Age and size at sexual maturity for the winter skate, Leucoraja ocellata, in the western Gulf of Maine based on morphological, histological and steroid hormone analyses

Abstract

SynopsisWe determined age and size at sexual maturity in male and female winter skates, Leucoraja ocellata, from the western Gulf of Maine. Age estimated from vertebral band counts resulted in an Index of Average Percent Error (IAPE) of 5.6%, suggesting that this method represents an accurate approach to the age assessment of L. ocellata. Size at sexual maturity was assessed by evaluating three endpoints: steroid hormone concentrations, and morphological and histological criteria. Our results suggest that 50% maturity in males occurs at a total length of 730 mm and at 11 years of age. For females, our results suggest that 50% maturity occurs at a total length of 760 mm and between 11 and 12 years of age. Collectively, our study suggests that analyzing a combination of reproductive parameters offers an accurate estimation of sexual maturity in the winter skate. Moreover, our results indicate that L. ocellata is a late-maturing and long-lived species, characteristics which make it highly susceptible to over-exploitation by commercial fisheries.

Indication of Density‐Dependent Changes in Growth and Maturity of the Barndoor Skate on Georges Bank

“…For MIA, SPOT basic software (Diagnostic Instruments) was used to incorporate pointto-point distance measurements into the digital image spanning the length of the final opaque band and the penultimate opaque band from the edge of the centrum. The ratio of these two values was then calculated as the marginal increment (Sulikowski et al 2005b(Sulikowski et al , 2007 and plotted by month of capture.…”

“…Females.-Sexual maturity in females was assessed by examining developmental changes in the gross morphology of the reproductive tract (Sulikowski et al 2005b(Sulikowski et al , 2006(Sulikowski et al , 2007. The oviducal gland and ovaries were removed, blotted dry, and weighed to the nearest gram.…”

“…Clasper length (CL), defined as the distance from the posterior of the cloaca to the posterior tip of the clasper, was recorded for each specimen. To further assess maturity, histological analysis of testes was conducted following the protocol of Sulikowski et al (2005b). After obtaining testes weight, a thin cross section was removed from the medial lobe of the testis and fixed in 10% buffered formalin.…”

“…Male maturity was classified by specimens having calcified claspers >19 mm, developed testes >12 g, and >23% mature spermatocytes. We adopted these criteria from previous studies that reported similar characteristics for mature rajid species (Sulikowski et al 2005b(Sulikowski et al , 2006Cicia et al 2009). …”

A comparison of reproductive parameters of the Bering skate, Bathyraja interrupta, from two Alaskan large marine ecosystems

“…The stages of spermatogenesis were classified as: stage I, germinal zone; stage II, early spermatocysts; stage III, spermatocytes; stage IV, spermatids; stage V, immature spermatozoa; stage VI, mature spermatocysts; and stage VII, empty spermatocysts (Maruska et al 1996;Ebert et al 2008a). Since the developmental stages of spermatogenesis have been well described for skates, and hormonal analysis has confirmed that spermatocyst and spermatid stages are associated with reproductive readiness (Sulikowski et al 2005(Sulikowski et al , 2006, we concentrated on stages III-VI (Maruska et al 1996). For ease of interpretation, stage VII, consisting of empty spermatocysts and free spermatogonia, was combined with stage VI.…”