FISHCOM: Addressing uncertainty in FISHeries management in a zooplankton-fish COMmunity under humaninduced perturbations (completed)

• Durant, Joël; Holt, Rebecca Emma; Ono, Kotaro & Langangen, Øystein Ole Gahr (2023). Predatory walls may impair climate warming-associated population expansion. Ecology. ISSN 0012-9658. 104(9), p. 1–8. doi: 10.1002/ecy.4130. Full text in Research Archive Show summary

  Climate change has a profound impact on species distribution and abundanceglobally, as well as local diversity, which affects ecosystem functioning. In par-ticular, changes in population distribution and abundance may lead tochanges in trophic interactions. Although species can often shift their spatialdistribution when suitable habitats are available, it has been suggested thatpredator presence can be a constraint on climate-related distribution shifts.We test this using two well-studied and data-rich marine environments.Focusing on a pair of sympatric fishes, Atlantic haddock Melanogrammus aeglefinus and cod Gadus morhua, we study the effect of the presence andabundance of the latter on the former distribution. We found that the distribu-tion of cod and increased abundance may limit the expansion of haddock tonew areas and could consequently buffer ecosystem changes due to climatechange. Though marine species may track the rate and direction of climateshifts, our results demonstrate that the presence of predators may limit theirexpansion to thermally suitable habitats. By integrating climatic and ecologicaldata at scales that can resolve predator–prey relationships, this analysis dem-onstrates the usefulness of considering trophic interactions to gain a morecomprehensive understanding and to mitigate the effects of climate change onspecies distributions.

• Buttay, Lucie; Ohlberger, Jan Philipp & Langangen, Øystein Ole Gahr (2023). Management strategies can buffer the effect of mass mortality in early life stages of fish. Journal of Applied Ecology. ISSN 0021-8901. 60(10), p. 2056–2065. doi: 10.1111/1365-2664.14489. Full text in Research Archive Show summary

  1. Mass mortality (MM) events affecting early life stages of fish can have strong and long-term consequences for population abundance and demography as well as the economic activity supported by exploited stocks. Adaptive fishery manage-ment may help mitigate economic impacts and ensure sustainable resource use following a MM event. 2. Using a state-space life cycle model, we simulated ‘what-if’ scenarios of MM on Northeast Arctic cod (Gadus morhua) eggs and larvae. We compared the expected catches, total stock biomass (TSB), and interannual variability in catches over a period of 10 years after the simulated disturbance. We further evaluated a range of management mitigation strategies, namely reductions in fishing mortality of varying duration (1–10 years) and intensity (no fishing reduction to full ban). 3. A large range of reductions in fishing led to an increase in expected catches over 10 years compared to no reductions, especially when applied immediately after the perturbation and when the cod population was characterized by a high mean age and high TSB. Severe fishing reductions can increase catches substantially but are associated with high interannual variability. Fishing reductions of moder-ate intensity applied between 1 and 4 years would allow to increase catches with only a slight increase in interannual variability. 4. Our findings demonstrate the potential benefits of an adaptive approach to fish-eries management and highlight that mitigation actions may ensure the sustain-able exploitation of fish stocks in the wake of unexpected disturbances. 5. Synthesis and application. Mass mortality events during early life stages of fish can potentially have substantial and long-term effects on the population. Mitigation is more efficient when the affected population has a diverse age structure and when the mitigation strategy is applied immediately after the perturbation. Severe re-duction in fishing mortality is an efficient measure to increase the expected aver-age catch but is associated with high interannual variability. Fishing reduction of moderate intensity applied during 1–4 years after the event also increases the expected average catch with only slightly higher interannual variability in catches.

• Langangen, Øystein Ole Gahr; Ohlberger, Jan Philipp; Stige, Leif Christian; Patin, Rémi; Buttay, Lucie & Stenseth, Nils Christian [Show all 8 contributors for this article] (2022). Effects of early life mass mortality events on fish populations. Fish and Fisheries. ISSN 1467-2960. 24(1), p. 176–186. doi: 10.1111/faf.12718. Full text in Research Archive
• Nilsen, Ina; Hansen, Cecilie; Kaplan, Isaac; Holmes, Elizabeth & Langangen, Øystein Ole Gahr (2022). Exploring the role of Northeast Atlantic cod in the Barents Sea food web using a multi-model approach. Fish and Fisheries. ISSN 1467-2960. 23(5), p. 1083–1098. doi: 10.1111/faf.12671. Full text in Research Archive
• Ottersen, Geir & Holt, Rebecca Emma (2022). Long-term variability in spawning stock age structure influences climate–recruitment link for Barents Sea cod. Fisheries Oceanography. ISSN 1054-6006. 32(1), p. 91–105. doi: 10.1111/fog.12605. Full text in Research Archive
• Durant, Joël; Ono, Kotaro & Langangen, Øystein Ole Gahr (2022). Empirical evidence of nonlinearity in bottom up effect in a marine predator-prey system. Biology Letters. ISSN 1744-9561. 18(11). doi: 10.1098/rsbl.2022.0309. Full text in Research Archive Show summary

  Strength of species interaction may have profound effects on population dynamics. Empirical estimates of interaction strength is often based on the assumption that the interaction strengths are constant. Barents Sea cod and capelin are two fish populations for which such interaction has been acknowledged and used, under the assumption of constant interaction strength, when studying their population dynamics. However, species interaction can often be non-linear in marine ecosystems and might profoundly change our understanding of food chains. Analysing 37 years long survey time series in the Arcto-Boreal Barents Sea with a state-space modelling framework, we demonstrate that the effect of capelin on cod is not linear but shifts depending on capelin abundance: while capelin is beneficial for cod population at high abundance, below the threshold, it becomes less important for cod. Our analysis therefore shows the importance of investigating non-linearity in species interaction and may contribute to an improved understanding on species assemblages.

