Exploring Balanced Harvesting by Using an Atlantis Ecosystem Model for the Nordic and Barents Seas

Abstract

Balanced Harvesting" (BH) has been suggested as a possible strategy to meet the objectives of the Ecosystem Approach to Fisheries, ensuring a high sustainable yield while maintaining ecosystem structure and function. BH proposes a moderate fishing mortality in proportion to productivity spread across the widest possible range of species, stocks, and sizes in an ecosystem producing a sustainable and overall non-selective harvest. The Norwegian and Barents Seas have been subjected to moderate fishing pressure on commercial species, and elements of an ecosystembased approach to management for many years, but not the fishing pattern proposed by BH. By using an Atlantis ecosystem model of the Nordic and Barents Seas, we investigated the effects of applying a BH regime to a region with existing successful fisheries management. This was done by running simulations with combinations of historic fishing pressure and fishing mortality rates proportional to 25% of the productivity of most species and sizes. The simulations were then compared to a control run where the historical fisheries were applied. The model results showed that implementing a BH regime in the Norwegian and Barents Seas would only produce marginal increases in total yields of currently commercially exploited stocks, likely because the Norwegian fisheries are already mostly well-managed. However, expanding the fishery to include species that are not commercially exploited today did produce higher yields, especially on lower trophic levels. This study represents the first attempted examination of implementing BH based on productivity using an Atlantis ecosystem model, as well as the first investigation of BH in the Norwegian and Barents Seas. We use this model as a case study to identify the gains that species-based BH can be expected to give over well-implemented traditional fisheries management rather than simply comparing to an over-exploited system.

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

“…Enhancing the number of components and also spreading the harvest across multiple trophic levels has been suggested as one solution (Sethi et al, 2010;Garcia et al, 2012;Kolding et al, 2016). However, going to a fully balanced harvest might not be the preferred solution (Howell et al, 2016;Nilsen, 2018).…”

Overexploitation, Recovery, and Warming of the Barents Sea Ecosystem During 1950–2013

“…This may have contributed to a kind of trophic balance when both typical prey and predator FGs were exploited simultaneously. Nilsen et al (2020) explored balanced harvesting strategies for the Norwegian and BS using the Atlantis model and found that a balanced harvesting regime would only produce marginal increases in total yield of currently exploited FGs compared to the historical exploitation regime after 1980.…”

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.…”