Clam Stress and Suggestion

[BonsaiNut]

I am posting this note only after keeping clams for years and reading some of the problems people are having. Note that my thoughts are based on personal experience only - I am not a marine biologist.

In reef tanks over the years I have kept large numbers of tridacna clams. Some of them were purchased, while some of them were collected in the wild (by myself). In general, my success rate was very high and I found these inverts very forgiving once they were established in a reef tank and recovered from shipping stress and/or collection damage. However, when clams start to go 'bad' they can succumb very quickly if the signs are not recognized and appropriate action taken.

Smaller clams in the wild (less than 1') are ALWAYS firmly anchored to the substrate. In most cases, the clams (through vigorous rocking action) can slowly grind away the coral rock beneath them, causing a substantial concave depression that protects much of the clam (and most importantly protects the 'back' of the clam from predators). In some cases, the clam can be over 75% buried in rock, so that the clam shell can only open partially, and when the clam's mantle is withdrawn very little of the clam is visible. In the wild clams are more firmly anchored to the rock (when young) than you would believe - it is easier to remove the clam with the surrounding rock than to try to separate the two. Healthy clams react VERY strongly to stimuli, contracting their mantles into their shells, closing their shells tightly, and anchoring themselves more firmly to the substrate.

The most noticeable way to detect that your clam is in trouble is when it starts to exhibit a 'gaping mouth' look. This is when the clam seems to be gaping open - its two shell halves are open wider than normal and the clam tissues almost appears stretched between the two shell halves. Note that the largest and strongest muscle in a clam is its 'abductor' muscle - which is the muscle that closes the two halves of its shell. A clam's shell is like a spring - if the clam cannot hold the two sides closed, it will automatically open up, even at a time when the clam most needs it to be closed (to recover from damage, stress, etc). I have had clams that demonstrate this 'gaping mouth' look even in tanks that have held other clams that were so healthy as to be spawning and otherwise behaving vigorously.

I have found that once a clam starts to exhibit this 'gaping mouth' look the mortality rate was almost 100% if action was not taken quickly. However, I was able to significantly reduce the rate of mortality to 10-20% by taking a very simple step. I would tie the clam closed.

The idea of tying a clam closed came from the simple intuition that clams close when they are in a risk situation, and that when clams exhibit 'gaping mouth' they are open beyond their normal healthy range. Perhaps (though I don't know) their abductor muscle is damaged, or stress has weakened them to the point where they cannot contract the muscle, so that the natural spring-like mechanism of the shell is slowly tearing the clam in half. Regardless, I use binder's twine or some other reef-safe material to tie the clam closed almost 100%, leaving just a 1/8" opening. In the vast majority of cases, this simple treatment will have a dramatic impact on the clam.

Normally as a clam recovers from its stressed condition, they will slowly project more and more of their mantle through the crack each day. A clam can project almost 100% of their mantle through a 1/8" crack (if the clam is hobby size - 6" or less). Wait until the mantle is fully extended during the day, and then remove the string, or (in cases of severe stress or damage, loosen the strong for a week or two before removing it entirely). Usually clams would recover strength in about two weeks.

I hope this note helps people with their clams, and may save a clam or two. Note that this treatment assumes an otherwise healthy environment (good water conditions and absence of predators). Clams for me were especially susceptible to bristle worms through their byssal opening (at the back of the clam). If your clam releases a brown mucus at the back of the shell, wait until nightfall and check to see what is irritating the clam - in most cases worms are getting behind the clam (something which does not happen in the wild due to the depressions in the rock where the clams live and their ability to rock/grind against the substrate). Note that I have NEVER seen a wild clam in sand. In all cases they were anchored on solid rock. On reefs in the wild you could see where larger clams were harvested by natives for food - the clam depressions were clearly visible.

[jim norris]

Well written and well done! I will try this and let you know. I house about 100 to over 200 clams at any one time and you are right on the money with everything stated. I would like to hear more!
Where abouts in Orange County? I lived in Tustin for about 8 years.
Jim
P.S.
May I reprint this in my website? www.tanku.net
It is all clams.

[toptank]

Have to agree with Jim, Very well written.

I have heard of this method before from a Marine Biologist in Florida but have never tried it.

Barry

[BonsaiNut]

Hi Guys -

Feel free to copy this information anywhere that it might do some good. I was in a store the other day and I saw a stressed clam and I thought to myself - that clam is gonna be dead within 24 hours - but I could probably save it. It made me feel bad, especially when this simple treatment worked amazingly well for me. In the past, I have taken clams that looked REALLY bad and tied them almost completely shut and they have come back. On occasion, with really bad cases, the clam was tied shut for so long that much of algae in the inner tissues of the clam had died off. However, as long as the mantle was healthy, and the clam was gradually reintroduced to full light (by loosening the string gradually over a week or two), the clam colored back up perfectly. As far as I am aware, I have never killed a clam by tying it shut too tightly - clams I have seen in the wild have sometimes bored into stone to such an extent that they can only open 1/8" or so at most, so they don't seem to be adversely affected by the treatment.

Let me know how everything turns out. I expect that you are going to be very happy with the results, expecially if you keep so many clams.

I live in Laguna Hills I actually lived in Tustin myself for about three months when I first came out to Orange County. I LOVE the location and the weather - but the electricity is killing me I left my reef tanks back in Chicago (because of an agreement my wife and I had while we were having children), and have been keeping myself satisfied with a 7000 gallon koi pond - but after keeping a reef there really isn't much challenge with it (though it is kinda fun to be able to swim in your 'tank' while doing maintenance). Of course now I am thinking about starting up a new reef tank and every time I think about the $100/month just for the metal halide lighting I wince.

I plan on going out to Polynesia in about five months - maybe I could take some photos of clams in the wild so people could see what they look like and where they live?

- Greg Peterson

[O'Man]

Starting a new thread related to your post. Hoping you will reply.

[toptank]

I did!

I would recommend you buy the book on Giant Clams by Daniel Knop. Great reading