People who fish for a living pursue top profits, not necessarily top predators, according to the first-ever analysis of worldwide catch and economic data for the past 55 years.
This differs from the observation raised 10 years ago that humans were "fishing down" the food web. It was assumed that catches of the predators at the top of the food chain, such as halibut and tuna, were declining after fishers started landing more fish from lower on the food chain, such as herring and anchovies.
The idea was that people had targeted fish at top of the food web causing declines that forced harvests of fish at ever lower "trophic levels" in the food web. Proponent of the idea at the time wrote, "If we don't manage this resource, we will be left with a diet of jellyfish and plankton stew."
Fishing down the food web has been debated by biologists and fisheries managers since the idea emerged. However, some in the news media, as well as a number of conservation groups and individuals, accepted the hypothesis without question, according to Suresh Sethi, a University of Washington doctoral student in aquatic and fishery sciences.
"We wanted to examine why fishermen might be motivated to preferentially harvest different trophic levels and our data showed that fishing down the food web by moving from higher to lower value species is an incomplete story of the evolution of global fishery development," says Sethi, lead author of a paper on the subject published this week in the early edition of the Proceedings of the National Academy of Sciences. "We found no evidence that humans first developed commercial fisheries on top predators then sequentially moved to species lower in the food web since the 1950s. Instead, those who fish for a living have pursued high revenue fisheries, no matter what the tropic level of the species."
It's important to know what motivates those who fish for a living as nations move toward ecosystem-based management
|Contact: Sandra Hines|
University of Washington