Article

Movement behaviour of alien largemouth bass Micropterus salmoides in the estuarine headwater region of the Kowie River, South Africa

Published in: African Zoology
Volume 50, issue 4, 2015 , pages: 263–271
DOI: 10.1080/15627020.2015.1079141
Author(s): Taryn S MurraySouth African Institute for Aquatic Biodiversity, South Africa, Mandla L MagoroSouth African Institute for Aquatic Biodiversity, South Africa, Alan K WhitfieldSouth African Institute for Aquatic Biodiversity, South Africa, Paul D CowleySouth African Institute for Aquatic Biodiversity, South Africa

Abstract

The movement behaviour of largemouth bass Micropterus salmoides in the estuarine headwater region of the Kowie River, South Africa, was investigated using passive acoustic telemetry. Ten adult fish were tagged and released in four discrete pools below a weir that precluded possible upriver migration. Their residency and movement patterns were monitored using 27 moored acoustic receivers spanning both riverine and estuarine habitats between January and November 2013. Small-scale movements ranging from 50 to 400 m occurred between pools in the headwater region, where tagged fish remained resident (did not leave their tagging pool) during the warmer (summer) months. The onset of autumn and winter correlated with declining water temperatures and half of the tagged largemouth bass made downstream excursions into the slightly warmer upper reaches of the estuary. The penetration of these alien piscivores into estuarine headwaters potentially provide additional predator pressure on the juveniles of migratory estuary-associated native marine fish species, which utilise these areas as nurseries. The presence of the alien fish in South African estuarine headwaters may impair the migration of juvenile fishes between the estuarine and freshwater environments.

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