Stress-mortality Differences between Intensively-and Extensively-Reared Largemouth Bass

Stress due to confinement in a net caused higher mortalities in largemouth bass Micropterus salmoides salmoides which were extensively-reared in ponds on zooplankton and other invertebrates than in those which were intensively-reared in raceways on pelleted food. Fish that were intensively-reared weighed more than the fish reared in ponds, although both groups were sorted with the same bar-grader. Intensively-reared fish exhibited 3% and 9% mortalities after 13- and 16-hour net confinements, respectively, compared to 34% and 38% for those fish reared in ponds. Fish reared intensively may be better able to tolerate the stress of harvest, handling, and transportation than extensively-reared fish.