The most widely adopted measure for assessing the state of the world's oceans and fisheries led to inaccurate conclusions in nearly half the ecosystems where it was applied.
The new analysis was performed by an international team of fisheries scientists, and is reported in this week's issue of the journal Nature.
"Applied to individual ecosystems it's like flipping a coin; half the time you get the right answer and half the time you get the wrong answer," said Trevor Branch, a University of Washington (UW) aquatic and fisheries scientist.
"Monitoring all the fish in the sea would be an enormous, and impossible, task," said Henry Gholz, program director in the National Science Foundation (NSF)'s Division of Environmental Biology, which co-funded the research with NSF's Division of Ocean Sciences.
"This study makes clear that the most common indicator, average catch trophic level, is a woefully inadequate measure of the status of marine fisheries."
In 1998, the journal Science published a groundbreaking paper that was the first to use trends in the trophic levels of fish that were caught to measure the health of world fisheries.
The trophic level of an organism shows where it fits in food webs, with microscopic algae at a trophic level of one and large predators such as sharks, halibut and tuna at a trophic level around four.
The 1998 paper relied on four decades of catch data and averaged the trophic levels of what was caught.
The authors determined that those averages were declining over time and warned we were "fishing down the food web" by overharvesting fish at the highest trophic levels and then sequentially going after fish farther down the food web.
Twelve years later newly compiled data has emerged that considers the numbers and types of fish that actually live in these ecosystems, as well as catch data.
The new analysis reveals weaknesses in assessin
|Contact: Cheryl Dybas|
National Science Foundation