Freshwater fish introductions in mediterranean‐climate regions: are there commonalities in the conservation problem?

Abstract

Aim To compare patterns and drivers of freshwater fish introductions across five climatically similar regions and evaluate similarities and differences in the non‐native species introduced. Location Five mediterranean‐climate regions: California (USA), central Chile, south‐western Australia, the Iberian peninsula (Spain and Portugal) and the south‐western Cape (South Africa). Methods Species presence–absence for native and non‐native fishes were collated across the regions, and patterns of faunal change were examined using univariate and multivariate statistical approaches. Taxonomic patterns in freshwater fish introductions were evaluated by comparing the number of species introduced by order to the numbers expected from binomial probabilities. Factors influencing multiple introductions of freshwater fish species in mediterranean regions were determined using generalized linear modelling. Results High levels of endemism (70–90%) were revealed for south‐western Cape, south‐western Australia and Chile. Despite their high rates of endemism, all regions currently have more non‐native species than endemic species. Taxonomic selection was found for five orders, although this was only significant for Salmoniformes across regions. The average increase in regional compositional similarity of fish faunas resulting from non‐native fish introductions was 8.0%. Important factors predicting multiple introductions of a species include previous introduction success and mean latitude of its distribution Main conclusions The mediterranean‐climate regions of the world, separated by vast distances, originally had a few fish species in common but are now more similar, owing to species introductions, illustrating the extent and importance of taxonomic homogenization. Introductions are largely driven by taxonomically biased human interests in recreational fisheries, aquaculture and ornamental pet species.

Escaped farmed salmon and trout in Chile: incidence, impacts, and the need for an ecosystem view

“…It is also important to evaluate and develop reliable indicators to estimate their impact on native species and ecosystems, as well as their social and economic impact in both marine and freshwater ecosystems (Velásquez et al 2011). For example, to test broad-scale hypo theses about taxonomic homogenization and expansion of introduced species, a paired comparison be tween historical and current presence/ absence of both native and introduced species appears to be a useful tool (Marr et al 2010(Marr et al , 2013.…”

Evaluating taxonomic homogenization of freshwater fish assemblages in Chile

“…We employed pairwise estimates of compositional similarity (CS) between watersheds from historical (CS his ) and current similarities (CS cur ) in fish composition using Sørensen's index (Sørensen 1957), one of most commonly used indices to infer TH (see Olden et al 2008;Leprieur et al 2008;Marr et al 2010Marr et al , 2013. Prior to estimating Sørensen index, presenceabsence data underwent a square root transformation and a double Wisconsin standardization (Oksanen et al 2011).…”

“…Our expectation was that introduced species with wide distributions might have a larger influence in TH than those with narrow distributions, which conversely are more likely to drive TD. These processes are likely to be driven by similar fish taxa because of convergent human interests around the globe (e.g., salmonids, cyprinids, and poeciliids : Ruesink 2005;Clavero and García-Berthou 2006;Marr et al 2010;Marr et al 2013). To our knowledge, this is the first attempt to broadly evaluate TH in Chile (but see Marr et al 2010), thus permitting assessments of changes in the freshwater fish fauna in order to evaluate current implications for conservation and aid policy-making decisions.…”

“…Biotic homogenization between communities represents a major biogeographic and ecological threat for biodiversity at a regional and global scale Rooney et al, 2004;Olden 2006;Olden and Rooney 2006;Marr et al 2010Marr et al , 2013. This phenomenon might include loss of taxonomic, functional, or genetic differentiation (Olden 2006).…”

“…Human-mediated introductions of species have been a key factor leading to diversity losses in these systems (Clavero and García-Berthou 2006). Fishes are in particular among the most documented introduced species around the world (Rahel 2000) due to aquaculture, recreational fisheries, biological control, and ornamental uses (Ruiz and Marchant 2004;Vargas et al 2010;Marr et al 2010Marr et al , 2013. Biogeographic and ecological approaches to quantify changes in fish communities over time have thus emerged as fundamental means to understanding global as well as local issues involving non-native fishes and their effects upon native aquatic biota, and to illuminate conservation implications as a result Marr et al 2010;Habit et al 2010).…”