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Horseshoe Crab Population & Distribution Survey
By Dr Hsu Chia Chi

Aims:

This island-wide survey aims to establish an estimate of the population and distribution of the two species of Horseshoe Crabs (HSCs) found in Singapore, namely the Mangrove Horseshoe Crab (Carcinscorpius rotundicauda) and Coastal Horseshoe Crab (Tachypleus gigas). Survey duration is from 2 pm to 6.30 pm. If you can help, please sign up at hsu_chia_chi@hotmail.com.

Sectors & Teams

Singapore will be divided into four sectors namely:

  1. North-West
  2. North-East
  3. South-East, and
  4. South- West
Each sector will have a Sector Leader. Survey areas within each sector have been identified and each will have an Area Leader. Depending on the size of the survey area, one or more teams might be assigned. Each survey team comprises four to six volunteers led by a Qualified HSC R&Rer (Team Leader), with an assigned recorder while participants become searchers-cum-measurers.

Survey Methods & Search Techniques

Two methods will be employed

  1. Transect search to depletion in areas where HSC density is expected to be high and/or
  2. Exploratory search in all possible HSC habitats. Search technique is based on HSC sighting and the gentle probing (NOT ploughing) of substrate with gardening forks as well as the careful digging up of buried HSC.
Area/Team Leaders will conduct on-site briefing on details such as the exact protocol, instructions and data recording.

Survey of Fishermen

In addition, there will be a survey-cum-conservation education of fishermen by younger members/primary school students. Using a survey-cum-conservation education questionnaire as well as photos of both HSC species, free and entrapped, they will approach local and recreational fishermen at boat mooring sites and popular fishing areas around Singapore.

Attire & Equipment

Recommended: Comfortable outdoor clothes (short or long sleeved tops; shorts or trousers), hat, sun block, old sports shoes/boots/booties that can get wet (NO exposed footwear such as sandals, crocs or slippers), drinking water, plastic bag (for collecting litter from survey sites), small gardening fork/rake (to probe for buried HSC) and 12-inch ruler.

Optional: Insect repellent, gloves or plastic bread wrappers to protect your hands, poncho (survey will be adjourned if there is bad weather), a change of clothes and extra foot wear (washing facilities may not be available at all sites), gardening cutters (to rescue Horseshoe Crabs entrapped in nets), binoculars, camera, note book and pen.

Directions

Meet at 2pm at your assigned meeting point. You may have to walk some distance to your actual survey area. The search proper will be from 4pm to 6pm, with the lowest tide at 5pm.

HSC Survey Result Presentation & Get-Together

This will be held on 21 March 2009 (Saturday) at the poolside of Ridgewood Condo at 6.30pm.

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