Science1 publisherNot yet confirmed elsewhere2 min readPublished
Lake trout embryos build up thiamine while incubating in Lake Champlain
Scientists at SUNY Brockport, UVM and Oregon State found lake trout embryos in Lake Champlain gained thiamine by hatching while paired lab embryos gained none. The study measured vitamin levels, not survival, so it has not yet tested whether wild hatchlings escape the deficiency seen in hatcheries.
The Scientist · Science desk
What happened
- Fertilized eggs from Lake Champlain were split between incubation in the lake and controlled lab rearing, and thiamine was measured at four developmental stages.
- Water analysis detected thiamine precursors and byproducts in Lake Champlain, a possible supply for the embryos incubating there.
- The work, published in Scientific Reports, is the first study to test whether fish embryos can acquire thiamine naturally in the wild.
- Lake Champlain was chosen because the deficiency is documented in its stocked lake trout and Atlantic salmon and its spawning sites are well studied.
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Why it matters
- constraint Because only thiamine levels were tracked, the study cannot show that lake-incubated hatchlings avoid the abnormalities and deaths that define the disorder in hatcheries.
- decision Planners ranking threats to lake trout recovery now have to decide how far hatchery-derived TDC risk applies to eggs spawned and incubated in the wild.
- capability If the uptake holds in other lakes, TDC assessment could account for thiamine an embryo gains during incubation as well as the supply the egg starts with.
The comparison is clean because both groups came from one pool of eggs [6]. Any later gap in thiamine is therefore hard to blame on what the mothers put into the yolk. What differed was the surroundings, over an incubation that runs more than five months before hatching [9]. Thiamine has to come from the diet or the environment, and the water around an egg may be a rich supply [9].
The difference showed up late. Lake embryos had significant increases at hatching and in the weeks after. The lab embryos showed no increase at all [5]. That puts the gain in the same window where thiamine deficiency complex (TDC) causes harm. The disorder brings severe neurological and behavioral abnormalities, and extremely high mortality, in newly hatched fish [8].
"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," said Matthew Futia, the study's lead author [3]. "Our findings suggest that what occurs in natural environments may actually be quite different, and thankfully, in a good way for the fish," he said [14].
The thing this doesn't tell you is whether the extra thiamine keeps fish alive. The team measured thiamine concentrations at set stages and analyzed the water. It did not track survival or behavior [6]. The published account is careful on this point: embryos may be able to take up enough thiamine to offset the deficiency [13]. It does not report sample sizes or how large the increase was. A gain that arrives at hatching might protect a hatchling or might arrive too late. A survival comparison between lake and lab embryos from the same eggs would settle it.
For lake trout recovery, the result is a reason to be wary of hatchery numbers applied to wild eggs. It is a weaker reason to downgrade TDC itself. Managers have tried for decades to restore wild recruitment across the Great Lakes region, with limited success [12]. Thiamine deficiency is one obstacle among several. The others are overfishing, sea lamprey predation, invasive species and altered habitat [11]. In hatcheries, staff can already treat the disorder with thiamine [8]. I think the study justifies keeping hatchery mortality rates out of wild-recruitment estimates until someone measures survival in a lake. It does not yet justify ranking TDC lower. The authors argue the pathway should lead to more accurate TDC assessment and better management across the Great Lakes and beyond [15]. So far, though, the evidence comes from embryos in one lake, Lake Champlain [4].
What to watch
- A survival or behavior comparison of lake- and lab-incubated embryos from the same eggs, testing whether the thiamine gain prevents TDC symptoms.
- Thiamine measurements at Great Lakes spawning sites, to see whether their water carries the precursors and byproducts found in Lake Champlain.
- Whether fisheries agencies change how they assess TDC risk for wild recruitment, as the authors say the findings could inform.