Daily Activity

The time of day can be very important in determining the species that are present in front of the video cameras. Some reef fish species may be closely associated with the reef structure and not move far from it, other species may spend most of their time swimming higher in the water column or foraging out over the adjacent sand bottom. Open water species, such as scad, might use the reef for shelter during times of the day, when large predators are feeding. During the daylight hours in November, 2002, a predictable change occurred in the fish assemblage near the bottom habitats. Relatively tranquil schools of juvenile fish seemed to predominate early and late in the day. Sometime shortly after mid-day, swarms of scad appeared near the bottom, often in frenzied swimming. The scad were followed by schools of blue runner, which were often present for less than an hour.