Management Scenarios Under Climate Change – A Study of the Nordic and Barents Seas

Abstract

The effects of increasing fishing pressure in combination with temperature increases in the Nordic and Barents Seas have been evaluated using an end-to-end model for the area forced by a downscaled RCP 4.5 climate scenario. The scenarios that have been applied have used four different fractions of fisheries mortality at maximum sustainable yield (Fmsy); 0.6, 0.8, 1.0 and 1.1 × Fmsy. As it is highly likely that more ecosystem components will be harvested in the future, the four scenarios have been repeated with fishing on a larger number of ecosystem components, including harvesting of lower trophic levels (mesozooplankton and mesopelagic fish). The zooplankton biomass had an increasing trend, regardless of the increase in fishing pressure on their predators. However, when introducing harvest on the lower trophic levels, this increase was no longer evident. When harvesting more components, the negative response in biomass of pelagic and demersal fish to increasing harvest became more prominent, indicating an increasing vulnerability in the ecosystem structure to stressors. Although harvest on lower trophic level led to an immense increase in the total catch, it also resulted in a decrease in the total catches of pelagic and demersal fish, despite more species being harvested in these guilds.

Ecological Effects and Ecosystem Shifts Caused by Mass Mortality Events on Early Life Stages of Fish

“…For the historical period, NoBa showed reasonable biomasses and development for both the pelagic and demersal guilds, comparable to Hansen et al (2019b) Figure S10). For the demersal guild, the correlation between observed and modeled biomass was particularly high (r = 0.89), whereas the correlation between observed and modeled pelagic biomass was not as high (r = 0.47).…”

“…The simulated biomass and catches of pelagic (including Norwegian Spring Spawning herring, mackerel and blue whiting) and demersal guilds (including Greenland halibut, Northeast Arctic cod, haddock, beaked redfish and golden redfish) were comparable to observations (Hansen et al, 2019b). The biomass levels were in good agreement, the timing of peaks and troughs though fitted better for the demersal guild than for the pelagic guild.…”

“…The simulated years after the MME was performed without any forcing. All runs included active fisheries, following historical fishing pressures until 2017, thereafter applying F msy levels (fishing pressures achieving maximum sustainable yield) for all commercial stocks (Hansen et al, 2019b).…”

Addressing initialisation uncertainty for end-to-end ecosystem models: application to the Chatham Rise Atlantis model

“…Atlantis models are end-to-end ecosystem models that can be used to model everything in an ecosystem from sunlight to market, including feed-back loops and flow-on effects (Audzijonyte et al, 2017a). There are many published Atlantis models (Link, Fulton & Gamble, 2010;Ainsworth et al, 2011;Ainsworth, Schirripa & Morzaria-Luna, 2015;Fulton et al, 2011;Weijerman et al, 2014;Sturludottir et al, 2018;Ortega-Cisneros, Cochrane & Fulton, 2017;Porobic et al, 2019;McGregor et al, 2019b), and sensitivities and uncertainties are beginning to feature in the more recently published work (Ortega-Cisneros, Cochrane & Fulton, 2017;Sturludottir et al, 2018, Ortega-Cisneros et al, 2018Hansen et al, 2019aHansen et al, , 2019bMcGregor et al, 2019b).…”

Management Strategy Evaluation: Allowing the Light on the Hill to Illuminate More Than One Species

“…However, Punt (2017) also noted the lack of consistent output metrics in ecosystem MSEs, though generally those metrics attempt to summarize status of habitats and non-target species, recovery of threatened and endangered species, and at times social and management objectives. In the last several years progress has been made, as many ecosystem modeling efforts have converged upon using similar sets of performance metrics based on ecological indicators and guildlevel biomass (Marshall et al, 2017;Olsen et al, 2018;Fay et al, 2019;Hansen et al, 2019b;Kaplan et al, 2020;Nilsen et al, 2020). Further tailoring of ecosystem performance metrics requires long-term commitment to stakeholder engagement, which in the United States is typically at the level of Fishery Management Councils.…”