Crown-of-thorns starfish (Acanthaster planci) surveys at Lord Howe Island and the Solitary Islands

Brief description

In 1987, surveys of crown-of-thorns starfish (Acanthaster planci) were conducted at 10 sites on the fringing reefs of Lord Howe Island and 2 sites in the Solitary Islands. Surveys using SCUBA were conducted at diving locations where Acanthaster planci had recently been sighted. Initially, belt transects (100m long by 10m wide) were searched to quantify the abundance of starfish in these areas. However, limited dive time at depths below 15 m (most dives being conducted at depths of 25 to 30 m) required a modification of the search technique to enable the maximum area to be surveyed. Therefore, circular areas of about 40m radius (5,000 sqm) were searched.When found, all Acanthaster planci were measured (maximum diameter and arm number), examined for injury, and photographed in situ prior to collection. When the starfish were actively feeding, or located on a coral with recent feeding scars, their prey species were recorded. Other corals established within these areas which exhibited evidence of recent predation were also recorded, and their relative abundance in the community was estimated on a 5 point scale - dominant, abundant, common, uncommon or rare. The approximate degree of damage to the scarred corals and proportion of scarred colonies for each species within the areas surveyed, were estimated. During the searches, any coral species not previously recorded from Lord Howe Island were photographed and sampled.On return to the dive boat, the starfish were placed in a water-filled bin for transfer to shore where morphometric and genetic samples were taken. Each starfish was photographed prior to dissection of the aboral disc and two arms. Each sample was labelled and stored in 5% formalin for morphometric study. A 30-40g portion of the pyloric caecae was then removed from each starfish. These were sealed in plastic bags, labelled and snap frozen in liquid nitrogen for genetic analysis. As most adult starfish were found to be gravid, similar sized samples of the gonads were also frozen for gamete development studies. The aims of the study were: 1. to assess Acanthaster planci distribution, abundance and impact on coral community structure 2. to assess the reproductive success of crown-of-thorns starfish on these high latitude reefs. 3. to collect specimens of Acanthaster planci to be used in morphometric and genetic studies to determine if the populations on Lord Howe and North Solitary Island reefs may have developed as a result of larval dispersal in the southward moving East Australia Current from the GBR. Genetic studies of Acanthaster planci collected from Lord Howe Island are included in the metadata record "Genetics of the crown-of-thorns starfish, Acanthaster planci in Australia".

Lineage

Maintenance and Update Frequency: notPlanned

Notes

Credit
DeVantier, Lyndon M, Dr (Co Investigator)

Credit
Andrews, Greg J, Mr (Co Investigator)