Giant Clams

Tridacna gigas

Last Saturday, Nick's class had a field trip to the Kosrae Aquaculture Center (Clam Farm) and I was invited to come along!  Amazing.

Nick's video (https://www.youtube.com/watch?v=nrEjllv1yLQ) sums up the trip well.

The Clam Farm also has an Instagram account at clamfarm_kosrae

Here are some of my pictures and comments.

Above you see one of the formerly extinct giant clams (Tridacna gigas) in a tank at Martin's clam farm, and beside that photo is one of a shell of that type of giant clam.  They can grow quite large (3-4 ft) and live for many years (100+).

A mainstay of the farm is this not-quite-as-giant clam (Hippopus hippopus).  These are reproduced at the farm and placed out in pens in the Lelu lagoon, at the Okat Marina, and in Utwe.  The clam farmers are successfully reproducing and repopulating the local area with these clams.

 Hippopus hippopus                                Tridacna maxima

The little blue ones you see (T. maxima) have been selected among many progeny for best color and health.  They will be grown up and put out in the cages. 

The farm grows six species of giant clam.  Martin was invited to run the farm by the local government in 2005.  He has grown the operation and, if you look at his Instagram feed, you'll see at least one report of his farm providing clams to other breeders and aquaria (especially, the Honolulu Aquarium after it lost it's much loved giant clam).

    

There are lots of tanks, all full now with the recent spawning of the T. gigas on February 9.  Clams release sperm first, then the eggs.  Generally they cannot self-fertilize.  Larvae are collected and spread out in the tanks (Martin explains well in Nick's video) where they float for two weeks, then settle.  Martin points out that the larvae settle in groups, somehow knowing where each other are.  This makes it more likely their eggs and sperm will find each other after spawning.  

With luck, out of millions of eggs and sperm, thousands of larvae will settle and then .... many baby giant clams will grow.  There is a lot of maintenance of the baby clams, flushing with water brought from the lagoon, making sure nothing leaves the tanks except water (filter keeps the larvae in), feeding with zooxanthellae to set up the mutualism necessary both for clams and for coral reefs!  

And patience.  

Yes ... the farm has backup generators; they would be out of business with lots of dead clams if the power were off for hours.

  

Martin set up for us two tanks with two species of clam (H. hippopus and T. derasa I think).  The hippopus had recently been collected from the pens at Otak Harbor.  As Martin explained, they may already have spawned, who knows, but he would give it a try. 

 He injects the gonads with a hormone: 60 seconds later he watches for a smokey cloud to be released.  These are sperm.  They are collected from the tank and set aside. Then that clam is isolated into a separate tank.  She is washed with sperm from a different clam (or injected).  If she releases eggs (you can see this below, if you look carefully, a small snowstorm of eggs is being released from the clam) they are mixed with sperm from a different clam, and life begins anew.

Sometimes, very rarely, a clam makes a pearl.  This one is tear-drop shaped, so unusual and snowy white.

The farm is also regenerating coral, successfully!  Here you can see the 'cookies' made of cement onto which pieces of coral are glued and allowed to grow in tanks until large enough to put out onto the reef.

Martin's wife Delphia has two side operations.  One is making clam products, wildly popular in Japan and costly.  Another is pizza, by far the best pizza I have ever tasted, ever, anywhere.  

  

This is the view of Lelu lagoon from the clam farm.

Same lagoon I swim in.

Magical