Effects of Lake Basin and Fish Population Characteristics on Gill Net Catchability of Northern Pike

摘要

Understanding factors that affect catchability is important for interpreting catches from assessment netting. Population densities of northern pike Esox lucius ages two and older were compared with gill net catch rates of northern pike ages two and older in 16 north-central Minnesota lakes that varied in physical characteristics and northern pike populations. Catchabilities for multimesh experimental gill nets ranged from 0.162 to 1.217 ha/net among the lakes (mean=0.466 ha/net; SE=0.070). Characteristics of the lake basins pertaining to depth, particularly mean depth, were strongly related to gill net catchability. Catchability was greatest in deep, steep-sided basins, which tend to concentrate northern pike movement and gill net effort along shorelines. Because nets are size selective, some of the variation in catchability was also explained by differences in size structure of the northern pike populations.