The Gulf of Maine–Georges Bank Atlantic herring ( Clupea harengus): spatial pattern analysis of the collapse and recovery of a large marine fish complex

Spatial patterns of the Gulf of Maine–Georges Bank Atlantic herring ( Clupea harengus) complex were evident at three levels of resolution from analyses using bottom trawl survey data from spring 1968 to 1998 and autumn 1963 to 1998. The geographic range of the complex contracted significantly during 1973–1985 in both spring and autumn, coincident with major declines in abundance following the distant water fleet fishery during 1961–1976. Following recovery in abundance, distribution patterns that were previously observed were re-established. Medium scale patterns (e.g., 50–200 km) in the data suggest that herring were not uniformly distributed over the continental shelf during spring and autumn, but rather aggregated in sub-groups within the range of the entire complex. Fine scale patterns in the survey data (5–50 km) suggest that herring maintained pre-collapse behavioral relationships even though the stock complex had declined by ∼85%. Among-site distances between the herring schools, presumably from the Gulf of Maine spawning component, remained remarkably constant as the Georges Bank and Nantucket Shoals spawning components were extirpated. As the complex recovered, it appeared that more and perhaps larger schools of herring were present. These analyses suggest that a fully-recovered stock complex has distributional characteristics and patterns that can be monitored and quantified. Quantification of spatial patterns may have important consequences for assessment, stock identification, and fishery management.