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Healing of Electroshock‐Induced Hemorrhages in Hatchery Rainbow Trout
Author(s) -
Schill Daniel J.,
Elle F. Steven
Publication year - 2000
Publication title -
north american journal of fisheries management
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.587
H-Index - 72
eISSN - 1548-8675
pISSN - 0275-5947
DOI - 10.1577/1548-8675(2000)020<0730:hoeihi>2.3.co;2
Subject(s) - electrofishing , rainbow trout , hatchery , medicine , fish <actinopterygii> , fishery , trout , chinook wind , zoology , biology , anesthesia , oncorhynchus
We monitored healing in electroshock‐induced hemorrhages of myomere blood vessels produced by individually exposing hatchery rainbow trout Oncorhynchus mykiss to direct current ( N = 502) and pulsed direct current ( N = 708). We used voltage gradients and exposure times that were suspected to produce high injury rates to facilitate observation of injury duration in muscle tissue. At 1 d postexposure, 86.1% of the test fish exposed to DC and 81.6% of those exposed to pulsed direct current (PDC) had at least one hemorrhage. Fish exposed to DC averaged 1.86 injuries at 1 d postshocking, and those exposed to PDC averaged 1.45 injuries. Number of hemorrhage injuries per fish began declining by 15 d postshocking in both groups. The severity of injuries initially increased through 15 d postshocking and then decreased through the remaining 3–5 weeks of the tests. At the end of the test, injuries induced by DC had declined by 78.0% (36 d postshocking), and those induced by PDC declined by 92.4% (57 d postshocking). In all, 1.8% of all fish exposed to DC and 1.1% of those exposed to PDC died during the study. Our data for hatchery rainbow trout suggest that hemorrhage injuries in salmonids caused by electrofishing exposure exist for a relatively short time and do not represent a long‐term mortality or health risk to the fish. Because of the ephemeral nature of blood vessel hemorrhages, compared with spinal injuries, future studies that examine electrofishing injuries should evaluate hemorrhage and spinal injuries separately and abandon the practice of combining these data.