St Croix River Population Report DNR 2010

Below is the Discussion portion of the 2010 Population Assessment of Lake Sturgeon in the Lower St Croix River.

At the bottom of this post you’ll find a link to the full report.

Discussion

The present population of lake sturgeon in the
Lower St. Croix River consists of a large
proportion of immature fish. Given the
migratory nature of this species and the fact that
the Lower St. Croix is an open system to the
Upper Mississippi River, an estimate of the
present population with any degree of accuracy
will be difficult to attain (Knights, et.al. 2002).
Because of these factors, the present calculated
population likely underestimates the actual
population that is present at any given time
significantly. To date, no movement patterns or
habitat preferences can be determined from
reported recaptures.

Project data indicates the lake sturgeon in the
Lower St. Croix River exhibit a slower growth
rate than fish from more fertile river systems. It
is also evident that lake sturgeon in the study
area exhibit a poorer condition than fish in other
river systems. We’re finding that the sturgeon in
the Lower St. Croix average over 12 percent
less in weight than fish of the same length from
other heavily studied populations in North
America. Our data even reflects an overall
relative weight (as determined from a length –
weight regression) of approximately 6 percent
less than that observed by the WDNR in 1986-
87 in these same waters.

Sampling results to date have also yielded very
few fish that are likely mature females
(approximately 1397 mm or mid-50 inches). It
is well documented that individual male lake
sturgeon spawn every 2 to 3 years, and
individual female lake sturgeon spawn once
every 4 to 6 years after reaching sexual
maturity. There is also some speculation that
females may not even spawn the first year that
they become mature. Given these spawning
intervals, it is likely that less than 30 percent of
the adult fish in the population may be sexually
active in any given season.

Sampling efforts during this project indicate that
lake sturgeon are very vulnerable to targeted
angling pressure. Given that lake sturgeon are
long lived, slow growing, and require a long
time to reach sexual maturity; present
populations could be threatened by the growing
popularity of this species as a sport fish.

From 1992 through 2008, regulations on the
Lower St. Croix River allowed the harvest of
one lake sturgeon 50 inches (1270 mm) or larger
(total length) per angler per year during a
limited angling season extending from the first
Saturday in September through October 15th.
Since 2006, anglers wishing to keep a lake
sturgeon from these waters have been required
to purchase and possess a special harvest tag
prior to having a legal size fish in possession. A
total of 16 lake sturgeon have been reported
harvested since initiation of Minnesota’s tag
reporting system. Five of these fish have
measured 60-inches (1524 mm), or more, in
length.

Fisheries managers had been concerned that
given the slow growth and the below average
condition for fish observed during this project,
the 50-inch minimum harvest length (1270 mm)
may be too liberal for the lake sturgeon in this
system. Until more information is available,
both Minnesota and Wisconsin are in joint
agreement that the harvest regulations should be
made more restrictive to protect female lake
sturgeon until they have had the chance to
spawn at least once. Beginning with the 2009
season, a 60-inch minimum harvest size (1524
mm) for lake sturgeon has been enacted on the
Lower St. Croix River. The harvest limit will
remain 1 fish per year for anglers who have
purchased a harvest tag in advance. The harvest
season has been shortened from the first
Saturday in September through September 30th.
An additional 15-day catch-and-release only
season was established that runs from October
1st through October 15th for anglers possessing a
Minnesota fishing license.

Ideally, data from this project should serve as a
foundation for biologically-based management
decisions to insure that lake sturgeon continue
to have strong presence in the Lower St. Croix
River. Given that we are working with a long-
lived and slow growing species, it will be
necessary to collect information for a long
period of time to do a thorough and proper
evaluation of this population. Future efforts
should also address the data gaps that are
evident in the present project that hinder more
informed management decisions. Besides the
need for data on growth rates of larger fish and
age of maturity for each of the sexes; telemetry
work is needed to better understand movement
patterns, preferred habitats and spawning
periodicity. Other issues that should also be
addressed are recruitment, natural mortality,
hooking mortality, and incorporation of PIT tags
on all marked fish to enable estimation of tag
loss.

I’ll be adding a link to download the complete PDF file hopefully today.

Very interesting. I wonder the reason(s) for the Croix sturgeon being in “poorer condition” than other populations. There seems to be a good forage base on the Croix.

