Species Mapping Lindsay N. K. Davidson Sawfish distribution maps were created based on a combination of data sources including encounter databases, museum archives, literature searches, and expert judgement. Before expert consultation, maps for the five species were created using two databases: International Sawfish Encounter Database (Page 77) and data from the National Marine Fisheries Service. This data was based on sightings from between 1782 and 2011 and had 8,530 records. These data included taxonomic nomenclature of eleven sawfish species, which were reconciled with current taxonomic names. Expert opinion on the distribution of each sawfish species was collated at the Sawfish Workshop. Each map was presented to the group, and the presence status for each species was discussed. Four presence codes were used: Extant (the species is known, or thought very likely to occur presently in the area), Probably Extant (a species presence is considered probable, either based on extrapolations of known records, or realistic inferences), Presence Uncertain (the species was formerly known or thought very likely to occur in the area but it is no longer known whether it still occurs), and Possibly Extinct (the species was formerly known or thought very likely to occur in the area but it is most likely now extinct from the area).
The historical range of a species is defined as the sum of all portions of the range regardless of presence code. Based on the ecology of sawfishes, it was assumed that the sawfish depth range was no deeper than 100m and that the geographic range area calculations are therefore bounded by the 100m depth contour and summarised as the area occupied by each presence code expressed as a proportion of the total (historic area). For visualization purposes, the resulting maps were drawn out to extent of Exclusive Economic Zone (EEZ; 200 nautical miles from the coastline). Therefore, these maps are an overestimation of the range area. Some countries have EEZs connected to offshore islands. These areas were ‘clipped’ or removed from a species range. Consequently, islands such as Fernando de Noronha off Brazil, Lord Howe Island off New South Wales in Australia, and San Antonio off Equatorial Guinea, were removed from the range maps.
8,530 records (with both a country and year) spanning 92 countries and more than two centuries.
Species richness maps Species richness maps were created using a hexagonal grid of cell size 23,322 km2 covering the range of all sawfish species (mapped to the EEZ scale). The four presence codes for each species were counted within each cell. Historic species richness was determined by the count of species present per cell, regardless of current presence code).
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