MATERIALS AND METHODS 



Ichthyoplankton program 



Ichthyoplankton studies have been conducted at Millstone since 1973. The program consisted of 

 both "offshore" and "entrainment" sampling, and the number of samples collected by year and station is 

 summarized in Appendix II. 



Offshore sampling was initiated in 1973 to provide information for development and interpretation 

 of entrainment impact predictive models (Sissenwine et al. 1973). A bongo sampler with two conical 

 plankton nets of 0.333- and 0.505-mm mesh and weighted with a depressor was towed for 1.5 min. Various 

 combinations of 16 stations (Fig. 2), sampling frequencies (weekly, biweekly, monthly), tow types (surface, 

 sawtooth oblique, bottom), and times (day, night) were used (Battelle 1976) (Table 1). Following an 

 evaluation of the program in 1975 (Vaughan et al. 1976), offshore sampling was redirected towards 

 determining the densities and seasonal succession of the plankton cornmunity. The number of stations 

 was reduced to six, the sampling frequency was changed to monthly, and night sampling was eliminated. 

 llie program was evaluated again in 1978 and the resulting recommendations were implemented in 1979. 

 Sampling was limited to NB because this station provided the most representative samples of the offshore 

 plankton community (NUSCo 1978). The 0.505-mm mesh net on one of the bongos was replaced with 

 a 0.333-mm mesh net; this arrangement provided replication for the latter net. A stepped oblique tow (5 

 min each at surface, bottom, and mid-depth) provided a sample representative of the entire water column. 

 Night sampling was reinstated to investigate the response of ichthyoplankton abundance to the diel period. 

 The program has essentially remained unchanged since 1980, except for the use of a wire angle-indicator 

 to more accurately position the net at the mid and bottom water depths. 



The ichthyoplankton entrainment studies began in 1973 (Table 2). The density of fish eggs and 

 larvae was estimated from three replicate samples collected at the intake (IN) at three depths: surface (in 

 previous reports called INTl), mid (previously INT3) and bottom (previously INT5), at the discharge 

 (FN, previously DISI), and at the quarry cut (QCUT) (Fig. 3). Thirty plankton samples were taken every 

 week (15 day, 15 night) with a 1.0 x 3.6-m conical plankton net with 0.333-rrun mesh netting; the volume 



