Tag Archives: oyster spat


Tile 2.0- Perfecting the Oyster Spat Tile Experiment

As we’ve been getting this post ready, David’s Apalach crew (Hanna, Stephanie, and Shawn) has begun deploying the experiment featured in the video above in Apalachicola Bay.  After years of perfecting it, the tile experiment has become a key tool in Randall and David’s oyster research.  As you can see, there were some headaches along the way.
If you’d like to know more about spat (young oysters), we covered that a few weeks ago in this video.
Dr. Randall Hughes FSU Coastal & Marine Lab

An "open" cage, with full predator access.

One of the primary goals of several projects in our labs involves figuring out where oysters grow and survive the best, and if they don’t survive, why not? Sounds pretty basic, and it is, but by doing this across lots of sites/environments, we can start to detect general patterns and identify important factors for oyster growth and survival that maybe we didn’t appreciate before. Our method of choice for this task is to glue the oysters to standardized tiles, place some in cages to protect them from predators, leave the rest to fend for themselves, and then put them in the field and see what happens over time.

In doing this lots and lots of times, we’ve learned who in the lab has a special knack for placing small drops of marine glue – Zspar (which you can see in the video) – on tiles, and who is better at adding the oysters so that the 2 valves of their shells don’t get glued shut. These are the sorts of crazy job skills that don’t go on a standard resume!

Any of you who have been following the blog for a while may remember the craziness of the our first NSF tile experiment (Tile 1.0) in the fall of 2010, which involved collecting lots of juvenile oysters (“spat”) that had recently settled in the field, bringing them back to the lab, and using a dremel to carefully separate that from the shell they settled on. (If you don’t remember and want to check it out, go here.)


Two of our oyster "families" in the water tables at Whitney Marine Lab

Since the Tile 1.0 experience, we’ve developed more elegant (and much simpler!) methods: we contract with an amazing aquaculturist at a FL hatchery to collect adult oysters from the field, provide just the right ambiance to make them spawn (release eggs and sperm), and then raise the oyster larvae to a perfect size for attaching to our tiles. This year, we added another twist on this theme (Tile 2.0) by collecting adult oysters from different areas in FL, GA, SC, and NC, and then spawning and raising them separately in the same hatchery under identical conditions. We refer to these different groups of oysters as “families”, because all of the spat from a given location are related to one another, but not very closely related to the oysters from a different location (who had different parents).


Evan and Tanya admiring our work after we deployed the first reef in St. Augustine.

By putting out tiles from each family at sites across this same geographic range (FL to NC), we can tell if some sites or regions are inherently better than others for oysters (for instance, as I’m currently learning first-hand, there’s a reason that everyone wants to spend the winter in FL!), or if some families are naturally better than others (think Family Feud with oysters), or if the oysters that came from a particular site do best at that site, but not in other places (like the ‘home field advantage’ that recently helped Maryland beat Duke in basketball). Whew – that was pretty mixed bag of metaphors! But you get the idea.

We’re still processing and analyzing the data from Tile 2.0, but it looks like which site is the best depends on what you’re measuring – the best place for survival is not always the best place for growth. And the different oyster families do look and “behave” differently – some grow quickly and some grow slowly, and some survive predators better than others.

Spat bred from adult oysters from Sapelo Island in Georgia (left) and ACE Basin in South Carolina (right).

Surprisingly, there doesn’t appear to be much of a home field advantage, at least from our initial analyses. And as Meagan pointed out, we’ve learned from other similar experiments for the National Park Service that it’s not just other oysters or predators that these guys have to worry about – it’s barnacles too! But there are still some ‘sweet spots’ out there for oysters, and once we’ve analyzed all of our data, we’ll have a much better sense for where those are.

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Music by Barnacled and Pitx.

In the Grass, On the Reef is funded by a grant from the National Science Foundation.


Experimental spat tiles, open, closed, and partially open.

Fear and the Choices Oysters Make

Last week, Dr. David Kimbro broke nutrients and oysters down for us.  But what if oysters are too scared to eat the nutrient fed plankton they need to survive?  David and Randall take us another step closer to understanding the Ecology of Fear, examining oysters’ choices and how their behavior affects the important habitat they create.  Stay tuned over the following weeks as they unravel the relationships between predators and prey on oyster reefs and their neighboring coastal ecosystems.  We’ll also continue to follow David’s crew in Apalachicola, Hanna and Stephanie, as they research the oyster fishery crisis.

