? ? ? ? ? ? ? ? ? ? ? ? Lakeland Currents is sponsored by Nisswa Tax Service.
Nisswa Tax Service offers tax
preparation for individuals and businesses. Across from city hall in Nisswa and on the web at Nisswatax.com. ? ? Hello again everyone and welcome to
Lakeland Currents. Where today
my guest is Doug Schultz, who is a fisheries manager/
supervisor in the Walker area. We’re going to talk about
managing walleyes in large
lakes. And specifically we are going to be talking mostly about Leech Lake because it is one of our larger lakes here
in central Minnesota. Certainly a lot of interest in fishing it. My guest today is Doug Schultz as I said the Walker area fisheries supervisor.
Doug welcome to the show. Thanks for having me Ray. Ray: It’s nice to have you here. It’s on another kind of dreary day, dreary evening we’ve had.
But hopefully the weather will
start turning around for us and we’ll get some of that nice fall that we’ve been hoping for. Tell us a little bit about yourself before
we get into what you do. Where did you go to school? What’s your
background? I’m assuming your
a biologist. Doug: Yep, Yep, My background I grew up
on a farm, dairy farm over by Alexanderia. And I did
my undergraduate study at South Dakota State University
and did my graduate work at Southern Illinois University
in Carbondale. Where we worked primarily
on Asian Carp quite a bit.
There was a recently established
population of the invasive carp there. So that
was roughly three years there. And then moved back to Minnesota
and started working for the DNR in 2006 and bounced
around with a couple jobs temporary employment
over a course of about a year. And then landed in Walker in 2007
as a large lake biologist. Just in the last two years now
I’ve been the area supervisor there in Walker.
Ray: When we define large lakes from your perspective how big of a
lake are we really talking
about? What we, we being the
department, cut it off- in 1983 I’ll give you a little
history here. The large lake
program was established by
the Minnesota DNR in 1983. The purpose of that was
to have a very intensive study/monitoring programming
for our 10 largest walleye lakes. So Cass Lake would
be the smallest at roughly 20,000 acres. And then all
they way up to Upper Red Lake which is the state portion and
you know Lake of the Woods being the biggest one. That was
established in 1983 and then since we’ve done
standardized annual sampling each of those lakes every year
since. What we are really starting
to see now is a lot of value out of that effort. Having those
standardized surveys cause I’m sure we’ll talk about this
in a little bit more detail.
We’re able to start making comparisons
from one lake to another. Not
necessarily the value of catch rates. Catch rates is the number of fish per net. Those are going to vary by lake
because all lakes are different and different productivity levels
and all of those sorts of
factors. But the trends you know the trends in the data sets
are what becomes very
important. That’s what we really rely on when
we are making management
decisions. Ray: There are two things that are close to a sportsman hearts and that is deer hunting. The numbers when
you look at pheasants or
grouse. and fishing, when we’re looking
at the numbers of fish.
Obviously your jobs are more fun when there are lots
of fish and probably a lot less
fun when there is not as many. Doug: Yep.
Ray :When you’ve been
collecting this data across these large areas.
Have you used pretty much the constant techniques so that you
are pretty well comparing one
year to the next with the same area that
you take out of the lake and
the same technique?
Doug: Yes so standardized assessments consists of doing the same thing,
with the same tool over a year net basically, during the same
time of year. Every thing is repeated. And the reason
we do that is we do not introduce additional
variability into the numbers that we are getting. And the reason that’s important is that there is a lot of noise out there anyway that’s natural.
Whether it’s weather induced or fish, most of our gears rely on fish to move for us
to catch them, so movement water temperature and all
these things can play into it. Those factors are extremely
difficult to filter out. By using
standardized gears we at least do not introduce
additional noise on top of
that. And that’s another reason why we
rely on trends than we do on
points. A collection of points, 3, 4, 5 in a row
is a lot more valuable than one independently.
Ray: I know that the general feeling with a lot of fish biologists
even like the University of Minnesota is that climate
change is indeed here. and it is impacting our
fisheries. I know that I’ve gone to a couple seminars where they’ve talked about possible losing ciscos in some of our shallow lakes
because the water temperature
is going to get to warm for them.
