Conference Abstracts

AMERICAN ELASMOBRANCH SOCIETY MEETINGS, TAMPA, FLORIDA, JULY 6-11, 2005

ARDIZZONE, DANIELE¹, GREGOR M. CAILLIET¹, LISA J. NATANSON², ALLEN H. ANDREWS¹, LISA A. KERR³, AND THOMAS A. BROWN⁴. ¹Moss Landing Marine Laboratories, California State University, 8272 Moss Landing Rd, Moss Landing, CA 95039; ²NOAA Fisheries Northeast Fisheries Science Center, Narragansett Laboratory, 28 Tarzwell Drive, Narragansett, RI 02882; ³University of Maryland Center of Environmental Science, Chesapeake Biological Laboratory, P.O. Box 38, 1 Williams Street, Solomons, MD 20688; ⁴ Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550.

APPLICATION OF BOMB RADIOCARBON CHRONOLOGIES TO SHORTFIN MAKO (ISURUS OXYRINCHUS) AGE VALIDATION

Age estimation is an issue for the shortfin mako (Isurus oxyrinchus) because of ongoing disagreement on the periodic deposition of vertebral growth bands. A band pair is defined as a set of opaque and translucent bands in vertebral centra. Using four age determination techniques, Pratt and Casey (1983) concluded two band pairs formed annually; however, Cailliet et al. (1983) assumed one band pair per year. To evaluate the validity of both interpretations, a new technique was applied using radiocarbon measured in shark vertebrae. In the 1950-1960s, thermonuclear testing released large amounts of radiocarbon into the atmosphere, which reacted to form ¹⁴CO₂ and entered the ocean through gas exchange over the following years. This influx created a time-specific marker in the marine environment that can be used in age validation. In the first application to elasmobranchs, Campana et al. (2002) validated the vertebral ageing methodology for the porbeagle (Lamna nasus) and assayed four samples from one shortfin mako vertebra, suggesting annual deposition of one band pair for both species. In the present study, band-counting age estimates from 54 shortfin mako vertebrae collected in 1950-1984 ranged in age 1-31 years. Bands in early stages of life appeared broad and clear and became less defined with age. Ageing error between readers was consistent, with 76% of the estimates ranging within two years of each other. Twenty-one radiocarbon values from vertebrae of eight shortfin makos (collected in the Western North Atlantic in 1963-1984) ranged between -160.2‰ and 86.8‰. The resulting concordance with the porbeagle indicated shortfin mako has longevity of at least 31 years and supports annual deposition of a single pair of growth bands.

This work was performed, in part, under the auspices of the U.S. Department of Energy by University of California, Lawrence Livermore National Laboratory under Contract W-7405-Eng-48

*BIZZARRO, JOSEPH J.¹, WADE D. SMITH¹, J. FERNANDO MÁRQUEZ-FARIAS², AND ROBERT E. HUETER³, ¹Pacific Shark Research Center, Moss Landing Marine Laboratories, 8272 Moss Landing Rd., Moss Landing, CA 95039, ²Instituto Nacional de la Pesca, Programa Tiburón, Centro Regional de Investigación Pesquera, Calle 20 Sur, 605, CP 85400 Guaymas, Sonora, México, ³Center for Shark Research, Mote Marine Laboratory, 1600 Ken Thompson Pkwy., Sarasota, FL 34236

REPRODUCTIVE BIOLOGY AND FISHERY ASPECTS OF THE GOLDEN COWNOSE RAY, RHINOPTERA STEINDACHNERI (EVERMANN AND JENKINS, 1891), FROM THE GULF OF CALIFORNIA AND PACIFIC COAST OF BAJA CALIFORNIA SUR, MEXICO

The golden cownose ray, Rhinoptera steindachneri (Evermann and Jenkins, 1891), is widespread in coastal waters of the tropical and subtropical eastern Pacific. It was among the most abundant species taken in artisanal elasmobranch fisheries of the Gulf of California and Bahía Almejas (Baja California Sur), Mexico, during 1998-2000. In the northern Gulf of California, R. steindachneri landings peaked during summer months and were negligible during winter. In Bahía Almejas, this species was frequently landed in August and uncommon in June, a trend also noted in CPUE (#individuals/vessel/trip; August=1.13, June=0.13). Size segregation and schooling behavior was evident from landings in both regions. Disc width (DW) of R. steindachneri harvested in the Gulf of California ranged from 39-98 cm and averaged 64.2 cm for males (n=585) and 64.4 cm for females (n=505). The largest male (96 cm DW) and female (104 cm DW) were recorded at Bahía Almejas. Size at first maturity and 50% median maturity were similar for males (64 cm, 69.9 cm DW) and females (65 cm, 70.0 cm DW). The largest immature male was 78 cm DW and the largest immature female was 72 cm DW. Fecundity was determined to be one offspring per female with larger females carrying larger embryos. Parturition was estimated to occur from late June to August at 39-45 cm DW after a gestation period of 10-12 months. Bahía Almejas served as a nursery ground for neonate R. steindachneri and a likely breeding location for adults. The conservative reproductive strategy of R. steindachneri, in which a single pup is produced annually after maturity is reached at a relatively large size, suggests that this species is of low productivity and highly susceptible to overexploitation.

KEYNOTE ADDRESS ABSTRACT
AMERICAN ELASMOBRANCH SOCIETY ANNUAL MEETING
"AGE AND GROWTH OF CHONDRICHTHYAN FISHES: NEW METHODS, TECHNIQUES, AND ANALYSIS SYMPOSIUM"

*CAILLIET, GREGOR M.¹, WADE D. SMITH, HENRY F. MOLLET, AND KENNETH J. GOLDMAN², ¹Moss Landing Marine Laboratories, 8272 Moss Landing Road, Moss Landing, California, 95039, U.S.A., ²Department of Biology, Jackson State University. 1400 J.R. Lynch Street, P.O. Box 18540, Jackson, MS, 39217 U.S.A.

CHONDRICHTHYAN GROWTH STUDIES: AN UPDATED REVIEW, STRESSING TERMINOLOGY, SAMPLE SIZE SUFFICIENCY, VALIDATION, AND CURVE FITTING

Validated age and growth estimates are important for constructing age-structured population dynamics models of fishes, including chondrichthyans, especially those that are exploited. We will review, correct, and supplement the results from the recent chondrichthyan ageing summary chapter, stressing the structures (both traditional and novel) utilized to estimate ages and synthesize the terminology used to describe their growth features. We will discuss validation approaches, concentrating on edge and marginal increment analyses. We will propose methods to assess size-specific sample sufficiency. We will review the mathematical approaches used to produce and interpret validated growth parameters, stressing the incorporation of size at birth (L₀). We will briefly summarize results from recent studies among taxonomic groups, stressing the patterns in growth and longevity parameters, how useful they are for age-structured models and resulting management policies for assessing the status of exploited chondrichthyan populations.

*CARLISLE, AARON B.¹, AARON KING², GREGOR M. CAILLIET¹, AND JAMES S. BRENNAN³, ¹Pacific Shark Research Center, Moss Landing Marine Laboratories, 8272 Moss Landing Road, Moss Landing, CA 95039, USA, ²BLM/DOI California Coastal National Monument, and NOAA/DOC National Marine Protected Areas Center, Science Institute, 99 Pacific St., Monterey, CA 93940, USA, ³Washingon Sea Grant Program, 3716 Brooklyn Avenue NE, Seattle, WA 98105, USA.

LONG-TERM TRENDS IN ELASMOBRANCH CATCH COMPOSITION FROM FISHING DERBIES IN ELKHORN SLOUGH, CALIFORNIA

Long term trends in the elasmobranch assemblage in Elkhorn Slough, Monterey Bay, California, were analyzed by documenting species composition and catch-per-unit-effort (CPUE) from 55 sport fishing derbies during May, June and July, from 1951 until 1995. The most abundant species, bat rays (Myliobatis californica), shovelnose guitarfish (Rhinobatos productus) and leopard sharks (Triakis semifasciata), were also analyzed for size-weight relationships, trends in size class distributions, stage of maturity, and sex ratios. Changes in species composition over the course of the derbies included the near complete disappearance of shovelnose guitarfish by the 1970s and a slight increase in the abundance of minor species (mainly smoothhounds, Mustelus spp., and thornbacks, Platyrhinoidis triseriata) starting in the mid-1960s. The proportion of bat rays in the catch steadily increased over the years while the abundance of leopard sharks has declined slightly during the last two decades. A peak in overall CPUE was evident during the mid to late fifties. Leopard shark and bat ray size class distribution data showed no obvious changes. The catch of bat rays and leopard sharks was consistently dominated by immature individuals, while the catch of shovelnose guitarfish was heavily dominated by adults. Female bat rays and shovelnose guitarfish were larger than their male counterparts, and outnumbered males nearly 2:1. Female and male leopard sharks were more nearly equal in size and sex ratio. Changes in species composition are likely due to shifts in the prevailing oceanographic conditions and habitat alteration in Elkhorn Slough. The sex ratios, stage of maturity, and size class distributions provide further evidence to the theory that Elkhorn Slough functions as a nursery ground for bat rays and leopard sharks.

