History of COTs around Efate Island in the last 30 years.
In an effort to help define the seriousness of the Crown of Thorns Starfish (COTs) problem in Vanuatu waters, various Scuba Operators have been monitoring and removing large aggregations wherever possible to minimise the effects of a second or third generation spawning event. Village Communities are often active in removing these echinoderms by snorkelling their home reefs or MPA's. However, unless they have a backup from Scuba Divers to remove the COTs in deeper waters, the critters will stay in the area, retreating to deeper waters by day and moving in on the onshore reefs by night.
Removing COTs from very-special, healthy reefs, with a high biodiversity of coral types, needs a coordinated effort by villagers on snorkel and scuba divers . But the Scuba Operators have logistical problems in supplying tanks, gear and competent qualified divers, if the areas of predation are too far from their bases of operation. It is all a matter of the costs involved. Fuel to run boats and outboard powered dinghies, electricity or fuel costs to pump compressed air into scuba tanks; vehicle transport costs to get divers to the dive base to join the boat, wear and tear on everything, crew wages, food to sustain the energy level of divers & snorkellers during a day's foray.
Even with snorkellers and divers working in unison, you can never expect to hit an area and clean it out wholly in one event. Once the larger aggregations are removed, it needs weekly cleanups to clear out an area. This could take 6 months to a year. So, from current observations, the areas that survive the onslaught best are Tourism-sensitive areas, where dive operators can continually monitor and remove the COTs during their routine operations.
Sailaway Cruises have been setting aside Saturdays, to be COTs removal days with volunteers or staff provided by the other Dive Operators (at their expense), even if the control areas are far removed from their normal divesites. Tranquillity Dive is now checking for COTs dispersals along the Moso coastline.
Sailaway is concentrating on the Paul's Rock to Mangaliliu coastline, Lelepa Island and monitoring Hat Island for arrivals. None at Hat so far.
COTs were first seen in a 1990-1991 outbreak emanating from Port Vila township, but also from a secondary source in the Moso/Nguna Islands areas. Several suspected causes were likely responsible for this infestation.
The massive underwater damage caused by Tropical Cyclone *UMA* in Feb 1987, where 30 year old, 4 metre diameter pristine plate coral gardens in Mele Bay were reduced to rubble, was perhaps the first trigger. As the corals started to regenerate in 1988, 1989, isolated COTs (which had not been seen prior to that time) could detect the weakened state of the marine ecosystem (less fish and coral to eat the COTs eggs, gamets and larvae), so that with the increased nutrients emanating from the effluent of a growing township and waterfront tourist resorts, a couple of big mama COTs must have decided this was a good place to drop their 30 million eggs.
Due to overfishing, and very likely the introduction of the Aquarium Trade about that time, and the removal of Triton shells, these eggs were no longer being consumed as they would be naturally.
Once an Outbreak gets underway, natural forces can't control it, and the COTs will move around coastlines dissolving the corals until there is practically no coral left. This has a devastating effect on certain fish stocks, as well as Tourism related businesses involved in snorkelling or diving tours. Not to even mention the gross out-of-balance the underwater environment now finds itself. Eventually the COTs move off to other islands, or their smaller offspring are carried Northwards in currents during the SouthEast tradewinds season. COTs aggregations are now being found in many of the Northern Vanuatu islands.
When most of the coral polyps are consumed, the COTs die of starvation; Or, where aggregations have been particularly large, a virus is thought to have spread amongst them (COTs AIDS ?).
But the environmental damage has been done and it takes over a decade for corals to regenerate to even half size, if there is sufficient base stock of coral left to spawn.
With each successive COTs outbreak, there is naturally less and less coral rejuvenation and diversity of coral types.
The second-known infestation began in Mele Bay, out from Port Vila again; but also again off Emao Island in North Efate, around 2006. Hideaway Island Resort pulled out over 30,000 COTs from Mele Bay reefs during the next few years; Big Blue Dive and Nautilus Scuba concentrated their efforts in dive sites and adjacent areas along the Pango coastline. An estimated 10,000 COTs were removed there.
