Abstract
Introductions of alien freshwater fish species into the Mediterranean-climatic South-west Coast Drainage Division of Australia have impacted a highly endemic (≈82%) yet depauperate (11 species) native freshwater fish fauna. This study updates the current known introduced freshwater fishes in Western Australia, assesses the historic rate of introductions and how habitat, water quality and climatic changes have facilitated those introductions. South-western Australia has undergone a ≈63% increase in alien freshwater fish introductions since 1970 (44% increase over the past decade) to 13 species; overtaking the number of native fishes. Aquarium species represent 80% of the latest introductions (46% of total number) and the majority (54%) of introduced fishes in the region are of sub-tropical or tropical origin. As found elsewhere, species with broad environmental tolerances and generalist diets are likely to continue to be the main colonizers in this region. We propose that past and future climatic and habitat changes in the Mediterranean-climatic south-west region will facilitate continued invasion of tropical and sub-tropical aquarium fishes and that strategic monitoring, control and public education programs are required to halt future introductions.
Highlights
The rate of non-native freshwater fish introductions has doubled in the past 30 years driven primarily by aquaculture and attempts to improve wild stocks (Gozlan 2008; Gozlan et al 2010)
Since 1970, there has been an increase of ≈63% in the number of known introduced freshwater fish species recorded in this region, with the past decade seeing an ≈44% increase (Table 1, Figure 2)
The rate of increase in Western Australia approximates the global increase in freshwater fish introductions that have doubled in the past ≈30 years (Gozlan 2008; Gozlan et al 2010)
Summary
The rate of non-native freshwater fish introductions has doubled in the past 30 years driven primarily by aquaculture and attempts to improve wild stocks (Gozlan 2008; Gozlan et al 2010). Aquaculture and wild stock enhancements are key vectors driving freshwater fish introductions (Gozlan et al 2010); another key vector has been aquarium releases Marr et al (2010) demonstrated that 76 species of freshwater fishes had been introduced to the five Mediterranean climate regions with four orders having been introduced to all of those regions (i.e. Cypriniformes (16 species), Cyprinodontiformes (10 species), Perciformes (26 species), and Salmoniformes (nine species)). There has been an 8% overall increase in the similarities of the freshwater fish fauna of Mediterranean-climatic regions due to those nonnative introductions (Marr et al 2010). Homogenisation of the Australian freshwater fish fauna due to species introductions has been demonstrated (Olden et al 2008). The introduction of the common carp Cyprinus carpio Linnaeus, 1758 and eastern gambusia Gambusia holbrooki (Girard, 1859) to the Lake Eyre and the South-west Coast Drainage Divisions has resulted in a present-day similarity of 7.3%, when historically they shared no species
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