The ecological disaster that is dolphin safe tuna
This is a rare cross post between my regular Monday “Ethical Debate” a soon-to-be-regular series entitled “Dolphins are actually jerks”, and a soon-to-be-regular series entitled “Hippie Hypocrisy: People who try (but fail) to help”.
Most environmental activists (indeed, most people) have heard the phrase “dolphin safe tuna”, but few know the details other than that it is tuna captured in a way that is better for dolphins.
Before we get into the ethical debate itself, here’s some background on the tuna fishery, and on what “Dolphin safe” actually means.
Tuna is one of the world’s most economically important fisheries, directly employing tens of thousands and feeding millions. The main way that tuna is caught is through purse seines in the Eastern Tropical Pacific. Basically, after a large group of tuna is located, a miles-across purse seine net is closed around them via a group of small boats associated with a large factory ship. It’s an effective way to catch large amounts of fish for not a lot of money.
This technique is pretty standard- the main variation lies in how the large group of tuna is located. There are basically three ways to do this.
1) Get lucky and happen to stumble across a large group of tuna visible from the surface in the middle of an enormous ocean. Obviously, this isn’t terribly practical.
2) Attract tuna using floating objects. Stay tuned, we’ll come back to #2.
3) Follow dolphins, because dolphins in the Eastern Tropical Pacific are often associated with large schools of tuna. Dolphins are easy to follow because, unlike tuna, they have to come up for air.
For a long time, #3 was the most common way of catching tuna. The problem with this method was that by definition, dolphins are right there- and they get caught in the net as well. Despite the honest effort of many sailors to free dolphins (there is a long maritime tradition of respecting dolphins), by some estimates, around 500,000 dolphins a year were killed as a result of bycatch.
As a result of pressure from environmental activist groups like Greenpeace, it became illegal to fish using method #3, and we now have what is called “dolphin safe tuna”. Technically this means only that the tuna isn’t harvested by searching for dolphins associated with a school of tuna, something that many environmental groups think isn’t a strong enough definition.
Recall that method #1 isn’t feasible. Tuna fishing fleets rapidly switched over to method #2, attracting tuna using floating objects.
It is poorly understood why fish in the open ocean flock in such huge numbers to floating objects, but is a near universal phenomenon. If you put a log in the middle of the ocean, within hours it will be surrounded by fish. It may have something to do with the fact that many open ocean fish can go their entire lives without encountering a hard surface.
The floating objects now used by tuna fishing fleets are quite high tech- they have sonar and video cameras that allow the flagship to detect how many fish are near that object. Once there are enough, the purse seine comes and scoops them all up- and the floating object is redeployed.
The big problem with this method is that floating objects don’t only attract tuna. EVERYTHING is attracted to floating objects, including sea turtles, sharks, seabirds, billfish, and, yes, dolphins!
Let’s compare the bycatch rates of floating object associated tuna and dolphin associated tuna.
“Ten thousand sets of purse seine nets around immature tuna swimming under logs and other debris will cause the deaths of 25 dolphins; 130 million small tunas; 513,870 mahi mahi; 139,580 sharks; 118,660 wahoo; 30,050 rainbow runners; 12,680 other small fish; 6540 billfish; 2980 yellowtail; 200 other large fish; 1020 sea turtles; and 50 triggerfish.”
“Ten thousand sets of purse seine nets around mature yellowfin swimming in association with dolphins, will cause the deaths of 4000 dolphins (0.04 percent of a population that replenishes itself at the rate of two to six percent per year); 70,000 small tunas; 100 mahi mahi; 3 other small fish; 520 billfish; 30 other large fish; and 100 sea turtles. No sharks, no wahoo, no rainbow runners, no yellowtail, and no triggerfish and dramatic reductions in all other species but dolphins.”
In other words… the only species that “dolphin safe” tuna is good for is dolphins! The bycatch rate for EVERY OTHER species is lower when fishing dolphin-associated tuna vs. floating object associated tuna! The reason for this is obvious- floating objects attract everything nearby, while dolphins following tuna doesn’t attract any other species.
If you work out the math on this (and you don’t have to, because the environmental justice foundation did) , you find that 1 dolphin saved costs 382 mahi-mahi, 188 wahoo, 82 yellowtail and other large fish, 27 sharks, and almost 1,200 small fish.
By trying to help dolphins, groups like Greenpeace caused one of the worst marine ecological disasters of all time. Few other fisheries are as bad for groups like sharks and sea turtles as the purse seine fishery, and none are as large in scale.
Here we get into the ethical debate.
Is it worth saving dolphins, who were not and are not endangered, at the expense of sea turtles, sharks, and many other fish species who are endangered?
To make this debate more interesting, I am taking the options of “just stop fishing for tuna” and “come up with another way” off the table- it’s simply not going to happen in reality, anyway.
Should we fish for tuna using dolphin associated schools and save sharks, sea turtles, and dozens of species of fish… or should we fish for tuna using “dolphin safe” floating object associated schools and wipe out the populations of many species of sharks (some populations have shown a 75% decline since “dolphin safe” tuna came onto the scene? In other words, what is more valuable- 1 dolphin, or so much else?
Personally, I think this is a classic example of the false value our society places on marine mammals, something that Andrew has already written about quite a bit. I think to wipe out the populations of so many other species in order to save a few individual dolphins (recall, dolphin populations aren’t threatened by dolphin-associated fishing, though lots die) is ludicrous.
I think we should go back to fishing dolphin-associated sets AS SOON AS POSSIBLE and hope that the damage done to shark, seabird, sea turtle, and large fish populations by the dolphin-safe disaster is fixable.
As a side note, our 43rd President, George W Bush, attempted to help on this issue by changing what dolphin safe means… but environmental groups stopped him. Go team.
As another side note, fisherman I’ve spoken to and read interviews with are horrified by the bycatch that floating object fishing causes and would like to return to the old ways, if only we will legally allow them to do so.
UPDATE: (added June 29, 2009). This post is starting to get a lot of attention, and some people are missing the point. There are a few things I would like to address because I don’t want to say this fifty times in the comments.
1) The comparison of 70 thousand to 130 million SMALL tuna is listing small tuna as bycatch. They are trying to catch BIG tuna. Catching small tuna is bad- they are less meat per fish (therefore more work), and it’s less sustainable because you’re killing the fish before they reproduce.
2) I’m restricting debate to the two methods of seining NOT because I believe those are the only two options, but because this post is PART OF A SERIES called “Ethical Debates” and I always restrict the debate because it makes the discussion more interesting. Please stop saying I’m arrogant, ignorant, stupid, or things of this nature because I restricted the debate to two unpleasant choices. I did that because it makes the discussion more interesting and for no other reason.
3) What can you do? Either don’t eat tuna or eat “Marine Stewardship Council” approved sustainable tuna, which is caught by rod and reel and has no bycatch. However, it is much more expensive, and is hard to find.
Update: Thanks to everyone who helped vote for this post in the 2009 3 Quarks Daily science blogging prize!