s with longline
fishing vessel|alt=Photo of thousands of birds feeding at water surface next to fishing boat Longline fishing is controversial because of
bycatch, fish caught while seeking another species or immature juveniles of the target species. This can cause many issues, such as the killing of many other marine animals while seeking certain commercial fish. Seabirds can be particularly vulnerable during the setting of the line. Methods to mitigate incidental mortality have succeeded in some fisheries. Mitigation techniques include the use of weights to ensure the lines sink quickly, the deployment of streamer lines to scare away birds, lasers, setting lines only at night in low light (to avoid attracting birds), limiting fishing seasons to the southern winter (when most seabirds are not feeding young), and not discharging
offal while setting lines. The
Hawaii-based longline fishery for
swordfish was closed in 2000 over concerns of excessive sea turtle by-catch, particularly
loggerhead sea turtles and
leatherback turtles. Changes to the management rules allowed the fishery to reopen in 2004. Gear modification, particularly a change to large circle-hooks and
mackerel-type baits, eliminated much of the sea turtle by-catch associated with the fishing technique. It has been claimed that one consequence of the closure was that 70 Hawaii-based vessels were replaced by 1,500–1,700 longline vessels from various Asian nations, but this is not based on any reliable data . Due to poor and often non-existent catch documentation by these vessels, the number of sea turtles and
albatross caught by these vessels between 2000 and 2004 will never be known . Hawaii longline fishing for swordfish closed again on 17 March 2006, when the by-catch limit of 17 loggerhead turtles was reached. In 2010 the by-catch limit for loggerhead turtles was raised, but was restored to the former limit as a result of litigation. The Hawaii-based longline fisheries for tuna and swordfish are managed under sets of slightly different rules. The tuna fishery is one of the best managed fisheries in the world, according to the UN Code of Responsible Fishing, but has been criticized by others, as being responsible for continuing by-catch of
false killer whales, seabirds, and other nontargeted wildlife, as well as placing pressure on depleted
bigeye tuna stocks. Commercial longline fishing is also one of the main threats to
albatrosses, posing a particularly serious threat to their survival. Of the 22 albatross species recognized by the
IUCN Red List, 15 are
threatened with extinction. The IUCN lists two species as
Critically Endangered (
Tristan albatross and
waved albatross), seven species as
Endangered, and six as
Vulnerable. These activities, however, are not randomly spread across the vast oceans, but rather are highly spatially concentrated. Therefore, the bird conservation lobby should work closely with
regional fisheries management organizations to devise and implement targeted interventions aimed at reducing potential illegal longline fishing, which, in turn, will likely have positive effects on albatrosses. A simple device which can be fitted onto longlines, known as Hookpod, has been proposed for mitigation of seabird bycatch; Hookpod was rolled out to a total of 15 commercial fishing vessels in New Zealand after a change in regulations in January 2020, with a result of zero seabird
bycatch in the first 6 months. == Plastic pollution ==