Crab Vs. Oyster

Interviewing a Scientist                                                                   July 15, 2016 @ 9:00 a.m.

Q. So the first question is, what is your degree exactly that you are pursuing?

A. I am getting a Doctorate in Marine Biology. We have two, well kind of three, programs here that are marine oriented. We have marine biology which is more like research into the specific organisms, ecology and that kind of stuff. And then we have CMSS which is Coastal Marine System Sciences which typically is more like about interactions with humans and animals. One of our students that was in CMSS did toxicology on Blue Crabs and pesticides that the ETEAMS have helped out with and how the pesticides affect the blue crabs. They do a lot of coastal wetland type research that is not necessarily marine.

Q. Right, okay so that brings me to my next question, I thought I had heard something about how everyone that works under Lee is specific to freshwater studies is that true or is that something that maybe I just thought I had heard?

A. No. Laughs. There are a lot of people that do freshwaters.

Q. Right but it is not specific to anyone that works under Lee.

A. Right, no.

Q. Okay so what are the two projects that you are currently working on. If you want you can talk about the one that is no longer continuing and then what you are specifically working on so we can branch off of that a little bit.

A. The one that we are not doing this year was looking at the defenses that we have seen in oysters. Um, we know that they produce them if we rear them from spat and up and we know that if we rear them from seed and up we can get them to produce them over a period of time.

Q. And by defenses what do you mean?

A. They are making changes in their shells that make it more difficult for the crabs to eat. We will sometimes look at diameter, we look at shell weight, but the most reliable predictor seems to be shell strength and how much force the crabs would actually have to exert in order to crush the shell. So those changes seem to stop at some age and the idea with is it could either be because when they are little they can turn it off and on and then as they get bigger they lose that ability or it could be that there is something about being bigger that it’s not worth that effort that they would have to put into it. So the idea there was to see first of all, if they could turn it off. So we were going to raise some of them with crabs and some of them without and then we were going to do a second period where half of them kept the same treatments and then the other half switched to a new treatment.

Q. So that of course is the one that you are not running anymore?

A. Yes. Part of that is because at the time when I originally proposed this experiment we did not know that the seed oysters would respond.

Q. Was it because of size?

A. Well it was because we had only been running them for only two months.

Q. Oh okay, so it was because of timing.

A. Yeah I didn’t think that we could see the responses. So the idea was during the first period to grow them up to the size that the seed oysters are when they start and then to change so that they are essentially seed oysters growing during the second half. And then we found that the seed oysters do respond! And then the other thing is that the spat aren’t coming and if they do end up coming then they will be sketchy and we will be running the experiment until the next year.

Q. And by sketch of course you mean that even if they do bring them you would be worried about them dying anyways?

A. Yes. So they have had several spawns this summer and none of those have seemed to survive.

Q. So then the one that you are currently pursuing right now, how is that a little different? I know that the spat and seeds are different but like what else? Are you looking for the same kind of thing? How is your hypothesis different?

A. I am looking for the same changes in the shell. But this one is one of a number of studies that I have for my dissertation – looking at factors that influence how and when oysters will produce the defenses. So whether they will produce them under a range of conditions and then if they do produce them do they produce them to different intensities… And so crabs might be around all the time, it might just not be the same crab and crabs are not necessarily coming on for like a full day at a time. It might be that they are there for a certain amount of time each week but it is not continuous. So the idea with this study is we would have one that stays in the control all of the time, one that’s in the predator tank for 24 hours a week, three treatments that are in the tank for 72 hours a week. The first of which is in for three days straight at the beginning of the week, the second is in for three days straight at the end of the week, and then one that is in for three days broken across the week, and then one that is in the predator tank all the time. And so we will compare all the different time lengths to see if it matters how long they are in there, and we are thinking that it will be since we kind of already have some evidence with that.

Q. So then how do the oysters sense the crabs?

A. They smell the crab urine.

Q. I understand using the oysters and how you were saying that blue crabs move all the time, so in a perfect world they are not necessarily always paired together. Then that leads me to wonder why blue crabs? Because I am sure that, that is not the only predator for the oysters. Was it just the easiest predator that you could simulate with this experiment?

A. So I kind of inherited blue crabs in general. People might have done something with fish, but I just kind of spring boarded on the study when I was designing this. I have also used mud crabs… but they didn’t respond to them even though they had before..

Q. But that is kind of nice to know because in real science it is all trial and error. You know, you are repeating these experiments that you have done before and if blue crabs is what you use because mud crabs didn’t work then that makes sense. And I feel like that is one of the things as a student, I didn’t necessarily love science, I mean I didn’t hate it but I definitely didn’t love it because it always seemed like this routine and procedures that are to the tee and you get this one answer if you do all of these things and that’s not true. So I actually love hearing that this didn’t work or that fell through and so we are doing this now.. Because that’s true science to me.

