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Chapter 9 - Large Pelagic FishNorthwest Atlantic Distribution and ImportantAreasMethodsTo understand the distribution of pelagic fish target speciesrelative to the Northwest Atlantic and identify criticalsites, the following questions were addressed:• Where are the greatest areas of co-occurrence?(richness of target species)• Where are the most important areas for essentialfish habitat?• Where has the species been found consistently overtime? ( persistence)Observation data were provided by NMFS. This data iscompiled from numerous sources, including cooperativetagging programs, mandatory logbook reporting for somefisheries, recreational surveys, and published literature.Approximately 96% of the data points originated from twofisheries-dependent tagging programs: the CooperativeTagging System run by Southeast Fisheries ScienceCenter, and the Cooperative Shark Tagging Program runby Northeast Fisheries Science Center, the two most comprehensivelong-term data sets available. The data providestagging, and recapture information when available,from tagged individuals, and is given as point locations,with year information associated. A detailed descriptionof the data sources is provided on pg. 10-3 of the HMSdocument, 2006 Final Consolidated Atlantic HighlyMigratory Species Fishery Management Plan. Data wereprovided in a summarized form by ten minute squares(TMS), where each square contained multiple surveypoints by life stage and was binned by decade (1965-1974;1975-1984; 1985-1994; and 1995-2004). Because this assessmentexplores ecologically important areas within aset boundary, we analyzed gridded points within the studyarea or within a buffer, extending out to 1500m depth, to4000m. In the southern area of the Northwest Atlantic,we extended a circular buffer of equivalent spatial scale.At the surface, this equated to 110 km.Essential fish habitat (EFH) polygons were obtained fromthe NMFS website, while the sandbar shark EFH wasprovided by HMS upon request. Source data for EFHpolygons (currently being updated by NOAA) were compiledand mapped for the 1999 HMS FMP by NOAAFisheries, Office of Habitat Conservation and the HighlyMigratory Species Division. EFH polygons were availablefor juvenile and adult life stages for all target species, withthe exception of the sand tiger (adult only). Neonate polygonswere only available for dusky shark, porbeagle, sandtiger, sandbar shark, shortfin mako, swordfish (larvae),and thresher.Data limitationsComprehensive fishery-independent surveys of the studiedspecies are not currently available. The data used inthis analysis is derived primarily from fisheries-dependenttagging data, and fishing effort varies considerablythroughout the region and likely through time. As wewere not able to correct for the bias imposed by variablefishing efforts, true abundances could not be determinedfrom this data, and consequently, we focused on metricsthat are less sensitive to fishery bias.Data AnalysisRichness of target species: To outline the diversity of targetspecies at particular points in space, the number of targetspecies observed within a TMS was summed and mappedbased on all available data (1965-2004). Maps were createdfor total number of targets and by age class (wheredata was available). The darkest colors on the map indicatethe areas with greater numbers of target species or targetspecies within an age classPersistence: The persistence score refers to the consistencywith which a target species was observed in the same generalarea (TMS) over time. For this calculation, we combinedjuvenile and adult observations as an indicator thatthe species was present. The persistence score was calculatedby summing the number of decades that a given targetspecies was recorded (e.g. one decade = 1, four decades= 4). The darkest colors indicate areas where target specieswere consistently observed over all decades.9-Northwest Atlantic Marine Ecoregional Assessment • Phase 1 Report