Collapse and recovery of seafood wholesale prices in time of COVID-19.

The COVID-19 pandemic has spread around the world, disrupting economies, societies and daily life. Early research anticipated significant negative impacts for the globalized seafood supply network. Here, we explore the impact of the COVID-19 pandemic on wholesale prices from five major seafood markets around the world. An anomalies analysis was used to establish a 5-year baseline price for each commodity. Daily price data from 2020 were compared to the baseline to identify collapses (>1.96 SE from baseline) and analyse collapse characteristics (timing, duration and magnitude). Non-uniform price collapses were observed across, and within, the markets analysed. Toyosu (Tokyo) Market experienced price collapses to 51% of commodities, Rungis (Paris) 36%, Mercamadrid (Madrid) 19%, Mercado La Nueva Viga (Mexico City) 35% and the Portland Fish Exchange (Portland, Maine) 32%. Collapse magnitude varied from 11% to 79% of the 5-year average price. Average collapse duration ranged from 13 to 24 weeks with some commodities (4%-22%) remaining collapsed at the end of 2020. For markets where volume data were available, collapses were also noted (59% of commodities in Toyosu, 10% in Mercamadrid and 19% in Portland Fish Exchange); in these cases, the volume collapse was more severe than the related price collapse. To better detect, anticipate and respond to future shocks, we recommend that relevant government agencies conduct comprehensive economic reviews of the COVID-19 pandemic throughout the seafood supply chain, including the outcomes of emergency measures, short- and long-term implications of market volatility and identify areas of supply and labour vulnerabilities.

Energy Flow Through Marine Ecosystems: Confronting Transfer Efficiency.

Transfer efficiency is the proportion of energy passed between nodes in food webs. It is an emergent, unitless property that is difficult to measure, and responds dynamically to environmental and ecosystem changes. Because the consequences of changes in transfer efficiency compound through ecosystems, slight variations can have large effects on food availability for top predators. Here, we review the processes controlling transfer efficiency, approaches to estimate it, and known variations across ocean biomes. Both process-level analysis and observed macroscale variations suggest that ecosystem-scale transfer efficiency is highly variable, impacted by fishing, and will decline with climate change. It is important that we more fully resolve the processes controlling transfer efficiency in models to effectively anticipate changes in marine ecosystems and fisheries resources.

Global change in the trophic functioning of marine food webs.

The development of fisheries in the oceans, and other human drivers such as climate warming, have led to changes in species abundance, assemblages, trophic interactions, and ultimately in the functioning of marine food webs. Here, using a trophodynamic approach and global databases of catches and life history traits of marine species, we tested the hypothesis that anthropogenic ecological impacts may have led to changes in the global parameters defining the transfers of biomass within the food web. First, we developed two indicators to assess such changes: the Time Cumulated Indicator (TCI) measuring the residence time of biomass within the food web, and the Efficiency Cumulated Indicator (ECI) quantifying the fraction of secondary production reaching the top of the trophic chain. Then, we assessed, at the large marine ecosystem scale, the worldwide change of these two indicators over the 1950-2010 time-periods. Global trends were identified and cluster analyses were used to characterize the variability of trends between ecosystems. Results showed that the most common pattern over the study period is a global decrease in TCI, while the ECI indicator tends to increase. Thus, changes in species assemblages would induce faster and apparently more efficient biomass transfers in marine food webs. Results also suggested that the main driver of change over that period had been the large increase in fishing pressure. The largest changes occurred in ecosystems where 'fishing down the marine food web' are most intensive.