Fish Lab & Marine Aquaria
Sea cucumber viewed from underneath, as it feeds on the glass in our marine aquarium
Previously, we had noticed a large population of silverside bait fish living in the shallow lagoon outside our Marine Discovery Centre, which persisted for a total of 3 weeks. The accumulated organic faecal matter in the vicinity of our water inlet pipe was stirred up by rough weather, creating turbid waters (characterised by high Reynolds numbers). These combined factors likely resulted in the influx of bacteria that caused our aquarium fish to become infected.
After treatment and reassurance that the infestation was eliminated, new fish species and marine invertebrates were introduced to the tank from collection sites around Landaa. The year then closed with a wide variety and high number of marine animals: a total of 130 individuals from 28 species across 16 families.
2019 was a successful year for the rearing of Aurelia aurita jellyfish in our new Kreisel aquarium at Landaa Giraavaru. We started with 50 tiny ephyrae (2mm diameter) and finished the year with 27 adult medusae with diameters ranging from 10-25cm. The survival rate to adulthood was a successful 54%, and life within our dedicated Kreisel tank could yield a 2-year lifespan (double that of wild individuals).
- April-July focused on the growth of the ephyrae to juvenile medusae.
- August-September was crucial for acclimating the juveniles to warmer waters.
- September-November focused on duplicating and growing substantial numbers of jellyfish polyps and juvenile strobila in the Fish Lab.
- December marked the commencement of strobilation conditioning, currently on-going.
At the close of the year, we have 600+ juvenile scyphistoma in our Fish Lab, with around 300 in conditioning for strobilation. We plan to develop a robust protocol for successful turnover and continuity in jellyfish stock for 2020 onwards.
2019 was a low year for both our Clark’s (Amphiprion clarkii) and Maldivian (A. nigripes) anemone fish breeding, with spawning events becoming less regular and more variable in batch size. We hope to improve things in 2020.
Our live food production of algae, rotifers and artemia continues successfully, with quantities refined throughout the year to meet the needs of the consumers in the Fish Lab and main aquarium. Artemia production was highest in April-May (to supplement the growth of the new jellyfish) whilst algae production fluctuated throughout the year, as required.
New arrivals to the Fish Lab in December included some tiny larvae, found amongst coral polyps from a donor colony. After microscopic observation, we determined these to be zoeaes; free-swimming planktonic individuals in the larval stage of decapod crustaceans (10-appendages). With their large cephalothoraxes, conspicuous eyes, and fringed antennae and mouthparts, we think they are crab zoeaes specifically.
At the beginning of December, a water-inflow problem resulted in a lack of oxygen in the aquarium. This caused the death of one of the Maldivian anemonefish (Amphiprion nigripes) and affected the behaviours of other species, particularly the blue-green chromis (Chromis viridis) and the blacksaddled toby (Canthigaster valentine).
On our mini-coral frame, the Acropora tenuis, A. digitifera and A. hyacinthus fragments continue to encrust over the onto the bars, but several newer fragments have bleached or died.
Small Aquarium Two
We recently removed all the fish from aquarium two for cleaning, and then reassembled the rock and hard structure. New additions include a large specimen of hard coral (Favites complanate), a smaller encrusting colony (Porites sp.) and two zooanthid colonies. Our small purple-tip anemone was divided, and a new mini coral frame added (with A. digitifera and A. tenuis), to compare the encrusting growth rates.
Regeneration of Linckia multifora sea stars
- SS1 (large specimen) showed an average decrease in arm length of 1mm, perhaps caused by the reduced water flow decreasing the available food.
- SS2 (automised arm) has disappeared somewhere in the tank!
- SS3 (large specimen) showed an average arm growth of 1.2mm.
- SS4 (automised arm) is now showing promising development of new arms (currently 2-4mm in length) although the parent arm has decreased by 1mm, likely as a result of the increased energy demand from the new arms.
