Behavioural response of fishes to increasing pH and dissolved oxygen: field and laboratory observations


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Freshwater fish assemblages were sampled before, during and after naturally-produced conditions of elevated pH and dissolved oxygen (DO) that occurred for 2-6 h in two dense macrophyte beds. Field observations were followed by 3-4-h laboratory behavioural experiments in which banded killifish Fundulus diaphanus, bluegill Lepomis macrochirus and striped bass Morone saxatilis were exposed to gradually increasing levels of pH, DO, and pH and DO together. The macrophyte bed dominated by Hydrilla verticillata had a higher fish density than the mixed-species (H. verticillata and Vallisneria americana) beds, but beds did not differ significantly in fish species richness or biomass. Within beds, diel changes in fish species composition, richness, density and biomass were minor. In the laboratory, avoidance of pH >9.5 was exhibited by all species tested. No significant response was observed to either DO increase treatments, or to pH and DO increase treatments. Results suggest fishes do not avoid areas, such as dense macrophyte beds, when high pH levels (9.5-10.0) are accompanied by high DO levels (200-260% saturation). -Authors

Original languageEnglish (US)
Pages (from-to)53-61
Number of pages9
JournalFreshwater Biology
Issue number1
StatePublished - Aug 1993

ASJC Scopus subject areas

  • Aquatic Science


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