Determining Growth Potential of the Eastern Oyster by Volumetric Comparison Utilizing Soda Bottle Upwellers

Progress report for FNE19-934

Project Type: Farmer
Funds awarded in 2019: $14,294.00
Projected End Date: 02/28/2022
Grant Recipient: Aquacultural Research Corporation
Region: Northeast
State: Massachusetts
Project Leader:
Cheryl James
Aquacultural Research Corporation
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Project Information

Summary:

The purpose of this project is to determine what population of oysters /soda bottle is ideal and what is practical. If we can demonstrate how many oyster juveniles we can successfully grow in a bottle nursery system then we can improve production by producing more oysters and occupying less space.

In ARC's 2019/2020 production season we ran several experiments. We found that we needed to develop a better system in determining the amount of algae we would feed the oysters. We will determine a new goal for an a.m. fluoro which is only used for the bottle nursery system. Therefore , in our 2021 production season we will do algae counts and fluoros and set an ideal  a.m. fluoro to aim for which will provide the animals with enough readily available food. If there is enough food in the sample coming out of the bottles there is more algae going into the bottles. If the animals have enough food around them to feed on, their growth rate will be higher.

In order to reduce splashing, we put a 1" i.d. elbow connected to a 7.5 " long, 1 " o.d. pvc pipe to the bottle outflow. We also set up a system with an elbow connected to tygon tubing in order to set the flow rates going through the bottles. 

In our 2019/2020 season we also tried 1" marbles with rubber around them which proved to be a problem. The rubber kept falling off of the marble leaving gaps for the oysters to escape. We therefore ran the bottle system with 1" marbles only. In 2021, we are going to try 1 3/8 " marbles a swell.

The food tank which is a holding tank for the algae worked very well. With tygon tubing connected to the tank we were able to pump the food into the system. A 1/4" barb/buna valve was put on the end of the tubing and flow rates were set daily. The food line was put on the left side of the tank where the seawater flow was going into the tank. the intake to the pump was just under the incoming food and seawater. Therefore, new seawater and algae moved through the bottles. The waste and used water came out the end of the trough next to the outflow. This is where we took out our samples.

Taking the elbow and tubing on and off of the outflow bottle unit is fairly easy to do and you can make your own flow meter with a graduated cylinder to be cost efficient.

Once we determine the ideal and practical densities of the oysters, an a.m. fluoro goal and bottle flows we will be able to create a protocol to run the system.

 

Project Objectives:

The goal of this project is to determine growth potential of the eastern oyster in soda bottle upwellers. We aim to determine what the ideal and practical densities are through running experiments with oysters at different densities. We will also need to look at food availability and temperature. Warmer temperatures and available food also affect growth rate. In, 2020 we ran numerous experiments at different densities and did not find a pattern. We will therefore be running more experiments and looking at a few other variables, available food and temperature.

Food availablility may be affected by the water flow going into each bottle unit fluidizing the oysters. In order to measure the amount of food in the  water a sample needs to be taken at the outflow of the tank. This will tell us how much remaining food there is after the water and algae has passed through the bottles. In 2019/2020 season we were using a TD 700 fluorometer to measure the amount of algae in the water. This machine measures the fluorescence of materials such as chlorophyll. We have created our own standard at the hatchery which tells us that one fluoro = 2,000 algae cells/ml.. Based on this information we can use our fluorometer to feed our animals a calculated goal of food. We did hit an obstacle which was a higher than expected fluoro reading in the samples. It was found that the fluorometer was reading other particles in the water due to turbulence created by the system. When the water flows through the bottles, waste and particles in the water are getting agitated so they are detected by the fluorometer. We only want a reading on algae cells present in the water column. In the hatchery we are able to feed juveniles in downwellers without the waste and particles in the water column. The downward flow into the units which house the animals keeps the waste etc. on the bottom of the tank making it possible for us to get a water sample which tells us how much algae there is. We can then calculate how many algae cells there are/ml.. Because of this obstacle, we are going to do algae counts of the samples taken in order to accurately determine how much food there is in the water column after it has passed through the bottles.

We will also be adjusting the flow rate through the bottle by eye fluidizing the oysters to ensure there is enough fluidization and then taking a flow rate. This information will let us know approximate flows that different size oysters at different volumes will require and how much the flow rate affects the growth. The temperature will also be documented so that we can compare growth rates at different temperatures.

 

Introduction:

Marine aquaculture is on the rise and has provided the United States with a source of seafood as well as employment opportunities. If the soda bottle upweller can positively affect production in shellfish hatcheries by housing more animals in the same footprint, it would be well worth its promotion.

The purpose of this project is to build a coke bottle upweller system and determine what population density/bottle is ideal and practical for growth. Through analyzing density , food availability and temperature a protocol can be designed . If we can increase oyster production we will have more seed for local fishermen.

Description of farm operation:

Aquacultural Research Corporation was started in 1960 and is a shellfish hatchery , as well as a farm operation. We spawn primarily oysters and quahogs and grow them in our hatchery and nurseries. We then sell millions of seed to fishermen. The seed is then grown out for market.

Cooperators

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Research

Materials and methods:

The research portion of this project has been delayed due to the availability of the ideal size of oyster seed. Research will resume in the spring when production of oysters resumes.

However, before deployment, we discovered several designs flaws with the coke bottle system. The trough for the water outflow was too small but was remedied with a larger diameter pipe. There were issues with the mechanism that keeps oysters from draining out. Through experimentation, we found the balance of correct density and materials which would minimize loss of oyster seed.

In the construction of the coke bottle upweller system some challenges occurred.  To start, the three inch half pipe volume was inadequate to support the volume of water flowing out of the 20 bottle units.  To solve this a new three inch pipe was cut, removing a quarter of it leaving a larger volume to support the water flowing from the 20 bottle units.  After the trough was fixed to collect the discharge from the bottle, larger oysters (R1.5/2mm) were placed in the bottles to run the system.  Larger oysters were used, since we had a failed oyster spawn and were unable to use small oysters (less than 1mm).  While testing with the larger oysters we determined that the acrylic balls, that are used to keep the water and oysters in the bottle when water flow is shut off, were less dense than the oysters. Therefore, the acrylic balls did not keep the oysters from draining out of the bottles.  To solve this problem denser glass marbles were used to keep the oysters in.  Although this worked to keep the oysters in, the marble crushed the oysters and therefore had to be modified.  Experiments were conducted and it was concluded that covering the marble with a rubber elastic would prevent the marble from crushing the oysters. The modified glass marbles were also successful in keeping the oysters in the bottle when water flow is off.  Using the modifications, we will now be able to utilize the system to collect data to determine the most practical density. Once this is accomplished, it will result in an increase in production without compromising the health or growth of the animals.  This information would benefit individuals that are interested in finding a more efficient way to grow juvenile oysters.

Based on the changes we made to the design of the system, we have minimized the risk of losing oysters when they become available to be tested in the system.

Participation Summary
7 Farmers participating in research

Learning Outcomes

Key areas in which farmers reported changes in knowledge, attitude, skills and/or awareness:

The staff of the hatchery has improved upon the original design and gained knowledge in how to operate the system. This is crucial to gather data when oyster seed becomes available.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.