By Rafael D. Guerrerro III

The “curacha” or spanner crab (Ranina ranina) is a highly-prized marine crab that is steamed or boiled when served as a delicacy not only in the seafood restaurants of Zamboanga City, but also in Metro Manila. The crab is relished for its meat which is similar to that of the blue swimming crab. Unlike the latter, however, the spanner crab’s color is red even before it is cooked. The price for “curacha” is P300-P400 per kilo depending on size and supply.

The “curacha” is caught all year round in the coastal waters of Southwestern Mindanao between Zamboanga and Sulu. It is also found in Bataan and in the eastern coast of Africa, Indonesia, Australia, Japan, and Hawaii.

One of the few biological studies on the “curacha” in the Philippines was done by Juliana Baylon and Oliver Tito of the University of the Philippines Visayas in Iloilo. They reported that the crab is harvested at depths of 10-100 meters on the “sandy smooth substratum where it burrows feeding on small fish and other organisms in the sand.” It is caught using baited traps and tangle-nets suspended over flat frames. Berried females (egg-bearing) are found all year round with the peak in November to February. A mature female produces 26,225-354,084 eggs.

Live spanner crabs being sold in a fresh market (the crabs are upside down to prevent them from crawling).

From Australia, we gathered more information on the spanner crab and its management. The crab’s fishery in Queensland and New South Wales is the largest in the world with exports amounting to A$15 million a year. The main market for the live crab is East Asia.

In catching it, the crab gets entangled in a flat net, called a dilly, that is placed on the sandy bottom, at a depth of at least 100 meters in intertidal areas. Only crabs that have a rostral carapace (top shell) length of at least 10 centimeters (legal size) are allowed to be harvested. Any crab caught that is below the legal size is returned back to the water. It takes the female crab 6 years to reach the legal size, and 4 years for the male. The spanner crab can grow up to a rostral carapace length of 15 centimeters, and weight of 0.75 kg. It has a lifespan of 15 years.

For conservation and protection of the crab from overfishing, a “closed season” (a period when no fishing is allowed) is imposed by fisheries authorities in the months of November-December during the spawning of the species. Only a total allowable harvest of 2,000 tons per year is allowed. Moreover, it is prohibited to catch egg-bearing females which are returned back to the water.

This appeared in Agriculture Monthly’s March 2019 issue.