FISHERY BULLETIN: VOL. 80, NO. 2 



Table 1.— Numbers of Arctica islandica in each gonadal development stage by 

 date for the period September 1978-May 1980: Data are pooled for shallow (A, B) 

 and deep (C, D) stations, respectively. Stage description: EA, early active; LA, 

 late active; R, ripe; PS, partially spent; S, spent. 



'Dredging prevented by bad weather. 

 2 No collection due to gear failure. 



A total of 667 A. islandica were of separate 

 sexes and the observed ratio of this sample was 

 1 :0.91 . These data are not significantly different 

 from a 1:1 sex ratio. This analysis omits the two 

 hermaphrodites. Recently, Thompson et al. 

 (1980b) have described the advanced age for sex- 

 ual maturity in A. islandica, and Ropes and 

 Murawski (1980) have examined the size and age 

 at sexual maturity of A. islandica collected from 

 a depth of 53-55 m south of Long Island, N.Y. 

 They found that individual A. islandica&s large 

 as 47 mm in length had undifferentiated gonads 

 and males began producing germinal cells at a 

 smaller size and younger age than females. 

 Small individuals were rare in the presentstudy. 

 Arctica islandica caught with the hydraulic 

 dredge ranged from 70 to 1 10 mm in shell length, 

 but were predominantly (84% of total) from 80 to 

 100 mm. The smallest specimen caught in the 

 nonhydraulic dredge measured 62 mm in length, 

 but most specimens (80% of total) were 80-100 

 mm. A record relating the length of each clam 

 examined to its gonadal development was not 

 kept in the present study; therefore a relation- 



ship between sex and length cannot be described. 

 The present data on sex ratio differ from those of 

 Jones ( 1980), who observed a sex ratio of 1 :0.72 in 

 a sample of 320 A. islandica of >75 mm individ- 

 ual length which were collected from offshore 

 New Jersey during the period April 1977-March 

 1979. 



DISCUSSION 



Data describing water column physical char- 

 acteristics are in general agreement with pre- 

 vious work in illustrating the seasonal, intense 

 thermocline, and indicate that mixing across 

 this phenomena is small during the summer 

 months. Partial oxygen depletion below the 

 thermocline during the summer is probably 

 strongly related to biological activity. 



The minor differences in gonadal development 

 in A. islandica between stations is, at first, sur- 

 prising considering the fact that the inshore, 

 shallower stations (A and B) were consistently 

 warmer than the offshore, deeper stations (C and 

 D) (Figs. 1, 2, 6); however, an assessment of go- 



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