Global Warming and FIsh Migrations
28 May, 2007 12:19 pm
Past variations in ocean climate have affected location and migrations of fish stocks. This indicates that global warming will have similar effects. This could pose difficult challenges for the management of fish stocks that traverse national boundaries in the ocean and which are shared between two or more countries.
The paper looks at a stylized case where a fish stock is displaced from being totally confined to the economic zone of Country A to gradually shifting into the zone of Country B, finally becoming totally confined to the zone of Country B. This process will be irregular with temporary setbacks, because most likely there will be fluctuations in ocean temperature around a warming trend. There will thus be an interim period during which a stock in transition from Country Aís to Country Bís waters will be shared by both. Since it takes time to work out a sharing rule, and furthermore since the migrations, or locations, are changing from year to year because of temperature fluctuations, the stock will be fished competitively and not managed as a whole for some time. During that period, both countries will take whatever they find in their interest, ignoring the repercussions for the other part.
The paper analyzes specifically the case where no agreement will be reached during the period when the stock is in transition and when both countries form symmetric, backward-looking expectations about the distribution of the stock. It is shown that in certain cases the stock could be fished to extinction, while in other cases it could be severely depleted over a long period of time. The actual distribution of the stock in each period is unknown before fishing starts and must be predicted, but becomes known once the period is over. The countries are assumed to revise their expectations about the distribution of the stock on the basis of how it changed in the previous period. The more slowly the countries revise their expectations, the more likely it is that the stock will become extinct as a result of competitive exploitation.
The paper is purely theoretical, but among stocks that might be affected by processes such as analyzed in the paper are California sardine, Pacific hake, Northeast Arctic cod, and Norwegian spring spawning herring.
Hannesson, Rognvaldur. Natural Resource Modeling . 20 , Number 2, Summer 2007. p. 301-319.