 |
Publications
Francesco Ferretti, Ransom A. Myers, Fabrizio Serena and Heike K. Lotze
Loss of large predatory sharks from the Mediterranean Sea, Conservation Biology, 2008.
Abstract:
Evidence for severe declines in large predatory fishes is increasing around the world. Because of its
long history of intense fishing, the Mediterranean Sea offers a unique perspective on fish population declines
over historical timescales. We used a diverse set of records dating back to the early 19th and mid 20th century
to reconstruct long-term population trends of large predatory sharks in the northwestern Mediterranean Sea.
We compiled 9 time series of abundance indices from commercial and recreational fishery landings, scientific
surveys, and sighting records. Generalized linear models were used to extract instantaneous rates of change
from each data set, and a meta-analysis was conducted to compare population trends. Only 5 of the 20
species we considered had sufficient records for analysis. Hammerhead (Sphyrna spp.), blue (Prionace glauca),
mackerel (Isurus oxyrinchus and Lamna nasus), and thresher sharks (Alopias vulpinus) declined between 96 and
99.99% relative to their former abundance. According to World Conservation Union (IUCN) criteria, these
species would be considered critically endangered. So far, the lack of quantitative population assessments
has impeded shark conservation in the Mediterranean Sea. Our study fills this critical information gap,
suggesting that current levels of exploitation put large sharks at risk of extinction in the Mediterranean Sea.
Possible ecosystem effects of these losses involve a disruption of top-down control and a release of midlevel
consumers.
|
