Trophic Relations of Introduced Flathead Catfish in an Atlantic River

Abstract

The flathead catfish Pylodictis olivaris is a large piscivore that is native to the Mississippi and Rio Grande river drainages but that has been widely introduced across the United States. River ecologists and fisheries managers are concerned about introduced flathead catfish populations because of the negative impacts on native fish communities or imperiled species associated with direct predation and indirect competition from this apex predator. We studied the trophic relations of introduced flathead catfish in an Atlantic river to further understand the effects on native fish communities. Crayfish (Astacidea) occurred most frequently in the flathead catfish diet, while sunfish Lepomis spp. comprised the greatest percentage by weight. Neither of two sympatric imperiled fish species (the federally endangered Cape Fear shiner Notropis mekistocholas and the Carolina redhorse Moxostoma sp., a federal species of concern) was found in any diet sample. An ontogenetic shift in diet was evident when flathead catfish reached about 300 mm, and length significantly explained the variation in the percent composition by weight of sunfish and darters Etheostoma and Percina spp. Flathead catfish showed positive prey selectivity for taxa that occupied similar benthic microhabitat, highlighting the importance of opportunistic feeding and prey encounter rates. Flathead catfish displayed a highly variable diel feeding chronology during July, when they had a mean stomach fullness of 0.32%, but then showed a single midday feeding peak during August (mean fullness = 0.52%). The gastric evacuation rate increased between July (0.40/h) and August (0.59/h), as did daily ration, which more than doubled between the 2 months (3.06% versus 7.37%). Our findings increase the understanding of introduced flathead catfish trophic relations and the degree of vulnerability among prey taxa, which resource managers may consider in fisheries management and conservation of native fish populations and imperiled species.

Population dynamics of introduced flathead catfish in Lake Mitchell, South Dakota

“…Highly abundant forage fish, such as gizzard shad (Dorosoma cepedianum), freshwater drum (Amplodinotus grunniens), and white perch (Morone americana) were the most common food items in flathead catfish in Great Plains reservoirs (Turner & Summerfelt 1970;Layher & Boles 1980;Vrtiska et al 2003) while flathead catfish introduced into a Minnesota lake primarily consumed common carp (Cyprinius carpio) and black bullheads (Ameiurus melas) (Davis 1985). Flathead catfish appear to be opportunistic feeders typically consuming the most abundant and easily-accessible prey items (Layher & Boles 1980;Davis 1985;Haas et al 2001;Vrtiska et al 2003;Baumann & Kwak 2011).…”

Evaluation of Recreational Hand‐Crank Electrofishing on Introduced Catfish Species in Southeastern North Carolina

“…It may be that given the Flathead Catfish's opportunistic feeding strategy (Pine et al. ; Baumann and Kwak ), impacts from density‐dependent factors may be lessened under low to moderate harvest levels, although angler harvest rates with this gear are unknown in these systems.…”

“…). Flathead Catfish outcompete species occupying the same benthic habitat through direct (i.e., predation) and indirect (i.e., opportunistic predator) mechanisms (Baumann and Kwak ).…”

Long‐term impacts of introduced flathead catfish on native ictalurids in a north Florida, USA, river

“…Although white catfish and channel catfish showed little or no change in abundance, continued monitoring is recommended, as white catfish have shown evidence of decline in the presence of other introduced ictalurids (Jordan et al . ) and channel catfish have been documented in flathead catfish diets (Weller & Robbins ; Baumann & Kwak ).…”

“…Considering the recency of colonisation of the fourth sampling site (Ebro, most downstream site) by flathead catfish, it seems likely that this site will eventually experience similar declines in spotted bullhead abundance. Although white catfish and channel catfish showed little or no change in abundance, continued monitoring is recommended, as white catfish have shown evidence of decline in the presence of other introduced ictalurids (Jordan et al 2004) and channel catfish have been documented in flathead catfish diets (Weller & Robbins 1999;Baumann & Kwak 2011).…”