Risk assessment model for the import and keeping of exotic freshwater and estuarine finfish Mary Bomford and Julie Glover June 2004 A report produced by the Bureau of Rural Sciences for The Department of Environment and Heritage © Commonwealth of Australia 2004 This work is copyright. Apart from any use as permitted under the Copyright Act 1968, no part may be reproduced by any process without prior written permission from the Commonwealth available from the Department of Communications, Information Technology and the Arts. Requests and inquiries concerning reproduction and rights should be addressed to the Commonwealth Copyright Administration, Intellectual Property Branch, Department of Communications, Information Technology and the Arts, GPO Box 2154, Canberra ACT 2601 or at http://www.dcita.gov.au/cca. The Australian Government acting through the Bureau of Rural Sciences has exercised due care and skill in the preparation and compilation of the information and data set out in this publication. Notwithstanding, the Bureau of Rural Sciences, its employees and advisers disclaim all liability, including liability for negligence, for any loss, damage, injury, expense or cost incurred by any person as a result of accessing, using or relying upon any of the information or data set out in this publication to the maximum extent permitted by law. Postal address: Bureau of Rural Sciences GPO Box 858 Canberra, ACT 2601 2 Foreword Exotic fish introduced into Australia can establish wild pest populations that cause environmental and economic harm. Predatory fish have the potential to cause extinctions of native fish species or reduce their range and abundance. Exotic fish can also compete with native fish for food and other resources. Other harm potentially caused by exotic fish includes altering the habitat of native species, spreading diseases and hybridising with native fish. There is a risk that new exotic fish species could establish as wild pests in Australia. If such fish escaped or were illegally released into a favourable environment, they could start to breed in the wild and spread to new locations. Once they are widespread, eradication becomes virtually impossible. Not all exotic fish species pose the same level of threat for establishing a wild pest population. This report addresses the question of whether it is possible to distinguish between species that pose a high risk and those that pose a lower risk. Based on a review of world scientific literature and an analysis of past introductions of exotic fish to Australia, it concludes that there is a suite of factors that separates high and low- risk species. This information is used to construct a scientifically based risk assessment model to evaluate the risk that an exotic fish species released into the wild could establish a wild population. The Bureau of Rural Sciences produced this report for The Department of Environment and Heritage with funding from the Natural Heritage Trust. The report provides information to assist the Commonwealth and State and Territory Governments assess the risks posed by the import and keeping of exotic fish. Dr Peter O’Brien Executive Director Bureau of Rural Sciences 3 4 Summary On average, around 50% of reported exotic fish introductions have resulted in new populations establishing although this figure varies between fish taxa and in different locations. This figure Around 50% of may overestimate the true success rate because successful reported exotic introductions are more likely to be reported. fish introductions Assessing invasion risk relies on identifying factors that are have resulted in linked to the probability of successful establishment if a new fish new populations species were introduced and released in Australia. There is a establishing. considerable scientific literature on the ecological theory of fish invasions, proposing a suite of factors that may influence whether or not they establish in new environments. Establishment risk There are five key factors for which there is strong evidence of a correlation with establishment success. These should be considered key factors when the risk that exotic fishes could establish here is assessed: The release of 1. Number of release events: large numbers of fish at The release of large numbers of fish at different times and places different times enhances the chance of successful establishment. Small and places populations are more susceptible to extinction from predation, enhances the reduced breeding success, poorer hunting success or increased chance of inter-specific competition. Chance events such as droughts and successful floods are also likely to drive small populations to extinction. establishment. Small populations may also lose genetic variability that may reduce the probability of long-term survival. The minimum viable population size for successful invasion is not known for most species. An analysis of worldwide fish introductions indicates a strong correlation between the number of times a fish species is All species for introduced and the number of exotic populations it establishes. which more All species for which more than ten introduction events have been than ten recorded have established at least one exotic population. Thus it introduction appears likely that most fish species can establish exotic events have populations if sufficient releases are made into suitable been recorded environments. This risk can be reduced by restricting which have established species are kept in Australia, the number of collections holding a at least one species, the number of individuals held in each collection, the exotic security conditions for keeping species, and by educating people population. about the risks of releasing exotic fish into waterways. Any changes to policy or management for exotic species that reduce restrictions on where exotic species can be held, or the numbers of species held, are likely to increase the risk that more exotic fish species will establish wild populations in Australia. 5 2. Climate match: Exotic fish have a greater chance of establishing if they are Exotic fish have introduced to an area with a climate that closely matches that of a greater chance their original range. Species that have a large overseas range over of establishing if several climatic zones are predicted to be strong future invaders. they are The suitability of Australian environments for the establishment introduced to an of a species can be quantified on a broad scale by measuring the area with a climate match between Australia and the overseas geographic climate that range of a species. Climate matching models generate maps of closely matches probability of successful establishment in Australia of a species that of their introduced from any part of the world. Successfully introduced original range. species in Australia have a greater area of climatically matched habitat than species that were released in Australia but failed to establish. Climatic matching only sets the broad parameters for determining if an area is suitable for an exotic fish to establish. Many factors, such as unsuitable water chemistry or flow dynamics, the absence of suitable spawning habitats or food, or the presence of competitors, predators or diseases, might prevent an exotic fish from establishing in a climatically matched area. 3. History of establishing exotic populations elsewhere: A history of establishing A history of establishing exotic populations may indicate that a exotic species has attributes that increase the risk of it establishing in populations other areas. A history of establishing exotic populations elsewhere is a elsewhere is a significant predictor of establishment success for significant exotic fish introduced to Australia and to the Great Lakes of predictor of North America. However, many species that are potential exotics establishment have not been transported to and released in new environments, success for so they have not had the opportunity to demonstrate their exotic fish establishment potential. Hence, caution should be applied when introduced to using a history of establishment elsewhere to predict a species’ Australia. establishment potential in Australia if the species being assessed has little or no history of previous introductions. 4. Overseas geographic range size: Species that have a wide Species that have a wide geographic range are more likely to geographic establish exotic populations than species with restricted ranges. A range are more wide geographic range could indicate flexible or generalist likely to species, or good dispersers, and hence species that are more likely establish exotic to invade successfully. A comparison of the 31 successfully populations established species of exotic fish in Australia with the 19 species than species that were introduced but failed to establish indicates that the with restricted successful species have larger overseas range sizes. ranges. 6 Both family and 5. Taxonomic group: genus are Both family and genus are significantly correlated with significantly introduction success rate for exotic fish species introduced around correlated with the world. The seven most successful families are Gobiidae, introduction Cobitidae, Poeciliidae, Clupeidae, Loricariidae, Atherinidae and success rate for Osteoglossidae. A precautionary approach may be advisable for exotic fish fish that have little or no introduction history, and without species relatives with an introduction history. introduced around the world. There are many additional