Climate-induced changes in the North Sea Decapoda over the last 60 years

Abstract

In the mid-1980s the North Sea ecosystem experienced a climate-induced regime shift that has favoured decapods and detritivores in the benthos and jellyfish in the plankton over com- mercial fisheries. Here, we investigate changes among the Decapoda in the North Sea plankton over the last 60 yr. Decapods are important predators in the plankton and the benthos where they can influence productivity and structure communities. In the North Sea it has been suggested that a climate-driven increase in decapod abundance has been important in propagating the climate signal through the North Sea food web. We show that climate-induced changes in the Decapoda in the central and southern North Sea include the presence of new warm-water taxa, changes in the abun- dance and proportions of commercial species of shrimp, and an earlier occurrence of decapod larvae in the plankton compared with the period 1981-1983. Notable amongst the warm-water taxa appear- ing in the North Sea is the predatory swimming crab Polybius henslowii that can swarm in large numbers when conditions are favourable and that is known to exhibit range shifts in response to fluctuations in hydroclimatic forcing. We suggest that climate-induced changes among North Sea decapods have played an important role in the trophic amplification of a climate signal and the devel- opment of the new North Sea dynamic regime. Understanding these changes is likely to be impera- tive for a successful ecosystem-based approach to the future management of North Sea fisheries at a time of climate change.