1977 Sampling 



Despite substantially increased effort in 1977, only 206 lob- 

 ster larvae were obtained (Table 2). We initiated sampling in 

 early May but caught no lobster larvae until 14 June when first 

 and second stage individuals were collected (Fig. 2). Water 

 temperatures averaged 14°C (surface) and 1 1.5 °C (bottom) on 

 this date. Hatching apparently terminated in August. On the 

 last sampling date (10 August), surface tows contained ex- 

 clusively fourth stage larvae. Further sampling was prevented 

 because of net fouling by an unidentified brown alga. 



Seasonal catch distribution was bimodal with larval densities 

 peaking on 1 1 and 29 July (Fig. 2). On 29 July, we collected 

 73 larval lobsters, consisting of 52% stage I and 29% stage IV 

 individuals. Mean seasonal density (pooled station and molt 

 stage data) was 1.26 larvae/ 1,000 m\ well below the 1976 

 average density level (Table 2). Percent composition of the 

 total catch for stages I-IV was: 55.2%, 16.9%, 5.3%, and 

 22.6%, respectively. 



Stations 1 and 2, in the area of Brant Rock (Fig. 1), yielded 

 the greatest numbers of larvae. At station 1 , catch composition 

 was dominated by stage I larvae (74%), while at station 2, first 

 stage larvae comprised about 43% of the station total. Sam- 

 ples were dominated by first and fourth stage individuals 

 (Fig. 3). Of the total first stage lobsters sampled, 49% were 

 taken at station 1. Within the study area, catches of stage I 

 larvae generally decreased from north to south. Only 9.0% 

 and 6.4% of the total first stage larvae were collected at sta- 

 tions 5 and 6, respectively. 



We made 48 subsurface tows from 9 June to I August 1977. 

 Two larval lobsters were collected at station 6 on 23 June. 

 One was a first molt stage individual collected at a depth of 

 7.6 m and the other a fourth stage larva captured 3.0 m below 

 the surface. 



Effect of Wind Conditions 



Analysis of wind data for the spring and summer of 1975 

 and 1976 indicated that offshore winds from the southwest 

 and south-southwest prevailed. However, an inspection of 

 wind direction for respective sampling days revealed that 

 during the period of peak larval abundance the majority of 

 sampling trips coincided with onshore or alongshore winds. 

 Seventy-three percent of the tows were made during onshore 

 winds, and 82% of the larvae were collected when winds were 

 onshore. Consequently, we could not statistically compare the 

 effect of onshore-alongshore winds versus offshore winds or 

 the dispersion and resultant concentration of lobster larvae 

 in the study area. 



Spatial and Temporal Distribution 



Kruskal-Wallis tests indicated no significant difference 

 (P > 0.20) in density of stage I larvae between stations sam- 

 pled in 1976 and 1977. There was no significant difference 

 (P > 0.20) in density of stage IV larvae between stations for 

 the same 2 yr. 



Temporal distribution of mean pooled lobster larvae densi- 

 ties by molt stage and water temperature data are given for 

 1975-77 in Figure 2. We estimated the period of occurrence 

 of larvae in the water column ranged from 46 to 62 d over the 

 time and area studied. 



10- 



5- 



STAGE I 



m 



m 



A 



5- 



STAGE II | — I 



u 



nu 



F^Eafe 



20 



< 



5 



o 



z 



D 



m 



22 



50' 



20 



| STAGE IV 



n W6 



ij 



i 



1 



) 2 3 4 5 6 

 STATIONS 



Figure 3.— Lobster larvae density by molt stage collected in neuston tows in 

 western Cape Cod Bay, 1976-77. 



51 



