The Challenge Depending on their design, where they’re utilised, and what they’re catching, different types of fishing gear can have a variety of effects. This is why, depending on how a species was taken, it may have varied sustainability rankings or eco-certifications. Similarly, various species caught with the same type of gear may pose distinct sustainability challenges.
Fisheries should employ gear that has the least amount of negative influence on the target species and the marine ecology. By adding “escape zones” or excluder devices to nets, for example, to allow unwanted species to escape, some gear types with bycatch difficulties can be changed to reduce these consequences. To prevent marine mammal entanglements, another improvement could be to use traps with submerged (rather than floating) lines. Some gear types, such as hook-and-line or diving for nearshore species, are intrinsically more selective and have a smaller impact.
The Atlantic Canadian
The Atlantic Canadian swordfish fishery is a good example of how differing gear can have a big impact on bycatch. Longlines and harpoons are the two types of gear used in commercial fishing. While bycatch is essentially non-existent in the harpoon fishing since each swordfish is specifically targeted, the longline fishery has been known to catch more bycatch — primarily turtles and sharks – than swordfish.
Nets come in a variety of sizes and shapes. Others are used actively (fixed, enabling fish and other creatures to swim into them), while others are used passively (fixed, allowing fish and other animals to swim into them) (mobile, dragged through the water). Trawl nets, dredges, beach seines, purse seines, gillnets, and cast nets are all common forms of nets.
Trawls are towed nets that are drawn from a boat to gather fish and other marine creatures. Trawls are typically trailed over ocean bottoms, although they can also be employed in the middle of the water to catch specific species. Trawls are mostly employed in Canada to harvest groundfish (such as Atlantic cod, rockfish, and hake) and shrimp.
Dredges are iron frames that resemble shovels and are equipped with fine nets. They rake the seabed to harvest species such as scallops and clams that live at or attached to the seafloor.
Seine nets are bottom-weighted nets used to surround a school of fish in the water. The bottom of the net is then drawn in using a purse seine, capturing all the fish inside. By drawing the net behind a boat, a Danish seine directs fish into the net. Seine nets are used to catch roughly half of all commercial salmon in Canada, as well as herring.
Gillnets are a sort of net that is submerged in water and catches fish that attempt to swim through it but become caught (usually by their gills). The nets can be arranged in a line, a circle, drifting, or stationary configurations. Gillnets catch nearly a quarter of all commercial salmon in Canada, and they’re the most common way to catch whitefish in Manitoba.