Papers in Marine Biology and Oceanography, Suppl. lo vol. .1 of Dccp-Sea Research, pp. 321-330, 



Effect of freshets on Passamaquoddy plankton 



By A. G. Huntsman 

 Department of Zoology, University of Toronto 



Summary— Sudden or heavy discharge into Passamaquoddy Bay, from streams at its head, works out 

 through the 10-mile long Bay and through the S-mile long Head Harbour Passage, its main con- 

 nection with the Bay of Fundy, in less than 10 days, as shown by the salinity of the water. Through 

 the Bay, the outflow is more or less superficial and carries certain elements of the plankton out into 

 the Passage. But, in the latter, strong tidal mixing prevents stratification, although the water is deeper. 

 Under these circumstances, working of the freshet outward has a double effect, first a carrying out 

 of the well-mixed plankton, and then an indraft of deep plankton from without. The latter provides 

 an abundance of planktonic animals in the Passage at all depths. 



Forty years ago, Dr. Johan Hjort, of Norway, brought Henry B. Bigelow and 

 me together in the expedition (Hjort, 1919), which he was organizing for the Biological 

 Board of Canada. It was for me a marvellous introduction to the oceanographic 

 problem in our waters. The methods used were those with which Hjort had been 

 concerned in north European waters and Bigelov/ in waters off the New England 

 and Nova Scotian coasts. In the picture that was developed, the Bay of Fundy, which 

 I was investigating for quite a few years from the Atlantic Biological Station at St. 

 Andrews, New Brunswick, stands out like a sore thumb, in the peculiarity of both its 

 plankton and its hydrography. This is in association with very heavy tidal action. 

 There is also a striking peculiarity in the wealth offish as well as of zooplankton near 

 the surface in the Passamaquoddy region near the mouth of the Bay (Huntsman, 

 1927). When the Passamaquoddy Power Project made the explanation of this 

 condition desirable, Bigelow asked me whether temperature explained this. and. if 

 not, what could the explanation be. This paper gives part of the answer to his question 

 and is offered as a tribute to the stimulating effects of long and most enjoyable associa- 

 tion with him in oceanographic investigations. 



The herring is by far the most abundant fish in the Passamaquoddy region (Fig. 1). 

 Its food consists mainly of Crustacean zooplanktons of the orders Copepoda and 

 Euphausiacea, which are known to the local fishermen as " red feed " and " shrimp " 

 respectively, as seen in herring stomachs. The distribution of such zooplankton both 

 vertically and horizontally determines its availability to the herring, which take these 

 forms individually as silhouetted against the sky when a matter of inches above them. 

 The herring have their own peculiar vertical and horizontal distribution, and vary 

 in condition in accordance with the food available at the place and the time (Battle, 

 et al., 1936). Freshets in the rivers that discharge into Passamaquoddy Bay shift the 

 herring about from one place to another (Huntsman. 1934). as do other factors that 

 bring about movements of the water. Also, mixture over shoals under tidal action of 

 the water of this Bay, which is stratified from river discharge, concentrates the herring 

 and their planktonic food together for effective feeding (Battle, et al.. 1936). There 

 has been need for elucidation of any effects of freshets in shifting the zooplankton 

 from place to place. 



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