• Ohlberger, Jan; Langangen, Øystein Ole Gahr & Stige, Leif Christian (2022). Age structure affects population productivity in an exploited fish species. Ecological Applications. ISSN 1051-0761. 32(5). doi: 10.1002/eap.2614. Full text in Research Archive
• Diekert, Florian Klaus; Nøstbakken, Linda & Richter, Andries Peter (2021). Control activities and compliance behavior—Survey evidence from Norway. Marine Policy. ISSN 0308-597X. 125. doi: 10.1016/j.marpol.2020.104381. Full text in Research Archive
• Diekert, Florian Klaus & Brekke, Kjell Arne (2021). Groups discipline resource use under scarcity. Theory and Decision. ISSN 0040-5833. 92, p. 75–103. doi: 10.1007/s11238-021-09813-4.
• Durant, Joël; Aarvold, Leana & Langangen, Øystein Ole Gahr (2021). Stock collapse and its effect on species interactions: Cod and herring in the Norwegian-Barents Seas system as an example. Ecology and Evolution. ISSN 2045-7758. 11, p. 16993–17004. doi: 10.1002/ece3.8336. Full text in Research Archive Show summary

  Both the Norwegian Spring Spawning herring (Clupea harengus) and the Northeast Arctic (NEA) cod (Gadus morhua) are examples of strong stock reduction and decline of the associated fisheries due to overfishing followed by a recovery. Cod and herring are both part of the Barents Sea ecosystem, which has experienced major warming events in the early (1920–1940) and late 20th century. While the collapse or near collapse of these stocks seems to be linked to an instability created by overfishing and climate, the difference of population dynamics before and after is not fully understood. In particular, it is unclear how the changes in population dynamics before and after the collapses are associated with biotic interactions. The combination of the availability of unique long-term time series for herring and cod makes it a well-suited study system to investigate the effects of collapse. We examine how species interactions may differently affect the herring and cod population dynamic before and after a collapse. Particularly we explore, using a GAM modeling approach, how herring could affect cod and vice versa. We found that the effect of cod biomass on herring that was generally positive (i.e., covariation) became negative after the collapse (i.e., predation or competition). Likewise a change occurred for the cod, the juvenile herring biomass that had no effect before the collapse had a negative effect after. Our results indicate that the population collapses may alter the inter-specific interactions and response to abiotic environmental changes. While the stocks are at similar abundance levels before and after the collapses, the system is potentially different in its functioning and may require different management action.

• Färber, Leonie Anette; van Gemert, Rob; Langangen, Øystein; Durant, Joel Marcel & Andersen, Ken Hasle (2020). Population variability under stressors is dependent on body mass growth and asymptotic body size. Royal Society Open Science. ISSN 2054-5703. 7(2), p. 1–11. doi: 10.1098/rsos.192011. Full text in Research Archive
• Durant, Joel Marcel; Ono, Kotaro; Stenseth, Nils Christian & Langangen, Øystein (2020). Nonlinearity in interspecific interactions in response to climate change: Cod and haddock as an example. Global Change Biology. ISSN 1354-1013. 26(10), p. 5554–5563. doi: 10.1111/gcb.15264. Full text in Research Archive
• Ono, Kotaro; Langangen, Øystein & Stenseth, Nils Christian (2019). Improving risk assessments in conservation ecology. Nature Communications. ISSN 2041-1723. 10, p. 1–7. doi: 10.1038/s41467-019-10700-4. Full text in Research Archive
• Langangen, Øystein; Färber, Leonie Anette; Stige, Leif Christian; Diekert, Florian Klaus; Barth, Julia Maria Isis & Matschiner, Michael [Show all 11 contributors for this article] (2018). Ticket to spawn: Combining economic and genetic data to evaluate the effect of climate and demographic structure on spawning distribution in Atlantic cod. Global Change Biology. ISSN 1354-1013. 25(1), p. 134–143. doi: 10.1111/gcb.14474. Full text in Research Archive

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• Durant, Joël (2022). Match-mismatch, trophic interactions and climate change. Show summary

  Climate change is affecting the trophic interactions on which we base our understanding of marine systems. The consequence is that we must get used to a world where our hard acquired knowledge on ecosystem and trophic interactions is no longer accurate, or at least not reliably so. In other words, the models we have developed based on long-term time series may not be reliable. We know that the physiology and the mechanisms it is driving are changing at the slower pace than climate. Building mechanistic models could thus be useful to explore the future consequences of climate change. In fish, the major driver of population dynamics is the recruitment of individuals through the reproduction process (i.e., production and survival through the early life stages). Several mechanistic hypotheses have been set forth to explain changes in fish production in relation to phenology, which is well documented to be strongly affected by climate change. One of the most well-known is the “match-mismatch” hypothesis (MMH) elaborated by David Cushing. A question is if the MMH is a useful tool to understand animal recruitment in the context of global climate change. I will present some of the latest development from my group on match-mismatch models (role of abundance and spatial distribution…) and the role of MMH for population dynamics. Finally, I will address the value of the MMH to make projection and I will highlight some of the limitation of our current understanding of MMH.

• Diekert, Florian Klaus; Goeschl, Timo & König, Christian (2019). The Nature of Experience.
• Diekert, Florian Klaus & Brekke, Kjell Arne (2019). Groups discipline resource use under scarcity.

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