Scientists from the Future of Marine Animal Populations (FMAP) project of the Census of Marine Life program have identified an alarming trend in the populations of large predatory fishes in the world's oceans. FMAP scientists claim that up to 90% of all large predatory fish such as cod, sharks, halibut, grouper, tuna, swordfish, and marlin have been depleted. Since 1950, with the onset of industrialized fisheries, the entire fisheries resource base has been reduced to less than 10% worldwide.
Inspired by similar analytical studies that have been performed on data regarding terrestrial species, this study investigated the species density of fish catch around the world. Published as the cover story of the May 15th, 2003 issue of Nature (Vol. 423, pp 280-283, 2003) the FMAP study analyzed the data from all major fisheries in the world including, most notably, many years of Japanese longlining data. These longlining data are key because they represent a widespread gear type, an extremely large fleet, and a consistent method that is utilized in almost every sea in the world. Additionally, pelagic longlining tends to target large predatory fish, thus giving insight into the depletion of higher trophic level species that often act as indicators of the health and balance of the overall ecosystem. Another alarming aspect of this study is the understanding that since the onset of industrialized fishing, the efficiency of the technology used has grown. If catch has declined from catching 10 fish per 100 hooks to 1 fish per 100 hooks in a fishery where efficiency has increased, it can be concluded that the fishery is suffering more than it appears when you look at the numbers out of context.
While most fisheries managers would agree that the global condition of fish stocks is in decline, some still find it hard to accept the results of this study as it pertains to individual species. However, scientists contend that the sustainability of fisheries is being severely compromised worldwide. Rebuilding fish stocks may be the best course of action, however, the sacrifices necessary to do so will hurt those who rely on the fish stock the most: the fishermen.
More information on this discovery is available in the full published article: Global patterns of predator diversity in the open oceans. Science 309:1365-1369.