LENGTH N CENTIMETERS 



Figure 5. --Size distribution of scallops in the commercial 

 fishery. 



EXPECTED CHANGES 



The major changes in the environ- 

 ment anticipated from the construction 

 of dams will be inside Passamaquoddy 

 and Cobscook Bays and immediately 

 outside the dams. They include changes 

 in the rate of water exchange and there- 

 fore will be of great significance to the 

 native scallops. These relatively sed- 

 entary animals must adapt to their 

 environment or perish. Changes in 

 scallop distributions must be forecast 

 with a knowledge of probable oceano- 

 graphic changes. 



Oceanographic Effects 



Forty-three oceanographic cruises, 

 under the auspices of the International 

 Passamaquoddy Fisheries Board, cov- 

 ered a network of stations in the 

 Quoddy Region during 1957 and 1958 

 and yielded pertinent information con- 

 cerning general patterns of water 

 levels, currents, temperatures, salini- 

 ties, etc. The following statements 

 are based upon this information. The 

 mean water level in the high pool will 

 be raised about 6 feet; that of the low 

 pool will be lowered about 5 feet. The 

 mean tidal range, now approximately 

 20 feet, will be reduced in both high 

 and low pools, to 4 feet and 8 feet, 

 respectively. 



Since the emptying and filling gates 

 will be closed during most of each 



tidal cycle, current patterns in both 

 pools will be greatly changed. When 

 the gates are open, velocities in most 

 areas should be only slightly lower 

 than at present, but the rate of filling 

 will, of course, be much slower. The 

 flushing time, i.e., the average length 

 of time required to remove 1 -day's 

 contribution of river water, is now 

 from 8 to 20 days, varying with the 

 amount of river discharge. Flushing 

 time in the high pool will be doubled 

 by dam construction. In the low pool, 

 flushing time will be reduced somewhat. 



Because of the 50 -percent reduction 

 in water exchange in the high pool, 

 the accompanying decrease in vertical 

 mixing will result in greater seasonal 

 water -temperature variations, par- 

 ticularly at the surface. The majcimum 

 surface temperature in summer may 

 increase from 54° to 68° F. Summer 

 water temperatures throughout the low 

 pool should increase to comparable 

 levels. Partial ice cover may be ex- 

 pected in the winter. 



Mean surface salinities will be 20 

 to 30 parts per thousand in the pools 

 as compared with the present 30 to 

 33 parts per thousand, but bottom 

 salinities are likely to change little. 



Effects of Changes on Sea Scallops 



The abundance of the sea scallop 

 has fluctuated widely and will continue 

 to fluctuate with or without impound- 

 ment. This species would be profoundly 

 affected, however, by construction of 

 the proposed dams. 



It is expected that impoundment will 

 increase scallop landings in the Quoddy 

 Region. It was concluded by Dickie 

 (1955) that fluctuations in the market- 

 able scallop supply can be largely 

 explained by fluctuations in water tem- 

 perature. Low temperatures prolong 

 the pelagic stages when the scallop is 

 most vulnerable to plankton feeders 

 and to wide dispersal by water cur- 

 rents. High temperatures, conversely, 

 are favorable to larval survival, as 

 are low rates of water exchange. Studies 

 have indicated that the number of larvae 

 which settle on their parent beds is 



