An entrainment mortality study was conducted in 1983 (NUSCo 1984). Samples of entrained winter 

 flounder larvae were collected downstream from the MNPS discharges with a 0.5-m diameter, 1-m long, 

 333-jim mesh plankton net. Dead larvae were removed from the sample and counted. Live larvae were 

 held in flow-through chambers in effluent water. Holding time was 2 or 4 h to simulate retention in the 

 quarry with three or two units in operation, respectively. Following effluent holding, chambers were 

 moved to ambient flow-through water and observed daily for latent mortality over a 96-h period. 



The thermal tolerance of larval winter flounder was examined (NUSCo 1975). Larvae were grouped 

 as pre-metamorphosis ( < 5 mm) and metamorphosing ( ^ 5 mm). Larvae were exposed to a AT of 13 °C 

 (acclimation temperature of 8 °C) for 1 to 9 h and survival was monitored. The critical thermal maximum 

 for the two groups was also examined, where larvae held at 8 °C were exposed to an increase of 1 °C per 

 min until death. The temperature at which complete mortality occurred was the estimated critical thermal 

 maximum of larval winter flounder. 



Impact assessment 



A population dynamics model was developed under the direction of Dr. Saul Saila of the University 

 of Rhode Island for impact assessment during the projected life of the plant and for a recovery period 

 following decommissioning. This model incorporates hydrodynamic, concentration, and population 

 submodels in a simulation of the effects of MNPS operations on the Niantic River stock of winter flounder. 

 Data from both NU studies and the scientific literature were used in the model. The methods and 

 procedures used in its development and may be found in progress reports to NUSCo by Sissenwine et al. 

 (1973, 1974, 1975) and Vaughan et al. (1976). Aspects of the model were published by Hess et al. (1975). 

 The final form of the model presented by Saila (1976) was summarized and used with updated information 

 in the Environmental Report for MNPS Unit 3 (NUSCo 1983c). A brief summary of the results and 

 conclusions of the latest model application will be given in this report. 



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