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| Message Subject: Could it be bad timing? | |||
walleye express |
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 Member Posts: 2680 Location: Essexville, MI./Saginaw Bay. | I just received word that the new DNR agenda for walleye plants has been finalized. And there will be no pond raised walleye fingerling plants this 2006 cycle year in the Saginaw Bay. This policy will be revisited each year with walleye planting criterion based on the Alewife/walleye (YOY) fingerling populations in both Lake Huron and Saginaw Bay. The public response period to this proposal is over, with few if any real concerns (except mine) about letting mother nature take over for man, and keeping us all happy about the walleye status quo on Saginaw Bay. And it's not my intention here to become chicken little and scream "The sky is falling." And to a point, I very much welcome Mother Natures new job as keeper of the "Holy Walleye Grail," on Saginaw Bay. But she is a fickle woman to say the least. And she seldom apologizes or makes up for her mistakes, ask the people in Louisiana. And I'm wondering if fate hasn't put together one of her mistakes, with the timing of this new DNR planting policy this year. I'd be interested to know if the spring floods that started in early May, effected what may have been the fingerlings, smolt or the UN-hatched egg production on the Tittabawassee, Shiawassee, Cass, Flint and many of the other Rivers walleyes spawn in. Many new tons of sediment were transferred downriver during that time, starting around the 7th of May pretty much until yesterday, when I fished the Tittabawassee with clients. Some Dow employees were cleaning what was close to 6 inches of bottom land muck from the ramp yesterday as we were launching. And I'm not seeing the thousands of walleye smolt like I did last year, schooling around the ramp area during this time. I'm hoping the DNR's timing on this one, don't come back to bite it on the butt. And the Lac of concerned comments from Joe Public on this issue prior to this new planting decision, won't happen until or unless the bottom falls out of the catch rate on the Bay in future seasons. That's the way most people are now. Don't bother me until it becomes a problem. I'd like to see DNR River data of the spawning/hatching/fingerling/smolting cycles for our new naturals, and I've already E-mailed my biologist bud for same. I'd like to roughly know the (season timetables) and (climate/temperature variables) they think get the walleyes eggs from the parents body, out to the Bay as smolts. Or if there even is such data known and available after all these years of undocumented, sterile walleye spawning activity on the Bay and it's tributaries. Having a knowledgeable handle on all these variables, would seem to be both necessary, essential, and be useful well before the actual yearly decision and placing of the publics pond raised fingerlings. Knowing we lost a year class of walleyes to Mother Natures whims during that years spring spawning cycle, due to bad weather conditions, would surely guarantee we needed part or all of the pond raised fingerlings to make up for such a loss. String a few years together with unscheduled/unseen surprises, and a Big hole appears in the year class of fish. Just my 2 cents. Edited by walleye express 5/25/2006 10:44 AM | ||
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| terroreyes |
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Member Posts: 300 Location: Lincoln Park, Mi | You know it will. It's just a fact of life we all have to accept, especially with our MDNR. As a rule of thumb, they should take their normal decision making process, then do exactly the opposite of what they conclude. | ||
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| walleye express |
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Member Posts: 2680 Location: Essexville, MI./Saginaw Bay. | Why couldn't they do everything possible to judge rather the spring natural reproduction was successful or not, long before the scheduled fall trawls, that makes it way to late to recuperate that years spring hatch. Strategically placed nets or screens, or trawling equipment with small enough mesh to capture walleye smolt could be utilized at the convergence on the Saginaw River. Virtually ever fish naturally spawned on all those river systems has to go by there at some point when smolting out. If it looked likely that the spring spawn was bad or failed from these samples, we would plant the pond raised fingerlings as planned in June. They say if they deteremine through (fall trawls) that the (spring) walleye spawn failed on a certain year, or the alewife populations show a jump in numbers, they will make up or continue the pond raised plants that fallowing year. O.K. now lets say the spawn fails or is poor in 2006 because of spring flooding. By waiting till next spring we will loose, or at least have a weak/deminished 1 year class of walleyes. Not only that, but then we have to keep or fingers crossed that the pond raised fish to replace them in 2007 don't meet the same fate that last years stocks did, and cook to death while we waited for the go ahead to release them. Or the hundred other things that can (and have) went wrong with pond raised fish since this all started. So lets say we loose the 2007 fish or have a miserable plant then as well. That's 2 year classes gone. Do we continue down this road or change things in a way to hedge our bet. Would you like me to tell you that the bridge is out before you cross it, or after you plunge into the water? Edited by walleye express 5/26/2006 6:57 AM | ||
