Nonconsumptive Effects: a story of oysters and mud crabs

Happy almost Thanksgiving, NERRds! We are so thankful for all the opportunities we have and the people that are in our NERRd-y lives. The collaborative projects we are able to work on at the GTM Research Reserve have allowed us to interact with so many different people from a variety of backgrounds and disciplines that bring with them arrays of knowledge. Today, we feature NERRds from a collaborative project that began at the GTM this summer. Hope you enjoy! 


By Nicole Peckham, Guest Writer

One of the best things about science is the ability to travel and collaborate with other groups. We are from Northeastern University’s Kimbro Lab and will be spending the next few years conducting research on oyster population dynamics in the GTM Research Reserve. Specifically, we are focused on measuring the nonconsumptive effects of predators on oysters.


 The Team: Rodrigo Pavani, Nicole Peckham, Dr. David Kimbro, and Adrienne Breef-Pilz

So what does that mean in regular words?

The idea is predators can affect their prey in two different ways: by actually eating them (consumptive effects), or by affecting their behavior and leading to changes in their growth, survival, or reproduction (nonconsumptive effects). For example, when wolves were reintroduced to Yellowstone National Park in 1995, the first significant growth of aspen trees in over 50 years was recorded. To understand how wolves can affect trees, there is one important link between the two: elk.

The wolves caused the elk to change their foraging behavior, which in turn allowed the aspen trees to grow more than they had when the elk had no wolves to worry about. Similar patterns have been shown in other environments, including oyster reefs!


Close up photo of an oyster reef in the Matanzas River south of St. Augustine, FL

An important predator on juvenile oysters is mud crabs, which are small crabs that live in burrows on the oyster reefs. Previous research in the Gulf of Mexico has shown that when exposed to recordings of three vocalizing fish predators (hardhead catfish, black drum, and oyster toadfish), mud crab foraging rates decrease. This can have cascading effects to the mud crabs’ prey: oysters!


Sound recording of an oyster toadfish

Our project is looking at something a little different: how the nonconsumptive effects of predators on oysters by mud crabs and crown conchs can directly change the traits of the oysters themselves.

If some oysters detect that other oysters are being eaten by crabs and conchs, then should we expect oyster traits, growth, survival, and reproduction to also change?

To look at this, we have an experiment set up on the oyster reefs throughout the GTM Research Reserve. Inside large cages, we have dead oyster shell to mimic the reef environment and different densities of predators (mud crabs and conch) and prey (adult and juvenile oysters). To determine the nonconsumptive effects of these predators, we also have a smaller cage inside, with adult and juvenile oysters that will be exposed to the cues of this predation but won’t actually be able to be eaten. These are the oysters that may change their traits over time.


Adrienne Breef-Pilz with our cages set up in Pellicer Flats

Once we have collected the data on these nonconsumptive effects, we will use it to create two separate models of the oyster population in the Reserve. One model will include the nonconsumptive effects, the other simpler model will ignore them. We will test both of these models to see which is more accurate for predicting oyster restoration success. This will allow us to evaluate the importance of these effects.


About the Writer

Nicole Peckham graduated from Northeastern University in 2017 with a degree in Marine Biology. She has since been working as a research assistant in the Kimbro Lab.

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