A.Laughs. And that’s usually where you actually figure out interesting things. Like it is not stuff that you anticipated getting.

Q. I noticed that when I asked a little bit about why you use the Blue Crabs part of it was that it was something that others have used, so then you are repeating this experiment that was originally started up by someone else?

A. Yeah, it has been altered. The original study was just looking blue crabs around, mud crabs around, nothing around. And they found that Mud Crabs definitely induce a response but the Blue Crabs induce a stronger response and so from there we started asking these more specific questions about how that changes under ecological circumstances.

Q. So working with ETEAMS, you actually mentioned that Lee is a writer on the grant, so can you talk a little bit about how you have partnered with ETEAMS and why. Was it more of a personal choice to work with teachers?

A. So basically when they were writing the grant, they had funding to pay a graduate student to do some of the work on it and Lee put my name forward since he was on it. It had never really occurred to me to consider it – it wasn’t necessarily something I was seeking out but Lee was telling me about it and I was like “that sounds really cool.”

Q. So how do you feel about it? Being so involved with science, you know I can tell it is a passion of yours, how does it feel to be involved with people that are going to be teaching this?

A. This really kind of sparked a passion for me for outreach. I really like working with kids because I was always like, “I don’t want to teach” and I don’t. I never want to like always be in the classroom setting but I really love doing outreach with the kids. Like going to the classroom and taking the crabs in there and they are all like, “oh my god!” Laughs. But I really do love how excited they all get about it… So I definitely have really enjoyed doing this and want to do more of this kind of stuff.


Azita Pardom


The purpose of my research project was to test the effects of prey (oyster seed) growth and defense responses when faced with predation. We were specifically testing for changes in shell growth, weight and strength. For success in this project, we paired the oyster seeds with the local Blue Crab which are top predators native to the Corpus Christi estuaries.


Corpus Christi,Texas



So what is the big deal you may ask? Well research about marine life, and specifically prey and predator interactions, allows scientists to understand the activity, life span, and characteristics of many underwater communities. Without the possibility of lab simulations such as the one in this project, we would not be able to lay down a foundation for further research regarding different relationships present in the animal kingdom – which widely includes humans. Still confused? Think about how brain neurological research can stem from the available studies on snail neurology because of common characteristics. Simply, we use available research opportunities in different animal communities to makes sense of the world we live in. Welcome to the world of science!

Now let’s switch gears for a minute. All this talk about the impact of science leads me to believe that we must begin setting a foundation for engagement and exploration early on in the primary and middle school levels. Our project itself could not have been successful without the careful understanding of the control and experimental groups in our projects. Without these we could not have tested our hypothesis and safely say that the Blue Crab were in fact responsible for obvious changes in the oyster seed growth. Eliminating the possibility other factors being held responsible, is highly important and is a major concept discussed in the middle school educational system. We want our students to be knowledgeable and prepared to properly execute and repeat scientific experiment.

Methods & Procedures

image2 - Copy (2)The first thing we did was set up a total of 18 tanks with a total of 9 predators and 9 control tanks with no predators. In order for the tanks to be sufficient for both the oyster and blue crab survival, we created three large water barrels, each with a salinity of measure of 20 units as well as bottle cap dose of Kordon NovaAqua Plus water conditioner. This is intended to add a protective layer of skin slime and detoxify chlorine and chloramines levels while still removing toxic metals from the city water system. These three barrels of water were used to fill up the tanks as needed throughout the duration of our experiment.

We then placed 9 crabs in each of the labeled predator tanks for about a week before we added the oyster seeds. The time allowed for us to decide exactly how we were going to simulate the presence of the predators without actually allowing the crabs to get ahold of the seeds. Remember – we want live oysters at the end of the project in order to measure their growth responses. In science, advice is key! In collaboration with fellow scientists, it was decided that the best way to simulate full presence would be to bind together two drain strainers with fishing line in order to hold the seeds together in the tanks. This was very innovative in that it still allowed water and food for the oysters to pass through the strains for survival while still creating a barrier of protection from the crabs.

Oy 2

In total, we created 54 balls with 108 strainers and managed to put a total of 15 oyster seeds in each. The balls were then divided up and labeled between 6 different colored zip ties. These colors each represent the different amounts of exposure to the predators.

  • White (Control) – 0 hours of exposure.

  • Pink – 24 hours of exposure a week.

  • Orange – 72 hours of exposure late in the week.

  • Yellow – 72 hours, constant early in the week.

  • Blue – 72 hours, broken throughout the week.

  • Black – 168 hours.

Depending on the exposure amounts listed above, the balls of oyster seeds were moved between the control tank with no crabs, to a tank with a Blue Crab predator.

Further information: water changes to keep the water quality clean and clear happened once a week on Mondays so that there was no interference with crab feeding prior to and oyster feeding after water changes. For testing procedures to come, please see discussion and conclusion section.


