Looking for Missing Link

[SlickTony]

The other day someone mentioned that the fish in (I think) Lake Michigan were developing gizzards in order to adapt to their new diet of zebra mussels because the shells tended to tear up their digestive systems. I wish I could remember who it was--I thought I would not forget, but I am increasingly afflicted with CRS (Can't Remember Shit). Is there a news story about this? I'd appreciate any info about it. Thanks in advance.

 

[dr_mabeuse]

I googled on "Lake Michigan fish gizzards zebra mussels" and found nothing, and I'm not surprised.

Organisms don't develop organs in response to environmental pressures. Instead, the pressures favor those changes that help the organism adapt. Developing a gizzard wouldn't happen over night.

I did find some examples of ducks dying because of ingesting zebra mussel shells. Maybe that's what you're thinking of?

---dr.M.

 

[ABSTRUSE]

hope this helps

this is long, but has a lot of info for those who are unaware of what these critters are all about.




ZEBRA/QUAGGA MUSSELS & WALLEYE
- from a fisherman's point of view!
By John A. Vance, Environmental Engineering Tech. and Outdoor Writer


The following article/information is covered under copyright law, and may not be reproduced in any form, without the express permission of the author, John A. Vance. E-mail me for any such permission/requests. (environm@oxford.net)


In this discussion, we'll look at the effect of Zebra/quagga mussels in Lake Erie, one of the world's premier walleye fisheries: EQUALLY IMPORTANTLY - WHAT IT COULD TELL US ABOUT THESE ANIMALS IN SIMILAR WATER CONDITIONS THROUGHOUT NORTH AMERICA.

By now, most of us, especially fisher-folk, have heard of these two great lakes' invaders. Such an introduction of animals into an eco-system, previously devoid of that species, but where living conditions are favourable, can cause a term known as an ‘epizootic'. This is when everything is ‘right' for these animals to grow, and with no/few natural predators established, or disease such as virus, fungus or bacteria present to keep their numbers in check; and they start massive population growth. This massive population explosion is called ‘exponential growth'. Often, such periods of a relatively ‘unchecked' population explosion in an epizootic such as the zebra/quagga mussel invasion of Lake Erie, lasts for approximately 11 years. During this time, natural predators are establishing themselves, and in the case of the Erie mussels, predators such as waterfowl, fish, zooplankton. As well, viral, bacterial and fungal diseases may also be getting established within the zebra /quagga populations - and hopefully is. If a virus or one of these other diseases successfully takes hold, because of the incredibly high mussel population, can make this mussel population ‘crash' quickly, in a ‘domino effect'. It is hoped by most biologists and officials responsible for Lake Erie's health, that this population ‘crash' is nearing. It has been nearly 11 years since these mussel invaders started manifesting Lake Erie, in their exponential growth cycle.

Zebra mussels do well in water that is between 3 feet and 30 feet deep, and their cousins, the quagga mussel likes water up to, but under 80 feet deep - making Lake Erie a mussel's dream come true. BUT IF YOUR FAVOURITE WALLEYE WATER has significant SIMILAR depths - and I'll just bet it does - then you'd best' keep on reading'. Zebra & quagga mussels do well in waters that have the walleye's preferred temperature range too, so on both these accounts, your walleye ‘honey hole' could similarly be in jeopardy - no matter where you are in North America!

When the zebra/quagga mussels first started to show up in high numbers, biologists worried about them taking over (by covering up) walleye's spawning grounds, and felt that this might be a serious threat. Today though, walleye actually spawn right over/on top of zebra/quagga mussel colonies. The walleye eggs hatch out in relatively short periods of time, and the zebra/quagga mussels haven't appeared to be a serious threat in this regard after all. Indeed, it is believed that mussel populations may slightly expand the size of spawning structure, and may actually have a positive effect on walleye's spawning.

But these two critters are amazingly efficient filtering machines, and this is what causes the major problem for water they inhabit. Indeed, most people think that clean, clear water is nice - and it is - aesthetic and pleasing to the eye, to be sure. The problem is, this very clean water doesn't hold much food in that water's eco-system for other life forms, that balance out the many needs of the water's TOTAL ‘life-web. In short, the zebra/quagga mussels are eating many other critters food stuffs, and themselves out of ‘house and home' realistically!

