Wednesday, July 01, 2009

The Ecological Disaster That is Dolphin Safe Tuna

Is Dolphin Safe Tuna really better for the environment? Southern Fried Science makes the case that switching from following dolphins to using floating objects to catch tuna is actually worse overall for sea life.

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.
More information in the post about how the types of fishing actually work.

Unless you have a great love for dolphins over other types of sea life, following dolphin to catch tuna is the preferable way to go. Of course this also calls out the need for a replacement to floating object fishing. Maybe autonomous robotic submarines could find them? Or high powered satellites? Or GPS tagging? The other solution is to become a Sardinista and switch from eating tuna to smaller fish that can be caught with fewer bycatch.

This blog's whole dolphins are actually jerks section is great reading as well.

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