It paints a different picture from previous catch data and has revealed another major new finding: on a global scale humans don't appear to be fishing down the food web, Branch said.
"The research shows the importance of synthesis to furthering an understanding of fisheries impacts and management strategies," said Phillip Taylor, section head in NSF's Division of Ocean Sciences.
"For complex ecosystem interactions, answers can only come from repeated scrutiny of data, and comparisons of different scientific methods and systems," said Taylor. "This synthesis points to a path forward to evaluate fisheries influences on ocean ecosystems."
The new catch data reveal that, following declines during the 1970s in the average trophic levels of fish being caught, catches of fish at all trophic levels have generally gone up since the mid-80s.
Included are high-trophic predators such as bigeye tuna, skipjack tuna and blue whiting.
"Globally we're catching more of just about everything," Branch said. "Therefore relying on changes in the average trophic level of fish being caught won't tell us when fishing is sustainable--or if it is leading to collapse."
When harvests of everything increase equally, the average trophic level of what is caught remains steady. The same is true if everything is overfished to collapse. Both scenarios were modeled as part of the analysis.
"The 1998 paper was tremendously influential in gathering together global data on catches and trophic levels, and it warned about fishing impacts on ecosystems," Branch said.
"Our new data from trawl surveys and fisheries assessments now tell us that catches weren't enough. In the future we will need to target limited resources in the best way, focusing on species that are especially vulnerable to fishing and developing indicators that reflect fish abundance, biod
|Contact: Cheryl Dybas|
National Science Foundation