Age, growth, reproduction and demography of the white-spotted ratfish, Hydrolagus colliei (Lay and Bennett, 1839)

M.S. Thesis Project:   

The purpose of this project is to study the life history of the white-spotted ratfish, Hydrolagus colliei (Lay and Bennett, 1839), as it relates to the present and potential direct or indirect harvest of the species.  Hydrolagus colliei is a member of the monophyletic class Chondrichthyes which includes the sub-classes Holocephali (chimaeroids or ratfishes) and Elasmobranchii (sharks and rays; Schaeffer 1981; Maisey 1984; Didier 1995; Grogan and Lund 2004).  This species is found from southeast Alaska (Wilimovsky 1954) to the tip of Baja and within the northern Gulf of California (Grinols 1965).  Their bathymetric distribution is quite broad, along the shelf and slope from the intertidal zone to 913m (Alverson et al. 1964).  Their minimum depth limit increases toward the equator, likely due to changes in vertical temperature distribution.  They are evolutionarily significant, with ancestors originating roughly 300 million years ago (Grogan and Lund 2004).  While there is not currently a directed fishery for H. colliei, they are incidentally captured and discarded by recreational fishermen, as well as commercial bottom trawl and longline fisheries. 

The impetus for researching the life-history of chondrichthyans has been well documented by many authors over the past three decades.  A high proportion of chondrichthyans studied to date have k-selected life-history characteristics such as slow growth rate, high longevity, late age of first maturation and low reproductive output (Cailliet and Goldman 2004).  These biological characteristics, combined with their tendency to aggregate in large groups may make chondrichthyans more susceptible to overfishing than teleosts (Holden 1973; Cailliet 1990; Hoenig and Gruber 1990; Bonfil 1994; Walker and Hislop 1998; Stevens et al. 2000).  Chondrichthyans which inhabit the deep waters of the continental slope or beyond exhibit k-selected life-history characteristics that are often even more extreme than their shallow-dwelling chondrichthyan relatives, making these species exceptionally vulnerable to overexploitation (Clark et al. 2003).  These biological obstacles to sustainable harvest are compounded by vast under-reporting of chondrichthyan catch (Bonfil 1994) and species misidentification or intentional combination of taxonomic categories in catch statistics (Dulvy et al. 2000). 

Specimens are being collected from the continental slope and shelf of California, Oregon and Washington, with the majority of individuals captured within the Monterey Bay, California, region. The dorsal spine will be used for ageing and stage of reproductive development will be determined based on macroscopic examination and histology of the reproductive tract.  The growth characteristics of the species will be modeled and age at first maturity and age at 50% maturity estimated.  Estimates of population growth, demography and elasticity analyses will be produced using the results of the age, growth and reproductive biology, combined with estimates of natural mortality.  Validation of ages will be attempted using the techniques of Marginal Increment Analysis (MIA) and tag-recapture with the chemical marker oxytetracycline.  Age validation, combined with estimates of reproductive output, will provide a baseline of life-history information for chimaeroids and introduce the methodology required for accurate life-history studies of other chimaeras and deep-water chondrichthyans.

Other ongoing research projects:

Description of a new species of chimaeroid fish from the Galapagos Islands, Ecuador (Holocephali, Chimaeriformes, Chimaeridae) 

This project is a collaborative effort with Dr. Dominique Didier Dagit (Millersville University, Millersville, PA) and Dr. David A. Ebert (Moss Landing Marine Labs/Pacific Shark Research Center, Moss Landing, California).  A single specimen of an undescribed species of the genus Hydrolagus was collected by Dr. John McCosker (California Academy of Sciences, San Francisco, CA) from the southeast Pacific, near the Galapagos Islands of Ecuador.  The preliminary description is as follows: It is in the genus Hydrolagus due to absence of anal fin.  Among species in the genus Hydrolagus, this species is differentiated by a combination of characters: small head with extremely short, rounded snout; dorsal spine, when fully depressed against the body, extending well beyond both the distal tip of the first dorsal fin and the origin of the second dorsal fin; preopercular and oral lateral line canals sharing a common branch from the infraorbital canal; dorsum medium brown with numerous circular and elongate white markings; ventrum a uniform white to tan.

Distribution of chimaeroid fishes of the Pacific Ocean (Holocephali, Chimaeriformes, Chimaeridae) 

Professional Presentations:

Barnett, L.A.K., Fitzhugh, G.R., Brusher, J.H., Taylor, J.C. and D.A. Devries.  Recruitment indices for the shallow water grouper complex: effective or not?  Oral presentation: Annual meeting of the American Fisheries Society, Florida Chapter, Brooksville, Florida, February 2004.

