Synthesizing lessons learned from comparing fisheries production in 13 northern hemisphere ecosystems: emergent fundamental features

Abstract

Understanding the drivers of the productivity of marine ecosystems continues to be a globally important issue. A vast body of literature identifies 3 main processes that regulate the production dynamics of fisheries: biophysical, exploitative, and trophodynamic. Here, we synthesize results from international workshops in which surplus production models were applied to 13 northern hemisphere ecosystems that support notable fisheries. The results are compared across systems, levels of species aggregation, and drivers. By applying surplus production models at single-species (SS), multi-species (MS), aggregated group, and full-system levels across ecosystems, we find that the different levels of aggregation provide distinct, but complementary, information. Further, it is clear that the triad of drivers contributes to fisheries productivity in each ecosystem, but the key drivers are system-specific. Our results also confirm that full-system yield is less than the sum of SS yields and that some MS and aggregate yields may lead to overharvest of some stocks if species groups are constructed without considering common productivity, inter-species, and en vironmental interactions. Several fundamental features emerge from this Theme Section including sigmoidal biomass accumulation curves across trophic levels, improvement of model fits by inclusion of environmental or ecological covariates, the inequality of system maximum sustainable yield (MSY) versus aggregated sums and SS sums of MSY, a 1 to 5 t km −2 fishery yield rule of thumb, and the finding that tradeoffs among ocean use objectives may not be as harsh as originally thought. These emergent features have the potential to alter our understanding of marine ecosystem dynamics and improve how we manage fisheries production.

Comparing Apples to Oranges: Common Trends and Thresholds in Anthropogenic and Environmental Pressures across Multiple Marine Ecosystems

“…Ecosystem thresholds were observed at landings of ∼2-4.5 t km −2 and fisheries exploitation of ∼20-40% of the total estimated biomass. All landings estimates fall within previously determined ecosystem-level surplus production model threshold estimates of 1-6 t km −2 Link et al, 2012;Lucey et al, 2012), further corroborating the robustness of a potentially universal ecosystem-level fisheries yield, at least in the northern hemisphere.…”

“…The impact of pressure variables at differing scales can also reveal unexpected responses. Link et al (2012) demonstrated that estimates of full system yield from surplus production models at the ecosystem level are lower than the sum of single species yield or multi-species yield. Being more conservative, the ecosystem level estimates indicate a potential for overharvesting certain fish stocks when ecosystem-level considerations are not made.…”

Exploring Patterns of Seafood Provision Revealed in the Global Ocean Health Index

“…For the fisheries sub-goal, it was very difficult to derive an accurate estimate of mMSY. Our estimate was obtained using a catch-based method for calculating singlespecies MSYs for each stock, summing across all stocks, and reducing this value by 25 % to account for multispecies interactions (Link et al 2012). Some data limitations may have caused poor estimates of MSY and, consequently, mMSY.…”

Getting to the bottom of global fishery catches

“…Cheung et al (21) underscore the need to mitigate climate change, predicting that each additional degree Celsius of warming will cost the planet some 3 million metric tons of potential fish catches. Ultimately, understanding the drivers of the productivity of marine ecosystems has the potential to help improve how we manage fisheries production both currently and into the future (22). If climate change alters the productivity of terrestrial and marine food webs, this change in productivity will challenge attempts to manage natural resources sustainably and conserve biodiversity.…”