Tip:
Highlight text to annotate it
X
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.