*CARLISLE, AARON B.¹, RICHARD M. STARR², GREGOR M. CAILLIET¹, AND DAVID A. EBERT¹, ¹Pacific Shark Research Center, Moss Landing Marine Laboratories, 8272 Moss Landing Road, Moss Landing, CA 95039, USA, ²Moss Landing Marine Laboratories, University of California Sea Grant Extension Program, 8272 Moss Landing Road, Moss Landing, CA 95039, USA

SPATIAL AND TEMPORAL PATTERNS OF MOVEMENT AND HABITAT UTILIZATION OF FEMALE LEOPARD SHARKS IN ELKHORN SLOUGH, CALIFORNIA

The leopard shark (Triakis semifasciata) is one of the most abundant nearshore sharks in California and is commonly found in bays and estuaries. Elkhorn Slough is a shallow tidal embayment at the edge of Monterey Bay that is extensively utilized by leopard sharks of all ages and is believed to function as a nursery ground for the species. Due to the important role of the Slough in the life history of leopard sharks, understanding how sharks utilize this environment is important. Patterns of movement and habitat use of female leopard sharks in Elkhorn Slough were examined using acoustic tags and a combination of manual tracking and passive monitoring techniques between May 2003 and February 2005. Ten leopard sharks (91-132 cm TL) were tagged and manually tracked for 20-71.5 hours. An additional 13 leopard sharks (78-140 cm TL) were tagged and monitored for 4-443 days using an array of acoustic receivers. Analyses done to date indicate that the Elkhorn Slough National Estuarine Research Reserve marsh restoration site is important for leopard sharks in Elkhorn Slough. Tagged sharks spent extensive amounts of time in several specific areas during the pupping season, providing evidence of the value of the reserve as a nursery ground. Shark movements and habitat use appeared to be tidally influenced, because movements of tagged animals were restricted to channels and tidal creeks at lower tides. As the tide increased, they moved out of the channels onto intertidal mudflats where they appeared to utilize low intertidal mudflats. When in the main channel of Elkhorn Slough, shark movements showed more diel periodicity. Tagged animals moved up and down the Slough at relatively regular intervals, in which the sharks primarily occurred in the lower slough during night.

*EBERT, DAVID A., Pacific Shark Research Center, Moss Landing Marine Laboratories, 8272 Moss Landing Road, Moss Landing, CA 95039, USA

REPRODUCTION, DIET, AND HABITAT UTILIZATION OF LEOPARD SHARKS, TRIAKIS SEMIFASCIATA (GIRARD), IN HUMBOLDT BAY, CALIFORNIA, U.S.A.

The leopard shark, Triakis semifasciata (Girard), endemic to the eastern North Pacific, is one of the most common elasmobranch species found along the California coast. Several northern California bays and estuaries, including Humboldt Bay, are important nursery areas for this species. A total of 312 females were sampled in Humboldt Bay during the spring over three successive years. All females examined were determined to be mature and ranged in size from 120-154 cm L_T. Only three adult males were caught in the study area and all were tagged and released. Overall, of the 153 females examined in early spring 130 contained term-embryos. Each embryo was encapsulated in a clear membranous sac and all appeared to be near-term. The number of embryos per female ranged from 1-37 with the trend being that larger females had more embryos. A total of 1,446 embryos were sexed with a male:female ratio of 1:0.93 that was not significantly different than a 1:1 ratio (P > 0.05). Embryos ranged from approximately 17-20 cm L_T. Of the 159 individuals examined in late spring no females with embryos were found and all, with the exception of four individuals, were observed to be ovulating. A total of 239 stomachs were examined, of which 196 (82.0%) contained prey items. Overall, fish eggs (Atherinopsis californiensis), at 48.0%, had the highest %IRI, followed by the cancrid crabs, Cancer antennarius (29.8%) and C. magister (11.6%). All other prey items were of relatively minor importance, cumulatively representing 10.6% of the overall diet. Leopard sharks were observed foraging and this behavior is described.

*FLAMMANG, BROOKE E.¹ AND EMANUEL AZIZI ², ¹ Pacific Shark Research Center, Moss Landing Marine Laboratories, 8272 Moss Landing Road, Moss Landing, CA 95039, USA, ² University of Massachusetts, Amherst, MA, USA

THE RADIAL MUSCLE: A NEW CHAPTER IN SHARK TAILS

The swimming kinematics and hydrodynamics of heterocercal tails in elasmobranchs have been the focus of a number of recent studies. However, the locomotor functions of the internal morphological structures of the heterocercal tail remain unexplored. In this study we examine the morphology and function of the radial muscle or radialis during swimming in the spiny dogfish Squalus acanthias. The radialis consists entirely of red muscle fibers and is located ventral to the segmented axial myomeres in the most distal region of the caudal fin, originating on the ventral processes of the vertebral column and inserting along the horizontal septum. Individual muscle fibers are arranged dorsoposteriorly at angles ranging from 14 to 88 degrees relative to the vertebral column. The muscle fibers of the radialis share a similar fiber orientation and lie in close association with the deepest layer of the subdermal connective tissue sheets. Electrical stimulation of the radialis in anesthetized sharks results in visible movement of the ceratotrichia of the dorsal lobe of the caudal fin.. Using sonomicrometry, we found that muscle fibers shortened by <1% of their resting length during stimulated contractions. Finally, we combined bilateral electromyography of the radialis with simultaneous video to determine the point of activation of the radialis within the tailbeat cycle. Our results indicate that the radialis is active immediately after maximum lateral excursion of the caudal fin to the ipsilateral side. We also find that the activity patterns of the radialis on the right and left side of the body are approximately 180 degrees out of phase. Morphology and motor patterns of the radialis suggest that this muscle is acting as postural reinforcement, and controlling the orientation of the dorsal lobe of the caudal fin during steady swimming.

*ROBINSON, HEATHER, DAVID A. EBERT, AND GREGOR M. CAILLIET, Pacific Shark Research Center, Moss Landing Marine Laboratories, 8272 Moss Landing Road, Moss Landing, CA 95039, USA

FOOD HABITS OF THE LONGNOSE SKATE, RAJA RHINA (JORDAN AND GILBERT, 1880), IN CENTRAL CALIFORNIA WATERS

The longnose skate, Raja rhina, is one of the most important incidental species landed in central and northern California demersal fisheries. However, life history information is extremely limited for this species and aspects of its diet and feeding habits are unknown. Feeding ecology studies can provide researchers with important insights towards understanding potential fishery impacts on marine systems. The primary objective of this study was to analyze the feeding ecology of R. rhina off the coast of central California. Specimens of R. rhina were collected between September 2002 and August 2003 from fisheries-independent trawl surveys conducted by the National Marine Fisheries Service, Santa Cruz Lab (NMFS-SCL). Of 1,193 longnose skates caught, 527 were female and 666 were male. To date, 116 R. rhina stomach samples have been processed, and all prey items identified to lowest possible taxa. For every stomach, the percentage of each prey item by number (%N) and weight (%W) were calculated and averaged to obtain a mean value. These measures were combined with the overall percent frequency occurrence (%FO) to determine the Index of Relative Importance (IRI), represented as %IRI. Preliminary results indicate that the five most important prey items are Neocrangon resima (31.7% IRI), Octopus rubescens (11.6% IRI), unidentified euphausiids (11.4% IRI), unidentified teleosts (10.7% IRI), and unidentified shrimp (9.6% IRI). Raja rhina diet will be further analyzed through comparison of the following intraspecific variables: gender (male/female), depth (shelf/slope), and size class (<600 mm/>600 mm).

*SMITH, WADE D., COLLEENA R. PEREZ, AND DAVID A. EBERT, Pacific Shark Research Center, Moss Landing Marine Laboratories, 8272 Moss Landing Road, Moss Landing, CA 95039, USA

GROWTH OF THE CALIFORNIA SKATE, RAJA INORNATA: ASSESSMENT OF MULTIPLE AGEING STRUCTURES AND SOMATIC GROWTH MODELS

Elasmobranch size-at-age estimates are predominantly derived from vertebral band counts and modeled using a three parameter von Bertalanffy growth function. However, alternative ageing structures and growth models may provide improved descriptions of species' growth. The objectives of this study were to examine the applicability of non-traditional calcified structures as reliable size-at-age estimators and to describe the somatic growth characteristics of Raja inornata, a nearshore skate species for which no previous life history information has been published. Relationships between ageing structure and specimen sizes were used to assess the assumption that the structures increase proportionally to specimen size. Precision among caudal thorn, neural arch, and vertebral centrum age estimates were evaluated using tests of symmetry and analysis of variance to determine the most suitable structure. The temporal periodicity of band deposition was examined using modified centrum edge and marginal increment ratio analyses as semi-direct methods of validation. Disc width-, total length-, and weight-at-age estimates were fitted to polynomial, two parameter von Bertalanffy, three parameter von Bertalanffy, Gompertz, and Schnute growth functions. Models were developed from female and male size-at-age data separately and combined and analyzed by analysis of residual sums of squares to determine if calculated parameters are equivalent between the sexes. The most appropriate growth model was selected based on parsimony and goodness-of-fit using Akaike's information criterion and standard errors of model estimates.

