Predator-prey relations at a spawning aggregation site of coral reef fishes

Abstract

Predation is a selective force hypothesized to influence the spawning behavior of coral reef fishes. This study describes and quantifies the predatory activities of 2 piscivorous (Caranx melampygus and Aphareus furca) and 2 planktivorous (Melichthys niger and M. vidua) fishes at a coral reef fish-spawning aggregation site in Johnston Atoll (Central Pacific). To characterize predator-prey relations, the spawning behavior of prey species was quantified simultaneously with measurements of predatory activity, current speed and substrate topography. The activity patterns of piscivores was typical of neritic, daylight-active fish. Measured both as abundance and attack rates, predatory activity was highest during the daytime, decreased during the late afternoon, and reached a minimum at dusk. The highest diversity of spawning prey species occurred at dusk, when piscivores were least abundant and overall abundance of prey fishes was lowest. The abundance and predatory activity of the jack C. melampygus were positively correlated with the abundance of spawning prey, and therefore this predator was considered to have a flexible prey-dependent activity pattern. By contrast, the abundance and activity of the snapper A. furca were generally not correlated with changes in abundance of spawning fishes. Spawning prey fishes were more common over substrates with complex topography, where refuges from piscivores were abundant. Piscivores differentially selected group-spawning species during spawning rushes over pair-spawning and nonspawning fishes. Overall attack rates by piscivores on adult spawning fishes were higher than by planktivores feeding on recently released eggs. The triggerfishes M. niger and M. vidua fed most actively at dusk and selected as prey those species of reef fishes that produced eggs of large size.KEY WORDS: Predator-prey interactions · Predation · Piscivory · Planktivory · Spawning · Coral reef fishes Resale or republication not permitted without written consent of the publisher

Selection of a spawning aggregation site by Chromis hypsilepis (Pisces: Pomacentridae): habitat structure, transport potential, and food availability

“…Spawning fishes have a greater susceptibility to predation because their attention to courtship and spawning activities can reduce their awareness of potential predators (Candolin & Voigt 1998, Sancho 2000. Increased habitat rugosity reduces the risk of predation on fishes (Hixon & Beets 1993), and other studies have shown a relationship between increased rugosity and spawning site selection (Sabo & Orth 1994, Sancho et al 2000a.…”

“…For example, distinctive physical structures at these sites may act as a visual signal to assemble individuals that are widely dispersed outside the spawning season (Moyer & Zaiser 1981). Aggregation sites may provide a reduced risk of predation for spawners because of some unique habitat attributes (Sancho et al 2000a). The most widely applied hypothesis for the selection of spawning sites by aggregative and non-aggregative species is that currents at the site favour the rapid transport away from the reef of newly fertilized eggs and hatching larvae (the off-reef transport hypothesis).…”

Breeding season, spawning time, and description of spawning behaviour in the Japanese ornate dragonet, Callionymus ornatipinnis: a preliminary field study at the northern limit of its range

“…Spawning at dusk invokes a variety of benefits for both offspring and spawning adults (e.g., Johannes 1978;Lobel 1978;Thresher 1984b;Sancho et al 2000a). From the offspring's perspective, low levels of feeding activity by planktivores at dusk may reduce egg predation (e.g., Johannes 1978;Lobel 1978; but see Sancho et al 2000b) and thus promote the transport of eggs off the reef during night. On the other hand, from the perspective of spawning adults, spawning at dusk may decrease the risk of predation because piscivores are also likely to be inactive at dusk (Sweatman 1984;Sancho et al 2000b; but see Hobson 1972;Lobel 1978).…”

“…From the offspring's perspective, low levels of feeding activity by planktivores at dusk may reduce egg predation (e.g., Johannes 1978;Lobel 1978; but see Sancho et al 2000b) and thus promote the transport of eggs off the reef during night. On the other hand, from the perspective of spawning adults, spawning at dusk may decrease the risk of predation because piscivores are also likely to be inactive at dusk (Sweatman 1984;Sancho et al 2000b; but see Hobson 1972;Lobel 1978). Predation avoidance by both adults and offspring might therefore account for spawning at dusk in C. ornatipinnis, although this would seem to be difficult to prove.…”

Ecological correlates of population density and behavior in the circumtropical black triggerfish Melichthys niger (Balistidae)

“…These data are among the first to suggest the possibility of growth limitation in oceanic island fish populations. Furthermore, since there are conflicting published reports of the trophic position of M. niger from different locations (Randall 1967;Aiken 1975;Sancho et al 2000;Sazima et al 2003), we establish whether these populations differ obviously in diet and in condition. Published accounts of density and distribution of this species are then discussed in relation to ecological and life history factors.…”