Not sure here, but considering how old these fish get before they spawn, wouldn’t it make sense to cut the numbers and make over 50″ fish not keepers???

I guess I don’t know what lenght/age they are at max spawning capability, but I’d think whatever it is, that’s the fish we want to protect..imho

Al

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Not sure here, but considering how old these fish get before they spawn, wouldn’t it make sense to cut the numbers and make over 50″ fish not keepers???

I guess I don’t know what lenght/age they are at max spawning capability, but I’d think whatever it is, that’s the fish we want to protect..imho

Al

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So true! Unfortunately the reason some people harvest them are for the eggs, so an immature female won’t do anything for them.

Now that makes me wonder about Sturgeon on the Croix. You can only take them in the fall. I assume like most fish that spawn in spring the eggs are non existant or underdeveloped in the fall. So my first point is moot for St. Croix. Seems that if that is the reasoning, maybe they should have special regs for St. Croix sturgeon. Nothing OVER X”.

Looking at the harvest numbers, there are hardly any sturgeon taken out of the river (legally, at least). Maybe they should got to all C&R, but it probably doesn’t matter too much.

Myself, I would like to try it, but I sure ain’t keeping a 60+ inch sturgeon. I keep meaning to throw a shovelnose in the livewell from P4, but I haven’t actually done it yet. Seems to be about the only way I’m gonna get to eat sturgeon.

It would be very interesting to add up how many rod hours we put in there on the Croix last fall. A safe assumption is at least 500 hours. We had numerous fish over 50 and several in the mid to high 50’s, but I don’t think we ever broke 60 once. I don’t remember for sure, we might have caught 1 or 2 at the very most, but I don’t think so. A 60” fish is pretty rare in that system. You hear and see a few each year, but very rare indeed. Now add into that the number of people who are going to harvest one, and the overwhelming odds are that very few (if any) will ever be harvested. I guess the numbers show that with only 1 in 2010.

With that restriction in place, I sure would like to see an extended season. Why criminalize people who want to go out and have some fun battling these giants if their intention is to release them, and/or the restrictions are so tight that by default they are going to have to be released anyways. Keep the slot tight and open up the C&R season year round. Why not? Oh and at the same time, why not open up the Upper Croix and Miss too. That’s just silly you can’t C&R fish for them there.

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Looking at the harvest numbers, there are hardly any sturgeon taken out of the river (legally, at least).

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Thanks for pointing that out. I didn’t actually go back and see how many were harvested from the Croix.

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So my first point is moot for St. Croix.

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Remember, a female sturgeon will carry the same eggs for 4 to 6 years. I haven’t a need to know when they are ripe enough to harvest.

I just received an update from the DNR on the Rainy/LOTW’s numbers. I’m correcting them in the post now.

Seems like alot of words but not much said. The poor length to weight ratio is pretty evident when you compare a St. Croix sturgeon to a Rainy River sturgeon.

Any word on a longer c&r season? I understand that this will not help the population in any way, but it might help the human population because we won’t have to risk our lives in the warm months to catch some of these awesome fish.

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Seems like alot of words but not much said. The poor length to weight ratio is pretty evident when you compare a St. Croix sturgeon to a Rainy River sturgeon.

Any word on a longer c&r season? I understand that this will not help the population in any way, but it might help the human population because we won’t have to risk our lives in the warm months to catch some of these awesome fish.

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Ya mean you don’t find a 36 foot cigarette boat going by you at 60 mph exciting or wondering if that guy in the 40 footer coming to wards you actually sees you????

I didn’t know there were that few getting harvested either.

Al

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Ya mean you don’t find a 36 foot cigarette boat going by you at 60 mph exciting or wondering if that guy in the 40 footer coming to wards you actually sees you????

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But a lot of that is made up with great hull ornaments and boat trophies. Unfortunately, they aren’t as exciting during those colder fall days.

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Ya mean you don’t find a 36 foot cigarette boat going by you at 60 mph exciting or wondering if that guy in the 40 footer coming to wards you actually sees you????

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But a lot of that is made up with great hull ornaments and boat trophies. Unfortunately, they aren’t as exciting during those colder fall days.

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Ya, it’d be a lot nicer if they’d slow down so I could find my binoculars then too…:)

Al

I’ve always wondered if the big sturgeons might be better targeted with a suspended bait instead. Afterall I catch them all suspended like crappies during the winter time.

