Niche complementarity between an alien predator and native omnivorous fish in the Wilge River, South Africa

Abstract

A major challenge in biological invasions is to predict community susceptibility to invasion. This study investigated trophic interrelationships between an alien predator, largemouth bass (Micropterus salmoides) and native omnivores sharptooth catfish (Clarias gariepinus) and largescale yellowfish (Labeobarbus marequensis) in an invaded aquatic system to elucidate factors that might have aided their successful establishment. It tested the hypothesis that M. salmoides is able to co-exist with the two native omnivores by either utilizing a previously vacant food niche or through niche complementarity. Gut content and stable isotope analyses were used to determine trophic interactions. There was no evidence that M. salmoides was utilizing a previously vacant food niche but instead it occupied a restricted and specialized niche within a broad niche space utilized by the native omnivores. Differences in niche space and size have resulted in minimal niche overlaps that imply niche complementarity. The introduction of M. salmoides raises concerns about increases in predation pressure in the system. This however, is difficult to ascertain because of complexities in measuring long-term trends in predator demands, abundance and community compensation mechanisms. There is a need for long-term monitoring of community structure, especially small-sized prey species that are vulnerable to increased predation pressure.

Ecological Niche Space of Fish Communities in Impounded Sections of Large Rivers: Its Application to Assessment of the Impact of Weirs on River Ecosystems

“…This may have a positive impact on omnivores. The trophic level of largemouth bass decreases in upstream locations, which suggests that they may become more omnivorous by selecting prey from lower trophic levels [41]. The predatory carp E. erythropterus is also known to feed on benthic invertebrates and juvenile fish.…”

Niche expansion by indigenous fish species following the introduction of rainbow trout (Oncorhynchus mykiss) in a subtropical river system, upper Blyde River, South Africa

“…Muscle tissue was excised from all fish samples while insects were analysed whole following similar studies done in the region (e.g., Lübcker et al, 2016;Taylor et al, 2017;Lombard et al, 2018;Bokhutlo et al, 2021). Insects were combined so that they included representatives from the following seven orders: Coleoptera, Diptera, Ephemeroptera, Hemiptera, Lepidoptera, Odonata and Trichoptera.…”

Trophic ecology of co‐occurring fishes in the Sundays River Valley irrigation ponds, assessed using stable isotope and gut content analyses

“…The introduction of fish through human actions can have negative effects on recipient systems (Nati et al ., 2018; Vitousek et al ., 1997). The negative effects of introduced fish include biodiversity loss (Ellender & Weyl, 2014), biotic homogenisation, introduction of pathogens, hybridisation and the destabilisation of native freshwater communities and food webs through biological interactions, such as consumptive and non‐consumptive effects (Lombard et al ., 2017; Mofu, South, et al ., 2019a; Wasserman et al ., 2016). The introduction of alien species in new environments is driven by many factors, such as inter‐basin water transfer schemes, biological control, aquaculture and sport fishing (Cambray, 2003; Chapman et al ., 2019; Pimentel et al ., 2005).…”