Fish Ecology Studies 



Introduction 



Fish are an important marine resource in Con- 

 necticut and millions of dollars in annual revenues 

 are generated by the fishing industry in Long Is- 

 land Sound (LIS) (Sampson 1981; Blake and 

 Smith 1984). Commercially and recreationally 

 important fishes are abundant in the area around 

 Millstone Nuclear Power Station (MNPS) along 

 with important forage species that contribute to 

 ecosystem productivity. Some vSpecies inhabit the 

 area seasonally for feeding, spawning, or nursery 

 activities while others are year-round residents. 



The operation of MNPS could affect fish as- 

 semblages in the area by increasing mortality rates 

 and altering spatial distribution. Adult and juve- 

 nile fish may be removed from populations by 

 impingement on the intake screens. Fish eggs 

 and larvae may be removed through entrainment 

 with the condenser cooling water. The effects of 

 uicreased mortality rates on the abundance of 

 these populations can differ depending upon the 

 size, life span, and age structure of the affected 

 population and on the existence of compensatory 

 mechanisms. Spatial distributions of local fish 

 populations may change in response to alterations 

 in the thermal or chemical regime of the effluent 

 or modifications to the physical habitat. Water 

 temperature increases can attract or exclude fish 

 from areas affected by the thermal plume of 

 MNPS. Physical alterations caused by bottom 

 scouring or dredging could also affect the spatial 

 distribution of fish. 



To determine if the operation of MNPS has 

 impacted the local fish assemblages, monitoring 

 studies have been established. The objectives of 

 these monitoring programs are: 



1. Describe the occurrence and abundance of 

 fish in the Millstone area. 



Identify spatial and temporal patterns of fish 

 assemblages and establish the extent and di- 

 rection of natural changes in these assem- 

 blages. 



Evaluate whether observed changes are the 

 result of MNPS operation, and if so, the 

 significance of these changes, with particular 

 emphasis on the period since Unit 3 began 

 operating. 



To meet these objectives, four sampling pro- 

 grams have been established to collect data on 

 the available life history stages of those fishes 

 susceptible to impact. These programs are the 

 demersal trawl; shore-zone seine; ichthyoplank- 

 ton, including entrainment sampling; and 

 impingement. In this report, the life history and 

 population characteristics of potentially impacted 

 species are presented and evaluated to determine 

 if MNPS has had any detrimental effects on them. 

 Although Unit 3 did not start producing com- 

 mercial power until April 23, 1986, variable num- 

 bers of condenser cooling water pumps were op- 

 erated starting in November 1985. For species 

 potentially impacted by entrainment or 

 impingement, all of 1986 will be considered as a 

 three-unit operational period. 



The Fish Ecology section of the two-unit sum- 

 mary report (NUSCO 1987b) emphasized time- 

 series analyses to describe the natural fluctuations 

 of potentially impacted species. These time-series 

 models represent a baseline that can be used with 

 intervention analysis (Madenjian et al. 1986) to 

 assess three-unit operations. But at this time, 

 with less than 2 years of data since the start-up 

 of Unit 3, there are insufficient data to apply 

 intervention analyses. Therefore, in this report 

 more conventional indices of abundance will be 

 used for assessment. 



Fish Ecology Studies 255 



