Hypoxia tolerance of two centrarchid sunfishes and an introduced cichlid from karstic Everglades wetlands of southern Florida, U.S.A.

Authors

  • P. J. Schofield,

    Corresponding author
    1. * U.S. Geological Survey, Florida Integrated Science Center, 7920 NW 71st Street, Gainesville, FL 32653, U.S.A. and U.S. Geological Survey, Florida Integrated Science Center, Everglades National Park Field Station, 40001 State Road 9336, Homestead, FL 33034, U.S.A.
      †Tel.: +1 352 264 3530; fax: +1 352 378 4956; email: pschofield@usgs.gov
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  • W. F. Loftus,

    1. * U.S. Geological Survey, Florida Integrated Science Center, 7920 NW 71st Street, Gainesville, FL 32653, U.S.A. and U.S. Geological Survey, Florida Integrated Science Center, Everglades National Park Field Station, 40001 State Road 9336, Homestead, FL 33034, U.S.A.
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  • M. E. Brown

    1. * U.S. Geological Survey, Florida Integrated Science Center, 7920 NW 71st Street, Gainesville, FL 32653, U.S.A. and U.S. Geological Survey, Florida Integrated Science Center, Everglades National Park Field Station, 40001 State Road 9336, Homestead, FL 33034, U.S.A.
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†Tel.: +1 352 264 3530; fax: +1 352 378 4956; email: pschofield@usgs.gov

Abstract

In this study, the hypoxia tolerance of three Everglades fishes, two native centrarchids (Lepomis gulosus and Lepomis marginatus) and a recently introduced cichlid (Hemichromis letourneuxi), were documented. Aquatic surface respiration (ASR) thresholds were lowest for H. letourneuxi, followed by L. gulosus, then L. marginatus. The ASR thresholds for L. marginatus were within ranges reported for small, freshwater tropical fishes, while those for L. gulosus were similar to swamp-adapted fishes. For H. letourneuxi, ASR thresholds were some of the lowest reported. All three species showed excellent tolerance of low dissolved oxygen levels when allowed access to the surface. When denied surface access, L. marginatus lost equilibrium at a higher oxygen tension than the other species. Overall, although all species easily tolerated hypoxia, H. letourneuxi appeared to be best equipped to deal with hypoxia, followed by L. gulosus, then L. marginatus. Hemichromis letourneuxi also exhibited more aggressive behaviours than the centrarchids. These results suggest that hypoxia is not likely to prevent H. letourneuxi from exploiting the seasonally inundated wetlands of south Florida while expanding its range there.

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