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| butch |
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Member Posts: 701 Location: upper michigan | I am not sure of about Saginaw bay but up on little bay de noc only a small percentage of the fish actually spawn in the rivers. 2 years ago I saw some vieo of walleye spawning right up tight to shore on the lake then you cant forget the reef spawners. Also you need to think about the forage base available. It seams at the present time the forage is down on Saginaw as compared to the past. This is evident in the lake of alwives and the smaller weight of the fish being caught. Watch a next bite show back a couple months ago and the walleye they caught where of good length but didnt have the weight they carried a few years ago. It may not be a bad thing if you had a bad year class or two so the system has a chance to balance out. I can see your point where you would hate to see a couple years of slower fishing as you depend on your charter for your income. I guess the thing to do is have faith that they will do everything within there power to ensure a healthy future for saginaw bay walleye. | ||
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| walleye express |
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Member Posts: 2680 Location: Essexville, MI./Saginaw Bay. | Here it is; early-life history of wild walleyes in Saginaw Bay: Some of this data answers my questions. Some raises more. Walleye spawning occurs over a period of time lasting about 3 or 4 weeks with the peak (majority) of the activity taking place in about a 7 to 10 day period in the middle of those 3 or 4 weeks (see attachement). When spawning takes place is triggered by day length and temperature. Generally walleye spawning is believed to occur between 46 F and 55 F but I have found that in the Tittabawassee spawning seems to happen a little cooler than that, say 42 F to 48 F. Once walleye spawn, the timing of the remainder of the cycle depends primarily on temperature, or more specifically “daily temperature units”. Daily temperature units or ‘DTUs’ is an expression of how much heating is going on. It is calculated by subtracting 32 degrees from the daily mean water temperature. The result is the DTU. For example; if one had a mean daily water temperature of 55 degrees, then that days’ DTU would be 55 – 32 = 23 DTU. In fish incubation, DTUs are cumulative. Walleye need about 300 DTUs to hatch. If the water temperature is very warm, then they will accumulate 300 DTUs very quickly and maybe hatch in about a week. If the water temperature stays cold, then it could take up to 3 or 4 weeks to hatch. Also affecting this is whether the water temperature fluctuates or not. If it does (and it usually does in the wild), then the total 300 DTUs are necessary. If somehow the water temperature would stay constant, then only 230 DTUs are necessary for hatch. Often in a hatchery situation, the water temperature will be constant resulting in less DTUs being required and a shorter incubation duration. Because spawning activity follows a bell-shaped curve pattern (attached graphic), so will hatching. Hatching can last over a few weeks and again mirror the pattern of spawning activity. Four other factors affect hatch; the are (1) fertilization. If an egg didn’t get fertilized at spawning, then obviously it won’t hatch. Fertilization is not a 100% occurrence but most do and this is just a fact of biology, not environment so much. (2) predation. Eggs get eaten by predators and that reduces the number that will eventually hatch. This too is simply a common biological occurrence. Walleye try to overcome this by laying lots of eggs. Other species like bass try to overcome this by building nests and guarding them. Predation becomes a problem when a new (exotic) egg predator comes on the scene. Round Gobies have that potential. Generally we don’t think they are a big issue in the Tittabawassee in the spring. (3) light. Light levels affect incubation in ways not well understood. Generally clear water is not a requirement, but if for some reason they were denied all light, it would mess with their hatch (duration and %). Lastly is (4) dissolved oxygen. The flowing water will deliver all then necessary oxygen to the incubating eggs but if the eggs become covered by sediment, then they will often die from a lack of oxygen. If a spring flood event came right during incubation, this could compromise