Figure 2. — Sampling locations for nel comparison siudy. 



The sampling variance was high and proportional to the 

 mean as is characteristic of lobster larvae data and most plank- 

 ton data (Cassie 1968). Consequently, the data were normal- 

 ized with a log (n + 1) transformation and a paired /-test was 

 performed on the complete data set. The mean difference of 

 total larval abundance from neuston net samples versus Tucker 

 net samples was significantly different Us = 6.42, / i(i7) = 2.90). 



When abundance is calculated over the area sampled (num- 

 ber per 1,000 m 2 ), the neuston and Tucker nets collected 

 approximately equal numbers of larvae (Table 1). The mean 

 difference in total abundance was not significantly different 

 (fc= 0.93; t mi) = 2.11). 



The Tucker net used in this study has a sampling volume 

 approximately 2.7 times that of the neuston net. The observed 

 ratio of abundance in Table 1 is approximately 2.9, indicating 

 that larvae may be concentrated in the uppermost 0.75 m. 



These observations indicate that densities of lobster larvae 

 (per 1,000 m 3 ) estimated from Tucker net samples can be 

 compared with neuston densities by considering ratios of 

 volumes filtered. However, such a factor would be applicable 

 only to samples collected under similar conditions. All samples 

 in this study were taken on sunny days when seas were 

 relatively calm (<1 m). Larval distribution in rough seas 

 and on cloudy days may be more dispersed and differences 

 observed would be smaller. 



ACKNOWLEDGMENTS 



Table 1. — Mean abundance ± standard deviation of lobster larvae (all stages) in 

 paired triplicate surface tows using a 1 m x 2 m neuston net and 2 m x 2 m 

 Tucker nel. 





Station 



Abundance 



per 1,000 m' 



Abundance 

 Neuston net 



per 1 ,000 nr 



Date 



Neuston net 



Tucker net 



Tucker net 



6/14/79 



NS-B 



37.1+44.1 



14.4 r 14.2 



27.9 ±33.0 



28.8 ±28.4 





PJ-C 



34.6 ±18.6 



14.3 ±15.7 



25.9 ±36.5 



28.7 ±26.8 



6/18/79 



NS-B 



6.4 + 4.1 



1.4±0.8 



4.6 ±3.0 



2.9 ±1.7 





PJ-C 



177.3+181.3 



47.3 + 33.7 



133.0+ 135.9 



94.5 ±67.3 



6/21/79 



NS-B 



6.1 ±5.2 



3.2 ±2.6 



4.5 + 3.8 



6.5 ±5.3 





PJ-C 



6.2 ±4.2 



3.1 ±0.8 



4.7 + 3.2 



6.3±l.5 



Grand mean and 











standard deviation 



44.6±91.1 



14.0 + 21.3 



33.4 + 68.3 



27.9 ±42.5 



when expressed on a volume basis (number per 1,000 m J ) the 

 neuston net collected two to four times as many larvae as the 

 Tucker net. 



The authors wish to thank M. Fogarty for the loan of the 

 neuston nets. This study was performed by Raytheon Ocean 

 Systems Company, under contract with New England Power 

 Company (Contract 24146). 



LITERATURE CITED 



BIBB, B. G., R. L. HERSEY, and R. A. MARCELLO, Jr. 



1983. Distribution and abundance of lobster larvae (Homarus americanus) 

 in Block Island Sound. U.S. Dep. Commer., NOAA Tech. Rep. NMFS 

 SSRF-775: 15-22. 

 CASSIE, R. M. 



1968. Sampling design. In D. J. Trantner (editor), Reviews on zooplankton 

 sampling methods, p. 105-121. UNESCO Press, Paris. 

 FOGARTY, M. J., M. A. HYMAN, G. F. JOHNSON, and C. A. GRISCOM. 

 1983. Distribution, relative abundance, and seasonal production of Ameri- 

 can lobster, Homarus americanus, larvae in Block Island Sound in 1978. 

 U.S. Dep. Commer., NOAA Tech. Rep. NMFS SSRF-775:23-28. 



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