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Study Finds Staggering Decline in Marine Fishery Biomass

https://www.geographyrealm.com/study...shery-biomass/

When a study claiming that marine fisheries were going to be completely depleted by 2048 first appeared 14 years ago, the idea still seemed to be in the domain of apocalyptic sci-fi.

However, the new 2020 research confirms that we are, unfortunately, rushing towards the foreseen scenario.

The team assessed biomass of over 1320 fish and invertebrate populations of 483 species, inhabiting the 232 coastal marine ecoregions around the world. The focus was specifically on species known to be exploited by fisheries.

The trends were derived using the Bayesian CMSY stock assessment method, applied to the global fisheries 1950–2014 catch database for every maritime fishing country. The database was reconstructed by the Sea Around Us, a research initiative at The University of British Columbia, to improve current issues in fish catchment statistics.

The mechanism behind the plummeting numbers is simple: seafood is being caught at rates that exceed its capacity to replenish. Consequently, the fishers are catching fewer animals over time, despite fishing longer and harder.

Of all the analyzed populations, 82 percent are below the levels that produce maximum sustainable yields. Out of these, 87 percent are in the “very bad” category, with biomass levels of less than 20% of the biomass needed for maximal sustainable fishery catches.

The greatest declines were found in the southern temperate and polar Indian Ocean and the southern polar Atlantic. Since 1950, fishery populations there has shrunk by over 50 percent.

One of the rare regions that are bucking the trend, having higher fishery biomass than in the 1950s, in the northern Pacific – specifically the polar-boreal zone. In polar and subpolar zones, the population biomass increased by an impressive 800 percent. In the temperate zone, the increase is more modest but still substantial – around 150 percent.

The authors suggest that the positive impact on fish populations occurred due to environmental changes in the region, in combination with sensible fisheries management.

However, although they have something to teach us about the value of good management, the improvements in few locations remain an almost incidental exception in a concerning big picture.