Dr. Randall Hughes FSU Coastal & Marine Lab

IGOR chip_ predators_NCE 150I recently moved and was faced with the dilemma of finding a place to live. This can be a touch decision, especially when you’re in a new city or town. Which neighborhood has the best schools? The best coffee shop? Friendly neighbors? Low crime? My solution was to find something short-term while I scope the place out some more, and then I can decide on something more permanent. (As anyone who has me in their address book knows, “permanent” is a very relative term – I have changed residences a lot over the last 15-20 years!) But imagine you had just one shot – one, for your whole life – to decide where to settle down. Talk about a tough decision! That’s what oysters have to do, because once they settle down and glue themselves to their location of choice, they don’t have the opportunity to move around any more. So how do they decide?

This oyster shell, harvested from an intertidal St. George Island reef, had been settled by multiple young oysters called spat. Spat grow into mature oysters with a hard shell, fused with the oyster on which they originally landed. Clumps of attached oysters form a crucial coastal habitat.

It turns out that oyster larvae (baby oysters swimming in the water) can use a number of “cues” to help them in the house-hunting process. First of all, they can detect calcium carbonate, the material that makes up oyster shells (and other things) – if there’s lots of calcium carbonate in an area, that could be a good sign that it’s an oyster reef. (Or it could be a sign that people have put a lot of cement blocks in the water in the hopes that oysters will settle and create a reef – that’s how a lot of oyster restoration projects are started.) Some recent research even shows that oysters can detect the sounds of an oyster reef, and then swim in that direction! Maybe these guys are smarter than we think…

Regardless of how oysters decide, there are times when we are also faced with the question of what makes good oyster habitat, or deciding which area is better than another. As scientists, we turn to experiments. One type of experiment that we have perfected over the years involves getting juvenile oysters- (either from the field, which can be pretty difficult -as you can see from the first round of our tile experiment, or from a hatchery), and gluing them to portable sections of “reef” (ceramic tiles weighed down by bricks). LOTS of ceramic tiles and bricks. We’re talking 800+ ceramic tiles and 700+ bricks last summer alone! That’s enough to make a path that is ~2 football fields long. All moved by truck, hand, boat, hand, kayak, and hand to their temporary location on a reef (and then moved back again when the experiment is done). But I digress.

In the second incarnation of the tile experiment, oyster spat were attached to tiles with an epoxy used in the repair of boat hulls. The tiles in the first version- the ones in the video above- were assembled differently. In a video we'll premiere later this month, we'll look at the twists and turns the experiment took.

After attaching the juvenile oysters to the tiles with a lovely substance known as z-spar, we enclose some tiles in cages to protect them from oyster predators, and we leave others with no cage so they are “open” to predators. (There’s also a 3rd group – the “cage control” – that get 1/2 a cage so we can test whether the cage has effects on the oysters other than keeping out the predators.) Then we take our oyster tiles and put them out in the field at different sites that we want to test. By observing the survival and growth of the ones in the cage (where no predators have access), we can get a general sense for whether it’s a good environment or not. Lots of large, live oysters are a sign of a good environment – plenty of food, good salinity (not too salty or too fresh), good temperature, etc. Also, by comparing the survival of the ones in a cage vs. not in a cage, we can get an idea of how many predators are around – lots of live oysters in the cage and none out of the cage is a pretty good sign that oysters are getting eaten. (If oysters in the cage are dead and oysters outside of the cage are missing, it’s a little tougher to figure out exactly what’s causing it, but it’s clearly not a good place for oysters to live!)

Experimental spat tiles at the Guana Tolomato Matanzas National Estuarine Research Reserve- open, closed, and partially open.

Of course, the oysters themselves don’t know whether they are nice and safe inside our cages, or easy pickings for a predator. So if there are lots of predators lurking around the reef, the oysters may try to “hide”. Obviously, hiding for an oyster does not mean packing up and moving elsewhere, but they do have a few tools at their disposal. In the short term, the oysters can choose not to open up their shells and feed (filter water) as often. This strategy has 2 benefits – 1, they are less vulnerable to predators when their shells are closed and 2, they aren’t releasing lots of invisible chemical cues in the water when they’re closed, so it’s harder for the predators to tell they are there. But as any of you who have been sticking to your New Year’s resolution to lose weight will know, there’s only so long that you can go without eating before that strategy loses its appeal! Over the longer term, the oysters can decide to devote more of the energy that they get from eating to create a thicker, stronger, rougher shell, rather than plumping up their tissues.