*TREJO, TONATIUH, GREGOR M. CAILLIET, DAVID A. EBERT, Pacific Shark Research Center, Moss Landing Marine Laboratories, 8272 Moss Landing Road, Moss Landing, CA 95039, USA

POPULATION STRUCTURE OF THRESHER SHARKS (ALOPIAS SPP.) BASED UPON MITOCHONDRIAL DNA CONTROL REGION SEQUENCE DATA

The family Alopiidae is comprised of three species: the pelagic (Alopias pelagicus), bigeye (A. superciliosus), and common (A. vulpinus) thresher sharks. Alopias pelagicus is found only in the Pacific and Indian oceans, while the other two species are distributed worldwide. Despite growing conservation concerns, genetic relatedness among thresher shark populations is poorly known. We examined the population genetic structure of each species using DNA sequences from the mitochondrial control region. Samples of A. pelagicus, A. superciliosus, and A. vulpinus were collected from the East (n = 0, 15, 14) and West (n = 0, 6, 39) coasts of the United States, Gulf of California (n = 23, 1, 0), Clipperton Atoll (n = 3, 0, 0), Ecuador (n = 22, 14, 0), Hawaii (n = 0, 13, 0), Taiwan (n = 5, 11, 5), Indonesia (n = 25, 0, 0), New Caledonia (n = 1, 0, 0), New Zealand (n = 0, 0, 5), South Africa (n = 0, 1, 5), and France (n = 0, 1, 5). Despite their high dispersal potential, our data indicate limited gene flow among thresher shark populations, but geographic patterns of genetic variation differ among species. Gene flow in A. pelagicus is limited across the Pacific Ocean, but is extensive among locations in both the eastern and western Pacific. In A. superciliosus, genetic heterogeneity was detected among Pacific and Atlantic populations, but not among populations spanning the entire Pacific Ocean. Results for A. vulpinus indicate genetic heterogeneity among all sampled populations, both within and between the Atlantic and Pacific oceans. Taken together, our data indicate that intra-specific biological and ecological differences among thresher sharks are sufficient to cause variable patterns of inter-specific genetic population structure. This study also highlights the need for international cooperation in management of thresher shark populations.

7TH INDO-PACIFIC FISH CONFERENCE, TAIPEI, TAIWAN, MAY 15-20, 2005

*CAILLIET, GREGOR M.¹ AND KENNETH J. GOLDMAN², ¹Moss Landing Marine Laboratories, 8272 Moss Landing Road, Moss Landing, California, 95039, U.S.A., ² Department of Biology, Jackson State University. 1400 J.R. Lynch Street, P.O. Box 18540, Jackson, MS, 39217 U.S.A.

REVIEW OF AGE DETERMINATION AND VALIDATION STUDIES IN CHONDRICHTHYAN FISHES

Validated age estimates are important for producing age-structured models to better understand population dynamics of exploited fishes. From our recent book chapter, we will review the structures utilized to estimate ages of chondrichthyan fishes, including the recent introduction of novel structures such as neural arches and caudal thorns, and the methods and analytical approaches used to produce reasonable growth characteristics for them. We will also review approaches that verify (assess precision of) age estimates (i.e. MRI and MIR) and those that validate (ascertain the temporal periodicity of) these age estimates and growth parameters. We will discuss results from two of the best methods used to validate age, growth, and longevity estimates: tag-recapture analysis and the time-specific, bomb-produced radiocarbon marker. We will summarize results among taxonomic groups from our studies, and those of others, and evaluate their verification and validation. Finally, we will briefly review the resulting growth and longevity parameters, and how they can be used to produce reasonable mortality estimates, demographic parameters, and age-structured management policies for assessing the population dynamics and recovery probabilities of exploited chondrichthyan populations.

*EBERT, DAVID A., Pacific Shark Research Center, Moss Landing Marine Laboratories, 8272 Moss Landing Road, Moss Landing, CA 95039, USA

REPRODUCTION, DIET, AND HABITAT UTILIZATION OF LEOPARD SHARKS, TRIAKIS SEMIFASCIATA (GIRARD), IN HUMBOLDT BAY, CALIFORNIA, U.S.A.

The leopard shark, Triakis semifasciata (Girard), endemic to the eastern North Pacific, is one of the most common elasmobranch species found along the California coast. Several northern California bays and estuaries, including Humboldt Bay, are important nursery areas for this species. A total of 312 females were sampled in Humboldt Bay during the spring over three successive years. All females examined were determined to be mature and ranged in size from 120-154 cm L_T. Only three adult males were caught in the study area and all were tagged and released. Overall, of the 153 females examined in early spring 130 contained term-embryos. Each embryo was encapsulated in a clear membranous sac and all appeared to be near-term. The number of embryos per female ranged from 1-37 with the trend being that larger females had more embryos. A total of 1,446 embryos were sexed with a male:female ratio of 1:0.93 that was not significantly different than a 1:1 ratio (P > 0.05). Embryos ranged from approximately 17-20 cm L_T. Of the 159 individuals examined in late spring no females with embryos were found and all, with the exception of four individuals, were observed to be ovulating. A total of 239 stomachs were examined, of which 196 (82.0%) contained prey items. Overall, fish eggs (Atherinopsis californiensis), at 48.0%, had the highest %IRI, followed by the cancrid crabs, Cancer antennarius (29.8%) and C. magister (11.6%). All other prey items were of relatively minor importance, cumulatively representing 10.6% of the overall diet. Leopard sharks were observed foraging and this behavior is described.

*FLAMMANG, BROOKE E., DAVID A. EBERT, AND GREGOR M. CAILLIET, Pacific Shark Research Center, Moss Landing Marine Laboratories, 8272 Moss Landing Road, Moss Landing, CA 95039, USA

DISTRIBUTION AND REPRODUCTIVE BIOLOGY OF DEEP-SEA SCYLIORHINIDS OF THE EASTERN NORTH PACIFIC

Apristurus brunneus, A. kampae and Parmaturus xaniurus were collected from trawl and longline fishery independent survey cruises from June 2001 through October 2004 from northern Washington to San Diego, California. Longline sets were mainly comprised of P. xaniurus, with occasional catch of gravid female A. brunneus. Conversely, trawl cruises were primarily comprised of Apristurus species. Apristurus brunneus were typically found between 300 - 942 m, while A. kampae occurred = 1,000 m deep. Parmaturus xaniurus was caught between 300 and 550 m depth. Egg cases of A. brunneus and P. xaniurus were located in specific nursery sites in areas of high vertical relief at 300-400 m depth. The total lengths at first, 50% and 100 % reproductive maturity were determined for males and females of all three species. At higher latitudes, A. brunneus and P. xaniurus reached sexual maturity at larger sizes. It was determined that both A. brunneus and P. xaniurus reproduce year-round, based on the occurrence of gravid females and gonadosomatic (GSI) and hepatosomatic indices (HSI) for both sexes. Gravid A. kampae females were found from July through December.

SMITH, WADE D. AND GREGOR M. CAILLIET, Pacific Shark Research Center, Moss Landing Marine Laboratories, 8272 Moss Landing Road, Moss Landing, CA 95039, USA

GROWTH AND MATURITY CHARACTERISTICS OF A COMMERCIALLY EXPLOITED STINGRAY, DASYATIS DIPERURA

The diamond stingray, Dasyatis dipterura (Jordan and Gilbert 1880; often inappropriately referred to as D. brevis), inhabits shallow coastal waters from southern California to Chile, including the Galápagos and Hawaiian Islands. In western México, D. dipterura is a common component of artisanal elasmobranch fisheries. Maturity estimates based on gross macroscopic assessment of reproductive tracts were completed for 126 females and 55 males. Median disc width (DW) at maturity was determined to be 57.3 cm for females and 46.5 cm for males, respectively. Growth characteristics were estimated by a detailed examination of banding patterns present in thin-sectioned vertebral centra. Age estimates were obtained from 304 fishery-derived specimens (169 female, 135 male). Based on four independent reads, 73.5% of all band counts agreed within at least ± 1 and the overall average percent error was 9.8%. An annual nature of band deposition was confirmed through centrum edge and marginal increment analyses. Gompertz, polynomial, and von Bertalanffy growth models were fit to the age-at-DW/weight data. Growth characteristics differed significantly between females and males. Resultant models were evaluated and ranked using Akaike's Information Criterion. The maximum estimated age was 28 years for females and 16.5 years for males. Traditional three parameter von Bertalanffy growth models produced relatively low instantaneous growth rates: females (DW8 = 92.4 cm, k = 0.055, to = -7.61); males (DW8 = 62.2 cm, k = 0.10, to = -6.80). These values are the lowest reported for myliobatiform stingrays and indicate low growth rates by comparison to elasmobranchs in general.

The Third International Symposium on Fish Otolith Research & Application, Townsville, Australia, 11-16 July 2004

* CAILLIET, G. M., ANDREWS, A. H., AND KERR FERREY, L. A., MOSS LANDING MARINE LABORATORIES, 8272 MOSS LANDING RD., MOSS LANDING, CA 95039, USA

KEYNOTE ADDRESS THEME 3: AGE AND GROWTH : AGE DETERMINATION AND VALIDATION: STRUCTURES, METHODS, ANALYSES AND APPLICATION

Validated age estimates are important for age-structured models to produce effective fishery management policies for exploited organisms, including invertebrates and fishes. We review the structures utilized to estimate ages of these organisms, including recent novel structures such as neural arches and caudal thorns in elasmobranch fishes. We then review the methods and analytical approaches used to assign ages to these structures. Of special significance for correct interpretation of growth, especially for deep-dwelling, long-lived organisms, are approaches that verify (assess precision of) age estimates (i.e. MRI and MIR) and those that validate (ascertain the temporal periodicity of) these age estimates and growth parameters. We will focus specifically on three methods used to validate age, growth, and longevity estimates: tag-recapture analysis, the disequilibria of lead-210 and radium-226, and the time-specific, bomb-produced radiocarbon marker. We will summarize results from our studies on deep-water organisms (elasmobranchs, bony fishes and corals), and those of others, and evaluate the veracity of these validation techniques. Finally, we will discuss the uses of the resulting growth and longevity parameters for producing reasonable mortality coefficients, demographic parameters, and age-structured management policies for assessing the population dynamics and recovery probabilities of exploited populations.