the magnitude of the resulting hatch for that reason. Providing these eggs get fertilized, don’t get eaten, and get the necessary light, O2, and DTUs, they will hatch. At hatch they are “fry” or we sometimes call them “larvae”. They are about 5 or 6 mm long and still have the yoke sac from their egg. At his point they need about another 20 DTUs to become active swimmers. Until then, they kind of just lay there I guess. Then once they achieve swimming ability, these newly hatched fry will swim to the surface of the water and gulp in a bubble of air. This is a one-time event to inflate their swimbladder. After that, they will regulate the swim bladder by the amount of oxygen they obtain from the water that becomes dissolved in their blood stream. Several things happen at once during this time period (immediately post hatch). Once swimming they need another 20 DTUs to become active feeders (that is exogenous feeders where they are trying to capture their first external foods). Until this point, they are still feeding on their yoke sac that is still attached to them. They are also feeding on zooplankton. In a fairly short time, they will exhaust their yoke sac and will either have to be successfully finding external food in sufficient quantities or they starve and die. Many biologists recognize the importance of this transition and call it the “critical period”. It’s critical they find ample first foods or they will succumb. The last thing to be happening simultaneously during all this is that they are being swept downstream (if they were spawned in a river) towards the mouth of the river and out into the bay. It is generally believed that the amount of zooplankton in a river is low compared to what’s out in the bay. So in many respects it’s a race to get to the bay before their yoke sac fully depletes (about 5 day maximum). Some studies have shown that a flood event in a river during the hatch is actually a very good thing because it tends to quickly sweep the fry out to the bay to waiting food resources. By this time they are up in the water column and sedimentation is less of a concern. Some fry may be lost to stranding in such a flood event but likely it helps more than it hurts overall. As mentioned, the importance of ample first foods (zooplankton) is fundamental to the survival of these fry. One element of uncertainty is if enough zooplankton will be on hand even in the bay. Although zooplankton are present in the water year-round, they are less abundant in the winter and early spring and become much more abundant (called blooming) as the water temperature warms. If the bay water temperature warming coincides nicely with the hatch and arrival of the walleye fry, then everything works the way it’s suppose to. If for some reason, however, the bay water temperature gets delayed like from a late winter storm, then its possible that the zooplankton bloom will also be delayed resulting in a lot of walleye fry arriving only to find insufficient food resources. This will result in starvation. Compounding this, the walleye fry are still very vulnerable to predation during this time period. They really can’t swim well enough to avoid predators so they are readily eaten by anything that can feed on something as small as a fry. We think alewives come into play in two places. One is that they are such efficient zooplankton grazers that they can crop down the zooplankton bloom and rob the walleye fry of sufficient zooplankton during the critical period. The other way, and the way most people think is probably the primary mechanism, is that alewives eat the walleye fry by directly predating on them. Remember that adult alewives are entering the bay for their own spawning purposes and their preferred temperature for spawning is just about exactly that temperature at which most walleye fry are just reaching the bay. This brings to two together at a most unfortunate time. Because alewives can be so numerous in Lake Huron (in many years) and because they are such efficient filter feeders, they can have a huge impact on these vulnerable walleye fry, reducing their total numbers to a small fraction of what is there otherwise. If our walleye fry makes it to the bay, finds sufficient first foods, and doesn’t get eaten by a predator, then it will grow and grow very quickly. The next stage is the ‘fingerling’ stage. The term “smolt” is reserved for salmon and trout species that do their growing in the river and then make a out-migration to the lake. Walleye do their growing in the bay or lake. Soon they are big enough and a good enough swimmer (say within a few weeks of arriving in the bay) that they can pick where they want to live. By this I mean they can seek out ‘nursery’ habitat. We often refer to these fingerings as young-of-the-year or YOY. We also often refer to them as age-0s. We often find these YOY fingerings on sand flats in the Saginaw River or around the mouth of the river. This may be partly because its easier for us to sample there. My hunch is that they are also making use of the weeded areas for