Content area
Full Text
Abstract - Ictalurus furcatus (Blue Catfish) provide trophy recreational fishing opportunities in Virginia's tidal rivers; however, potential ecological impacts are of concern. We used mark-recapture techniques and electrofishing in 2007 and 2014 to estimate Blue Catfish density and biomass in Powell Creek. A 66% decline in fish density occurred between 2007 (708 fish/ha) and 2014 (239 fish/ha) and biomass declined by 31% over the same timeframe (266 kg/ha to 185 kg/ha). These findings are supported by long-term monitoring trends in the tidal James River. Here, we provide: (1) data relative to temporal shifts in abundance and biomass, (2) data for use in subsequent population-dynamics analyses, and, (3) points of caution when assuming temporally static populations for introduced species. We demonstrated the feasibility of low-frequency electrofishing and mark-recapture methods to estimate Blue Catfish abundance, and recommend use of the approach where catfish abundance estimates are important.
Introduction
Ictalurus furcatus (Valenciennes) (Blue Catfish) is native to the Mississippi River drainage and range geographically into Central America (Graham 1999). The species is a common, though not native, component of the fish assemblages of fresh to mesohaline sections within Virginia's tidal rivers (Hewitt et al. 2009, Tuckey and Fabrizio 2016). Blue Catfish constitutes a valuable recreational fishery in Virginia's tidal rivers; trophy sizes of up to 46 kg have been recorded (Virginia Department of Game and Inland Fisheries [VDGIF], Angler Awards Program, unpubl. data); however, managers and researchers are uncertain about overall impacts to the Chesapeake Bay ecosystem. Schmitt et al. (2017) found that Blue Catfish in tidal rivers are opportunistic omnivores, but evaluation of overall impacts to prey species are dependent on size estimates of populations of Blue Catfish.
Ecosystem-based management has broad applicability to the future health of the Chesapeake Bay and its tributaries, and modeling ecosystem processes and functions must be informed through various data inputs (Boesch 2006, Christianson et al. 2009). For example, the modeling software Ecopath with Ecosim requires biomass for its mass-balance-modeling structure, and direct estimates of Blue Catfish biomass would be useful for modeling ecosystems within the Chesapeake Bay watershed (Christianson et al. 2009). Although population estimates are available for some catfish species (Daugherty and Sutton 2005, Fabrizio et al. 2018, Newcomb 1989), monitoring programs rely heavily on relative-abundance indices to...