An assessment of barotrauma and the stock characteristics of Tennessee River sauger populations

An intense winter fishery for sauger Sander canadensis exists in the Tennessee River. Although previous research suggested that catch-and-release mortality due to barotrauma or other factors was not a serious problem for undersized sauger (<356 mm total length), angler concerns persisted. The objectives of this study were to assess the survival of saugers inflicted with barotrauma and determine whether capture depth, ascent speed, and fish size contributed to the frequency and severity of barotrauma. In February 2008 and from January to March 2009, 81 saugers (73 alive at release, 8 euthanized) were affixed with ultrasonic transmitters. The magnitudes of movements (or lack thereof) by saugers released alive were compared with those of the euthanized fish to assess survival. Sauger experienced barotrauma over a wide range of capture depths (6-19 m). Barotrauma was evident in 72% of saugers collected in 2008-09; about 33% of those individuals exhibited severe barotrauma. There was a positive relationship between the incidence of barotrauma and capture depth, but not fish size or ascent rate. Sixty-seven percent of saugers released alive exhibited maximum daily movements that exceeded 0.5 km/d (the greatest movement of any euthanized fish) and those fish (n = 42) were classified as survivors. Survival of released saugers was directly related to incidence of barotrauma and capture depth.;In 1992, minimum length limits for sauger populations in the Tennessee River were established to reduce exploitation and improve the size distribution of sauger populations. The objectives of this study were to determine the efficacy of those limits by assessing spatial and temporal differences in stock characteristics and the likelihood of growth- and recruitment-overfishing. Saugers were collected from late winter to early spring in 2008 and 2009 in Kentucky Lake and Watts Bar Lake using monofilament experimental gill nets. Mean lengths and mean ages of sauger varied significantly among years and reservoirs and Watts Bar sauger were generally older and longer than sauger in Kentucky Lake. Although means varied significantly among years, mean ages and mean lengths did not exhibit any trends between 1990 and 2009 in either reservoir. In 2008-2009, the Kentucky Lake sauger population was not exhibiting signs of growth overfishing or recruitment overfishing under the current minimum total length limit of 356 mm. The Watts Bar Lake sauger population was not exhibiting signs of growth overfishing under the current total length limit of 381 mm, but is susceptible to recruitment overfishing at high (>40%) exploitation rates. Eliminating the size limits in either reservoir would increase the likelihood of both growth- and recruitment overfishing, but the extent of risk would depend on the level of exploitation and natural mortality in each reservoir.