Updated on June 6, 2016
Updated on June 6, 2016
Consumers often ask us to describe various types of fishing gear and explain which ones cause the most destruction to the ocean. Another frequent question is why our seafood ratings for a particular species differ depending on the fishing method used. To help answer these questions, we decided to create a Fishing Gear 101 blog series. In this series, we describe how common types of gear work, what they catch, how they affect ocean wildlife and habitats, what technologies or regulations can help lessen the gear’s negative effects, and what we see as the path forward to ensure healthy oceans in the future.
We want to help seafood consumers, businesses, and chefs who use our seafood ratings better understand what the terms ‘trawl’, ‘longline’, or ‘handline’ really mean. We also hope Fishing Gear 101 will help everyone understand the collateral damage that fishing can cause to the ocean and the importance of choosing seafood caught in a responsible way.
Next in this series are pots and traps. Pots and traps are three dimensional structures designed to trap or ensnare ocean animals that live on or near the ocean floor. In many cases, this gear has minimal effects on ocean wildlife and habitats. But there are still a few problems managers and fishermen need to work on solving.
FISHING GEAR 101
Pots and Traps – The Ensnarers
What is a pot/trap?
Pots and traps are three dimensional cage-like structures that capture animals that live on or near the bottom of the ocean floor. They are designed to lure animals into the device, and then once the animals are inside, make it difficult for them to escape. To lure the animals into the pot or trap, fishermen will bait them with small fish, fish parts, or artificial bait.
Fishermen set pots and traps on the bottom of the ocean floor, in both shallow and deep waters. Fishermen may set them individually or they may set several together that are connected by a common line. A rope connects the pots/traps to a buoy at the surface of the water. Fishermen will leave them in the ocean to fish for a few hours to a couple of days.
Some pots/traps are rectangular, some circular, and others cone-shaped. They are made of various materials, such as wood, steel, and wire1. Some pots/traps are small and lightweight while others are quite large and heavy. Take note of the different sizes and designs of the pots/traps in the images throughout the blog!
What does a pot/trap catch?
Fishermen often use pots and traps to catch crabs, lobsters, shrimps/prawns, and whelk. They will also use them to catch bottom-living fish that congregate around structures, such as Pacific cod, sablefish, black sea bass, and reef fish.
How do pots/traps affect the ocean?
Pot and trap fisheries catch varying amounts of bycatch – bycatch refers to the accidental catch of non-target animals. Bycatch in pot and trap fisheries often consists of other fish or invertebrate species that live in the same habitats as the target species. But because these animals are simply “trapped” rather than entangled, fishermen can typically release these non-target animals back to the ocean alive. Therefore, many pot and trap fisheries have low effects on other ocean species.
However, some pot and trap fisheries accidentally catch or entangle vulnerable ocean wildlife2.
Turtles are sometimes attracted to the bait, and get caught in the pots/traps or entangled in the fishing lines, and subsequently drown. For instance, the U.S. blue crab fishery catches depleted diamondback terrapins, and the Queensland, Australia blue swimmer crab fishery occasionally catches endangered green sea turtles. The lines that connect the pots/traps to the buoys or the lines that connect several pots/traps together can also pose a threat to marine mammals. The U.S. Northeast lobster and crab fisheries, for example, sometimes entangle and kill endangered North Atlantic right whales and humpback whales.
It’s also important to note that pot and trap fisheries can have an effect on the fish species they use for bait. Lobster fisheries, in particular, tend to use large amounts of fish for bait – more than the amount of lobster they catch! Fishermen often use small fish like herring, mackerel, and sardines to bait their pots/traps. These small fish – collectively called “forage fish” – play an important role in ocean ecosystems, serving as prey for many larger animals. So removing too many of them could not only harm their fish populations but entire ocean ecosystems.
Pots and traps cause low to moderate damage to bottom ocean habitats. Because they are relatively stationary, they are less damaging than bottom trawls or dredges. But they may bounce around in strong tides or storms. Additionally, if fishermen drag the pots/traps along the seafloor when hauling them in (instead of pulling them straight up), they may damage any sensitive bottom plants and animals, including sea grass, corals and sponges that are in their path1.
A final problem in pot and trap fisheries (and perhaps the biggest problem) is that this type of gear is very easy to lose at sea. In several pot and trap fisheries it is reported that fishermen may lose anywhere from 10-30% of their pots/traps each year. This means that across the global ocean, hundreds of thousands of pots/traps are lost each year3! This is a huge problem because lost pots/traps can continue to catch ocean animals – called “ghost fishing” – and bounce around on the seafloor.
What can be done to lessen the negative effects of this fishing gear?
There are several things that managers and fishermen can do to lessen pot and trap fisheries’ effects on the ocean. In many cases, making some simple modifications to the fishing gear design can make a big difference.
For instance equipping pots and traps with escape rings or vents can provide openings for undersized or non-target animals to escape (see image below).
Additionally, attaching bycatch reduction devices to the pot/trap entrances can prevent non-target species from entering the pot/trap to begin with. The idea of a bycatch reduction device is to exclude the catch of non-target animals, while still allowing for the capture of the target species. Scientists have shown that placing a simple bycatch reduction device over the entrances of blue crab pots can prevent most diamondback terrapins and non-target fish from entering, without reducing blue crab catches (see image below). Yet, currently only some U.S. blue crab fishermen are using these bycatch reduction devices. In Queensland, Australia, managers are encouraging crab fishermen to place a barrier, like a vertical cord, over the pot entrances to deter sea turtles from entering2.
To prevent entanglements of marine mammals in pot/trap gear, fishermen can add “weak links” to the lines that connect the pot/trap to the buoy. Weak links are designed to break under the force of a swimming whale. Another thing fishermen can do is make sure the lines that connect the pots/traps together sink, rather than float or arc up in the water2.
Further, modifications to the pot/trap design can help reduce “ghost fishing” if they are lost at sea. In many fisheries managers require fishermen to use biodegradable panels or mesh on their pots/traps. This way if the pot/trap is lost a sea, the panel or mesh will eventually dissolve and the pot/trap will no longer continue to effectively catch ocean animals. Research is ongoing to determine the most effective biodegradable designs3.
Other ways that fisheries managers try to lessen pot and trap fisheries’ effects on ocean wildlife and habitats include:
The Path Forward
In many cases, pot and trap fisheries have low effects on other ocean animals and habitats. In fact, you will find several “green” rated pot and trap fisheries in our online seafood guide – e.g. U.S. king crab, U.S. snow crab, Alaska shrimp, British Columbia spot shrimp, U.S. black sea bass, and Mexico spiny lobster. And pots/traps are an excellent alternative to bottom trawl gear when fishing for shrimp or octopus.
But there are still several things managers and fishermen need to improve upon:
With continued work, we can make more pot and trap fisheries ocean-friendly!
Elizabeth Brown-Hornstein is a Research Scientist at The Safina Center.