Habitat Characteristic and Reproductive Biology of the Flat-ribbed scallop, Decatopecten radula (Linnaeus, 1758) on the Coastal waters of Guiuan, Eastern Samar

Abstract

Decatopecten radula is highly sought for its shell meat making it as a source of food and income for local shellfish gatherers in Guiuan, Eastern Samar. This study provides biological information for future conservation and management. Data were obtained monthly in the three selected sites within coastal waters of Guiuan, Eastern Samar from January 2016 to December 2016. These scallops were distributed at shallow areas of Trinidad Tubabao Island, Kamandag Reef, and Magluto Reef in depths of approximately 1-5 meters throughout the sampling period. Scallops are abundant in Kamandag reef where the site is characterized by its rocky area and mainly composed of a sandy bottom. Scallops were found on the surface of the sediment, attached to rocks or hard elements, hidden in a seagrass and seaweed. Physico-chemical parameters were observed within a narrow and normal range. Water temperature did not vary widely from 28°C to 30°C while salinity, pH, and dissolved oxygen ranged from 33-34, 8.2-8.7, and 3.4-4.8 mg/L respectively. The results from the 825 scallops showed that D. radula is dioecious species with four gonad stages (developing, mature, spawning, spent) based on the histological examination and calculation of gonadosomatic index (GSI). The spawning period of the species is protracted and spawning peaks occur from August to November with a male-female sex ratio of 1:1.24. Size at sexual maturity reached 55 mm shell height (SH) in males and 60 mm SH in females. Thus, the collection of scallop should be limited to individuals >60 mm shell height.