1. Evaluate the relative performance of stocked age-0 (fingerlings) vs. age-1 (yearlings) channel catfish into Ohio reservoirs

Ohio reservoirs have historically been stocked with age-1 fish (yearlings, ~232 mm in total length, TL). The motivation for stocking age-1 individuals over age-0 individuals (fingerlings, ~133 mm TL) appears to primarily emanate from two experimental studies (Krummrich and Heidinger 1973; Spinelli et al. 1985), both of which suggest smaller channel catfish are more vulnerable to predators—specifically largemouth bass (LMB)—than larger individuals. 

However, given the artificiality of these two experiments (carried out in 280-L and 750-L aquaria, respectively) and preference of LMB for alternative prey, whether predation on channel catfish occurs in reservoirs remains an open question. Because Ohio reservoirs offer ample alternative prey (e.g., gizzard shad, Dorosoma cepedianum; bluegill) for LMB, as well as refuges from predation, we hypothesize that predation on channel catfish fingerlings and yearlings will be low in Ohio reservoirs, thus negating the need to rear individuals to age-1 (yearling) sizes in the hatchery. The first objective of this study will test this hypothesis through three joint approaches, ultimately leading to quantifying recruitment rates of stocked fingerlings and yearlings across reservoirs of varying predator (LMB) abundance.

2. Improve our understanding of the ecology of stocked versus wild-produced channel catfish in Ohio reservoirs

Knowledge of the degree to which wild-produced versus hatchery-reared individuals support Ohio’s reservoir fisheries remains an important information gap. We will assess the degree to which stocked individuals contribute to a reservoir’s fishery (relative to wild-produced individuals), as well as the mechanisms that might underlie this success. Towards this end, we will seek to identify hatchery-reared individuals and quantify their relative contributions to reservoir populations. In so doing, we will then be able to understand differences in contribution at different ages (e.g., new recruits at ages 2-3 vs. old recruits at ages > 7), as well as how age-specific growth and life-history traits (e.g., longevity, maximum size) vary between wild and stocked fish. We will then seek to use environmental data (e.g., reservoir size, reservoir type, water temperature, prey availability, predator abundance) to explain among-reservoir differences in channel catfish demographics.

While no research appears to have examined these questions for any catfish population, we predict that wild-produced individuals will grow faster, live longer, and contribute more to fisheries relative to hatchery-reared fish. Ancillary data from Carter-Lynn et al. (2015) in part support this hypothesis, as fish > age-8 were rarely seen in a completely stocked population, which is different from populations with wild reproduction in which fish > age-9 are common. We also expect that channel catfish density and prey abundance will influence growth rates (Michaletz 2009; Braun and Phelps 2016) with abiotic controls also being important. Finally, we expect to find among-reservoir variation in growth rate and abundance that is unrelated to source origin (i.e., wild vs. hatchery).

Understanding what drives channel catfish population demographics and how stocked individuals are assimilated into the fishable population across reservoirs will help the ODNR-DOW make stocking decisions, and ultimately producing better and more cost-effective fisheries.