to a lesser extent, within each larval stage (Hadley 1905, 1908). 

 First and fourth stage larvae were initially positively photo- 

 tactic but reversed phototactic responses late in each stage. 

 Second and third stage larvae tended to be negatively photo- 

 tactic, however, response patterns were highly variable. 

 Huntsman (1924) indicated that direct exposure to sunlight 

 under experimental conditions could be lethal to first stage 

 larvae. Templeman (1936) reported increased survival and 

 growth rates for larvae cultured in darkness. These field and 

 laboratory observations indicate that ambient light levels may 

 directly affect availability of larval lobsters to neuston nets, 

 potentially affecting estimates of relative abundance and 

 survival. 



Field investigations demonstrate a predominance of stage I 

 larvae in daylight surface collections (Table 1). The progressive 

 decline in successive stage densities is presumably due to the 

 effects of mortality and behavioral factors, notably photo- 

 taxis, which affect availability and catchability of larvae. 



TEMPERATURE 



Scarratt (1964) found no relationship between surface water 

 temperature and production, relative abundance, and survival 

 of larvae in Northumberland Strait during 1949-61. The period 

 of larval production was, however, extended in cool years. 

 Scarratt suggested that larvae produced in the latter part of the 

 season may be unable to successfully molt into fourth stage 

 before winter. Caddy (1979) concluded that the cumulative 

 temperature sum (degree-days) required for completion of the 

 pelagic phase increases with decreasing water temperature and 

 further suggested that larvae produced in the later part of the 

 season (mid-late August) may not successfully molt if water 

 temperatures decline more rapidly than the accretion of nec- 

 essary degree-days. An apparent relationship between survival 

 and mean surface water temperature from April through 

 August inclusive was also indicated. Sherman and Lewis (1967) 

 reported mean surface water temperatures of 13.7°-15.0°C 



Table 1. — Summary of published accounls of larval American lobster sampling programs conducted from soul hern New England lo Newfoundland in daylight surface tows. 



(Only daylight tows with complete catch composition dala are included.) 



Year 



Location 



Sample Percent stage composition Total no 



period i fi Til fv larvae 



No. 

 lows 



Tow Tow 



speed duration 

 (km. hr) (min) 



Gear 



Source 



1936 



Nova Scotia 



July-Aug. 



95. S 



1936 



Northumberland 

 Strait 



July-Aug. 



98. 1 



0.3 



0.6 



324 



50 



60 



1 m plankton 

 1 m plankton 



Templeman 1937 



Smith 1937 (cited 

 by Stasko I9S0) 



1938-40 Newfoundland 



June-Sepi. 54.4 13.6 IK. 9 13.1 



1,037 



1 m plankton 



Templeman and 

 Tibbo 1945 



1948-61 Northumberland June-Sept. 77.9 I3.S 4.7 3.6 298,872 



Strait 



1.8 



30 



3.7x0.9 m 

 neuston 



Scarratt 1964 



1962-63 Northumberland June-Sept. 88.8 S.6 2.1 0.5 11,955 44S 



Strait 



1.8 



30 



3.7x0.9 m 

 neuston 



Scarratt 1973 



1965-66 Gulf of Maine June-Sepi. 80.4 1.9 0.3 17.4 368 2IS 



10-30 



I m plankton 

 2x1 m neuston 

 1 x0.5 m neuston 



Sherman and Lewis 

 1967 



1966-67 Offshore S. New Junc-Aug. 47.9 14.3 2S.6 9.2 119 96 



England 



30 



1.5 m plankton 



Lund and Stewart 

 1970 



1968 Long Island 



Sound 



June-Auc. 34.7 23.8 23.6 17.9 1.367 145 



5.6-6.5 



30 



1.5 m plankton 



Lund and Stewart 

 1970 



1966 Nova Scotia 



Julv-Aue. 94.9 4.4 0.4 0.3 1.9S4 100 



1.8 



30 



3.7x0.9 m 

 neuston 



Scarratt 1968 



1968 Nova Scotia 



Julv-Aue. 90.2 2.0 0.4 7.4 ^46 100 



1.8 



30 



3.6x0.9 m 

 neuston 



Scarratt 1969 



1975 Nova Scotia 



June-Aua. 91.7 7.8 0.5 



193 



7.4 



0.4x0.4 m 

 neuston 



Harding el al. 

 1979 



1976 Scotian Shelf Aug. 



1.5 8.5 19.7 63.4 142 



4.6-9.3 



15-30 



I m neuston 



I m plankton 



Issacs-Kidd Trawl 



Stasko (see text 

 footnote 2) 



1978 Nova Scotia 



June-Aug. '69.6 '22.6 '6.1 1.7 925 81 



B.iveJ on production estimaies. 



5.4-7.: 



15-20 



0.4x1.1 m 



partitioned 



neuston 



Harding et al. 

 (1982) 



