The age determination and growth rate of the european flat oyster, ostrea edulis, in british waters determined from acetate peels of umbo growth lines

Abstract

Clearly-defined winter-growth lines are present in acetate-peel replicas of shell sections of the umbo region of the European flat oyster, Ostrea edulis. They are formed annually during March and April and cun be reliably used to determine age. The clarity of the annual winter-growth lines is variable: the first growth line is weak, ill defined, and composed of a number of finer lines, but the second and subsequent winter-growth lines are clearly defined. The pattern of annual lines in oysters from the River Blackwaler. on the east coast of England, are clearer than those from the two south-coast sites studied, the River Fal and Solent. Analysis of the annual growth lines has been used to provide first-ever estimates of the age and growth for these wild populations. Samples from three wild stocks consisted of mainly 2- to 6-year-old oysters with maximum ages estimated at 14 years (River Blackwater) and 10 years (River Fal and Solent). River Blackwaler oysters reach a size of 60 mm in 2-3 years and attain a greater size (Von Bertalanffy growth parameters K =0.41+0.18: L, n[ = 93.37 ±8.88) than stocks in the River Fal (K=0.35±0.09; LinI = 80.29 ±6.40) and Solent (K =0.46±0.17; Ljnf = 72.09±7.76). which grow to 60 mm in 5 years. © 1993 Conseil International pour l’Exploration de la Mer.