Sunday, July 11, 2010
Its that time of year again. Scallops have started spawning. Tiny larvae have drifted around and metamorphosed. And now, they are settling out of the water column onto various substrates. I have made this point many times before, but I will repeat it: typically, eelgrass is considered the main suitable substrate for bay scallops, and that their larvae settle out of the water column onto this submerged angiosperm. However, scallop spat appear to be pretty opportunistic settlers, settling on a variety of substrates - both natural and artificial. Some of my colleagues have investigated the settlement of post set on various natural substrates - comparing different abundant macroalgae to eelgrass. This past week we did some diving to look for scallop spat attached to macroalgae in the field. First, I will say it is difficult to spot 1-2mm scallops on a natural surface - they blend in very well! That said, I was able to identify ~25 scallops of the 1-2mm range attached to 3 different types of macroalgae - Codium fragile (my personal favorite and a species I am fully confident is acting as an eelgrass surrogate for many species which rely on eelgrass), Spyridea, and something I call "red puff" algae, because right now, I can't remember its genus. Anyway, we found baby scallops on these three types of algae while diving, measuring the height of attachment and collecting both the scallops (to be measure in the lab) and the algae tuft to return to the lab. We then took wet weight biomass of the algae, and sprayed it down into a sieve (800 um mesh) to see if there were any scallops we missed. All in all, it was a rewarding dive for a variety of reasons, most importantly is that if we are finding multiple scallops on relatively small algae tufts, that is an indication that this years spawning and first set have been very good. This is promising for the scallop population as a whole. Second, it further reiterates that species other than eelgrass can potentially serve as alternative habitats for scallops - and this is important for the restoration efforts along the East Coast. It will allow managers to target some potentially non-traditional areas for restoration. Good stuff!