Behavioural responses to environmental novelty in demersal, cover-seeking invasive fish and their native counterparts

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 to understand the mechanisms of dispersal and success of the alien species in colonised environments. Here, we have investigated this topic using the Ponto-Caspian gobies as model species. 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 fish behaviours were analysed using Noldus Ethovision XT ® 10.1 program. The uploaded files contain raw data exported from the program. There is a “description” sheet in each file to explain the variable meanings. We performed a Principal Component Analysis (PCA) on the correlation matrix separately for each test and each pair of fish species (six analyses in total) using these data. Then we run general Linear Models on the principal components extracted by the PCA to get the results. The results showed that European bullhead left the shelter later and was less active, as well as 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.