FISH NUTRITION
47 1
variation in the hatchery diet ingredients and in their content of the
major components, correlation between body composition and diet
composition was evident (Wood et al., 1957b).
Westman et al. (1969) compared growth and body composition of
rainbow trout fed on nine different commercial diets. Greatest variation
occurred in the fat content of the fish (6.0-9.8% on a wet weight basis)
which was related to the fat and calorie content of the diet. The content of water plus fat was relatively constant (76.7% to 79.1% of the
whole) and there was something of an inverse relationship between body
water and body fat. Elevated leveIs of body fat occur not infrequently
as a consequence of feeding high fat diets (Phillips et al., 1966; Mann,
1959) and are interpreted by Westmann and his colleagues as indicating
a surplus of dietary calories.
The composition of wild fish is influenced by a large number of
environmental and physiological factors, especially after they reach
maturity, so that comparison of the composition of such fish with
their hatchery-reared brethren may be somewhat tendentious.
Nevertheless, a similar trend toward elevated lipid levels is evident
in plaice reared on an empirical ration (Table XIX) as compared with
young two year old plaice taken during September after a period when
natural food should have been abundant. These elevated lipid levels
may result from the reduced activity in hatchery reared fish which
do not have to hunt for their food and thus burn less energy.
Measurements of body length and weight have frequently been
used to assess and compare the nutritional adequacy of different
treatments. The above considerations indicate that data on body
composition are desirable for a full evaluation of these treatments.
TABLE XIX. GROSS CO~~POSITION OB PLAICE OB COMPARABLE SIZES OBTAINED
KROM DIBFERENT SOURCES
Source of fish or
Water
Protein
Lipid
Aeh
Total
dietary treatment
Wild fish
80.03
14.92
1.17
3.30
99.42
White Fish Authority
hatchery HunterstoxP
77.1 1
16.72
1.78
3.23
97.84
Laboratory reared on
pelleted dietb
76.49
16.43
4.74
3.01
99.67
=, Diet-minced trash white fish, binding agent, vitamin pre-mix.
b, Diet (drymateria1s)-white fish meal 496%,spray dried milk lO.O%, shrimp meal 26%,
aom oil 8.0%. cod liver oil 3.0%. vitamin pre-mix 2.7% minerals 0.3%, binding agent
4.0%.
47 1
variation in the hatchery diet ingredients and in their content of the
major components, correlation between body composition and diet
composition was evident (Wood et al., 1957b).
Westman et al. (1969) compared growth and body composition of
rainbow trout fed on nine different commercial diets. Greatest variation
occurred in the fat content of the fish (6.0-9.8% on a wet weight basis)
which was related to the fat and calorie content of the diet. The content of water plus fat was relatively constant (76.7% to 79.1% of the
whole) and there was something of an inverse relationship between body
water and body fat. Elevated leveIs of body fat occur not infrequently
as a consequence of feeding high fat diets (Phillips et al., 1966; Mann,
1959) and are interpreted by Westmann and his colleagues as indicating
a surplus of dietary calories.
The composition of wild fish is influenced by a large number of
environmental and physiological factors, especially after they reach
maturity, so that comparison of the composition of such fish with
their hatchery-reared brethren may be somewhat tendentious.
Nevertheless, a similar trend toward elevated lipid levels is evident
in plaice reared on an empirical ration (Table XIX) as compared with
young two year old plaice taken during September after a period when
natural food should have been abundant. These elevated lipid levels
may result from the reduced activity in hatchery reared fish which
do not have to hunt for their food and thus burn less energy.
Measurements of body length and weight have frequently been
used to assess and compare the nutritional adequacy of different
treatments. The above considerations indicate that data on body
composition are desirable for a full evaluation of these treatments.
TABLE XIX. GROSS CO~~POSITION OB PLAICE OB COMPARABLE SIZES OBTAINED
KROM DIBFERENT SOURCES
Source of fish or
Water
Protein
Lipid
Aeh
Total
dietary treatment
Wild fish
80.03
14.92
1.17
3.30
99.42
White Fish Authority
hatchery HunterstoxP
77.1 1
16.72
1.78
3.23
97.84
Laboratory reared on
pelleted dietb
76.49
16.43
4.74
3.01
99.67
=, Diet-minced trash white fish, binding agent, vitamin pre-mix.
b, Diet (drymateria1s)-white fish meal 496%,spray dried milk lO.O%, shrimp meal 26%,
aom oil 8.0%. cod liver oil 3.0%. vitamin pre-mix 2.7% minerals 0.3%, binding agent
4.0%.