Today Grace and I did an assessment of oyster survival and growth at Westcott Shellfish. This assessment is our fall time point. We will assess again in the spring.

Overview

We outplanted oysters at Westcott this past summer (June) after conducting sub-lethal stress hardening treatments (daily or weekly exposure to elevated temperatures; Efforts B and D).

More information on this project can be found in the GitHub repo and my past notebook posts.

Today our goal was to take images of oysters for size and survival measurements, download temperature loggers and maintain the cages.

Growth and survival assessment

The Westcott crew attached buoys to our cages and we picked them up on the barge today. We then removed the oysters from each cage using the following proceedure:

• Remove oysters from cage - oysters are kept in smaller mesh bags inside each of the rack cages.
• Manually measure length, width, and depth for a subset of oysters (n=10 per cage) including the largest and smallest oysters in the measurements. These will be used to generate a model to estimate oyster volume from length and width measurements only, because we will use the images to measure length and width of all other oysters.
• Record the number of any dead shells and discard dead shells.
• Take an image of all oysters in each cage. Include the original tag in the image (UW-SR#). Add a new purple cattle tag to the image, this tag will be added to each cage (#000). Include a scale bar in each image.
• Move all oysters back into their mesh bags. If mesh bags were too small or damaged, we moved them into new mesh bags.
• Attach cattle tag to interior of the mesh bag with the oysters. Add the old paper tag into the bag as well.
• Put the oysters back in the same cage and secure closed.
• After all oysters were imaged, the Westcott crew will put them back in the same location.

Size data, mortality, and notes regarding bags or cage condition were made in the notebook, see the link below for images to notebook pages.

Here is an example of images from today:

All images of oysters and notebook pages with size data are stored on GitHub.

Temperature loggers

We downloaded all five loggers today and left them in their original location. Each logger has used only 19% of memory, so we did not clear the memory and kept them deployed at their current settings.

Files were downloaded and added to GitHub here.

Loggers were left attached in their same cages, they were not fouled and did not need cleaning.

• Logger 22023393: UW-SR1
• Logger 22023396: UW-SR26
• Logger 22023401: UW-SR20
• Logger 22023405: UW-SR12
• Logger 22023412: UW-SR19

Here is the temperature data from the start of the outplanting process after downloading data today:

Next steps

We are now going to work on the following steps:

• Measure oyster size from images
• Count oysters in each cage for survival
• Run models to predict volume from length and width measurements from subset of manually measured oysters
• Analyze growth as percent growth from intial time point

We will assess outplants again in the spring.