Comparison of field-based and indirect estimates of daily food consumption in larval perch and zander |
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Authors: | S Worischka T Mehner |
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Institution: | Institute of Hydrobiology, University of Technology, D-01062 Dresden, Germany |
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Abstract: | Since bioenergetics models for 0+ fish have seldom been validated by field consumption estimates, field-based and indirectly estimated daily food rations were compared in larval perch Perca fluviatilis and zander Stizostedion lucioperca. Field-based estimates were calculated with linear and exponential evacuation rates based on gut fullness data during a 24-h cycle, with hourly field samplings instead of the normally recommended 3-h intervals. Indirect calculations used bioenergetics modelling with variable activity multipliers ( A ). Field-based estimates of daily rations ranged between 0·21 and 0·27 g g?1 day?1 in perch (mean L T 13·1 mm) and 0·31–0·40 g g?1 day?1 in zander (mean L T 10·6 mm). The higher values were calculated by using the exponential model. Daily rations calculated by bioenergetics modelling with A = 1 were only slightly higher than direct estimates in both species. However, if A values >1 were used, calculated daily rations were substantially higher than direct estimates. Estimates of daily ration based only on every third value ranged between 41 and 72% compared with 1-h intervals, mainly because of lower estimates of evacuation rate. |
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Keywords: | bioenergetics gut evacuation models age-0 fish |
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