I don't have any specific statistics on the decline of dolphins owing to sea-bass fishing but this is a problem faced with all large-scale net fishing. The sea bass you should buy is line-caught. There are also new nets being tested with (I think) rigid square panel escape hatches through which dolphins can escape. In trials so far they don't actually escape through these panels, but are scared by the new nets and so stay away entirely. More research needs to be done along these lines. However, we should try not to eat too much of any one given species: farming can have negative effects on the ecosystem (parasites breed, the water becomes eutrophied and so on...) while overfishing has already stripped the Newfoundland cod banks and inshore North Sea waters of all cod (in practical terms). The MSC puts its logo to fish which is caught in the correct manner from sustainable stocks but they have recently been making some dodgy pronouncements about large-scale farms. Some are unhappy that the WWF has ceded much of their control over the organisation; John Gummer is now a senior board member. If you want to sleep easy, buy lesser-known line-caught species from day boats. If you're eating out, it's harder to know where the fish comes from. Bizarrely, Little Chef has some part of its menu cleared by the MSC and The Aquarium - a quite different, really rather good restaurant run by a couple of Swedes in St Katherine's Dock, London - has the fisheries content of its menu endorsed by the WWF. Anyway, I reckon you should eat gurnard instead: a few fiddly bones but sweet, firm flesh with no grey goo under the skin.