* Lisa A. Kerr Ferrey¹ Thomas A. Brown², Allen H. Andrews¹, Gregor M. Cailliet¹, ¹Pacific Shark Research Center, Moss Landing Marine Laboratories, 8272 Moss Landing Road, Moss Landing, CA, U.S.A., ²Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratories, 7000 East Avenue, Livermore, CA, U.S.A.

Radiocarbon Age Validation of the White Shark (Carcharodon carcharias) from the eastern Pacific

A preliminary study of the age and growth of the white shark (Carcharodon carcharias) from the eastern Pacific revealed a relatively long life span and slow growth rate; however, no age validation has been performed for this species to date. In order to obtain reliable growth rates, age structure, and longevity estimates, it is essential to validate the age estimation procedures for the white shark. Without this information, accurate life history assessment, stock assessment and management for these species is not possible. By counting growth zones in the vertebrae we are able to estimate the age of the shark, however, not all sharks deposit annual growth zones nor are growth bands easily discernable in all species. Therefore, it is necessary to validate the periodicity of growth in vertebrae by an independent method. Radiocarbon age validation uses the discrete radiocarbon signal produced from thermonuclear testing in the 1950s and 1960s and retained in skeletal structures as a time-specific marker. The goal of this study was to validate the age and age estimation methodology of the white shark by measuring bomb radiocarbon in vertebrae with estimated ages that span the pre- to post-bomb era, and compare this to an established chronometer for bomb radiocarbon. Radiocarbon measured in growth zones of vertebrae were plotted against estimated birth year to produce a radiocarbon time series for southern California waters from 1955 to 1975. The agreement between the white shark record and published radiocarbon chronometers successfully validated the annual formation of growth increments.

AES / ASIH, Norman, Oklahoma
May 26-31 2004

* BIZZARRO, JOSEPH J. AND CAILLIET, GREGOR M., PACIFIC SHARK RESEARCH CENTER, MOSS LANDING MARINE LABORATORIES, 8272 MOSS LANDING RD., MOSS LANDING, CA 95039, USA

DIET, FEEDING ECOLOGY, AND ECOMORPHOLOGY OF THE DOMINANT RAY SPECIES IN BAHÍA ALMEJAS (BAJA CALIFORNIA SUR, MEXICO)

Despite the importance of trophic relationships in understanding community structure and stability, little is known about the feeding ecology of most elasmobranch species. This is especially true of rays, which typically occupy high trophic levels in low-latitude marine coastal ecosystems. In Bahía Almejas, specimens were collected between 1998 and 2002 from an artisanal gillnet fishery targeting rays during summer months. Diet and ecomorphology of the feeding apparatus were examined for the most abundant species, including: the shovelnose guitarfish (Rhinobatos productus), diamond stingray (Dasyatis dipterura), Cortez electric ray (Narcine entemedor), California butterfly ray (Gymnura marmorata), and Pacific cow-nose ray (Rhinoptera steindachneri). Sample size sufficiency was examined using cumulative prey curves and a priori power analyses. Compound indices (%IRI, GII) were used to characterize diet. Ontogenetic, intergender, and temporal differences in diet were analyzed using parametric or multivariate statistics, whenever possible. Interspecific comparisons of dietary overlap, using both general (e.g., crabs, teleosts, polychaetes) and species-specific prey categories, were compared using Spearman Rank correlation. Trophic level was calculated using a technique modified from Cortés (1999). An Index of Foraging Habitat was created based on known habitat associations of prey items. Morphological and meristic aspects of the feeding apparati of each species were compared intraspecifically with principal component analysis and interspecifically with discriminant function analysis. Canonical correlation analysis was used to investigate associations between morphological variables and diet composition. Results of these analyses will be presented and the trophic roles of these species in Bahía Almejas assessed. The diets and morphologies of these species did not exhibit a high degree of similarity, potential facilitating their coexistence in this region.

*BIZZARRO, JOSEPH J. ¹, SMITH, WADE D. ¹, MÁRQUEZ-FARÍAS, J. FERNANDO ², AND HUETER, ROBERT E. ³, ¹PACIFIC SHARK RESEARCH CENTER, MOSS LANDING MARINE LABORATORIES, MOSS LANDING, CA, ²INSTITUTO NACIONAL DE LA PESCA, GUAYMAS, SONORA, MÉXICO, ³CENTER FOR SHARK RESEARCH, MOTE MARINE LABORATORY, SARASOTA, FL

OBSERVATIONS ON THE REPRODUCTIVE BIOLOGY AND FISHERY FOR RHINOPTERA STEINDACHNERI IN THE GULF OF CALIFORNIA AND BAHÍA ALMEJAS, MEXICO

The Pacific cow-nose ray, Rhinoptera steindachneri, is a common nearshore stingray ranging from the Pacific coast of Baja California Sur to the Galapagos Islands, yet little is known about its basic biology. From 1998-2000, surveys of artisanal fishing camps throughout the Gulf of California (GOC) and in Bahía Almejas identified and characterized elasmobranch fisheries and sampled landings. Fishery-derived R. steindachneri were enumerated, sexed, measured, weighed, and examined for reproductive condition. This species was the sixth most abundant of 44 elasmobranch species observed in northern GOC, comprising 6.92% (n=11,142) of overall landings and 11.45% (n=4,079) of summer landings. In the Bahía Almejas summer batoid fishery, it was the fifth most abundant of twenty-one elasmobranch species (2.13%, n=113). Rhinoptera steindachneri is typically landed with bottomset gillnets in mixed species fisheries for batoids, small coastal sharks, and demersal teleosts. The mean size of females captured in the GOC was 64.4 + 11.8 cm disc width (DW) (mean and SD, n=505) whereas males averaged 64.2 + 14.0 cm DW (n=586). Landed specimens measured from 39 to 98 cm DW, with only females occupying the largest size classes (>89 cm DW). Maximum size records for both males (96 cm DW) and females (104 cm DW) were noted among Bahía Almejas landings. Median DW at 50% maturity was similar between sexes (males=69.9 cm, females=70.0 cm). Fecundity was only one embryo per female in all gravid specimens examined (n=149). The largest embryo was 43 cm, slightly smaller than the largest free-living specimen (39 cm DW). Gravid females were recorded during all seasons, with most observed in spring (59.7%, n=89) and fewest in summer (2.7%, n=4). The mean DW of GOC embryos increased from April (x=26.3 cm, n=16) to May (x=30.4 cm, n=63), to June (x=38.8, n=2). In all months, larger females carried larger embryos.

* EBERT, DAVID A., PACIFIC SHARK RESEARCH CENTER, MOSS LANDING MARINE LABORATORIES, 8272 MOSS LANDING ROAD, MOSS LANDING, CA. 95039, USA

FROM THE BERING SEA TO SOUTHERN AFRICA: AN OVERVIEW OF SKATE (CHONDRICHTHYES: RAJIFORMES) REPRODUCTIVE BIOLOGY

Skates are an important component of the demersal fish community in many temperate and deepsea ecosystems. Similar to other chondrichthyans, most skates have life history characteristics that make them vulnerable to over-exploitation. Recently, skates have become a concern to fishery agencies due to the preponderance of these elasmobranchs caught as bycatch in groundfish fisheries and as a directed fishery. Although they may comprise a significant component of the overall catch, general biological information on skates is scare. Current studies by researchers at the Pacific Shark Research Center (PSRC) reveal that skates exhibit variable and complex life history parameters. Presently, a long-term, broad-based study is underway to elucidate aspects on the life history, ecology, and systematics of skates in three different ecosystems. These aspects include age and growth, demography, distribution, feeding ecology, habitat utilization, systematics, and reproductive biology. Data will be presented from the age, growth, and reproductive biology portions of this study that includes a total of 43 species representing 12 genera and three families. Among the findings to be presented, it is important that skate studies, (1) determine the correct identity of the species involved, (2) identify to species those taken as bycatch and/or in directed fisheries, (3) standardized the methods of determining maturity, (4) critically review age and growth studies, and (5) determine and identify discrete populations through genetics and quantitative life history studies. Finally, it is concluded that skate life history parameters need to be studied on a localized basis and not on a global basis. This is especially true for management purposes.

EBERT, DAVID A., CARLISLE, AARON, AND *CAILLIET, GREGOR M., MOSS LANDING MARINE LABORATORIES/PACIFIC SHARK RESEARCH CENTER, 8272 MOSS LANDING ROAD, MOSS LANDING, CA 95039, USA

A LIFE HISTORY DATA MATRIX FOR CHONDRICHTHYAN FISHES OF THE EASTERN NORTH PACIFIC OCEAN

One the primary objectives of the newly-formed Pacific Shark Research Center (PSRC) at Moss Landing Marine Laboratories (MLML) was the creation of a comprehensive life history data matrix covering the entire body of literature on all chondrichthyans (sharks, rays, and chimaeras) of the eastern North Pacific, from the eastern Bering Sea to the southern tip of Baja California. We, along with 11 additional contributors at PSRC/MLML, have completed this literature review and produced a data matrix designed after a previous version, completed in 2001, on the life histories of 124 common nearshore fish species of California for the California Department of Fish and Game (dfg.ca.gov), under Pacific States Marine Fisheries Commission support. The new chondricththyan data matrix covers 21 families and 63 species of sharks, 11 families and 42 species of rays, and 2 families and 4 species of chimaeras. It includes information on taxonomy, geographic range, age and growth, longevity, reproduction, demography, trophic interactions, habitat utilization, genetics, recruitment, mortality, and behavior of these 109 species. PSRC scientists and graduate students are now working on research projects to fill data gaps uncovered by this extensive literature search. We will discuss the format of the data matrix and present the life history information on selected, exemplary chondrichthyan species. It will soon be available on the MLML and PSRC/NSRC web pages (www.mlml.calstate.edu and www.flmnh.ufl.edu/fish/Sharks/nsrc/NSRC.htm) and we invite constructive suggestions on it.

