Abundance and Distribution of Lobster Larvae 

 {Homarus americanus) for Selected 

 Locations in Penobscot Bay, Maine 



DANIEL M. GREENSTEIN, LEIGH C. ALEXANDER, and DARYL E. RICHTER 1 



ABSTRACT 



Larval lobster (Homarus americanus) abundance and distribution were compared at three locations in 

 Penobscot Bay, Maine, from May through September 1976. For the areas in which larvae were found, 

 abundance was low (0.30 larvae/1,000 m 3 ) during the hatching and development period (mid-June through 

 July) when over 98% of the larvae were collected. Hatching initiated when bottom temperatures were as low as 

 10.5°C (Station 2). The abundance of lobster larvae decreased from the mouth to the head of the bay. The 

 absence of larvae at the upper bay station was attributed to low salinity surface waters in the area. Almost all 

 stage 1 larvae (92^o) were found on days when cloud cover was 50% or greater. 



INTRODUCTION 



American lobster, Homarus americanus, larvae were col- 

 lected in Penobscot Bay from May through September 1976 as 

 part of a regional environmental survey related to a proposed 

 power plant site in the upper bay. The principal objective of 

 the study was to estimate the relative abundance and temporal 

 distribution of lobster larvae at three locations in Penobscot 

 Bay (Fig. 1). These stations, distributed over the length of the 

 bay, had similar benthic topography. Furthermore, the lower 

 bay station was selected as an area of relatively high lobster 

 density (as indicated by lobster trap densities). 



The study also provided a data base which would contribute 

 to estimates of power plant entrainment impact. 



MATERIALS AND METHODS 



Lobster larvae were collected with a 1 mm mesh net similar 

 to the type developed and used by Wilder (1953) and Scarratt 

 (1964, 1968, 1973). The net measured 3.7 m x 0.9 m at the 

 mouth, extending 7.6 m to a 0.4 m cod end, and was rigged 

 and buoyed horizontally to expose the upper 0.15 m above 

 the air-sea interface with the remaining 0.85 m underwater. A 

 flowmeter was mounted in the mouth of the net. The net was 

 towed 90 m astern of the boat to avoid towing in the propeller 

 wash. Each tow was 30 min at approximately 1.8 km/h and fil- 

 tered about 2,650 m 3 of water. Generally samples were col- 

 lected 3 or 4 d per week. On sampling dates two or three tows 

 were made at each of two stations on a rotating schedule. All 

 samples were collected during the daylight hours. 



RESULTS 



Total Catch 



A total of 58 lobster larvae was collected in 213 surface net 

 tows (Fig. 2). Only 23 of the tows (11%) contained larvae. All 



ENOBSCOT 

 RIVER 



44° 



VINALHAVEN IS 



Scale in Kilometers 



10 



l 



69° 



32 



-44° 



Environmental Studies Department, Central Maine Power Company, P.O. 

 Box 53. Yarmouth, ME 04096. 



Figure 1. — Sampling stations for lobster larvae, Penobscot Bay, Maine. 



59 



