Movement, dispersal, and home ranges of tournament displaced largemouth and spotted bass in Lake Martin, Alabama

Abstract

Anglers fishing in black bass tournaments often displace fish great distances from their site of capture and the effects of tournament displacement on movement and behavior of fish after release have been variable. Accumulation of black bass, which may have negative effects on populations and the fishery, can occur when many tournaments displace large numbers of black bass to a single tournament processing site. Largemouth bass Micropterus salmoides and spotted bass M. punctulatus were implanted with radio transmitters to observe the effect of tournament displacement on movement and behavior in Lake Martin (16,188 ha), Alabama. In April-May 2005, 10 largemouth bass and 10 spotted bass were collected with electrofishing, radio-tagged, and transported to a popular tournament processing site (Wind Creek State Park; WCSP). In addition, 10 largemouth bass and 9 spotted bass were tagged and released at their capture location to serve as control fish. In November 2005, 7 spotted bass and 8 largemouth bass weighed-in at black bass tournaments were implanted with radio transmitters and released at WCSP. Both groups of displaced largemouth bass and spotted bass moved farther from the release site than control fish over time. Fish displaced in spring 2005 exhibited higher daily movement than control fish during the spring, summer, and fall 2005. Diel behavior was not significantly different between the two experimental groups. No significant differences were detected between the 50 and 95% kernel home range estimates of control and displaced largemouth bass. However, control spotted bass had smaller 50 and 95% home ranges than control largemouth bass. Displaced largemouth bass set up home ranges 9 to13 km from WCSP, 47 to 85 d after being released. For fish tagged in November 2005, 57% (4 of 7 fish) of the tournament displaced fish remained within 2 km of the WCSP release site for 3 months. All tournament simulated fish moved farther than 2 km from the WCSP release site within 3 months. Dispersal of black bass from the tournament release site was used to model the increase in biomass of black bass that occurred within 2 km of the release site during the spring 2005. Based on the model and estimates of standing stock biomass from Lake Martin, estimates of black bass biomass possibly doubled within 2 km of WCSP (146 ha) as tournament displaced fish contributed nearly 9 kg/ha during the 3-month tournament season. Behavior of tournament released fish was altered for up to 9 months following release and short-term accumulation of fish at the release site probably occurred. Most displaced black bass migrated from WCSP within a few months of release, but some remained in the vicinity of WCSP for up to 3-6 months. Short-term accumulation of fish occurred which likely artificially increased black bass abundance near the release site. Simulated tournament fish moved more than control fish for up to 9 months and altered behavior could effect growth, survival, and reproductive output. To negate the effects of tournament displacement additional tournament release sites could be used on Lake Martin and improvement of the “live release” boat could expedite dispersal.