Lake Superior cisco population may be rebounding
Minnesota DNR finds nearly three times more little "herring" than any recent year.
DULUTH — The Minnesota Department of Natural Resources Lake Superior fisheries team got some good news when they were out trawling on the big lake in October: The number of small cisco — commonly called herring by folks along the North Shore — were way up.
“It was a very welcome sight for us. We haven’t had even a decent year class since 2014-15,” said Cory Goldsworthy, the DNR’s Lake Superior fisheries manager. “And you have to go back to the 80s to have a really great year for them.”
The DNR crew landed 115 of the small, young cisco this year where none had been netted in any of the past four assessments. Just two were netted in 2016 and 43 in 2015, which coincides with that last decent year class for cisco.
Goldsworthy said he hopes spring test netting by the U.S. Geological Survey will echo the same results. That survey hasn’t found many young cisco since 2003 and hasn’t seen a bumper crop for more than 30 years.
The big crop of little cisco may signal good news not just for the commercial netters who harvest them to sell, but also for the lake’s entire ecosystem and for sport anglers. This year’s little fish should be big enough to harvest in about four years. Cisco also can be a major food source for native lake trout and introduced salmon species and, when they reach full size of about 16 inches, can even become a target species for ice anglers on the big lake.
Cisco have been in decline for several decades on the big lake, with poor reproduction and dwindling numbers in general. The fish can live for decades, if they aren’t gobbled up by bigger fish, and some of the adult cisco now being caught are still from phenomenal reproduction years in the 1980s.
Scientists looking back found that years with large swaths of Lake Superior covered in ice were the best years for cisco reproduction. But, as the lake’s water temperatures have warmed in recent decades, there have been far fewer years with major ice cover. And there have been far fewer good years for cisco.
“Ice cover makes a difference for cisco. The more ice, the better the year class,” Goldsworthy noted.
It’s less clear what impact invasive species like rainbow smelt and spiny water fleas may have on the cisco population.
There are 25 state-licensed commercial cisco netters along the North Shore who harvest the fish both for food (they are tasty table fare and taste nothing like pickled ocean herring) and, in November as they spawn, for their eggs. The cisco roe, or caviar, is sold overseas at a premium price.
DNR crews were out on Lake Superior in October at night when the cisco come up to hang out closer to the surface. Fisheries crews use electronic acoustic (scientific-grade fish-finders) readings but also drag a big net at least once to verify what the electronics tell them.
The DNR does the work from the deck of the Blue Heron, the University of Minnesota Duluth’s Large Lakes Observatory research boat.