Loss of Large Predatory Sharks from the Mediterranean Sea

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.

Retained fishing gear and associated injuries in the east Australian grey nurse sharks (Carcharias taurus): implications for population recovery

“…The viability of certain shark populations is of global concern (Robbins et al 2006;Dulvy et al 2008;Ferretti et al 2008). Many shark species that are targeted commercially, caught and harvested as bycatch, or captured incidentally and released by recreational or commercial fishers are at risk of over-exploitation and possible extinction (Baum et al 2005;Campana et al 2006;Myers et al 2007).…”

Acoustic telemetry and network analysis reveal the space use of multiple reef predators and enhance marine protected area design

“…For instance, catch rates for some shark species in the Atlantic Ocean are estimated to have declined by over 90% [12,23], with similar declines (more than 70%) also indicated for the Pacific Ocean [22,24]. Data on Indian Ocean shark populations are severely deficient by comparison, but available reports suggest declines in this region (e.g.…”

“…Fishing pressure on sharks has increased to the point where an estimated 63-273 million sharks are caught each year [11], with some populations appearing to have undergone significant declines [12,13]. A common tool to combat overfishing, especially in tropical ecosystems, is the designation of marine protected areas (MPAs), which can be very effective, depending on their size, level of restriction and associated enforcement [14,15].…”

Analysis of swordfish Xiphias gladius and blue shark Prionace glauca fisheries by Catalan longline fleet from 2010 to 2015 in the occidental Mediterranean Sea

“…Según la clasificación de la IUCN (Unión Internacional para la Conservación de la Naturaleza), la tintorera, en el Mediterráneo, está en la categoría 'en peligro crítico' (Dulvy et al 2016). Hay antecedentes que sobre el 98% de la biomasa de la tintorera habría desaparecido en el Mediterráneo durante el último siglo debido a la sobrepesca (Ferretti et al 2008).…”