The silky shark Carcharhinus falciformis (c) Hilton/Greenpeace
Silky Shark (Carcharhinus falciformis)
The silky shark has a cosmopolitan distribution and can be found around the world in tropical waters. It is most often found near the edges of continental shelves, from the surface to a depth of 50 m. It can grow to a length of 2.5 m (8.2 ft) and has a metallic bronze-gray colour on its upper body.
It is a mobile predator that feeds on bony fishes and cephalopods, and aggregations of silky sharks are often found trailing schools of tuna. As a consequence it is one of the most common shark species caught as bycatch in tuna longline and purse seine fisheries operating throughout its range. This species is hunted for its fins, with much of the product being sold at the Hong Kong shark fin market.
Data now suggest that silky shark numbers are declining in many areas, and the IUCN assessed the global silky shark population as being Near Threatened.
Coconut Crab (Birgus latro)
Coconut Crab (Birgus latro)
The coconut crab is the world’s largest terrestrial arthropod, reaching over one metre in leg span and 3.5-4 kilos in weight. As a juvenile it behaves like a hermit crab and uses empty coconut shells as protection but as an adult this giant crab climbs trees and can crack through a coconut with its massive claws.
Despite its wide global distribution, it is rare in most of the areas it is found. It is primarily threatened by over-collection for food, but also as ornaments for sale to tourists and as bait for fish traps. Demand for coconut crabs as souvenirs is strong, and other threats include habitat destruction and predation from introduced species such as rats.
The coconut crabs on Chagos constitute one of the most undisturbed populations in the world. An important part of their biology is the long distances their young can travel as larvae. This means the Chagos coconut crabs are a vital source for replenishing other over-exploited populations in the Indian Ocean region.
Bigeye tuna (Thunnus obesus) caught on a longline. (c) Sutton-Hibbert/Greenpeace
Bigeye tuna (Thunnus obesus)
Bigeye tuna (Thunnus obesus) are deep water fish, occupying almost all the world’s oceans within about 45º of the equator. With a diet of fish, cephalopods and crustaceans, and a migratory nature, the adults roam deeper waters whilst juveniles often associate with floating objects acting as fish aggregation devices.
As one of the larger tuna-fishes they can reach 2.5m in length with up to 200kg of high performance muscle. Tunas have an unusual amount of red, blood-rich sprinting muscle (hence the colour of sashimi) which makes them some of the fastest fish in the oceans.
Bigeye tuna are one of the most sought after and commercially important species of tuna, and as such, the IUCN lists them as Vulnerable and many stocks globally show signs of depletion.
