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Injuries to Brown Trout and Rainbow Trout Induced by Capture with Pulsed Direct Current
Author(s) -
Thompson Kevin G.,
Bergersen Eric P.,
Nehring R. Barry
Publication year - 1997
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(1997)017<0141:itbtar>2.3.co;2
Subject(s) - electrofishing , rainbow trout , brown trout , fishery , trout , salmo , fish <actinopterygii> , biology
Brown trout Salmo trutta 10–49 cm total length and rainbow trout Oncorhynchus mykiss 13–51 cm total length were captured in three Colorado rivers with 60‐Hz pulsed DC applied with boat‐mounted (single mobile anode) and “walk” (shore‐based multiple mobile anode) electrofishing systems, then X‐rayed and necropsied to evaluate spinal and hemorrhage injuries resulting from exposure to electrofishing. Among three study streams, spinal injuries were found in 18–64% of rainbow trout and 18–52% of brown trout collected by boat electrofishing, and in 6–40% of rainbow trout and 27–38% of brown trout collected by walk electrofishing. Overall, more than half of the injured fish were judged to have the lowest severity of spinal injury, and in 11 of 12 samples 2.1 % or less of the fish sustained the most severe class of injury (class 3‐fractured vertebra or separated spinal column). Injured rainbow trout collected by boat electrofishing tended to have more severe injuries than the other test groups. Hemorrhage injuries were found in 28–65% of rainbow trout and 24–45% of brown trout collected by boat electrofishing, and in 13–49% of rainbow trout and 13–30% of brown trout collected by walk electrofishing. Logistic regression modeling of both types of injury revealed that rates of fish injury differed among the streams studied. Length of fish was significantly related to the probability of injury in most of the best models, longer fish having a greater chance of sustaining injuries. Rates of injury were also found to vary with species in most models, and rainbow trout were usually more likely to be injured than brown trout for a given method and river. Method of capture also influenced the rate of injury. Where this occurred, boat electrofishing always injured a higher proportion of fish than did walk electrofishing.