Maybe a better ideal habitat for bass and some of the other fish
and not such an ideal habitat for the northerns and the walleyes.
When you guys work together with other biologists are you
starting to see trends of this happening already? Doug: Yeah, so
climate change really has two
different key components to it. One is
climate change as we think of
it. Meaning average summers, on average
summers are getting a little
bit warmer And in a lot of cases we have clearer water because we’ve done
a better job on the landscape. not putting phosphorous, nitrogen
and those sorts of things in. We’ve cut down
on our pollution. So by default that’s going
to benefit species that reproduce and do well during
warmer temperatures or clearer
water You sight feeders for example, bass
and pike are really good
examples of species that really do well in those
sort of conditions. Longer growing season,
warmer water temps on average shorter winters and the clear water.
The other part of that that thread is with cisco are moderate water or marginal cisco lakes
the ones right now where ciscos are kind of on the
fringe of relatively low density
populations make use that use to be really good 15 -20 years ago. It’s kind of that band right through central Minnesota.
In those lakes warmer summers are obviously going
to increase summer stress and increase the likelihood
for summer kill events to
occur. That combined with landscape
changes for example additional development
on some of those marginal waters that right now aren’t heavily developed.
Those kind of landscape changes
increase by default nutrient loading.
Which by default increase oxygen
consumption in the entire
system. And that is the challenge with
summer kill is oxygen becomes
limited. That condition is actually
going to get worse in those marginal waters over time.
Ray: What is the overall health
of our larger lakes if you look at
this corridor from say Mill
Lacs to the Canadian border? Doug: Overall large lakes are actually in exceptional shape. A number of them, Leech is one Lake Vermillion is another one.
A lot of these bigger waters are have had large expanses of
public land around them. The landscape changes have not
been as drastic as they have on a lot of our smaller waters.
Intact watersheds the more intact watersheds
are 75% or more those lakes are actually
are in excellent condition. It’s when we start getting 50-75%
development within the watershed is potential for significant changes
to start happening. Then below
50 % or when development within
the watershed starts exceeding 50% that’s when we start seeing real significant impacts to water quality. And then changes in the fish communities and all sorts
of things are associated with
that. Ray: Let’s just talk a little bit about Leech Lake itself because that’s where you’re working now. I now we were talking
a little bit before we came on
the air, here that you didn’t
actually start working there during the collapse. You kind
of came in at the end of that. But I have fished that lake
most of my life and it was pretty dramatic what we saw there when the fishing just about stopped. It was sort of a mystery to
me to because you could go out and you could hardly find perch there for
three or four years and yet
those perch had to be there because there were
big perch caught a few years
later. Lots of them 12- 13 inchers, I don’t know where they were but they were out there hiding somewhere. That lake’s recovered hasn’t it.
It’s doing pretty well for pretty well now. Doug: Yeah actually fishing on Leech has been exceptional since 2007 already. When we
first started seeing the 2005 year class
of walleyes was the first good strong year class that we had in the
lake in almost 10 years. And
those fish fish were hitting harvestable sizes already
in 2007 and when that happened that’s when fishing up there really turned around.
Now it’s a slot limit that we
have on there right now
which is currently 18-26
inches protected. That’s done a very good job in insuring
that there is always going to
be those mature females
in the system to reproduce as well as being available for
anglers to catch. Even on a
slow day I’d rather throw back 3
than catch none. So fishing quality overall has
improved tremendously there. Our catch rates are
averaging higher year to year than they have in
the past. That’s relevant go back to the ’90’s even when
fishing was red hot on Leech. Our catch rates are still averaging higher overall and our harvest rates are not much lower than what
they were through the ’80s and ’90s even though we
have that slot limit in place. Overall the fishing on Leech has
just been tremendous. Ray: Now
there is rusty crayfish, I think that is the only
invasive species isn’t it that
is in Leech? Doug: We also have Eurasion watermillfoil.
