Monday 8 November 2010

Oils spills versus fishing

Surprisingly, the Gulf of Mexico oil spill may have been the best thing for lots of fishes. Why? Because it shut down the fishery.
Valentine’s research, which consists of trawl surveys in Mobile Bay, Mississippi Sound and around the barrier islands shows a roughly threefold increase in what the nets captured after the spill compared to before, in terms of both the weight of the catch and the number of animals caught. Valentine said it was possible seasonal factors played a role in the changes in the data, though he believed the lack of fishing was the key.


“The problem with the fishing closure, that impact is so large it is probably going to swamp any impact of the oil spill,” Powers said. “We’re not saying we didn’t lose any fish to the spill or the contaminants. We’re saying it is going to be harder to detect any smaller changes due to oil spill contamination. We’ll have to look carefully.”
Read that again. The Gulf of Mexico, plus oil spill minus fishing, has three times as much fish as it had with no oil spill but with fishing.

The American part of the Gulf is under a quota management system; I don't know how the rest of the Gulf is managed.

Lessons, if these results hold up:
  • The Gulf fishery is rather resilient.
  • BP ought to shell out for lost earnings during the fishing ban, but it doesn't look like there will be any long term negative effect on fish stocks.
  • In a rational world, fishermen would do better to highlight the economic costs to them of the oil spill than the environmental costs to the Gulf if commercial fishing reduces fish stocks by an awful lot more than oil spills.
  • Evidence of stock tripling is not evidence that ex ante quotas were too high, but will be interesting data to feed into models of optimal catch rates. If anything, it's probably evidence that the ex ante quota was pretty sustainable. The fisheries economists will be drooling over this: they've now an experiment showing the effects on fish stocks of a total fish ban, with a bit of oil and dispersant contamination. This ought give them a better handle on actual resource replacement rates.
The punchline of all this should be that global commons problems in fisheries are very likely worse than the effects of any other kind of pollution on global fish stocks.

I wonder whether future Seasteads will be able to claim 300 mile limits and implement innovative property rights mechanisms in fisheries. How many Seasteads would we need to replace a global commons problem with a global PD game?

HT: Scott Beaulier's shared items


  1. The Gulf of Mexico, plus oil spill minus fishing, has three times as much fish as it had with no oil spill but with fishing.

    Of course a true measure of the impact of fishing would be GoM - fishing vs GoM + fishing, where the spill isn't a contributing factor. I imagine it is difficult to say for sure what the true impact of the oil spill is on fish stocks, that would be found by comparing GoM + fishing + oil vs GoM + fishing - oil. We'll never really know for sure, but the greeny lurking beneath my surface suspects it had at least some significant short-term impact. Luckily nature seems pretty resiliant...

  2. @Lats: Well, yeah, but you can't run that experiment. We can say that the oil spill had far far far less effect than fishing did.