Dispersal Patterns of Coastal Largemouth Bass in Response to Tournament Displacement

Tournament displacement, stockpiling near release points, and handling stress are major concerns for managers of sport fisheries in the southeastern USA. We examined the effects of transport distance and tournament handling stress on dispersal of 40 Largemouth BassMicropterus salmoides via telemetry from May 2012 to September 2013 in the Albemarle Sound system of eastern North Carolina. Largemouth Bass were captured from four tributaries of Albemarle Sound and transported 16.5–45 km to a central release point before being acoustically tagged and released. Movement data from an array of passive receivers was used to calculate rates of dispersal from the release point, emigration from the study area and return to capture location over time. Blood cortisol concentration, collected from our tagged Largemouth Bass and those captured in an actual tournament, was used to determine the effect of stress on potential postrelease movement and survival. Our findings indicate little evidence of long-term stockpiling (i.e., fish remaining close to release point; Richardson-Heft et al. 2000); 57% of displaced Largemouth Bass dispersed more than 500 m from the release point within 7 d and 87% within 21 d postrelease. Half of those that emigrated from Edenton Bay returned to their capture location. However, no Largemouth Bass displaced 35–45 km returned to their capture locations, suggesting that long-distance displacement inhibits return. Fishing (2.8%) and nonharvest mortality (0.5%) were low throughout this study except for peaks observed during late spring (42.9%) and early summer (25.1%) of 2013. Mean cortisol concentrations were similar in Largemouth Bass collected during our simulated tournament (126.7 ng/mL) and an actual tournament (118.4 ng/mL). However, cortisol concentrations were unrelated to survival, postrelease dispersal, or return of tagged individuals to their capture location. Largemouth Bass appear to be able to cope with current tournament practices; however, restrictions on displacement distance may increase return rates. Displacement of fish during angling tournaments can have a significant effect on the distribution of target species (Lantz and Carver 1976; Fewlass and Groves 1991; Richardson-Heft et al. 2000; Wilde 2003), and the increasing popularity of competitive fishing (Duttweiler 1985; Kerr and Kamke 2003; Schramm and Hunt 2007; Driscoll et al. 2012) may exacerbate this effect. The increasing number of competitive fishing tournaments has led to concerns about potential stockpiling of captured fish near weigh-in locations, detrimental effects of tournament stress on fish health, and postrelease mortality *Corresponding author: [email protected] Received August 26, 2014; accepted January 14, 2015 431 North American Journal of Fisheries Management 35:431–439, 2015 American Fisheries Society 2015 ISSN: 0275-5947 print / 1548-8675 online DOI: 10.1080/02755947.2015.1009660 D ow nl oa de d by [ N or th C ar ol in a St at e U ni ve rs ity ] at 0 6: 23 2 8 A ug us t 2 01 5 (Gilliland 1999; Richardson-Heft et al. 2000; Kerr and Kamke 2003; Schramm and Hunt 2007). An estimated 25,000 competitive fishing tournaments occur annually in North America; a significant portion of these tournaments target black basses (Micropterus) and in particular Largemouth Bass Micropterus salmoides (Duttweiler 1985; Schramm et al. 1991b; Kerr and Kamke 2003). For example, Driscoll et al. (2012) estimated that Largemouth Bass were the focal species of more than 90% of fishing tournaments held between 2009 and 2011 in the southeastern USA. While much of this tournament angling occurs in inland systems, many competitive tournaments targeting Largemouth Bass take place in coastal river systems in North Carolina (Dockendorf et al. 2004; McCargo et al. 2007; Ricks and McCargo 2013) as well as New York, Maryland, and Alabama (Nack et al. 1993; Richardson-Heft et al. 2000; Norris et al. 2005). Studies examining the effect of tournament displacement on Largemouth Bass have focused primarily on inland lakes and impoundments. Results from these studies are equivocal concerning postrelease dispersal, with support for both substantial (>1.6 km; Healy 1990; Fewlass and Groves 1991) and restricted (<1.6 km; Lantz and Carver 1976; Gilliland 1999) distance traveled from the release point. In contrast, studies focused on tournament displacement of Largemouth Bass in coastal systems have yielded results that are more consistent. For example, Richardson-Heft et al. (2000) found that 64% of Largemouth Bass displaced in Chesapeake Bay dispersed more than 500 m within 7 d, and Norris et al. (2005) reported 58% dispersal beyond 500 m within a week of release in the Mobile–Tensaw delta, Alabama. Despite