Put yourself, for a moment, in the fins of a juvenile herring. You were born in the spring, after your mother\u2019s egg and your father\u2019s milt mingled on a strand of eelgrass in a British Columbia inlet, the bay colored a cloudy turquoise by the spawning multitudes. Your parents\u2019 school returned to its open-ocean feeding grounds soon after your conception, abandoning you to hatch and then loiter in the shallows, filter plankton, and dodge hungry cormorants. After two years of maturation, you\u2019re ready to venture out and join a school of your own\u2014but which one?<\/p>\n
On your way offshore, you bump into a congregation of fellow Clupea pallasii<\/em> and join the ranks, trailing your companions to the bay where your adopted school has bred for generations. You deposit your own eggs, then follow your school back to sea, memorizing the route from spawning bed to foraging area. The next spring, you repeat the migration, accompanied by a batch of fresh recruits who, this time, shadow you<\/em>. The cycle replays, again and again: you and other elders guiding, younger herring following. Your school is as faithful to its inlet as salmon are to their natal streams, except you\u2019re guided by intergenerational knowledge\u2014by social learning.<\/p>\n That is the powerful concept that underpins the adopted migrant hypothesis, the notion that some fish learn migration routes via follow-the-leader. Now a new study, inspired by Indigenous ecological knowledge, suggests that adopted migration may explain the structure of Pacific herring populations\u2014as well as their sluggish recovery from nearly a century of overfishing.<\/p>\n The motivation for the study, published this spring in the American Naturalist<\/em><\/a>,<\/em> came from a fisherman. Bill Gladstone, a member of the Heiltsuk First Nation, has plied British Columbia\u2019s central coast for decades, harvesting kelp upon which herring lay their eggs and selling the valuable roe clusters. That non-lethal harvest technique long stood in contrast to the method used by non-native commercial fishermen, who netted and cut the roe sacs from around 30,000 tonnes of BC herring annually<\/a> throughout the 1990s and early 2000s.<\/p>\n As the heftiest, most valuable herring vanished, Gladstone says, the spawning runs began to go haywire: fish vanished from bays where they\u2019d bred for centuries or popped up for a day in places they normally stayed a week. \u201cThe small herring became very erratic,\u201d Gladstone says. \u201cThey didn\u2019t know what the heck they were doing.\u201d<\/p>\n Gladstone passed along his observation to Anne Salomon, a marine ecologist at Simon Fraser University in Burnaby, British Columbia. \u201cHerring have lost their big chiefs,\u201d Gladstone told her, \u201cand no longer know where to spawn.\u201d The remark intrigued Salomon and Luke Rogers, a marine biologist at the University of Toronto. They began to wonder whether social learning through adopted migration\u2014first proposed in 1997 <\/a>to explain the behavior of Atlantic herring\u2014was operating on the central coast.<\/p>\n