May 10, 2023 — Every year, 22 million sockeye salmon begin life some 420 kilometers, or about 260 miles, inland from the Alaskan coast, in plastic bins. They’re at the Gulkana hatchery, the largest sockeye salmon hatchery in the world — but just one of countless hatcheries around the globe that release native fish into rivers, lakes and oceans to augment wild stocks.

Fish hatcheries, like the species they breed, come in many shapes and sizes. Some, like the Gulkana facility in the U.S., pump out millions of fish each year to support commercial fisheries. Others, like the Nechako White Sturgeon Conservation Centre hatchery in Canada, focus on conservation by rebuilding and maintaining genetic diversity in threatened populations. Some hatcheries use eggs and milt (sperm) from wild fish; others use hatchery fish as parents. But no matter what the species of fish or the purpose of the hatchery program, the released fish enter the ecosystem en masse and interact with an existing community.

Pacific salmon are economically and culturally important species for nations across the northern Pacific Ocean, and hatchery programs positioned to boost commercial fisheries have increased dramatically over the last 150 years. Since the early 1990s, approximately 5 billion hatchery salmon have been released every year, primarily by the United States, Japan and Russia. Chum (Oncorhynchus keta) and pink (Oncorhynchus gorbuscha) salmon are by far the most common hatchery salmon species, but others are also bred and released from hatcheries. For example, in Japan, masu salmon (Oncorhynchus masou masou) are a highly sought-after fish, and hatchery managers release approximately 10 million hatchery-bred fry — a juvenile life stage of salmon — into freshwater each year. Typically, the released masu fry stay in streams for at least a year before the majority migrate to sea (as smolts), returning a year later to freshwater streams to spawn (as adults).

Read the full article at Mongabay