Shark fishing for meat, cartilage and liver oil, and the destruction of important habitats, such as mangrove swamps and shallow lagoons (areas that provide safe havens for juvenile sharks), is having devastating effects on shark populations worldwide. Although almost every large-scale shark fishery ends in collapse, global shark exploitation and trade remain unregulated and no internationally recognised management scheme exists. Some of the most destructive and damaging fishing methods affecting shark populations today include, gill netting, long-lines, trawling, sport fishing and of course finning. It is not only the sharks that are affected by these practices but many other species are also adversely affected including rays, a close relative of the sharks.
Many sharks are caught as accidental bycatch in long-lines, trawls, and nets targeting other species. Bycatch is simply the proportion of unwanted catch returned to the sea after fishing. Sharks are highly migratory and they often swim in groups that are the same size and age. This can mean that a key part of the population (mature females for example) can be wiped out in one fell swoop. Estimates vary, but bycatch (unwanted catch) is expected to account for a significant proportion of shark fatalities. Another problem for sharks, known as ghost fishing, occurs when fishing gear is abandoned and continues to catch whatever swims by. An improvement in the species selectiveness of fishing gear is needed if bycatch figures are to be reduced.
Long-lines are made of monofilament and are used mainly to catch tuna, swordfish and shark. However, they are indiscriminate and catch many animals other than those targeted, including birds, sealions, sharks, dolphins, turtles and more. Also known as 'curtains of death', long lines can range from a metres to kilometres and are kept near the surface using floats made of styrofoam. At intervals of 30 meters or so secondary lines are attached and baited with whatever is at hand; fish, squid or even dolphin meat.
Long-lines are a huge threat to the survival of many species of shark. The vast majority of sharks caught by this method are killed only for their fins; the rest of their body is discarded as "bycatch" and thrown back into the sea. The practice of long-lining is inextricably linked to finning. Long lining has been banned in a few specific areas such as the US Pacific coast because of its huge impact on ocean life, however in the vast majority of areas it is still legal and practiced routinely.