Out in the open ocean, it’s another story. There is no protection here, and yet this is where most fish are now being caught. These may look like minnows, but they are tuna, each a healthy two kilos or more. Four different species are fished in the tropical Pacific. These are skipjack tuna, with some yellowfin tuna mixed in. But this boat is not setting nets. The ancient technique of fishing with rod and line is now practiced on an industrial scale. The water jets break up the outline of the boat from below, and mimic the noise and commotion of baitfish when under attack. Meanwhile, live baitfish are strewn around the boat to keep the tuna interested. It may look like a lot of effort for a few fish, but this pole and line technique of fishing can be surprisingly effective. Fishing for export is now big business in the tropical Pacific, with tuna alone accounting for 30 times more fish than all the fish caught by subsistence fishermen. So is commercial fishing sustainable? Skipjack are the smallest, and by far the most abundant tuna species in the Pacific. They reach maturity in just a year and then spawn many times within a season. They seem to be the perfect catch, as their numbers just keep bouncing back. But not all marine life is so resilient. Thanks to modern fishing, some of the best-known animals of the Pacific are in deep trouble. Sharks have been top dog in the Pacific for millions of years. They control the numbers of other fish, and so play a vital role in keeping the underwater ecosystem healthy and diverse.