Vitamin B1 gains in wild lake trout embryos challenge assumptions drawn from hatcheries

For decades, fisheries managers have struggled to restore recruitment in wild lake trout populations across the Great Lakes region, with limited success. Returning this species to its former abundance is hampered by overfishing, sea lamprey predation, invasive species and habitat alterations.

A potential barrier to recovery is thiamine deficiency complex (TDC), a disorder caused by insufficient vitamin B1, or thiamine. This syndrome is widely considered a major threat to conservation and restoration efforts.

TDC can cause severe behavioral and neurological abnormalities and extremely high mortality among newly hatched fish. It is typically observed in hatcheries that rear salmon and trout from eggs obtained from wild populations, and hatchery staff can mitigate its effects using thiamine treatments.

Wild embryos gain thiamine

Now, scientists from SUNY Brockport, the University of Vermont (UVM) and Oregon State University have conducted the first study to examine whether embryos can acquire thiamine naturally in the wild. The study, published in Scientific Reports , found that lake trout embryos developing in Lake Champlain accumulated substantial amounts of thiamine, while paired embryos reared under controlled laboratory conditions did not show the same increase.

The findings provide new insight into how the effects of thiamine deficiency may play out differently in the wild than in hatcheries.

Until now, all research on TDC-related mortality has taken place in hatcheries, leaving uncertainty about how the disorder functions in natural ecosystems. Thiamine must be acquired from the diet or environment—and is potentially highly available in water, where lake trout eggs incubate for over five months before hatching.

“Prior to this study, practically everything we knew about the effects of TDC on newly hatched fish was based on studies in labs and hatcheries,” says Matthew Futia, the study’s lead author. “Our findings suggest that what occurs in natural environments may actually be quite different, and thankfully, in a good way for the fish.”

Lake and laboratory results diverge

Lake Champlain was selected as an experimental system because TDC has been documented in stocked populations of lake trout and Atlantic salmon, and spawning sites are well studied. In fieldwork led by UVM’s Rubenstein Ecosystem Science Laboratory and the Rinchard Lab at SUNY Brockport, fertilized eggs from Lake Champlain were split between natural incubation and controlled laboratory rearing. The team measured thiamine levels at four developmental stages and analyzed the lake water to learn how much thiamine is available in the surrounding environment.

The researchers found that lake-reared embryos experienced significant increases in thiamine concentrations at the time of hatching and in the following weeks, compared with the lab-reared embryos, which showed no increase at all.

The team also detected thiamine precursors and byproducts in Lake Champlain. Together, these findings indicate that developing embryos may be able to take up enough thiamine during development to offset problems due to thiamine deficiency.

By revealing a previously unknown pathway for thiamine acquisition in the wild, this study opens the door to improved restoration strategies, more accurate assessment of TDC and better-informed management decisions for lake trout and other salmonines across the Great Lakes and beyond.

Who’s behind this story?

Robert Egan

Bachelor’s in mathematical biology, Master’s in creative writing. Well-traveled with unique perspectives on science and language.

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