Complex interactions between native and invasive fish: the simultaneous effects of multiple negative interactions

Abstract

We suggest that the ultimate outcome of interactions between native species and invasive species (extinction or coexistence) depends on the number of simultaneous negative interactions (competition and predation), which depends on relative body sizes of the species. Multiple simultaneous interactions may constrain the ability of native species to trade fitness components (i.e., reduced growth for reduced risk of predation) causing a spiral to extinction. We found evidence for five types of interactions between the adults and juveniles of introduced western mosquitofish (Gambusia affinis) and the juveniles of native least chub (Iotichthys phlegethontis). We added ten large (23-28 mm) and seven small (9-13 mm) young-of-the-year (YOY) least chub to replicate enclosures with zero, low, and high densities of mosquitofish in a desert spring ecosystem. Treatments with mosquitofish reduced the average survival of least chub by one-third. No small YOY least chub survived in enclosures with high mosquitofish densities. We also performed two laboratory experiments to determine mortality to predation, aggressiveness, and habitat selection of least chub in the presence of mosquitofish. Mean mortality of least chub due to predation by large mosquitofish was 69.7% over a 3-h trial. Least chub were less aggressive, selected protected habitats (Potamogeton spp.), and were more stationary in the presence of mosquitofish where the dominance hierarchy was large mosquitofish>>large least chub approximately small mosquitofish>>small least chub. Least chub juveniles appear to be figuratively caught in a vice. Rapid growth to a size refuge could reduce the risk of predation, but the simultaneous effects of competition decreased least chub growth and prolonged the period when juveniles were vulnerable to mosquitofish predation.

Trophic overlap between cohabiting populations of invasive mosquitofish and an endangered toothcarp at changing salinity conditions

“…In addition, other studies have demonstrated that interaction with mosquitofish causes alterations in the biological parameters of native species, such as growth or recruitment (e.g. Howe et al 1997, Mills et al 2004). …”

Expansión del alburno <i>Alburnus alburnus</i> (Linnaeus, 1758) (Actinopterygii, Cyprinidae) en la península Ibérica: el papel de los embalses

“…The negative effects of invasive fish species on native fish, communities and ecosystems is widely recognized (Cambray, 2003;Mills et al, 2004). The impact of an invader like the bleak needs to be assessed at different levels: genetic pool (hybridization), individuals (changes in life history and behaviour), populations (changes in abundance and distribution of native fish species) and communities (competition, species richness, diversity and trophic structure).…”

Changes in range-wide distribution of plains topminnow Fundulus sciadicus

“…In addition to the intro duction of non-native predatory sport fish, riverine environments have often experienced shifts in species assemblages towards non-native generalist species (Fischer & Paukert 2008). One such species that has been widely implicated in declines of native species is the western mosquitofish Gambu- (Lynch & Roh 1996, Haas 2005 and has affected species assemblages through predation, competition and harassment, leading to the reduction and elimination of fish species, aquatic invertebrates and amphibian communities around the world (Meffe 1985, Moyle 2002, Mills et al 2004, Zeiber et al 2008. Whether the western mosquitofish threatens the plains topminnow is not clear.…”

“…The western mosquitofish has been implicated in the reduction of plains topminnow populations (Lynch & Roh 1996, Haas 2005 and has affected species assemblages through predation, competition and harassment, leading to the reduction and elimination of fish species, aquatic invertebrates and amphibian communities around the world (Meffe 1985, Moyle 2002, Mills et al 2004, Zeiber et al 2008. Whether the western mosquitofish threatens the plains topminnow is not clear.…”