Fish Lab

Clownfish Breeding Programme
Following major refurbishment of our facilities at Landaa Giraavaru, we restarted our clownfish rearing during January. We are feeding our breeding pairs with food enrichment (SELCO + prawns) to produce good quality eggs with plenty lipid reserve for the larval growth.
We have also started several experiments to research various environmental parameters:

  • Water temperatures (<26C is harmful) – heater adjusted to 28°C, and the air office conditioning is now turned off overnight.
  • Food – we enriched the rotifers with algae and ‘Selco’; results seem promising.
  • Collection of larvae (newly hatched fish) – the syphon method may be damaging, so we made a new light trap which is useful for small batches of larvae.
  • Light – we have increased light levels to allow the larvae to hunt better for food.
  • Bacteria – we clean all equipment with soap and water.
  • Salinity – levels are variable, so better water changes are required.
Fish Lab - Sargassum frogfish (Histrio histrio) Marine Savers Maldives

Sargassum frogfish (Histrio histrio)

We have welcomed several uncommon new residents to our tanks.

  • Robust ghost pipefish (Solenostomus armatus) – quite rare in Maldives
  • Reef top pipefish (Corythoichthys haematopterus)
  • Painted-rock lobster (Panulirus versicolor) – we hope to grow it to join our main aquarium.
  • A Sargassum frogfish‘ (Histrio histrio), collected from seagrass near Voavah. In the wild, frogfish live in surface waters drifting among Sargassum seaweed, and if threatened by predators can jump from the water. Our frogfish lives in Sargasso weed, and we feed it one small piece of reef fish daily, by hand.
  • A ‘Common seahorse‘ (Hippocampus kuda) – very rare in Maldives – found in a ghost net drifting around Hulhudhoo reef. They are difficult to keep in captivity, being prone to bacterial infection and water-borne disease. Our seahorse hides amongst the branching structures in our tank, and we feed it thrice daily on 3-day Artemia.

Live Food Production

  • Algae – we produced 60L of the microalgae Nannochloropsis and 20L of Tetraselmis during January.
  • Rotifers – we are maintaining 60L of Rotifera culture with an average of 568 rotifers/ml.
  • Artemia brine shrimp – although we don’t yet have clown fish juveniles, we need some Artemia to feed our Fish Lab tank and new aquarium residents. We maintain the three Artemia stages: newly hatched, 1-day, 3-day enriched with Selco.

Throughout February, we produced 1516L of algae and increased our production of Artemia to 100L (5 per ml concentration).

Anemone project

Our anemone project was re-launched on 2 February with three anemones collected from Kamadhoo reef. We divided them with a simple cutting method to create clones, and then hope to grow them as homes for our Clownfish. The initial 3 anemones underwent 3 bisections to create 9 individuals, and the resulting parts are growing well.

Excursions

Our recent sightings of marine mega fauna include:

  • Hawksbill turtle (Eretmochelys imbricata), Green sea turtle (Chelonia mydas),
  • Jenkins whipray (Himantura jenkinsii), Spotted eagle ray (Aetobatus narinari), Porcupine ray (Urogymnus asperrimus),
  • Pink Whipray (Himantura fai), Blotched fan tail ray (Taeniura meyeni),
  • Sharks: Nurse (Nebrius ferrugineus), Blacktip reef (Carcharhinhus melanopterus), Whitetip reef (Carcharhinus longimanus), Oceanic whitetip (Triaenodon obesus).
  • Night snorkel safari: lion fish, squid and moray eels.
  • 41 Pilot whales (Globicephala macrorhynchus), 3 Blue whales (Balaenoptera musculus), 2 possible Beaked whales (unconfirmed) due to the characteristic head-shape and dorsal fin position. (More info on beaked whales is at NOAA, and rare video footage is at Gizmodo.)

Dolphin ID Project

More than 1,500 dolphins were sighted during January-February, mainly Spinner dolphins (Stenella longirostris) plus a few pods of Bottlenose Dolphins (Tursiops truncates).
The Spinners are usually observed in pods of 40 to 100 individuals. Many of the groups showed active and social behaviour, playing in the wake behind the boat and showing off their acrobatic skills – jumping, spinning, porpoising and bow-riding. Some calves (30-90cm length) were seen swimming alongside their protective mothers, and on some occasions even practising their jumping and spinning skills.

We are continuing to develop our ‘Dolphin ID’ project by taking photos of dorsal fins. So far, we have found it difficult as Spinner dolphins do not have such distinctive markings, and a high-quality photo is needed. But we have been able to individually identify several Spinner dolphins that we have seen and photographed on more than one occasion. This month we are experimenting with different ID software applications, and using a GoPro to capture underwater video.

Up to the end of February, we have uniquely identified 45 Bottlenoses and 20 Spinners in our database.

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