Ray: Oh there is okay there is
millfoil there. I noticed in my career, I used
to fish a lot on the east side of Bear Island, which is Minnesota largest island I believe. And the vegetation that used to be
up and down that east coast is on the east side of it is almost gone.
Now I’ve heard that rusty crayfish could be responsible
for vegetation destruction is
that, do they have that kind of affect? Doug: Yes,
that is basically what they eat
is vegetation Ray: Wow.
Doug: So in some lakes and I think a lot of this is tied to
whatever kind of substrate is
in the lakes. If the substrate is
primarily rock or gravel and cobble and boulder
then you can expect once rusty crayfish are introduced you can expect them to take off and do well. It’s just good habitat for them. Ray: Wow.
Doug: And then we’ve seen in
some other lakes where there is just not a lot of
rock and gravel there it’s more
sand or silt or that sort of
substrate, rusty crayfish are simple present in really low numbers
and they don’t have that big of
impact on vegetation. Ray: So Leech Lake is a
good habitat for rusty
crayfish. Doug: Yep the same reason it’s a good habitat
for walleyes. Rock and gravel substrate both species benefit from it.
Ray: And obviously the young are good prey for walleyes because you see them coughing them up all time when you are fishing them. Doug: Yeah and actually more so
perch. Perch will be stuffed
to the gills with them. Ray: So just talk for a few minutes
if you would about how you gather data in a lake. Leech Lake is
what is it 160 miles of shore. or something like that?
Doug: 211 miles of shoreline
and roughly I think that includes the
islands. And roughly 112,000 acres.
Ray: That’s a big body of
water. How do you go about
collecting data? How do you run your nets so that it is
pretty consistent? Doug: So our normal year will be we’ll
start saning, shoreline saning for young year walleye, perch primarily.
Ray: So is that walking? basically carrying a net or do you
stake them out? Doug: We’ll do
a 100 not 100 a 50 yard
transect roughly 100 feet where we pull it
parallel to the shore and then we’ll bring it around and bring
it up on the shore. That
starts in July and that is 40 total hauls.
So we have 5 sites and we do 2
hauls per site each week
for the whole month of July.
Total of 40 hauls. And then in the same location year after year
we always start right after
the 4th of July. We always wrap up
the last week of July. We take about a week off and
then in August we start
crawling which basically crawl is a net
you drag along the bottom of
the lake. And shrimp crawls
it’s just a small shrimp crawls, is what it is. Drag that along the bottom of the lake for five minutes and that’s one haul at 3 1/2 mph.
So our time there is standardized and the boat
speed and the time of the
haul. Do that at fixed sites and
again during the same weeks, year after year. And then our
gill nets which is really the bread and butter
of what we work with. That’s
were our recruitment information really comes from our
age and growth data. Ray: When
you say recruitment what do you mean? Doug:
Recruitment would be the
relevant number of fish that comprise the year class.
It’s not the relevant number of young year fish, It’s the relative number of those fish that actually survive that stuck around, hit age 3
and are going to reach the fishery at roughly 14 inches.
So that’s our index of recruitment, growth and
maturity rates. All the real vital populations statistics
that we need to make good decisions comes from our guild
net data. And that’s always the first two weeks of
September right after Labor Day we usually set Labor Day. This year we had
really hot water yet that first
week so we threw it off a week.
Cause the water temps were above 70, we like to be right at.
Ray: To protect the fish Doug: Mortality is guaranteed
with gill nets. But it is more so related to movement and ensuring
that their catch rates are
going to be comparable to what they have been in the past. Water
temperature does, when it
starts dropping below 70 that’s when movement
starts increasing and that’s one of things we try to keep
as consistent as possible. You
see the water temperatures
the same. So on Leech we have a total of
36 gill net sets around the entire lake. We do them in groups
of 4 so 4 nets a day. Start at one of the lake,
Kabekona Bay and then Steamboat Bay, and Walker Bay and Agency Bay that would be the first week. The second we will start in
Sucker Bay and work our way
around. But roughly four sets in each
bay. Same location as the previous years.
We have them all gps now. Fish the nets same direction.
