We should be asking how to improve things. But to make improvements we need to know what is broke.
Damn straight! I completely agree. As fisheries managers, that’s our job. To figure out what’s going on, assess what we can control, and take steps to address things when we can.
The primary thing that is broken, plain and simple, is that there's not enough bait in the lake compared to how things were 10+ years ago, and certainly 20-30 years or more ago. Some of that is due to nutrient loading reductions via the Clean Water Act, and a lot of it is due to mussels sequestering nutrients and disrupting the food web. The rest of it is because there’s too much predation pressure on the remaining bait. That is the only thing we can realistically improve in terms of the bait situation. Our only feasible tool in the toolbox for increasing bait is reducing predation pressure.
How you fix it is by reducing stocking in the short term, so the bait can rebound bigtime, and then you can increase stocking moderately so you don't end back up at Square 1. We’re starting to see the positive results of the cuts, but it’s not like things are peachy. Bait has ticked up, not totally and completely exploded. Quite honestly, I think to really help bait come back quickly, we would need to cut significantly more fish. But given the angler pushback over the previous cuts, I don’t think that’s an outcome that the public would support in the short term, even though it likely would have the best long-term chance of success in terms of building back more bait.
Aside from the obvious purpose of adult fish feeding on it, surviving and growing, there's a couple really important functions that bait provides to baby kings. Number 1 is that when there's a lot of alewives inshore during May, they are a "predation buffer" - everything is eating them, instead of the 3-4 inch chinook smolts.
And Number 2, those inshore alewives need to pull off a good spawn, so that the baby kings can eat those Age 0 alewives in late summer and early fall, so they can survive to become 1 year old kings. The single biggest predictor of a good chinook yearclass is the strength of the same year’s alewife yearclass. Even if you have zero smolt predation, it doesn’t matter if there are not enough alewives for them to eat and survive to adulthood.
In terms of smolt predation, it's next to impossible to measure this directly. Once they are outside the river system it's really impossible to measure. It's a big lake and they disperse. Can't follow every single fish around for months to obtain predation rates upon smolts.
You can, however, make educated guesses based on knowledge of specific stocking locations. For instance, on systems where the fish are stocked way far upstream and there are lots of dams and predators along the way (e.g. St. Joseph River), there's higher smolt mortality from dams and predators. And in smaller systems without resident populations of big predatory fish (like Trail Creek, Little Cal, etc) there is much less predation on smolts within the river system.
The most reliable thing to do to get at the smolt predation question is to measure the returns as adults, compared to how many you stocked. The ones that don't return are dead, through some combination of smolt predation, anglers catching them, and death by starvation/disease/other causes. That lets you somewhat isolate the predation issue from the others, but it doesn’t really give you a “predation number”.
In terms of net pens, those are some really good questions that Ed posed.
The
perception is that net pens provide time for fish to acclimate to their new environment, which helps imprinting, and avoid initial predation when they are disoriented right after stocking. The reality is that this may or may not be true, depending on location. Past reviews of net penning have produced very mixed results by location. This isn’t very surprising, because each stocking site is different. For instance, the imprinting issue is moot if you are stocking upstream in a river system, because smolts do not need much in terms of imprinting. Their outmigration journey triggers them to both imprint geographically and using olfactory cues (how the river smells). So, in upstream stockings, net pens won’t offer any improvement with regard to imprinting. But in a harbor, they probably help considerably.
For predation, net pens would be expected to help most in areas with large amounts of predators right at the stocking site itself, that would feed upon disoriented smolts soon after stocking. This would include harbors and stocking sites near the mouth of very large river systems.
Other net pen considerations: they have to be in an area easily accessible for daily feeding, there needs to be enough flow to supply adequate dissolved oxygen, flush out fish waste and excess food, be in an area not subject to extreme temperature changes, wave action, changing water levels, and ideally be in an area that would not be prone to chemical or fuel spills (eg near a fuel dock in a marina).
