Kelsey James
Age and growth of the starry skate, Raja stellulata Jordan and Gilbert 1880, comparing two techniques: thin sectioning and histology.
Kelsey C. James
M.S. Thesis:
Because humans rely heavily on oceanic resources, it is important to understand our impacts on exploited marine organisms. One major impact that must be understood is the incidental bycatch of fisheries. Bycatch species, such as skates, are generally poorly studied because of their lack of commercial value. Life history research is being conducted on many of these species to determine the impacts of fishing mortality on them and to relate that knowledge to our understanding of ocean ecosystems as a whole.
Even incidental capture can be deleterious to skate populations because they are known to grow slowly, mature late in life and have low fecundity like their relatives, the sharks. Efforts must be made to conserve these species and explore their life histories to better understand how to focus conservation efforts. There are at least eleven species of skate that are known to occur in California waters (Ebert 2003). The maximum age of those studied has varied from 12 to 20 years (Davis et al. 2007, Perez 2005, Zeiner 1991), but such information is unavailable for most species, including the starry skate, Raja stellulata Jordan and Gilbert 1880.
Raja stellulata is the species of focus for my thesis. It occurs along the California coast from inshore waters to 752 m, but is most commonly found in depths of < 100 m (Ebert 2003). Little is known of this species’ biology besides its occasional occurrence as bycatch in trawl and longline fisheries. I plan to explore its age and growth parameters by determining age at length from collected specimens and using the results to determine an appropriate growth curve; both which in turn increase the knowledge of R. stellulata’s life history.
My thesis objectives are to 1) determine appropriate ageing structures for R. stellulata, 2) estimate age at lengths of R. stellulata comparing two techniques: thin sectioning and histology, and 3) validate the age estimates with OTC injection, marginal increment ratio and centrum edge analysis techniques. If possible other life history aspects, such as reproductive biology or habitat selection will be added to my thesis as I progress.
Other projects:
My graduate coursework includes a Systematics class where I have the chance to describe a new species of Chimaera (Family Chimaeridae) of the Genus Hydrolagus that occurs off the California coast . Specimens have been collected from Baja California and are being examined to confirm that this is a valid new species. The scope of the class includes a thorough description of the species, comparing it to known species and submitting a manuscript for publication. The Chimaera’s typical habitat, the deep sea, has not been sampled in a uniform way, making the discovery of new species quite probable. For example, six new species from the family Chimaeridae were described in 2008 from Australian waters (Last et al. 2008).
References:
Davis, C.D., G.M. Cailliet and D.A. Ebert. 2007. Age and growth of the roughtail skate Bathyraja trachura (Gilbert 1892) from the eastern North Pacific. Environ Biol Fish 80:325-336.
Ebert, D.A. 2003. Sharks, Rays, and Chimaeras of California. University of California Press, Berkeley, California, 284 p.
Jordan, D.S. and C.H. Gilbert. 1880. Description of a new species of ray (Raia stellulata) from Monterey, California.roc US Nat Museum 3:133-135
Last, P.R., W.T. White, and J.J. Pogonoski. 2008. Descriptions of New Australian Chondrichthyans. CSIRO Marine and Atmospheric Research Paper: 022. 368 p.
Perez, C.R. 2005. Age, growth, and reproduction of the sandpaper skate, Bathyraja kincaidii (Garman, 1908) in the Eastern North Pacific. Masters Thesis, California State University, Monterey Bay and Moss Landing Marine Laboratories, California. 94 p.
Zeiner, S.J. 1991. Growth characteristics and estimates of age at maturity of two species of skates (Raja binoculata and Raja rhina) from Monterey Bay, California. Masters Thesis, California State University, Stanislaus and Moss Landing Marine Laboratories, California. 53 p.