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Lack Of Vitamin B Threatens Steelheads

Steelhead or Rainbow Trout

Steelhead – a strain of rainbow trout - are showing stress in Lake Ontario and its tributaries. For the first time in New York, some steelhead are dying from an apparent vitamin B deficiency.

The DEC’s Salmon River Fish Hatchery is helping research this disorder, also known as EMS or Early Mortality Syndrome.

Steve LePan runs the Great Lakes Fisheries office in Cape Vincent. He told WXXI that this fall, anglers were reporting rainbow trout that seemed to be in distress. They were struggling to swim. For the first time, the steelhead were spotted on river bottoms, dead. But why?

Tests for usually troublesome viruses, bacteria and parasites were negative. However, a lack of Vitamin B or Thiamine, showed in the dead fish.

LaPan reminds us that steelhead and other predator fish feed on alewives, an invasive species bait fish. Alewives can suffer a Vitamin B deficiency. "They also can produce an enzyme in their gut, called Thiaminase, which actually breaks down vitamin B, so it's a bit of a double-edged sword. You get less vitamin B when you feed on these fish, and then you also get this enzyme that breaks down the vitamin B that you do have."

LaPan says for years, the DEC has given vitamin B to newborns at its Salmon River hatchery. And, imagine this, they give shots of vitamin B to some adult fish which make it up river to the hatchery. "People from our fish pathology lab are injecting adult fish, and then they'll hold those fish outdoors in raceways and feed them a commercial diet, that, as I mentioned before, has vitamin B in it."

The goal is to produce more healthy fish and healthy eggs when it's time for the DEC to harvest them in the spring.

Steelhead fishing
Credit NYS DEC

LaPan says the DEC saw some signs that alewives were stressed this year, following last year’s cold, hard winter. That's not unusual and he suspects alewives produce more of that vitamin B reducing enzyme Thiaminase when stressed. "Or it could be related to the feed that alewife are consuming. If there was some kind of a shift in the lower food web, namely, the different type algae in the water that's consumed by the small organisms that alewife feed on."

LaPan admits he’s not sure the DEC will be able to pinpoint a cause for the vitamin B deficiency.

Why worry about a little vitamin B? Money. Steelhead are an important component of Lake Ontario's sport fishery, which a Cornell University study valued at over $112 million in New York annually.

It’s not just rainbow trout. Steve LaPan says most anglers want Chinook salmon to be the prevalent predator in Lake Ontario. "You've got Chinook, Coho Salmon and steelhead, brown trout and lake trout, so in any given year, if there is a drop in any particular species, there are four other species out there."

Chinook also feed on alewives, so what happens to the alewives matters. "Chinooks really do best in the Great Lakes when you have a health population of alewife. The other side of that coin is, when you have too many alewife around, they can have negative impacts on native species."

That's the DEC's dilemma: trying to rehabilitate native species while supporting lucrative trout and salmon fishing. But diversity is one of the great things about fishing Lake Ontario. "Sport fishery, for the past twelve years has been near record breaking levels, in terms of angler success, so anglers on Lake Ontario have been enjoying the best trout and salmon fisheries since the inception of the stocking."

Something’s working. "We're hopeful that whatever happened in Lake Ontario this year that caused this event in the first place, that it doesn't happen again."

The DEC promises to watch and react if problems come up this year.