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Figure 2.— Weekly lobster larval densities at Stations 1, 2, and 3 in Penobscot 

 Bay, Maine, May-September 1976. 





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Figure 3. — Surface and bottom water temperatures at Stations 1, 2, and 3 in Pe- 

 nobscot Bay, Maine, June-September 1976. 



cloud cover. For all larvae, 84% were collected when cloud 

 cover was >50% and 62% of the larvae were obtained on 

 completely overcast days. Approximately 45% of all tows were 

 made on days when cloud cover was >50%. 



DISCUSSION 



but one larva were collected from 16 June through 26 July. 

 Stage I larvae dominated the catch, initially appearing at the 

 southernmost station (No. 3) followed by their appearance at 

 station 2, 2 wk later. Only one stage II larva and no stage III 

 larvae were collected during the study. Stage IV larvae were 

 initially found during the later part of July. 



Catch by Station 



Throughout the sampling period no larvae were found at 

 station 1. At station 2, 17 larvae (14 stage I; 1 stage II; and 

 2 stage IV) were collected during 1 through 26 July. The 2 

 stage IV larvae were found in near-surface waters at the end of 

 this period. A peak density of 1.62 larvae/ 1,000 m s occurred 

 8 d after the first occurrence of larvae in neuston samples. 



Highest densities of larvae were recorded at station 3 where 

 38 stage I and 3 stage IV lobster larvae were collected. Stage 

 I larvae were initially found on 16 June. Higher bottom tem- 

 peratures were recorded at station 3 (Fig. 3), resulting in earlier 

 hatching at this station than station 2. Hatching intensity, as 

 reflected by the presence of stage I larvae, peaked at a density 

 of 2.89 larvae/ 1,000 m\ 9 d after the initial occurrence of 

 larvae (bottom temperature = 11°C). Hatching apparently 

 ceased after 16 July, after which 2 stage IV larvae were found 

 1 wk later and 1 stage IV larva was collected on 31 August. 



Relation to Cloud Cover 



A relationship was noted between the number of larvae 

 taken and the degree of cloud cover. Ninety-two percent of the 

 stage I larvae were collected on days of cloud cover >50% 

 while all stage IV larvae (n = 5) were taken on days of <50% 



Overall abundance of lobster larvae at the Penobscot Bay 

 stations was low when compared with similar studies con- 

 ducted in New England coastal waters (Sherman and Lewis 

 1967; Lund and Stewart 1970) and along the eastern Canadian 

 coast (Scarratt 1964, 1968, 1973). We noted an average density 

 of 0.30 larvae/ 1,000 m' of water for the observed hatching and 

 development period (16 June-31 July) and 0.19 larvae/1,000 

 m J for the entire period of larval occurrence at stations 2 and 

 3. Based on the temporal distribution of larvae, it appears that 

 the majority of lobsters in Penobscot Bay spawned from early 

 to mid-June through July in 1976. 



Stage I larvae from the lower bay (station 3) showed the 

 earliest evidence of hatching (16 June) and the longest period 

 during which larvae were found (16 June through 31 August). 

 Scarratt (1964) suggested that stage I abundance is indicative 

 of underlying parent stock size. Thus, the higher stage I larval 

 abundance observed at station 3 possibly reflects a larger 

 parent stock at this location. 



An early warming of the Maine coastal waters in 1976 

 (Welch 1 ) stimulated hatching in mid-June. During the previous 

 year lobster larvae were first observed in Penobscot Bay during 

 early July (Central Maine Power Company 3 ). Hatching at 

 station 3 apparently began within 6 d after bottom tempera- 

 tures rose to 12.5 °C. Not until 21 June did the bottom 

 temperature at station 2 exceed 10°C and become warm enough 

 to stimulate hatching at this site. At station 2, stage IV larvae 



; W. R. Welch, Maine Department of Marine Resources, Fisheries Research 

 Station, W. Boothbay Harbor, ME 04575, pers. commun. October 1976. 



'Central Maine Power Company, Environmental Studies Department. 1976. 

 Lobster larval distribution in Upper Penobscot Bay, Maine. Unpubl. rep., 

 4 p. Central Maine Power Company, Augusta, MEU4336. 



60 



