The population of Pacific blue sharks has returned to 1970 levels, or is on its way to recovery, despite shark finning practices that have raised a global outcry. The rebounding blue shark population is the result of the 1992 ban on drift netting, said Pierre Kleiber, a fishery biologist with the National Marine Fisheries Service. In a preliminary report presented to the Western Pacific Regional Fishery Management Council on Maui, Kleiber said he studied confidential fishery data from Japan, Taiwan, Vietnam and Hawai ' i-based longline fisheries, and found that catch rates for blue sharks have increased strongly after being depressed apparently by the aggressive drift net fishing in the North Pacific in the 1980s. Estimates for the North Pacific are that drift net fishery used to capture squid killed 2 million to 3 million sharks, most of them blue sharks, each year.
Drift nets are open-ocean nets that are miles long and tens of feet deep.
Before their ban by international treaty, they were portrayed as indiscriminate killers, snagging any marine animals that came by, even though those who used them sought only the squid. Catch rates declined during the height of the drift net fishery, suggesting that blue shark populations were dropping. Depending on how much allowance is given to improving longline fishing techniques, statistical reviews of the 1990s data indicates that shark populations have now risen, Kleiber said. Even if researchers assume the effectiveness of longline fishing has increased dramatically, the figures show shark populations rising. If fishing efficiency is presumed to be roughly level over time, shark populations appear to have returned to pre-drift net levels, he said.