There’s no such thing as “the” ocean. It’s a mix of unique habitat. Fish don’t suspends uniformly throughout the water column.
They cluster within particular areas, they bury themselves into the sediment on the sea floor. Or they suspend beneath the surface. Commercial fishing operations has to account for this vertical diversity.
There’s no silver bullet for catching all fish. Your choice of net affect which zone of the water column you target. It also affects what species you’ll catch and whether or not you’ll spend hours pulling equipment aboard.
Matching the tool to the target species Choosing a net comes down to matching the nature of your targeted species with the appropriate gear. Is the fish fast and aggressive? Or is it slow and holds tight to bottom?
Does it tear up or are they more delicate? Are you dealing with a fish that will hold up well under rough handling, or not so much? The fishing industry have adapted specialized tools for all of those situations.
Knowing that explain why the fishing industry is what it is today. And it points out the balance between being sustainable and being efficient that guys has to strike every day. The major categories of commercial fishing nets are listed below in order from their relationship to the catch and the water.
Each is designed to solve a particular problem of catching fish for human consumption. Understanding them better show a more complete picture of the world’s food supply chain. A purse seine is a big circular net.
Major Types of Commercial Fishing Nets Explained
1. Purse Seine Nets
They’re these giant circular nets designed to corral schools of fish near the surface. This is what a purse seine looks like. The net drops into the water and hangs down vertically.
When the boat circles around the school, the folks on board pull a rope connected to the bottom of the net. That cinches the net shut like a draw string bag. So now you have a cylinder of netting surrounding the target, and the only way out of there is up (unless they want to hang out forever).
Really efficient way to catch fish that travel in tight balls (and are easy to see) like tuna, mackerel, sardines. On some of these trips, the catch is mind boggling. Often, they fill a whole ship in one haul.
But with great efficiency also comes huge concern about bycatch. If not carefully managed, sea turtles and marine mammals can becomes stuck against this wall of netting. Because this works so well, operators often use satellite or bird data to steers their boats toward where they think the fish are schooling.
2. Trawl Nets
Trawl nets use a simple concept. They are dragged through the water to scoop up whatever is in their path. Whatever they catch gets scooped into the net.
Trawls come in different forms but broadly speaking there are two type. There are bottom trawls. There are also midwater trawls.
Both function the same way. One or two vessel tow the net behind. As it goes it casts a wide mouth which filters the water.
Doors or otter boards holds the shape of the net open. Behind them, the mouth is pushed open. This type of fishing work well for bottom-dwelling species (species that live close to or on the sea floor).
Examples include cod, haddock, shrimp. It enables you to keep picking continuously. You don’t need to stop, set gear and go back and recover it.
Drawbacks includes the physical damage caused to the seabed. Seagrass beds and coral reefs can be disturbed by this form of fishing. This changes the environment for other marine life.
Bycatch levels tend to be higher too. The net doesn’t discriminate between different species passing through it.
3. Gill Nets
Stationary nets are curtain-like pieces of mesh called gill nets that hang in the water., How do they work?
A particular method of capture. Fish swim headfirst into the mesh and get caught. Head first.
Mesh catches on the gill cover of the fish. Fish cannot move and get stuck. It is important to note that the mesh size must be set to match the size of fish you want.
So it can help minimize bycatch vs. Trawl methods. It is not perfect, though. Bigger creatures like seals and dolphins can also gets tangled up in these.
They could of also potentially drown., Gill nets have to be placed just right. It depends on current and fish migration routes. They are left hanging in the water for a few hours or even an entire night.
It requires skillful positioning. It is quiet and doesn’t stir up the water. There is no sound or movement.
So this works well for shy fish.
4. Longlines
A longline is essentially a single line up to miles long with regularly spaced hooks hung below it that are baited. Technically speaking, it’s not a net at all.
But it acts as a passive form of fishing. Like the other items on this list, it has a main line that is attached to floats or anchored at both ends. It catches big predators.
Think tuna, halibut, swordfish. The advantage here again is less habitat damage and bycatch of non-target species. That’s relative to a seine or trawl though.
It does present a danger to birds, such as seabirds which dive down for the baits. To reduce this, operators has weighted hooks and lines called bird-scaring lines. The downside is increased labor because each hook must be individually baited and removed by hand.
5. Trap Nets and Pots
Some gear uses exclusion instead of entanglement: trap nets and pots. These work by using exclusion rather than entanglement, allowing entry but preventing exit. Funnels lead lobsters into lobster pots and crabs into crab traps.
They are made from twine or rope. Pointed ends guide the animals into the pot. The animal cannot find its way back out.
It is very selective. You can size the funnel opening to ensure only mature-sized individuals gets caught. Promotes sustainability; lets young animals escape/reproduce.
Gear typically sits on the bottom of the sea; recovered after some time. It is labor intensive. But it catches high-quality fish with little damage.
Meat stays fresh and undamaged. Gets better price in marketplace. There’s a reason each one made it into the industry.
Each fills a different ecological niche and exists within its own economic reality. Gear choices impact the whole chain. From the boat to the plate.
Knowing about them helps consumers better understand how complicated the source of our food can be. Next time you’re faced with seafood on a menu, ask yourself what tool was used to bring it to shore. It is more than just fishing…
It is the complex relationship between humans and ocean life.