Scallops, and Clams, and Mussels, Oh My!

Post by Bailey Moritz, Scallop Research Intern

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Mussel jackpot! We’ll put these guys back to grow bigger.

The dock has become my office. Since retrieving the spat bags in late July, I have been whiling away the hours, fog or shine, sorting and measuring the baby scallops in all 35 bags that we collected. Eventually, we will map the data to get a picture of where in Penobscot Bay scallop settlement is higher, which can inform fishery management policy. Even though my scallop count is a whopping 14,000 and counting, I can still say that baby scallops are adorable and surprisingly entertaining. These tiny guys are anywhere from 0.1 to 2 cm in height. By rapidly clapping their shell halves together, they can propel water and thus swim to the surface of the jar I collect them in. Check out Hurricane Islands Instagram for a great video of this phenomenon! My swimming jar of baby scallops has been an excellent show and tell for visitors and students pulling up on the dock. In addition to their cute little performance, juvenile scallop shells have colorful and varied patterns worthy of being called art.

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An invasive form of encrusting tunicate forms orange and black mats on the mesh. The little white shapes are clams!

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Baby scallops come in a beautiful array of colors and patterns that they’ll eventually lose in adulthood.

Mesh spat bags are not selective. Any larvae floating in the water column can enter the bag and start to grow. While there are upwards of 500 scallops in each bag, there are usually more than 5000 little clams filling the bag as well. Thank goodness I’m not counting clams! The spat bags came from different locations in Penobscot Bay, and you can tell. Each spat bag displays distinct characteristics from the others. One might have lots of healthy juvenile mussels hanging on tight with their byssal threads. Another may have only larger scallops compared to bags with handfuls of practically unseeable small ones. A number of bags contain starfish, thought to be a predator to the scallop, which might be the cause behind a number of empty, crushed shells. I have seen 7 species of beautiful sea slugs, called nudibranchs, and am now well acquainted with tunicates and sea squirts that find the thick blue mesh a perfect point of attachment. I won’t say the number of times I’ve accidentally squirted myself (or others) in the eye trying to peel them off the bags.

Over the course of the past month witnessing the ebb and flow of the tides from my workspace, I have come to appreciate the diverse and unique ecosystem that is a spat bag. What may at first appear to be a mess of muddy shells, shrimp, and slime, actually holds a snapshot of a coastal marine world in an early stage of growth. I still have a few more spat bags to pick through. But with the dock as my office and swimming baby scallops to keep me company, I really can’t complain.

Desperately Seeking Spat Bags

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Some of the bags were completely covered in fast growing seaweed!

Dripping with muddy water and covered with tiny dancing skeleton shrimp, we spent the day searching for and hauling up lines of spat bags. Cait deployed them this past October, so they have been collecting scallop larvae for the past 9 months. A spat bag is constructed of 2 layers of mesh; the outside green layer having very small netting that only larval stage scallops can enter and exit through, and the inside blue layer with larger netting that they can attach and grow on. 5 bags are tied to a line with a cement block on one end and buoys on the other, suspending them at different depths throughout the water column. Soon, we’ll count all the scallop spat in the bags to gain an understanding of how many scallops are entering these areas and how much settlement might be occurring around Muscle Ridge. The bags don’t select for species, so we’re sure to find lots of little clams and mussels as well. 

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Keeping the pile of spat bags cold and wet with ocean water

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It takes a whole team of eyes to hunt down the right color in the sea of buoys.

Lobstermen generally don’t leave their traps out during the winter and you can see why. The buoys were harder to spot with the colors washed off and some of the bags looked more like we had undertaken seaweed aquaculture! Luckily our fantastic captain, Skip, had a knife handy to clean the outside of the bags as we hauled them up. Strong winter storms can also push the cement blocks across the ocean floor, far away from the GPS point where they were dropped, making it a challenge to find them again. In the end, we recovered 5 of the 12 lines, which luckily included all 3 lines that had the HOBO temperature loggers tied to them! To keep them wet and out of the hot sun, we covered them in burlaps sacks soaked in seawater. After multiple transfers in and out of the water, the spat bags made it on the boat out to Hurricane Island, where we’ll start counting those adorable little scallops.