1941). Subadults enter the river in the spring and 

 summer, often in enough abundance to support a 

 sport fishery in Connecticut (Moss 1960). No striped 

 bass were passed upstream in the two Holyoke Dam 

 fish lifts located at river km 140 from the initial 

 operation in 1955 until 1979, when 103 were lifted. 

 Each year from 1980 to 1984, 110-510 striped bass 

 have used the fish lifts (O'Leary 1985). In 1982, 

 83.5% of the fish were age II; 16.5% were age III; 

 and none were sexually mature (Warner 1983). 



Because the striped bass did not migrate into the 

 river to spawn, they probably entered to feed. The 

 food of striped bass has been extensively studied, 

 but there is no published report about the food of 

 young fish that gather below a hydroelectric dam. 

 We studied the food of the striped bass that were 

 lifted at Holyoke Dam in 1982. 



Methods 



The stomachs of fish were removed and frozen, and 

 the contents were examined in the laboratory with 

 a dissecting microscope Stomach contents were 

 classified as small forage fish, body parts of large 

 fish (i.e., fish larger than the striped bass could eat 

 whole), insects, plant material, and empty. Body 

 parts were the scales, bones, flesh, and ovaries of 

 adult alosids (i.e, American shad, Alosa sapidissima, 

 and blueback herring, A. aestivalis), and pieces of 

 adult sea lamprey, Petromyzon marinus. The body 

 parts originated from the following sources: fish that 

 were injured or killed while attempting to pass the 

 dam or to use the fish lifts, American shad that were 

 discarded below the dam by sport fishermen, or 

 turbine-induced injuries or mortalities of fish that 

 passed through the hydropower turbine at the dam 

 (Bell and Kynard 1985). 



When possible, small forage fish were identified 

 to species and measured for total length. Insects 

 were identified to order. We compared the frequency 

 of occurrence of the four foods eaten by striped bass 

 that were lifted early (25 May-14 June), when average 

 daily passage of adult alosids in the lifts was about 

 28,000, with the foods eaten by striped bass that 

 were lifted late (after 21 June), when the average 

 daily lift of alosids was about 3,000. 



Results and Discussion 



We examined 78 stomachs of striped bass— 65 

 (83%) contained food. Sixty-nine percent of the 

 stomachs with food contained the body parts of large 

 fish (Fig. la). Of the stomachs with the body parts 

 of large fish, 93% contained the scales of adult 



alosids, with many containing over 20 scales; 16% 

 contained the body parts of adult sea lampreys. 



Small forage fish were second in the frequency of 

 occurrence at 61%, and insects were third at 21% 

 (Fig. la). Elvers of the American eel, Anguilla 

 rostrata, (96 mm mean total length, range: 70-125 

 mm, N = 24) dominated the small forage fish 

 category, occurring in 58% of the stomachs that con- 

 tained forage fish. Elvers, migrating upstream from 

 the ocean, may be delayed and concentrated by 

 Holyoke Dam; perhaps striped bass follow the elvers 

 upriver— both species occur in the fish lifts at the 

 same time Cyprinids were identified in six of the 

 stomachs with forage fish. All had a 2,4-4,2 tooth 

 formula and were probably spottail shiners, Notropis 

 hudsonius, a commonly observed minnow. Insects in 

 stomachs were mayfly nymphs, order Ephemerop- 

 tera, but only one or two mayflys were found in any 

 stomach. 



There was a significant difference in the frequency 

 of the four food groups in fish collected early and 

 late (x 2 = 12.6, P < 0.01). Fish parts dominated the 

 stomach contents of early-lifted fish, whereas in late- 

 lifted fish 54% contained parts of large fish, but 77% 

 contained small forage fish (Fig. lb). Fifteen per- 

 cent of the stomachs of early-lifted fish were empty, 



UJ 



o 



a: 100 



UJ 



a. 



FISH FORAGE 



PARTS 



FISH 



INSECTS PLANTS 



Figure 1— Percent occurrence of the four major foods in the 

 stomachs of striped bass passed by the Holyoke fish lifts a) in all 

 of 1982 and b) in fish sampled early (25 May-14 June, N = 39) and 

 late (after 21 June, N = 26) 1982. 



221 



