There is a lot of fishing equipment and methods used today to get fish for us to eat e.g. fishing from the rocks with fishing rods or big boats going out with nets. Today it’s a big thing to know what fish we eat and where it comes from. Lists have been established for most parts of the world to help us decide what fish to eat. These lists are not only based on the fish species that are low in numbers but also on the effect different fishing methods have on the marine environment. We will go through different fishing methods to give a better understanding on why certain types of fishing methods are unsustainable. By-catch is one of the main things that are considered when determining how sustainable a fishing method is. By-catch is the animals and plants that are captured with the target fish and thrown back into the ocean, it normally consist of marine mammals, birds, turtles, too small fish, corals and sea grass.
Fishing gear that has the least effect on the environment is rods. Pods and traps are good to use as they catch specific species, but the problem with them is that marine mammals can get entangled in the buoy lines, so they should not be used in areas that whales migrate in. Hook-and-line is also a good method to use, as it is short lines with hooks that are dragged behind a boat and since they are not left in the water for a long time they have a minimum by-catch.
Most other fishing methods have an effect on more than the target species. Long-lines are lines that can be kilometres long with thousands of baited hooks that catch everything. There are a few solutions on how to minimize the by-catch in long-lining, e.g. using circle hooks to prevent catching turtles and setting deeper lines to reduce catching sharks and marine mammals. A way to reduce catching sea birds are setting the lines quickly and at a greater depth, using bird scares, and setting them at night. The problem that arises by having long lines deeper, is that they can get caught on the bottom of the ocean and break off. That creates ‘ghost’ lines that keep on catching animals but no one take the catch.
Nets that can be used are pelagic gillnets, bottom gillnets and purse seines nets. Gillnets are left in the ocean in rows to catch fish swimming into them, purse seines nets are used by putting the net around a school of fish and then closing it like a purse. Gillnets are good when using the right size as smaller fish can then swim through it and stay in the population while the larger fish get trapped. These nets have a high by-catch of marine mammals, but pingers and other devises were invented to minimize this. The problem with the purse seines is that they are often used wrongly and set around floating debris where fish (big and small) hide and gives a large by-catch. When used properly on free-swimming species e.g. mackerel and tuna it is a good fishing method. A problem in the tuna fishery is the chance of catching dolphins. Since the tuna and dolphins migrate together they can get trapped and stressed even though the dolphins are released.
The last problem is all the different types of trawlers. This is large nets that are dragged behind boats catching everything in its way. Some trawlers are used in open oceans, other on the ocean floor. The bottom trawlers destroy everything in their way since the net acts as a vacuum cleaner that takes everything in its path away. The largest trawling net can fit 13 jumbo jets in it and they are up to 600m long. There is a lot of protest against the use of trawlers and their large by-catch as ±30% of their catch is by-catch. A large portion of this by-catch is turtles. Escape hatches for turtles have been created to take down the numbers, but only a few of them are used. Even if they are used on every trawler the main problem is that the trawlers destroy the bottom of the ocean when dragged along it.
There are different ways of minimizing the by-catch but to install and change the gear is something that takes time, so when buying fish to eat, look at how and where it has been caught, it’s our choice as the consumer to buy and eat fish that has been harvested in a sustainable way.