Lobster Population Dynamics 



Introduction 



The American lobster, Homarus americanus, is 

 the most valuable commercial species in Long 

 Island Sound (LIS) (Blake and Smith 1984). 

 Commercial landings of 1.57 and 2.03 million 

 pounds in 1986 and 1987, respectively, were val- 

 ued in excess of 5 million dollars. The proportion 

 of the total catch landed in New London county, 

 which includes the Millstone Point area, was 27% 

 in both years (CT DEP Marine Fishery Statistics 

 for 1986 and 1987). Because lobsters are an im- 

 portant commercial resource in the Millstone 

 Point area, dynamics of the local lobster popula- 

 tion have been studied to determine if construction 

 and operation of the Millstone Nuclear Power 

 Station (MNPS) have caused changes in the local 

 population beyond those expected from natural 

 variation. 



Potential effects of MNPS operations on the 

 lobster population are entrainment of larvae 

 througli the cooling water systems, impingement 

 of lobsters on the intake traveling screens, thermal 

 effects of the discharge and disruption of lobster 

 habitat caused by routine dredging in the vicinity 

 of the intakes. While mortality due to entrainment 

 and impingement may alter recruitment patterns 

 of lobsters by reducing the survival of lobster 

 larvae and juveniles, the thermal plume may affect 

 the behavior of adults which may result in a de- 

 cline in the local inshore fishery. Dredging may 

 temporarily disrupt lobster habitat (shelters) and 

 thereby displace lobsters from the affected area 

 until sediments stabilize. 



The lobster studies at MNPS were designed to 

 evaluate year-to-year, seasonal, and between sta- 

 tion changes in catch per unit effort and in pop- 

 ulation characteristics such as size frequency, 

 growth rate, sex ratio, female size at sexual ma- 

 turity, characteristics of egg-bearing females and 



lobster movements. Lobster larvae studies were 

 conducted to assess potential impacts of entrain- 

 ment on the larval stage of lobsters. The results 

 of these studies are compared to other studies 

 conducted throughout the range of the American 

 lobster. 



In order to assess potential impacts on the local 

 lobster population associated with 3-unit opera- 

 tion, this report compares data collected during 

 3-unit operation (1986-87) to data collected before 

 Unit 3 became operational. 



Materials and Methods 



A detailed description of methods used to con- 

 duct lobster population studies from 1969 to 1985 

 can be found in NUSCO (1987a). Since 1978, 

 four pot trawls consisting of five double entry 

 wire pots (76x51x30 cm; 2.5 cm mesh) equally 

 spaced along a 50-75 m line bouyed at both ends 

 were used to collect lobsters from May througli 

 October at three stations (.lordan Cove, Intake, 

 and Twotrce; Fig. 1). Pots were individually num- 

 bered beginning in 1984 to determine the variabil- 

 ity in catch among pots, and provided more ac- 

 curate values for catch-per-pot than an average 

 catch-per-pot based on the 20 pots of each sam- 

 pling location. Pots were checked three times 

 each week, rebaited with flounder carcasses and 

 reset in the same area. lobsters > 55 mm 

 carapace length were banded to restrain chelipeds, 

 brought to the lab, and kept in a tank supplied 

 with a continuous flow of seawater. On Fridays, 

 lobsters caught that week were examined and the 

 following data were recorded: sex, presence of 

 eggs (berried), carapace length (CL), crusher claw 

 position, missing claws and molt stage (Aiken 

 1973). Lobsters were then tagged with a serially 

 numbered international orange sphyrion tag 

 (Scarratt and Elson 1965; Scarratt 1970), and re- 

 leased at the site of capture. Recaptured tagged 



LxDbster Population Dynamics 



121 



