Monday, 13 June 2011 10:27
Between March 15th and April 26th 40 points were surveyed at the Corral study area. This mapping study was conducted using a modified version of the circular transect methodology that allowed for more precise sampling and a greater completion rate of surveys. A total of 47 seahorses were found at 21 of the study sites. The greatest number of seahorses was found along the southern edge of the study area, suggesting that the greatest population density may occur outside of the sampled zone. The study area has therefore been increased with the addition of 10 new points in order to include this area in the study parameters. These new points will be surveyed during the month of June, and will increase the Corral study area to 50 total points with an area of 1.8km2.
The data collected from the study suggests a general picture of the population structure, distribution and habitat preferences for the seahorses in the Corral study area. A strong preference was found for pencil urchins as habitat, with 72% of seahorses being found attached to urchins. This association was significantly more common than attachment to any other substrate, particularly for juveniles, indicating the importance of pencil urchins as habitat for seahorse populations in the area. Bottom-scraping activities such as trawling, which often remove seahorses as by-catch, may therefore have significant secondary negative effects on seahorses by removing important habitat that may play an important role in the settlement of juveniles.
The population structure of seahorses in the Corral area was found to be fairly even, with a total of 19 adult females and 14 adult males found. 11 juvenile seahorses were found, suggesting that the population has been actively breeding throughout the spring season. The presence of two pregnant males indicates that the population remains reproductively active and that breeding occurred within 2 weeks of the sampling period during which they were found.
In addition to the extension of the Corral study area with the 10 new study sites, the area has been divided into a GPS grid in preparation for the next phase of study of the seahorse population of Koh Rong Samloem. 476 new points were created to allow for random sampling during a population assessment, which will be conducted during the month of June. 35 randomly located transects will allow for accurate estimates of the population size and structure, and the inclusion of species identification in the methodology will allow for greater understanding of seahorse diversity in the area. With 5 species positively identified from the area and a total of 8 species having ranges that include Cambodian waters, this assessment could provide important insight into one of the most diverse seahorse habitats currently under study. Over time, repetitions of this study will allow the population to be tracked, and will reveal shifts in abundance, structure and diversity. These results can also be shared with other seahorse monitoring organizations to increase the global understanding of the condition of seahorse populations, and allow for more targeted conservation efforts.
Wednesday, 29 September 2010 10:53
Marine Conservation Cambodia is excited to have a positive Id on one of its Seahorse sightings.
So far no sightings of this species (Hippocampus Mohnikei) have been officially recorded in Cambodia. This is our first big find since the sighting of a new species of Nudibranch in early 2009
Found in Kampot's extensive Seagrass beds this small pregnant male seahorse was captured on Camara in November 2009.
Often it takes sometime to go through all of our survey photos and then more time to get a positive identification.
This find came as we have been updating our Cambodian Marine Fish Species List and with the Addition of this find and over 70 other marine fish species this is the most extensive Cambodian Marine Fish Species database compiled so far. This new list will be available online shortly
A big thank you to Rachel Atanacio and Dr Lourie for the Identification of this small Seahorse.
Sunday, 29 August 2010 12:48
During April and May 2010 Marine Conservation Cambodia (MCC) research divers observed a significant amount of bleaching affecting the coral reef systems around Koh Rong Samloem and Koh Koun. More than 50% of the coral coverage was suffering from bleaching on the surrounding reefs. Bleaching affects corals and also certain invertebrates. Bleaching is actually the loss of a specific algae (Zooxanthellae) due to stress. This algae has a symbiotic relationship with its host, supplying colour and providing the majority of energy needed by the host organism.
Luminescence of organisms is an indicator of stress before the final bleached stage. Luminescence was observed in a large majority of hard and soft corals, giant clams and anemones. The process of luminescence is a reaction of the zooxanthellae to increased sun exposure and acts as a sunscreen. The algae pigment cells react to the additional sun energy by breaking up the sunlight into the colour spectrum and expelling the more damaging energies, giving the coral a fluorescent colour. Near the end of this process, if the health of the coral is not improving, the algae leave the zooxanthellae and the coral is considered bleached.
One factor which is known to have an effect on the reef’s organisms and cause them to come under stress is water temperature. The proposed explanation for the current bleaching incident is due to an increase in oceanic temperature. Tropical reefs normally exist within a temperature range of 27⁰ Celsius to 32⁰ Celsius. When the temperature rises above this range, the organisms within the reef show bleaching. This has occurred in other coral reef systems around Jamaica in the Caribbean Sea and also the Great Barrier Reef in Australia. The water temperature in Cambodia around Koh Rong Samloem and Koh Koun rose from an average of 30oCelcuis to a peak temperature recording of 35oC.
Bleached coral may recover if zooxanthellae return to the coral. It has been documented that corals that recover zooxanthellae within four to six months after a bleaching event are more likely to return to a healthy state (Diaz-Pulido and McCook 2002). The fate of the bleached coral is dependent on the ability of the coral to out-compete the algae. Oceanic temperatures have decreased dramatically with the arrival of the wet season. Temperatures are once again averaging 30oCelcius and dropping frequently to 29oCelcius. Hopefully with this reduction in temperature the majority of the coral reef system will successfully recover.
In the past two months it appears that some of the corals are starting to recover and the majority of clams are also appear much healthier. MCC research staff and volunteers will continue to monitor the extent of bleaching and rates of recovery.
We have so far produced to documents on the bleaching event here in Cambodia the surveys conducted focus on four main tourist dive sites, the first document is on the initial extent of the bleaching during the months of April and May the second was conducted during July and August to monitor for signs of recovery or continued bleaching. These documents are available on request.
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