they could cause high larval fish mortality (Pearcy 1962, Fraser 1969). 

 The present zooplankton program does not include quantitative measurements 

 of medusae and ctenophores. They are captured in plankton tows and 

 could be measured volumetrically. 



Recommendations 



We recommend that the present zooplanton program be continued with 

 zooplankton processing from 0.333-mm-mesh ichthyoplankton samples at the 

 Discharge and Station 5. This will maintain the long time series of 

 data which is important for assessing plant impact compared to natural 

 variability. In addition, we feel the following recommendations should 

 be considered to better assess entrainment impact: 1) more specific 

 identification of tychoplankton and meroplankton; 2) conducting entrain- 

 ment mortality studies on dominant tychoplankton taxa (primarily amphipods) 

 Also, we feel the following additions to the zooplankton program would 

 provide information on factors affecting fish larval abundance: 1) 

 sampling of smaller zooplankton utilized as a food source by larval 

 fish, 2) quantitative measurement of ctenophore and medusae abundance in 

 0.333-mm-mesh samples as potential predators of fish larvae. 



ICHTHYOPLANKTON 

 Natural ichthyoplankton mortality rates are one of the most important 

 controlling factors in adult fish stock abundance (Cushing et al. 1973, 

 Bannister et al. 1974, May 1974, DeAngelis et al. 1977). Additional 

 mortality due to entrainment could affect local fish populations. 

 Because of this potential entrainment impact, ichthyoplankton studies 

 have been conducted at Millstone since 1973. Included in these studies 

 are estimates of ichthyoplankton entrainment density and species composi- 



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