TOPIC:

Lickety-Split wrote:

Dave,
maybe we should try something here, that we could do if people were willing.We could keep track on how many natural lakers are making up the total catch rate. I asked Dan Okeefe why a laker ambassador program has never executed. The answer was poor. He mentioned that some were fin clipped over the years but he claimed that the records were poorly handled.There is nothing stopping us from running this experiment for the next season. How many stocked lakers compared to non stock or naturals. We need proof going forward. That is the only way to get down to what really is happening here in Indiana. How many are willing to post their catch and break out stocked vs naturals.

Keep in mind that's only for Sea Grant via Salmon Ambassador program.

I would say there is already definitive proof of what is happening both in Indiana, and lakewide. The federal mass marking program has a boatload of data on wild lake trout caught by anglers since 2013. Approximate % wild lake trout in Indiana starting in 2013 and going to 2019: 13%, 19%, 18%, 18%, 33%, 33%, 40% (2019 data still preliminary and could be revised due to data validation)



Here's a good presentation by Matt Kornis at last year's South Haven Fisheries Workshop.


I think a poll on here for natural lake trout, much like the one for stocked vs wild chinooks done a few years ago, would be great. The chinook poll numbers here lined up almost exactly with the numbers from the mass marking program. Not surprising, as it's the same group of fish being caught by the same general people in the same general area. I'd expect no different from lake trout, with one caveat:

The challenge with lake trout is that anything older than 9 years old has a rotational fin clip (pectoral and/or ventral fin clips) and they can be very difficult to spot unless you have some training and know what you're looking for. Those older clips often regenerated and can be missed unless you look close - many inexperienced folks will mis-classify an old stocked fish as a wild fish. If I was Dan O'keefe that would have been my answer as to why salmon ambassadors wasn't expanded to lakers. The accuracy rate would be much lower than for adipose clip or non adipose clip unless all the participants had good training.

Lickety-Split wrote:

Another way of working with this is to really get working on sending in stomachs samples to be evaluated. Many of these articles like the one I posted are based on lake wide samples.Could we get Prof. Roth MSU to do a special study just on this for the southend?
Jory and Chuck do some very good work. How do we help ourselves.

How many people would follow thru with this?????

Brian Roth does have a substantial amount of stomachs from the South End, as the mass marking biotechnicians have been taking them and then sending them in. One of the complications there is that many of those samples are coming from the summer only, rather than spring and fall. Our office is hoping to rectify that - Phil attended 2 of the tournaments in April last year and collected stomachs for Roth's study.

Obviously the more the better, so hopefully people will be cooperative when DNR or USFWS personnel are out collecting them. Most importantly is that those stomachs have to be completely whole - not sliced open. It's the only way they can be sure that the entire contents of the stomach were received. Here are the instructions www.michiganseagrant.org/wp-content/uplo...ructions-2019-v2.pdf

Ben is doing a great job of laying out the information.
Ed according to the Great Lakes Mass Marking Program for 2019.
2018 Estimated contributions of wild lake trout to fisheries in Lakes Michigan and Huron 
65% of lake trout recovered in Lake Huron had no fin clip and were presumed wild. 
30% of lake trout recovered in Lake Michigan had no fin clip and were presumed wild, and comprised a greater percentage of the catch in southern and central areas.
Approx 40% of Indiana's Trout are from the Southern Refuge, 40% from Julian's Reef and 20% Nearshore Stockings. dnr.wi.gov/topic/fishing/documents/lakem...rkingResults2019.pdf

The 2016 Lake Michigan Lake Trout Working Group Report also has a lot of good information.
www.glfc.org/pubs/lake_committees/michig...%20Report%202016.pdf

In summary, widespread recruitment of wild fish is now occurring in southwest Lake Michigan where evaluation objectives for spawner abundance, spawner age composition, percent spawning females, target mortality, and thiamine egg concentrations (in most years) have been achieved. Recruitment of wild fish, at a lesser scale, is now evident in mid-latitude management units, especially on the western shore. We have shown that managing lake trout stocks to achieve the population objectives provided in the Implementation Strategy remains an appropriate strategy to achieve progress toward lake trout rehabilitation in Lake Michigan.

I would be willing to keep track of Adipose fin clips on the trout we catch. We usually only keep a few and release most without netting. I have seen the ventricle and pectoral fin clips and could keep track of those also.

"Approximate % wild lake trout in Indiana starting in 2013 and going to 2019: 13%, 19%, 18%, 18%, 33%, 33%, 40%"
Very scary how fast this is accelerating.

