| Popis: |
This study explores the information contained in commercial catches of demersal fisheries off Brazil to address and evaluate possible trends and tipping points in marine ecosystem changes. The analysis included the computation of “mean temperature of the catch - MTC” from inferred temperature preference of species in the catch, weighed by their annual catch. The premise of this method is that, as ocean temperature increases over time, isotherms move poleward expanding latitudinal distribution of warm water species, while contracting the distribution range of cold-water species. In tropical – subtropical transition areas marine communities would gradually become dominated by warm-water species, increasing their presence in the catch compositions of long-standing multispecies fisheries. This hypothesis is supported by preliminary results of an MTC time-series computed annually between 2000 and 2019 off Brazil (iAtlantic Study region 10), which exhibited a significant increasing trend, as explained by declines in catches of cold-water species such as monkfish (Lophius gastrophysus) and the Argentinian hake (Merluccius hubbsi), and increases in catches of tropical fish, including the grey triggerfish (Balistes capriscus). In addition, MTC temporal trend increased significantly from 2011 onwards, suggesting an important discontinuity in that year. This work will continue exploring correlations between MTC and INALT-derived bottom temperatures, and the spatial structure of MTC variability. In addition, further applications of MTC time-series analysis will be conducted on oceanic pelagic fisheries of the SW Atlantic. |
