Experimental Prey Selection by Non-Native Bullseye Snakehead from Southern Florida

Bullseye snakehead Channa marulius is a predatory fish native to Southeast Asia. A non-native population was discovered in canals of Broward County, Florida, in 2000. Currently, bullseye snakehead is one of the most abundant large, predatory fish in some canals. This species is a generalized predator, consuming a variety of vertebrate and invertebrate prey, with fish making up the bulk of the diet in Florida. Otherwise, little is known about the trophic ecology of this species. We determined the length-specific gape size of bullseye snakehead and experimentally tested maximum prey size using blue tilapia Oreochromis aureus.  Previous literature suggested that snakeheads consume fish prey larger than gape size. In contrast, no snakehead (n = 11; 444-765 mm total length) consumed prey with body depths larger than 80% of predator gape; mean maximum prey size was 75%. Snakeheads (n = 12) offered a choice of three blue tilapia size classes (large = 75-80% of gape; medium = 50-60%; and small = 20-30%) were not strongly size-selective. Snakeheads were offered blue tilapia, golden shiner Notemigonus crysoleucas, eastern mosquitofish Gambusia holbrooki, and crayfish Procambarus spp. to determine prey selection. Crayfish were quickly and easily captured and consumed, showing that snakeheads can overcome prey morphological defenses. Snakeheads (n = 8) strongly selected crayfish (α = 0.80) and selected against all fish (α < 0.15). This selection pattern is unusual for predatory fishes in tank studies and suggests that snakeheads likely select the least mobile prey. Future work includes (1) comparing size of prey in stomachs of snakeheads collected in the field with predator gape size and (2) estimating prey vulnerability for snakeheads in a south Florida canal using data on snakehead and prey fish size structure. These data, coupled with diet information, will advance understanding of potential impacts of bullseye snakehead on Florida fish communities.