* FLAMMANG, BROOKE E., EBERT, DAVID A., AND CAILLIET, GREGOR M., PACIFIC SHARK RESEARCH CENTER, MOSS LANDING MARINE LABORATORIES, 8272 MOSS LANDING RD., MOSS LANDING, CA. 95039-9647, USA

DISTRIBUTION AND REPRODUCTIVE BIOLOGY OF DEEP-SEA SCYLIORHINIDS OFF CENTRAL CALIFORNIA

These findings are part of a broad-based ecological investigation into the life history of three deep-sea catsharks (Scyliorhinidae), Apristurus brunneus, A. kampae and Parmaturus xaniurus, in the eastern North Pacific. Preliminary results on the distribution and reproductive biology of these species off central California will be presented. Specimens were collected from trawl and longline survey cruises by the National Marine Fisheries Service (NMFS) from June 2002 through December 2003 from Año Nuevo to Point Sur, California. Distribution and occurrence of the three species were analyzed to identify trends associated with season, depth, maturity, and sex. Longline hauls were mainly comprised of P. xaniurus, with an occasional catch of gravid female A. brunneus. Conversely, trawl cruises were primarily comprised of Apristurus spp. Apristurus brunneus were typically found between 300-942 m, while A. kampae occurred deeper than 1,005 m. The total lengths at 50% reproductive maturity were determined for males and females of all three species. It was determined that both A. brunneus and P. xaniurus reproduce year-round based on the occurrence of gravid females and gonadosomatic (GSI) and hepatosomatic indices (HSI) for both males and females. Gravid A. kampae females were found from July through December.

PEREZ, COLLEENA, CAILLIET, GREGOR M., AND EBERT, DAVID A., MOSS LANDING MARINE LABORATORIES/PACIFIC SHARK RESEARCH CENTER, 8272 MOSS LANDING ROAD, MOSS LANDING, CA 95039, USA

AGE, GROWTH, AND REPRODUCTION OF THE SANDPAPER SKATE, BATHYRAJA KINCAIDII, OFF CENTRAL CALIFORNIA

The sandpaper skate, Bathyraja kincaidii is commonly taken as bycatch in trawl fisheries off central California although there is no life history information known for this species. To assess age, growth and maturity, 393 Bathyraja kincaidii have been collected from commercial samplers, monthly trawl surveys and slope surveys conducted by the National Marine Fisheries Service since January 2002. Sexes were equally represented, with females comprising 50.1% and males 49.9%. Females ranged from 199-610 and males from 195-635 mm total length (TL). For age and growth analysis, sectioned vertebrae were read 3 times and APE (0.08), CV (0.13) and D (0.07) precision values calculated. Ages were assigned based on agreement of at least two independent estimates, with an additional read if necessary. Marginal increment analysis was unsuccessful, therefore centrum edge analysis is being investigated. Age estimates indicate a minimum longevity of 17 years for female and 18 years for male B. kincaidii. Females grow faster (L =533.9 mm; k=0.245; n=100) but males reach a larger size (L =580.387mm; k=0.187; n=90). Analysis of residual sum of squares indicated no difference (p = 0.089) between male and female von Bertalanffy growth curves, and combined sexes produced values of L =554.2mm and k=0.213. Females first mature at 450 mm (4 years), while males first mature 440 mm TL, 1 year earlier. However, 50% maturity was similar between sexes: 467 mm and 7.0 years for females and 492 mm and 7.5 years for males.

* SMITH, WADE D., PACIFIC SHARK RESEARCH CENTER, MOSS LANDING MARINE LABORATORIES, 8272 MOSS LANDING ROAD, MOSS LANDING, CA, 95039, USA

POPULATION DYNAMICS OF A COMMERCIALLY EXPLOITED STINGRAY, DASYATIS DIPTERURA

Rays are commonly taken in western Mexico's artisanal elasmobranch and industrial trawl fisheries. Dasyatis dipterura, the diamond stingray, is one of the most commonly landed species in their directed elasmobranch fisheries. Demographic analyses of D. dipterura from the Magdalena Bay lagoon complex, B.C.S., Mexico, were performed to estimate population growth characteristics and potential responses to fishing pressure. Age-structured life history tables and Leslie matrices were calculated using empirical fecundity, longevity, and maturity values. Monte Carlo simulation was incorporated to introduce demographic variability and uncertainty in age at maturity, fecundity, survivorship, and longevity. Ten models were developed from static (4) and Monte Carlo (6) approaches based on maximum observed age (28), theoretical maximum age (63), and variable longevity (25-39) under unexploited and exploited (F=0.05) conditions. Elasticity analyses determined the relative contribution and impact of changes in fertility, juvenile, and adult survival to population growth rates (?). Annual survivorship probabilities ranged between 0.71-0.94. Projections generated by incorporating Monte Carlo simulations produced mean ? of 1.05-1.06 (5-6% increase) per year, net reproductive rates per generation (Ro) of 2.4-3.0, and generation times (A) from 14.4-15.2 years. Mean values of ? obtained applying variable vital rates were similar to those recently calculated for several large, coastal carcharhinids. Introducing relatively low fishing mortality into population models produced a maximum ? value under an optimal, static scenario of 1.09 and a minimum value of 1.01 annually under varied models. These D. dipterura populations thus have relatively low productivity and low resilience to fishing pressure. Elasticity analysis indicated that population growth rates of D. dipterura are more strongly influenced by survival of the juvenile and adult stages than survival of neonates or changes in fecundity. This elasticity pattern is similar that those observed among species of sharks and other long-lived marine vertebrates.

*TREJO, TONATIUH; CAILLIET, GREGOR M.; EBERT, DAVID A. PACIFIC SHARK RESEARCH CENTER, MOSS LANDING MARINE LABORATORIES, 8272 MOSS LANDING ROAD, MOSS LANDING, CA, 95039, USA

PHYLOGEOGRAPHY OF THRESHER SHARKS, ALOPIAS SPP., BASED UPON MITOCHONDRIAL DNA CONTROL REGION SEQUENCES: PRELIMINARY RESULTS

The global population structure of thresher sharks (Alopias pelagicus, A. superciliosus, and A. vulpinus) is virtually unknown. Thresher sharks are taken worldwide both by directed commercial fisheries and as bycatch in tuna and billfish fisheries. Recent analysis of logbook data for the U.S. pelagic longline fleets targeting swordfish and tunas in the Northwest Atlantic indicates that catches of thresher sharks have declined by 80% since 1986, a trend that may reflect their global status. Effective conservation and management strategies for pelagic sharks require a fundamental understanding of their life histories, including population structure. If thresher shark populations are genetically distinct, management guidelines aimed at large geographic areas could be inappropriate, perhaps leading to the permanent loss of regional populations and decreasing their genetic diversity and evolutionary potential. Tissue samples of A. pelagicus, A. superciliosus, and A. vulpinus have been collected from the Northeast Pacific (N = 13,0,32), Central Pacific (N = 0,16,0), Northwest Pacific (N = 3,3,0), Southeast Pacific (N = 21,19,0), Southwest Pacific (N = 0,0,5), Northwest Atlantic (N = 0,15,15), Northeast Atlantic (N = 0,0,6), and Indian (N = 0,1,0) Oceans. We are using mitochondrial DNA control region sequences to quantify the degree of genetic relatedness among geographically disjunct populations of thresher sharks. In addition, DNA sequences from the cytochrome b gene are being used to confirm species identifications of the samples collected. Results will be presented in the context of thresher shark conservation and management.

