Macrofauna Settlement on Pearl Oyster Collectors in Kenya: Seasonality and Abundance

Abstract

Collection of pearl oyster seed using artificial collectors is a critical step in the production of cultured pearls. This paper reports the seasonal abundance of macrofauna, which settled on spat collectors set to collect Pinctada margaritifera and Pteria penguin seed in shallow inshore areas at Kisite and Mombasa, Kenya. In both, settlement of macrofauna and bivalves was higher during the northeast monsoon season than the southeast monsoon season. Ascidiians and Sabellidae were significantly more abundant on collectors during the southeast monsoon season. A few bivalve species of commercial value including: P. penguin, Perna viridis and Anadara antiquata also settled on collectors during the southeast monsoon. Multivariate analysis showed the periods April-June and June-October presented significantly different macrofaunal assemblages in the open lagoon environment at Mombasa, whereas a significant difference occurred between assemblages settled during June-October and October-January in the channel environment in Tudor. Seven P. penguin specimens were obtained from 41 spat collectors in Kisite, whereas one P. margaritifera and three P. penguin specimens were obtained from 40 spat collectors deployed in Tudor Channel during the southeast monsoon period. From the results, settlement of P. margaritifera appears to be episodic and needs long term monitoring to determine the environmental and oceanographic conditions that are associated with its recruitment, whereas P. Penguin settlement occurred mainly during the southeast monsoon season.