Because the marine mammals sometimes raid fishing gear, harassing or killing them is banned, and rules now mandate specialized fishing methods for longliners to avoid snagging seabirds. Other protective measures are credited with aiding recovery of the once-threatened eastern Steller sea lion and helping to stop the decline of the mammal’s endangered western population. Research and training on bird-avoidance measures (notably led by Ed Melvin of Washington Sea grant) enabled managers to mandate techniques to ward off seabirds that dive on baited hooks. Curtailing longline bycatch throughout the Pacific is considered a key step to conserve the endangered short-tailed albatross (above), a species mistakenly declared “extinct” after WWII, after feather harvesting (for down) and volcanic eruptions had devastated its main nesting colony on Japan’s Torishima Island.
Faced with an urgent need to protect the endangered short-tailed albatross, managers mandated the use of “streamer lines” by North Pacific longline vessels that fish for halibut, sablefish, cod, and other groundfish. Longline crews reel out multiple baited hooks suspended on slender fishing line from a single long “groundline,” baiting the hooks just before they drop into the sea. Because seabirds sometimes dive on the bait, streamer lines are designed to flap in the wind near the hooks as they descend into the sea behind the vessels—harmlessly discouraging this habit. Research has shown that paired streamer lines can reduce bycatch by 88% to 100% in Alaska. These efforts, along with optional practices such as weighting longlines to sink faster, and natural trends such as changes in bird abundance have cut bycatch of all three species of albatross found in the North Pacific from over 2,000 birds in 1998 to less than 200 birds by 2002, maintaining low levels since then. The number of other birds inadvertently caught also declined.
Graph from: NOAA 2014 seabird bycatch estimates; 2014 data points added from Stephani Zador (NOAA) pers. comm. 2016NOAA Seabird Bycatch Estimates
These huge marine mammals haul out on remote beaches in northern Bristol Bay. When trawlers began fishing for sole near Round Island in the 1980s, researchers noted that more than half the animals quit the area. Fishery managers responded by banning groundfish trawling within 22 nm of the island. They later protected more haulout areas nearby, excluded other fishing methods, and restricted even vessels transiting near haulouts during the walrus’s peak season. In light of new research, USFWS later relaxed concerns about potential disturbance from fishing vessels beyond 3 nm from haulouts. The Council in 2015 therefore partially eased no-transit rules north of Round Island, helping vessels avoid another walrus haulout on Hagemeister Island. The new transit rules allow fishing vessels to access trampers in Togiak without having to go all the way around (saving about 10 hours of travel), while keeping a respectful distance from the big mammals.
Until the 1980s, hundreds of Steller sea lions were inadvertently caught or otherwise killed annually during trawl operations off Alaska. Protective measures have cut that toll by more than 98%. Compared to the annual average 971.5 animals killed during 1966-1988, observer data yield an estimate of just 14.2 incidental mortalities in 2013 for groundfish trawl fleets. In the past, sea lions often became entangled in fishing gear or suffered from conflicts with fishermen, in part because the big mammals (males can exceed 1,000 lbs) found plenty of prey in fishing gear. Regulations to protect the animals and institution of three-mile buffer zones to protect waters around rookeries began in 1990 with the listing of Steller sea lions as "threatened" under the Endangered Species Act. Today, biological observers onboard trawl vessels record mortalities or serious injuries to sea lions, enabling precise tracking of impacts.
After decades of worrisome decline, the endangered western population of Steller sea lions (map) is stabilizing in US waters, and even rising in the eastern Aleutian Islands and other areas. A 2015 NOAA aerial survey confirmed the trend, showing a modest but sustained growth of 1.94% annually in non-pup counts since 2000. Meanwhile the eastern population (see map) has fully recovered, and NOAA in 2013 removed it from the “threatened” list under the Endangered Species Act, after observing sustained growth of 4.18% annually, outperforming the 3% target.
Causes of decline and recovery are still debated. A nationwide ban on killing marine mammals that sometimes seize fish from commercial fishing gear began in 1990. Following litigation, North Pacific managers in 2000 imposed far-reaching fishing closures and restrictions intended to eliminate any plausible chance that trawlers or other fishing vessels may locally deplete feeding grounds of Steller sea lions in western waters off Alaska. In 2014, NOAA released a new Biological Opinion after two independent scientific reviews questioned much of the previous evidence of prey competition from fisheries and theories about the linkage between fishing and the decline. The 2014 Biological Opinion included new information from agency and external researchers on causes of sea lion mortality as well as tagging and other studies to evaluate how fishing affects sea lion prey. Following the new Biological Opinion, the Council adjusted protections, easing some measures that restrict fishing outside of 10 nm from sea lion rookeries and haulouts. In the western Aleutians the regional population decline may continue, so many restrictions on fishing for Atka mackerel and cod remain in place.