In MEESO we have developed and tested new submersible platforms with acoustic and optical technologies and new fine-meshed trawl designs. A review of their use, including a summary of standard sampling techniques, has been written as a protocol for future mesopelagic surveys. During MEESO cruises we have used new technologies to provide new estimates of mesopelagic diversity, biomass and individual size. One of the trawls is now used as standard equipment on Norwegian and Icelandic ecosystem surveys.
We have investigated three different commercial midwater trawls with different mesh sizes focusing on catch efficiency and homogeneity of the catch. Furthermore, we investigated which processing methods would be suitable for mesopelagic species. The most commonplace processes all proved applicable and are hypothesised to be the most likely with commercial viability. Biotechnological development of the mesopelagic catch was also performed with experimental identification of different compounds with potential use in biotechnological applications such as nutraceutical or pharmacological.
Field campaigns were conducted in the North Atlantic, covering large areas with both acoustic surveys and net sampling down to 1000 m depth. Regional maps of acoustic abundance were created and estimates of biomass in the mesopelagic were improved. The influence of hydrographical parameters on the vertical distribution of key fish species has been studied and new insights into trophic interactions and pathways of carbon flow revealed. Demographic parameters essential for understanding the population dynamics of key fish species in the mesopelagic layers were produced.
We have delivered new biomass and key demographic parameter estimates for B. glaciale and M. muelleri. We have identified spatial growth and mortality variations and estimated MSY and associated reference points, indicating high productivity but uncertainty regarding sustainable fishing. An ensemble of population and ecosystem models was used to explore resilience to future harvesting and climate change. Projections suggest fluctuating MSYs and climate vulnerability for M. muelleri, suggesting theoretical feasibility but practical challenges for sustainable harvesting, especially amid climate change uncertainties.
Based on technical and economic insights gained through stakeholder workshops and interviews and various databases, bioeconomic models were developed to evaluate management strategies and to perform a cost-benefit analysis including monetised climate impacts. Stakeholder workshops, a survey, a behavioural experiment, and automated contents analysis (ACA) of social media posts were carried out to analyse public understanding of mesopelagic fisheries. Observational field work on research vessels and ACA of scientific abstracts analysed the role of scientific practices in forming frames and perceptions of the mesopelagic zone.
MEESO studied the governance of mesopelagic fishery sustainability. Analyzing 2700+ policy documents, it found few policies protecting mesopelagic fish. Policies for climate, biodiversity, and fish tend to be isolated, hindering integrated ecosystem management. Interviews revealed gaps in governance but highlighted collaboration opportunities with RFMO, High Seas treaty, area-based management, impact assessment, and ecosystem-based fisheries management. Deep uncertainty analysis showed tradeoffs between fishing and preserving climate services, with potential costs outweighing benefits. Geographical analysis revealed governance challenges for species-level management, such as migratory stocks and trans-boundary effects beyond national jurisdiction.
For capacity building and promoting new techniques, methods, models and key knowledge to the public, external stakeholders and governance bodies, MEESO has published over 5 e-learning courses and webinars on key models and new methods. Additionally, 2 public videos on best surveying and fishing practices were released for general and future use, and 14 workshops for feedback were conducted. The project results have been disseminated through more than 35 papers in high ranking scientific peer reviewed journals and in 4+ popular science publications.
