Tidal flat observation and monitoring using still video and network cameras

Tidal flats have important roles in a coastal ecosystem as a habitat for benthic infaunal species, including commercial bivalves, and as a feeding ground for migratory species of fish and birds. Migratory species have a significant effect on the infaunal species abundance by predation. Therefore, it is important to know the type of migratory species and how often they appear on the flat. It is also important to know the abundance of commercially available and/or endangered migratory fish species (e.g., the Japanese eel). We tried to observe the migratory species on the tidal flats by using time-lapse still, infrared video, and network cameras to understand their dynamics. Commercially available cameras and hand-made underwater camera housing were used to reduce the equipment cost as low as possible. These camera observations could reveal the species composition of fish, presence of the Japanese eel, and appearance of ducks during winter on tidal flats. However, comparing the spatio-temporal difference in their abundance is difficult because underwater visibility differed among sites, and bio-fouling to the camera housing disturb the long term observation. Further impovements, such as the area estimation of the captured image and anti-bio-fouling mechanisms, are required in the future research to monitor the abundance of migratory species in tidal flats.