Growth and Mortality of Invasive Flathead Catfish in the Tidal James River, Virginia

Abstract

Invasive species are a major threat to biodiversity of native fishes in North America. In Atlantic coastal rivers of the United States, large catfishes introduced from the Gulf of Mexico drainages have become established and contributed to native species declines. Flathead Catfish Pylodictis olivaris were introduced to the Chesapeake Bay drainage in the 1960s and 1970s in the James and Potomac river systems in the eastern United States. Diet studies have found James River Flathead Catfish function as apex predators and are known to consume at-risk Alosa spp. To limit further range expansion and impacts to native species, resource management agencies need information on population characteristics to support population assessments and management plan development. Thus, we examined temporal trends in growth rates and estimated total instantaneous mortality for tidal James River Flathead Catfish collected by Virginia Department of Game and Inland Fisheries from 1997 to 2015. Parameters of the von Bertalanffy growth model with length-at-age observations pooled across sampling years were estimated as L ' ¼ 1,059 mm, k ¼ 0.231/y, and t 0 ¼ 0.55 y. Flathead Catfish growth differed among sampling years, especially for the years 2007 and 2014, which had the largest sample sizes. However, there were no obvious temporal trends in growth trajectories. James River Flathead Catfish tend to grow much faster than most populations used in development of the relative growth index, but the species is known to grow faster in its nonnative range. Consequently, scientists and managers should use caution when applying growth indices if native and nonnative populations are not expressly considered in development of the index. We estimated total instantaneous mortality as Z ¼ 0.50 and mean natural mortality from six estimators as M ¼ 0.30. A lack of older individuals in the population means that mortality rates may be overestimated as a result of gear selectivity or ongoing maturation of the population. These data provide information to support future work examining the species in the James River and development of population models to evaluate management strategies and management plans.

Two Decades of Advancement in Flathead Catfish Research

“…2016; Hilling et al. 2019). One exception is the Satilla River, Georgia, where A was reported as 0.62 (Bonvechio et al.…”

“…During summer, Flathead Catfish are most commonly found in shallow (<3 m) locations with large woody debris, riprap, or hard-bottom substrates (Weller and Winter 2001;Vrtiska et al 2004;Daugherty and Sutton 2005a;Malindzak 2006*;Huck 2014*;Blank et al 2021, this special issue), but in winter they move to water depths exceeding 4 m in deep, main-channel pools (Daugherty and Sutton 2005a). Nighttime habitat use includes a greater proportion of open-water habitat away from wood and rock (Daugherty and Sutton 2005a) Mayo and Schramm 1999;Odenkirk et al 1999;Eggleton 2001*;Haas et al 2001;Irwin 2003, 2011;Vrtiska et al 2003;Eggleton and Schramm 2004;Waters et al 2004;Pine et al 2005 Dobbins et al 1999;Pugh and Schramm 1999;Weller and Winter 2001;Bayne et al 2002;Vokoun 2003*;Travnichek 2004;Vokoun and Rabeni 2005a;Vokoun and Rabeni 2005b;Meerbeek 2007 Kwak et al 2006;Sakaris et al 2006;Donabauer 2009*;Marshall et al 2009aMarshall et al , 2009bRypel 2011Rypel , 2013Steuck and Schnitzler 2011;Bonvechio et al 2016;Lucchesi et al 2017;Massie et al 2018;Hilling et al 2019 TWO DECADES OF FLATHEAD CATFISH RESEARCH S13…”

“…There is generally no difference in growth between sexes in rivers (Grabowski et al 2004;Steuck and Schnitzler 2011), but males can grow longer than females in reservoirs (Marshall et al 2009b). Flathead Catfish generally grow faster in rivers where they are introduced than in rivers where they are native (Grabowski et al 2004;Kwak et al 2006;Sakaris et al 2006;Rypel 2013;Bonvechio et al 2016;Hilling et al 2019). Within their native range, Flathead Catfish generally grow faster in reservoirs than in rivers (Kwak et al 2006;Lucchesi et al 2017), but invasive riverine populations typically grow faster than fish in either habitat within the species' natural range (Kwak et al 2006;Sakaris et al 2006).…”

Range Expansion and Factors Affecting Abundance of Invasive Flathead Catfish in the Delaware and Susquehanna Rivers, Pennsylvania, USA

“…Developing baseline population measures will help to assess changes in Flathead Catfish abundance and other vital statistics (e.g., growth rates) as the species continues to become more established. Initial data have shown rapid growth rates in the Susquehanna River (Massie et al 2018;Hilling et al 2019), but continued analysis is needed to track temporal changes. In both tidal and nontidal reaches, a series of long-term monitoring sites would help to assess temporal changes in the population.…”

Carbon dynamics at the river-estuarine transition: a comparison among tributaries of Chesapeake Bay

“…However, the rate of biomass removal for one of the dominant metazoans (catfish) can be used as a first approximation of their annual production. Catfish were introduced to the James during the 1970's and 1980's and now dominate the fishery (Fabrizio et al 2018), which has led to questions about their influence on food webs and ecosystem processes (Greenlee and Lim 2011;Hilling et al 2019;Schmitt et al 2019). The biomass of catfish removed from the James represents a conservative estimate of their annual production in that current harvest rates have not brought about declines in the catfish population, indicating that annual production exceeds the amount of biomass removed (Orth et al 2017).…”