Diane Haas

Age, growth, and reproduction of the Aleutian skate, Bathyraja aleutica (Gilbert, 1896), from Alaskan waters

Diane Lee Haas

Email address: dhaas@mlml.calstate.edu

Diane with a 1.8 m big skate (Raja binoculata)

Graduated – Fall 2011

Skates (Chondrichthyes: Rajiformes) are the largest and most diverse group of the elasmobranchs, with approximately 236 valid species and 49 undescribed species worldwide (Compagno 2005). Globally, they are common and abundant components of demersal fish communities, and consequently, skate populations frequently represent a significant proportion of the biomass in commercial groundfish fisheries, either as targeted species or as incidental landings (Martin & Zorzi 1993; Walker & Hislop 1998). This is alarming because skates often exhibit k-selected life history characteristics such as slow growth, low fecundity, and late age at maturity, that may severely restrict their ability to sustain fishing pressure or recover from overexploitation (Holden 1974; Reynolds et al. 2005).

In Alaska, although skates represent the greatest proportion of non-targeted biomass landed, species compositions and relative abundance of skate landings remain unknown (Ormseth et al. 2008). This is largely because skates have been managed as part of the “other species” category, and historically only have been categorized as “skate unidentified”. With the development of a directed fishery in Kodiak in 2003-2004, and a limited skate fishery currently under development in Prince William Sound (Ormseth and Matta 2008), it is likely that skates will be increasingly targeted. However, almost nothing is known about the life histories of local species or the impact fishery exploitation has on them. The effective management of any species requires details of life history characteristics, especially age, growth, and reproduction, to be understood and incorporated. To increase our understanding of Alaskan skates, I assessed the life history characteristics of a common species, the Aleutian skate, Bathyraja aleutica (Gilbert 1896).

Bathyraja aleutica (Arhynchobatidae, Fowler 1934) is one of the largest deepwater batoids in the North Pacific, reaching a maximum total length of 161 cm. Among the complex of 15+ valid species of Bathyraja occurring in Alaska (Mecklenburg et al. 2002; Stevenson & Orr 2005), B. aleutica dominates the biomass in the eastern Bering Sea slope and throughout the Gulf of Alaska (Ormseth and Matta 2007). Despite its common occurrence in the bycatch of Alaskan fisheries, age and growth parameters, which are essential components of life history and used extensively in stock assessments, have not been estimated.

Objectives of this study are to: 1) assess the suitability of vertebral centra and caudal thorns for age estimation; 2) validate periodicity of growth band formation using centrum edge characteristics; 3) estimate age and growth parameters and longevity; 4) determine size and age at first, 50% and 100% maturity; 5) estimate fecundity; 6) describe seasonal reproductive patterns; and 7) determine if regional differences exist in age, growth, or reproductive parameters of B. aleutica from the eastern Bering Sea and Gulf of Alaska.

aleutian-skate

 

Other research projects

Torpedo ray systematics

 

Publications

Haas, D.L., and Ebert, D.A. 2008. First record of hermaphroditism in the Bering skate, Bathyraja interrupta. Northwestern Naturalist 89(3):181-185.

Ebert, D.A., Smith, W.D., Haas, D.L., Ainsley, S.M. and Cailliet, G.M. 2007. Life history and population dynamics of Alaskan skates: providing essential biological information for effective management of bycatch and target species. North Pacific Research Board Final Report 510, 124 p.

Haas, D.L., and Ebert, D.A. 2006. Torpedo formosa, a new species of electric ray (Chondrichthyes: Torpediniformes: Torpedinidae) from Taiwan. Zootaxa 1320:1-14.

 

Posters and Presentations

Haas, D.L., Ebert, D.A., & Cailliet, G.M. 2008. Comparative life history characteristics of the Aleutian skate, Bathyraja aleutica, in two Alaskan ecosystems. American Elasmobranch Society, Montreal, Canada.

Haas, D.L., Ebert, D.A., & Cailliet, G.M. 2008. Age, growth, and reproduction of the Aleutian skate, Bathyraja aleutica (Gilbert, 1896), in the eastern Bering Sea. Western Groundfish Conference, Santa Cruz, CA.

Haas, D.L., Ebert, D.A., & Cailliet, G.M. 2008. Age, growth, and reproduction of the Aleutian skate, Bathyraja aleutica (Gilbert, 1896), in the eastern Bering Sea. Alaska Marine Science Symposium, Anchorage, AK.

Haas, D.L., Ebert, D.A., & Cailliet, G.M. 2007. Age, growth, and reproduction of the Aleutian skate, Bathyraja aleutica (Gilbert, 1896), in the eastern Bering Sea. American Fisheries Society, San Francisco, CA. Poster.

Haas. D.L., and Ebert, D.A. 2007. Torpedo formosa, a new species of electric ray (Chondrichthyes: Torpediniformes: Torpedinidae) from Taiwan. American Elasmobranch Society, St. Louis, MO.

Haas, D.L., Ebert, D.A., and Cailliet, G.M. 2007. Age, growth, and reproduction of the Aleutian skate, Bathyraja aleutica (Gilbert, 1896), in the eastern Bering Sea. American Elasmobranch Society Meeting, St. Louis, MO. Poster.

Ebert, D.A., Smith, W.D., Haas, D.L., Ainsley, S.M., and Cailliet, G.M. 2007. Life history and population dynamics of Alaskan skates: Providing essential biological information for effective management of bycatch and target species. Alaska Marine Science Symposium, Anchorage, AK. Poster.

Ebert, D.A., Bizzarro, J.J., Haas, D.L., Neway, A.L., Ainsley, S.M., Smith, W.D., and Cailliet, G.M. 2006. Age, growth, and reproduction of four Alaskan softnose skates (Chondrichthyes: Rajiformes). Western Groundfish Conference, Newport, OR. Poster.

 

Awards Received

Outstanding Student Oral Presentation (Masters), Alaska Marine Science Symposium, January 2008

Best Student Poster Award, American Fisheries Society (Western Division), September 2007

 

Funding

Funding for this project has been provided by the North Pacific Research Board (Project numbers 510 and 715), and NOAA National Marine Fisheries Service through the National Shark Research Consortium’s Pacific Shark Research Center. Additional funding was provided by the Packard Foundation, American Elasmobranch Society, San Jose State University, and the Dr. Earl & Ethel Meyers Oceanographic Trust.

 

References

Coming soon