Education & Awareness
Marine conservation for children as part of our Junior Marine Savers activities
Our 6 students from the Four Seasons Apprenticeship program have successfully completed their placement with us, amounting to a total of 60 hours of lectures and practical work covering our marine conservation programs. This culminated during December with the second semester exam and final presentations.
The students were assigned a selection of scientific articles to review, prior to presenting their findings to our panel. Their articles were focused on studies made in the Maldives on areas such as sea turtle by-catch, manta ray seasonal distribution, coral reef restoration, reef fish and shark conservation. All the students did a great job in answering all the tricky questions posed by our panel of marine experts!
Public Lecture at Villa College
“Malé Island: Formation and Future Through Geological Times”
On 11 December, we were pleased to attend a lecture at Villa College in Malé, presented by visiting speaker Professor Andre Droxler of Rice University (Houston, Texas, USA).
The Professor explained how Maldivian coral atolls were formed, and detailed how Malé rests on the edge of an old volcano that has sunk over time, with vast layers of volcanic rock and coral skeletal substrate pushing upwards along the edge of the volcano’s mouth, so that just sandy islands and coral reefs poke above the surface.
Professor Droxler is also running a virtual-reality project that uses aerial drone footage of coral reefs to open up coral reef geology to students and a wider audience.
For further scientific reading, please refer to Professor Droxler’s extensive published research.
In December, we were pleased to welcome students on their annual visit from Flinders University (Adelaide, South Australia). The 22 students spent an afternoon with Marine Savers at Landaa Giraavaru, learning about marine conservation and our post-graduate internship program. Professor Karen Burke Da Silva has been following our clownfish breeding program for several years; she is Director of the ‘Saving Nemo’ program in Australia, and we welcome her advice and support for our own clownfish hatchery.
REEFSCAPERS Coral Propagation Program
At Kuda Huraa, the Reefscapers coral propagation program experienced both highs and lows throughout 2019. Prior to April, the program was meeting its sustainability goal, with most coral fragments being successfully harvested directly from our frames (rather than the natural reef). Then in April, the seasonally elevated ocean temperatures combined with problems of sedimentation and disease proceeded to wipe out 60-70% of the corals at every site (except for the House Reef).
Following this bleaching event, the rest of the year has largely been spent recycling, remapping, cleaning, and re-transplanting frames.
- The Water Villas site is now completely re-transplanted and monitored.
- The Starfish is 70% complete and the Channel is 60% complete.
- The House Reef has been re-transplanted but requires monitoring.
- The Channel remains the most challenging site; many of the frames are buried or missing tags, with sedimentation and algae accumulation impacting our efforts to restore the frames there.
- Metal wire is now the preferred method to attach the frame ID tags.
- Polyester resin was found to be better than epoxy resin for recoating frames with sand.
ICRS 2020 is the primary international conference on coral reef science, conservation and management, bringing together leading scientists, early career researchers, conservationists, ocean experts, policy makers, managers and the public.
This symposium will be the key event to develop science-based solutions addressing the present and future challenges of coral reefs. The five-day program will present the latest scientific findings and ideas, and provide a platform to build the essential bridges between coral reef science, conservation, politics, management and the public.
We hope to attend the symposium with our submissions “Using deep-learning models to monitor coral colonies on a large scale”, and “Scaling up: what lessons can we learn across larger scales for understanding coral reefs?”
- Louise Sabadel (January to April) conducted photo-analysis on our coral frame database, to compare two methods for protecting corals against bleaching events: (1) providing shade, and (2) relocating to greater depths. Louise showed that both these techniques can be effective in providing greater resilience to future bleaching events.
- Olivia Beatty (June to August) studied the effects that fragment size has on coral health, with a practical experiment using 6 coral frames. Subsequent analysis revealed a statistically significant difference, and Olivia was able to conclude that larger fragments have more resilience to negative environmental factors. Follow-up studies are required, to increase the sample size and include extra species.
