Fish Lab - Maldivian clownfish

Clown Fish Breeding Programme

In aquaculture, the success of rearing is highly dependent on the water quality. By feeding the larvae with live prey, the consumption of oxygen in the tank will be multiplied by two and the waste created by the animals will also affect the water oxygenation by promoting bacterial growth. We have started to double the water changes of the larvae tanks (to 80% of the water volume daily) and we also use the inlet water flow to maintain constant water renewal. This process will also renew the old nutritionally poor Rotifers and Artemia.

Production of algae has increased, due to the use of two new French strains alongside vitamin B12 supplementation, and we are also using some new large 100L outdoor tanks. The extra algae were used to enrich the Artemia, the main food for the seahorses, whereas Rotifers have been down due to variations in the washing process. We plan to restart Rotifer enrichment for clownfish food.

We have stopped using algae for any enrichment during the larvae rearing process, and changed to the S-presso INVE brand enrichment. The results are satisfying, giving reduced maintenance and cleaning of the rearing tanks. Our most successful rearing experiment so far is E90717:

  • larvae collected by the Syphon method;
  • AC off at night (to maintain 28°C); low (50%) lighting on day 1;
  • no algae; increased concentration of rotifer enrichment, with monitoring.
  • daily water changes via the inlet water-flow pipes.

Our new intern, Jean Gabriel, is now running some Clownfish breeding experiments. The main objective of his project is to improve the survival rate of the larvae during the first stages of their life:

  • Improve the quality of the eggs and larvae yolk sacs by modifying the parental food composition (addition of fish eggs and mussels) and increasing the feeding frequency (from 3 to 5 times per day).
  • Promote the survival rate of the larvae and their growth, by feeding with different rotifer enrichments and by alternating the light period.

Click to enlarge
Clownfish breeding results October 2017 (above)
Clownfish breeding experiments August-September 2017 (left)

Clownfish Release Project

Our clownfish release project has been integrated into the Four Seasons Apprenticeship Programme. Four groups of students released the captive-bred fish and their home anemone under different premises. This project enables the apprentices to learn how to conduct a scientific study and for us to collect data regarding this activity. They had to elaborate a protocol of release that we can replicate, and which will give the best chance of survival for the animals. Each set of release plans included:

  • A fish training section (we fed them less and put in contact with their home anemone).
  • An evaluation of the suitable location (depth, current, luminosity…).
  • A biodiversity investigation on site (search for predators).
  • A monitoring schedule (collecting data).
  • Final presentation (introduction, data analysis, conclusion).

In total we released 12 clownfish and 4 anemones, but unfortunately none of these experiments were successful in the long-term. The maximum time in the wild was 4 weeks (wedding pavilion team); all the others were victims of high predation or their host anemone moved from the original area.

In science there are no bad results, as we can now improve our release protocol to avoid repeating the same mistakes. We plan to release smaller fish and bigger host anemones, to give the fish more hiding places against predators and more time for growth and adaptation to the natural environment. We also plan to install a protective cage during the first weeks of the release, to temporarily reduce the risk of predation to help the clownfish and the anemone to adapt to their new home.

Additional lessons learned:

  • The clownfish remained in good health and could find food by themselves.
  • The anemones were healthy even in shaded sites (under the wedding pavilion).
  • The stone arena created to break the current attracted predators and created hiding places for them.
  • The House Reef area is patrolled by hungry wild groupers that eat clownfish!
  • We observed the natural recruitment of some wild juvenile clownfish to our anemones (when sited close to a wild inhabited anemone).
Grouper predation on wild anemone

Grouper predation on wild anemone

Recruitment of Amphiprion nigripes and Dacyllus trimaculatus

Recruitment of Amphiprion nigripes and Dacyllus trimaculatus

Parley Plastics Takeover

On 16 October, the Marine Discovery Centre hosted a Parley Takeover in Café Umarbe, the staff canteen. Parley is a company that repurposes plastics into high fashion clothing items. Their goal is to intercept these plastics before they enter the sea and promote avoiding using plastics in the first place both in the Maldives and globally.

In order to increase awareness regarding plastic use and the correct use of the Parley bins, we planned a couple of activities for the event. Firstly, we set up a table to display the types of plastics that can be put into the bins on one side of the table, and items that cannot be put into the bin on the other. This was so people would have a clear idea of what can and cannot be placed into the bins.

Secondly, our corn hole game was a huge success! A player would answer a question about ocean plastics, which gave them three attempts at the beanbag game, with each successful hole-in-one awarded a prize-draw entry.

With the help of the Recreation team, we also created decorations and posters, and even prepared some themed foods! It was a successful combination of fun activities and new menu items, with some hard-hitting environmental information.

Sea Turtle Morpho-Evolution Project

The purpose of our new Sea Turtle Morpho-Evolution Project is to record the growth of the hatchlings on a weekly basis, from the moment they are accepted into our r centre up to their release. Twice a week, close-up pictures of the sides of the head and the carapace are taken to record the evolution or transformation of the scales and scutes during growth, and to assess how they change over time.

A stand for a DSLR camera was specially designed and attached to a plexiglass sheet with a measuring tape glued over it, so that we can place the turtle at the same spot and distance every time, giving us the length measurement of each individual throughout the year.

At the end of the data collection period, normally after 15 to 18 months, the photograph series obtained will be uploaded in a program called “Photomorph”, which basically morphs one picture into the next one, creating a video that will display how the scales and scutes evolve with time. This should reveal the development stage at which the scales no longer change significantly, so they can be used to identify the turtles in future wild encounters.

Turtle hatchling head start Marine Savers Maldives

Maldivian Sea Turtle Identification Programme

During the last few months, we have received over 100 quality submissions to our national turtle identification programme, mostly via our Facebook group. From these photographs, we have been able to identify many new Hawksbills and several new Green turtles from around the Maldives, and we have added further re-sightings of existing turtles in the database. This takes our total number of uniquely identified Hawksbills to 1006 and Greens to 149 individuals.

Do you have any photographs of Maldivian sea turtles ? We’d love to see them ! Join the Facebook group and if your turtle is new to us, you can give it a name and receive a ‘certificate’ ! 🙂

Newly identified Hawksbill turtle [#EI1000] sighted and photographed in North Malé Atoll, Maldives

Newly identified Hawksbill turtle [#EI1000] sighted and photographed in North Malé Atoll, Maldives

Maldivian Turtle ID Project - Marine Savers Maldives - Facebook photo submissions

Photo submissions via our Facebook group

Turtle hatchling head start Marine Savers Maldives
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