BAR TODAY || Official Quarterly Publication of the Bureau of Agricultural Research

Sea urchin (Tripneustes gratilla) research
project
by Marie Antonette Juinio-Meñez, Ph.D.

April-June 2000
Volume 2 No. 2

From 1988 to 1992, the reef flats of Bolinao, Pangasinan supported a thriving sea urchin (Tripneustes gratilla) fishery that generated multimillion-peso earnings per annum for the country. It was also the source of livelihood for thousands of coastal fisher families. However, uncontrolled and non-selective harvesting of spawning stocks inevitably led to the collapse of the fishery in 1992. Despite the imposition of a moratorium on commercial harvesting, no significant natural recruitment has been observed in the past few years.

Clockwise,left to right: shucked T. gratilla showing five strips of gonads; juvenile rearing in aquaria; and sea urchin delicacies

The sea urchin culture was initiated at the Bolinao Marine Laboratory of the University of the Philippines Marine Science Institute in 1993. Its aim was to enhance the recovery of T. gratilla spawning populations. Grow-out culture in sea cages/pens was deemed to be a very promising mechanism for the sustainable management of sea urchin resources. Artificial aggregations of sea urchins in grow-out cages may increase successful fertilization during spawning and may enhance local larval recruitment. In addition, sea urchin grow-out culture can be a supplemental source of livelihood for fishery operators.

To date, the project has successfully closed the entire life cycle of T. gratilla in the laboratory. The project site maintains the only echinoderm hatchery in the country. The hatchery produces approximately 40,000 sea urchin seedstock (>1cm TD) per annum. The seedstock is used in pilot grow-out studies and made available to interested cooperators. It is also used for reseeding in marine protected areas.

Sea urchins attain sexual maturity at an average size of 6.0 cm TD, about eight to nine months after settlement. Experimental grow-out culture and reseeding of cultured sea urchins in Bolinao were conducted since 1996. At any given time, there are 6,000-10,000 adult sea urchins in the grow-out cages on the reef flat. The sea urchins are harvested only when they measured 7.0 cm in diameter. In addition, about 40,000 sea urchins were reseeded in selected reef areas in Bolinao. The impact of these enhancement activities is difficult to ascertain.

However, for the first time in 1999, significant natural sea urchin recruits were observed at various reef areas in Bolinao. No recruits have been found in adjacent reefs, including the Hundred Island National Park. Also in 1999, recruits were particularly notable at the community-managed marine reserve in Bolinao which was reseeded with over 2,000 cultured sea urchins in 1997.

The results of a preliminary larval dispersal model suggest sea urchin spawning populations in Bolinao may not be self-seeding, and that T. gratilla populations along the northwestern coast of Luzon may be interconnected through reciprocal larval exchange. In order to test this hypothesis, the project is also undertaking a population genetics study to determine the degree of genetic contiguity of T. gratilla populations along the western coast of Luzon.

Current research funded by the Department of Agriculture-Bureau of Agricultural Research is geared towards the development of appropriate grow-out culture protocols and the promotion of grow-out technology to fishers at selected localities in western Luzon, using either cultured or wild seedstock. The project also conducts periodic workshops/trainings on sea urchin grow-out culture and on management for fishery managers, extension workers, students and interested fisherfolk.