WEIGHT LOSS, MORTALITY, FEEDING, AND DURATION OF 



RESIDENCE OF ADULT AMERICAN SHAD, 



ALOSA SAPIDISSIMA, IN FRESH WATERS 



Mark E. Chittenden, Jr.^ 



ABSTRACT 



Linear regression equations are given for each sex for the regressions of total weight, somatic weight, 

 and gonad weight on length prior to spawning, and for total weight on length after prolonged stay in 

 fresh water 



Most shad began to return seaward by late June and probably had spent a maximum of about 2 mo 

 in fresh water Many fish, however, remained near the spawning grounds well into summer; and 

 many died near the spawning grounds, probably from starvation. Opportunistic feeding oc- 

 curred on "planktonic" items, but adult shad do not regularly obtain energy sufficient to maintain 

 their weight in fresh water. Weight loss was related to sex and increased with increasing size. Mean 

 length males and females averaged 45 and ^T7c total weight loss, respectively. Daily somatic 

 weight loss was at least 5.75 g for males of average size and 12.47 g for females. 



The anadromous American shad, Alosa sapidls- 

 sima, an important commercial and sport fish, 

 ranges widely on the Atlantic and Pacific coasts of 

 North America. There is much literature on this 

 fish, but little of it pertains to adults in fresh wa- 

 ter, except for aspects of their spawning and popu- 

 lation dynamics. In the course of other studies on 

 the Delaware River from 1960 to 1968, I made 

 many opportunistic observations on weight loss, 

 mortality, feeding behavior, and duration of resi- 

 dence of adult shad on their spawning grounds in 

 fi'esh water. This paper summarizes those obser- 

 vations and presents data on total-fork length 

 conversion, regressions of total weight, somatic 

 weight and gonad weight on length prior to 

 spawning, and regressions of total weight on 

 length after spawning. 



MATERIALS AND METHODS 



Adult shad were collected during their spawn- 

 ing runs at Lambertville, N.J., 22.5 km above 

 tidal water (but far downstream of the present- 

 day spawning grounds) using a 76-mm stretch- 

 mesh, 107 m long and 3.6 m deep haul seine that 

 was paid out from a boat and landed about 400 m 

 downstream. Sampling occurred at 3- or 4-day in- 

 tervals from 5 April to 19 May 1963, from 20 



'Based on part of a dissertation submitted in partial fulfill- 

 ment of the requirements for a Ph.D. degree, Rutgers Univer- 

 sity, New Brunswick, N.J. 



^Department of Wildlife and Fisheries Sciences, Texas A&M 

 University, College Station, TX 77840. 



March to 18 May 1964, from 26 March to 7 May 

 1965, and from 27 March to 19 May 1966. Data for 

 the period 1959-62 were obtained from rotenone 

 surveys (hereinafter referred to as the Tri-State 

 Surveys) during July and August by the States of 

 New Jersey, New York, and Pennsylvania in 

 cooperation with the U.S. Fish and Wildlife 

 Service. 



I examined grossly the stomach contents of 

 many adults captured during the Tri-State Sur- 

 veys in mid-July 1961, most of the 526 fish col- 

 lected at Lambertville and many fish captured on 

 the spawning grounds after 1962. 



Length and total weight were determined on 

 most fish in 1961 and 1962 and on all fish thereaf- 

 ter. Gonad weight was measured after 1962. 

 Length, always taken in inches, was measured as 

 fork length during 1961 and 1962 and as total 

 length thereafter. To develop conversion factors, 

 both measurements were taken on 490 adults col- 

 lected at Lambertville during 1963 and 1964 and 

 on 100 young captured in summer 1966. Total 

 weight was measured in pounds (to the closest 0.1 

 lb) during 1961-63 but in grams thereafter Gonad 

 weights were always taken in grams (to the 

 closest 0.1 g). All measurements were converted 

 to grams, millimeters, and fork lengths for pre- 

 sentation herein. 



Regression analyses and related statistics were 

 calculated using computer program BMD-03R 

 (Dixon 1967). All regressions presented herein 

 were significant at a = 0.005. The coefficient of 



Manuscript accepted July 1975. 



FISHERY BULLETIN: VOL. 74, NO. 1, 1976. 



151 



