Crown-of-thorns starfish (COTS) control program : Voyage data - Catch per Unit of Effort (CPUE), Eradicated COTS size and coral cover from July 2013 - Jan 2015 (AMPTO)

Brief description

This dataset contains the voyage data from the crown-of-thorns starfish (COTS) control program operated by the Association of Marine Park Tourism Operators (AMPTO) from the Cairns to Lizard island region. It contains the data from two control vessels (MV Hero and MV Venus II) with a total of 64 voyages, each of 10 days. This dataset contains a record of the work activities (Dive, Transit, No Diving - other, Departure delayed, etc.) on each voyages as well as the Catch per Unit of Effort – number of COTS injected per minute of dive time, the size and number of COTS caught and eradicated and the coral cover at each site estimated with Reef Health Impact Surveys (RHIS). The AMPTO COTS program was established in July 2012 with the primary purpose of protecting the coral cover at high value tourism sites. The control efforts were initially conducted by MV Escape, which was in operation between March and August 2013, and MV Hero, which began operations in August 2012. The contract for MV Hero was renewed in July 2013 until June 2015 (Contract 2). In December 2013 a second control vessel (MV Venus II) was added to the control program. Methods: Control is conducted over a ten day voyage with each voyage designated a target area. The Voyage Plan is determined by the Project Manager in consultation with the managing agencies (GBRMPA and RRC). The current work program has the vessels confined to the seven target areas that comprise the main tourism region off Cairns and Port Douglas. This means that a Target Area is controlled every 2 months by one of the vessels. Occasionally the vessels will respond to requests from tourism to assist them with COTS control at their site, the vessels may travel outside of their target area to assist the operator. The crew will fish down the site (usually between 2-4 control dives) before returning to the scheduled target area. A total of four control dives are done each day of the ten day voyage with the exception of the first and last day when only two control dives are conducted to allow for victualling and berthing of the vessel. The number of sites controlled on each voyage depends on the size of the sites and density of COTS within each site but is usually between 10 and 16 sites. Control dives are normally 40mins in duration using all available crew to conduct the control (the available crew fluctuates between 4 and 11 divers). Depending on the site and crew available the divers are often broken into groups to sufficiently cover the polygon depicted as the control site. Whilst all efforts are made to cover the dive site polygon during the control dives some areas may be excluded from control and the divers may control some areas outside of the polygon (an error value of +-5% of the total area of the polygon may be applied). For example if the site is along a wall the crew would be broken into two groups and move in opposite directions along the wall. Divers would be spaced about 5 metres apart (depending upon visibility and density of COTS) covering the crest and slope of the wall. If COTS are in the shallower part of the reef then snorkelers may be used to cover the reef flat. If a site has a dense population of COTS in one section of the reef, the crew would usually concentrate their efforts in this area to fish down the population as much as possible, before completing the rest of the site. If it is a large aggregation the crew will return to the site after a day or two (if time and weather allow) and cover the area of concentration again, this is to allow the injected COTS sufficient time to die and dissolve, ensuring that any COTS that were missed on the first control effort are picked up and not mistaken for COTS already culled. Sites are selected based upon location and intelligence from tourism operators and surveys conducted by Marine Parks, as well as scouting trips conducted by crew on board the AMPTO vessels. The sites that are used by the tourism operators (generally those with their own names or GM numbers as site names) have already been designated by the operators and will cover the extent of their operations at that site. Sites that do not receive regular visitation from tourism vessels have been established by the COTS control program (usually following the naming protocol of Reef Name Site no. (for example Arlington Site 1) and will normally cover an area that can be controlled by two control dives with an average of eight divers in the water. Control divers will search their designated area looking for white scarring that indicates a COTS feeding scar. When scarring has been found the diver will search an area around the scar to find the COTS