Notes on an escallop (Pecten maximus) population in Holyhead harbour

Abstract

The sampling of a discrete unfished population of escallops at Holyhead by diving showed that there was no influx into the area of escallops at any age or size, other than by spat settlement. The success or otherwise of the spat settlement, which was very variable, determined the age- and size-distribution of the population. Evidence is adduced that normal dredge sampling gear is very selective or, if it is made unselective, becomes too laborious to use because of the low densities of escallops. In a commercially fished population the failure to catch the smaller escallops by the sampling dredges, combined with the fishing off of the larger ones, makes the age-distribution of the population appear always to be dominated by the 2- or 3-year-old escallops. The great variability of the success of year-classes is masked by this sampling selection combined with the effects of commercial fishing.