What Happens To Fish When There Is Less Fishing? A Q&A With Ragnar Arnason

February 14, 2017

Ragnar Arnason, professor in the Faculty of Economics at the University of Iceland, is the author of the bio-economic model used in The Sunken Billions Revisited, published by the World Bank. We asked him a few questions on the occasion of the report launch.

1. The Sunken Billions Revisited suggests that by reducing fishing effort by 44 percent, the biomass of fish would theoretically increase by a factor of 2.7 and annual harvests would increase by 13 percent. Can you walk us through this scenario? What happens to fish when there is less fishing?

Reducing fishing effort reduces fishing mortality and reduces the negative ecosystem and environmental impacts associated with fishing. All these factors contribute to larger and healthier fish stocks:  

  • Reduced fishing mortality leads to increased fish stocks: Fish live longer and reach larger sizes, which is good for fisheries since larger fish are generally more valuable and no more expensive to catch than smaller fish. Spawning is also generally enhanced and becomes more reliable because more fish survive to become spawners.
  • Fishing generally focusses on relatively few species in the marine ecosystem, which creates a certain imbalance in the ecosystem. The more fish stocks are reduced, the greater this imbalance. Therefore, reduced fishing effort and restored commercial stocks contribute to a more balanced and, presumably, healthier ecosystem.
  • Fishing generally has negative environmental impacts – the extent of which depends strongly on the level of fishing effort and the fishing method. Reducing fishing effort reduces the negative environmental impacts, which further contributes to a more robust ecosystem and stronger fish stocks.

Larger stocks can sustain higher catches as well as allowing more stable catches over time.  Therefore, reduced fishing effort leads to higher sustainable catches, up to the maximum sustainable yield.

2. How quickly can this type of recovery occur?

When fishing effort is reduced, the biological and economic benefits will not appear right away. Initially as fishing effort is reduced, catches go down because the stock has not had time to recover. As time passes, however, the stock improves, catches gradually increase and eventually the stock may have increased so much that catches are higher in spite of lower fishing effort. Catch “bounce back” will be more pronounced in the case of fisheries that were previously heavily overexploited.

In The Sunken Billions Revisited, we acknowledge that there are different possible paths from the current state of the world's fisheries to the optimal sustainable state. Particular fish stocks should be rebuilt over time, according to their biological reproductive processes and the social and economic characteristics of fisheries. The pace of fisheries reform has to be well thought out and the appropriate measures taken to alleviate possible hardship during the initial adjustment phase of fishing effort.

3.  What are some of the factors limiting reform? Is recovery of the ‘sunken billions’ possible in practice?

In my view, the main barriers to restoring global fish stocks and securing high sustainable economic benefits from fisheries are firstly the political willingness and secondly the ability of nations to constrain fishing effort and introduce effective fisheries management systems. These two obstacles are related because political willingness depends at least partly on the ability to implement and enforce new rules.

High-income countries and international development agencies can lower these barriers for low- and middle-income countries by providing technical assistance in fisheries management and financial assistance to build fisheries management capacity and meet the temporary dip in catches due to reduced fishing effort. Experience shows it can be done. We’ve already seen greatly improved fisheries management in places like Chile and Peru (Pelagic stocks), and Namibia (hake).

The alternative is doing nothing and continuing to let too many vessels chase too few fish in places where fisheries management is weak or even non-existent. We may see a further significant decline in sustainable catches and threat to the food security and livelihoods of populations who rely on fishing unless we invest in fisheries management. By investing in reform, it’s possible to derive much more value from fisheries and support long-term jobs and economic development.