Maturity, fecundity, and reproductive cycle of the spotted ratWsh, Hydrolagus colliei

Size at maturity, fecundity, and reproductive periodicity were estimated for the spotted ratWsh, Hydrolagus colliei (Lay and Bennett, 1839), oV the coast of California, Oregon, and Washington. Maximum body size and size at median maturity were greater for females than males. Skeletal muscle concentrations of the steroid hormones testosterone (T) and estradiol (E2) predicted similar, but slightly smaller sizes at maturity than the morphological criterion. Stage of maturity for males was estimated identically using internal organs or external secondary sexual characters, thus allowing non-lethal maturity assessments. Size at median maturity was greater north of Point Conception for females, and north of Cape Mendocino for males. Peak parturition occurred from May to October, with increased concentrations of E2 in skeletal muscle of females correlating with ovarian recrudescence during November to February. No signiWcant seasonal trends in female T were apparent, but mean female 11-ketotestosterone (11KT) was 300% greater in April than any other month during the parturition season. There was a marginal evidence for increased number and size of ova with maternal size. Extrapolation of the hypothesized 6 to 8-month egg-laying season to observed mean parturition rates of captive specimens yielded an estimated annual fecundity of 19.5–28.9 egg cases. DiVerences in fecundity among higher taxonomic classiWcations of chondrichthyans were detected with chimaeriform Wshes more fecund than lamniform, myliobatiform, squaliform, and rhinobatiform Wshes, and less fecund than rajiform Wshes.