Fish Lab & Aquaria -Marine Life in the Maldives

Fish Lab

Down in our Fish Lab, we are continuing to revise our protocols and methodologies. Algae production is strong, and now requires changing every 4-5 days; Rotifers have stabilised and the numbers are growing. The strobilation of the new jelly fish has begun, with a higher-than-expected yield from a single tile.

Plankton Production

Our revised algae production implemented last month has proven successful, and we can now maintain 4 x 100L and 4 x 20L buckets over the month. This has made it incredibly easy to maintain our Rotifer safety net.

With the arrival of our new Rotifer feed, we have been experimenting and settled on a feed ratio of 0.63ml/million Rotifers (as recommended for a daily 20% harvest rate). The numbers have risen steadily and consistently, and there has been little build-up of waste, therefore avoiding the cycle of quick growth/increased ciliates/population crash. This also allows us to feed the Rotifers accurately and measurably in a way that can be easily replicated (new to our Fish Lab), with yeast quantities estimated day by day.

The Artemia have been more challenging. We now create a safety net of frozen Artemia every 2-3 days to ensure enough food should there be any issue with aeration overnight. This method also allows us to track our usage (448g cysts/tin gives 224 ‘portions’). We will begin counting on a bidaily basis to calculate average number of Artemia produced, and start comparing total number of Artemia as opposed to Artemia/ml.
After a few incidents of both explainable and unexplainable drops in hatching success, we have revised our methods to improve success rates, to more easily identify any issues:

Old method:

• Batch partial-hydration of cysts + remove unhatched
• Estimate and hydrate a suitable amount of partially hydrated cysts daily for up to 24hrs, to provide enough food for the following day
• Separate hatched from unhatched and provide the feed as required

Revised method (simple, more measurable, fewer unhatched cysts):

• Hydrate 2g cysts in 2L salt water daily (additional 2g to provide a tray of frozen feed as required)
• 24hrs later, separate the hatched from the unhatched
• Feed as required

Zooplankton Study

While we await the equipment delivery, we have created a simple database to use for data collection. We have also been collating a library of scientific papers on plankton (Indian Ocean, climate change, etc).

We held a video call with zooplankton expert, Anthony Richardson, (CSIRO Australia), discussing formalin concentrations (with safe handling/disposal), and the actual identification of the zooplankton (majority will be copepods). We plan to purchase:

• Flow meter (vital for getting volume measurements and adding validity to our data)
• Small oven (to determine biomass of samples, widening our scope of applications at a low upfront cost)
• Scientific weighing scales (to weigh dried samples)

This is a great opportunity to be the first long-standing plankton study in the Maldives, with potential for future growth and interaction both locally and globally.

Small Aquarium One

• Mini coral frame – 4 dead fragments removed; 16 new fragments added (Acropora species).
• Maldivian clownfish (Amphiprion nigripes) breeding pair – no eggs this month.

Small Aquarium Two

• Mini coral frame – 5 dead fragments removed; 9 new fragments added (Acropora tenuis).
• Clark’s anemonefish (Amphiprion clarkia) – 3 batches of eggs.

Linckia multifora sea stars

• SS3 (large specimen) – growth in all arms.
• SS4 (new Jan 21) – growing steadily (especially shorter arms).

from: life cycle of scyphozoan jellyfishes