Doug Beare

Prevalence of boreal Atlantic, temperate Atlantic and neritic zooplankton in the North Sea between 1958 and 1998 in relation to temperature, salinity, stratification intensity and Atlantic inflow

The Calanus finmarchicus population of the North Sea has collapsed since the late 1950s, while abundance of temperate Atlantic and neritic species groups has risen. These changes are explored in relation to the changing environment of the North Sea. Non-parametric regression methods are used throughout the study, in order to compare the spatial, long-term and seasonal dynamics of the changes in both biotic (e.g. C. finmarchicus) and physical variables (e.g. temperature, salinity, and stratification). The fall in the population of C. finmarchicus has coincided with a long-term freshening and warming of the eastern North Sea and a long-term increase in the salinity of the western North Sea. At the same time the prevalence of temperate Atlantic and neritic zooplankton species has risen. The changes may be explained by differing origins of Atlantic water entering the North Sea since the late 1950s.

Damage sustained by epibenthic invertebrates discarded in the Nephrops fishery of the Clyde Sea area, Scotland

The Clyde Sea Nephrops fishery produces ca. 25,000ty1 discards with invertebrates accounting for up to 90% of the number of animals discarded. Trawling and handling of the (by-)catch often results in physical injury, the extent of which was previously unknown.Damage sustained by invertebrate discards was assessed following commercial trawling (of 62-270min duration) and sorting on deck. Brittlestars Ophiura ophiura were most vulnerable with 100% incurring damage, followed by squat lobsters Munida rugosa (57%) and starfish Astropecten irregularis (56%). Harder-shelled species such as hermit crabs Pagurus bernhardus and queen scallops Aequipecten opercularis sustained fewer injuries (14 and 2%, respectively). Shell chipping, loss and damage of limbs were the most frequent types of injury incurred. The severity and frequency of damage was mainly correlated with species-specific morphological and behavioural characteristics. Vessel type, tow duration and animal size had a major influence on damage to the epibenthic invertebrates caught. While damage may potentially be repaired, survival is adversely affected and sublethal effects might significantly impair fitness of frequently trawled individuals and populations.