| Abstrakt: |
Selective feeding on and digestion of detritus in surface sediments (organic matter < 10%, nitrogen < 0.4%) by age-0 and adult (ages 3 and 4) gizzard shad Dorosoma cepedianum in Acton Lake, Ohio (water temperature = 15-18°C) were compared with those of age-0 fish fed two particulate diets (low-quality diet: organic matter = 10%, nitrogen = 0.3%; high-quality diet: organic matter = 89%, nitrogen = 6.7%) at 18°C in the laboratory. Fish feeding on natural detritus and the low-quality diet exhibited mean selection efficiencies, ratios of nutrient weight percentages in the gizzard to those in the sediment or food, of 1.8-2.9 for total organic matter, 2.4-4.4 for total carbon, and 3.2-13.2 for total nitrogen. Fish fed the high-quality diet exhibited no selective feeding. Mean digestive efficiencies, 100 [ 1 - (feces value ÷ gizzard value)], for total organic matter, total carbon, and total nitrogen in the diets had ranges of 50-66, 51-64, and 62-84%, respectively. Age-0 fish feeding on natural detritus and the two laboratory diets exhibited similar digestive efficiencies. In addition, age-0 and adult gizzard shad were equally efficient at digesting the components of natural detritus. Gizzard shad apparently can ingest selectively the more nutritious portions of low-quality particulate diets in the field and laboratory and digest a substantial proportion of the nutrients present. [ABSTRACT FROM AUTHOR] |
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