LAUSR

Non-native freshwater zooplankton species have been recorded from aquaculture ponds in New Zealand and Italy, while zooplankton invasions elsewhere have implicated the aquaculture industry as the vector for introduction. However, the prevalence of non-native species in international aquaculture facilities is unclear. We undertook a literature review of publications examining zooplankton assemblages in freshwater aquaculture ponds globally to determine; 1) the prevalence of non-native taxa, 2) the quality of the studies undertaken, 3) how well the major freshwater aquaculture nations are represented in studies, and 4) the representation of dominant aquaculture species. Thirty-two suitable publications were found that provided data on zooplankton assemblages from aquaculture facilities. We supplemented this by sampling Huka Prawn Park, Taupō, New Zealand, as knowledge of zooplankton in prawn facilities was scarce. Zooplankton data was obtained for 205 outdoor ponds and experimental tanks, from 39 different aquaculture facilities, across 13 countries. Non-indigenous taxa were recorded from 17.9% of facilities globally. Over half of these publications (53.1%) identified taxa to genus level only, with the remaining 46.9% attempting species level identifications. The high proportion of publications not identifying to species level indicates that non-native species will not be recognised in most studies; 31.8% of facilities were invaded when considering only studies with species level identifications. In total, 234 different taxa were identified (including 184 to species level), with only 4, located in Italy and New Zealand, recognised as non-native; only 3 of these 4 taxa were clearly identified as non-indigenous in their respective publications. Another species has been identified outside of its native range in North American aquaculture facilities, but no co-existing zooplankton species were reported. While aquaculture facilities were found to harbour only a small number of non-indigenous species, our findings indicate that there is a significant lack of taxonomic resolution used in most studies, and a lack of surveys in major aquaculture producing regions and from facilities holding many of the major aquaculture species. Importantly, few zooplankton invaders putatively originating from the aquaculture industry have been found within aquaculture facilities themselves. Overall, it is currently difficult to determine the prevalence of non-indigenous zooplankton species in aquaculture facilities globally, and our results suggest the risk may be far higher than is currently appreciated. As such, we recommend systematic surveys of ponds utilising species level identification from a variety of geographic regions, to better quantify invasion risks by non-native zooplankton taxa from the freshwater aquaculture industry.