Interactions between biology, environmental and anthropogenic factors on the exploitation of pelagic species by the Scottish fleet

Herring and mackerel are migratory species and targeted seasonally during spawning and/or feeding aggregations. These species comprise 80% by weight of the Scottish pelagic fisheries, and account for >55% by weight, and >40% by value of the entire Scottish fishing sector. The Scottish fleet is 21 large (>40-85m) modern trawlers based in Shetland, Peterhead and Fraserburgh. The fishing efficiency, combined with both restricted quotas and the migratory behaviour of the species result in relatively short seasonal fisheries that are mainly: herring July-Aug and mackerel Jan/Feb and Oct/Nov. Large fluctuations in annual fishing quota together with a mis-match between fisher observations and assessment output led to industry calls for improved science on these stocks. As part of this, the industry through the SPFA, have worked in partnership with UHI and MSS since 2018 to develop fisher self-sampling and fisher/science co-sampling programmes that have been adopted as the route through which the Scottish Government collects pelagic data [1]. These programmes collect data on a haul-by-haul resolution and are providing biological data on previously unobtainable resolution. The data-set continues to grow and is ripe for the analysis of biological factors and for correlation to environmental variables. In addition to immediately apparent seasonal and inter-annual variations within the catch data, there are a range of external factors that affect the fishing choices that skippers make in relation to when to fish, what they are targeting regarding fish size, maturity and condition, and where to land their catches (Scottish processors or abroad). These are influenced by market forces and have in recent years been significantly affected by Russian sanctions (since 2019) and in 2022 by the Ukraine war. The development of the pelagic fisheries from 1945 until 2000 has been documented [2] but since 2000 there has been a complete fleet renewal and significant technological advances that have improved fishing efficiency. Additionally, the introduction of vessel visibility through AIS and VMS has resulted in skippers being able to track where the fleet are, has eliminated fishing location secrecy - a huge change in culture, has cut the amount of time vessels spend searching for shoals and the altered fisher behaviour will have further increased catching efficiency and may have reduced carbon footprint through fuel consumption. The student will work collaboratively with both academia and the pelagic industry. The research will include an element of cross-disciplinary data collection from the incorporation of the collection and analysis of fisher knowledge, through social science-based methodologies, alongside the analysis of empirical datasets.