So thankfully, they effectively controlled their prime healthy reef sites until the plague moved through.
It appears the residual COTs on the Pango side of Mele Bay then moved North up the East coast around 2010-11, passing through Erakor and Eratap Islets, skipping some reef areas, possibly due to this side of Efate being the weather side, so the COTs finding it uncomfortable to be thrown around in an onshore surf or be in strong currents, which makes gripping & feeding on the corals difficult.
We have confirmed reports of COTs aggregations at Manuro, but we don't know if they are Northbound COTs from Port Vila; or whether they are Southbound COTs from Nguna & Pele Islands.
Eton Beach area seems to be free of COTs, but nearby Eton village reports seeing COTs recently inshore, probably when this coast had calm waters in the summer months.
So we are unclear as to what is going on along the East coast. But it is a coastline which limits COTs controls, due to dangerous currents and also it is too far from Scuba facilities. So,efforts to control COTs there would likely be ineffective.
From 2007 to 2012, the Nguna /Pele/Emao islands were under assault. Starting from Emao, they jumped the channel to Pele and then worked their way up the East coast of Nguna Island. From our latest observations they have now moved across Undine Bay to the top end of Moso Island and are making their way down the outside of Moso to Lelepa Island.
Reports from this Nguna/Pele area indicate that reefs are now in a sad state, despite the sincere efforts of different Villagers to snorkel-remove them off their reefs.
Although we provided scuba assistance on several occasions to cull the deeper water ones, it was too far from our normal operating area to monitor over the long term.
It appears the COTs have now moved out of this area, moving down both the East and West sides of Efate.
It is like a pincer movement with the Port Vila COTs moving up both coasts to meet their comrades.
Our main concern now is to locate where the larger aggregations are on the calmer, Western side, where we have scuba support facilities at Tranquillity Dive and Sailaway Dive.
These COTs seem to be moving in a band from 8 to 25 metres (varies as to U/W topography) and not as yet confronting the fringing reefs. So snorkel support from villagers is not as yet required.
We can identify the healthier reef systems which we can try to defend, but even that will be difficult unless we can find financial support to pay for the daily wages of niVanuatu scuba divers who are currently without work.
Sailaway Dive will continue to go out COTs SWAT-ting on Saturdays and shall now be able to report our findings via the NAB webportal.
A couple of our previous COTs Reports can be found in the www.nab.vu site under Resources, under Article Search. Report #2 was on 18 Nov 2012; Report # 6 was on 23 March 2013 ; Report # 7 was on 30 March .
Earlier Reports on request. Today's entry below includes Reports #8 from 6 April; and #9 from 13 April and #10 from 20 April.
Cheers, Peter Whitelaw,
Sailaway Cruises
email: sailaway@vanuatu.com.vu
Tel: 23802 or 7723802 (mob)
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Brief COTs Report #8 for Saturday 6 April:
Hi Olgeta,
Our first scuba dive concentrated on the southern side of Paul's Rock base in 20 to 30 metres depth on an expansive low-lying coral reef sitting up off a sandy floor. Our attention was drawn by the white scarring now showing up amongst the healthy corals. There were quite a few clumps of COTs and other individuals hiding in holes by day. In depths greater than 30 metres, no COTs were visible and corals remained intact. With 6 divers in the water, we pretty-much cleared this reef of COTs, bagging 40 in a 100m x 100 m area. These were taken ashore.After lunch we moved further South and closer to shore in 15 m water, towing snorkellers in the water to look out for indicators of recent scarring.Our second dive was cut short when we realised that COTs had already moved through this area.Third dive was also only in 15 m depth inshore from Paul's Rock, where some scarring was evident. We collected another 40 COTs, took them to nearby Paul's Rock and left them underwater in the bags.On a normal day cruise, 24 hours later, we were able to tip them from the bags, belly-up and watch several varieties of fish enjoy the fresh-meat presented to them.We seem to be thinning out the number of COTs sighted in this Paul's Rock area, but we are sure further aggregations are on their way from Tukutuku Point (in background of the pic below)Other COTs sightings around Efate:Please let me know if you hear of any COTs sightings around Efate & offshore islands.Latest info from North Efate is that the plague in the Nguna/Pele/Emao area has moved West (& most likely South down the East coast too). There are unconfirmed reports of large numbers of COTs in Undine Bay, near Siviri Village and dining on the healthy reefs in the channel between East Moso Island and the mainland. This is the North entrance to Havannah Harbour and being a narrow entrance, could easily be defended by community snorkelling groups from Siviri, Sunae and Tassiriki Villages, with assistance from Scuba diving Operators in Havannah Harbour.However, once again, just moderate funding could pay for wages of local snorkellers to give-a-hand. Banana boats or canoes would be needed to move the collected COTs to shore.Outgoing and incoming tides would likely cause currents through this entrance, making collection & removal difficult at certain times of day.More info on this development next week. Next COTs SWAT on Saturday 13 April for any interested scuba divers.Cheers, Peter @ Sailaway Cruisesemail: sailaway@vanuatu.com.vuTel: 23802 or 7723802 (mob)
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COTs Report #9 for Saturday 13 April:
Dear Olgeta,
Our foray last Saturday, 13 April, was to the top end of Moso Island, following reports of numerous COTs feeding on the healthy corals usually found at the entrance to the channel between Moso and the mainland.
Reports were sketchy of local village lads removing plenty (some time ago ?? months or a year ago, probably), but the corals there being mainly eaten out now. Unconfirmed reports also indicated they were not moving down inside the channel into Havannah Harbour, but instead were moving down the outside of Moso Island.
Unfortunately we were unable to venture into this area with our boat because of the onshore NE wind. However we were able to drop off snorkellers at the top North Point of Moso (Lat: 17deg30.158minS; Long:168deg17.149min E )
and they snorkelled 1 Km down to the BatCave (17deg30.395; 168deg16.613 ) where we anchored in calm water.
Seawater visibility was around 30 metres, so 6 snorkellers spread out to cover the depths from 15 metres right in to shore. It is very difficult to spot COTs by day, as they are usually hiding under ledges, but there was a general dispersal of COTs sighted mainly in a band from 5m to 10m depths, but some right up on the fringing reef. They were mainly seen as individuals separated by an average distance of 20 metres apart, but some were in clumps.
It is hard work duck-diving down to these depths to collect COTs, so after lunch we set up scuba gear and dived a 200m x 80m area off the Bat Cave (white marker on cliff face).
6 divers collected only 50 COTs, which were spread out on the sea-floor as individuals, some very large, but a third of them being half-size, so likely a second generation bred in Nguna/Pele waters and now moving South.
The numbers and dispersal of COTs collected on the dive was consistent with what the snorkellers saw in the morning swim. No large aggregation, but predation ongoing as individuals, probably mopping-up after a larger aggregation moved through a year or more ago. There was not much evidence of recent white scarring. They had mainly been feeding on smaller porites coral and small hard corals. Most of the small plate corals had been eaten out previously.
The once-healthy fringing-reef corals had mainly been devoured several years earlier, going on the small amount of coral regeneration which could be seen amongst the black algae-covered skeletons.
There are obviously enough COTs remaining along this coastline and sufficient coral feed-stock for another generation to breed along here, unless these ones can be systematically removed.
Indications are that there is a general dispersal of COTs the full length of Moso Island, as they are now being seen on Lelepa Island.
So, to give more support to this assumption, on our return, we anchored at the end of Bells Reef, an extensive reef midway down the Moso coast and jutting several hundred metres out into the sea from the shoreline.
(Lat: 17deg13.87; Long: 168deg14.48). The bommies at the end of the reef get quite a current flow bringing in nutrients, so coral reefs in such places usually regenerate fairly quickly after a catastrophe like damaging cyclonic waves.
In a late-afternoon, short 15 minute check-out dive, the reefs in 2m to 20m depths had a very healthy coral cover of small plate acropora up to 30cm diameter, indicating that no large aggregation of COTs had moved through here, at least in the last 3 years. Very likely a cyclone around 3 to 4 years ago had wiped out the shallower corals and re-growth had occurred.
