MEPS 553:203-217 (2016)  -  DOI: https://doi.org/10.3354/meps11754

ABSTRACT: Understanding the persistence of fish aggregations is essential for the development of spatial fisheries measures and marine spatial planning advice. This study examined the temporal persistence of haddock Melanogrammus aeglefinus aggregations and life-stage sensitivity to environmental 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 that 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 significant age-related differences in temperature, depth, salinity and sediment preference. Depth explained the largest deviance in abundance models for most age-classes and seasons, but it was difficult to disentangle the relative contribution of this factor and salinity to habitat preference. The density of age 1 haddock indicated a preference for coarse sands in the winter and spring, which may 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 region of the northern North Sea. Moreover, this habitat is predicted to decrease in the following decades. 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.

KEY WORDS: Nursery areas · Haddock · Niche · GAMs · Distribution models