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NOAA Technical Memorandum NMFS-AFSC-333

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Reconciling ambiguity resulting from inconsistent taxonomic classification of marine fauna assessed in the field: Querying a database to reclassify by lowest accountable inclusive taxon (LAIT)


Marine areas such as the eastern Bering Sea (EBS) continental shelf contain such significant commercial and ecological resources that it demands our careful stewardship to maintain them. This requires developing a comprehensive knowledge of the ecosystems involved, which in turn requires in-depth, long-term investigations to elucidate and quantify the biotic and abiotic elements, and the relationships among them, that make up these systems and enable their productivity. Accurate assessment of taxonomic diversity and the composition of communities and or biotopes is instrumental. Accordingly, the benthic fauna of the EBS are the subject of annual bottom trawl surveys of the continental shelf conducted by the National Oceanic and Atmospheric Administration (NOAA), Alaska Fisheries Science Center (AFSC), Resource Assessment and Conservation Engineering (RACE) Division. These surveys comprise a time series of data collected from 1982 to 2015, employing standardized gear and sampling methods for consistency over the period.

The region surveyed is an area of the shelf from the Alaska Peninsula and Aleutian archipelago on the south to about 62° N lat., and from the Alaska coast to the shelf break. It comprises roughly 480,187 km2, spatially represented by 376 trawl sampling stations distributed throughout. Each station’s catch is sorted by taxon, weighed, and individuals counted. Abundance is indexed by catch amount per area swept by the net. The data are entered into an Open Database Connectivity (ODBC) database maintained by RACE. Biomass has averaged 1,429 kg per haul since 1982, with invertebrates constituting roughly 22% of the total. A total of 227 taxa of vertebrates and 624 of invertebrates have been identified and reported. Identifying and classifying catch on a survey of such scope is a formidable task. Certain anomalies and ambiguities occur in the historical data from the survey. Inconsistent resolution in identifying individuals of a given species to the lowest hierarchical level practicable is apparent in the data. To mitigate such problems, this paper presents a query system for objectively transforming the invertebrate catch data from the survey into an unambiguous, consistent, usable form: the reclassification of taxonomic data to lowest accountable inclusive taxon (LAIT). For a given taxon in a dataset, the LAIT is that taxon also reported therein which by definition includes the given taxon and which itself is not defined as a subtaxon of another reported taxon. When subtaxa are thus consolidated, all LAITs unambiguously account for the invertebrate catch (albeit with possible minor loss of taxonomic resolution), without the chance of incorrect assessment of the catch of a reported lower-level taxon when the latter is also present among catch identified only to a higher level, inclusive taxon.

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