cover. Very shortly during this time period, they transition from zooplankton food to other small fish. It’s at this early YOY fingerling stage that stocking takes place. By covering all the pervious steps in a hatchery or rearing pond, we can maximize their survival. Once released at this stage, its past the alewife vulnerability stage and they (stocked fish) generally do well. The YOY walleye, however, are not “out of the woods yet”. They still endure lots of loss to other predators at this size. If there are very many YOY walleye at this point, they will even compete with each other for food and the best habitat. That’s why we see a smaller average size (slower growth rate) for these YOY fingerlings during these big year classes. A smaller average size has two negative consequences, one is that they are vulnerable to predation losses for a longer period of time and two, they build less fat reserves that they will need to survive their first winter. This is why stocking under this situation is a poor choice. Adding walleye hatchery fingerlings on top of abundant wild fingerlings, only further slows their growth and results in lower survival. Yes, you may get hatchery fish in the fall or next year, but who knows how many wild ones were lost in the process. Maybe as many or more than was achieved by stocking. There you have it. Collectively we refer to all these steps as a fish's "early life history". Walleye reproduction and subsequent recruitment is kind of like one of those things where there is only one way it can go right, and a hundred ways it can go wrong. There are all these steps that have to be timed right and happen in sequence. If they don’t, the result will either be a weaker year class or no year class at all. The latter is actually pretty rare since all these steps are happening over a spread of time (remember the bell shaped curve), conditions may be poor part of the time but ideal at some point too. Walleye like many fish have evolved to overcome much of this by (1) spreading out their spawning period some, and (2) by laying lots and lots of eggs. They try to compensate by sheer numbers. Also spawning is taking place in a variety of locations (different rivers) and sometimes also on off-shore reefs. This diversification of spawning location can also have an insurance effect to ensure that some fry will be produced and survive. I have been participating in an analysis of our annual data sets going back many years to mathematically model the relative significance or effect of many of these different factors. We don’t have good data or representations of all the steps but we have enough to get a handle on it. What this analysis showed is that for Saginaw Bay at least, that the abundance of adult alewives was by far the most significant factor in determining how many walleye fall YOY fingerlings were produced. More than stocking, more that water temperature, more than flow rates, more than productivity (a surrogate variable for zooplankton abundance). Trends in adult alewife abundance explained between 55 and 70% of the annual variability of fall walleye YOY abundance (with few alewives favoring high walleye YOY abundance). That’s a very big amount for just one factor. The others are important too and probably become the next limiting factors in the absence of alewives (like we have been experiencing since 2003). Remember that 2003 was a good walleye year class across the Great Lakes, so that year some ideal weather conditions maximized each of the different steps described above. In Saginaw Bay, that was also the first year of little or no adult alewives. The two factors together really maximized walleye reproduction that year. Since then the weather variables have returned to more normal levels and walleye recruitment around the Great Lakes also returned to normal levels except in Saginaw Bay which stayed high. We believe that’s because of the on going scarcity of adult alewives. Generally we predict that the higher level of walleye reproduction will continue as long as adult alewives remain scarce. We don’t know how long that will be. There are, however, scenarios by which we could get poorer reproduction success even in the absence of adult alewives. That is if walleyes become abundant enough in the bay, that “density-dependent” factors will begin to kick-in and moderate reproductive success. Factors like cannibalism and competition for food and habitat. I mention this because if we see a year class of walleye this year that is less than stellar, it likely isn’t because we didn’t stock, but because these density-dependent mechanisms are probably starting to become a factor. If that’s the case, then stocking would not have helped any. These density-dependent factors are the same ones governing and moderating the amount of reproductive success in fully recovered places like Lake Erie. Eventually Saginaw Bay will get that way too, but really that’s a success story if and when it happens. Edited by walleye express 5/26/2006 1:57 PM | ||
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