| Summary: | For migratory animals, understanding where individuals are in space and time is a cornerstone for conservation. Atlantic bluefin tuna (ABT) are a migratory teleost fish with a high commercial value. Their distribution in the North Atlantic has fluctuated over time, and as a result a key research goal over the past two decades has be discerning trends in both their general distribution and migratory habits. This thesis investigates the contemporary spatial ecology of ABT in the northeast Atlantic. This thesis represents the most comprehensive analysis of the spatial ecology of ABT in the northeast Atlantic to date. In Chapter 2 I combine datasets from multiple sources (citizen science, ecotour operators, fisheries surveys, and commercial fisheries) to demonstrate that ABT have increased in relative occurrence off the UK and Ireland since 2014. This increase is likely linked to an increase in the eastern stock of ABT, and in part to hydroclimatic forcing. In Chapter 3, I show that ABT present in foraging aggregations off the coast of Ireland form two migratory ecotypes, one that migrates to the Central Atlantic and another that conducts dominant east-west movements. For all ABT tracked from Ireland, the Bay of Biscay is identified as an important foraging ground, no tracked ABT migrated to the English Channel (hereafter “the Channel”) and individuals from both ecotypes visit known spawning grounds in the Mediterranean Sea. In Chapter 4, I identify a direct relationship between data quantity and the accuracy and precision of geolocation for tracked ABT using Wildlife Computers’ proprietary software (GPE3) and hardware (MiniPATs). To aid the field of biologging. I provide researchers and manufacturers with quality control processes to reduce the risk of drawing conclusions based on inaccurate or imprecise data. The ramifications of the findings from this chapter are considerable as they will aid all researcher undertaking PAT-based research requiring route reconstruction from drawing erroneous conclusions. In ...
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