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Responses of Largemouth Bass and Bluegills to Removal of Surplus Largemouth Bass from a Kansas Pond
Author(s) -
Gabelhouse Donald W.
Publication year - 1987
Publication title -
north american journal of fisheries management
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.587
H-Index - 72
eISSN - 1548-8675
pISSN - 0275-5947
DOI - 10.1577/1548-8659(1987)7<81:rolbab>2.0.co;2
Subject(s) - bass (fish) , electrofishing , micropterus , fishery , hectare , biology , zoology , fish <actinopterygii> , ecology , agriculture
A slot length limit of 30‐38 cm was imposed on largemouth bass (Micropterus salmoides) in a Kansas pond to improve the species' population structure. In conjunction with this limit, 62‐91 largemouth bass 20‐30 cm long were removed annually per hectare from 1979 to 1983 via electrofishing to simulate what was considered an appropriate harvest. Both the electrofishing catch rate and estimated number of 20‐30‐cm largemouth bass in 1982 were less than half that of 1979. Largemouth bass 30‐38 cm long were estimated to be twice as abundant in 1983 as they were in 1979, and over three times as many fish of this size were captured per hour of electrofishing in 1983 as were collected in 1979. Biomass of largemouth bass 20‐30 cm long decreased by nearly one‐half and the weight of 30‐38‐cm largemouth bass more than doubled from 1979 to 1983. Only modest improvements in growth rates occurred and condition factors remained less than satisfactory, probably because the removal amounted to less than one‐fourth of the estimated number and less than one‐third of the estimated biomass of small largemouth bass present in the first 2 years of the study; density of surviving bass 20‐30 cm long was 229 or more per hectare. As a result, largemouth bass 38 cm and longer were not found until 1983, and then only 3% of all largemouth bass 20 cm and longer were of this size. Bluegill (Lepomis macrochirus) recruitment increased, probably due in part to decreased largemouth bass predation. In addition, electrofishing catch rates for bluegills 20 cm and longer increased annually and were over four times higher in 1983 than in 1979. This increase was due to lower mortality rates among age III and older bluegills. Increased longevity of bluegills and their continued good growth and condition, despite increased density, indicated that the removal of largemouth bass may have reduced competition for food between largemouth bass less than 30 cm long and bluegills 15 cm and longer. It may be difficult sometimes to remove sufficient numbers of small largemouth bass to produce a balanced population of this species in situations of high recruitment, but fisheries managers should strive to maintain a proportional stock density of 20‐40 and a relative weight of 85‐95 for largemouth bass if there is interest in maximizing the production of large bluegills.