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| Photo copyright 2011 & 2012 by Jackson Landers. |
This proposed person will then stumble on to this particular blog entry. It is to you that this message is addressed.
As no doubt you have already learned, Chinese mystery snails are native to Asia and were brought here in order to help keep koi ponds and aquariums tidy. They move around sucking up algae and bacteria from the sides of the tank. They are also happy to eat all sorts of other organic debris. In an artificial habitat this is a very useful habit. But in an established ecosystem, a creature like this is in danger of competing with a whole host of native organisms who have been doing the job quite well. And when you conquer the very bottom of an ecosystem in this manner you are in danger of toppling the whole thing.
They tend to find their way into the wild in North America (I pray that no other continent other than Asia has been visited by these things) via aquarium dumping. A single mature female can immediately release between 20 and 30 live young, which will likely be able to reproduce within two years of introduction. Very few things are in the habit of eating these snails once they are over half an inch in length, though I have personally found large numbers of tiny, newborn snails in the stomachs of catfish.
I want to stress that I have not conducted a fully vetted scientific study of this species in introduced habitats. However, I have gathered them from the wild on many occasions and monitored them in buckets and aquariums for days, weeks, and even years following their collection.
Understand that these aquatic snails give birth to live snails which are essentially miniature adults. They do not lay eggs to develop outside of their shells. Anecdotally, I have found that females are disproportionately likely to release their young within 24 hours after being removed from the water and placed in a suitable new aquatic habitat. I theorize that the offspring are ordinarily held longer than really necessary for survival and that a gravid adult will release the young quickly in response to a cycle of stress followed by relief of stress. This habit should give the species an advantage in colonizing new territory.
Because of this tendency, I believe that Chinese Mystery Snails have a leg up in their early weeks and months as an invasive species in a particular area.
Various chemicals can be utilized to kill Chinese mystery snails in a limited area. These chemicals require special licenses to apply and permits must be obtained from your state or provincial government in order to use them. This is because the chemicals will kill indiscriminately and wipe out many other species. This must generally be accepted in order to remove the snail, but please do not try to do this on your own without a permit.
What you will need to do is get the attention of local and regional government in order to have these chemicals applied. Unfortunately, they will probably ignore you for a while. You are really going to have to work hard to get anyone to care about what is happening before its too late. Talk to reporters for local newspapers. Look for local chapters of groups like Trout Unlimited to partner with. Make a big fuss. But meanwhile those snails need to be kept out of larger waterways where the use of chemicals would be impractical. You need to fight them in the stream, creek or pond for as long as you can until you get the government on your side.
All that you can do is buy time. You do this by killing snails. One at a time.
Get yourself a pair of water shoes or Tevas or something, put on a bathing suit, and carry a bucket. And then you just have to go out there in the water and start picking up snails.
At first you'll be taking the low-hanging fruit. The big adults hanging out in the shallows. But then there are more that you won't see so easily. Under normal circumstances only a small percentage of the total population will be visible in the shallows, if they can help it.
Chinese mystery snails deal very well with cold. They prefer a mild winter (don't we all?) but can hack it through a long, deep freeze. But they do not deal well with a really hot summer. In hot weather they will first go down deep in search of more temperate water. They do the same thing in cold weather, actually. If the heat continues then the oxygen levels throughout the water column may begin to drop. When this occurs they will head upward for shallow water where their siphons can directly access the oxygen that they need to survive. If the heat does not subside within 48 hours then the snails will begin to die en masse.
This happened on various tributaries of the Potomac River in 2010 and 2011. The stink was nearly unbearable. I have observed the same effect experimentally in buckets of a few dozen snails left outside in the summer heat with about 18 inches of water. Within 48 hours, 50% will be dead. After 72 hours of really tough summer heat (in my home state of Virginia) 100% are dead.
My personal observations suggest that the snails do best over a period of several years in shaded streams or creeks with water that runs year-round. In river systems with full sun on much of the river they will tend to follow a 'boom and bust' pattern over the years.
When you are gathering snails you will find it necessary to put your hands in places where you do not want to put them. In an ideal habitat with a constantly running stream over rocks under a canopy of trees, most of the snails at any given time are under rock ledges. You will need to reach into submerged crevices and feel around for the tell-tale round lumps. Grab as many as you can on the first pass and drop them into your bucket. Then reach back in and grab a few more. On the third pass, all of the remaining snails will probably have felt the glancing of your hands and arms and they will have let go of the ledge and dropped straight down. So stop feeling along the top and sides and reach down to the bottom where they weren't before.
There isn't a whole lot of point to re-visiting the same spot two days in a row. Snails move at a snail's pace. The snails that were in the really deep or unseen spots will take a while to move out to where you can see or feel them. Hit the same place once a week and you will find a steady flow of mature snails until they are really subsiding.
Don't kid yourself, though. You cannot totally remove the species any time soon by gathering them by hand. You are missing the vast majority of juveniles, which basically feel like little bits of gravel and you'll never spot more than 2% of them visually. What you are doing by gathering adult snails is reducing the impact of the species on the immediate environment and you are dramatically slowing the expansion of the infestation. You could be the difference between whether this species hits the nearest river in two years or ten years. And ten years is long enough to get the cavalry to finally come. Ten years is several election cycles, and a lot of slow news days that give you a shot at getting headlines for this invasive species.
Be sure to regularly search downstream to make sure that you are knocking the enemy out along the course of its front. Pick up some especially large and nice-looking shells and carry them with you to help educate people about the problem. Above all else, do not stop picking up the snails.
Oh, then you have that bucket full of snails to deal with. Right. Well, you can eat them. Flush the water out a few times a day for a couple of days and they will be very clean-tasting. You can par-boil them for two minutes in order to pluck the meat out of the shells and do what you will with it. Mincing them and incorporating them into some sort of white sauce over pasta is simple enough. They are a lot like slightly rubbery fried clams if you don't take measures to tenderize them.
Whatever you do, don't let them have any shot at escaping into water or else you'll become part of the problem. The snails need to die after you capture them. Freezing isn't reliable enough. Drop them into boiling water, pour a tablespoon of bleach into two gallons of water containing snails, or whatever you have to do. Just make certain that they die. It ain't pretty but it is absolutely necessary.
I have been fighting several infestations of these things for about a year now. You know who cares? Nobody. Neither of us will ever get a medal for this. We will fight this unglamorous aquatic snail that nobody else is interested in because there is a stream or a river or a lake that we each care about. And in that body of water there are tiny little species of native snails and crawdads and fish that might very well become extinct because this invader shows up. None of these little species happens to have a lobbyist or a team of biologists working for them. All that they have is you and me and our buckets and our aquasox. Out there taking down the invaders, one by one.
Now go to work.
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