Stewart, D.R. and J.M. Long. 2015. Growth and contribution of stocked channel catfish, Ictalurus punctatus (Rafinesque 1818); the importance of measuring post-stocking performance. Journal of Applied Ichthyology 31:695-703. doi:10.1111/jai.12797.
Natural recruitment of channel catfish Ictalurus punctatus is limited in impoundments and stock enhancement is commonly used by state agencies to maintain fisheries. Advanced size fingerlings (> 175 mm total length (TL)) can be costly to rear, but survival is greater and their effectiveness has not been extensively studied for larger impoundments (> 200 ha). We evaluated stocking success of advanced size channel catfish marked with oxytetracycline (OTC) in two Oklahoma impoundments (Lakes Lone Chimney and Greenleaf). Channel catfish were marked in a solution of 700 mg L-1 of OTC for 6 hr, stocked at 178 mm TL, and both lakes sampled from May to August 2011 and 2012. Survival and marking success was high (100%), but the response to stocking, measured by relative abundance (CPUE, number of per 3-d tandem hoop net series), stocking contribution, and growth, was significantly different between the two impoundments. The differences are likely contributed to the different relative abundances between lakes Lone Chimney (80.5 fish series-1) and Greenleaf (9 fish series-1). Consequently, stocking contribution was lower at Lake Lone Chimney (3-35%) than at Lake Greenleaf (84-98%); however, relative abundance only increased at Lake Greenleaf. Average length and weight of stocked fish at age-2 only reached 230 mm TL and 85 g in Lake Lone Chimney, whereas fish stocked in Lake Greenleaf reached sizes of 340 mm TL and 280 g. The use of population indices like proportional size distribution (PSD) may misguide fishery managers as this value decreased at both reservoirs post-stocking, indicating that stocked fish contributed to the sample. But, because we could distinguish between wild and stocked fish using OTC, we were able to determine that stocking was not successful at Lake Lone Chimney. By batch-marking fish, a more direct assessment of stocking success was obtained and this option is viable for future studies.