Summary1. Commercial fisheries risk unintentionally depleting local population components if stock management units do not reflect the population structure of the species. Atlantic cod Gadus morhua L. was over exploited in the sea areas around the British Isles in the last century and is struggling to recover. There is an urgent need to define the biological stock structure to improve management. 2. In this study, we used data recovered from temperature and depth loggers attached to 252 Atlantic cod to infer and map their movements around the British Isles. Individual cod showed a range of behaviours including migration, site fidelity and limited home ranging. We estimated home ranges and seasonal movements and test predictions based on data from population genetics. Cod from a northern offshore area in the North Sea did not mix with cod from the central and southern North Sea, which in turn did not mix with those from western areas (the Celtic and Irish Seas). 3. Cod experienced average monthly temperatures between 6 and 17°C and occupied average depths between 15 and 165 m. Cod that occupied the deeper northern offshore area lived in colder and less variable waters than elsewhere. Differences in thermal experience are likely to underpin variation in physiology and growth rate that will have implications for how the species responds to climate change. 4. This study provides evidence that cod living around the British Isles are comprised of at least one more distinct population unit that is currently recognized for stock management purposes. Failure to recognize this complexity of stock structure in past management plans is likely to have been a contributory factor to the over-exploitation of cod stocks around the British Isles. 5. Synthesis and applications. The results of this study and recent genetic research provide a new and more definitive understanding of movement patterns and population structure of cod around the British Isles. The applied implication of this is that spatially explicit adjustment of exploitation strategies, for example setting a maximum sustainable yield for each of the population units, should be considered to ensure sustainable harvesting of cod in the future.

Lordan, C., Ó Cuaig, M., Graham, N., and Rihan, D. 2011. The ups and downs of working with industry to collect fishery-dependent data: the Irish experience. – ICES Journal of Marine Science, 68: 1670–1678. Working with the fishing industry to collect fishery-dependent data for scientific and advisory purposes is essential in most countries, but despite the many advantages of working with fishers, it is not without challenges. The objectives and the ups and downs of 16 recent projects in Ireland are described, and four case studies are discussed in detail. Some common themes that characterize both successful and unsuccessful experiences are identified. One critical aspect is industry's sometimes unrealistic time-horizons and expectations when engaging in scientific data collection. Detailed communication of objectives, procedures, results, and relevance not only to industry representatives, but also to vessel owners and crew, is required throughout the life cycle of a project. For some projects, there is a clear need to include incentives in the design, but for others this is less critical. The critical needs for ongoing quality control and assurance, validation of data, and appropriate project design are discussed, along with the link between successful management systems and participatory research. Finally, comment is provided on how the expected reforms of the EU's Common Fisheries Policy will place new demands on joint research.

Fishing industry stakeholders have unique and important contributions to make to fisheries research. Co-operative and collaborative research approaches between science and industry are important to facilitate the documentation of fishers’ knowledge and the co-creation of common understandings. Successful collaborations require open communication, trust and social capital, but numerous barriers exist to establishing these effective partnerships. This paper takes a narrative approach to reflect on the authors’ experiences of engaging and collaborating with Irish fishers in the quest for the co-creation of knowledge, while considering how data from industry can best be used and integrated into scientific processes. This includes reflecting on barriers faced, in addition to motives and opportunities that have enabled this work to progress. Through case study examples, we reflect on issues surrounding misunderstandings regarding the roles of scientists and the scientific process, a lack of transparency, a lack of trust, historical/legacy issues, and contemporary pressures including the COVID-19 pandemic and impacts of Brexit. Building trust and active communication are identified as key elements to effectively co-create knowledge and common understanding. Trust is often developed in an informal setting, but more formalized processes, increased transparency and opportunities to engage, and institutional supports may further facilitate effective knowledge co-creation in fisheries.