Abundance and distribution of nocturnal fishes over a coral reef during the night

Abstract

Coral reefs are characterized by high abundance of fishes, which often have marked effects on the recruitment, nutrition, and reproduction of coral reef inhabitants. Despite the fact that fish are active over the coral reef at night, very little is known of their whereabouts or about their contribution to those processes. In the present study, the abundance and distribution of nocturnal fishes were studied over a coral reef near Eilat, Red Sea. Sampling was conducted between the surface and 15 m depth, using a stereoscopic camera system that surveyed 3.5 m 3 of water every 2 min. The density of zooplanktivorous species ranged from 0.7 to 7.4 fish 100 m -3, accounting for > 60% of the total nocturnal fishes recorded. Fish abundance decreased with increasing distance from shore and with increasing height above bottom. Larger fish foraged at greater heights above bottom. While the appearance of zooplanktivorous fishes after sunset and their disappearance before sunrise corresponded to that of demersal zooplankton, inter-night variation in fish abundance was unrelated to variation in zooplankton abundance. Furthermore, neither current speed nor moon illumination accounted for inter-night variations in fish abundance, perhaps indicating some degree of site fidelity. The abundance of zooplanktivorous fishes was ~30-fold lower during the night than day. However, since nocturnal fishes feed on larger zooplankters, the biomass of zooplankton preyed upon by nocturnal fishes was similar to that of diurnal species. This study suggests that the paradigm of negligible predation by nocturnal fishes should be reconsidered.

Near-surface enrichment of zooplankton over a shallow back reef: implications for coral reef food webs

“…Planktivorous fish are a major component of coral reef communities both day and night (Hobson 1991;Holzman et al 2007). Most diurnal planktivores, including pomacentrids and planktivorous triggerfish (Balistidae) feed primarily on copepods (reviewed by Hobson 1991) which we found to be highly concentrated near the surface.…”

The lunar cycle determines availability of coral‐reef fishes at fish markets

“…Diminished illumination at the end of the day triggers diurnal fishes to hide and nocturnal fishes to leave their daytime shelters (Jennings et al , 1999; Holzman et al , 2007). Light reflected by the moon may actually hamper these triggers.…”

Life cycle differences between two species of genus Pempheris based on age determination around Okinawa-jima Island

“…In many cases, however, such data are still not enough. Holzman et al (2007) showed the importance of nocturnal zooplanktivorous fish that connect lower-order and higher-order consumers. In addition, they indicated that the biomass of the nocturnal fishes is almost the same as that of diurnal fishes.…”