Suitable lobster habitats in the vicinity of MNPS (6.5 km ! ) are 

 characterized by rocky outcrops interspersed with patches of hard 

 sand. 



Beginning in January 1975, lobsters were sampled from natural 

 and artificial habitats using scuba, from fish trawls, and from im- 

 pingement studies at Units 1 and 2 intake structures. In September, 

 20 double entry wooden lobster pots (91 x 51 x 30 cm; 3-5 cm lath 

 space) were set at each of three stations (Fig. 1): Jordan Cove, (east 

 of Millstone Point; 500 m from discharge) Intake, (along the 

 western shore of Millstone Point near the power plant intake struc- 

 tures; 600 m from discharge) and Twotree ( 1 ,600 m offshore, near 

 Twotree Island). Year round sampling continued until November 

 1978. Subsequently, the sampling period was reduced to the 

 months of high catch, May-October. In August 1978, half of the 

 wood pots (10 per station) were replaced with commercial vinyl 

 coated wire pots (76 x 51 x 30 cm; 2.5 cnr mesh). 



Throughout the study, pots were hauled on Monday, Wednes- 

 day, and Friday, weather permitting. At each station, lobsters were 

 removed from traps, claws restrained with rubber bands, and pots 

 rebaited. Prior to 1979, an assortment of locally caught fish was 

 used as bait; subsequently, to standardize the effect of bait on 

 catchability, flounder carcasses were used exclusively. Carapace 

 length (CL), sex, presence of eggs (berried), missing claws, and 

 molt stage were reported for each lobster captured. 



Molt stage was determined using criteria established by Aiken 

 (1973). Recaptured tagged lobsters, severely injured individuals, 

 and those < 55 mm CL were returned to the water untagged. All 

 others were returned to the laboratory and maintained in con- 

 tinuous flow saltwater tanks, segregated by station and pot type. 

 Each Friday, all lobsters were tagged with a numbered interna- 

 tional orange sphyrion tag (Scarratt and Elson 1965; Cooper 1970; 

 Scarratt 1970), and returned to the site of capture. 



From 1979 to 1981, during each sampling trip, surface and bot- 

 tom water temperatures and salinities were recorded at each station 

 with a Beckman salinometer. 



RESULTS AND DISCUSSION 



Physical Measurements 



Water temperature and salinity were measured from May 

 through October (1979-81). Bottom temperatures ranged from 7°C 

 in early May to 22°C in summer, and were up to 2.TC lower than 

 corresponding surface temperatures (Table 1). Temperatures (sur- 

 face and bottom) at Jordan Cove and Intake (4-6 m in depth) were 

 similar to each other, but slightly warmer than at Twotree (12 m). 

 At present (two unit operation), the thermal plume does not reach 

 the bottom sediments at any station. 



Salinity was constant between stations and between surface and 

 bottom; values ranged from 29.1 to 32%o. Due to the spring 

 freshwater runoff, salinities were 1.2%o lower in May and June 

 than in the rest of the sampling period. 



Abundance and Catch Per Unit Effort 



A total of 27,019 lobsters were collected in the study area from 

 1975 to 1981 (Table 2). The increased catches from 1978 to 1981 

 were the result of the addition of wire pots into the sampling pro- 

 gram (Table 3). 



Catch per unit effort (CPUE) for wood pots was similar in 

 magnitude from 1976 to 1981, but peaked at different times within 

 each year (Fig. 2). At temperatures > 10°C lobster catch began to 



Table 1. — Mean monthly surface (S) and bottom (B) water 

 temperature (°C) at each station (1979-81). 





Jordan Cove 

 S B 



Intake 

 S B 



Twotree 



Month 



S 



B 









979 









May 



10.3 



9.5 



10.5 



9.5 



9.9 



9.2 



June 



15.0 



14.2 



15.2 



14.4 



14.5 



13.9 



July 



19.9 



17.8 



19.2 



18.3 



18.3 



17.7 



August 



20.6 



19.6 



20.2 



19.8 



19.7 



19.2 



September 



19.8 



19.2 



19.8 



19.3 



19.2 



18.9 



October 



17.0 



15.9 



15.8 

 980 



15.7 



15.6 



15.5 



May 



10.8 



9.8 



10.6 



9.7 



9.9 



9.4 



June 



14.8 



14.1 



14.7 



14.3 



14.4 



13.9 



July 



19.6 



17.8 



19.2 



18.3 



18.4 



17.7 



August 



21.2 



19.9 



21.0 



20.1 



20.2 



19.7 



September 



20.7 



19.8 



20.5 



20.0 



20.1 



19.9 



October 



16.1 



15.9 



16.1 

 1981 



16.0 



16.2 



16.1 



May 



9.8 



9.0 



9.6 



9.1 



9.3 



8.8 



June 



16.0 



14.1 



15.3 



14.6 



14.6 



14.0 



July 



19.9 



19.0 



19.8 



19.2 



19.3 



18.6 



August 



21.8 



20.5 



21.2 



20.7 



20.6 



20.3 



September 



20.4 



19.5 



19.8 



19.6 



19.7 



19.4 



October 



15.2 



14.6 



14.7 



14.5 



14.2 



14.1 



Table 2. — Summary of lobster mark-recapture program, 1975 

 through 1981. 



Sampbng period 



Number 



Number 



Recaptures 



Months 



Year 



caught 



lagged 



N 



% 



Sept. -Dec. 



1975 



1,501 



1.501 



97 



6.5 



Jan. -Dec. 



1976 



3,498 



2,962 



341 



11.5 



Jan. -Dec. 



1977 



3,242 



2,876 



240 



8.3 



Jan-Dec. 



'1978 



4,371 



3,199 



378 



11.8 



May-Oct. 



1979 



5,031 



3,732 



674 



18.1 



May-Oct. 



1980 



4,266 



3,634 



485 



13.3 



May-Oct. 



1981 



5,110 



4,246 



571 



13.4 



Total 





27,019 



22,150 



2,786 



12.6 



Wire pots added to sampling scheme in August. 



increase at Jordan Cove and Intake and peaked between 15° and 

 20°C (Fig. 3). However, at Twotree (our deep station), the catch 

 was highest between 7° and 15°C. Since catches at Twotree decreas- 

 ed concurrently with increases at Jordan Cove and Intake, the 

 movement of lobsters from Twotree into our inshore stations may 

 have been the cause of the increased inshore catch; however, 

 preliminary data on interstation movements do not support this 

 hypothesis (NUSCo 1979, 1980)'. The relationship between catch 

 and water temperature has been reported by other researchers 

 (McLesse and Wilder 1958; Dow 1966, 1969, 1976; Flowers and 

 Saila 1972). 



Results from the 1978-80 sampling period indicated that wire 

 pots caught significantly more lobsters than did wood pots (Table 

 3); however, this was not the case in 1981. The wire pots used in 



■NUSCo. 1979. Lobster population estimates. In The annual report on 

 ecological and hydrographic studies at the Millstone Nuclear Power Station, p. 

 E1-E27. Northeast Utilities Service Co., Waterford, Conn. 

 NUSCo. 1980. Lobster population dynamics. In The annual report on ecological 

 and hydrographic studies at the Millstone Nuclear Power Station, p. 195-231. 

 Northeast Utilities Service Co., Waterford, Conn. 



