Degree Name

Bachelor of Conservation Biology (Honours)


School of Earth, Atmospheric and Life Sciences


Marian Wong


Social interactions among shoaling fish often rely on the recognition of conspecifics and appropriate behavioural responses towards them. Furthermore, the complexity of shoal composition and preferences is often also influenced by the sex and size of the fish. Despite the extensive literature on social behaviours in shoaling fish and invasive-native species impacts, little is explicitly known of the effects of invasive fish on social recognition in native fishes. Studying native-invasive interactions in a social recognition and shoaling preference context is critical to understanding the potential effects invasive fish pose on native shoaling species. The first objective of this study was to determine whether the native Pacific blue-eye (Pseudomugil signifer) had the ability to recognise a shoal comprising familiar individuals and preferentially associate with it over a shoal comprising unfamiliar individuals. Secondly, whether these abilities and preferences changed with sex or body size of the focal fish. Thirdly, it was investigated whether the individual recognition abilities and shoaling preferences of P. signifer were affected by the presence of an additional unfamiliar conspecific versus an invasive Eastern mosquitofish (Gambusia holbrooki). Simple binary choice experiments allowing both visual and chemical cues were conducted to record focal fish’s proportion of time spent with unfamiliar and familiar stimulus shoals and activity rate. Overall, this study found that P. signifer did not show a preference for familiar over unfamiliar shoal mates, and this did not change with sex or size. Furthermore, the presence of G. holbrooki did not affect shoal recognition or shoal preference in focal P. signifer. The overall lack of preferences suggests that P. signifer may not have the ability to recognise individuals based on familiarity, or there may not be substantial benefits of shoaling with familiar over unfamiliar conspecifics. Given that P. signifer is a shoaling species and social affiliation appears to confer fitness advantages, the lack of preference may beneficially allow individuals to form shoals regardless of familiarity with conspecifics. The findings of this study also suggest that G. holbrooki IV presence is not costly for P. signifer. However, longer-term experiments with the two species would be important for confirming whether the invasive species poses a threat as an aggressive competitor. Therefore, it is important that additional research is conducted regarding what processes are driving shoaling in P. signifer and how G. holbrooki impacts them. Overall, in conjunction with past and future studies, this study contributes towards a more comprehensive understanding of the shoaling preferences of native P. signifer and how they are affected by the invasive G. holbrooki.

FoR codes (2008)

060201 Behavioural Ecology



Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.