The weight of fish in the northwest Pacific Ocean decreased in the 2010s because the fish food supply is fleeing to colder seas due to warming water, according to a published University of Tokyo study. this week.
This conclusion is drawn after researchers analyzed the individual weight and overall biomass of 13 fish species. Weight refers to individual fish (e.g. a 200 gram mackerel), while biomass is the total weight of a species or group in an area (e.g. 50,000 tonnes of mackerel). The results indicate that in the 1980s and 2010s, fish were lighter. The researchers attribute the first period of weight loss to the presence of greater numbers of Japanese sardines, which increased competition with other species for food.
During the 2010s, while the number of sardines and Japanese mackerel increased moderately, the effect of climate change, which warms the ocean, appears to have also resulted in greater competition for food, as colder, more carbon-rich water Nutrients could not easily rise to the surface.
These results have implications for fisheries and policymakers trying to manage ocean resources under future climate change scenarios. The research focused on the study of long-term data from six fish populations of four species between 1978 and 2018, and medium-term data from 17 fish populations of 13 species from 1995/1997 to 2018. Data from sea water temperature between 1982 and 2014. to see if changes in the surface and subsurface layers of the ocean may have had any impact.
As reported by the University of Tokyo, the results showed two periods of reduced fish body weight, first in the 1980s and again in the 2010s. The team attributed the weight decline of the 1980s to an increase in the Japanese sardine, which likely led to increased competition for food within and between fish species.
In comparison, in the 2010s, although there was a moderate increase in the population of Japanese sardine and mackerel, the team's analysis appeared to show that the reduction in the supply of nutrients to the surface of the ocean from the subsurface layers, due to the effect of the global warming in the ocean, was an influential factor.
Researchers hope fishery managers and policymakers will use findings like this to better understand the changes occurring in the oceans around Japan and help make informed decisions for the future.
