TOPIC:

There is no new data to share on the alewife population - they do the prey fish surveys in August, so they are just starting that and it takes some time to collect, process, and write up their report. Typically we don't have a decent idea of their findings until winter. Hopefully this is understandable, it is not an overnight process to survey on a lakewide basis and then analyze and summarize the massive amounts of data they collect.

This is the most recent data available - from 2015. Note two things: wide variance in size among yearclasses (e.g. there are 4 different age classes represented at the 155 mm length, so you cannot reliably tell how old an alewive is just on size alone)

The other and more important thing to note is that the bulk of sexually mature alewives are the 2012 and 2013 yearclasses. In 2015, there were very few alewives left from 2009 (I would expect them to probably be all gone this year), only a few left from our best yearclass in recent memory (2010), and only a few from 2011. This is just as concerning as the overall biomass of alewives. If we don't have enough diversity in alewife age classes, their entire population is very vulnerable to being wiped out due to consecutive poor spawns or increases in predation or decreases in survival due to cold winters/not enough food.


For comparison, see the 2014 age/size distribution of alewife, and you can get an idea of how fleeting their yearclasses have been. The blue and yellow chunk from the 2011 and 2010 yearclasses, respectively, was MUCH bigger in 2014 than in 2015. Those 2010 and 2011 alewives have been getting chowed down upon by everything, and they're gonna be gone pretty soon. If we don't have some new sizeable yearclasses come in, we're still in trouble regardless of how much cuts happen to predators
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MC_angler,
Is it correct that lakers, although they feed on both juvenile and adult alewife, preferentially eat the adults?
With the adults seemingly the most critical component to the alewife survival as you are showing, this seems the cut to lakers is all the more important.
Are further cuts on the table in the future if necessary? Will these be evaluated yearly?

lake trout preferentially eat anything and everything that fit in their mouths, I would imagine that due to habitat overlap, they would eat adult alewife more than juvenile

As far as I know, the lake committee is recommending this laker cut as of now because that's all they could quickly come to consensus on (quickly being a relative term, they have been having a ton of discussion). And I have been told they are intending to revisit lake trout and start talking about the more complex issues like the 2020 consent decree and the 1836 Treaty Waters.

"If necessary" is a pretty subjective thing but yeah absolutely - "if necessary" to prevent the collapse to the forage base in the future, additional cuts to any predator could be on the table. I can't answer anything more than that because I don't know - again, this just came out on Tuesday and I do not sit on the Lake Committee. They haven't even put out a press release yet. We're in uncharted territory at the moment and things are pretty volatile both in terms of biologically but also politically, so pretty hard to say how things shake out in the future

Thanks for the response MC_angler. I realize the reductions to lakers are a tougher nut to crack because of the Feds and other parties involved. Here's hoping everyone can stay on board.

www.thenewsdispatch.com/sports/article_a...75.html#.V62yxNRtEUk

some more info., but I guess the best thing is they are trying to accommodate anglers because the strictly science-based answer to saving alewives likely would have been to cease all chinook stockings years ago

Is there any thought being given to trying something different in relation to Indiana chinook stocking? The returns to the streams has been pretty low for quite awhile now. I think Indiana tried some net pen experiments back in the 80's or 90's, can't remember if it was a success or not. Just throwing it out there to try to increase that 1% return rate. I'm sure the charter boat assn and the coho club would be happy to feed them in pens, but maybe this has been shown to be non effective.
Just thoughts

I think multi species reductions are the key at this point going forward. Since the lakers are eating a lot of ales also.

I believe Wisconsin uses net pens, which I read somewhere leads to better survival of their stocked fish since they are larger and more mature when released. I'm not sure if that helps their return rate or not.
Maybe I'm wrong but my 2 cents worth.

Wisconsin only just recently gained approval to use net pens (I think last year or the year before). The reason Wisconsin fish have better survival than anywhere else is because of ideal physical and biological conditions on their coast. They have frequent upwellings due to prevailing westerly winds, which stir up nutrients that mussels have sequestered on the bottom, and make them available to the pelagic food web (e.g. alewives). As a result, they frequently have more bait in their waters than do other states, which does 2 things: provides a food source for salmon, but also buffers predation pressure on the 4-5 inch salmonids as they are acclimating to their new home. Schools of millions upon millions of alewives basically means that stocked salmon smolts can fly under the radar and not get eaten by predators ( whether avian or fish). But if there's no alewives, the smolts are often the only tasty snack in town, so they get eaten.

