Philippine E-Journals

A preliminary study on shelter, avoidance and risks of juvenile Portunid crabs of the genus Scylla

Minerva I. Morales | Jimmy T. Masagca | Angelica V. Mendoza | Linda F. Talan | Estrella T. Tribiana | Ricardo V. Arcilla Jr. | Rosel Ibardaloza | Pedro Tumaque | Sonia A. Torio | * Cstifdp Research Team

Discipline: Natural Sciences, Agriculture

 

Abstract:

Many studies have demonstrated that habitat complexity is important to several benthic crustaceans (e.g. Scylla and Panulirus) because shelters provide the matrix of different sized refuges that organisms can use to escape from predation, rest and hide during molting. Two shelter structures as refugias were used in the study: (1) bamboo dens (7 cm x 30 cm forming letters T, L and X); and (2) “damhak”, a locally known structural lair or warren composed of a bundle of mangrove twigs and branches were used. Aerated marine wooden tanks (242 x 187 x 30 cm) with white background were set-up outside the facility of the Catanduanes Marine Multispecies Fish Hatchery (Palnab, Virac, Catanduanes, Philippines) and were stocked with juvenile Scylla serrata (±4.8 to 5.7 cm, carapace width or CW) to determine shelter-use patterns, feeding behavior, predator avoidance and risks of juvenile mud crabs from adults of S. olivacea (±10.5 to 15.5 cm, CW). Results show that that designs T and L were the most preferred but not for the X design; and further demonstrated that “damhak” is acting on the specific size of juvenile crabs that created the removal of demographic bottlenecks. This is most likely to have limiting influence on mortality; shelter provisions for escaping crabs in nylon net pen enclosures as well as risks reduction of the juvenile crabs from larger crabs.