Polychaete (Marphysa mosambica) Morphometrics, and their use in the Estimation of Whole Polychaete  Size and Breeding Values of  Bait Exploited by Artisanal Fishers at the Kenyan Coastline

Kihia CM*, Waigwa SW, Munyaka JM

Department of Biological Sciences, Egerton University, Egerton, Kenya.

Abstract: Polychaetes, such as Marphysa mosambica, are extensively used as bait in tropical artisanal fisheries, while, cultured polychaetes are exploited as fishfeed in mariculture. In order to monitor exploited wild and cultured polychaetes populations, metrics that predict growth and reproductive condition, are needed. Adult polychaete specimen were collected from mudflats at three locations along the Kenyan coastline. Measurements of the head, trunk and tail length were obtained and correlated to whole polychaete dimension. Breeding values monitored were condition factor and gonadosomatic index. Regression between morphometrics and whole polychaete dimension, and also breeding values, were obtained and the best variable estimator identified. Results indicate, adult polychaete along the Kenyan coastline are 97 mm long, with 170 segments and weigh 2.36g, with an average egg load of 106 eggs. Polychaete morphometric and condition factor differed among the locations, but GSI were similar. Differences were attributed to habitat characteristics and bait exploitation patterns. Polychaete trunk length and width, were best estimators (r²<0.4) of whole polychaete dimension, condition factor and GSI. Upon further validation, trunk dimensions may be used for rapid estimation of the total length, weight and reproductive condition of polychaetes.

Keywords: Morphometrics, whole polychaete, Condition factor, Gonado Somatic Index.

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