So, those are the big-time decisions that an oyster faces: where to live, and when to eat. Sounds kind of familiar…

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In the Grass, On the Reef is funded by the National Science Foundation.

Pea crabs at various stages of development. The ones in the center are young crabs, as they appear in the stages immediately following infection of an oyster. The ones on the right are older, harder-carapaced crabs (most likely males, which may leave their hosts in search of oysters harboring females). The crab on the left is a mature female. The developing, orange-colored gonads are visible through the female’s thin carapace. Since mature females never leave the their host oyster, their carapaces (shells) are very soft and thin. This makes them very… squishy and pea-like.

Pea Crab Infestation!

Tanya Rogers FSU Coastal & Marine Lab

IGOR chip- biogeographic 150Serendipitous results are surely one of the most rewarding parts of experimental research. This past winter, I spent many weeks processing various frozen components of great cage experiment of last summer, including the several hundred spat tiles placed inside the different cages at all sites along the coast. It was while delicately measuring and shucking these little spat that I made one such unanticipated finding: Our oyster spat, unbeknownst to us, had become infested with pea crabs.

Pea crabs at various stages of development. The ones in the center are young crabs, as they appear in the stages immediately following infection of an oyster. The ones on the right are older, harder-carapaced crabs (most likely males, which may leave their hosts in search of oysters harboring females). The crab on the left is a mature female. The developing, orange-colored gonads are visible through the female’s thin carapace. Since mature females never leave the their host oyster, their carapaces (shells) are very soft and thin. This makes them very… squishy and pea-like.

You might have had the surprise of finding an oyster pea crab (Zaops ostreus) while shucking an oyster yourself. These small crabs live inside oysters and are a type of kleptoparasite, meaning they steal food from their hosts. An oyster gathers food by filtering water over its gills, trapping edible particles on its gills, and carrying those particles to its mouth using cilia (tiny hairs). Pea crabs sit on the gills and pick out some of the food the oyster traps before the oyster can consume it. By scurrying around inside oysters, pea crabs can also damage the gills mechanically. The pea crabs, like most parasites, don’t kill their hosts, but they can certainly affect the oysters’ overall health.

pea crabs 2

A gravid (egg-bearing) female pea crab next to the oyster spat in which she was living. The female, like most crabs, carries her eggs until they hatch, and then releases her larvae into the water. The baby crabs, when ready, will locate a new oyster host by smell.

As I was processing the oyster spat from all of our experimental sites (Florida to North Carolina) for survivorship, growth, and condition, I began to notice a surprising number of pea crabs living inside them and started to keep track. What’s interesting was not so much that the oysters had pea crabs, but that the percentage of oysters infected with pea crabs varied geographically. For instance, only about 25% had pea crabs in St. Augustine, Florida, whereas over 70% were infected at Skidaway Island, Georgia. Keep in mind that these spat all came from the same source and the same hatchery, so they all had the same starting condition. What’s more, I found that spat in Georgia which had naturally recruited to the tiles from the surrounding waters (of which there were quite a lot, and for which I also processed condition) rarely had pea crabs. Only about 5% of the recruits had pea crabs at Skidaway Island, Georgia. Why is there this huge difference in infection rate? Do the local oysters know something that the transplants don’t? How do these patterns in pea crab infection relate to other geographic patterns we’re finding? How does pea crab infection affect oyster condition? These and many more questions await to be addressed in further analyses and future experiments.

Spat on a Platter

Tanya Rogers FSU Coastal & Marine Lab

IGOR chip_ predators_NCE 150“Spat tiles” are a tool our lab commonly uses to measure the growth and survivorship of juvenile oysters under different conditions, and we’ve used them with varying degrees of success in many of the experiments chronicled in this blog. What these are essentially (in their final form, after a good degree of troubleshooting), are little oysters glued to a tile, which is glued to a brick, which is glued to a mesh backing, which is zip tied vertically to a post. Rob and I have put together a couple interesting slideshows chronicling the growth of these spat over time from two of those experiments. Ever wonder how fast oysters grow? Observe…

This is a time series from our first spat tile experiment, which you can read about in this post. As you may recall, this experiment was largely a failure because the adhesive we used to adhere the spat was inadequate. However, we decided to keep the fully caged tiles out on the reefs to see how they fared over time in different locations. I photographed the tiles every 6 weeks or so, so that we now have a series showing their growth over time. The slideshow shows one of the tiles from Jacksonville. It starts in October of 2010. You’ll notice that not much growth occurs though the late fall and winter, but the spat start to grow noticeably from April-June 2011. From June-September the spat grow explosively and many new spat settle on the tile from the water column and grow equally rapidly. Just as plants (and algae) have a summer growing season, so too do the oysters that feed on them, when conditions are warm and there is abundant phytoplankton in the water to eat.

