We've tested a couple of other things. We had automated camera systems where you have a flow field. If an organism is present in that flow field, you interrupt the light through it. Based upon the pictures that you get from that, you can try to match a library of images to what you're getting. We found that system did not work well. For zebra mussels they also have a larval stage called a veliger larva, which is very small. It has a unique property that if you hit it with polarized light, you get a star pattern or a cross in your field. When you're looking under a microscope, typically most things look more or less the same, but if you are using this polarized light technique, then if you have these veligers present in your sample, you will see these crosses, and they stand out.
We found that is a very effective way to find if you have them.