A report issued by the National Resources Defense Council finds that more than 650,000 marine mammals -- dolphins, whales, manatees, seals and more -- are either killed or "seriously injured" by foreign fishing tactics. These tactics include the unregulated use of large-scale tools like gill nets and mesh that trap wildlife indiscriminately. Marine mammals may not be actively fished, but they frequently get caught in fishing gear.
The U.S.'s Marine Mammal Protection Act provides comparatively strict protection for marine mammals during fishing expeditions, on top of existing state law; for example, gill nets are banned by many top U.S. fishing states, including Florida, but are legal in countries like Sri Lanka. ("Large catches of Long-snouted Spinner Dolphins in gillnets and by harpooning in Sri Lanka and the Philippines have occurred for the past 20 years," says Australia's Department of the Environment.) Our domestic protections don't matter much when, according to the NRDC, 91 percent of the U.S.'s seafood is foreign caught and not subject to those laws:
Nearly every foreign fish product sold in the U.S. violates a federal marine mammal protection law. The wild-caught seafood most enjoyed by Americans – shrimp, tuna, crab, lobster, and salmon – present a particularly significant risk to marine mammals due to the dangerous fishing practices associated with them abroad.
The U.S. government doesn't impose its own laws on fish imports, which allows foreign fisheries to operate without regard for marine mammals. Several petitions are circulating (here, here, and here) in an effort to call on administrators to enforce already established seafood import laws and to protect the lives of marine mammals.