Description: A growing population on a planet with limited resources demands finding new sources of protein. Hence, fisheries are turning their perspectives towards mesopelagic fish, which have, so far, remained relatively unexploited and poorly studied. Large uncertainties are associated with regards to their biomass, turn-over rates, susceptibility to environmental forcing and ecological and biogeochemical role. Models are useful to disentangle sources of uncertainties and to understand the impact of different processes on the biomass. In this study, we employed two food-web models – OSMOSE and the model by Anderson et al. (2019, or A2019) – coupled to a regional physical–biogeochemical model to simulate mesopelagic fish in the Eastern Tropical South Pacific ocean. The model by A2019 produced the largest biomass estimate, 26 to 130% higher than OSMOSE depending on the mortality parameters used. However, OSMOSE was calibrated to match observations in the coastal region off Peru and its temporal variability is affected by an explicit life cycle and food web. In contrast, the model by A2019 is more convenient to perform uncertainty analysis and it can be easily coupled to a biogeochemical model to estimate mesopelagic fish biomass. However, it is based on a flow analysis that had been previously applied to estimate global biomass of mesopelagic fish but has never been calibrated for the Eastern Tropical South Pacific. Furthermore, it assumes a steady-state in the energy transfer between primary production and mesopelagic fish, which may be an oversimplification for this highly dynamic system. OSMOSE is convenient to understand the interactions of the ecosystem and how including different life stages affects the model response. The combined strengths of both models allow us to study mesopelagic fish from a holistic perspective, taking into account energy fluxes and biomass uncertainties based on primary production, as well as complex ecological interactions.

Description: Highlights: • Modelled fish biomass was affected by interannual variability in the plankton food. • The effects were small compared with the high variability in observations. • Fish were highly affected by changes in the larval mortality of anchovy. Abstract: The Northern Humboldt Current System is the most productive eastern boundary upwelling system, generating about 10 % of the global fish production, mainly coming from small pelagic fish. It is bottom-up and top-down affected by environmental and anthropogenic variability, such as El-Niño Southern Oscillation and fishing pressure, respectively. The high variability of small pelagic fish in this system, as well as their economic importance, call for a careful management aided by the use of end-to-end models. This type of models represent the ecosystem as a whole, from the physics, through plankton up to fish dynamics. In this study, we utilised an end-to-end model consisting of a physical–biogeochemical model (CROCO-BioEBUS) coupled one-way with an individual-based fish model (OSMOSE). We investigated how time-variability in plankton food production affects fish populations in OSMOSE and contrasted it against the sensitivity of the model to two parameters with high uncertainty: the plankton accessibility to fish and fish larval mortality. Relative interannual variability in the modelled fish is similar to plankton variability. It is, however, small compared with the high variability seen in fish observations in this productive ecosystem. In contrast, changes in larval mortality have a strong effect on anchovies. In OSMOSE, it is a common practice to scale plankton food for fish, accounting for processes that may make part of the total plankton in the water column unavailable. We suggest that this scaling should be done constant across all plankton groups when previous knowledge on the different availabilities is lacking. In addition, end-to-end modelling systems should consider environmental impacts on other biological processes such as larval mortality in order to better capture the interactions between environmental processes, plankton and fish.

Description: Science Board Meeting 2022 — Note from the Science Board Chair. FUTURE SSC’s 8th Annual Meeting ~ Highlights. PICES-2022 and the first hybrid annual meeting. Featuring PICES-2022 Award recipients: (Chair Award, Wooster Award, Zhu-Peterson Award, PICES Ocean Monitoring Service Award, ECS Best Presentation Awards). PICES-2022 Workshop Reports: (W1: Distributions of pelagic, demersal, and benthic species associated with seamounts in the North Pacific Ocean and factors influencing their distributions, W2: Integrated Ecosystem Assessment (IEA) to understand the present and future of the Central Arctic Ocean (CAO) and Northern Bering and Chukchi Seas (NBS-CS), W3: SmartNet: Promoting PICES and ICES Leadership in the UN Decade of Ocean Science for Sustainable Development, W4: Exploring Engagement Opportunities for Early Career Ocean Professionals (ECOPs) within PICES and Internationally, W5: Integrating biological research, fisheries science and management of broadly distributed flatfish species across the North Pacific Ocean in the face of climate and environmental variability, W7: Anthropogenic stressors, mechanisms and potential impacts on Marine Birds, Mammals, and Sea Turtles, W8: Science Communication Training: How to Create Memorable PICES Science Stories, W10: A TCODE Workshop on “Openly Discoverable, Accessible, and Reusable Data and Information in the U.N. Decade”). PICES AP-NPCOOS "Ocean Big Data" Summer School. PICES AP-CREAMS Virtual Summer School on Ocean Turbulence: From Observing to Research. Science and Innovation to Scale Up Ocean Action: UN Ocean Conference 2022. ECOP Perspective on the 4th Early Career Scientist Conference (ECSC4). Symposium in Lisbon Re-unites the Global Community Investigating Small Pelagic Fish. SPF2022 Symposium Workshop Reports: (1: Application of Genetics to Small Pelagic Fish, 2: The Devil’s in the Details of Using Species Distribution Models to Inform Multispecies and Ecosystem Models, 3: Small Pelagics for Whom? Challenges and Opportunities for the Equitable Distribution of Nutritional Benefits, 4: Evaluating Inter-Sectoral Tradeoffs and Community-Level Response to Spatio-Temporal Changes in Forage Distribution and Abundance, 5: Recent Advances in the Daily Egg Production Method (DEPM): Challenges and Opportunities, 6: Small Pelagic Fish Reproductive Resilience). SOLAS Open Science Conference, 2022. Early Career Scientist Participation in SOLAS Open Science Conference, 2022. PICES SeaTurtle researchers find clues linking derelict fishing lines of “Urban Fishermen” to sea turtle stranding. NPAFC's IYS Synthesis Symposium - Key Takeaways. The Bering Sea: Current Status and Recent Trends. Western North Pacific: Current status and recent topic: Sea Surface Temperature during the 2022 warm season, The Northeast Pacific: Update on marine heatwave status and trends. PICES Events Calendar. PICES by the Numbers, and an Invitation to join SG-GREEN. Open call for PICES Press submissions | About PICES Press

Description: Published

Description: Non Refereed