Identify the critical factors in the present practice of the trochus hatchery and give guidance for improving techniques in the production system.
Carry out practice of trochus seed production with appropriate methods by using the existing facility.
Make recommendations on further programmes required towards development of trochus mariculture.
Submit a report of the study.
The study was conducted between January 11 and 24, 1989.
A fundamental problem encountered was that adult trochus could not be maintained in the tanks for more than four or five days before they all died.
An experiment was conducted which demonstrated that death was caused by some aspect of the aquarium equipment. The quality of the water being pumped from the sea was not the primary cause.
Possible sources of toxic contamination included the brass gate valves on the water supply lines and rust (iron oxide) leaching from the iron reinforcing material in the concrete tanks.
Patterns of mortality indicated that more than one factor was operating to kill the trochus.
Although water quality was not the primary cause of death of trochus in the tanks, it may have been a contributing factor. Evidence to support this includes frequent observations of diesel oil slicks on the water over the intake line, and of bilge water discharge from vessels in the same locality. Anti-fouling paints on the hulls of permanently-moored large vessels nearby may also cause pollution by copper-, lead- and tin-based compounds.
A possible alternative site for the hatchery near the village of Mélé was examined, and its advantages and disadvantages discussed. The criteria by which a site should be chosen are given.
A possible layout and design of the hatchery is given, as well as the size and number of tanks, pumps and other equipment.
Because of the inability to keep healthy adult trochus in the tanks, it was not possible to address the second objective listed in the terms of reference above — that is, to demonstrate larval rearing and seed production following spawning.
Despite this, larval rearing techniques were described to personnel at the Fisheries Department, and a manual of rearing techniques appended to this report.
Potential problems associated with establishing a trochus hatchery and ranching operation in Vanuatu are identified and discussed. These include high mortality of juveniles between outplanting on the reef and harvesting, the scale of ranching operation necessary to significantly augment the fishable stocks, and the social conflicts which may arise from re-seeding village-owned reefs.
If it is decided to establish a trochus culture project in Vanuatu, it should be re-located to a site with an unpolluted water supply. Port Vila Bay is unsuitable because of the continued pollution of the sea by the shipping industry as well as by seepage of nutrient-enriched groundwaters from the lagoon.
Possible hatchery sites on the island of Espiritu Santo should be examined, and compared with the site of the old Macrobrachium farm near the village of Mélé before a decision is made on its new location.
It is recommended that the aquarium equipment presently in place at the Fisheries Department in Port Vila be abandoned, and replaced entirely with new equipment at the new site. All equipment in contact with the seawater supply (pumps, tanks and pipelines) should be constructed from non-metallic materials such as PVC, fibreglass or concrete.
Recent advances in trochus culture and ranching made in other countries should be reviewed thoroughly prior to setting up a trochus hatchery in Vanuatu. If necessary, these should be adapted to Vanuatu conditions. In particular, it should be demonstrated that reasonably high survival rates during the ranching phase are achievable before proceeding.
The person chosen as hatchery manager should be experienced in mariculture, preferably of tropical invertebrates. He/She should become fully acquainted with these latest advances by visiting the Japanese Government-supported trochus facility in Okinawa, Japan and the Micronesian Mariculture Demonstration Center in Palau before commencing work in Vanuatu.
