538 



Fishery Bulletin 103(3) 



Statistical analyses 



The results are presented as means ±SEM and evalu- 

 ated by Kruskal Wallis analysis of variance followed 

 by a Tukey's post hoc test. Statistical significance was 

 accepted at P<0.05. To determine whether a relation- 

 ship exists in measured morphological and histological 

 reproductive parameters, a Pearson correlation analysis 

 (denoted as r) was performed. 



Results 



The lack of a robust sample size presents a potential lim- 

 itation for our study. However, over the last decade, there 



6 1 A 



has been an increasingly precipitous decline in thorny 

 skate populations in the Gulf of Maine, especially larger 

 size specimens (NEFMC 2 - 3 ). These declines were evident 

 in our sampling trips, because large, mature individuals 

 were rarely caught in most trawls. The data presented 

 in this article are the result of 84 sampling trips that 

 took place over the course of two years (approximately 

 three to four trips per month). Moreover, the recent pro- 

 hibition on thorny skate landings has put an end to any 

 prospects regarding collection of additional specimens 

 in the foreseeable future. Thus, the data set we have 

 presented represents the best available information on 

 the reproductive cycle for this species. 



Size ranges 



Mature female skates (?i=48) ranged from 

 820 to 1050 mm TL (mean=917 ±7 SEM) and 

 from 4.4 to 10.2 kg (mean=7.7 ±0.2 SEM) in 

 total body mass. Mature male skates (;? = 48) 

 ranged from 800 to 1040 mm TL (mean=952 

 ±11 SEM), and from 5.4 to 10.8 kg (mean=8.4 

 ±0.3 SEM) in total body mass. 



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



B 



Jan Feb Mar Apnl May June July Aug Sept Oct Nov Dec 



Figure 1 



Monthly changes in female thorny skates {Amblyraja radiata): 

 (A) Gonadosomatic index (GSI); (B) hepatosomatic index (HSI); 

 (C) shell gland weight; and (D) diameter of the two largest follicles. 

 Values are expressed as means +SEM. Sample sizes are indicated 

 above each month. Values designated with different letters are 

 significantly different from each other (P<0.05). 



Assessment of morphological parameters in 

 the female reproductive tract 



In females, the average GSI of skates captured 

 in July was lower (P<0.05) than those captured 

 in October and December, and those from Sep- 

 tember were lower than the specimens captured 

 in October, November, and December (Fig. 1A). 

 Because the number of samples from April con- 

 sisted of only two skates, we were unable to test 

 for statistical differences between other months. 

 Despite this limitation, the two specimens from 

 April displayed similar values to those in July. 

 Average HSI (Fig. IB) did not change <P>0.05) 

 over the sampling period. However, the aver- 

 age shell gland weight (Fig. 1C) from skates 

 captured in October was greater (P<0.05) than 

 those captured in September. Because all shell 

 glands from skates captured in February were 

 in the process of encapsulating ovulated eggs, 

 we were unable to obtain accurate individual 

 shell gland weights. 



There were no differences (P>0.05) observed 

 in the average diameter of the two largest 

 follicles (Fig. ID), and no pattern of follicle 

 dynamics was discerned. Also, fully formed 

 egg cases, or those in the process of formation, 

 were found in the uteri of skates captured 

 during all months of the year, except June 

 and September. 



Additional analysis revealed that GSI was 

 correlated to shell gland weight (r=0.53) and 

 average follicle diameter (r=0.4). Further- 

 more, HSI was also correlated to shell gland 

 weight (r=0.53) and average follicle diameter 

 (r=0.7). 