and then inject it with a bile salt solution delivered by a needle at the end of a 50cm spear. COTS can usually be found within a 1m2 area from the freshest feeding scar, however there are instances when the COTS has moved a significant distance and cannot be found. COTS are generally found by the diver within 30 seconds of searching but if nothing is found after a thorough search (or is impossible to reach as it is too deep in a hole), then the diver will move on and continue searching for the next animal. There is some variation in the skill level of divers being able to identify COTS scarring although this is primarily only relevant when looking for juvenile COTS (<15cm diameter). In large outbreaks COTS will switch behaviour and instead of hiding throughout the day they will be out in the open. In large outbreaks the COTS will form into feeding fronts where there is an extremely dense aggregation in a small area, with groups of COTS often feeding on the same coral colony. In these aggregations the whole crew will be used in a single area with all the divers moving across the feeding front in a line with minimal separation distance. Control was initially conducted using sodium bisulphate and injecting COTS multiple times (up to 26 times depending on the size of the animal). In June 2013 the AMPTO crew assisted a combined research team involving James Cook University (JCU), the Australian Institute of Marine Science (AIMS) and the Australian Research Centre (ARC) in developing a new injection technique using a bile salt derivative. This new injection technique reduced the number of shots required to inject a COTS (down to a single shot per animal) improving the efficiency of control efforts. In August 2013 AMPTO received permission to begin using the single shot bile salt method for all control work. This change in methodology affected the CPUE, particularly where there were dense aggregations of COTS. Most of the data in this dataset (except for Hero Voyages 1, 2, 4 and half of Voyage 3) corresponds to voyages using the single shot injection method. At each site a total of three Reef Health Impact Surveys (RHIS) will be conducted to establish the percentage coral cover. RHIS point surveys cover approximately 80m2 of reef and involve estimating the benthos cover, which includes the live coral cover, as well as identifying and quantifying any impacts to the coral. These surveys will be conducted over coral nearby to COTS control sites and are not necessarily indicative of the entire reef’s average coral cover. If a reef site has never been visited the RHIS sites are selected randomly within the control area. All three RHIS points are recorded as GPS co-ordinates so they can be repeated on subsequent visits. The coral cover for the site is established by taking the average live coral cover from the three surveys and can be used to track changes over time to establish the impact of COTS and the effectiveness of control efforts. All three RHIS are taken from the same habitat type on the reef (e.g. all from a reef flat or all from the crest) so as to not skew the average coral cover which is pooled for the three RHIS. Limitations: The dataset uses CPUE (catch per unit of effort (=no. of COTS injected / dive time in mins.) to estimate the population of COTS at control sites. CPUE is a highly variable quantification method and can be impacted by a number of factors: visibility, rugosity and complexity of the site, currents, swell, surface conditions, experience of the divers and time of day can all contribute to differences in the CPUE. The crew are sufficiently trained to be able to find COTS and all attempts are made to ensure that the crew are diligently searching for COTS in their assigned area to minimise discrepancies. Although there will be some variation with differing levels of experience and ability to identify scarring. Likewise CPUE should only be compared at the same site as differences in the site layout and composition of the benthos will make COTS harder to find. The change in injection method that occurred in August 2013 has some major implications for the use of CPUE. Whilst the CPUE is still dependent upon the density of starfish at each site, where there is a high density of COTS (>40starfish per 10m2) (or a CPUE >1.0) the single injection method using bile salts can improve the efficiency of control by reducing the amount of time required to inject the animal. This is particularly useful in dense outbreaks where COTS are largely sitting on top of the coral and crew do not have to spend time searching for the animals. Hence the CPUE recorded in dense aggregations are significantly higher than those recorded with the original sodium bisulphate method. At lower densities (CPUE < 0.5) use of the single injection method does not have a noticeable effect on the CPUE