They’ve been known to live for 75 or 100 years.
These fish can reach upwards of 20, 30, 40 lbs. in some very, very productive areas.
Really impressive fish — and also fish we like to eat. They’re like salmon, so very
tasty, but a little oily for some people’s taste. So they’ve been commercially fished
for a couple hundred years in the Great Lakes, and they’re sport fish almost everywhere in
their range. Lake trout disappeared from Lake Champlain
around 1900. Maybe in part due to overfishing. Other effects, we don’t know. The State of
Vermont has been stalking lake trout since 1972, and all of the fish you see out in Lake
Champlain right now are stocked fish. The goal is to restore a self-sustaining population.
Why pay for something that could be naturally produced? So my research for the last 12 years, basically,
is trying to find out why lake trout aren’t self-sustaining, given that we’re stocking
them and they’re surviving well into adulthood. We might have enough room to set up here.
Really? I think you’re bound on a rock or a branch.
Let’s go back to the left, then. What is that fish doing just looking miserable?
I’m starting to think about John’s comment about farming deficiency. Are these ones that
are just hanging there? You know, are they the ones that are going, “I dunno.” Now, do you need anything else from up here? About ten years ago, we looked for spawning
areas. We found a number of places where they’re spawning. Then we looked to see whether they’re
spawning successfully there. They are. Then we looked to see whether those eggs that are
deposited in November hatch successfully in April and the fry emerge out of the substrate.
Yes, we’re good there. Are the numbers high enough? Yes, we’ve got very high numbers.
And now we’re continuing to push that research forward to understand what happens to those
fry as they progress through life? Because at the moment, we see no sustained, successful
survival of naturally reproduced fry past about four weeks of age. All of the fish in
the lake are stocked. ROV is a remotely-operated vehicle. Or you
can think of it as a remotely operated video built for underwater use. So what this is
is a little remote-controlled robot, if you will, that allows us to go underwater, and,
from our perspective, what we want to do is just do filming. The densities of lake trout out there are
astounding–sort of surreal after a while. We have to wonder how much of it is artificial
density because they’re attracted to the hatchery effluent, but we don’t know. They’ have an important ecological role as
a predator. So in Lake Champlain, for example, there are really only about three or four
top predators that will eat smelt and the rest of the forage base. It’s the major offshore
deep water, cold water predator. So they help the balance of the lake by consuming part
of the forage base that is smelt. There’s three things that could affect them:
disease, predation, starvation. Disease: we’re fairly confident there aren’t any diseases
we don’t know about in the lake. There’s no weird syndromes showing up that we don’t know
about. Starvation’s a possibility, and the fry themselves, the newly hatched ones, are
feeding very early, very successfully. So they’re not starving. But it is possibly that
once they leave the reef, there’s some imbalance in the food supply. We have to find them to
know whether they’re starving. And at the moment, we can’t find them after they leave
the reef. So it’s difficult to study. Predation’s another possibility. The community
of the lake has changed a lot with the addition of exotic species. We’ve stocked things like
brown trout, rainbow trout. We’ve got alewife in the lake. We’ve got white perch in the
lake. They could be competing for food. They could also be directly consuming lake trout
fry. It’s hard to find that smoking gun. We have
to find fry in the stomachs of those predators after they’ve left the reef. So we can look
at them on the reef, and there’s lots of predation and they are being eaten by a lot of fish
— probably not enough to engulf every last fry. But we have to extend that outwards now
off the reef and see who’s eating them. At about four weeks old, they leave the spawning
reef and they should be going off into deeper water. It gets very hard to follow them at
that point. We never see them again, and that’s our obstacle right now — our black hole. We’ve gone a good ten minutes. We’ll just
get it down to that spot. Yup. I say we do one more video dive. You brought a banana. Nobody told him about
bananas? You don’t bring bananas on boats.