Next is a series of images from our caging experiment last summer, which you can read about here. Our large cages contained either:


no predators (bivalves only),


spat-consuming mud crabs and oyster drills (consumers),


or mud crabs and oyster drills plus blue crabs and toadfish (predators).

The spat tiles within the larger cages were placed either exposed to potential predators or protected from them in a smaller subcage. Here are typical examples of what tiles looked like at the end of the experiment (about 2 months after starting). You can see how all the spat on the unprotected tiles were wiped out in the consumer treatments, but a good number survived in the treatments with no predators, as we would predict. In the predator treatments, most of the spat on unprotected tiles were removed, but not as fully or quickly as in the consumer treatments, which we would predict if the predators are inhibiting consumption of spat by the mud crabs and drills through consumptive or non-consumptive effects. You’ll see one tiny spat holding on in the predator tile shown. On the protected tiles, most of the spat survived in all treatments, as expected. We plan to further analyze the photographs from the protected tiles though, to see whether spat growth rates differed between them. We may find that protected spat in the consumer treatments grew slower than in the other treatments because of non-consumptive predator effects.

Currently, we’ve recovered most of our arsenal of spat tiles from the field, and I say we have probably amassed enough bricks to pave an entire driveway! Good thing we can reuse them!

The Biogeographic Oyster Study is funded by the National Science Foundation.


Reviewing the Oyster Study in 2010

IGOR chip_ predators_NCE 150IGOR chip- biogeographic 150IGOR chip- habitat 150IGOR chip- employment 150

Dr. David Kimbro FSU Coastal & Marine Lab

David's collaborators, from left to right- Dr. Jeb Byers, Dr. Mike Piehler, Dr. Jon Grabowski, and Dr. Randall Hughes.

As you can see from the video that summarized our efforts over 2010, it was a busy 6 months of research.  After taking a great break during the holidays, the entire oyster team (Jon = Gulf of Maine Research Institute, Mike = University of North Carolina at Chapel Hill, Jeb = University of Georgia, Randall = Florida State University and me) met for a long weekend to figure out what we accomplished and where we are going in the future.

You might think that our 2011 research plans should already be set given that we received funding.  Well, we did receive funding to carry out some outlandish field experiments in 2011, but these experiments were dreamed up in our offices and may not address the most ecologically relevant questions for our system.   Checking in with the monitoring data is probably the best way to determine if our planned experiments were on target or if they needed to be adjusted and hopefully simplified!

Prior to the oyster summit last weekend, I hounded all of the research teams for all of their data.  Given the huge volume of data and everyone’s busy schedules with teaching classes and other research projects, this was quite the task.  Once Tanya meshed all the data together (also not a simple task), I then moved on to the next task of analyzing our data.

Well, the initial excitement quickly turned into a stomach churning feeling of….where the heck do I begin?  Similar to the way that too many prey can reduce the effectiveness of predators, the data were swamping me…I was overwhelmed and the draining hourglass wasn’t helping (people were flying into town in two days…yikes!).

After multiple cups of coffee, the anxiety passed and I decided to revisit some basic questions:


David's team used gill nets to catch the larger fish around the reefs, many of which are top predators in that habitat.

(1) With the gill nets, we obtained predatory fish data.  So how do the abundance and biomass of these fishes vary across latitude? And does this pattern change with season (i.e., summer versus fall)?

(2) Then I thought back to the fond memories of ripping up oyster habitat to check out the abundance of things that consume oysters (e.g., mud crabs).  Oh…the memory of that work gives me a warm and fuzzy feeling; I bet Tanya, Hanna, Linda and everyone else that helped feel the same way!  How do the abundances of these things change across latitude?  Are there larger crabs up north or down south?  How does the mud crab picture mesh with the predatory fish picture?


This spat stick is made of calcium carbonate, the same substance as oyster shell, and is ridged to simulate the ridges in those shells. That makes it an attractive landing spot for oyster spat (larval oysters), which tend to settle on oyster shells.

