An overview of the LEAR (Lobster Ecology and Recruitment) project: results of field and experimental studies on the juvenile ecology of Homarus gammarus in cobble

Abstract

Field and experimental studies were undertaken in four European countries on clawed lobster (Homarus gammarus) ecology and recruitment. The aims were to assess: (a) abundance of early benthic phase (EBP) lobsters and other benthic species at cobble sites, (b) the effect of these species on EBP growth and survival, and (c) influence of these factors on recruitment and/or viability of restocking. Suction sampling of cobble sites revealed a wide diversity and abundance of potential competitors but no EBP lobsters. Hatchery-produced EBPs were therefore used for small-scale mesocosm experiments. In nature, predation on EBP was rapid without shelter, whereas in-vitro mortality, growth, and behaviour experiments showed that cover potentially increases survival. Scarcity per se may not completely explain the apparently absence of EBP, given that not a single EBP lobster was located either during this study or during any other of the extensive benthic investigations. The present paper discusses the implications of their apparent absence and whether it arises because EBPs are very scarce, cannot be captured by suction sampling, are not within lobster habitat, or occupy a specialized niche within adult habitat outside the range of current sampling methods.