However there was some evidence of recent white scarring on this colourful reef, and on closer examination, COTs were found to be hiding in hollows. 8 smaller COTs were removed in an area of 30 metres x 30 metres, spread out, no clumps.
This healthy reef system deserves to be protected and further scuba diving and removal of COTs here is warranted.
Because the reef juts out so far into the ocean, any South-bound COTs have to pass around it, so it is an ideal place to set up a defence-line.
Next Saturday, we shall be checking out Lelepa Island, where there have already been sightings of COTs on the inside and the outside, but numbers are unknown.
OTHER COTs sightings:
Deeper reefs off Eratap Island were recently dived and found to be in healthy condition (Hat tip: Krystal @ Big Blue). So the large aggregation which moved up the East coast from Mele Bay, seemed to bypass this location.
Again, it looks like a fast-moving frontal line of COTs moves through in a particular depth band. The stragglers then come in after and extend the band towards shore, and at some stage clump together to facilitate fertilisation of eggs and thereby cause a re-generation the following year. So the Eratap area still needs monitoring for stragglers.
OTHER INFO:
1. Richard Chesher in New Caledonia has forwarded USA reports of COTs outbreaks in Micronesia in the late 1960's, where he headed a team of scientists to investigate.
This is very lengthy reading for those seriously interested in this phenomenon. I'll include one of his Reports in the PDF below. If any of you are further interested, I can send another 2 x PDF's, covering COTs science. Just email me. (Hat tip: Richard)
2. Robert Schabetsberger and Ursula Sichrowsky from Salzberg Uni in Austria were 2 weeks ago studying the migratory habits of eels from freshwater Lake Letas on Gaua Island out to spawning grounds in the ocean.
They came out with us on 2 days to get some underwater pics and U/W video footage of the COTs problem, so land-lubbers can get a better appreciation of what healthy reefs look like, what the white scarring looks like and the basic collection method we are using.
I didn't wish to feature in the short You-Tube video, but the only day Robert had the U/W video housing , I was the only diver on board during a normal Tourism-cruise. However on the COTs collection day he came out with us, he featured the niVanuatu COTs-SWAT team that day in the above-water footage.
6 min quick compilation of COTs footage: https://www.youtube.com/watch?v=QjeEJlJtfto
If you are more interested in Eels than COTs, then here is a YouTube insight into their project: http://www.youtube.com/watch?v=Zo1F32H-5aI for English sub-titles press button CC
All for now, Peter @ Sailaway.
email: sailaway@vanuatu.com.vu
PS: If you can provide more info on COTs sightings through the islands, please email, so we all get a better idea of the larger problem at hand.
If you wish to see underwater photos, or PDFs on COTs Science and Controls which were attached to the COTs SWAT reports sent out, then please also email & I'll forward them.
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COTs SWAT Report #10 for Saturday 20 April:
The aim of COTs control activities this day, was to check the dispersal and numbers of COTs along the seaward coastline of Lelepa Island, from the channel entrance facing Moso Island to the small island off the Northwest corner (closest point to Hat Island). We needed to find out if the Nguna-Pele COTs which we now knew to have moved along the Moso coastline, had also reached Lelepa Island.
First stop was at the Lelepa side of the channel between Moso & Lelepa Islands, just offshore the cliff-face which supported the Submarine Nets & walk-bridge across the Channel in WW2.
Lat: 17deg34.29 ; Long168deg12.58 min. We had 6 snorkellers in the water.
In the inter-tidal zone along the shoreline, the plate corals and more robust acropora were quite healthy, with colourful plates over 1 metre diameter. No sign of COTs from 0 to 2 metres depth. It was amazing that these larger corals had survived cyclonic wave action over the past 5 years.
But from 2 to 4 m depths we found a mix of large (50cm) and small (20cm) COTs, spread out as individuals , sighting one in every 5 x 5 metres square (= 25 sq. m.) approx. A quarter of the available corals had been eaten, moreso towards the dropoff into the channel and on the bommies within the channel. The sides of the channel from 4 to 10 m contained mainly dead corals covered in black algae, so heavily consumed several months to a year ago.
