A Comparison of Lobster Larvae Sampling 

 Using Neuston and Tucker Nets 



BRENDA GOLBERG BIBB,' RONALD L. HERSEY, : and ROCCO A. MARCELLO, JR. 3 



ABSTRACT 



A series of paired surface tows with aim x 2 m neuston net and a 2 m x 2 m Tucker net were made to 

 compare sampling efficiency for lobster larvae. The neuston net collected two to four times more larvae per unit 

 volume than the corresponding Tucker net. Both nets collected similar numbers of larvae if numbers are ex- 

 pressed per unit area. This indicates that larvae were concentrated in the upper 0.75 m of the water column. 



INTRODUCTION 



Both neuston and Tucker nets have been used to collect lob- 

 ster larvae along the New England coast. Neuston nets were 

 used in a study of geographic distribution of lobster larvae 

 in Block Island Sound (Fogarty et al. 1983) and Tucker nets in 

 a study of distribution and abundance off East Beach, R.I. 

 (Bibb et al. 1983). Because of the different nets used, the re- 

 sults of these surveys are not directly comparable. This study 

 was conducted to compare the sampling efficiency of the 

 neuston net with that of the Tucker net to determine whether 

 lobster larvae data collected using these two techniques are 

 comparable. 



METHODS 



Paired tows were made with a neuston net off the port side 

 and a Tucker net off the starboard side of the survey vessel. 

 About 25 cm of the neuston net and 10 cm of the Tucker net 

 were kept above the water's surface while towing. All tows 

 were made into the current at 1 m/s for 15 min. Sample vol- 

 ume and boat speed were estimated with a calibrated General 

 Oceanics Model 2030 flowmeter. 4 Volumes for each tow ranged 

 from approximately 2,000 to 4,000 m 3 (Tucker) and 1,500 to 

 2,000 m 3 (neuston). 



The neuston net had 1 m x 2 m opening and 4 m length with 

 a 1 mm mesh (Fig. 1). The opening and closing Tucker net was 

 8 m long with a 0.950 mm mesh (Fig. 1). The mouth of the 

 Tucker net was designed to sample at a 45° angle with a resul- 

 tant 2 m x 2 m sampling area. 



Samples were collected 14, 18, and 21 June 1979 at two 

 stations in Block Island Sound, NS-B and PJ-C (Fig. 2). Tri- 

 plicate paired tows were made at each station. Mean surface 

 temperatures for each sampling date were 15.4°, 16.7°, and 

 16.1 °C, respectively. During sampling, the sky was clear and 

 seas were calm. 



'Raytheon Company, P.O. Box 360, Portsmouth, RI 02871. 



Raytheon Company, P.O. Box 360, Portsmouth, R.I.; present address: 124 

 North Road, Kingston, RI 02881. 



'Yankee Atomic Electric Company, 1671 Worcester Road, Framingham, MA 

 07101. 



'Reference to trade names does not imply endorsement by Raytheon Company 

 or by the National Marine Fisheries Service, NOAA. 



Data comparisons were made in two ways: Per unit volume 

 (1,000 m 3 ) and per unit area (1,000 m 2 ). Abundance per unit 

 volume was calculated using the volume filtered as indicated 

 by the flowmeter. Abundance per unit area was calculated by 

 dividing the flowmeter volume by the depth sampled by each 

 net. These depths were 0.75 m for the neuston net and 1.9 m 

 for the Tucker net. 



RESULTS AND DISCUSSION 



A comparison of the total number of lobster larvae col- 

 lected in paired triplicate surface tows using neuston and 

 Tucker nets is shown in Table 1. These results indicate that 



IMM MESH NET 



CANVAS COLLAR 



TOWING YOKE 



OPENING AND CLOSING TUCKER NET 



Figure 1. — Diagrammtic representation of neuston and Tucker nets. 



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