Age and length at maturity among populations of channel catfish considering influence of environmental variables and implications for sustainable management of slat basket fisheries

Floodplain river populations of channel catfish Ictalurus punctatus form the basis of a significant public fishery in Mississippi. This study addressed user concern that some commercial fishing gears might have a detrimental impact on such populations. The relative efficiency and selectivity of these gears was investigated. The project also related biological stock descriptors for channel catfish to characteristics of the watershed environment and expanded understanding of floodplain rivers as a dynamic terrestrial-aquatic interface. Wild channel catfish (N = 1,299) were collected from 10 rivers and two lentic systems in Mississippi during 2001/2002 using slat traps, trotlines, hoopnets and angling. Slat traps had two throats, were 1.8 min length, 38 cm in width and had four interslat spaces of 3.8 by 61 cm. Trotlines were 10 m in length with hooks 1 m apart. Hoopnets were 4.3 m long, had seven hoops of 1.07 m diameter, and were constructed of 3.81 cm bar mesh. Catch per unit effort (CPUE; fish/gear-night) did not differ among slat traps, trotlines and hoopnets, but differed among systems. A comparable unit of effort for angling was not defined. Trotlines caught more fish longer than 500 mm total length (TL) than slat traps but no differences in catch of smaller fish were detected. Angling caught more fish <300 mm TL than any other gear. Size selection of channel catfish varied among slat traps having different interslat space widths. A 3.8-cm slat trap had a 50% retention length for channel catfish of 392 mm. These data indicate that slat traps don't impact channel catfish populations more than do trotlines or angling.; All channel catfish were aged using pectoral spines and growth was compared among rivers. Mean back-calculated length at age differed among rivers and was related significantly to watershed soil fertility and elevation above sea level. Growth of channel catfish in all rivers was best modeled by a Gompertz curve. The parameters of the curve were related significantly to slat trap CPUE, a surrogate for population density. Slat trap CPUE in rivers was correlated positively with the proportion of the watershed comprised of bottomland hardwood forest.; Length at maturity of channel catfish did not differ among rivers; hence the statewide application of a minimum length limit (MLL) in Mississippi is appropriate. However, the length when channel catfish (N = 271) from all rivers combined attained 50% probability of sexual maturity was 384 mm, suggesting that the current MLL of 300 mm in the commercial fishery may be too small. Channel catfish from the Sunflower River matured younger than fish from the Buttahatchee, Noxubee and Pearl rivers. Sunflower River fish also showed rapid growth and large asymptotic size.