The EcoWB GIS Program is assisting Dr. Jens Hegg of the University of Idaho on a project investigating the migration patterns of Largetooth Sawfish (Pristis pristis). Dr. Hegg’s project utilizes chemical analyses of bony structures (including rostral teeth) from specimens accidently killed as fishing bycatch to assess habitat affinities across different life stages, with the goal of reconstructing movement patterns to better understand and conserve this critically endangered species. The EcoWB GIS Program is assisting this project by assembling a GIS database that includes water depth, temperature, and salinity within the study area (Fig 1).

Study area used to create the GIS model.

Figure 1. The study area includes riverine and shallow coastal areas within the shaded box.

Depth data will be provided by the General Bathymetric Chart of the Oceans (GEBCO) database, with possible supplementation with digital navigation charts provided by the Brazilian Navy. Water surface temperature data will be generated through analysis of Landsat 8 Thermal Infrared Sensor (TIRS) imagery, based on the methods outlined by Vanhellemont (2020). Work is ongoing to identify an adequate method of collecting high-resolution salinity data. To account for seasonal and yearly variation in temperature and salinity, separate maps will be produced for the wet and dry seasons for each variable, based on 5 years of averaged data (with at least 2 records per season per year). These data, when combined with Dr. Hegg’s chemical isotope analyses, will shed important light on the movements and critical habitats of this endangered and little-known species.

References:

Vanhellemont, Q. 2020. Automated water surface temperature retrieval from Landsat 8/TIRS. Remote Sensing of the Environment 237: 111518

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