Fishery applications of optical technologies

The optics of the ocean are very different from those of the atmosphere. Light is much more strongly absorbed and scattered. Despite the difficulties, optical systems have been widely applied in fishery research and management. These applications include, but are not limited to: abundance surveys using video and still cameras, airborne lidar (light detection and ranging), supporting data for acoustic measurements, behavioural studies, observations of fishery operations, and habitat classification. New applications are continually being developed and made possible by the array of optical technologies available. Many use simple digital still or video cameras. For operation at depths greater than a few tens of metres, where there is little ambient light, low‐light‐level cameras and artificial lighting are often used. Lasers have found application in a number of configurations, including airborne lidars that operate like vertical echosounders, holographic cameras, and laser‐imaging systems designed to increase image contrast in the presence of scattering in the water. There are a number of practical factors that affect the performance of optical systems. These include the capability of the platform, geolocation, data processing, metadata, calibration, and of course estimate of measurement uncertainties.