CAUSES OF FLUCTUATIONS IN ABUNDANCE 

 OF CONNECTICUT RIVER SHAD 



By Reynold A. Fredin, Fishery Research Biologist 



This study of fluctuations in abundance of the 

 Atlantic shad (Alosa sapidissima) in the Con- 

 necticut River is part of a 6-year, coastwise study 

 of the species sponsored by the Atlantic States 

 Marine Fisheries Commission. The Uaited States 

 Fish and Wildlife Service, with the cooperation of 

 the various State agencies along the Atlantic 

 coast, has undertaken to determine the factors 

 affecting the abundance of shad and to recommend 

 measures for restoring the species to its former 

 abundance. 



The present commercial shad fishery on the 

 Connecticut River is below Enfield Dam, in Con- 

 necticut, 60 miles from the mouth of the river, 

 which rises in Quebec, Canada, and flows south- 

 ward nearly 400 miles into Long Island Sound, at 

 Saybrook, Conn. An angler's fishery is at the 

 dam. Shad ascend the river as far as Holyoke, 

 Mass., about 85 miles from its mouth, where a 

 dam prevents further upstream movement. What 

 effect the fishway now being constructed at the 

 Holyoke Dam will have on future shad runs is 

 not known. 



Nearly all of the shad fishermen on the Connect- 

 icut River are gainfully employed in other occupa- 

 tions, but take leave from their jobs each spring 

 during the shad season. After the legal season 

 opens, a few fishermen start fishing at the mouth of 

 the river to determine when the shad enter the river. 

 Shortly after the first shad are taken, other fisher- 

 men at the mouth of the river begin operations 

 and are in turn followed by those farther up the 

 river. Fishing continues until the run dwindles. 

 Since the fishermen take time off from their jobs 

 for the sole purpose of fishing, and since the 

 season is short, lasting from 6 to 8 weeks, the 

 fishing effort remains fairly uniform throughout a 

 given season. Logbooks, maintained by a few 

 fishermen for a period of several years, show that 

 once a fisherman commences fishing in a given 

 season he fishes consistently until he stops for 

 the year. Drift gill nets and haul seines are the 

 types of commercial gear used throughout the 



259310—64 



fishery, except for one pound net located at the 

 mouth of the river at the time of this study. 



This paper presents information on some of the 

 factors affecting the abundance of shad in the 

 Connecticut River, such as water temperature, 

 stream flow, pollution, and escapements, and on 

 the basis of catch and effort data for a period of 

 17 years attempts to relate the fluctuations in 

 abundance of the species to these factors. 



Since accurate catch and effort records are pre- 

 requisite to determining fluctuations in abundance 

 of shad or of any other species of fish taken com- 

 mercially, and since a scientific interpretation of 

 these fluctuations should precede any fishery- 

 management recommendations, special recogni- 

 tion is due the Connecticut State Board of Fisheries 

 and Game for having obtained statistics on the 

 Connecticut River shad fishery for a number of 

 years. I wish to thank Dr. R. P. Hunter, Lyle 

 Thorpe, Douglas D. Moss, and other members of 

 the Connecticut State Board of Fisheries and 

 Game, for permission to use shad-fishery statistics 

 and scale data from their official files; for assistance 

 in conducting the field work; and for helpful 

 suggestions pertinent to the investigation. 



An expression of appreciation is due to members 

 of the staff of the United States Fishery Labora- 

 tory, Beaufort, N. C, who helped in the field 

 work and offered suggestions throughout this 

 study; to Dr. D. B. DeLury, Ontario Research 

 Foundation; Dr. R. J. Monroe, North Carolina 

 State College; Dr. M. B. Schaefer, Inter-American 

 Tropical Tuna Commission; and Elizabeth Vaughn 

 for reviewing this paper; and to the shad fishermen 

 of the Connecticut River without whose coopera- 

 tion during tagging studies and in turning over 

 their records for review, this work could not 

 have been completed. 



STATISTICS OF THE FISHERY, 1890-1951 



Although commercial fishermen on the Connect- 

 icut River have reported their annual catches of 

 shad to the State of Connecticut since 1890, and 



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