Zebra/quagga mussels being the incredible ‘bio-filters' that they are, are so efficient at competing for food, that they are cleaning up much of the available food needed, such as plankton, small zooplankton, and algae - needed to sustain other life forms in a water body. This food, consumed by the mussels, then isn't available to feed other plants/critters which in turn, in the eco/web of life, feed other and larger plants/critters, and eventually starvation, or severe population reductions of the larger animals - SUCH AS WALLEYE, PERCH, TROUT, SALMON occurs. In fact, walleye puppies, and other small fish fry and minnows eat plankton, zooplankton and insects, and small food particles that the mussels compete with them for. Larger walleye, of course, eat primarily minnows as fodder, and a few insect critters. It should be abundantly clear that if there is no food available for these minute critters, then there will be less of them, and consequently, much less food for walleye in the overall eco/food chain web.

Too, some of these smaller fish/.insects actually use water structure, and its constituents, as cover, such as turbidity, or simply put, unclear/stained or murky water. Much of this ‘stained' water is from the plankton, zooplankton and algae in the water. Once this is gone, then a host of fish can be successful at predating these smaller forage fish, and eliminate the numbers available for themselves and others. This is particularly evident in Lake St. Claire, where water clarity is so much improved aesthetically, that fish populations are in trouble. THIS IS ALSO HAPPENING IN LAKE ERIE - EVEN AS YOU READ THIS ARTICLE! In addition to these actual eco-foodstuffs, zebra/quagga mussels also compete for some of life's needed elements, such as, and in some water, very importantly, calcium, and others (elements) that may not be in over/adequate abundance; hence, this competition can/could prove particularly deleterious to the ‘local' flora/fauna of those waterbodies.

All of the above conditions/statements are why biologists and officials are watching closely, the exponential growth of the zebra/quagga mussels, and are hoping that these animals' populations ‘crash' soon, or at least become predated to an extent that their numbers are reduced, BEFORE A REAL AND POTENTIAL WALLEYE, PERCH, TROUT, AND SALMON FISHERIES COLLAPSE OCCURS! - SPOOKY AIN'T IT!

As fishermen - and anyone concerned with the well being of the Great Lakes for that matter, we should hope that the ‘crash' is buffered somewhat, and occurs over a sure but moderate decline. Zebra/quagga mussels, being the effective filtering machines that they are, have bio-accumulated many/much of the toxins/pollutants that were/are in Lake Erie's water. These toxic nasties aren't gone - just ‘on hold' in the mussels' bodies. If a quick population decline occurs, during decomposition, many of these toxins (pcb, insecticides, herbicides, and many industrial nasties) will be re-released into the water. These toxins will undoubtedly enter into the drinking water of those municipalities using lake water for (mass) human populations, as well as being consumed by other life forms, and ending up in the fish we eat from the lake. Too, a massive (nearly) simultaneous die off of mussels will increase the Biological Oxygen Demand (BOD) within the whole lake, and potentially cause a lot of stinking rotten mess (blunt/crude but effective description)! Hopefully (and optimistically), too, with a moderate decline in mussel population, that many of these aforementioned toxins will be covered over, and ‘locked-up' in the lake bottoms' silt, through the continual natural ‘silting' process going on in the lake. This may not be an eradication of these toxins - but is a whole lot better than all of us - and the lake's eco-life forms, having to consume/be-subjected to these toxins!

We should also look at zebra/quagga mussels in other watersheds, in addition to the great lakes, in that some will be more vulnerable to them than others. Indeed, those waters with little/low calcium/lime, and often consequently with a lower pH, likely won't see large growths of these unwanted critters. In watersheds that are conducive to these mussels, but with marginal calcium/lime in the water, major mussel populations will undoubtedly stress other life forms, also needing the calcium for survival. Fresh water clams, crayfish, and many other species use calcium as a prime constituent in bone formation. Mussels, being very efficient at filtering out of the water what they need, will likely sadly reduce this element, and be a major ‘competition' factor for many of the indigenous species. Fortunately, zebra/quagga mussels don't do as well where pH is lower (more acidic), so many watersheds may end up with a few of these unwanted critters, but with luck, they won't proliferate these waters. Very often, areas of lower pH are also areas of low calcium/limestone.

