This is one of the food industry topics that I have been asked to write about on the blog. Tuna is a popular fish choice for many people due to its cost and relatively mild flavor. Because of this, I thought that it was a great suggestion and I want to cover it in detail, like I did with shrimp a few weeks ago.
Note: When you Google search “Is eating tuna bad for the environment?”, all of the suggested searches are about how much tuna can be consumed per week due to the accumulation of heavy metals (such as mercury) in its tissues. This post will not deal with health ramifications of eating tuna, although it is a valid concern. Instead, I would like to talk about the environmental issues associated with tuna fishing.
Types of Tuna & Their Conservation Statuses
There are five main species of tuna that are commercially fished and sold for human consumption, and each one has a unique geographic range, fishing methods and conservation status (source, source).
Skipjack
A temperate and tropical-dwelling fish usually sold canned in grocery stores. The population is currently stable and classified as “of least concern.” However, skipjack are usually caught using purse-seine nets in combination with fish aggregation devices (FADs). FADs are floating fish “lures” that attract not only the target fish, but also many other species that get caught up in the fishing net with the target fish (source). FADs greatly increase the amount of bycatch per net. Obviously, this is not an environmentally-friendly fishing tool–steer clear of fish that is caught using FADs. Better yet, look for pole-and-line caught fish, which has an even lower incidence of bycatch and bycatch mortality (source).
You can easily find eco-friendly fished skipjack using the Monterey Bay Aquarium’s Seafood Watch site (or download the app, which is linked on the home page).
Yellowfin or “Ahi”
A tropical fish sold canned and fresh, and often used in sashimi. They are “near threatened” as populations are declining worldwide due to overfishing. They are usually fished using the same methods as skipjack. Due to their conservation status, it is probably best to stay away from yellowfin tuna. Only eat sustainably-fished yellowfin (pole-and-line caught, or at least fished without FADs) if you must.
Albacore
Albacore tuna inhabit a wide range of temperate and tropical waters and are usually sold canned. They are also “near threatened” due to overfishing. They are usually caught on longlines, in which several smaller fishing lines with (often live) bait on the end are attached at intervals to one long fishing line. Longline fishing results in significant amounts of bycatch. It is widely considered to be inhumane, as fish and other animals that are caught are left to die over a period of several hours or even days (source).
Again, it is probably best to avoid eating albacore tuna to due its conservation status. If you must eat it, look for pole-and-line caught fish.
Bigeye, also known as “Ahi”
Bigeye tuna live in subtropical and tropical waters and are sold fresh or frozen. Their populations are “vulnerable”: less than 20% of the population remains (source). The fishing method is irrelevant here. Eating bigeye in any form, fished in any manner is bad for the environment.
Bluefin
Bluefin tuna live all over the world. There are three subspecies: Atlantic, Southern, and Pacific. Atlantic Bluefin tuna are endangered. Southern Bluefin tuna, which migrate between the Indian Ocean and western Australia, are listed as critically endangered by the International Union for Conservation of Nature (IUCN). Pacific Bluefin tuna are estimated to be at less than 3% of their population. However, the US government refuses to put protections in place to prevent them from going extinct, most likely because they are so lucrative (source). Definitely avoid Bluefin tuna.
Overall: If you like tuna, buy sustainably-caught skipjack. Limit sustainably-caught yellowfin and albacore consumption. Avoid bigeye and bluefin entirely.
Environmental Impact of Tuna Decline
So maybe you like tuna, but you wouldn’t really mind if they went extinct and you couldn’t get it anymore. There would still be salmon, shrimp, crab, and all of that other tasty seafood, after all. Why should you care?
Here’s the thing, said Claire, putting on her glasses and pulling out her college ecology notes. Because tuna are predators near the top of the ocean food chain, the decline of tuna populations doesn’t just mean less tuna for us.
Removing top predators from ecosystems results in a population explosion of prey species. Without that control, prey species generally become unhealthier (predators take down the sick and the weak, to the overall betterment of prey populations) and overgraze their environments. In some cases, prey can permanently destroy the resources that they depend on to survive.
Thus, if tuna go extinct, it’s not only possible but likely that populations of other species down their food chain swell and burst. All the way down to the plankton that many, many ocean creatures depend on for survival.
When marine scientists express concern that the “collapse of the oceans” is at hand, they’re not simply trying to be dramatic to get the public’s attention. They’re voicing a real fear that our love of seafood–and ignorance of where it comes from–will permanently destroy one of the world’s greatest resources.
I want to hear your thoughts! Are you a seafood fan? Did I miss anything in this article? And is there another topic about the food industry that you’d like to see covered?