Our observations thus far have only included ones that allow us to safely say that the oyster seeds and Blue Crabs are still alive. It is important to mention that this project has been revised from previous years by using oysters seeds instead of oyster spat which are larger. With that being said, the changes in size and shell response are minimal and not obvious to the naked eye. In the past project however, the responses and changes in size were in fact obvious to researchers because the oysters exposed to predators were growing at an alarming rate. We are hoping at some point to see these obvious changes in the current experiment. However, because we are rearing very young oyster seeds and not spat, it will be a while before seeing any truly measurable observations.



As I mentioned previously, the rearing of oyster seeds is a very meticulous and time consuming process. The project itself ran a few weeks late and so far has a projected four month wait until the oyster seeds have grown large enough to be tested. At this time the graduate student, Avery Scherer, will measure the strength of the oysters by essentially applying pressure to the shells with a device called a penetrometer that measures how much force is needing to be exerted before the shell breaks.  She will  then proceed to measure shell weight by first removing soft tissue and drying them in order to remove the excess water weight. Finally, the diameter of the shells will be measured to see if there is any correlation at all to the strength and weight. However, it is important to mention that the most reliable measurements for the experiment are the weight and strength. Past studies performed on oyster spat show that we can expect an obvious change in oyster growth responses when paired with predators for long periods of time. Simply put we are expecting the larger growth shells, with greater weight and strength to be consistent with those exposed to the predators for long periods of time.

Lesson Plan

5E Lesson Plan:

Essential Questions:

  • How can we show the proper use of the scientific method for an actual audience?
  • What tools will we need and what variables can we change in our experiment?
  • How can we analyze data to form conclusions?
  • How can we present our data to an audience?


3.2.B Collect data by observing and measuring using the metric system and recognize differences between observed and measured data.

3.3.A In all fields of science, analyze, evaluate, and critique scientific explanations by using empirical evidence, logical reasoning, and experimental and observational testing, including examining all sides of scientific evidence of those scientific explanations, so as to encourage critical thinking by the student.

Critical Thinking: Interpret and evaluate information to solve real problems with conventional and unconventional approaches.


Scientific Method, hypothesis, variables, inquiry, conclusion

Engage/Hook (One Day):

Option 1: Kostoryz (your campus) Mad Scientists,

Have you ever thought about how you use the Scientific Method in your everyday life? Everyday you encounter problems that you may not know the answer to and to find your answer you need a plan. Today you will meet a real marine biologist. Her name is Avery. Find out how she uses the scientific method to do research and how you can use it to do research to your own questions.

On day one the 3rd grade students will meet with Ms. Avery Scherer, a real marine biologist who works every with the crabs and oyster in the above research project. She will talk to the students about her work and the importance of following specific routines and procedures in her lab. She will introduce the a crab or two to the students in order to engage them about being real scientists. Students are encouraged to ask her questions. She will then provide the students with their own challenge brief which includes following routines and procedures for a Gummy Bear experiment. She will then challenge the students to change the experiment the next time around by choosing different solutions.

Option 2: Animated Science Episode 1: The Scientific Method

Show students the episode about the scientific method. Be sure to discuss with students what they notice in each of the scientific method stages so that it is clear what is expected of them when conduction their own experiment.

Explore  (Two-Three Days)

The students will work in groups in order to complete the Gummy Bear experiment (student worksheet and directions for the experiment can be found on teachers pay teacher). The experiment calls for the students to make predictions about what would happen to gummy bears when placed in water overnight. Students will complete the experiment  and record changes the next day.

The students will record observations on the gummy bear now that it has been left in water overnight. Students will “buzz” (turn and talk) to their group members about why they believed the changes happened in the way that it did. They will then decide as a group how they can change the water variable. For example, the students may choose to repeat the experiment using soda, hot water, juice etc.

Explain (One Day):

The students will create a venn diagram comparing the first Gummy Bear experiment to the second one, recording observations and verbally detailing the process of completing both experiments. The students are expected to record explanations their classroom iPad and share the video with another group.

  • What were some differences and similarities that you noticed in the two experiments?
  • Why do you think you saw these types of changes?
  • What is the importance of repeating your experiment and changing the solution?
  • What was the importance of working together collaboratively?

Elaborate/Evaluate (Two-Three Weeks):

The students will get the opportunity to share their experiments and videos with Avery when she returns to our campus. This is to practice having an authentic audience. The students will then take the time to use what they have learned in order to recreate an original science project following the same scientific method we used as a class on the gummy bear experiment. Their final evaluation will be judge during their science fair in October. It is important to note that our school science fair packet includes specific guidelines for students to follow which includes the scientific method and each of its components.

Note: If your school does not participate in a science fair with an authentic audience you may ask permission to partner up with another class (maybe an upper grade level) in order to complete the evaluation process. If not, you may instead choose to create your own student rubric and evaluate the original projects on your own.