We could see that COTs had moved inside the Havannah Harbour side of Lelepa Island and also around the seaward side towards Hat Island. We took out 50 COTs, locating them by the fresh white scars.
Next stop was Mid-Lelepa Small Island, a popular snorkelling spot for Tourists. Close inshore no COTs were found, likely because the Lelepa Island Tours staff have been keeping this area clear of them on their day tours.
But on the reef extending out from the island, we found fresh white scarring in 2 to 10 m depths, so did a scuba dive to further investigate. We collected 28 COTs in a 100m x 100 m area, so they were widely dispersed and in hiding, so only located by the fresh scars. Most of the corals in this area had not seen a COTs infestation.
But there was no doubt that they were moving into this area from the Northeast.
Next stop was the Northwest Point of Lelepa Island and the large bommies off the Small Island facing Hat Island. COTs had arrived here, but only in very small numbers at this stage. We collected only 7 in 2 to 5 m depths.
Corals on the bommies which catch a good current and nutrients, were quite healthy. Plates were smallish at 25cm diameter, probably due to annual cyclonic wave action breaking them off when they get much larger.
Last stop was the Lelepa Lagoon with its sandy beach, used by Lelepa Island Tours. The outer part of the lagoon wall had seen a passage of COTs in the past few months, with not much live coral remaining.
But inside the Lagoon, the relatively fragile corals that live here, were in quite good condition. Very long blue branching corals; a brown lumpy, foliose-type coral and a few scattered bommies with plate corals up to 35cm across. Probably not the favourite diet of any fussy COTs used to dining on lush, smooth corals that are easy to slide over & extend their stomachs onto.
We collected 10 small COTs ( < 25cm dia) in the Lagoon in a 50m x 50m area. These were new generation COTs, indicating they had been in this general area for some time.
Total COTs collected for the day = 95, and these were taken ashore to a small remote beach on Lelepa.
So, as an over-view, COTs would appear to be in greater concentrations at the Eastern side of Lelepa and tapering off towards the Western side.
The villagers on Lelepa Island could cull the majority of these, just by snorkelling in 2 to 5 m depths. They need to be made aware of the problem on their doorstep and to be motivated to do something about it.
But, then the Moso villagers also need to be stopping them moving down the outside Moso coastline towards Lelepa.
Reports from Owen @ Tranquillity Dive and Bungalows, are that over the last few months, isolated groups of COTs have been removed from Tourist snorkelling reefs and especially at the entrance to Havannah Harbour on the Moso side of the channel in 2 to 6 metre depths. Their Scuba divers only found a few at 15 to 20 m depths.
In the last week an exploratory reconnoitre to Bells Reef revealed a largish aggregation of COTs on the Eastern side of this extensive reef, but close in to shore (2 to 4 m depths). Tranquillity staff were collecting COTs at a frequency of about 4 COTs per 10m x 10m square. This is a greater aggregation than what we had seen the week before on the outer part of Bell's Reef. This looks to be a priority area to protect from predation.
Again, Moso Villagers should be encouraged to help remove as many of these pests as possible and Tranquillity Dive can focus on the deeper water ones towards the end of the Reef.
The villagers are used to snorkel-spearfishing by night and advise that this would be the most efficient time to collect COTs, as they come out of hiding and feed at night. Go for a full-moon timing, but torches would also be needed.
They also advise that with winter approaching, the waters by July will be a bit too cool for serious snorkelling efforts. So now is the time to haul out as many COTs as possible.
Next Saturday, we at Sailaway shall be concentrating on further removal of COTs in the Paul's Rock area, where only a few COTs have come up near fringing reefs, so require scuba divers to collect them further out in 10 to 20 m depths.
Thanks to our volunteer team today, Kolen, Ada, Eric, Sam; plus Big Blue's Alex and Mattie; and Victoria from the Havannah.
All for now, cheers, Peter @ Sailaway Cruises
Below are the 3 x PDF's from Richard Chesher for in-depth scientific studies done on Acanthaster Planci outbreaks in Micronesia in 1969. Deja Vu for the South Pacific islands in 2012-13.
