auling in a 50-pound halibut might be a once-in-a-lifetime triumph for an angler. For a commercial halibut vessel, it’s the start of a good fishing day. For trawlers targeting other groundfish, like Pacific cod, catching a halibut is a hassle. The trawler might not have permission to keep a halibut, and its hold has only so much room for saleable species. Easier to discard the halibut overboard, even if the accidental encounter proves fatal. The bycatch removes the fish from the ecosystem without any economic reward for the crew. What a waste.

Sustainably managed fisheries have strong incentives to minimize bycatch, at the cost of some inconvenience to hard-working crews. Regulations, specialized gear, monitoring technology, and in-person observers are some of the tools at the disposal of NOAA Fisheries. The agency keeps detailed reports from every active vessel about the amount of bycatch to the nearest gram, or less than the weight of a single halibut’s weird eyeball.

Now, halibut are relatively safe, with bycatch at historically low levels. As Vanessa Orr’s article “Snagged by Accident” reports, other fisheries are suffering, particularly Western Alaska salmon, and even if bycatch is not the most important factor in the decline, it is the most controllable.

This edition of Alaska Trends dips into the overwhelming abundance of data to fish out a few facts.