Tuesday, October 14, 2008
Failure to launch, er, or settle, or recruit...
Yes, that is right. Failure. I guess it happens to everyone, and I half expected it by the way my recruitment experiment was going all summer. But I did get that glimmer of hope 6 weeks ago, when I did find a handful of scallop spat on my recruitment squares, and both 4 weeks ago and last week when I saw numerous scallops in our local spat collectors. Alas, no recruits on my squares. That old adage of "If you build it, they will come" does not seem to be ringing true for scallop spat in my grass mats.
Now, I don't want to make this all bad, because clearly highly mobile macrofauna have had no problems discovering or inhabiting my artificial grass mats. In fact, with the water relatively clear last week, I saw numerous species, including tomcod (which I had not seen in Hallock in all my dives there), largish sea bass, and the usual suspects (killifish, pipefish, sticklebacks, cunner, blackfish, porgies). So the whole "if you build it, they will come" theory behind creating artificial habitats or restoring habitats may ring true for certain mobile organisms. However, habitat value aside, no habitat can encourage organsisms to come if those organisms can not get there. Simple. If the supply is low, which I have reason to expect that it is (judging by the almost complete absence of adult scallops from the bay, among other things), it cannot be compensated by available habitat. However, it is still quite possible that I am simply missing the spat on my collecters, since collecting approximately 1 square meters worth of recruitment squares (~500 shoots) out of ~119 square meters of areas (~59000 shoots) may just be too small an amount to see anything. Finding scallop spat on natural grass is akin to finding a needle in a haystack, so why would my mats have been any different? And yes, the number of squares I collect seems low relative to the total area, but over the course of the whole summer, I collected ~5 square meters worth of artificial grass mats, with essentially the same result every time, nothing. Given the amount of hours it takes to locate and collect the squares, then process them, it is alot of work, trust me on that. It just seems to me that supply is very low. Even in the collectors we aren't getting that many, 10-20 per collector, and those are on a mesh that has more surface area than my recruitment squares and are enclosed and thus less likely to be preyed upon. My recruitment squares also don't have that luxury, and I did this on purpose. Maybe next year I will do a predicted vs apparent recruitment survey. I know I am missing some, since we did collect one large seed ~30mm on one of my squares, but not attached to my grass. At least this is a good sign that there are probably some seed out there, and I am hoping in November to do some bottom surveys to find out.