Habitat structure differentially mitigates predation impact of juvenile largemouth bass and Florida bass

Abstract

Habitat complexity plays an important role in structuring species diversity, behaviour and distribution. Furthermore, habitat complexity can mediate the strength of predator-prey interactions through the provision of prey refugia or through enhancing ambush predation. In this study, we use functional responses (FRs) to compare the effect of habitat complexity on resource utilisation between Largemouth Bass Micropterus salmoides and Florida Bass Micropterus floridanus predating upon Mozambique Tilapia Oreochromis mossambicus fry. Treatments for this study were zero and high habitat complexities, with the latter being artificially constructed using plastic strips. Both predator species exhibited a Type II FR in both habitat complexities, with Florida Bass exhibiting significantly higher FR magnitudes, compared with Largemouth Bass under both habitat complexities. Both species experienced dampening of FR magnitudes under high habitat complexity. Florida Bass had persistently lower handling parameters than Largemouth Bass regardless of habitat complexity. While higher habitat complexity may offer prey refugia from Florida Bass, changes in complexity had a negligible effect upon Largemouth Bass predatory efficiency. Measures to enhance natural complexity through system restoration may be a useful conservation measure for endemic fish in rivers invaded by Florida Bass, however, the same mitigation measures may not be as effective for Largemouth Bass.

Keywords:

• functional response
• habitat complexity
• invasion biology
• South Africa