Development of new artisanal fisheries based on the capture and culture of postlarval coral reef fish

• Ministry of Agriculture and Fisheries, Solomon Islands
• Australian Institute of Marine Science, Australia

In the early 1990s an industry was established to collect tropical marine fish for the aquarium trade (mainly for sale in North America and Europe) and harvest groupers, snapper and the napoleon wrasse for sale as live fish for human consumption-often to up-market restaurants in Hong Kong, Taiwan and China. The industry grew rapidly and soon virtually every country in the South Pacific and Southeast Asia supplied one or both of these markets. The high value of the trade led to over-exploitation in several places. In addition, the collection methods often damaged fish stocks. Of particular concern was the use of sodium cyanide to 'stun' fish, which could then easily be collected. In the process, many fish and other organisms were killed.

Non-destructive fishing methods for these species existed, and various NGOs trained coastal communities in their use. However, despite these good intentions, there was growing concern that harvests of coral reef fish were simply not sustainable. A possible solution was to collect postlarval fish in numbers that would not affect the replenishment of natural populations and culture these to marketable size, using simple techniques and readily available food sources. For best results, the fish would be caught whilst still in abundance, which meant before they suffered the naturally high mortality that occurred during their growth.
Fish could be caught either using light traps or crest-nets. Research was needed to determine which method was preferable, as well as to assess levels of abundance and any seasonal fluctuations, and to develop methods for coastal villagers to grow selected species to marketable size. This project concentrated on the situation in Solomon Islands, a country that typified tropical reef fish operations in the South Pacific. Coastal villagers collected about 150 species for exports, although only about 40 species accounted for the majority of sales.

The project aimed to increase the production of marketable coral reef fish-and reduce reef damage-by providing the means to capture and then rear the postlarvae of desired species in a sustainable fashion.

The work was divided into three sub-projects in line with the three objectives. In the first, temporal variation in the abundance and diversity of postlarval fish was assessed near Gizo in the Western Province of Solomon Islands. The second sub-project compared light traps and crest-nets as catching methods to determine whether they differed in total catch, the species caught and the condition of the postlarvae.
The third component identified the target species most amenable to culture. The team studied the growth and survival of these to minimum marketable size, and identified suitable foods. This sub-project also calculated the cost-effectiveness of rearing the postlarvae.

The project substantially achieved its research objectives despite a period of civil disturbance that required the evacuation of the on-site project leader, and despite ongoing uncertainty in Solomon Islands. The researchers found that temporal variation in most species captured was low and generally unpredictable, with the only major exception being the puerulus lobsters, which showed peak abundances in July, August and September during the two years of sampling.

Light traps were found to capture large numbers of low-value fish species and were relatively expensive to construct and operate. Researchers recommended that no further development of this technology for capture of post-larval reef fish in Solomon Islands was justified.

Crest nets, however, captured smaller numbers of high-value species, including lobsters and shrimps. The number of invertebrates and finfish captured in crest nets indicated that further development of this technology could provide an economically viable technology for collection of post-larval fish for the aquarium trade. Thus researchers recommended that further capture technology development should focus on crest nets. In their current form they resulted in substantial mortality of captured fish, so a redesign was advocated.

Neither crest nets nor light traps captured sufficient numbers of fish to supply the live reef fish food trade. The project thus focused on marine aquarium fish. Feedback from the aquarium fish exporter in Honiara indicated that captured-then-cultured fish showed better adaptation to captivity than wild-caught fish, in that they were less 'nervous' in the tanks and more readily accepted food.

A rough cost:benefit estimate indicated that, using catch and value data from the project, a fisher could expect to repay the capital cost of a collection device after about 25 nights fishing. The project team identified a number of potential sites throughout Solomon Islands where modified reef crest collection devices could be established. Reviewers recommended a program of follow-on research, development and extension activities to realise the benefits of the project for coastal communities in the South Pacific.