It is worth noting, that I've noticed first hand, and have also seen where it is documented, that these mussels have a tough time surviving where there is a lot of mud (usually clay) in the water. I believe this ‘plugs-up' their filtering apparatus. While this observation may not be scientific, the concept is so simple that I can't see the need to put a ‘rocket science' explanation to it. Mud/clay silt isn't used by these mussels as foodstuffs. In water that is turbid due to algae, plankton, of other organic matter, mussels will do well. The point is that these bio-filtering animals will clean water with/of organic matter, but not clarify/clean what most regard as ‘muddy' water.

I'm sure that most readers of this article have been ‘bombarded' with the needed information from their local wildlife protection agencies, against the spread of these organisms into their watersheds. I won't go into that here: suffice to say that it is important to realise, and take measures to safeguard against these mussel invader's spread. The key point of this discussion is to make our natural resource utilisers more knowledgable about zebra/quagga mussels, and what they reasonably can expect in their own ‘home' watersheds if these invaders do spread there. But there are a lot of questions unanswered, and many are a ‘time will tell' scenario, especially in the great lakes. Lets all hope that some natural occurring situation arises soon, before the collapse of our great lakes (primarily Erie) fishery. Too, if these mussels enter into a marginal, or frail watershed, conducive to their( mussel's) survival, decimation and collapse of the local fisheries may be a real and sad possibility.

Hopefully the information here has been valuable, informative, and will give you the needed motivation/stimulation/enthusiasm to heed all of the directions to reduce/halt the spread of zebra/quagga mussels. John A. Vance

 

[SlickTony]

Someone told me that the fish with the gizzards are probably gizzard shad, an invasive species that have always had gizzards and are not just developing them. Perhaps they've come after the zebra mussels.

 

[R. Richard]

I hate to lecture people, however maybe this is the time.

People keep pets. When they tire of the pets or can no longer afford to keep them, they dump them pets. If a person dumps a breeding poplulation of foreign beasties in the wild/lake/stream, there is often no predator chain to keep the new beasties in check. As a result, native species die.

Before you dump Shamu or SuperSnail, check with your local college or whatever to find out if you are going to kill a large part of your own environment.

 

[dr_mabeuse]

I’ve been watching the zebra mussel phenomenon since it was first noticed, maybe 8-10 years ago (?). As I recall, they traced them to ballast water from Italian ships that came up the St. Lawrence seaway to the Great Lakes. About 5 years ago I first noticed zebra mussel shells washed up on the east side of Lake Michigan, and now they’re quite common on the west side too.

The problem we have with them around Chicago is that they make the lake water so clear that sunlight can penetrate down to the depth of the intakes through which we get our drinking water. That enables algae to bloom down at those depths, and the algae in turn flavor the water with a noxious chemical that makes the water taste kind of rancid in concentrations of just parts per billion. Not all people notice this taste, but I do. They say it’s not harmful, but who wants to drink stinky water? I can even smell it on dishes that come out of the dishwasher.

This summer hasn’t been as bad as other years, so maybe the mussel population is stablizing or the lake is striking a new balance. We use activated charcoal filters now in my house.

---dr.M.

 

[rgraham666]

Link is missing?

Jesus, I'm always the last to know.

 

[Guest]

rg, you're the first person to really crack me up today. P.

 

[rgraham666]

You're welcome.

 

[SlickTony]

If the zebra mussels make the water that dang clear, it's too bad they can't be managed and used somehow.

 

[Guest]

It was me -

Tony - I posted about the zebra mussels.

The mussels do clear up the water of algae and such - but they are everywhere - on all the boats, nets, docks, shorelines, etc. Pests.

You know, I haven't even looked for any stories about it - I should. In fact, my husband is planning on using this in his science classes this fall.

dr. M. - the gizzards are there - I've seen them. It's pretty obvious when you gut a whitefish.

My family is into our fourth generation of commercial fishers on the Great Lakes. My uncle was pretty surprised when he told us they've been pulling in whitefish with gizzards this summer.

BUT - only from Michigan - the Lake Huron whitefish haven't figured it out yet.

I'm sure it wasn't overnight - but it is certainly here now.

It's kind of exciting - unusual - different.

(Just listen for the Twilight Zone music . . . )