LARVAL STAGE 



I 



JUNE JULY 



AUG 



of lobster larvae, this must be considered a preliminary 

 estimate. 



For comparative purposes, a minimum estimate of potential 

 stage I production in Statistical Area 4 was derived using pop- 

 ulation size determined by cohort analysis (Jones 1974), size 

 at sexual maturity (Russell et al. footnote 5), and fecundity 

 (Saila et al. 1969). Commercial catch data (B. Simon 9 ) for Sep- 

 tember 1977 to 30 July 1978 were employed in this analysis; 

 this interval spans the egg bearing period for lobsters which 

 would release larvae in 1978. It is implicitly assumed that the 

 catchability of ovigerous females is not altered. Size groupings 

 were arbitrarily defined based on molt increment data using 

 the minimum legal size at the time of this study (78 mm cara- 

 pace length) as a starting point. Terminal fishing mortality 

 (F t = 1.2) was determined from tag return data (Russell et al. 

 footnote 5) adjusted for the seasonal pattern of catches. Fe- 

 cundity for each molt class was calculated using the relation- 

 ship 



F= 0.02502 CL : 8647 



where F is fecundity and CL is the carapace length (mm) (Saila 

 et al. 1969). Estimated potential egg production for Statistical 

 Area 4 was 3.323 x 10 7 (Table 2). No estimate of the repro- 

 ductive contribution of females <78 mm CL was made, how- 

 ever ovigerous females composed < 1% of the 68-77 mm CL 

 female size class in research catches. The expanded survey 

 estimate of stage 1 production apparently underestimated 

 potential production by an order of magnitude. Nichols and 

 Lawton (1978) noted discrepancies between estimated larval 

 density of H. gammarus and potential production. Larvae are 

 not entirely confined to the surface layer (Scarratt 1973) 

 accounting, in pari, for this discrepancy. The contagious 

 distribution pattern and behavioral responses to environ- 

 mental conditions (light intensity, wind factors, etc.) which 

 alter availability compound the difficulty in estimating larval 

 abundance. 



Environmental Effects 



The influence of several hydrographic and climatological 

 factors on larval density was examined using stepwise multiple 



Figure 4. — Dail> production (no. 1.000 m J ) estimates of stage l-IV lobster larvae 

 during period of larval occurrence (1 June-22 August). 



B. Simon. Rhode Island Department of Environmental Management, 150 

 Fouler St.. Wickford, Rl 02852, pers. commun. 



Table 2. — Arbitrary size classes (carapace length, mm); proportion of each size class, proportion female, and proportion ovigerous in 

 research catches: estimated number of females in commercial catch from 1 September 1977 to 30 Jul> 1978 in statistical area 4: popu- 

 lation size of females based on cohort analysis; estimated numbers of ovigerous females in population: and average fecunditv. 



Size 



Proportion of 



Proportion 



Proportion 



Est 



no. females 



Est 



no. females 





Average 



class 



catch ! 



female' 



ovigerous' 





in catch 



in 



population 



No. spavvners 



fecundity' 



78-87 



0.823 



0.529 



0.073 





24.421 





33,683 



2,459 



7,581 



88-99 



.162 



.522 



.143 





4,938 





6,282 



898 



10,142 



100-112 



.011 



.444 



.375 





285 





658 



247 



14,866 



> 112 



.004 



.750 



.333 





175 





266 



89 



20,473 



Russell et al. (text footnote 5). 



•Parameters for cohort analyses by length groups (Jones 1974): K = 0.0966, L m = 184.58, M = 0. 1 5, F = 1 .2 (Russell et al. text foot- 

 note 5). 



'Average fecunditv for each size class using mean carapace length of each group and fecunditv relationship of Saila et al. (1969). 



26 



