Bioenergetic study of brown trout in a natural stream


Category:  Wildlife Science
Linked Publication
Language: English
Author(s): Paul E. Mongillo
Description: A combination of field and laboratory techniques were used to quantify the seasonal and yearly energy budgets of brown trout Salmo trutta) in a lotic system. Effects of environmental factors were examined in an attempt to explain the levels of energy budgets and why these levels change. Food consumption was measured in the wild to determine the total calories available for energy transformations. The quantity of food consumed was estimated as a percentage of stomach capacity. Brown trout stomach contents were collected with a stomach pump every 3 hours throughout a 24 hour period. Consumption rates ranged from a low of 4. 99 cal/kcal/day in November to a high of 22. 31 cal/kcal/day in late April. Energy expenditure (standard plus swimming metabolism) was measured using a combination of laboratory and field methods. Velocities of water where trout swam were determined in the wild by taking water velocity readings at the location where a fish was observed. Brown trout swam in velocities between 11.46 and 14.14 cm/sec. Fish acclimated at 3.5, 7.5, and 11.5 C were forced to swim at 12.80 cm/sec in an active respirometer to determine energy expenditure. The metabolic rates ranged from a low of 4. 17 cal/kcal/day at winter temperatures to a high of 7. 26 cal/kcal/day at summer temperatures. Standard metabolism, growth, and waste products were determined from literature sources. Swimming metabolism was derived by taking the difference between energy expenditure and standard metabolism. Specific dynamic action (SDA) was estimated by subtracting the sum of growth, energy expenditure, and waste from food consumed. The average energy budget for one entire year as a percentage of total food energy was 26 percent standard metabolism, 23 percent swimming metabolism, 18 percent growth, 20 percent waste, and 13 percent SDA. The factors determined to have the greatest effect on energy transforma tions are water temperature, photoperiod, and water flow. Temperature directly affects metabolism and indirectly affects food consumption and growth. Photoperiod has a direct effect on thyroid activity and an indirect effect on metabolism, food consumption, and growth. Stream flow directly affects competition levels and has an indirect effect on metabolism, food consumption, and growth.