*WINTNER, S. P.¹, NATANSON, L. J.², JOHANSSON, F.³, PIERCY, A.⁴, CAMPBELL, P.⁵, DE MADDALENA, A.⁶, GULAK, S.⁷, HUMAN, B.⁸, CIGALA FULGOSI, F.⁹, EBERT, D.¹⁰, FONG, J. ¹¹, HEMIDA, F.¹², MOLLEN, F. H. ¹³, VANNI, S.¹⁴, BURGESS, G. H.¹⁴, COMPAGNO, L. J V.¹⁵, WEDDERBURN-MAXWELL, A.¹⁶, ¹NATAL SHARKS BOARD, PRIVATE BAG 2, 4320 UMHLANGA ROCKS, SOUTH AFRICA, ²NARRAGANSETT LABORATORY, NORTHEAST FISHERIES SCIENCE CENTER, NATIONAL MARINE FISHERIES SERVICE, NOAA, NARRAGANSETT, RI, USA, ³VERTEBRATE SECTION, GÖTEBORG NATURAL HISTORY MUSEUM, GÖTEBORG, SWEDEN, ⁴FLORIDA PROGRAM FOR SHARK RESEARCH, FLORIDA MUSEUM OF NATURAL HISTORY, UNIVERSITY OF FLORIDA, GAINESVILLE, FL, USA, ⁵DEPARTMENT OF ZOOLOGY, THE NATURAL HISTORY MUSEUM, LONDON, UK, ⁶BANCA DATI ITALIANA SQUALO BIANCO, MILANO, ITALY, ⁷PELAGIC OBSERVER PROGRAM, SOUTH EAST FISHERIES SCIENCE CENTRE, NATIONAL MARINE FISHERIES SERVICE, NOAA, MIAMI, USA, ⁸27 SOUTHERN AVE, WEST BEACH SA 5024, AUSTRALIA, ⁹DIPARTIMENTO SCIENZE DELLA TERRA, UNIVERSITÀ DI PARMA, PARMA, ITALY, ¹⁰PACIFIC SHARK RESEARCH CENTER, MOSS LANDING MARINE LABORATORIES, MOSS LANDING, CA, USA, ¹¹DEPARTMENT OF ICHTHYOLOGY, CALIFORNIA ACADEMY OF SCIENCES, SAN FRANCISCO, CA, USA, ¹²LABORATOIRE ECOLOGIE ET ENVIRONNEMENT (PROJET HALIEUTIQUE), UNIVERSITÉ DES SCIENCES ET TECHNIQUES HOUARI BOUMEDIENNE (USTHB), ALGIERS, ALGERIA, ¹³MEISTRAAT 16, B - 2590 BERLAAR, BELGIUM, ¹⁴ MUSEO DI STORIA NATURALE DELL'UNIVERSITÀ, SEZIONE DI ZOOLOGIA "LA SPECOLA", FIRENZE, ITALY, ¹⁵ SHARK RESEARCH CENTER, SOUTH AFRICAN MUSEUM, CAPE TOWN, SOUTH AFRICA, ¹⁶UMHLANGA RADIOLOGY, UMHLANGA HOSPITAL, UMHLANGA ROCKS, SOUTH AFRICA

SOUTH AFRICA PRELIMINARY INVESTIGATION OF VERTEBRAL GROWTH RINGS IN THE BASKING SHARK CETORHINUS MAXIMUS (GUNNERUS)

Vertebral samples of 10 females (260.6-686 cm total length (TL)), 15 males (311-840 cm TL) and 9 unknown sex (375.9-853.4 cm TL) C. maximus were sourced through museums and institutional and private collections. A total of 101 vertebrae, including 58 vertebrae from a 260.6 cm TL animal, were used. In addition, different size vertebrae from a further eight animals were available. X-radiography was used to enhance the visibility of vertebral growth rings and a total of 153 x-radiographs were produced. Of those, 94 were scanned and growth ring counts were done both "manually" and using Digital Image Analysis. There was a linear relationship between vertebral diameter and TL and Von Bertalanffy parameters based on observed and back-calculated values will be presented.

Western Groundfish, Victoria, British Columbia, Canada
9-13 February 2004

The reproductive biology and habitat utilization of skates collected along the eastern Bering Sea continental slope was studied (EBSCS). Data were collected during a National Marine Fisheries Service (NMFS) exploratory research cruise along the EBSCS during June-July 2002. A total of 1,330 specimens comprised of nine species were examined for reproductive information. The survey area extended the length of the EBSCS from northwest of Unalaska Island (55° 95'N, 168° 51 92'W) to the southern Navrin Canyon (60° 16'N, 179° 68'W) in waters ranging from 209 to 1,556 m deep. The survey area was divided into two strata types, one by area and another by depth. The EBSCS can be characterized by three distinct habitats; a broad, gentle, sloping area referred to as shelf habitat, areas bisected by submarine canyons referred to as canyon habitat, and areas of steep profile referred to as slope habitat. Skates are an important component of the demersal fish community along the EBSCS and are commonly caught in groundfish fisheries. Despite the abundance and diversity of skates in this region very little is known about their basic life history and ecology. The results presented are part of an ongoing, broad-based, study of the demersal chondrichthyan fauna in the eastern North Pacific and Bering Sea.

One the primary objectives of the newly-formed Pacific Shark Research Center (PSRC) at Moss Landing Marine Laboratories (MLML) was the creation of a comprehensive life history data matrix covering the entire body of literature on all chondrichthyans (sharks, rays, and chimaeras) of the eastern North Pacific, from the eastern Bering Sea to the southern tip of Baja California. We, along with 11 additional contributors at PSRC/MLML, have completed this literature review and produced a data matrix designed after a previous version, completed in 2001, on the life histories of 124 common nearshore fish species of California for the California Department of Fish and Game (dfg.ca.gov), under Pacific States Marine Fisheries Commission support. The new chondricththyan data matrix covers 21 families and 63 species of sharks, 11 families and 42 species of rays, and 2 families and 4 species of chimaeras. It includes information on taxonomy, geographic range, age and growth, longevity, reproduction, demography, trophic interactions, habitat utilization, genetics, recruitment, mortality, and behavior of these 109 species. PSRC scientists and graduate students are now working on research projects to fill data gaps uncovered by this extensive literature search. We will discuss the format of the data matrix and present the life history information on selected, exemplary chondrichthyan species. It will soon be available on the MLML and PSRC/NSRC web pages (www.mlml.calstate.edu and www.flmnh.ufl.edu/fish/Sharks/nsrc/NSRC.htm) and we invite constructive suggestions on it.

The sandpaper skate, Bathyraja kincaidii is commonly taken as bycatch in trawl fisheries off central California although there is no life history information known for this species. To assess age, growth and maturity, 393 Bathyraja kincaidii have been collected from commercial samplers, monthly trawl surveys and slope surveys conducted by the National Marine Fisheries Service since January 2002. Sexes were equally represented, with females comprising 50.1% and males 49.9%. Females ranged from 199-610 and males from 195-635 mm total length (TL). For age and growth analysis, sectioned vertebrae were read 3 times and APE (0.08), CV (0.13) and D (0.07) precision values calculated. Ages were assigned based on agreement of at least two independent estimates, with an additional read if necessary. Marginal increment analysis was unsuccessful, therefore centrum edge analysis is being investigated. Age estimates indicate a minimum longevity of 17 years for female and 18 years for male B. kincaidii. Females grow faster (L_∞=533.9 mm; k=0.245; n=100) but males reach a larger size (L_∞=580.387mm; k=0.187; n=90). Analysis of residual sum of squares indicated no difference (p = 0.089) between male and female von Bertalanffy growth curves, and combined sexes produced values of L_∞=554.2mm and k=0.213. Females first mature at 450 mm (4 years), while males first mature 440 mm TL, 1 year earlier. However, 50% maturity was similar between sexes: 467 mm and 7.0 years for females and 492 mm and 7.5 years for males.

Skates have long been a common component of bycatch and discards among eastern North Pacific trawl fisheries, however, very little is known of their biology, distribution, or abundance throughout this region. In California, skate landings have markedly increased since the early 1990's, but associated species and population-level effects are unknown. Fishing pressure has notably impacted the abundance, population structure, and distribution of skates in the North Atlantic, emphasizing the need for baseline biological information of this poorly known group. Since September 2002, members of the Pacific Shark Research Center have been working in cooperation with the National Marine Fisheries Service (NMFS) Santa Cruz Laboratory to investigate the life history, ecology, and systematics of central California skates. Data are being collected from monthly NMFS longline and trawl surveys across five depth strata ranging from 18-823 m. Here we report on the reproductive biology of the two most common skate species collected in these surveys, California (Raja inornata) and longnose (R. rhina). Raja inornata ranged from 17.3 to 72.2 cm TL with a F:M sex ratio of 1:0.8 (n = 299). First maturity was observed at 54.5 cm TL among females and at 50.1 cm TL for males. Raja rhina ranged from 16.3 to 131.0 cm TL with a F:M sex ratio of 1:1.3 (n = 1,176). First maturity was determined to be 73.1 and 61.9 cm TL for females and males, respectively. The results presented are part of an ongoing, broad-based study developed to determine critical life history parameters that are essential for effective management of these and other chondrichthyan species.

Conservation and Management of Deepsea Chondrichthyan Fishes, Dunedin, New Zealand
27-29 November 2003

The reproductive biology and habitat utilization of skates collected along the eastern Bering Sea continental slope was studied (EBSCS). Data were collected during a National Marine Fisheries Service (NMFS) exploratory research cruise along the EBSCS during June-July 2002. A total of 1,330 specimens comprised of nine species were examined for reproductive information. The survey area extended the length of the EBSCS from northwest of Unalaska Island (55° 95'N, 168° 51 92'W) to the southern Navrin Canyon (60° 16'N, 179° 68'W) in waters ranging from 209 to 1,556 m deep. The survey area was divided into two strata types, one by area and another by depth. The EBSCS can be characterized by three distinct habitats; a broad, gentle, sloping area referred to as shelf habitat, areas bisected by submarine canyons referred to as canyon habitat, and areas of steep profile referred to as slope habitat. Skates are an important component of the demersal fish community along the EBSCS and are commonly caught in groundfish fisheries. Despite the abundance and diversity of skates in this region very little is known about their basic life history and ecology. The results presented are part of an ongoing, broad-based, study of the demersal chondrichthyan fauna in the eastern North Pacific and Bering Sea.