The reason we haven't used net pens in the Trail Creek/Little Cal systems is that the systems themselves are offering the same advantages as net pens. We stock the fish upstream several miles, so there are no imprinting issues. There are very few predators in these systems where the fish are stocked, so predation within the stream isn't a significant issue either. Smolts can spread out within the system, find food and cover in the ample woody debris, and outmigrate whenever they want to. They’ve already imprinted, and they’ve already oriented themselves to their new environment, so predation within the stocking site isn’t a large issue either.
There are downsides of net pens in a river system: if the system is flashy (like ours are) a springtime rain can lead to a flood, reducing dissolved oxygen, increasing sediment and large debris, which can affect their gills, potentially cause physical damage to the pen, and or actually kill the fish inside, since they are confined and cannot spread out and go to safer areas, or even ride the flood out to the lake. There can also be issues with fish health and disease that can affect the entire stocking. There are multiple documented instances of entire net pens being wiped out from fin rot, coldwater disease, bacterial gill disease, and other fish health problems. Basically there’s a small chance of direct loss to a substantial part of the stocking since they are all in one small place in the river and cannot leave unless they are released from the pen.
Note that net pens do NOT really solve predation outside of the stream, nor do they solve the problem of not enough to eat in the big lake.
My point here is not to say net pens are useless, but that they are a tool. They are not a panacea. I’m all for using the right tools for the right job.
I reached out to my counterpart in Wisconsin who is evaluating their net pen projects. Their data is still preliminary as there are only a couple years of data available, since the program just only recently got underway.
They are taking a really close look at the Root and Kewaunee Rivers, since they both have weirs and offer very easy and verifiable return data in southern and northern Wisconsin. They used coded wire tags and stocked some of their fish in net pens, and others directly into the river using their normal stocking procedures (just like Indiana’s stockings). This paired design offers a direct comparison between direct stocking and net pens. Then they evaluated the returns of these fish to the weir in the fall.
Those
preliminary results, according to the Wisconsin biologist, are that their data so far suggest no significant difference between net-penned fish and direct-stocked fish when comparing return to their weirs, and actually the direct river stocked fish did slightly better overall
Both of these rivers are pretty similar to Indiana’s – relatively small, not a ton of flow, not a ton of predators to eat smolts, and the fish are stocked within a few miles of the lake. I consider it an excellent proxy for our stocking situation in terms of imprinting and smolt predation potential.
Based on the data he supplied me, over 2 recovery years, at the weirs operating on the Root and Kewaunee they recovered 8.89 fish per 1000 stocked in net pens, and 9.65 per 1000 stocked directly in the river.
So, my take is also that so far the evidence for net pens in Wisconsin is that they are not improving survival and imprinting. I personally would not expect that to change substantially, but there’s a few more important years of data to collect yet before final conclusions are drawn.
With regard to Lake Huron chinooks, that is a giant can of worms. About the only thing I can say for sure is that there’s practically zero chance that chinooks stocked in Lake Huron are going to get added to Indiana’s stocking quota. As per my numbers in the previous post, Indiana already stocks far more chinooks per square mile than any other state. That is unlikely to drastically increase at the expense of other states.
Furthermore, although those chinooks are currently counted for Lake Michigan management purposes, to actually shift those over from Huron, the Lake Huron Committee has to sign off on it. What do you think the odds are of Michigan DNR’s two separate lake committee people saying, hey you know what, we’re totally cool with moving a bunch of chinooks out of Huron and give them to Indiana? And Michigan's anglers being ok with that?
Probably about the same odds as Indiana giving Michigan DNR permission to take all of our chinooks and stock them in Port Huron, wouldn’t you think?
Selfishly from Indiana’s perspective, I’d like to see those Lake Huron chinooks cut entirely, because it would reduce a decent chunk of pressure on the Lake Michigan forage base without substantially affecting our fishery on the south end. But I’m sure the folks in northern Lake Michigan have a different outlook on that.
