Bycatch in the context of "Bird conservation"

Longline fishing, or longlining, is a commercial fishing angling technique that uses a long main line with baited hooks attached at intervals via short branch lines called snoods or gangions. A snood is attached to the main line using a clip or swivel, with the hook at the other end. Longlines are classified mainly by where they are placed in the water column. This can be at the surface or at the bottom. Lines can also be set by means of an anchor, or left to drift. Hundreds or even thousands of baited hooks can hang from a single line. This can lead to the death of many different marine species known as bycatch. Longliners – fishing vessels rigged for longlining – commonly target swordfish, tuna, halibut, sablefish and many other species.

In some unstable fisheries, such as the Patagonian toothfish, fishermen may be limited to as few as 25 hooks per line. In contrast, commercial longliners in certain robust fisheries of the Bering Sea and North Pacific generally run over 2,500 hand-baited hooks on a single series of connected lines many miles in length.

A fishing net or fish net is a net used for fishing. Fishing nets work by serving as an improvised fish trap, and some are indeed rigged as traps (e.g. fyke nets). They are usually wide open when deployed (e.g. by casting or trawling), and then close off when retrieved to engulf and trap fish and other aquatic animals that are larger than the holes/gaps of the net, as well as many unwanted bycatches due to the underwater area a net can cover.

Fishing nets are usually meshes formed by knotting a relatively thin thread, and early nets were woven from grasses, vines, flaxes and other fiber crop material, while later woven cotton was used. Modern nets are usually made of artificial polyamides like nylon, although nets of organic polyamides such as wool or silk thread were common until recently and are still used.

The common stingray (Dasyatis pastinaca) is a species of stingray in the family Dasyatidae, found in the northeastern Atlantic Ocean and the Mediterranean and Black Seas. It typically inhabits sandy or muddy habitats in coastal waters shallower than 60 m (200 ft), often burying itself in sediment. Usually measuring 45 cm (18 in) across, the common stingray has a diamond-shaped pectoral fin disc slightly wider than long, and a whip-like tail with upper and lower fin folds. It can be identified by its plain coloration and mostly smooth skin, except for a row of tubercles along the midline of the back in the largest individuals.

The predominant prey of the common stingray are bottom-dwelling crustaceans, though it also takes molluscs, polychaete worms, and small bony fishes. It is aplacental viviparous: the embryos are nourished by yolk and later histotroph ("uterine milk") produced by the mother. Females bear 4–9 young twice per year in shallow water, after a gestation period of four months. The common stingray can inflict a painful, though rarely life-threatening, wound with its venomous tail spine. During classical antiquity, its sting was ascribed many mythical properties. This species is not sought after by commercial fisheries, but is taken in large numbers as bycatch and utilized for food, fishmeal, and liver oil. Its population is apparently dwindling across its range, and the International Union for Conservation of Nature (IUCN) assesses it as Vulnerable.

Fish meal (sometimes spelled fishmeal) is a commercial product made from whole wild-caught fish, bycatch, and fish by-products to feed farm animals, such as pigs, poultry, and farmed fish. Because it is calorically dense and cheap to produce, fish meal has played a critical role in the growth of factory farms and the number of farm animals it is possible to breed and feed.

Fish meal takes the form of powder or cake. This form is obtained by drying the fish or fish trimmings, and then grinding it. If the fish used is a fatty fish, it is first pressed to extract most of the fish oil.

The vaquita (/vəˈkiːtə/ və-KEE-tə; Phocoena sinus) is a species of porpoise endemic to the northern end of the Gulf of California in Baja California, Mexico. Reaching a maximum body length of 150 cm (4.9 ft) (females) or 140 cm (4.6 ft) (males), it is the smallest of all living cetaceans. The species is currently on the brink of extinction, and is listed as Critically Endangered by the IUCN Red List; the steep decline in abundance is primarily due to bycatch in gillnets from the illegal totoaba fishery.

The dwarf lanternshark (Etmopterus perryi) is a species of dogfish shark in the family Etmopteridae and is the smallest shark in the world, reaching a maximum known length of 20 cm (8 in). It is known to be present only on the upper continental slopes off Colombia and Venezuela, at a depth of 283–439 m (928–1,440 ft). This species can be identified by its small size at maturity, long flattened head, and pattern of black ventral markings and a mid-dorsal line. Like other members of its genus, it is capable of producing light from a distinctive array of photophores. Reproduction is aplacental viviparous, with females gestating two or three young at a time. The dwarf lanternshark is not significant to commercial fisheries, but could be threatened by mortality from bycatch; the degree of impact from human activities on its population is unknown.