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I’ve always wondered if the big sturgeons might be better targeted with a suspended bait instead. Afterall I catch them all suspended like crappies during the winter time.

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Once they catch the scent, it probably doesn’t matter where the bait is. Still, they are built to dig stuff out of the sand and it is probably easier for them to grab is off the bottom. Then again, if they are hanging out in the middle of the water column, they might miss the scent trail.

After reading some of these posts,I was wondering what a longer season would do on the Croix. Figured I would ask a biologist that’s been working with them for around five or so years. He made some very valid points that should be considered.

My thought was to extend the end of the season for catch and release although I didn’t mention when in my question to him. His response follows:

It’s hard to answer that question, without knowing how big of a C&R window you are thinking of. Extending it a couple of weeks later into the Fall, likely would have no biological effect. On the other hand, extending the season the other direction, there could potentially be some negative effects. LKS are a cool water species, and thus are less tolerant of temperature extremes in water than warm water species. Consequently, angling for them during the summer months when water temps are high runs the risk of increased the delayed mortality from physically stressing individuals when they are already thermally stressed. Angling for them in the spring runs the risk of disrupting the spawning behavior of individuals or increasing the delayed mortality by stressing already weakened fish that are post spawn. And of course, ice angling increases the potential for “break-offs” resulting in more fish swimming around with hooks embedded in areas of the mouth or throat that may inhibit their ability to feed normally. I’m not saying that these things “will” happen, but they have the “potential” to occur. So much depends on each individuals physical condition, how they are handled, and external environmental factors at the time of capture. Since there is no hard and fast rule to give you a definite biological answer, I can only speculate on generalities.

I would suspect that there may be an even greater sociological risk to the fishery than a biological one. Lengthening the season would potentially open the door to increased angling pressure on a individual species by calling more people’s attention to it by affording them a larger “window of opportunity” to partake in targeting those fish. More pressure = more competition for fishing spots and likely will increase the incidence of delayed mortality of fish that are caught and released. Many anglers are already expressing concern over the increase in angling pressure on the Croix LKS fishery that they have observed in the just last 5 years. Presently, one of the factors protecting LKS in the Lower Croix is the timing of the current season. Many outdoorsmen are busy in the limited duration hunting seasons in the Fall, and are not willing to pass on that opportunity to go fishing. I know several people who are intrigued by the idea of LKS fishing, but who have their Fall weekends already planned out for hunting and are unwilling to change their traditions!

I know that you are looking for a concrete answer to your question, but unfortunately, I can only give you general speculation or possible scenarios of concern. When I’m in doubt about something, I always tend to fall back on a principle that I was brought up with…”If it ain’t broke, don’t fix it”!

I hope this provides you some food for thought or helps to shed some light on your question.

I can appreciate the DNR being careful with the St. Croix population.

I’m sure they could make a valid argument for not being able to fish for them at all

Because they have whiskers and have a sucker for a mouth and aren’t pronounced ‘wah-lie’ they just will never be looked at in the same light as other game fish(as far as management goes).

I nominate the “break offs” argument in the winter as a candidate for the “Most preposterous statement of the year”

Not sure I am following you on the second statement. Seems to me that they are much more careful with protecting and managing the fish than they are with walleye or even musky.

Unless you are equating management with how much opportunity they give us to fish them. Guess I am confused…again.

I don’t know Mike, I guess I’m talking out of my butt and no doubt not making any sense. It wouldn’t surprise me if I was confusing everyone. No offense about the preposterous statement, just a silly KFAN reference.

I just get so frustrated about the whole thing. You have people who are out blatantly fishing for them in bodies of water they shouldn’t be, through the ice, and during closed season. These are fine folks who really don’t want to break any laws, they just love to fish. The picture through the ice a couple of months ago was a PERFECT example.

Sturgeon are tough fish and on the St Croix we are allowed only about 1 good month to fish for them. It saddens me. The harm to them to extend the C&R another 2 months would be minimal at worst.

Not to mention that if we are disturbing the spawn in the spring than we have hypocritical regs from one part of the state to the next. Which doesn’t surprise me with the whole 2 line in the winter and 1 in the summer…..but I’m not getting into that one.