Cause our nets are 3/4 inch mesh on one end and then 1 inch 1 1/4 inch,
1 1/2 inch then 2 inch on the
other end. The reason is we have those different
size panels is different size
fish get stuck in there. So we fish
the nets the same direction at the same location year
after year and you’re getting consistency really helps keep
some additional noise out of the data that we work with. Ray: What determines is a good spawning year from
an environmental perspective
versus a bad year? Doug: That’s a really
good question because a year like this one for example
we had a really late cold
spring and fish were ice was no
more melting and fish were spawning because walleyes
anyway were spawning because photo period daylight
lengths said it’s time to go. You would think that it probably
would have been a poor year but . Ray: Yeah that’s what I thought, it’s probably going to be a terrible year. Doug: Yeah but seeing quite a few young year out there. So there are a lot of factors that really go into how many young a year are
actually going to make it the
next year. And that’s really the key question.
It’s not how many are you
starting with. It’s how many you have left at the end
of the day or at the end of the
season. How many you have the next spring basically. And the things that go into that are obviously
what kind of spring we get. If it’s a real cold spring;
for example let’s say they spawn at the normal time and then we get a
real bad cold snap while the
eggs are incubating. And they incubate longer
cause hatching is based on total temperature units
accrued. If that delays hatching we are
going to extra egg mortality. If fry come off and
we get a bad cold snap about the time fry come
off we have roughly 3-4 days they’d absorb the yolk sac and then they have to switch to zoe plankton. Which are little mirco you know
invertebrates. We get a bad
cold snap at that timing you are probably get a high fry mortality because
zoe plankton numbers going to
be really low. You get a cold summer
they don’t grow as well. Growth especially
that first year is pretty strongly tied to water temperature.
So if we have a cold summer growth isn’t going to be
as good and what we do see is survival tends
to go down. We do see that fish don’t grow well in the summer.
So there is a lot of different
things that feed into how many are going
to be around the next year. It’s not surprisingly
it’s not directly fry density driven.
We like to think in straight lines and in straight line
thinking is if you have more
fry in at the start of the year by default
you are going to have more out
next year. And it just doesn’t work that
simple because all these natural checks and balances that go
into it. Ray: So what would a
normal on a good year what would the length of a walleye be at the end of the first year, second year, third year? Doug: On Leech inches we are looking for roughly 6 inches going into September. Ray: 6 inches per year. Doug: Yep that has
really corresponded well year classes the follow year.
Basically we get a bunch of
them you know half or better of
our fall after fishing catch 6 inches or higher you know
a little bit longer. Then they tend to stick around
pretty good. Woman Lake for example just southeast of
Leech which is about 5,000 acres There it is 5 1/2 inches.
Tends to correspond to acres. It’s one of those things that varies
a little bit from lake to lake. Ray: Then in that second year would
they be in that 12- 13 inch
range. Doug: Yeah fall of the second year is going
to be about 10-11 inches.
Seeing about 13 the next year. Ray: Okay so it slows down after the first couple of years. Doug: Yeah the first year is
really the big one. And then by after by age 3 roughly 13
inches are when males start to become
sexually mature. Then their
growth rate actually is going to slow down a little bit because
they are putting energy into
reproduction. instead of getting bigger. And that’s when we
see males and females start to
grow different. rates until the females mature
roughly 18 -19 inches. Then their growth rates from year to year are going to slow down. Ray: So you are looking at pretty good population now I know there was a lot of controversy for the period there was about 4 years where fishing was really tough there. A lot of
people blamed a lot of this on Cormorants I know there has been a real significant harvest of Cormorants Do you think there is data to
show there was a correlation between those populations
falling and Cormorants or still a little gray?
Doug: So the background on this
Ray is the Cormorant population
reestablished on Leech in
1998. Cormorants were historically
not only native by extremely abundant up here. If you
go back through historical
records roughly European settlement
time; number of accounts of really high Cormorant numbers in Northern Minnesota. Post European settlement between just being generally
targeted and then also the use of DDT after
World War II really knocked continental populations down.
