the north part of Passamaquoddy Bay. 

 Maximum surface salinity will occur just 

 inside Letite filling gates and will exceed 

 30 parts per thousand. Fresh water is 

 not likely to penetrate below 30 to 50 

 feet, and the bulk of it will be confined 

 to the upper 5 to 15 feet. Flushing time 

 is expected to be increased markedly. 



All saline water will enter the low 

 pool through the turbines and will carry 

 with it the total fresh water discharged 

 into Passamaquoddy Bay. Mean salinity 

 should therefore be lowered. Decreases 

 should not exceed 3 to 4 parts per thou- 

 sand (i.e., salinity not less than 28 parts 

 per thousand) except during peak runoff. 

 Bottom salinities should not drop below 

 28 parts per thousand. Stratification 

 should not be very marked except in the 

 upper reaches of Cobscook Bay. West of 

 Leighton Neck, however, a thin layer, 

 probably not more than 3 feet thick, may 

 be quite brackish and at times drop below 

 20 parts per thousand. Flushing time is 

 expected to be increased substantially. 



In outside areas, significant changes 

 are expected only adjacent to the emptying 

 gates and inside the Head Harbour-BUss 

 Island line. Reduction in salinity is un- 

 likely to exceed a few parts per thousand. 



Oxygen content 



At present, due to vigorous tidal 

 mixing, water in the Quoddy Region is 

 nearly saturated with oxygen. Under pro- 

 posed conditions, mixing will be decreased 

 inside the impoundment and oxygen con- 

 centrations of water in the deep basins 

 of Passamaquoddy and Cobscook Bays 

 may be reduced. Rates of water renewal, 

 and hence rates of oxygen supply to the 

 deep water within the basins, will be 

 minimal during periods of maximum 

 fresh -water discharge into the Quoddy 

 Region. However, oxygen concentrations 

 are unlikely to fall below 50 percent 

 saturation. 



BIOLOGICAL EFFECTS OF 

 IMPOUNDMENT 



In the biological study, particular 

 attention was given to herring, the most 

 important commercial species in the 

 Quoddy Region. This study included catch 

 statistics, identification and origin of 

 populations, food and feeding habits, be- 



havior, and migrations. Catch statistics 

 and published info rnnati on on other species 

 were evaluated. Anticipated changes in 

 oceanographic conditions were considered 

 in predicting changes that may take place 

 in all commercially important species 

 as a result of the proposed dams. 



Herring 



Herring stocks in the Quoddy Region 

 are produced outside, probably in south- 

 west Nova Scotia waters. Since environ- 

 mental changes are anticipated only inside 

 the bays and immediately outside the 

 proposed dams, it is extremely unlikely 

 that the abundance of herring will be 

 affected. Most of the plankton that makes 

 up the food of herring is also produced 

 outside the Quoddy Region, and no nnajor 

 change in its abundance and distribution 

 is anticipated. 



Tagging experiments indicate that 

 herring move freely in and out of Pas- 

 samaquoddy and Cobscook Bays during 

 the fishing season with some tendency to 

 concentrate at the head of Passamaquoddy 

 Bay. It is not expected that the installation 

 and operation of the proposed dams will 

 affect the movement of herring to the 

 Quoddy Region, nor should the distribu- 

 tion of fish, except in the bays and im- 

 mediately outside the dams, be affected. 

 It has been predicted, that significant 

 changes are unlikely in oceanographic 

 conditions outside the Quoddy Region be- 

 yond the Head Harbour-Bliss Island line. 

 Herring should therefore arrive outside 

 the passages as before. It has been 

 concluded from behavior studies that 

 herring will swinn against a current only 

 when they can see fixed objects such as 

 the bottom. Most of the year, herring 

 are in the upper-water layers and, hence, 

 probably will be transported passively 

 in the current. For most of the period 

 when they are open, the current through 

 the filling gates and for some distance 

 outside will exceed 5 feet per second. 

 This velocity exceeds the maximum 

 swimming speed of herring and the fish 

 will be carried into the high pool. Since 

 the filling gates are open only for about 

 6 hours each day, movements of fish 

 into Passamaquoddy Bay will be delayed. 

 This short period during which the gates 

 are open will affect the rate at which 

 herring accumulate inside Passamaquoddy 

 Bay. However, recaptures fronn tagging 



27 



