Outdoor floating rearing ponds were used for mass rearing of eggs and embryos of Acroporid corals that were transported from slicks on the sea surface, after simultaneous spawning at Akajima, Okinawa, on May 23, June 13, 2003, and June 1, 2004. The mortality rate of embryos (i.e. until about 70 hrs post-fertilization) was high and varied by slicks, ponds and over time in a single pond. However, the mortality rate lowered among swimming planula larvae. A pond mean of 43% of the stock on Day 3 or 134 inds/l survived until Day 6 when they achieved viability for settlement. The embryos were concentrated on the surface of ponds, but the planulae were distributed more or less evenly throughout the water column. By reducing the density of embryos on the surface and providing shade to avoid direct sunlight, it will be possible to produce in the ponds more planulae able to settle on the substrate.

View full abstract

In 1996 and 1997, concrete box structures were installed in a shallow reef edge at Miyako Island, Okinawa (24°55'45"N 125°15'55"E) for rearing the commercially important top shell snail Trochus niloticus. Corals quickly attached on the quartz sandcoated fiberglass reinforced plastic latticed substrata on the bottom of the box. Within few years after severe damage of corals following extensive bleaching in 1998, however, the lattice was covered by Acropora-dominated coral colonies. In November 2005, coral coverage in four boxes was 50 to 90%. There were 25 species and the average size of the coral colonies was around 50 cm.
The accidental and rapid recruitment of corals on these aquaculture structures seems to have created an ideal environment for coral recruitment and growth. This finding provides a unique opportunity to gain insight into critical mechanisms of coral recruitment that may be used to improve coral reef restoration. The present paper deals with the aquaculture structures, environment, species diversity of corals, and possible factors that may have contributed to coral recruitment and growth.

View full abstract

The diversity and multi-functions of MPAs (Marine Protected Areas) in Fiji, Samoa, the Philippines, the Indonesia, Mauritius, and five districts in Okinawa were studied and effective methods to decide MPA size were discussed. The MPAs studied mainly target fisheries resource management. This study confirmed that the MPAs are powerful management tools in the tropics and subtropics. The nature of the MPAs differ greatly whether they are: 1) no-take or less strict, 2) government-initiated or community-based, 3) permanent or temporary, or 4) restricting only certain species or not. The size of the MPAs also varies significantly with multi-purposes such as eco-system conservation or eco-tourism promotion.
The larger the size of a MPA, the better it is for bio-diversity conservation. However, for the fishermen, too large MPA means the reduction of fishing grounds. The eco-tourism use of the MPAs also has potential conflict with fishing and dietary culture. To better balance these objectives, we need quantitative researches on the spillover effect, a process in which the organisms in MPAs spillover outside the MPAs. Simultaneously, with the participation of the fishing communities, the MPAs should be set and improved through “adaptive management”.

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract