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Effectiveness of Bowfin as a Predator on Bluegill in a Vegetated Lake
Author(s) -
Mundahl Neal D.,
Melnytschuk Christina,
Spielman Deena K.,
Harkins Jason P.,
Funk Kate,
Bilicki Andrew M.
Publication year - 1998
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 - 10.1577/1548-8675(1998)018<0286:eobaap>2.0.co;2
Subject(s) - lepomis , pimephales promelas , electrofishing , biology , predation , minnow , lepomis macrochirus , fishery , stocking , macrophyte , centrarchidae , population , ecology , predator , dorosoma , fish <actinopterygii> , micropterus , demography , sociology
Adult bowfins Amia calva were reintroduced (initial density approximately 32 fish/ha) into Lake Winona, Minnesota, from 1984 to 1986 to evaluate their effectiveness in controlling overabundant, stunted bluegills Lepomis macrochirus and other sunfishes (centrarchids) in a system with extensive macrophyte beds. Bowfin catch rates (trap nets, gill nets and electrofishing) declined rapidly after reintroductions ended in 1986. Catch rates and growth rates of bluegill and black crappie Pomoxis nigromaculatus have not changed since bowfin reintroduction. In 1992, only adult bowfins (average age, 10 years; average weight, 2.4 kg) were captured in Lake Winona, and they were concentrated in or near dense macrophyte beds. The final population estimate for bowfin in the west basin was 114 fish (3.17 fish/ha). Captive bowfins exhibited no size selection when feeding on sunfish and consumed on average less than 5 sunfish/24 h. Bowfin consumption rates declined by 80% when the density of artificial vegetation exceeded 500 stems/m 2 . Bowfins preferred both fathead minnows Pimephales promelas and virile crayfish Oronectes virilis over sunfish in prey choice trials. Lack of natural reproduction by bowfins in Lake Winona, their rapid decline in numbers after stocking, and their low rate of sunfish consumption may explain why bowfins apparently have been ineffective in controlling the lake's bluegill population.