18/12/2015: New report suggest world fish stocks are decreasing

According to an article recently published by Weather.com, the study that featured in the prestigious peer-reviewed journal Proceedings of the National Academy of Sciences, specifically notes that the global distribution of certain species has changed. In the future, their ability to reproduce efficiently might be hampered as well, the study found.

"We think it is a lack of food availability for these small fish," lead author Gregory L. Britten, a doctoral student at the University of California, Irvine, told NPR. "When fish are young, their primary food is phytoplankton and microscopic animals. If they don't find food in a matter of days, they can die."

In total in this study, 127 species were examined through a global meta-analysis. Across the regions and species studied, the average recruitment (or ability to produce viable offspring) was projected to drop 3 percent. But while the global average saw a decline in fish recruitment, some species might increase in population due to climate change, the paper noted.

“There's a lot of variability around that 3 percent,” Jon Hare, supervisory research oceanographer at the Northeast Fisheries Science Center, a division of NOAA Fisheries, who did not work on the study, told weather.com. “Some stocks are going to experience even greater decline, and some stocks are going to experience lower declines and also, potentially, increases.”

Hare said in the Northeastern United States the Atlantic croaker, for example, might do well in warmer conditions.

“One of the regulation mechanisms for Atlantic croaker is overwinter survival, so in a very cold winter, fewer young fish survive,” he said. “As winters have warmed, that's meant that more and more young fish are surviving.”

Although Hare said the new study adds an important element to the global discussion, individual species analysis is key to fishery management. That's one reason NOAA recently completed a vulnerability assessment for fish stocks in the Northeastern U.S., examining 82 species individually and making projections about the effect of future climate change. There's also a new online database tracking population movements to help fisheries respond.

At this point, all estimates of future fish populations are just that: estimates. Currently, we have a good idea of how climate change will impact fish 20, 30, even 50 years into the future, and we know we need to respond, Hare said. But beyond that, it's difficult.

“When you get beyond 50 years, that's when it really becomes dependent on the choices we make now in terms of CO2 emissions,” he noted.

Britten told NPR that the study's findings on fish reproduction should aid future fish management to lessen climate change's impact.

"It's no longer just pull back on fishing and watch the stock rebound," he said. "It's also a question of monitoring and understanding the ability of stocks to rebound, and that's what we demonstrated in this study."