A new paper released by the PNAS (Proceedings of the National Academy of Sciences of the USA) has shown that in ocean regions that are intensively managed, fisheries are recovering and harvest rates going down.
This is one key-result in the paper researched by leader Ray Hilborn, Ricardo Oscar Amoroso, Christopher M. Anderson, Julia K. Baum, Trevor A. Branch, Christopher Costello, Carryn L. de Moor, Abdelmalek Faraj, Daniel Hively, Olaf P. Jensen, Hiroyuki Kurota, L. Richard Little, Pamela Mace, Tim McClanahan, Michael C. Melnychuk, Cóilín Minto, Giacomo Chato Osio, Ana M. Parma, Maite Pons, Susana Segurado, Cody S. Szuwalski, Jono R. Wilson, and Yimin Ye.
The significance of the paper is that it compiles estimates of the status of fish stocks from all available scientific assessments, comprising roughly half of the world’s fish catch, and shows that, on average, fish stocks are increasing where they are assessed. We pair this with surveys of the nature and extent of fisheries management systems, and demonstrate that where fisheries are intensively managed, the stocks are above target levels or rebuilding. Where fisheries management is less intense, stock status and trends are worse. We review evidence on the half of world fisheries that are not assessed or intensively managed and suggest their status is much worse than where fisheries are intensively managed.
Trevor A Branch, one of the co-authors explained the scientific approach to the project.
“It took 10 years to compile all the data from 880 fisheries, which together caught almost half of all ocean landings.” he said.
On the chart below Trevor explained “Trends in ocean fisheries vary across regions, but those with intensive management usually saw rebuilding of fish numbers (orange), and declines in harvest rates (green). Less managed areas are doing much worse: 3X higher harvest pressure, and half the fish numbers.”
“A key result from the paper: fisheries with high biomass and high fishing pressure usually declined (red); while those with low biomass and low fishing pressure increased (blue). The line is the theoretical increase-decrease border, matched very well by observed data (colors)”
“Among ocean regions doing badly in 2000, with more than five overfished stocks, nearly all have experienced recovery since that time”
align=”alignnone” width=”584″] Figure 5[/caption]
In 2019, the RAM Legacy Stock Assessment Database contained biomass trends for stocks constituting 49% of the global marine landings reported to the Food and Agriculture Organization (FAO) between 1990 and 2005. Most of the catch in North and South America, Europe, Japan, Russia, Northwest Africa, South Africa, Australia, New Zealand, and RFMO-managed tuna fisheries are included in the database. With the exception of the major tuna stocks and the catch locations listed here, we have no assessments from South and Southeast Asia, China, the Middle East, Central/Eastern Africa, or Central America in the database. Even for regions where almost all catches are represented in the database, the coverage is much better for large, commercially important stocks, and many small stocks remain unassessed, mirroring the findings from a detailed analysis of US fisheries.
If you want to read more on the paper you can do so at https://www.pnas.org/content/early/2020/01/07/1909726116