ECONOMIC IMPORTANCE 



The larvae of Trichoptera, which live on the bottom of various water 

 bodies, are one of the food sources of bottom-feeding fish; they are a 

 principal, supplementary or accidental part of their food. Certain 

 predatory fish (especially their young) also feed sometimes on Trichoptera. 

 The most useful food are the large species which appear in great numbers. 

 In the open littoral of lakes, these are various species of Limnophilinae 

 and Apataniinae, especially species of Potamophylax, Chaetopteryx, 

 Anabolia, Dicosmoecus and Apatania. In plant thickets, these are 

 species of Phryganea, Agrypnia, Nemotaulius and Grammo- 

 taulius, and also numerous small species of Leptoceridae and Hydropti- 

 lidae, which inhabit plant thickets of lakes, rivers, reservoirs, ponds and 

 water bodies of river floodlands. 



We give herewith some data on the role of Trichoptera as food of some 

 benthon-feeding fishes of the USSR.* 



The larvae of Hydropsychidae, which occur in large numbers on the 

 bottom of large rivers in the plains, are an important part of the diet of 

 Acipenseridae. In the Volga, Acipenser ruthenus ruthenus begins to 

 feed on Trichoptera when it reaches a length of 4— 8 cmj in its later life, it feeds 

 on larvae of Hy d r op sy c h e sp. sp. (mainly H. o r nat ul a). According to 

 observations made in 1934 in spawning grounds in the middle Volga, in the 

 area of Kazan, larvae of Hydro psyche are the largest invertebrates in 

 the diet of Acipenser ruthenus. In the Kuibyshev region (according 

 to data from 1939) in some places, these larvae constitute up to 50% of the 

 food of this fish; in the stomach of 1 specimen, 144—350 larvae of 

 Hydropsy che were found (Bening, 1912:7— 11; Aristovskaya, 1935a:147; 

 1935b:47-49; Pankratova, 1948:610—613). The same applies to the Siberian 

 sterlet (A c i p e n s e r ruthenus ruthenus natio m a r s i gl i i). To judge 

 from the frequency of occurrence of Trichoptera in the stomach of sterlets in the 

 upper and middle Ob, and the avidity with which they are eaten by sterlets, 

 these insects take first place in the diet of this fish (Solomonovskaya, 

 1952:69—70). In the Irtysh, the food of this fish consists mainly of 

 Tendipedidae, mayflies and species of Hydropsy che and Brachy- 

 centrus subnubilus; in the lower reaches of the river, during the 

 summer, an average of 52 specimens was found in the stomachs of sterlets 

 in some localities. Trichoptera constitute about 12% of the food of sterlets 

 in early August and 28.8% in mid-August (Chalikov, 1928:16—17; Revnivykh, 

 1937:261-267; Sal'dau, 1949:202-203). The food of the Siberian sterlet 

 includes Trichoptera all along the Yenisei; 194 specimens are sometimes 

 found in the stomach of this fish (isachenko,** 1916:5—6; Romanova, 1948:152). 

 1 75 Trichoptera were also found in the stomachs of Acipenser baeri 

 in the Ob and Yenisei (Solomonovskaya, 1952:66—68). In the Irtysh, 

 Trichoptera occur constantly in the summer diet of the sturgeon; this fish 

 prefers larvae of B r a c hy c e nt r u s subnubilus (Chalikov, 1930:1— 2; 



The literature on the feeding of fish is large; we are using here only Russian works, selecting only works 



in which the role of Trichoptera as food is well described. 



Isachenko (1916) apparently was mistaken when he described the larvae of Phryganeidae as the predominant 



food of sterlets in the Yenisei. When Hydropsychidae are abundant in the Yenisei, there are no larvae of 



Phryganeidae in the river, as shown by the observations of P.L. Pirozhnikova and others (Lepneva, 1948b: 



71-86). 



164 