Awards Received:

Oregon Chapter of the American Fisheries Society undergraduate scholarship award 2002

Funding:

California Sea Grant Traineeship # R/F – 199.

Links:

A biological profile I authored on Somniosus pacificus (Bigelow and Schroeder 1944), the Pacific sleeper shark, is accessible on the website of the Pacific Shark Research Center: http://psrc.mlml.calstate.edu/elamon_may05.htm

Literature cited:

Alverson, D.L., Pruter, A.T. and L.L. Ronholt.  1964.  A study of demersal fishes and fisheries of the northeastern Pacific Ocean.  H.R MacMillan Lecture Series in Fisheries, Inst. Fish. Univ. British Columbia.  190 p.

Bonfil, R.  1994.  Overview of world elasmobranch fisheries.  FAO Tech Paper 341.  117 p.

Cailliet, G.M.  1990.  Elasmobranch age determination and verification: An updated review.  In: Elasmobranchs as Living Resources:  Advances in the Biology, Ecology, Systematics, and the Status of Fisheries.  Pratt, H.L., Gruber, S.H, and T. Taniuchi (eds.), NOAA Technical Report 90:157-165.

Cailliet, G.M and K.J. Goldman.  2004.  Age determination and validation in chondrichthyan fishes.  In: Biology of Sharks and Their Relatives.  Carrier, J.C., Musick, J.A. and M.R. Heithaus (eds.), CRC Press, Boca Raton, FL, 399-448.

Clark, M. W., Kelly, C. J., Connolly, P. L. and J. P. Molloy.  2003.  A life history approach to the assessment and management of deepwater fisheries in the Northeast Atlantic.  Journal of the Northwest Atlantic Fishery Science 31:401-411.

Didier, D.A.  1995.  Phylogenetic systematics of extant chimaeroid fishes (Holocephali, Chimaeroidei).  American Museum Novitates 3119.  86 p.

Dulvy, N.K., Metcalfe, J.D., Flanville, J., Pawson, M.G. and J.D. Reynolds.  2000.  Fishery stability, local extinctions, and shifts in community structure in skates.  Conservation Biology 14(1):283-293.

Grinols, R.B.  1965.  Grinols, R.B.  1965.  Check-list of the offshore marine fishes occurring in the northeastern Pacific Ocean, principally off the coasts of British Columbia, Washington, and Oregon.  M.Sc. Thesis.  University of Washington.  217 p.

Grogan, E.D. and R. Lund.  2004. The origin and relationships of early Chondrichthyes.  In: Biology of Sharks and Their Relatives. Carrier, J.C., Musick, J.A. and M.R. Heithaus (eds.), CRC Press, Boca Raton, FL, 3-32.

Hoenig, J.M. and S.H. Gruber.  1990.  Life-history patterns in the elasmobranchs: implications for fisheries management. In: Elasmobranchs as Living Resources:  Advances in the Biology, Ecology, Systematics, and the Status of Fisheries.  Pratt, H.L., Gruber, S.H, and T. Taniuchi (eds.), NOAA Technical Report 90:1-16.

Holden, M.J.  1973.  Are long-term sustainable fisheries for elasmobranchs possible?  Rapports et Procès-verbaux des Rèunions, Conseil International pour L’Exploration de la Mer 164:360-367.

Lay, G.T. and E.T. Bennett.  1839.  Fishes.  In: The Zoology of Captain Beechey’s Voyage.  Richardson, J., Vigors, N.A., Lay, G.T., Bennett, E.T., Owen, R., Gray, J. Buckland, W. and G.B. Sowerby (eds.), Henry G. Bohn, London, 71-75.

Maisey, J.G.  1984.  Chondrichthyan phylogeny: a look at the evidence.  Journal of Vertebrate Paleontology 4:359-371.

Schaeffer, B.  1981.  The xenacanth shark neurocranium with comments on elasmobranch phylogeny.  Bulletin of the American Museum of Natural History 169:3-66.

Stevens, J. D., Bonfil, R., Dulvy, N.K. & P.A. Walker.  2000. The effects of fishing on sharks, rays, and chimeras (Chondrichthyans), and the implications for marine ecosystems.  ICES Journal of Marine Science 57:476-494.

Walker, P.A. and G. Hislop.  1998. Sensitive skates or resilient rays? Spatial and temporal shifts in ray species composition in the central and north-western North Sea between 1930 and the present day. ICES Journal of Marine Science 55:392-402.

Wilimovsky, N.J.  1954.  List of the fishes of Alaska.  Stanford Ichthyological Bulletin 4(5):279-294.