By Antoine Teitelbaum, Emmanuel Malpot, Koroa Raumea and Richard Story

 

 

The French Pacific Fund has agreed to support a cooperative project between French Polynesia and the Cook Islands, which will share skills in post-larval reef fish capture and culture. SPC’s Aquaculture Section, together with experts from French Polynesia (Aquanesia), has taken the lead in implementing this year-long project.

 

The main aim of this trip was to:

-       Introduce post-larval fish collection techniques to MMR’s staff;

-       Trial the efficiency of two post-larval fish capture techniques;

-       Train MMR and AMRC staff in collecting, sorting, identifying and growing-out commercially valuable fish species;

-       Develop a database to record the catch;

-       Explore the possibilities of accessing a reliable source of fingerling supplies for developing low-cost food fish culture; and

-       Develop ”eco-friendly” ornamental fish grow-out techniques to provide juvenile reef fish that can complement coral gardens supplied to hotels in Aituitaki.

During the visit, two types of trapping devices were used: a ”hoa” (or channel) net, which was deployed in a reef channel near AMRC (at Akitua), and two light-traps, which were moored south of the main pass at Aitutaki, a five-minutes boat ride from the town centre. A temporary sorting area was installed in AMRC’s hatchery, consisting of a 1 tonne tank prepared with floating trays in it to receive the catch and sort the fish.

The eight days of collection (during the new moon period of November 2007) showed promising results; a wide variety of fish and invertebrate species were recorded. The most abundant and potentially valuable families collected were surgeonfish (acanthurids) and mantis shrimps (stomatopods). During the sampling period, the channel net generally yielded higher catches than the two light traps (Fig. 1).

The main field tasks of this preliminary study were to train MMR staff in installing, maintaining, harvesting, sorting and identifying fish species. The SPC/Aquanesia team ensured that MMR staff were fully efficient in most operations, in order for them to repeat the operation during the fish colonisation period (from Spring to Summer).

MMR staff showed great diligence and skills in all these operations and were able to carry out all steps by themselves in only a few days. The bottleneck of this technology lies in the laborious task of identifying all larval fish species that are collected. Although it was fairly easy to identify the larger post larvae to the genus level, identifying to the species level was not an easy task. Fortunately, two post-larval fish identification guides were published in 2007[1] and the coral reef fish identification book by Myers end Lieske was very useful for this exercise.

A database to log all catch data was also installed on AMRC’s computer and Richard Storey was trained in using it. At the end of every sampling period, fish were recorded by species, site, abundance and status, whether they were dead or live.

Rearing commercially valuable fish was also dealt with during this trip. Most surgeonfish that were selected for nursery culture were isolated and placed in a clam raceway. That way, they could feed on turf algae growing on the sides of the tank although an artificial diet was also supplied to the fish. A small Artemia culture unit was also set up and AMRC staff were trained in hatching and harvesting Artemia, using plastic bottles and sieves.

Most non-commercial fish were released into the lagoon and a small diversity of reef fish were kept in a separate tank for display. Early trials were made with mantis shrimps, which were placed in small (10 litre) plastic containers with substrate and fed with minced fish. These immediately showed good burrowing and feeding behaviour.

The overall results of this first trip were encouraging; however, the total yield and the amount of commercially valuable organisms collected were not sufficient to prove any commercial viability at this stage.

The team also visited the rest of the island and surveyed the reefs for potential collection sites. Although there were many protected reef areas on the leeward side of Aitutaki that would be suitable for mooring light traps, there was only a limited amount of crest/channel areas suitable for collection.

MMR staff will continue post-larval fish collection during the new moon periods of December, January, February and March, and the results will be analysed at the end of the collection period. According to these results and the potential for commercial activities in Aitutaki, more funds could be directed towards extending the project.

A study tour for both Richard Storey and Koroa Raumea is being organised. These MMR representatives will be sent to Bora Bora in French Polynesia, specifically to Bora Eco Fish, a company specialises in post-larval capture and culture (PCC) activities and is currently involved in several related projects. An article discussing the outcome of this short training will appear in the next issue of the Fisheries Newsletter.

In mid- to late 2008, it is expected that an analysis of the potential for developing small-scale industries based on PCC in the Cook Islands will be jointly produced by MMR, local Aitutaki authorities, and external advisers.