evidence for rapid postrelease dispersal of Largemouth Bass caught during tournaments in coastal systems, frequent tournaments (e. g., weekly; Gilliland 1999) can create short-term accumulations (Ricks and Maceina 2008) near popular release points. At one such release point in the Chowan River, a tributary of Albemarle Sound, North Carolina, (up to five tournaments occur monthly in the sound) sampling conducted by the North Carolina Wildlife Resources Commission found much higher catch rates (111 fish/h) than at sampling locations (35–78 fish/h; Jeremy McCargo, personal communication). In addition, known tournament release locations often attract tournament and nontournament anglers (Gilliland 1999). This can lead to increases in mortality (Gilliland 1999) due to additive stress from multiple captures, an outcome that fishery managers and angling organizations strive to minimize. Concerns over the fate of angled fish extend to the final distribution of those individuals, including the availability of these fish for further angling (Schramm et al. 1991a), metapopulation structure, and potential overharvest. Although there is some agreement that Largemouth Bass have the ability to return to capture sites following displacement (Stang et al. 1996; Pearson 2002), questions remain regarding how displacement distance, or the distance from capture site to release point, influences the rate of return. In Rideau Lake, Ontario, Ridgway (2002) reported a 47% rate of return for Largemouth Bass displaced less than 8.0 km; however, 0% of the fish displaced more than 8 km returned to their capture location. In contrast, Richardson-Heft et al. (2000) found substantial rates of return for Largemouth Bass displaced 15 km (33%) or 21 km (43%) in the tidal Chesapeake Bay. However, variations in salinity and dissolved oxygen can potentially influence the movement of Largemouth Bass in coastal systems (Heft and Richardson-Heft 2002; Brown 2014; Norris et al. 2005). In addition to tournament displacement, handling stress associated with angling activities (e.g., hooking, air exposure, livewell confinement, weigh-in) can cause substantial physiological disturbances. Stress is commonly evaluated from cortisol levels, which rise rapidly following a stress event, and because samples are easily collected and measured from blood plasma (Wendelaar Bonga 1997; Mommsen et al. 1999). For example, cortisol concentrations from Largemouth Bass caught during large, 2-d tournaments were 140 times the cortisol concentrations of control fish (Suski et al. 2003). These authors later confirmed that angling-associated activities, specifically air exposure during weigh-in, could further exacerbate the physiological disturbance associated with tournament angling (Suski et al. 2004). Sublethal effects of angling stress on Largemouth Bass include depressed growth rates (Wendelaar Bonga 1997; O’Connor et al. 2010), decreased locomotory activity, and reduced reproductive success (Cooke et al. 2000). Although the physiological effects of angling stress have been well documented, the effect of angling stress on postrelease movement and survival of displaced Largemouth Bass remains unclear. The goal of this study was to quantify the effects of displacement on the survival, postrelease dispersal, and rate of return to capture location of Largemouth Bass in an open coastal system. Anglers traverse great distances across Albemarle Sound during tournaments; thus, we tested the effect of a wider range of displacement distances on these variables than has previously been evaluated. We simulated a fishing tournament by collecting Largemouth Bass from four tributaries of the Albemarle Sound often fished by anglers during tournaments; captured bass were transported to a central release point frequently used for tournaments. The orientation of these tributaries allowed us to quantify the effect of open-water crossing on the ability of displaced Largemouth Bass to return to their capture locations. We used acoustic telemetry to monitor postrelease movement and detection data to estimate fishing and nonharvest mortality. These estimates of mortality were used to determine the effect of frequent tournament releases and potentially increased fishing pressure on the survival of displaced Largemouth Bass near the release point. A second goal was to measure cortisol concentrations as an indicator of handling stress effects on rates of dispersal, emigration, return to initial capture location, and mortality of Largemouth Bass displaced during our simulated tournament. Results from this study will help managers ensure the health and distribution of fish captured during tournaments. 432 BROWN ET AL. D ow nl oa de d by [ N or th C ar ol in a St at e U ni ve rs ity ] at 0 6: 23 2 8 A ug us t 2 01 5