Terminal lakes are lakes with no hydrologic surface outflows and with losses of water occurring only through surface evaporation and groundwater discharge. We quantified the extent of the littoral zones (areas where 1% or more of surface irradiation reaches the lake bottom) and open water zones (areas where less than 1% of surface irradiation reaches the lake bottom) in 18 terminal lakes. Additionally, we quantified habitat usage and diets of the fish species inhabiting these lakes. This dataset contains includes seven lakes from North America (Atitlan, Crater, Eagle, Mann, Pyramid, Summit, Walker), one from South America (Titicaca), five from Eurasia (Caspian, Issyk-Kul, Neusiedl, Qinghai, Van), and five from Africa (Abijatta, Manyara, Nakuru, Shala, Turkana).

Measurements of the surface areas of the littoral and open water zones were performed using ArcGIS Pro Version 2.9. First, we generated year-specific digital elevation models (DEMs) of the lake’s bathymetry by a) using existing bathymetry raster data or b) by digitizing published depth contours of the lake’s bathymetry and interpolating a bathymetry raster using a natural neighbor interpolation. For several lakes that showed significant changes in lake level and where data regarding lake level change were available, we were able to produce a second year closer to the present by using the Raster Calculator function in ArcGIS Pro and then clipping the bathymetry raster to the lower lake level. This was possible for 5 of the 18 lakes (Mann Lake, Eagle Lake, Lake Abijatta, Walker Lake, and Lake Turkana), allowing us to map changes in the littoral zone size between the two years. For the lakes containing two years of data, we used only the most recent year in all subsequent analyses. We defined the portions of the littoral zone of the lake as the portions where the intensity of photosynthetically active radiation (PAR) reaching the lake bottom is 1% or greater relative to the intensity at the surface. For lakes where 1% PAR depth was not published, we calculated 1% PAR depth from published light profiles using the Lambert-Beer Law: 0.01 = e^-u*z where µ is the light attenuation coefficient (meters^-1) and z is 1% PAR depth (meters). For lakes where neither 1% PAR depth nor light profiles were published, we approximated the 1% PAR depth by multiplying the Secchi depth of the lake by a coefficient of 2.5. We sought the most recently collected Secchi depth to make these calculations. We then used the Raster Calculator function in ArcGIS PRO 2.9 to determine the portions of the lake where depth was less than or greater than the 1% PAR depth to map the open water and littoral zones, respectively.

Fish species inventories and information regarding each species’ habitat and diet was compiled from 1) published peer-reviewed primary literature, 2) non-peer-reviewed literature (books, reports by government agencies or private firms), 3) online databases (i.e., FishBase (https://www.fishbase.de/home.htm), California Fish Website (www.calfish.ucdavis.edu)), and/or 4) experts studying the ecology of the species or lake ecosystem. We employed a conservative view regarding species taxonomy (i.e., ‘lumping’ rather than ‘splitting’). We classified species’ habitats with respect to three categories: 1) littoral zone (occurring in parts of the lake where 1% or more of the surface radiation reaches the lake bottom), 2) open water zone (occurring in parts of the lake where less than 1% of the surface radiation reaches the lake bottom), and 3) littoral & open water zone (occurring in both lake zones). These habitat classifications were based on adult habitat use only, and habitat use during larval and juvenile stages was not considered. We classified diets with respect to seven categories: 1) plankton only, 2) periphyton only, 3) periphyton and macroinvertebrates, 4) periphyton, macroinvertebrates, and plankton, 5) periphyton, macroinvertebrates, and fish, 6) fish OR fish and plankton, and 7) fish, plankton, periphyton, and macroinvertebrates.

The fish habitat and diet data (All_Lakes_Fish_Data.csv) can be opened with any program capable of reading .csv files (e.g. Microsoft Excel). The GIS files can opened with any software capable of opening GIS files (e.g. ArcGIS Pro, QGIS, Google Earth).