Bycatch rates and initial mortality of paddlefish in a commercial gillnet fishery

Tennessee is one of seven states in the U.S. that allows commercial fishing for paddlefish, Polyodon spathula. Although there is a small market for the flesh, most fishers target paddlefish for their valuable roe, which currently brings as much as US$143/kg wholesale. We deployed experimental monofilament and multifilament gillnets in Kentucky Lake, Tennessee-Kentucky, and accompanied commercial gillnet fishers during the 2003–2004 and 2004–2005 commercial fishing seasons (November 15 to April 23) to estimate the bycatch of sublegal (<864 mm eye-fork length) paddlefish, legal males, and legal, but immature, females. Variation in initial mortality (i.e., dead in the nets) was modeled as a function of mesh size, fish length, water temperature, soak time, and twine type using multiple logistic regression. The bycatch rate of sublegal fish in the commercial catch was 60%. Mature females represented only 8% of the catch; thus, the bycatch rate was 92% for fishers targeting egg-laden fish. Most (71%) of the paddlefish were dead in the nets when water temperatures exceeded 17 °C. Mesh size and fish length were not significant (P ≥ 0.098) predictors of initial mortality. The probability of initial mortality was significantly (P ≤ 0.004) and directly related to soak time and water temperature and fish were more likely to be dead in monofilament nets than multifilament nets. The results of this research prompted the state regulatory authority to end the commercial season 8 days sooner (on April 15 each year) to avoid warm water temperatures; however, a proposed ban on monofilament netting met with stiff opposition from commercial fishing interests and the ban was not enacted.