Impacts of the alien mosquitofish on the abundance and condition of two Mediterranean native fish

Abstract

The rapid decline of the Greek native Valencia letourneuxi, and its recently described sister species Valencia robertae, has been often attributed to habitat degradation, as well as aggression from or resource competition with the alien mosquitofish Gambusia holbrooki. The mosquitofish is extremely wide-spread in Mediterranean freshwater ecosystems, however, documentation on its presumed negative impacts on native freshwater fishes is limited. In this study, we compared abundance, condition and gonad weight of Valencia spp. in no co-occurrence versus co-occurrence to the mosquitofish, using data collected from eight aquatic systems of Greece, over a five year period (2005 to 2009). Our results show that Valencia abundance is significantly lower in co-occurrence to the Eastern mosquitofish. Furthermore, female Valencia spp. individuals in co-occurrence to the mosquitofish were smaller in length and had poorer somatic condition compared to females in habitats not invaded by the mosquitofish. The mechanisms responsible for these effects of the alien mosquitofish as well as the conservation implications for native Valencia populations are discussed.

eDNA‐based monitoring: Advancement in management and conservation of critically endangered killifish species

“…Using our novel assays, we were able to highlight six sites where V. letourneuxi were found and six sites for V. robertae. These locations fell within the historical range of the targeted species but had steep banks, abundant vegetation cover, and/ or deep waters, making traditional surveying difficult (Kalogianni et al, 2010(Kalogianni et al, , 2019. Therefore, eDNA-based methods offer a noninvasive and safer alternative for monitoring these species, especially at locations which present difficulties of applying more traditional sampling methodologies.…”

“…Further, we intentionally targeted the killifishes preferred habitats in this study (spring-fed wetlands with clear waters and rich surface vegetation) and focused on sites which had known historical presence of the species (Kalogianni et al, 2010(Kalogianni et al, , 2019. This meant that the environment surveyed was largely uniform across the various samples.…”

“…Once widely distributed in Western Greece (Barbieri, Daoulas, Psarras, Stoumboudi, & Economou, 2000), the distribution ranges of the two native species have now been drastically reduced over the last 40 years. This decline has been linked to anthropogenic habitat modification and competition from the non‐native Eastern mosquitofish G. holbrooki (Kalogianni et al., 2010, 2019). G. holbrooki is originated from the United States and Mexico and is now widespread throughout much of Southern Europe where it was introduced in the early 1920s (Piria et al., 2018; Ribeiro & Leunda, 2012).…”

Ecological particularities of the critically endangered killifish Valencia letourneuxi and its spring-fed habitats: a long-lost endemic species of south Albania

“…It was also classified as Critically Endangered by the IUCN, based on restricted distribution, suspected population decline and projected decline in the coming decade, as well as due to impacts of introduced alien species (Crivelli, 2006).The species is included in the Greek Red list of threatened species (Legakis and Maragou, 2009) but not on the Albanian Red list due to data deficiency. To ensure the conservation of the species, coordinated conservation initiatives in Greece and Albania are urgently required to mitigate the impacts of habitat degradation and of competition with the alien Eastern mosquitofish Gambusia holbrookiare (Barbieri et al, 2015;Kalogianni et al, 2019), including considerations of the establishment of NATURA 2000 sites in Albania (Shumka, 2019).…”

New horizons for the Panhellenic Symposium of Oceanography & Fisheries

“…• The freshwater fish species of Valencia spp. are investigated byKalogianni et al (2019) and, in particular, whether the abundance of the species and their somatic condition in habitats co-occurring with the Eastern mosquitofish and in others without, differ. Their study has been carried out in eight Greek freshwater ecosystems.Section 3: The marine abiotic environment • De Ruijter et al (2019) provide results of their study on the bathymetric distribution of microplastics in the shallow sediments of Samos Island (Aegean Sea, Greece).…”