Case Study 10 Use of Night Satellite Imagery to Monitor the Squid Fishery in Peru

The giant squid (Dosidicus gigas) lives mainly in the oceanic environment, but also occurs in neritic (relatively shallow) environments, and makes horizontal and vertical migrations. It is a physiologically tolerant species, characterized by opportunistic consumption habits and is also considered an ecologically important species, acting as predator and prey of a large number of species (including their own species). The distribution of Dosidicus gigas is far reaching since it is a highly migratory species. In the eastern Pacific Ocean its geographic habitat is from California (37◦N) to southern Chile (47◦S) and from the coasts of North and South America to 125◦W. The greatest concentrations are located in the Peruvian coastal oceanic region in the southern hemisphere, and the Gulf of California in the northern hemisphere (Nesis, 1983). In Peru, the fishing activity of the giant squid or "pota" is exerted mainly by industrial Japanese and Korean squid jigging vessels with a holding capacity of 300–1000 tonnes, which have been fishing off Peru since 1991 (Taipe, 2001). The squid jigging vessels operate at night, using powerful lights (2000 watts) to attract the squid. The lights are set at a specific height and angle to allow for a shade zone next to the ship where the squid concentrate. The number of lights per ship varies between 120 and 200 depending on vessel capacity. Squid are attracted to the light, creating massive concentrations around the luminous source, and allowing for easy harvest. These lights can be observed as bright-light areas on night-time OLS (Operational Linescan System) images of the Defense Meteorological Satellite Program (DMSP). Cho et al. (1999), Kiyofuji et al. (2001), Rodhouse et al. (2001) and Waluda et al. (2002) have examined night-time visible images to determine the spatial distribution of fishing vessels. Cho et al. (1999) and Kiyofuji et al. (2001) determined that the bright areas in the OLS images, created by 2-level slicing, were caused by light