Transport pathways shape the biogeography of alien freshwater fishes in Australia

Abstract

Aim Changing preferences regarding which species humans have transported to new regions can have major consequences for the potential distribution of alien taxa, but the mechanisms shaping these patterns are poorly understood. We assessed the extent to which changes in human preferences for transporting and introducing alien freshwater fishes have altered their biogeography. Location Australia. Methods We compiled an up‐to‐date database of alien freshwater fishes established in drainages in Australia before and after the number of established alien fish species doubled (pre‐1970 and post‐1970, respectively). Using metacommunity models, we analysed the influence of species traits and drainage features on the distribution of alien fishes that established pre‐ and post‐1970. Results Alien fishes in Australia were introduced via four main transport pathways: acclimatization, aquaculture, biocontrol and ornamental trade. The relative importance of each pathway changed substantially between the two periods, accompanied by changes in the distribution of alien fishes and the variables predicting their distribution. Pre‐1970, most species (64%) were introduced by acclimatization societies for purposes such as angling and biocontrol, and these fish have established in inland drainages more heavily impacted by human activities. In contrast, most of the post‐1970 introductions (69%) were ornamental fishes, with most species established in small, north‐eastern, tropical and subtropical coastal drainages. Main conclusions Substantial changes in introduction preferences and transport pathways over time have altered both the patterns and underlying processes shaping the biogeography of alien fishes in Australia. Our findings highlight the need for caution when using historical data to infer potential future distributions of alien species. The continuing spread of alien species means traditional biogeographical units may no longer be identifiable in the foreseeable future.

Integrating dispersal along freshwater ecosystems into species distribution models

“…There is a lack of evidence for the inclusion of distance in our models. Effects of distance may have been negated by historical human introductions, as human activities have been shown to alter species distributions across large regions (García-Díaz et al, 2018;Peoples & Midway, 2018). However, the fact that slope metrics affect F I G U R E 6 Presence/absences of perch (Perca fluviatilis) compared to gradient measurements for the streams connecting lakes and their nearest source populations in lakes previously treated by the piscicide rotenone throughout Sweden (white) and in a selection of lakes throughout the Kautokeino drainage basin in northern Norway (grey).…”

“…There is a lack of evidence for the inclusion of distance in our models. Effects of distance may have been negated by historical human introductions, as human activities have been shown to alter species distributions across large regions (García‐Díaz et al., 2018; Peoples & Midway, 2018). However, the fact that slope metrics affect distributions speaks against this hypothesis.…”

Barriers to hybridisation and their conservation implications for a highly threatened Australian fish species

“…This implies that introductions of native fishes, particularly those belonging to widespread genera are likely to result in the loss of genetic integrity of native populations. The number of alien species released into Australian waterways continues to increase with aquarium species contributing to the increasing numbers (García‐Díaz et al, ; Lintermans, ; Whittington & Chong, ). When combined with the increased availability and popularity of Australian/New Guinean species the potential for native species to introgress with alien species increases.…”

“…Keeping Australian fish in aquariums, ponds and stock troughs is becoming increasingly popular (e.g., Australia New Guinea Fishes Association). Unfortunately, releases or escapes of alien ornamental fish has resulted in increasing numbers of these species becoming established in Australian waterways (García‐Díaz et al, ). Once established, these species are often spread further by secondary human movement such as bait buckets or stocking (Lintermans, ).…”

Ten complementary measures to assist with environmental watering programs in the Murray–Darling river system, Australia

“…In some instances, non‐native species may occupy a vacant habitat or trophic niche or disrupt the natural ecological functions that support native species (Finlayson ). Twelve of the 57 fish species present in the MDB are non‐native or translocated (Lintermans, ), with the majority established through acclimatisation prior to 1970 (García‐Díaz et al, ).…”