542 



Fishery Bulletin 103(3) 



Comparisons 

 percentage of 



males and females over the course of 

 their reproductive cycles. Among them, 

 coordinated peaks in gonad weight and 

 steroid hormone concentrations in win- 

 ter skates (Sulikowski et al., 2004) and 

 epaulette sharks (Heupel et al., 1999) 

 were observed in males and females over 

 an annual cycle. In the present study, 

 mature spermatocysts (SVI) and per- 

 centage of female thorny skates with 

 egg cases were also synchronized over 

 the course of the study. In contrast, 

 Henderson and Casey (2001) found that 

 the gonadal cycles of male and female 

 lesser spotted dogfish were asynchro- 

 nous, which they hypothesized to be 

 due to the storage of sperm by females. 

 Sperm storage has been documented in 

 other female elasmobranch species as 

 well (e.g., Pratt, 1993; Maruska et al., 

 1996) and is thought to be a feature pri- 

 marily of species that are nomadic or 

 segregated by sex (Pratt, 1993). In the 

 current study, A. radiata was neither 

 segregated by sex (both genders were captured in the 

 same area and in the same trawls) nor found to be no- 

 madic in their movement patterns (Templeman, 1987; 

 Sulikowski, unpubl. observ. ). Moreover, because males 

 are capable of producing viable sperm and females ap- 

 pear to be reproductively active throughout the year, 

 there is probably no need for the population of thorny 

 skates that we sampled to store sperm. On the basis 

 of the above information, we believe that the reproduc- 

 tive cycle in the sampled population of thorny skates is 

 coordinated over an annual cycle. 



In summary, according to the reproductive strategies 

 outlined by Wourms (1977) and later by Hamlett and 

 Koob (1999), the results of the present study indicate 

 that thorny skates have a reproductive cycle that is con- 

 tinuous throughout the year. For females, this conclu- 

 sion was based on ovary weight, shell gland weight, and 

 diameter of the largest follicles (the preovulatory fol- 

 licles). For males, this conclusion was based on the pres- 

 ence of mature spermatocysts within the testes over the 

 course of the sampling period. Moreover, comparisons 

 between the proportion of mature spermatocysts within 

 the testes and the percentage of egg-case-bearing fe- 

 males indicate that the reproductive cycles of male 

 and female thorny skates are synchronized. Currently, 

 analyses of circulating steroid hormone concentrations 

 are in progress for the thorny skates used in the pres- 

 ent study, which may provide additional insight into 

 the regulation and timing of reproductive events in 

 this species. 



Acknowledgments 



Collection of skates was conducted on the FV Mystique 

 Lady. We thank Noel Carlson for maintenance of the fish 



25 



20 



Jan Feb March April May June July Aug Sept Oct Nov Dec 



Figure 4 



between the percentage of spermatocysts (SVI) and the 

 female thorny skates (A. radiata) with egg cases. 



at the U.N.H. Coastal Marine Laboratory. This project 

 was supported by a Northeast Consortium grant (no. 

 NA16FL1324) to PCWT, JAS, and PDD. 



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