In its essence, something that is sustainable can be continued. A sustainably caught fish is one that is caught in a way that can be continued indefinitely.
There are a number of factors influencing the ultimate sustainability of seafood. The way I think about it, they are:
first, species caught;
second, the practice used;
third, location; and
fourth, the number of handlers between you and the fishermen.
Let’s go through these factors in order.
First: species caught.
The species of seafood affects sustainability in a profound way. Some fish mature and reproduce both quickly and in great numbers. These species can rebuild populations quickly. Others take years to mature and reproduce in smaller numbers. These take a long time to rebuild their populations.
Eating lower on the food chain is often a better choice, since these species are more abundant and can often rebuild faster.
Knowing the species of the fish you’re eating is imperative. Ideally, knowing the scientific name would be a given, since there can be multiple fish by one name. For example, Atlantic Bluefin Tuna (thunnus thynnus), Pacific Bluefin Tuna (thunnus orientalis), and Southern Bluefin Tuna (thunnus maccoyii) all share the “bluefin tuna” name, but have slightly different population statuses.
Once you know the scientific name, do a little research before eating–check the conservation status, maturation, and reproduction. If you can, make sure the fish you’re eating has had a chance to reproduce, especially if it’s a species that rebuilds more slowly.
Second: practice used.
Fishing practices are a huge part of sustainability, and also one of the more obscure. Knowing the exact practice used to catch the fish you’re eating is very important. The same fish could have been caught using a pole-and-line, which has very little impact on the ecosystem outside of the direct result of removing that particular fish, or a dolphin-set purse seine, which kills hundreds of dolphins every year, or even a gillnet, which are so notorious for their bycatch that they are called “walls of death.”
A few of the more problematic fishing practices include trawling, gill or drift nets, longlines, purse seines, pots, traps, and dredges.
- Trawls are cone-shaped nets pulled along the seafloor or through the water column. Bottom trawls–those used on the seafloor–are used to catch animals that live on or near the seafloor, including fish, squid, and shrimp. Midwater trawls–those used in the water column–are used to catch schooling fish like sardines and herring. Those dragged on the sea floor can cause damage to its ecosystems and habitat, and both kinds have high rates of bycatch, or catching fish they didn’t intend to catch, like sharks, endangered sea turtles, and fish.
- Gillnets, also known as drift nets, are large walls of netting, suspended in the water column or weighted to the bottom, which snare fish by their gills. Bottom gillnets catch fish like cod, halibut, and bass. Drift or midwater gillnets catch fish like sharks, swordfish, and salmon. Both kinds have a high rate of bycatch. Species affected can include turtles, marine mammals, sharks, and other endangered species.
- Longlines are long fishing lines with smaller lines attached. These smaller lines end in baited hooks. They can be suspended in the water column or weighted to the bottom. Pelagic longlines catch fish like tuna and swordfish. Bottom longlines catch fish like halibut, grouper, and bass. Many longlines also have a high rate of bycatch which can include seabirds, and many top predators, which affects marine ecosystems. If they snag on bottom organisms like corals and plants, they can also damage those habitats.
- Purse Seines are large nets which encircle schools of fish like tuna, trapping them inside. There are three types of purse seines: free school which set the nets on a free school, dolphin set in which fisherment locate tuna by searching for a pod of dolphins, and associated, in which fishermen locate a school of tuna by searching for natural debris around which fish gather, or by setting out a fish aggregating device (FAD), in order to attract fish. Dolphin set and associated purse seining are particularly problematic. Dolphin set purse seines encircle pods of dolphins in the process of fishing, and can kill dolphins. Associated purse seines have higher rates of bycatch than free school purse seines, and FADs may disrupt behavior of fish species in the ocean.
- Dredges dig into the sea floor using teeth or jets of water. They catch mainly shellfish like clams and oysters. They can cause habitat damage by uprooting or destroying bottom features and species like seagress, crabs, and snails. They leave scars in the ocean floor, sometimes for months. Dredges also have high rates of bycatch, which can include flounder, skates, and sea turtles.
- Pots and traps are similar to cages in many shapes, left on the ocean floor with a line connected to a buoy at the surface. They are used to catch animals including crabs, lobsters, and some fish. Pots and traps can negatively impact marine ecosystems by damaging the sea floor, accidentally catching or entangling non-target species such as cetaceans or turtles, or being lost and so continuing to catch or entangle ocean animals. This is called ghost fishing.
And even within a practice–purse seining, for example–there can be a range of variation as to the exact impacts it has. An open-set purse seine has a minimal impact on the ecosystem, and can be a sustainable choice. Associated purse seining, using fish aggregation devices (FADs), and dolphin-set purse seining, are often both problematic.
Even a usually problematic practice, like longlining, can be made more sustainable through the use of modifications like streamers, to warn off seabirds, circle hooks, to reduce bycatch of marine mammals and non-target fish, or even using whole fish as bait rather than squid to reduce bycatch of sea turtles, since turtles have a tendency to eat a whole fish off the hook in small bites, whereas they will eat the whole piece of squid–with the hook–at once.,
Take time to familiarize yourself with fishing practices used to catch the fish you’d like to eat. Find out which were used to catch the fish you’re eating, and which modifications were used to lessen negative effects, like bycatch or damage to the sea floor.
Where a creature was caught will also affect the sustainability of your meal. A species that’s doing well in one area could be nearly gone in another, and the regulations can vary. For example, while dolphin-set purse seines aren’t used by US fishermen, this method is used in other areas of the Pacific.
Knowing where the fish you’re eating came from is important to know the sustainability of your food.
Fourth: number of handlers between you and the fishermen.
An unfortunate aspect of eating seafood is that the information one needs to determine the sustainability of a meal can be lost in the transactions between the fishermen and your table. There can be miscommunications, mistranslations, and sometimes even straight up misinformation.
The ideal place to buy seafood is from the fishermen themselves. They are the best informed to answer any questions you have about how the fish was caught, what species it is, or anything else you have concerns about. Plus, fishermen earn more for their catch when it is sold with fewer middlemen.
Another thing to be aware of is hidden seafood–that is, products made from seafood that one wouldn’t necessarily think of as being seafood, like fish oil supplements or salad dressings.
In conclusion, there is no list or magic formula to find out whether a fish was caught sustainably. Every fish is different, and “sustainable” is just a label. The only way to really know is to determine it for yourself, from the information you have. If you’re not certain that the fish you’re eating was sustainably procured, eat something else. In the United States, we don’t need fish as a protein source, and are able to make another choice. In other areas of the world, this isn’t the case–they need to be able to eat these fish, and we need to leave the fish so that they can.
Our generation depends on healthy oceanic ecosystems, and that means that we need everyone to make responsible seafood choices in order to maintain or rebuild healthy fish populations. Get informed about the fish you’re eating and do your research before buying it–or don’t buy it at all.
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