DDT was banned in the ’70’s Cormorants were also added
to the Migratory Bird Treaty
Act in 1972 that basically
afford them protection in the true places they were getting
hit hardest. And slowly over
time the continental populations
have rebounded. More so in the 1990’s when they
really started taking off and
doing well. A lot of that was probably tied
to aquaculture in the south and basically extra available
food source in the winter basically in the wintering grounds.
So Cormorants reestablished on
Leech in 1998 and the population really
started to take off exponential rate in 2002. To our surprise in 2004, it really took off. The evidence
that we had at the time suggested that Cormorants
might be having an affect. One of the limiting factors with all that
was we didn’t have a lot of
examples around the country to draw from
where this had occurred
elsewhere. That’s something we do a lot of.
We think we have a problem,
we’ll dig into the literature and see if there
is other places with examples that we can use to help draw
some inferences on what’s going
on. So at the time there wasn’t
a lot of that out there. 2004 when the population peaked
at 10,000 birds in the fall. We worked with the
Leech Lake Band of Ojibwe cause that’s were birds were nesting
was on tribal property on the
island. and the U. S. Fish and Wildlife Service who is basically the administrating agent of the Migratory Bird Treaty
Act to initiate a resource deprivation
order. Which allowed us to start controlling Cormorants in 2005.
One of the things that was tied to that deprivation
order was funding for diet work. So we looked
at Cormorant diets throughout 2005 – 2007
throughout the entire season. And then also again
in 2010 the band did that Independently, sought
independent funding to do that Basically what we saw
is perch made up roughly 60 – 70% diets.
Cisco or tulibee when available are actually
probably are a preferred diet item. Real high
caloric content, a really good
food source for them. Just like they are for
any other predator in the
system. Cisco can actually buffer
predation on other species when they are available.
So perch were 60-70% of the
diet. Cisco up to 50% of the
diet in a given year. When the right size was out there for them.
And then walleye was actually only roughly 3-6% of the diet and again this is by weight.
But 3-6%, 3-7% of the diet by weight during
the given year. That said hindsight, I personally did extra monitoring last year.
Start looking at this in more
detail basically restructured those
walleye year classes from age 3 working backwards.
What that effort showed was Cormorant
predation on 1 and 2 year old walleyes that should have otherwise
been recruited to the
population mortality was probably higher
on those because of Cormorant predation. Ray: So it did have
some bearing. Doug: Yes, so very long winded answer here to give
everybody an appropriate
perspective Yes, what we saw was
a Cormorant predation during the 2000’s.
2001 especially thru roughly 2005, Cormorant
predation was significant.
And certainly implicates that was a cause in the changes
in walleye population. Ray: We
are down to about a minute. Doug: Okay Ray: But you are working on
whether or not to raise the
slot. Doug: Correct Ray: Because you got an 18 inch slot now and I know you’ve had some meetings on this. When do you plan to make some kind
of decision on that? Doug:
Right now the recommendation moved forward that
we’ll move ahead to a 20-26
inch slot starting next year. It still needs to be
approved down in St Paul. That
should be firmed up here by the end of November. Ray: And part of that rational would be is you think there is getting to be too many of that bio mass of that size now. Is that a fact?
Doug: We’ve exceeded our management objective.
Which we have to track Red Lake and Red Lake that puts them in a surplus mode is what they refer to it as and we’re in a similar situation. here. And then we are
also seeing perch are really
taking shorts with all the walleyes we have in the system. So we are going to relax that slot up a little bit see if we can find a better balance. Ray: Well we’ve run out of time and I haven’t run out of questions, Doug: Yeah
I haven’t run out of answers. Ray: But the bottom well is doing
well and rebounding well. And it’s a good sign of things to come.
Doug: Yeah it’s doing
exceptional right now. It’s a great fishery. Ray: Well thanks for coming
on the show, lots of great
information. Doug: Yeah thanks for having me. Ray: You’ve
been watching Lakeland Currents
where we’re talking about what your talking about. I’m Ray Gildow so long until next time. ? ? ? ? ? ? ? ? ? ? ? ? ? ?