FISHERY BULLETIN: VOL. 78, NO. 3 



larvae could have gone undetected. The same 

 problem occurred in defining the time of disap- 

 pearance, for larvae were abundant on 14 Sep- 

 tember 1971 and 1972 but the next sampling was 

 not conducted until 26 October 1971 and 16 Oc- 

 tober 1972. Only one Stage I larva was found in 

 October 1971. 



The Cape Henry data helped to determine more 

 closely the planktonic duration of the larvae since 

 a weekly sampling program was followed when 

 weather permitted. In agreement with the RANN 

 survey, the first larvae appeared in late July. Lar- 

 vae were present on 28 July but none were found 

 on 20 July. Larvae were found until 6 October; 

 none were collected on 13 October. From the 

 RANN and Cape Henry surveys it is apparent that 

 the planktonic occurrence of S. empusa extends 

 from the last week of July until the first week of 

 October, a period of almost 11 wk or about 2V2 mo. 



Only Stages I-IV and IX were collected by the 

 RANN survey (Figure 3). Bearing this in mind, 

 the RANN data showed the month of maximum 

 abundance to be August, with 0.37 larva/m^ col- 

 lected in 1971 and 0.59 larva/m^ in 1972; Sep- 



tember, July, and October trailed in order of de- 

 creasing abundance (Figure 2). The Cape Henry 

 data, on the other hand, showed a peak abundance 

 in September with 0.27 larva/m^ in 1976 followed 

 by August, July, and October 



All nine stages were collected during the Cape 

 Henry sampling program (Figure 4). In July, when 

 the larvae first began to appear. Stages I and II 

 were the only stages collected in abundance and 

 they were more numerous than in any following 

 month. Several specimens of Stages V and VIII 

 were also captured. All larval stages were present 

 in August with younger larvae generally being 

 predominant over older larvae. By early Sep- 

 tember the larvae had reached their peak abun- 

 dance. Although some of the younger larval stages 

 had begun to decline, they were still predominant. 

 The latest larval stages, VIII and IX, were becom- 

 ing increasingly abundant until October when 

 only Stage IX larvae were obtained. 



The abundance of larvae caught from each sub- 

 area during the RANN survey indicates that lar- 

 vae were more prevalent in the eastern and chan- 

 nel areas of the bay than in the western portion 



CO 



< 

 > 



< 



'A S O N 

 1971 



J J A S O N 

 1972 



J J 

 1973 



Figure 3. — Abundance of larval stages (I-IX) ofSquiUa empusa 

 collected from the lower Chesapeake Bay from August 1971 to 

 July 1973. Larval stages described in Morgan and Provenzano 

 (1979). 



FIGURE 4.— Abundance of larval stages (I-EX) and postlarva 

 (PL) of Squilla empusa collected at Cape Henry, lower 

 Chesapeake Bay, from June to October 1976. Larval stages de- 

 scribed in Morgan and Provenzano (1979). 



696 



