Sumaila responds to Branch et al. in Nature

Economist Rashid Sumaila recently responded to the paper by Trevor Branch and colleagues in the journal Nature:

The trophic fingerprint of marine fisheries’ (Nature, 468, 431-435, 2010), has intensified the debate on how best to measure the impact of commercial fishing on ocean biodiversity: Is catch data useful in telling us what is happening in the ocean or do we need stock assessment information in order to say something meaningful? As an economist, I cannot contribute to this debate but I can ask some questions: What conclusion does one come to if one uses one or the other of these approaches?If one ends up with the same conclusion then the debate is only of academic interest. If the conclusions reached are different, what are the potential costs to the world should one or the other be incorrect? In general, proponents of the use of stock assessments for measuring the ‘health’ of ocean fish populations, led by Ray Hilborn of the University of Washington, conclude that ocean fish populations are doing just fine, while those who use catch data, spearheaded by Daniel Pauly of the University of British Columbia, come to the conclusion that global fish stocks are in bad shape. Depending on which of these two camps wins the argument, the world would either stick to the status quo and continue to manage global fisheries as we currently do, or the world community would double its efforts to manage global fisheries sustainably. Should the former conclusion turn out to be incorrect, the world would have saved some costs by continuing to fish without further management restrictions, with the consequence that ocean biodiversity would be eroded further, thereby supplying less and less fish with time. On the other hand, if the latter turns out to be incorrect, the world would have incurred unnecessary cost due to stricter management but would have an ocean rich in biodiversity that is capable of supplying fish into the future.

Read more on this issue here.

MSC Critique Chosen As Part of Nature’s Top Six of 2010

Seafood stewardship in crisis, by Sea Around Us Project members Jennifer Jacquet and Daniel Pauly, as well as David Ainley, Sidney Holt, Paul Dayton & Jeremy Jackson, was chosen as one of Nature’s top six comment pieces of the year. The piece criticizes recent seafood certifications by the Marine Stewardship Council (MSC) and makes suggestions on how the certification could be improved. Read the full piece here.

Scientific American Article Explores Catch Data Controversy

A recent study by Trevor Branch and colleagues asserted that the decline in the mean trophic index is no longer present in the global catch data. But does it really cast doubt on the depletion of big ocean species?

In an article published today at Scientific American, journalist Mike Orcutt explores how best to measure commercial fishing’s impact on ocean biodiversity. He discusses the findings of Brach et al. in light of the new study quantifying fisheries expansion. Orcutt reports:

Pauly says the new PLoS One paper “completely invalidates” Branch’s Nature paper because the authors failed to account for the spatial expansion described in the former. As fisheries move offshore, he says, they first target large fish high on the food web—just as they did closer to shore. “Hence, moving offshore will mask inshore declines in mean trophic levels.”

Read the full article here.

Photo: Tiny fish caught by a trawler off of Hong Kong by Stanley Shea/BLOOM.

New Study Quantifies Expansion of Fisheries

While it is widely-recognized that fishing boats have moved further offshore and deeper in the hunt for seafood, the Sea Around Us Project, in collaboration with the National Geographic Society, recently published in PloS ONE the first study to quantify global fisheries expansion.

The study reveals that fisheries expanded at a rate of one million sq. kilometres per year from the 1950s to the end of the 1970s. The rate of expansion more than tripled in the 1980s and early 1990s – to roughly the size of Brazil’s Amazon rain forest every year.

Between 1950 and 2005, the spatial expansion of fisheries started from the coastal waters off the North Atlantic and Northwest Pacific, reached into the high seas and southward into the Southern Hemisphere at a rate of almost one degree latitude per year. It was accompanied by a nearly five-fold increase in catch, from 19 million tonnes in 1950, to a peak of 90 million tonnes in the late 1980s, and dropping to 87 million tonnes in 2005. Now we have run out of room to expand fisheries.

The image here (click to enlarge) shows a time series of areas exploited by marine fisheries by latitude class, expressed as a percentage of the total ocean area.