The role of climate in determining the temporal variation in abundance, recruitment and growth of sole Solea solea in the Bristol Channel

Abstract

Using a 24-year time series of monthly samples, the factors correlated with long-term variation in the abundance and growth of sole, Solea solea, in Bridgwater Bay in the Bristol Channel, England are identified. This bay offers shallow estuarine habitat used by sole as a nursery area. Sole first enter the bay in July when 2–3 months old and after a residence of 4–5 months, the majority migrate offshore at the beginning of winter to return the following April. By three years of age most have left the bay never to return although occasional large fish up to 480 mm in length are caught. Sole were found to be highly seasonal in their growth and only increased in length during the months of May to August inclusive. In recent years, there has been an approximately exponential increase in sole abundance that is highly positively correlated with seawater temperature during the early part of the season. The average length of fish in September, at the end of their first growing season, showed significant between year variation, ranging from 65·3 mm in 1989 to 79·8 mm in 2003. This variation was positively correlated with the North Atlantic Oscillation (NAO) winter index for the winter prior to their birth. Between year recruitment variation is correlated with both water temperature and the rate of growth. High temperatures allow faster development and a positive NAO index increases productivity and offers more food. Both of these positive influences act to reduce mortality resulting in stronger year-classes. No relationships between sole and other fish and macro-crustaceans living in the nursery were identified.