Gear and seasonal bias associated with abundance and size structure estimates for lentic freshwater fishes

Journal of Fish and Wildlife Management
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Abstract

All freshwater fish sampling methods are biased toward particular species, sizes, and sexes and are further influenced by season, habitat, and fish behavior changes over time. However, little is known about gear-specific biases for many common fish species because few multiple-gear comparison studies exist that have incorporated seasonal dynamics. We sampled six lakes and impoundments representing a diversity of trophic and physical conditions in Iowa, USA, using multiple gear types (i.e., standard modified fyke net, mini-modified fyke net, sinking experimental gill net, bag seine, benthic trawl, boat-mounted electrofisher used diurnally and nocturnally) to determine the influence of sampling methodology and season on fisheries assessments. Specifically, we describe the influence of season on catch per unit effort, proportional size distribution, and the number of samples required to obtain 125 stock-length individuals for 12 species of recreational and ecological importance. Mean catch per unit effort generally peaked in the spring and fall as a result of increased sampling effectiveness in shallow areas and seasonal changes in habitat use (e.g., movement offshore during summer). Mean proportional size distribution decreased from spring to fall for white bass Morone chrysops, largemouth bass Micropterus salmoides, bluegill Lepomis macrochirus, and black crappie Pomoxis nigromaculatus, suggesting selectivity for large and presumably sexually mature individuals in the spring and summer. Overall, the mean number of samples required to sample 125 stock-length individuals was minimized in the fall with sinking experimental gill nets, a boat-mounted electrofisher used at night, and standard modified nets for 11 of the 12 species evaluated. Our results provide fisheries scientists with relative comparisons between several recommended standard sampling methods and illustrate the effects of seasonal variation on estimates of population indices that will be critical to the future development of standardized sampling methods for freshwater fish in lentic ecosystems.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Gear and seasonal bias associated with abundance and size structure estimates for lentic freshwater fishes
Series title Journal of Fish and Wildlife Management
DOI 10.3996/082013-JFWM-054
Volume 5
Issue 2
Year Published 2014
Language English
Publisher Scientific Journals
Contributing office(s) Coop Res Unit Seattle
Description 19 p.
First page 394
Last page 412
Country United States
State Iowa
Other Geospatial Don Williams Lake, Lake Minnewashta, Pleasant Creek Lake, Prairie Rose Lake, Silver Lake, West Okoboji Lake