Effectiveness of sampling strategies for intertidal monitoring

Abstract

Multiple random quadrats (25cm by 25cm) were sampled at five sites on depositing shores in South Wales and the Isle of Man. The effect of increased number of samples was examined in relation to the reliability of estimation of various ecological measures - J, H', number of species, total individuals, total individuals of selected species. The replication required varies with the measure involved, but generally 10-20 or even more quadrats are needed for reliable information which can be used to detect other than very gross changes with time. In monitoring programmes it is thus advantageous to concentrate sampling effort on a limited number of sites with high replication because of this considerable spatial variation. The need to define specific aims, and to design a sampling format related to these aims, is emphasized. | Multiple random quadrate (25cm by 25cm) were sampled at five sites on deposition shores in South Wales and the Isle of Man. The effect of increased number of samples was examined in relation to the reliability of estimation of various ecological measures - J, H prime , number of species, total individuals, total individuals of selected species. The replication required varies with the measure involved, but generally 10-20 or even more quadrats are needed for reliable information which can be used to detect other than very gross changes with times. In monitoring programs it is thus advantageous to concentrate sampling effort on a limited number of sites with high replication because of this considerable spatial variation. The need to define specific aims, and to design a sampling format related to these aims, is emphasized.