161 



Abstract — The northwest Atlantic 

 population of thorny skates (Ambly- 

 raja radiata) inhabits an area that 

 ranges from Greenland and Hudson 

 Bay, Canada, to South Carolina. 

 Despite such a wide range, very little 

 is known about most aspects of the 

 biology of this species. Recent stock 

 assessment studies in the northeast 

 United States indicate that the bio- 

 mass of the thorny skate is below 

 the threshold levels mandated by the 

 Sustainable Fisheries Act. In order 

 to gain insight into the life history 

 of this skate, we estimated age and 

 growth for thorny skates, using verte- 

 bral band counts from 224 individuals 

 ranging in size from 29 to 105 cm 

 total length (TL). Age bias plots and 

 the coefficient of variation indicated 

 that our aging method represents a 

 nonbiased and precise approach for 

 the age assessment of A. radiata. Mar- 

 ginal increments were significantly 

 different between months (Kruskal- 

 Wallis P<0.001); a distinct trend of 

 increasing monthly increment growth 

 began in August. Age-at-length data 

 were used to determine the von Ber- 

 talanffy growth parameters for this 

 population: L x = 127 cm (TL) and 

 6 = 0.11 for males; L r = 120 cm (TL) 

 and 6 = 0.13 for females. The oldest 

 age estimates obtained for the thorny 

 skate were 16 years for both males 

 and females, which corresponded to 

 total lengths of 103 cm and 105 cm, 

 respectively. 



Age and growth estimates of the thorny skate 

 (Amblyraja radiata) in the western Gulf of Maine 



James A. Sulikowski 



Jeff Kneebone 



Scott Elzey 



Zoology Department, Spaulding Hall 

 46 College Road 

 University of New Hampshire 

 Durham, New Hampshire 03824 

 E mail address !for J A Sulikowski, senior author): 

 isulikowigihotmail.com 



Joe Jurek 



Yankee Fisherman's Cooperative 



P.O. Box 2240 



Seabrook, New Hampshire 03874 



Patrick D. Danley 



Department of Biology 

 University of Maryland 

 College Park, Maryland 20724 



W. Huntting Howell 



Zoology Department, Spaulding Hall 

 46 College Road 

 University of New Hampshire 

 Durham, New Hampshire 03824 



Paul C.W. Tsang 



Department of Animal and Nutritional Sciences 



Kendall Hall 



129 Main St. 



University of New Hampshire 



Durham, New Hampshire 03824. 



Manuscript submitted 21 August 2003 

 to the Scientific Editor's Office. 



Manuscript approved for publication 

 8 July 2004 by the Scientific Editor. 



Fish. Bull. 103:161-168(2005). 



The northeast skate complex consists 

 of seven species endemic to the waters 

 off the New England coast of the 

 United States (New England Fisheries 

 Management Council (NEFMC 1 - 2 ). In 

 the past, these skates were generally 

 discarded because of their low commer- 

 cial value (NEFMC 1 - 2 ). More recently, 

 the rapidly expanding markets for 

 human consumption of skate wing 

 and for use as lobster bait have made 

 three of these species (winter skate 

 [Leucoraja ocellata], little skate [L. 

 erinacea], and thorny skate [Amblyraja 

 radiata]) commercially more viable 

 (Sosebee, 2000; NEFMC 1 - 2 ). Despite 

 an increasing commercial importance, 

 harvests for skate in the U.S. portion 

 of the western north Atlantic remain 

 unregulated and have the potential to 

 over-exploit the stocks. Moreover, life 

 history information is almost nonex- 

 istent for most of these elasmobranch 

 fishes (Frisk, 2000 NEFMC 1 - 2 ). 



The available information from the 

 few skates that have been studied cat- 

 egorizes them as equilibrium strate- 

 gists (K selected) because they reach 

 sexual maturity at a late age, have a 

 low fecundity, and are relatively long- 

 lived (Holden 1977; Winemiller and 

 Rose, 1992; Zeiner and Wolfe, 1993; 

 Francis et al., 2001; Frisk et el., 

 2001, Sulikowski et al., 2003). These 



characteristics, coupled with the prac- 

 tice of selective removal of large in- 

 dividuals, make these animals more 

 likely to be over-exploited by commer- 

 cial fisheries (Brander 1981; Hoenig 

 and Gruber, 1990; Casey and Myers 

 1998; Dulvey et al., 2000; Frisk et 

 al., 2001). 



The thorny skate (Amblyraja radi- 

 ata) is a cosmopolitan species found 

 on both sides of the Atlantic ocean 

 from Greenland and Iceland to the 

 English Channel in the eastern At- 

 lantic (Compagno et al., 1989) and 

 from Greenland and Hudson Bay, 

 Canada, to South Carolina, United 

 States, in the western Atlantic (Rob- 

 ins and Ray, 1986; Collette and Klein, 

 2002). Along with this broad geo- 

 graphic range, marked differences in 

 size exist for specimens captured in 

 different regions of the Atlantic. For 



1 NEFMC (New England Fishery Man- 

 agement Council. 2001. 2000 stock 

 assessment and fishery evaluation 

 (SAFE) report for the northeast skate 

 complex. NEFMC, 50 Water Street, Mill 

 2 Newburyport, MA 01950. 



2 NEFMC (New England Fishery Man- 

 agement Council). 2003. Skate fish- 

 eries management plan. NEFMC, 50 

 Water Street, Mill 2 Newburyport, MA. 

 01950. 