WSN, Long Beach, California
7-10 November 2003

These findings are part of a broad-based ecological investigation into the life history of three deep-sea catsharks (Scyliorhinidae), Apristurus brunneus, A. kampae and Parmaturus xaniurus, in the eastern North Pacific. Preliminary results on the distribution, abundance, and reproductive biology of these species off central California will be presented. Specimens were collected from trawl and longline survey cruises by the National Marine Fisheries Service (NMFS) from June 2002 through May 2003 from Año Nuevo to Point Sur, California. Distribution, occurrence, and abundance of specimens were analyzed to identify trends associated with season, depth, maturity, sex, and species. On average, longline hauls were mainly comprised of P. xaniurus, with an occasional catch of gravid female A. brunneus. Parmaturus xaniurus were usually found less than 485 m deep. Conversely, trawl cruises were primarily comprised of Apristurus spp. Apristurus brunneus were typically found between 300-942 m, while A. kampae occurred deeper than 1,005 m. The total lengths at 50% reproductive maturity were determined for males and females of all three species.

AES, Manaus, Brazil
June 27 - June 30 2003

* BIZZARRO, JOSEPH J.; CAILLIET, GREGOR M. Pacific Shark Research Center, Moss Landing Marine Laboratories, 8272 Moss Landing Rd., Moss Landing CA, 95039, USA
Feeding habits of the dominant ray species in the Almejas Bay (B.C.S., Mexico) artisanal fishery
Rays are one of the most abundant and ubiquitous groups of fishes in tropical and subtropical marine nearshore environments, where they often occupy high trophic levels. Global fishing pressure has increased on rays, typically without regulations or catch records. In Almejas Bay, Baja California Sur, an artisanal ray fishery operates primarily from April through August. Sampling of rays from this fishery for diet composition was conducted at Puerto Viejo, in June 1998-2000 (20 days, 34 vessel trips) and August 1998-1999 (35 days, 92 vessel trips), with 62 supplemental samples collected in 2001 and 2002. Of 4,035 elasmobranchs landed among at least 22 species, four species (Rhinobatos productus, Dasyatis dipterura, Narcine entemedor, and Gymnura marmorata) comprised 91.7% of the catch. Sex ratios, length frequencies, CPUEs (number/vessel) and a description of the fishery will be presented. This fishery peaked in June (total CPUE = 42.74), targeting mainly gravid female R. productus (CPUE = 21.48) and N. entemedor (CPUE = 10.74). In August, the fishery operated at a diminished capacity (total CPUE = 22.30), subsisting primarily on resident populations of D. dipterura (CPUE = 9.46) and G. marmorata (CPUE = 4.74). Stomachs and foreguts excised, preserved, and examined from 2,184 total specimens provided data on ontogenetic, intergender, and interannual differences in diet and facilitated comparisons of dietary overlap. Rhinobatos productus preyed primarily on crustaceans (shrimp and crabs) and, to a lesser extent, polychaetes with fishes also taken by large specimens. All sizes of G. marmorata consumed exclusively teleost fishes with a single occurrence of a squid. The diet of D. dipterura consisted mainly of epibenthic and infaunal invertebrates, including pea crabs, small bivalves, and polychaetes. Narcine entemedor fed primarily on polychaetes, sea slugs, and eels. The diets of these species did not exhibit a high degree of overlap, potential facilitating their coexistence.

EBERT, DAVID A. Pacific Shark Research Center, Moss Landing Marine Laboratories, 8272 Moss Landing Rd., Moss Landing, CA, 95039, USA
Reproductive biology and habitat utilization of skates along the eastern Bering Sea continental slope
The reproductive biology and habitat utilization of skates collected along the eastern Bering Sea continental slope was studied (EBSCS). Data were collected during a National Marine Fisheries Service (NMFS) exploratory research cruise along the EBSCS during June-July 2002. A total of 1,330 specimens comprised of nine species were examined for reproductive information. The survey area extended the length of the EBSCS from northwest of Unalaska Island (55° 95'N, 168° 51 92'W) to the southern Navrin Canyon (60° 16'N, 179° 68'W) in waters ranging from 209 to 1,556 m deep. The survey area was divided into two strata types, one by area and another by depth. The EBSCS can be characterized by three distinct habitats; a broad, gentle, sloping area referred to as shelf habitat, areas bisected by submarine canyons referred to as canyon haitat, and areas of steep profile referred to as slope habitat. Skates are an important component of the demersal fish community along the EBSCS and are commonly caught in groundfish fisheries. Despite the abundance and diversity of skates in this region very little is known about their basic life history and ecology. The results presented are part of an ongoing, broad-based, study of the demersal chondrichthyan fauna in the eastern North Pacific and Bering Sea.

* FLAMMANG, BROOKE E.; EBERT, DAVID A.; CAILLIET, GREGOR M. Pacific Shark Research Center, Moss Landing Marine Laboratories, 8272 Moss Landing Rd, Moss Landing, CA, 95039-9647, USA
Preliminary findings on the distribution, abundance, and reproductive biology of deepsea scyliorhinids off central California
These findings are part of a broad-based ecological investigation into the life history of three deep-sea catsharks (Scyliorhinidae), Apristurus brunneus, A. kampae and Parmaturus xaniurus, in the eastern North Pacific. Preliminary results on the distribution, abundance, and reproductive biology of these species off central California will be presented. Specimens were collected from trawl and longline survey cruises by the National Marine Fisheries Service (NMFS) from June 2002 through May 2003 from Año Nuevo to Point Sur, California. Distribution, occurrence, and abundance of specimens were analyzed to identify trends associated with season, depth, maturity, sex, and species. On average, longline hauls were mainly comprised of P. xaniurus, with an occasional catch of gravid female A. brunneus. Parmaturus xaniurus were usually found 72 less than 485 m deep. Conversely, trawl cruises were primarily comprised of Apristurus spp. Apristurus brunneus were typically found between 300-942 m, while A. kampae occurred deeper than 1,005 m. The total lengths at first reproductive maturity were determined for all species using nidamental gland width, egg diameter, and outer clasper length measurements, as well as gonadosomatic indices (GSI) for males and females. Size at first reproductive maturity as determined by GSI is being compared to the maturation of other sexual organs to determine if development is synchronous. Initial analyses are attempting to determine if reproductive seasonality is evident by associated changes in the GSI and hepatosomatic index (HSI).

MOLLET, HENRY F. Moss Landing Marine Laboratories, 8272 Moss Landing Road, Moss Landing, CA 95039, USA
Comparison of elasticity patterns of elasmobranchs and mammals with review of vital parameters of lamnids
Vital parameters (age-at-first-reproduction, maximum-reproductive-age, age-specific fertilities, and age-specific mortalities) of lamnids were reviewed. Despite progress in the last 20 years, vital parameters of lamnids and many other elasmobranchs are not sufficiently well-known to produce reasonably accurate population growth rates (l). Luckily, the elasticity pattern of a species that is needed to evaluate management proposals is fairly robust and does not require an accurate l. Furthermore, there is no need to calculate l because the elasticity pattern is determined by age-at-first-reproduction (a) and generation time (Abar) alone, with gestation period (GP) providing a refinement: E(fertility) = E1 = 1/Abar; E(juvenile survival) = E2 = (a - GP) E1; E(adult survival) = E3 = 1 - E2 = (Abar - a + GP) E1. These are lower-level elasticities of the vital parameters as they appear in a life history table and E2 includes survival to age one. Therefore, they do not sum to one but are easily normalized. The exclusion of survival to age one from E2 distorts the elasticity pattern, in particular for species with low age-at-first reproduction. Abar is usually not known. However, using an Abar estimate based on the mean Abar/a ratio of 60 elasmobranchs (1.31, coefficient of variation 9.3%, range 1.1-1.8) provided promising results. The elasticity pattern of elasmobranchs as a function of age-at-firstreproduction indicated that E2 is largest for all elasmobranchs if a > 1 yr (valid for most if not all elasmobranchs). Accordingly, protection of juveniles will provide the most effective measure to reverse population declines if that has been observed for an elasmobranch species. The mean Abar/a ratio of 50 mammals (2.44, coefficient of variation 33.5%, range 1.2-5.0) is larger and more variable compared to that of elasmobranchs and, accordingly, the elasticity pattern is more complicated.

* SMITH, WADE D., CAILLIET, GREGOR M., and MARIANO MELENDEZ, EVERARDO (WDS, GMC) Pacific Shark Research Center, Moss Landing Marine Laboratories, 8272 Moss Landing Rd., Moss Landing, CA, 95039, USA; (EMM) Universidad Autónoma de Baja California Sur, La Paz, BCS, MX
Aspects of the life history and population structure of the diamond stingray, Dasyatis dipterura
Dasyatis dipterura (Jordan and Gilbert 1880; often inappropriately referred to as D. brevis) inhabits shallow, coastal waters from southern California to Peru, including the Galapagos and Hawaiian Islands. Although D. dipterura is a common component of artisanal elasmobranch fisheries and trawl fishery bycatch throughout western Mexico, very little is known of the life history of this stingray. Biological information was obtained from 1,119 fishery-derived specimens from the Magdalena Bay Lagoon Complex, Baja California Sur, Mexico. Sampling was conducted during 1998-2000 in four fishing camps. The sex ratio at the primary study site, Puerto Viejo, was 2.32:1 in favor of males in the 1998-99 landings (450 male:194 female; c_{2 0.05, 1} = 101.76). Specimen disc widths (DW) ranged from 25-89 cm, with females reaching greater sizes than males. Our largest recorded male measured 60 cm DW. Based on examination of reproductive tracts and clasper length-DW relationships in males, size-at-first-maturity was determined to be 45 and 57 cm DW for males and females, respectively. The average DW of females observed in the fishery was 52.1 cm, indicating that the majority of females landed in the fishery were immature. Growth characteristics were estimated by a detailed examination of banding patterns present in thin-sectioned vertebral centra. Age estimates were obtained from 358 specimens (160 male, 198 female). The maximum age, based on vertebral band counts, was 29 16.5 for males and 28 for females. Age-at-first maturity was determined to be 6-8 for males and 8-12 for females. Gompertz, logistic, and von Bertalanffy growth models were fit to the age-at- DW/weight data for the sexes combined and separately. The annual nature of band deposition was supported through centrum edge and marginal increment analyses. Von Bertalanffy growth parameters, empirical longevity, and mortality calculations will be presented and compared to published values obtained for other elasmobranchs.

