CHITTENDEN: ADULT AMERICAN SHAD IN FRESH WATER 



tured many adults during midsummer between 

 Skinners Falls, N.Y. (348) and Minisink Island, 

 N.J. (266): 538 fish were captured at three sta- 

 tions in mid-July 1961; 237 fish were captured at 

 two stations in mid-July 1962; 30 adults were 

 captured near Milford, Pa. (269) on 7 August 1959, 

 and 13 were captured there on 1 August 1961. 



Upstream Mortality 



There was a large mortality of shad upstream 

 near the spawning grounds about the end of the 

 spawning period. In 1963, I observed many dead 

 fish along the banks or in shallow water on 5 

 July; and a surface gill net set overnight at Mil- 

 ford, Pa. on 22 June captured 15 fish that ap- 

 peared to have been dead for several days. In 

 1964, dead shad first appeared in the East Branch 

 near Hancock about 14 June; on that date, I 

 walked the bank for about 0.8 km and observed 

 26 dead fish within 10 m of the shoreline. I ob- 

 served hundreds of dead shad on 8 July 1964 dur- 

 ing a 19-km float from Matamoras, Pa. (274) to 

 Dingmans Ferry, Pa. (258). I frequently saw dead 

 fish in shallow water during August. 



Shad may die before being completely spent. 

 Some dead fish examined near Hancock had 

 ovaries about a fourth the size of those in fish 

 captured at Lambertville. The ovaries of these 

 dead fish contained many translucent eggs, a 

 criterion (Milner 1874; Brice 1898; Leach 1925) 

 indicating that the fish is ripe. 



shad, 2) 6 darters and 17 shad, 3) 46 shad, and 4) 15 

 shad. Young shad were the first fish to react to 

 rotenone, and the adults probably foraged on dis- 

 tressed and dying young. 



Weight Loss in Fresh Water 



Much weight was lost while the adult shad 

 were in fresh water Fish captured near Hancock 

 had noticeably lost weight by late May, and they 

 became more emaciated the longer they remained 

 in fresh water. Tri-State Survey data obtained 

 10-13 July 1961 from Belvidere, N.J. (197) to Han- 

 cock, N.Y. and 16-17 July 1962 at Minisink Island 

 and Skinners Falls were used to estimate the 

 changed weight-length relationship for each sex. 

 The relationships between total weight and 

 length of these fish were TW = 536.34 + 3.24(FL - 

 407.34) for 296 males and TW = 661.29 + 3.01(FL 

 - 451.18) for 19 females. Valid ranges for linear 

 interpolation were about 265-450 mm for males 

 and 340-475 mm for females. About 66% (males) 

 and 63% (females) of the variation in total weight 

 was associated with variation in length. These 

 regressions explain less variation in total weight 

 than the 80% explained for fish taken at Lam- 

 bertville. 



The average percentages of total weight loss in 

 fresh water were estimated by comparing Lam- 

 bertville and Tri-State Survey regression means 

 at different lengths for each sex (Figure 1). The 



Feeding Behavior in Fresh Water 



Feeding did occur in freshwater, at least near 

 the upstream spawning grounds. The stomachs of 

 most shad captured at Lambertville were empty, 

 but a few contained a slight amount of amorphous 

 material. Stomachs of fish collected upstream 

 from Port Jervis, N.Y. (295) in late May and June 

 frequently contained a few insects. I observed a 

 large mayfly hatch in late May 1964 near Han- 

 cock: hundreds of adult shad were rising to the 

 surface, apparently to feed, and the stomachs of 

 many fish (about 50) captured by angling were 

 packed with mayflies. Similar surface feeding be- 

 havior was observed on several other occasions, 

 although fish were not collected to confirm feed- 

 ing. Many adults captured during the Tri-State 

 Surveys contained recently eaten young shad and 

 shield darters, Percina peltata.For example, four 

 stomachs contained: 1) 2 darters and 9 young 



I 



en 

 (/) 

 O 



z 



UJ 



5 



70 



60 



50 



40 



30 



20 



10 



9 



300 



400 500 



FORK LENGTH (mm) 



600 



FIGURE 1. — Minimum average total weight loss of American 

 shad in fresh water. 



153 



