Dilution stress facilitates colonization of invasive mosquitofish in a saline Mediterranean stream: population biology response

Abstract

1. Knowledge of the interplay of abiotic factors and the invasive success of exotic fish is fundamental both to proper management and the ability to predict consequences for native communities.2. The highly invasive eastern mosquitofish (Gambusia holbrooki) has been introduced worldwide; however, although salinity could limit its invasive success, the influence of variations in water salinity on its population biology has been scarcely studied.3. The present study aimed to analyse the effect of changes in water salinity on the life history and microhabitat use of a mosquitofish population inhabiting a hypersaline stream subjected to human-caused dilution stress.4. Dilution process and associated habitat changes, such as increased aquatic vegetation, available food and the spread of invasive riparian vegetation (the common reed Phragmites australis), seem to have favoured mosquitofish proliferation and colonization. 5. Dilution caused an increased somatic condition for all individuals and a higher reproductive investment of males and larger females. This led to greater survival, recruitment rates, and abundance during the period of lower salinity.6. The species showed changes in microhabitat use which could be advantageous in less saline conditions; for instance, the species preferentially used areas with the presence of P. australis as a refuge, and this pattern increased during the dilution period.7. These results support the hypothesis that human activity is one of the main forces shaping the colonization and proliferation of exotic freshwater fishes. At least in a Mediterranean context, an increase in mosquitofish abundance and the improvement of its population status could be clear indicators of the degradation of natural saline systems.

Pushed to the edge: Environmental factors drive ecological responses of Aphanius fasciatus when in sympatry with invasive Gambusia holbrooki

“…In the most extreme and stressed environments, killifish is able to survive and persist, with both salinity and the presence of the invader representing two factors acting synergistically in characterizing and shaping the distribution patterns of the native species. This difference in response to salinity between the two species is consistent with their ecological characteristics and previous studies: It is known that salinity is a major limiting factor for mosquitofish (Alcaraz & García‐Berthou, 2007; Ruiz‐Navarro et al, 2013), whereas killifish has a much higher tolerance to hyperhaline conditions (Bianco, 1995). It has been reported that the highest salinity tolerated by mosquitofish is 58.5‰ for 30 days (Ruiz‐Navarro et al, 2011), which is approximately equivalent to the highest values where the species was found in this study; however, reports of mosquitofish in hyperhaline conditions are very limited in the scientific literature (Alcaraz & García‐Berthou, 2007).…”

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

“…Among others, its tolerance to high temperature, acid and basic pH, or low dissolved oxygen (Homski et al 1994, Pyke 2008 can be highlighted. Mosquitofish is also able to survive a wide range of salinities (Purcell et al 2008), and even established mosquitofish populations have been de scribed in eusaline and hypersaline waters (Alcaraz & García-Berthou 2007a, Ruiz-Navarro et al 2011, 2013. However, salinity is one of the most stressful factors in the viability of mosquitofish populations, and the disrupting effects of salinity on the species' biology have been described (Alcaraz & García-Berthou 2007a, Ruiz-Navarro et al 2013).…”

“…Mosquitofish is also able to survive a wide range of salinities (Purcell et al 2008), and even established mosquitofish populations have been de scribed in eusaline and hypersaline waters (Alcaraz & García-Berthou 2007a, Ruiz-Navarro et al 2011, 2013. However, salinity is one of the most stressful factors in the viability of mosquitofish populations, and the disrupting effects of salinity on the species' biology have been described (Alcaraz & García-Berthou 2007a, Ruiz-Navarro et al 2013). Tolerance to salinity is wider in Iberian toothcarp, and, in fact, its current distribution is mostly concentrated in saline aquatic systems (Oliva-Paterna et al 2006, Alcaraz & García-Berthou 2007a, Alcaraz et al 2008b.…”

Climatic and geographic variation as a driver of phenotypic divergence in reproductive characters and body sizes of invasive Gambusia holbrooki

“…However, lower salinity levels were also reported to induce higher reproductive effort of males and larger females, and resulted in higher survival and recruitment rates, suggesting some complexity in the interaction of salinity with Gambusia spp. population dynamics (Ruiz-Navarro et al 2013). Nevertheless, the expression of larger male gonopodia and smaller body sizes of both sexes in our coastal areas might again be related to higher population abundances that were enabled by the likelihood that the abiotic characteristics of these waters included relatively high salinity levels versus the populations further inland.…”