They also have more rock structure in Wisconsin, which in turn means more invertebrates, which directly feed baby salmonids, and also provide food for baitfish. Finally, (and this is a guess) but I would expect that due to the prevailing westerly winds, they also have a lot more terrestrial bugs blowing into the lake, which is also a food source for baby salmonids.

Michigan uses net pens and has for a long time, but Wisconsin survival/return still kicks their butt. Net pens can certainly help in some areas, but in other areas they have not increased survival a ton.

We have kicked around the idea of net pens for chinooks, likely the place it would help the most is harbor stockings (Buffington/East Chicago). The main advantage of net pens is to let the fish acclimate to their non-hatchery environment while preventing lots of predation. A secondary benefit is holding the fish a little longer and getting them a bit bigger. Trail and Little Cal don't really have those issues because they have time in the creeks to acclimate (and feed and grow a bit), and there's not a ton of natural predators up in the creeks. Unlike say, the St. Joe or other large rivers which are teeming with bass, catfish, walleye, pike, etc.

I’d like to address what Mike wrote in his article, regarding lake trout. I agree with him that we did a pretty poor job of explaining how consumption and biomass estimates go together at the meeting. Part of this is because it is a complex topic and hard to communicate simply, and part of it is because we (meaning Indiana DNR) do not run these models, we simply supply some of the information that is used in the modeling. There are a lot of roles in Lake Michigan management, and no one agency or biologist can wear all the hats, or instantaneously recall all this information. We (Indiana DNR) do the best we can at the meetings to answer a wide variety of questions, and we don’t always have the answer to the question in person at that exact moment, even if we know that there is an answer to the question. What should have been said at the meeting was that yes, obviously you do have to have a biomass estimate to produce a consumption estimate. However, we (meaning Indiana) did not know off the top of our heads what the biomass estimates were, even though we knew an estimate did exist.


That being said, I took the time to get a better answer for you guys. I spoke with the Michigan DNR research biologist who recently updated the consumption estimates to get some numbers on biomass of lake trout. Keep in mind that this report is still being written, so these are “draft” or unofficial numbers. Now, obviously biomass fluctuates over time due to a whole host of factors such as stocking levels, mortality, environmental conditions, changes in forage, etc. But - about 10 years ago, estimated lakewide lake trout biomass was around 5 kt, and now it is over 7.5 kt. Not a shock to anglers who have noticed an abundance of lake trout… the biomass has been slowly and steadily rising over the last decade. Some of this is probably because of increased stocking, some of it is because of reductions in mortality from lampreys, and some of it is probably because of gobies providing excellent additional forage, and also because of increasing natural reproduction.

What Jeremy said at the meeting about needing to get a better idea of lake trout biomass was the simple and short answer to a long and complex explanation. Currently, we (meaning all lakewide managers) have a pretty good handle on the lake trout population in the northern part of the lake. This is because of treaty issues and commercial fishing, which has required better stock analysis in that region. However, we know there are regional differences in lake trout survival, diet, and growth, since they do not move around nearly as much as silver fish, and they have a much more diverse diet. We know there is more natural reproduction in the southern basin compared to the north. There’ve been proposals advanced to better model the lake trout population in the southern basin, because of these factors. That is what Jeremy was alluding to. We’d like to have better information on ALL aspects of the lake, but the reality of management is that with a lake covering 22,000 square miles, we only have so much funding, staff time, and other resources to go around at any one time. Hopefully that doesn’t sound like an excuse, it’s just the reality of managing a giant complex system with limited resources

MC Angler I have a question for you about the lake's food web or pyramid if you will? I was wondering where does the quagga mussel larvae fit into the picture. I believe they are free swimming for a while and I would think they could be a food source for the small fresh water shrimp or other small invertebrates or possibly small fish. Is this something that is even considered since they are an unwanted invasive species?