I could look it up, but remember, not too many years ago lake trout stocks in Indiana (not sure about southern IL or MI,) were curtailed or halted. The increase in wild fish caught, could be a reflection of the decrease or elimination of stocked fish as much as a sign of an ever expanding number of wild fish being born.

This next point is as much theory as proven science but bear with me.
1) The increase in natural reproduction is due to the switch to gobies as forage, away from alewives.
2) When gobies invaded Lake Michigan, obviously there weren't enough lakers to control them so the goby population exploded and they became super abundant. (Anyone remember a decade or more ago when perch fishing was nearly impossible because the gobies would eat all the bait and it was not unusual to catch 6 or 8-inch gobies?)
3) Once the gobies peaked, lakers switched from alewifes to gobies to the point they no longer suffered thiamine deficiency and their eggs started hatching and the lake trout fry surviving.
4) With the influx of wild lakers along with the stocked lakers, the trout started controlling the gobies, eating the big ones first, until now there are very few greater than 4-inch gobies swimming around. One could say they "over controlled the gobies" since about 90 percent of the population is eaten each year - thus the lack of bait-stealing size gobes.
5) The trout now are increasingly dependant on alewives much of the year either because alewives taste better or because it's easier to catch a half dozen alewives than 20 teeny gobies to get a full belly.

My theory then is at some point, as alewives become an increasing part of their diet, it's going to be at the expense of natural reproduction and the "reef" fish from IL and Port of Indiana "nursery" are no longer going to produce numbers of wild fish.

To take it farther, with neither wild or stocked lakers replenishing the lake, trout numbers will dwindle, goby numbers and size will increase, perch fishermen will begin cussing the gobies, what few lakers are left will again switch to gobies enough to get their thiamine level back up to snuff and the lake will undergo another cycle. Unfortunately, the since lakers don't become sexually mature, (or interesting to catch) until age six or seven, it's not going to be a quick cycle, rather one which takes 10 to 20 years to come full circle.

Mike, lot of good thoughts.

Matt Kornis's talk above actually addresses your initial thought - the increase in recruitment is real, even accounting for lake trout stocking reductions the absolute number of wild recruits has been going up. And most of those reductions in the southern basin took place recently enough that I don't think anglers are seeing the results yet, because those fish haven't fully recruited to the fishery yet.

Gobies definitely are thought to be a large part of why lake trout are successfully reproducing. Coupled with significant declines in alewife biomass over the past decade. And, lake trout reproduction has been observed on aggregations of dead quagga mussel shells - it's possible that this is a new and increasing spawning habitat that lake trout are taking advantage of.

Recent diet data show that percentage of alewife in lake trout diets has not shifted substantially in the past 10 years, but rather that gobies have replaced the other non-alewife fish (sculpins, bloater, smelt, etc). On aggregate lake trout diet is about 30% gobies, although obviously that differs seasonally and spatially

Gobies are definitely getting eaten at a high level - very high exploitation. But, to Mike's point, lake trout are opportunistic feeders. They didn't switch to gobies to a large degree until their population had exploded and alewife had declined. IF alewife keep going up and gobies keep getting controlled, at some point there indeed would be a shift away from gobies toward more alewife.

The big irony in all of this is that many of the anglers that do not want lots of lake trout are clamoring to see fisheries managers take actions that increase the likelihood that the lake will become more dominated by lake trout: stocking more salmon, driving the alewife population back down, which favors more and more natural reproduction by lake trout as they will remain concentrated on gobies, which do not contain the thiaminase that alewife do. Alewife generally inhibit lake trout reproduction, which is why in the lake trout rehabilitation plans it's noted that the easiest thing to do in terms of rehabilitating wild lake trout is to drive the alewife population down significantly.


Lastly - some really interesting local/region stuff going on with lake trout. Our spring and fall netting assessments show very low levels of wild fish. Very few wild fish getting reproduced at the Port, despite the huge biomass of adult spawners there. Late spring into late summer, there are wild fish all over the place. I strongly suspect that the concentrations of wild fish are over in Illinois waters during late fall thru early spring, spawning and feeding on offshore gobies, and then disperse throughout the immediate tri-state area during the rest of the year. Illinois netting data corroborate this theory, as they have consistently high numbers of wild fish throughout the year in both their surveys and in the angler catch

Question, in the old days when smelt were prolific, it seemed that lakers were working them over pretty good.
We haven't seen smelt in decades until recently. If the smelt continue to go up in numbers will lakers move from alewife to smelt?

Lake trout would definitely incorporate smelt as well, if their abundance increased significantly. The Lake Huron lake trout eat mostly smelt and gobies, given there is a lack of alewife over there. Smelt also have thiaminase like the alewife