The transcript details a process at UC Davis Bodega Marine Laboratory involving the settlement and early cultivation of European flat oyster larvae. It describes steps like emptying culture tanks, preparing downwellers with phytoplankton, aeration, and substrate, and ensuring proper concentration and health of larvae before transferring them to grow further until they become oyster spat, to be moved to a FLUPSY system.

How to Settle European Flat Oyster Larvae: A Step-by-Step Guide

I recently received a call from Joe, informing me that it was time to settle the European Flat Oyster larvae. European flat oysters, also known as Belon, are native to Europe and closely related to the Olympia oyster. Without wasting any time, I headed to the UC Davis Bodega Marine Laboratory in Bodega Bay, California, to begin the process.

The Journey to the Oyster Hatchery

Upon arriving at the Bodega Marine Laboratory, we rushed inside to the oyster hatchery. While I wish I could have given you a tour of the lab and shown you the impressive rockfish aquarium, we had no time to waste as Joe was already starting to empty the tank of oyster larvae. We arrived just in time.

Observing the Oyster Larvae

As we shone a light into the culture tank, we could see millions of larvae swimming around. We knew they were ready when the larvae began settling to the bottom of the tank and started probing the surface with their foot, looking for a substrate to attach to.

Preparing the Downwellers

While Joe was busy emptying the tanks, we needed to prepare the downwellers and fill our sumps with phytoplankton. If you have an oyster hatchery, you must be adept at farming microalgae to feed your oysters. Once our buckets were filled, Sam ensured there was enough food in each of the downwellers.

Ensuring Optimal Conditions

We also needed to ensure there was plenty of oxygen in the downweller. The aeration helps mix the microalgae and keep it in suspension. A downweller is designed for water to flow down through the system, usually through a sieve. In this case, the oyster larvae will need a substrate to attach to, and we used various sizes of crushed shell, specifically a fine powdered shell. Each grain of sand will eventually support a single oyster larva.

Avoiding Air Pockets

Before adding the larvae, Joe checked to ensure there were no air pockets in the system, as these could be lethal. Once we were ready, we added the powdered oyster shell to the downwellers.

Emptying the Culture Tanks

Our culture tanks were close to emptying, and all the dark specks visible were baby oysters. After emptying the culture tanks, Joe made sure all the detritus and debris were pushed through the 150-micron sieve. This process is crucial for ensuring a clean sample before adding the larvae to the downweller.

Calculating Larvae Concentrations

Once the larvae were added to the bucket with a set amount of water, we calculated the concentration to ensure the right amount of larvae were put into each downweller. To determine the concentration of oyster larvae, we used a graduated cylinder as a plunger to mix our sample. After taking multiple measurements and recording the concentration under a microscope, we took an average.

Selecting the Best Larvae

We had an abundance of oyster larvae, so we selected only the largest and healthiest larvae, removing anything less than 230 microns. We repeated the process, filtering the sieve one last time, adding water, and determining the final concentration.

Filling the Downwellers

Finally, the moment arrived to fill the system. You might be surprised to learn that there were 50,000 baby oysters in that beaker! Joe and Sam systematically filled each of the downwellers and conducted one last check to ensure there were no large air bubbles. The larvae would remain in the oyster hatchery until they reached two to three millimeters, at which point they are referred to as oyster spat. They are then transferred into a FLUPSY.

To follow the journey of these oyster larvae into the field and learn more about what a FLUPSY is, be sure to watch our next video!

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By following these steps, you can successfully settle European Flat Oyster larvae and ensure their healthy growth in your oyster hatchery. Whether you’re an experienced farmer or a beginner, this guide will help you understand the process and achieve the best results.