SMITH, WADE D., EBERT, DAVID A., BIZZARRO, JOSEPH J., and * CAILLIET, GREGOR M. Pacific Shark Research Center, Moss Landing Marine Laboratories, 8272 Moss Landing Road, Moss Landing, CA, USA
Distribution, abundance, and reproductive status of skates landed in groundfish surveys off central California, USA
Although skates have long been a common component of bycatch and discard among eastern north Pacific trawl fisheries, very little is known of their biology, distribution, or abundance throughout this region. In California, landings of skates have markedly increased since the early 1990's. Fishing pressure has notably impacted the abundance, population structure, and distribution of skates in the North Atlantic, emphasizing the need for baseline biological information of this poorly known group. Since September, 2002 members of the Pacific Shark Research Center have been working in cooperation with the National Marine Fisheries Service (NMFS), Santa Cruz Laboratory to investigate the life history, ecology, and systematics of central California skates. Data are being collected from monthly NMFS trawl surveys across five depth strata ranging from 18-823 m. We report on preliminary analyses of surveys conducted between September, 2002 and March, 2003. An approximate total of 1,500 specimens comprised of six species have been examined. The most abundant species, Raja rhina, comprised more than 50% of the overall catch followed by Bathyraja kincaidii, R. binoculata, R. inornata, and R. stellulata, respectively. Depth distribution and relative abundance of skates will be presented and compared by season, sex, reproductive status, and occurrence with the other chondrichthyans collected in these surveys.

Foro de Intercambrio Cientifico sobre Tiburones y Rajas, Mexico
May 2003

Aspects of the fishery and feeding ecology of the dominant ray species in Bahía Almejas (B.C.S., México)

Pacific Shark Research Center. Moss Landing Marine Laboratories. 8272 Moss Landing Rd. Moss Landing, CA. USA.95039. (831) 771-4419. Correo electronico: jbizzarro@mlml.calstate.edu

Sampling of rays from the Almejas Bay (BCS, Mexico) fishery for diet composition was conducted at Puerto Viejo during summer months from 1998-2002. Of over 4,000 elasmobranchs landed among at least 22 species, four species (Rhinobatos productus, Dasyatis dipterura, Narcine entemedor, and Gymnura marmorata) comprised 91.7% of the catch. Sex ratios, length frequencies, cpues (number/vessel) and a description of the fishery will be presented. This fishery peaked in June (total cpue = 42.7), targeting mainly gravid female R. productus (cpue = 21.4) and N. entemedor (cpue = 10.7). In August, the fishery operated at a diminished capacity (total cpue = 22.3), subsisting primarily on resident populations of D. dipterura (cpue = 9.5) and G. marmorata (cpue = 4.7). Samples were collected from over 2,200 specimens for dietary analyses. Rhinobatos productus preyed primarily on crustaceans (shrimp and crabs) and, to a lesser extent, polychaetes with fishes also taken by large specimens. All sizes of G. marmorata consumed exclusively teleost fishes with a single occurrence of a squid. The diet of D. dipterura consisted mainly of epibenthic and infaunal invertebrates, including pea crabs, small bivalves, and polychaetes. Narcine entemedor feed primarily on polychaetes, sea slugs, and eels. Differences in diet appear to be correlated with differences in morphology of the feeding apparatus.

The importance of life history studies (age, growth, reproduction, and demography) for effective fisheries management of sharks and rays

Moss Landing Marine Laboratories and Pacific Shark Research Center. 8272 Moss Landing Road, Moss Landing, CA 95039. USA. (831) 771-4432. Email. cailliet@mlml.calstate.edu

Fishery biologists require age in addition to length and weight data as essential parameters for age-based population models. Especially important are details about growth and mortality rates, life span, age at maturity, reproductive output, and the resultant demographic parameters, including net reproductive rate, generation time, and both instantaneous and finite population growth rate estimates. Fisheries for chondrichthyan fishes are not easily sustained, primarily due to their typical life history patterns (slow growth, late age at maturity, few offspring, and lengthy gestation periods) that make them vulnerable to overfishing, despite their relatively long life spans. I will review the ways in which elasmobranch fish life histories have been investigated, including age determination, age validation, reproductive studies, mortality estimates, and demographic analyses using both life history table analyses and matrices. The need for these studies on all exploited elasmobranch species will be emphasized using results from a global literature review on this subject, with emphasis on studies from the United States and Mexico.

Taxonomic status of commercially exploited butterfly rays (Family: Gymnuridae) from the Gulf of California and Mexican Pacific

¹Moss Landing Marine Laboratories (MLML) and Pacific Shark Research Center (PSRC), 8272 Moss Landing Road, Moss Landing, California 93940, USA, (831) 771-4419. Email: wsmith@mlml.calstate.edu. ²Centro Regional de Investigaciones Pesqueras de Guaymas (CRIP-Guaymas, INP). Calle 20 Sur 605, Col. Cantera. CP 85400 Guaymas, Sonora, México. ³Guy Harvey Research Institute, Oceanographic Center, Nova Southeastern University, Dania Beach, Florida 33004, USA, Tel. (954) 262-3653. jnielsen@nova.edu.

Butterfly rays are a primary component of artisanal elasmobranch fisheries throughout the Gulf of California and Pacific Baja California coast. Two of the three species recognized from the eastern Pacific, G. crebripunctata (Peters 1869) and G. marmorata (Cooper 1863), have been recorded in these landings. The validity of these species was first questioned in 1928, but evidence supporting synonymy has been inconclusive. To determine if G. crebripunctata and G. marmorata are valid species or male and female morphs of the same species, morphometric and molecular techniques were applied. Interspecific morphology was compared using multivariate statistical techniques to determine distinguishing characters. Tissue samples were collected from fishery-derived specimens from Sonora and Baja California Sur, México. Similarity of the two species was examined through direct sequence comparison and phylogenetic analyses of approximately 445 base pairs of the mitochondrial cytochrome b locus. Variation in the characters used to distinguish G. crebripunctata from G. marmorata can be attributed to proportional differences between sexes. Variation of cytochrome b sequences does not support separation of the two species. We conclude that G. crebripunctata is not a valid species and should be considered a junior synonym of G. marmorata.

AFS, Western Division, La Jolla, California
April 2003

Results of a two-year survey of Mexican artisanal fisheries targeting sharks, skates and rays in the Gulf of California

Robert Hueter*, John Tyminski, Gregor Cailliet, Joseph Bizzarro, Wade Smith, Fernando Marquez-Farias, Leonardo Castillo-Geniz and Carlos Villavicencio-Garayzar

* Presenter

(RH and JT) Center for Shark Research, Mote Marine Laboratory, Sarasota, Florida USA; tel 941-388-4441; fax 941-388-4312; rhueter@mote.org, johnski@mote.org

(GC, JB and WS) Moss Landing Marine Laboratories, Moss Landing, California USA; tel 831-632-4432; fax 831-632-4403; cailliet@mlml.calstate.edu, jbizzarro@mlml.calstate.edu, wsmith@mlml.calstate.edu

(FM) Instituto Nacional de la Pesca, SAGARPA, Guaymas, Sonora, Mexico; tel & fax 622-222-5925; fmarquez@gys.megared.net.mx

(LC) Instituto Nacional de la Pesca, SAGARPA, Mexico and Laboratorio de Ecologia Pesquera, CICESE, Ensenada, BC Mexico; tel 526-174-5050; fax 526-175-0545; lcastill@cicese.mx

(CV) Universidad Autonoma de Baja California Sur, La Paz, BCS Mexico; tel 521-121-1140; fax 521-121-1880; cvilla@calafia.uabcs.mx

Mexico is a major shark-fishing nation, and more sharks and their relatives (elasmobranch fishes) are taken in artisanal fisheries of Mexico's Gulf of California than in any other Mexican region. Concerns over the status of shark and ray populations under heavy fishing pressure in the Gulf led us to conduct a multi-institutional study of artisanal fishing effort and catches of sharks and other species over a two-year period (1998-99). Surveys revealed a total of 147 active fishing camps and 4,000-5,500 active fishing boats (pangas) targeting sharks to one degree or another. A total of 30 shark species and 24 batoid species were documented in the catch and juvenile sharks, pregnant sharks, small shark species (cazones) and rays were common. Catches of large sharks (tiburones) appear to have declined in recent years. Even with the great natural abundance and biodiversity of sharks in the Gulf, and with the small-scale, non-industrialized methods of artisanal fishermen, overfishing of shark stocks has probably occurred. The resulting information from our study is designed to be used by resource managers and user groups to formulate conservation and management priorities and plans for the Gulf of California.