Age-related and seasonal changes in haddock Melanogrammus aeglefinus distribution: implications for spatial management

Understanding the persistence of fish aggregations is essential for the development spatial fisheries measures and marine spatial planning advice. This study examined the temporal persistence of haddock Melanogrammus aeglefinus aggregations and life-stage sensitivity to conditions in the North Sea during the period 1991 to 1997, using a 2-step generalized additive model. Geostatistical aggregation curves and the spaces selectivity index indicated physical habitat preference was independent of changes in annual abundance. Juvenile haddock distribution did not conform to definitions of nursery area as there was no major shift in habitat use following settlement or seasonally persistent aggregation. Nevertheless, there were some age-related differences in temperature, depth, salinity and sediment preference. Depth the largest deviance in abundance models for most age-classes and seasons, but it was to disentangle the relative contribution of this factor and salinity to habitat preference. The of age 1 haddock indicated a preference for coarse sands in the winter and spring, which reflect the distribution of prey. Thermal regime was an important constraint on age 0 distribution in quarter 3 (summer), as this life stage preferred areas <11°C, which were limited to a narrow of the northern North Sea. Moreover, this habitat is predicted to decrease in the following . The present study, together with past work on dispersal indicates that haddock aggregations are unlikely to remain in areas for sufficient time to justify permanent fishery closures