Behavioural responses to environmental novelty in demersal, shelterassociated invasive fish and their native analogues

Invasive species may differ from native species in terms of behavioural responses to the stress of encountering a novel environment. Learning about the nature of these differences can help us understand the mechanisms of dispersal and success of the alien species in colonized environments. Here, we investigated this topic using two Ponto-Caspian gobies as model species. They constitute a specific group of invasive fish spreading in North America and Europe. They are benthic, territorial fish of low mobility; they are poor swimmers and are strongly associated with shelters. We compared the behaviour of two invasive goby fishes (the racer goby, Babka gymnotrachelus, and the monkey goby, Neogobius fluviatilis) to that of their native counterparts (the European bullhead, Cottus gobio, and the gudgeon, Gobio gobio, respectively). We used three laboratory tests to measure boldness-shyness traits: shelter occupancy test, novel object test and open field test. The European bullhead left the shelter later and was less active, and avoided the open field to a greater extent than the racer goby. The gudgeon was more associated with the shelter and novel object than the monkey goby and, in contrast to the monkey goby, decreased its activity in the presence of the novel object and in the open field. All the species were attracted to the vicinity of the novel object. Our study suggests that the invasive Ponto-Caspian gobies are bolder when confronted with structural changes in their environment and have a greater potential to spread across the open bottom, devoid of hiding places, compared to their native analogue species. (c) 2023 The Authors. Published by Elsevier Ltd on behalf of The Association for the Study of Animal Behaviour. This is an open access article under the CC BY license (http://creativecommons.org/licenses/ by/4.0/).