(3) Working our way down the food web and sticking with the oyster samples we ripped up back in August, how do oyster densities and oyster size change across latitude and how do these patterns mesh with the mudcrab and predatory fish data?

(4) Finally, I wanted to revisit the data from our instrumentation to see how temperature and salinity changed across latitude and with season, as well as the data from our spat sticks to see how oyster recruitment differed.

It’s pretty amazing that six months of work can be summarized so quickly into four topics.  Well, I kept hitting the coffee and got all of these data worked up in time for the first portion of our oyster summit.  Surprisingly, all inbound flights arrived on time and we all assembled last Friday to go over the data.  I’ll briefly lift the research curtain to illustrate what our data looked like:

Jeb cuts blue crab from shark belly

The Georgia reef gill nets trapped a lot of sharks. Here Dr. Jeb Byers is removing blue crabs (also an oyster reef predator) from shark bellies. The trapping done on these reefs is clarifying the food web for these habitats.

(1) Although we predicted predator abundance to increase at lower latitudes, predator abundance and the number of different predators peaked in Georgia/South Carolina.  This is because lots of the species we have in Florida were also in Georgia.  And, Georgia has lots of sharks!  Needless to say, Jeb’s crew has been the busiest during gillnet sampling.  Jon and Mike’s crew have had it pretty easy (no offense)!  The workload reduced for everyone in the fall, but the differences across latitude stayed relatively the same.  The really cool result was the pattern that hardhead catfish are extremely important and the most abundant predatory fish on Florida reefs; I love those slimy things.

(2) Interestingly, mudcrab biomass peaked up north where predatory fishes were less abundant.

(3) And the abundance of large, market size oysters was highest where predatory fish were most abundant (GA/SC).

(4) Amazingly, we all did a good job selecting oyster reefs with equivalent salinities (this can vary a lot just within one estuary) and temperature was the same across all of our sites until December….instrumentation up north got covered in ice!  Glad I was assigned the relatively tropical reefs in Florida.  Finally, oyster recruitment in NC and Florida appears to proceed at a trickle while that of GA/SC is a flood-like situation during the summer.


A month after first being deployed, Tanya and Hanna inspect an Alligator Harbor tile. You can see that some of the oysters have definitely started growing, but also that some of the spat became unglued. When they run the experiment again, they'll use a different adhesive more suitable for a marine environment.

After we all soaked that in, we then talked about the tile experiment.  While these data were really cool (mortality presumably due to mudcrabs was lowest where predatory fish were most abundant = GA), we worried about being able to tease apart the effects of flow, sedimentation, and predation.  Unfortunately, this experiment seems to uphold my record with experiments: they never work the first time.  We’ll probably repeat this in fall of 2011 with a much better design to account for flow and sedimentation.

Before breaking for a nice communal dinner at my place, Mike summarized the nutrient cycling (sediment) data that we have been collecting.  In short, having lots of living oysters really promotes de-nitrification processes and our sampling picked this up.

Putting this all together, it looks like there are latitudinal patterns in fish predators that may result in mudcrab density and size patterns.  Together, these may help account for latitudinal patterns in oysters (highest in GA).  This all matters because more oysters = more denitrification = healthier estuarine waters.


On day 2 of the summit, we worked through what made us happy about the monitoring data, what things we could add on to make us happier, and that we should continue this monitoring through the summer of 2011.  This actually took all morning.


On day 2, the oyster summit moved into the more comfortable location of the Marine Lab guest house.

After a quick lunch break, we then reconvened in another room with a better view (nice to change up the scenery) to go over how we should experimentally test the linkages I mentioned above.  This is where the saw blade of productivity met a strong wood knot.  Personally, I became horribly confused, fatigued and was utterly useless.  This resulted in lots of disagreement on how to proceed and possibly a few ruffled feathers.  But nothing that some good food and NFL playoff football couldn’t cure.

After taking in a beautiful winter sunset over the waters off the lab, we ditched the work and began rehashing old and funny stories about each other.

Amazingly, we awoke the next morning and fashioned together a great experimental design that we will implement beginning June 2011.  To Jeb’s disappointment, this will not involve large sharks, but we will get to play with catfish!

But now it’s time to prepare for our winter fish and crab sampling.  It will be interesting to see what uses these reefs during the dark and cold of winter!

Thanks for following us during 2010, and please stick around for 2011 as I’m sure things will get really interesting as we prepare for our large field experiment.



David’s research is funded by the National Science Foundation.
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