IMIS

L'Archipel des Kerguelen (49S, 70E) - a remote island group in the French Southern and Antarctic Lands - is a unique and pristine environment to study colonization mechanisms in salmonid fishes. Beginning in the early 1950s, several salmonid species were introduced to Kerguelen, which was devoid of any native fish fauna. Since then, brown trout have successfully invaded the landscape and established several self-sustaining breeding populations. Kerguelen thus provides a rare opportunity to study the process of colonization (e.g. demography, habitat use, movement patterns and range expansion) in the absence of confounding factors such as inter-specific competition with native fish species and human activities. Despite recent research efforts into the invasion dynamics of brown trout, many questions remain unanswered and limit our basic biological understanding of salmonids exploration and colonization behaviour. How far do anadromous brown trout from the colonization front migrate in the marine environment? Do they explore other freshwater systems along the way? What role do phenotype and environmental conditions have in mediating exploration behaviour? Using a combination of acoustic telemetry and bio-sampling techniques, we will test the over-arching hypothesis that inter-individual differences in marine habitat use and exploration behaviour by brown trout are explained by intrinsic (phenotypic differences) and by extrinsic (environmental) factors. Specifically, we will: i) quantify the marine and freshwater habitat use of individual brown trout along the colonization front at Kerguelen; ii) examine how well phenotypic traits explain individual movement and exploration behaviour; and iii) examine whether seasonal, environmental variation in temperature and salinity also influence exploration behaviour. In Jan 2018, we deployed a total of 52 acoustic receivers in rivers, estuaries, and in the marine environment surrounding the brown trout colonization front of Kerguelen Archipelago - currently located in Baie Irlandaise. Subsequently, in Jan and Feb 2018, we externally tagged 50 adult brown trout with acoustic transmitters that record ambient temperature and conductivity, as well as collected measurements, scales and blood samples to characterize individual phenotypes. After tagging and sampling, fish were released back in the environment and subsequently detected in the acoustic array. Receivers will be recovered and downloaded in Jan 2019. The salmonid invasion of Kerguelen's fish-less, glacially-fed, and under-exploited ecological niches makes an excellent study context to develop modelling tools applicable to predicting the movement of salmonids to the new, fish-less habitats in other Arctic and Antarctic regions exposed via melting glaciers. Ultimately, this study will provide key information about the intrinsic and extrinsic factors underlying invasion, range expansion, and colonization.