FISHERY BULLETIN: VOL. 80, NO. 4 



Halver 1961). Brook trout fingerlings (initial 

 mean weight = 1.6 g) fed 14% glucose, galactose, 

 or fructose over a 20-wk period had better growth 

 rates when fed 14% glucose or fructose (McCart- 

 ney 1971). Rainbow trout fingerlings had better 

 growth rate, feed conversion, and protein effi- 

 ciency when fed 30% glucose concentrations com- 

 pared with 30% raw corn starch or 15% glucose 

 plus 15% cellulose (Bergot 1979a). Dietary glu- 

 cose concentrations as high as 30% doubled 

 plasma glucose 6 h after the first meal, while 

 normal plasma glucose concentrations were at- 

 tained 24 h later (Bergot 1979b). Channel catfish 

 fingerlings can utilize 2.25 g of dextrin in place 

 of 1 g of lipid for growth equally well within die- 

 tary lipid concentrations of 5 to 12.5% and digest- 

 ible carbohydrate concentrations of 5.6 to 22.5% 

 (Garling and Wilson 1977). 



Dietary fiber is not required by fishes and is 

 considered to be a nonnutrient bulk component 

 in fish diets. According to Leary and Lovell 

 (1975), dietary cellulose in excessive amounts 

 probably decreases absorption of essential nutri- 

 ents by physical obstruction of enzymes and in- 

 creased rate of passage through the digestive 

 system. Obstruction of enzyme activity may re- 

 sult from ingested fiber chelating metal ions 

 serving as cofactors of enzymes. Dietary cellu- 

 lose concentrations as high as 8% did not inhibit 

 growth of channel catfish, whereas 14% dietary 

 cellulose depressed growth. No similar studies 

 have been conducted with salmonids or other fish 

 species to evaluate maximum tolerable, dietary 

 fiber concentrations. 



Cellulase activity in stomachs of several fish 

 species and intestinal portions of stomachless 

 Cyprinidae was positively correlated with 

 amount of detritus consumed (Prejs and Blasz- 

 czyk 1977). Microflora ingested along withdetri- 

 tal material is probably responsible for the cellu- 

 lase activity in fish; however, further research 

 should examine sources of cellulase activity, espe- 

 cially in herbivorous species. 



VITAMINS 



Qualitative vitamin requirements of fishes 

 (National Research Council 1973, 1977) and their 

 biochemical and physiological functions are gen- 

 erally similar to requirements and functions 

 demonstrated for terrestrial animals. Early 

 qualitative vitamin requirement studies of fishes 

 usually consisted of long-term feeding trials 

 (e.g., 14 to 24 wk) in which laboratory cultured 



salmonids were fed a positive control diet (i.e., 

 assumed to be nutritionally complete) or that 

 same diet omitting one of several vitamins 

 (McLaren et al. 1947; Halver and Coates 1957; 

 Coates and Halver 1958). Growth, survival, be- 

 havior, internal organ appearance, blood physi- 

 ology, and histopathology were often examined 

 to describe deficiency symptoms. Also, fish fed a 

 vitamin-deficient diet were often divided into 

 two subgroups during the course of the study. 

 One subgroup remained on the vitamin-deficient 

 diet while the recovery subgroup was fed the 

 complete diet to detect positive responses such as 

 accelerated growth rate and disappearance of 

 deficiency symptoms. 



More recently, biochemical criteria such as 

 activities of specific enzymes requiring a given 

 vitamin for coenzyme formation have been used 

 to determine qualitative and quantitative vita- 

 min requirements of fishes (C. E. Smith et al. 

 1974; Cowey 1976). According to C. E. Smith et 

 al. (1974), biochemical defects in the form of re- 

 duced enzyme activity allow detection of pre- 

 clinical vitamin deficiencies. A review of vitamin 

 requirements of fishes was presented by Halver 

 (1979). 



Thiamine 



Essentiality of dietary thiamine has been veri- 

 fied for brook, brown {Salmo trutta), and rainbow 

 trout (McLaren et al. 1947; Phillips and Brock- 

 way 1957), chinook salmon (Halver 1957), coho 

 salmon (Coates and Halver 1958), channel cat- 

 fish (Dupree 1966), rainbow trout (Kitamura et 

 al. 1967a; Aoe et al. 1969), Japanese eel (Arai et 

 al. 1972a), red sea bream (Yone 1975), and turbot 

 (Cowey et al. 1975). Thiamine deficiency symp- 

 toms commonly observed in many of these fish 

 species include anorexia, poor growth, depig- 

 mentation, and loss of equilibrium. Hemorrhage 

 and congestion of fins has been noted in thiamine- 

 deficient Japanese eel (Hashimoto et al. 1970; 

 Arai et al. 1972a) and thiamine-deficient com- 

 mon carp (Aoe et al. 1969). 



Quantitative thiamine requirements have 

 been determined for turbot and channel catfish. 

 Cowey et al. (1975) detected optimal erythrocyte 

 transketolase (thiamine pyrophosphate serves as 

 coenzyme) activity in turbot fed 2.6 mg thiamine/ 

 kg dry diet, whereas maximal growth occurred 

 at dietary thiamine concentrations >0.6 mg/kg 

 dry diet. Therefore, in addition to growth rates, 

 functional evidence such as enzyme activity also 



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