Effects of Repeated Electroshocking on Instantaneous Growth of Trout

Gatz, A; Loar, James; Cada, Glenn

ABSTRACT: Instantaneous growth rates were calculated for age-1, −2, and −3 + wild rainbow trout (Salmo gairdneri) and brown trout (Salmo trutta) at each of eight stream sites on five streams in western North Carolina and eastern Tennessee. Growth rates of individual trout that had been electroshocked with pulsed DC two to seven times within a 12-month period were lower than the average growth rates for trout of the same age and species at their respective sites. This decrease in growth rate occurred significantly more often among age-1 and −2 trout than among those 3 years and older, and more often among trout that had been electroshocked within the last 2.5 months than among trout that had 3 or more months to recover from electroshocking. These results indicated that fisheries management studies should be designed to avoid repeated electroshocking, especially at intervals of less than 3 months. Growth studies in which more than a small fraction (e.g., >20%) of the total population is repeatedly electroshocked at short (<3-month) intervals are likely to underestimate growth rates.