Gape: Body Size Relationship of Flathead Catfish

Abstract

The flathead catfish Pylodictis olivaris is a highly piscivorous ictalurid native to central North America whose range has been extended throughout much of the United States. With this range expansion, many populations of native fishes have experienced declines in the number of individuals due to direct predation by flathead catfish. Previous evidence suggests that flathead catfish are opportunistic feeders and may be the least gape limited of North American freshwater piscivores. To better understand the size of prey vulnerable to flathead catfish, we measured gape dimensions for individuals of various sizes to determine the maximum size prey a flathead catfish can kill based on its gape limitations. Our results show the relationship of total length to horizontal and vertical gape and the relationship of flathead catfish total length to the total lengths of ingestible-sized prey of different body shapes. Furthermore, comparisons of the body depth of three common fish species to the gape dimensions showed that no size of largemouth bass Micropterus salmoides, bluegill Lepomis macrochirus, or gizzard shad Dorosoma cepedianum would preclude predation by flathead catfish. Our results support the assumption that the flathead catfish is one of the least gapelimited piscivores.

Predation and Prey Selectivity by Nonnative Catfish on Migrating Alosines in an Atlantic Slope Estuary

“…The primary alosine consumed by Flathead Catfish was Blueback Herring, which was found in nearly 10% of stomachs; Flathead Catfish also consumed American Shad and Alewives but to a lesser degree. Even small Flathead Catfish were piscivorous; this is likely mediated by their huge gape size, which is among the largest observed in any North American freshwater fish species (Slaughter and Jacobson 2008). Because of their voracious feeding habits, Flathead Catfish are already considered to be one of the most ecologically harmful introduced species in the United States (Fuller et al 1999), and several studies have empirically demonstrated declines in native fish populations after the introduction of Flathead Catfish (Guier et al 1984;Ashley and Buff 1988;Thomas 1995;Kwak et al 2006).…”

Assessing Distribution of Migratory Fishes and Connectivity following Complete and Partial Dam Removals in a North Carolina River

“…However, Flathead Catfish appeared capable of passing the notched dam under all flow conditions, suggesting their downstream delays may be a choice (e.g., foraging) rather than forced. Flathead Catfish have the potential to negatively impact native fishes as their large gape size allows them to consume adult American Shad, Gizzard Shad, Largemouth Bass, and Bluegills (Ashley and Buff 1988;Pine et al 2005;Slaughter and Jacobson 2008).…”

Size-selectivity of predatory reef fish on juvenile prey

“…Prey selected by a predator depends on the characteristics expressed by both predator and prey, and how these interact (Cohen et al 1993, Woodward et al 2005, Urban 2007). For many piscivores, the upper limit of potential prey sizes is set by morphological constraints imposed by mouth width, or gape size (a mechanism known as 'gape-limitation'; Persson et al 1996, Slaughter & Jacobson 2008. According to OFT, as predator size increases, the optimal prey size on which to feed should also increase (Hughes 1980).…”