as the majority of dive time is spent looking for COTS rather than injecting them. The coral cover data that is recorded in the dataset is derived from the RHIS surveys conducted by the crew. These surveys use estimation to determine coral cover which is then averaged out over three surveys per site. The RHIS crew undergo rigorous training and are regularly checked to ensure that they are estimating benthos categories in a similar manner, however as the method is based upon estimation there is some variation in coral cover. GPS co-ordinates are used to locate the survey sites however there is some variance in the area surveyed as the GPS is only accurate to +- 4 metres and the crew are being dropped into the water from a non-stationary vessel. To eliminate this problem permanent RHIS sites have been established. At permanent RHIS sites, three star pickets have been placed into the substrate and these pickets are used as the centre point of the survey circle. A total of 36 permanent RHIS sites have been established with two more still to be installed. Format: Excel spreadsheet for each vessel (MV Venus II and MV Hero) containing a record of each voyage. Each spreadsheet contains a number of sheets including: Summary (by voyage), By Site, one sheet per voyage (V1 - V54), Site list, datasheet (containing all voyages in one table) and By voyage pivot check. The spreadsheet contains sheets for future planned voyages which have blank data. Data Dictionary: - Date: Date of the work activity - work: Work activity during the voyage (Values: Dive, Transit, No Diving - dangerous weather conditions, No Diving - other, Departure delayed) - Reef ID: GBRMPA Reef ID of the sites for Dive work or 0. (Examples: 14-116a, 15-082, 16-028) - Location: Name of the location. (Examples: Lizard Island, Emily Reef, Low Isles) - Zone: Marine park zone of the site (Values: Habitat Protection Zone, Marine National Park Zone, Conservation Park Zone, Buffer Zone, Scientific Research Zone). - Target Area: Each voyage is assigned a Target Area in which to work with the intention that control will be conducted at all the available sites within the Target Area. The Target Area map was initially established in February 2013 where the reefs between Lizard Island and Cairns were divided up into seven target areas (see Figure 2). Target Area 1 has been left free as it encompasses the area north of Lizard Island, so the Target Areas start at Area 2 (being the reefs near Lizard Island) and work their way south to Target Area 8 (the southernmost reefs in the Cairns Region). An eighth Target Area was assigned to the Whitsunday area (Target Area 9), as three voyages have been conducted in this area at the request of the Whitsunday Tourism Operators. In June 2014 the Target Areas have been revised and are now broken down into smaller areas in the Cairns and Port Douglas region (Target Areas 6,7 and 8), to provide greater control in the tourism areas and ensure that coral cover is protected at the high value tourism sites (Values: 0, 2, 3, 4, 5, 5.1, 6, 7, 8, 10) - Site / Polygon Name: Unique name given to each site. (Examples: St. Crispin Site 2, Opal Site 2, Bashful Bommie, South East Channel Site 3) - GPS: Coordinates of the centroid of the site. Note: this is a single column with both latitude and longitude combined as a string.(Example: 16°56.481' S 145°51.071' E) - Operator: The tourism operator who operates the mooring - Selection Matrix Score: A score based on the first visit to that reef with weighting given to; proximity to tourism sites and the tourism site value, whether there are existing COTS control measures being implemented at the site, coral cover, density of COTS and density of COTS >15cm (double weighted). - Average Depth (m): Average depth that the eradication operations were undertaken. - Bottom Time: Number of minutes of diving associated with finding and injecting COTS - <15cm: Number of COTS smaller than 15 cm culled during the dives. - 15-25 cm: Number of COTS between 15 - 25 cm culled during the dives. - 25-40 cm: Number of COTS between 25 - 40 cm culled during the dives. - >40cm: Number of COTS bigger than 40 cm culled during the dives. - Total: Total number of COTS culled in the dive. - CPUE: Catch per Unit Effort - number of COTS injected per minute of dive time - RHIS Date: Date of the RHIS performed at the site along with the control diving. - Average Coral Cover: Coral cover estimate from the RHIS surveys at the site. Average of 3 RHIS over the area of the site. - Water Temp (oC): Water temperature measured at a 3m depth at the end of the site. - Visibility (m): Estimated water visibility in metres at the end of the site visit. This is visually estimated by the dive supervisor. Data Location: This dataset is filed in the eAtlas enduring data repository at: data\COTS-IMP\GBR_AMPTO_COTS-control