- Iris Van Djik (October to January 2020) worked on a coral sexual-reproduction pilot study, looking at spawning in an aquarium environment. Coral planulae were observed to successfully settle on substrate, and primary polyps started feeding on rotifers after 7 days, followed by some budding.
Work is continuing on our autonomous reef-monitoring catamaran. In order to diversify the AI training photographs, we have been providing the AI software model with new monitoring sets from different environmental conditions. The current version of the artificial neural network is now trained on 605 monitoring pictures, a total of 9,442 individual fragments. To obtain these results, we had to train the model for more than 3 million seconds… which equates to approximately 35 days!
We are also developing a deep-learning AI method (similar to fragment detection) to recognise the bars on our frames, which will be essential in visually complex environments, for instance when the ground is covered with rubble.
Sea Turtle Conservation
At Kuda Huraa, we are closing the year with 6 Green turtles (Chelonia mydas) and 6 Hawksbills (Eretmochelys imbricata) in our hatchling rehabilitation program (see the corkboard, below).
- During 2018, we received 3 full clutches of turtle eggs and several single hatchlings.
- During 2019, we had fewer hatchling admissions, and fewer nests were reported to us. This could be related to nesting behaviours, as sea turtles nest every 2-3 years (with 1 to 9 clutches per season). The mortality with our hatchlings was higher this year, as we now only accept sick hatchlings into the program.
A third overseas aquarium has shown interest in adopting one of our unreleasable sea turtles, as part of our ‘Flying Turtle’ program, and we are preparing the preliminary documentation. The process for rehoming a sea turtle is a long administrative process, filling in official forms and seeking approval from various governmental agencies.
Currently, we are awaiting approval from the Maldives Environmental Protection Agency (EPA) to send blood samples overseas for analysis. We hope to be able to send two of our turtles overseas later this year.
Olive Ridley turtle ‘Luchi‘ rescued from ghost netting (January 2020)
At the end of December, we have 7 Olive Ridley turtles (Lepidochelys olivacea) plus 1 Hawksbill (Eretmochelys imbricata) in our care at Kuda Huraa (see the corkboard, below). Throughout 2019, we recorded a total of 42 turtle strandings.
- 3 turtles were released immediately, after being freed from ghost nets;
- 6 turtles were found dead, entangled in ghost netting and marine debris;
- 33 turtles arrived at our Centre for rehabilitation, many suffering from buoyancy syndrome, with lacerations and amputated flippers.
At Landaa Giraavaru, we admitted 21 sea turtles to our Rehabilitation Centre in 2019, with 6 successful releases, 6 mortalities and 6 transfers (to either Kuda Huraa or the Olive Ridley Project).
We currently have 8 sea turtles in our care (see the corkboard, below), following the successful release of Nadia on 28 December.
In early 2020, we hope to employ a marine veterinarian (vacancies), to perform emergency surgical procedures and expand our facilities.
Turtle photographs are kindly sent to us from members of the public, fellow marine biologists and dive centres stationed at other resorts around the Maldives. Submissions consist of close-up photographs of the turtle facial profile, enabling us to outline the unique pattern of scales (scutes) that act like a human fingerprint.
During December, we received a total of 46 sets of photo submissions (THANK YOU!)
Our national turtle ID database of uniquely identified individuals now stands at: 1207 Hawksbills, 210 Greens and 56 Olive Ridleys.
Spotted a turtle? Share your photos
PHOTO: Hawksbill turtle EI1167
Further News & Updates
You might also be interested in our Dolphin ID Project, and our Sea Turtle Enclosure out in the lagoon at Landaa.
Looking for details of our coral propagation programme ?
Head over to our Reefscapers 2019 Diary for all the latest updates.
You can sponsor your own dedicated Coral Frame, and then see how it grows in the future by viewing the photo updates every 6 months, as part of our Coral Frame Collection.
Photos: (1) Reefscapers coral frames at Kuda Huraa water villas.
(2) Junior Marine Savers learn the importance of corals.