By MarEx 2018-12-12 18:19:29
A pioneering study by French, Scottish and Canadian researchers has found that industrial fisheries are competing with seabirds for seafood resources, and that a corresponding decline in available food may be a contributing factor in the birds' plummeting population numbers.
The new report was published in the latest edition of Cell Press' Current Biology, and it finds that seabird fish consuption decreased by nearly 20 percent between two twenty-year periods, from 1970-89 and 1990-2010. Between the same time periods, global catch doubled; in the fisheries competing geographically with seabirds, it rose by 10 percent.
The team found enhanced competition between birds and fishing boats in half of all studied areas, notably the Southern Ocean, Asian littorals, Mediterranean Sea,
Norwegian Sea, and California coast. The team described the competitive pressure as a "severe constraint" on seabird populations, which have declined by 70 percent between 1950 and 2010. Seabirds are now considered the most threatened bird group.
The study relies on a library of population data representing about 60 percent of the world's seabirds . Based on regional population numbers, species-specific counts and metabolic rates, the team estimated that the bird's overall food consumption fell by 19 percent between the two periods reviewed. Populations in the Southern Ocean and North Atlantic were particularly affected, and diving petrels, frigatebirds and terns were the species hardest hit. The research team compared this inferred consumption data with fishery records covering the same geographic range to determine the proportion of the take captured by each.
While many other factors have had an impact on bird populations - like bycatch, habitat reduction, climate change, pollution and ocean plastics - the authors noted other regional studies that show fishing's impact on seabird populations. "Competition with fisheries should . . . be regarded as one of the numerous stressors acting upon the fitness of individual seabirds and, ultimately, upon population trajectories. As our study indicates, this threat should not be neglected as it is substantial and global," the researchers concluded.
“You have more and more fishing effort for less and less potential seabird prey, consumed by fewer birds,” said lead author David Grémillet, a scientist with France's National Center for Scientific Research (CNRS), in a statement. “The noose is tightening around seabirds - I find this terrifying.”