Surveying black bream, Spondyliosoma cantharus (L.), nesting sites using sidescan sonar

Abstract

Black bream, Spondyliosoma cantharus (L.), are summer visitors to the south and west coasts of the UK, overwintering in deeper waters and migrating inshore to breed from April to June. Bream are demersal spawners, with the eggs laid in a nest excavated by the male as it creates a depression in a sandy gravel substrate. To build their nests, male bream expose bedrock and gravel by using their tails to remove the surface layer. The present study, using sidescan sonar and SCUBA diving, extends the known occurrence of extensive nesting grounds off the West Sussex coast to the Isle of Wight and Dorset. The nests are typically circular craters 1-2m wide, and 5-30cm in depth, which can clearly be seen using sidescan sonar as groups of circular depressions. Several thousands of eggs (1-2mm) are attached to bare rock in the centre of these structures. All the eggs hatch by July. The species is valuable and particularly vulnerable to exploitation by both sport and commercial fishermen during its nesting season. With no minimum landing size and no prescription for Total Allowable Catch or the International Council for the Exploration of the Sea (ICES) stock assessment, they are suitable for protection under spatial planning measures, such as through the use of marine protected areas (MPAs).