Bycatch levies could reconcile trade-offs between blue growth and biodiversity conservation

eDNA based bycatch assessment in pelagic fish catches

Pelagic fish like herring, sardines, and mackerel constitute an essential and nutritious human food source globally. Their sustainable harvest is promoted by the application of precise, accurate, and cost-effective methods for estimating bycatch. Here, we experimentally test the new concept of using eDNA for quantitative bycatch assessment on the illustrative example of the Baltic Sea sprat fisheries with herring bycatch. We investigate the full pipeline from sampling of production water on vessels and in processing factories to the estimation of species weight fractions. Using a series of controlled mixture experiments, we demonstrate that the eDNA signal from production water shows a strong, seasonally consistent linear relationship with herring weight fractions, however, the relationship is influenced by the molecular method used (qPCR or metabarcoding). In four large sprat landings analyzed, despite examples of remarkable consistency between eDNA and visual reporting, estimates of herring bycatch biomass varied between the methods applied, with the eDNA-based estimates having the highest precision for all landings analyzed. The eDNA-based bycatch assessment method has the potential to improve the quality and cost effectiveness of bycatch assessment in large pelagic fisheries catches and in the long run lead to more sustainable management of pelagic fish as a precious marine resource.

Experimental evidence of the impact of framing of actors and victims in conservation narratives

Media narratives play a crucial role in framing marine conservation dilemmas by depicting human actors, such as fish consumers or the fishing industry, as responsible for negative effects of their actions on species and ecosystems. However, there is little evidence documenting how such narratives affect preferences for reducing bycatch. Behavioral science research shows that people can act less prosocially when more actors are responsible for a collective outcome (responsibility diffusion effect) and when more victims need to be helped (compassion fade effect); thus, the media's framing of actors and victims may have a significant effect on preferences. We conducted the first test of responsibility diffusion and compassion fade in a marine context in an online experiment (1548 participants in the United Kingdom). In 9 media narratives, we varied the type of actors responsible for fisheries bycatch (e.g., consumers and industry) and victims (e.g., a single species, multiple species, and ecosystems) in media narratives and determined the effects of the narratives on participants' support for bycatch policies and intentions to alter fish consumption. When responsibility for negative effects was attributed to consumers and industry, the probability of participants reporting support for fisheries policies (e.g., bycatch enforcement or consumer taxes) was ∼30% higher (odds ratio = 1.32) than when only consumers were attributed responsibility. These effects were primarily driven by female participants. Narratives had no effect on personal intentions to consume fish. Varying the type of victim had no effect on policy support and intentions. Our results suggest that neither responsibility diffusion nor compassion fade automatically follows from increasing the types of actors and victims in media narratives and that effects can depend on the type of outcome and population subgroup.

Overfishing drives over one-third of all sharks and rays toward a global extinction crisis

The scale and drivers of marine biodiversity loss are being revealed by the International Union for Conservation of Nature (IUCN) Red List assessment process. We present the first global reassessment of 1,199 species in Class Chondrichthyes-sharks, rays, and chimeras. The first global assessment (in 2014) concluded that one-quarter (24%) of species were threatened. Now, 391 (32.6%) species are threatened with extinction. When this percentage of threat is applied to Data Deficient species, more than one-third (37.5%) of chondrichthyans are estimated to be threatened, with much of this change resulting from new information. Three species are Critically Endangered (Possibly Extinct), representing possibly the first global marine fish extinctions due to overfishing. Consequently, the chondrichthyan extinction rate is potentially 25 extinctions per million species years, comparable to that of terrestrial vertebrates. Overfishing is the universal threat affecting all 391 threatened species and is the sole threat for 67.3% of species and interacts with three other threats for the remaining third: loss and degradation of habitat (31.2% of threatened species), climate change (10.2%), and pollution (6.9%). Species are disproportionately threatened in tropical and subtropical coastal waters. Science-based limits on fishing, effective marine protected areas, and approaches that reduce or eliminate fishing mortality are urgently needed to minimize mortality of threatened species and ensure sustainable catch and trade of others. Immediate action is essential to prevent further extinctions and protect the potential for food security and ecosystem functions provided by this iconic lineage of predators.