Morse and Able: Distribution and life history of Scophthalmus aquosus 



683 



1 3 5 7 9 11 13 15 17 19 21 23 25 



Temperature °C 

 Figure 5 



Abundance of 2-4 mm windowpane, Scophthalmus 

 aquosus, larvae by subarea relative to bottom water tem- 

 perature during 1977-87. 



tures, which approaches the preferred temperatures, 

 suggests that spawning here may be triggered by the 

 highest temperatures available. Subareas 4 and 5 are 

 intermediate, with preferred temperatures available 

 from July to November (Fig. 6); yet spawning occurs 

 from May to December (Table 2; Fig. 4). Peak spawn- 

 ing occurs in October, a full three months later than 

 the first record of preferred spawning temperatures. 



Larval distribution and abundance 



Larvae were captured every month on the continen- 

 tal shelf (Table 2). January-April catches were very 

 low in subareas 1-3 and 5 and were totally absent 

 elsewhere. Larvae were caught in all subareas in May 

 and were most abundant in subarea 2. By June, lar- 

 val abundances were highest in subarea 4, and from 

 July to October subarea 7 had the highest larval 

 catches. Throughout August and September, abun- 

 dances in subareas 5 and 6 were intermediate, and 



o 



Month 



Figure 6 



Monthly temperature means and ranges by subarea of 

 the continental shelf of the northeastern U.S. during 

 1977-87. Shaded bar is the preferred spawning tem- 

 peratures (16-19°C) for windowpane, Scophthalmus 

 aquosus. 



catches in subareas 1—4 remained very low. By Octo- 

 ber, catches of larvae decreased somewhat in sub- 

 area 7 and increased in all other subareas. Novem- 

 ber catches showed a continued decline in subarea 7 

 and began to decrease in subareas 4-6. Catches in- 

 creased to their highest levels in subareas 1 and 2, 

 whereas subarea 3 catches remained at October lev- 

 els. In December, no larvae were captured in sub- 

 area 7, a few large larvae occurred in subarea 3, and 

 only moderate catches were made in subareas 4-6. 

 The nearly total absence of larvae in subareas 1—4 

 during December is attributed to the low number of 

 stations sampled and not necessarily to the disap- 

 pearance of larvae within this area. 



The size of larvae captured on the continental shelf 

 varies between subareas (Table 2). Few larvae >8 mm 

 were captured in subareas 1-4; only 18 of 3,282 sta- 



