An experimental approach to determine esocid prey preference in replicated pond systems

Competitive interactions between salmonids and white suckers (Catostomus commersonii) often result in poor salmonid growth, condition, and ultimately angler catch-per-unit-effort. Fisheries managers frequently introduce hybrid northern pike (Esox lucius) and muskellunge (E. masquinongy), known as tiger muskellunge, as biological control agents to reduce the abundance of undesirable species including white suckers, while simultaneously attempting to create viable recreational fisheries with stocked salmonids. In this study, northern pike were used to evaluate esocid prey preference between naïve, hatchery-reared rainbow trout (Oncorhynchus mykiss) and wild white suckers. Enclosures containing northern pike were stocked with rainbow trout and white suckers at 2 densities (50:50 and 20:80, respectively) to represent different ratios of forage. Weekly sampling by beach seine was used to determine rainbow trout and white sucker mortality. When the experiment was complete, enclosures were drained to determine overall survival of the forage species. Rainbow trout numbers declined precipitously to zero, while 60–75% of white suckers remained across all treatments. This study demonstrated a clear difference in survival of rainbow trout and white suckers (rainbow trout having lower survival) in the presence of northern pike under these conditions. We suggest fisheries managers consider these findings when stocking or managing for piscivores to control undesirable fish species, or to create recreational fisheries, while simultaneously stocking naïve sport fish vulnerable to predation.