Behavioral observations of an upcurrent reef colonization event by larval surgeonfish Ctenochaetus strigosus (Acanthuridae)

We visually censused fishes along transects on the back-reef and adjacent lagoons of bank-barrier reefs at 6 sites on St. Croix, US Virgin Islands, to determine the extent to which coral reef fishes use lagoon habitats as nurseries. Fishes were recorded by size class (small, < 3 cm; medium, 3 to 5 cm; large, > 5 cm) on the back-reef, and on 5 lagoon habitat types: patch-reef, rubble, seagrass, algal plain, and sand. We examined densities of 4 focal 'species' (Acanthurus spp. [A. bahianus and A. chirurgus], Haemulon spp. [all species of the Haemulon genus], Sparisoma aurofrenatum, and Scarus iserti), and densities of all species combined to determine spatial and temporal patterns of habitat use. Although there was a general tendency for coral reef fishes to use lagoon habitats as nurseries, we discerned 2 patterns of habitat use: 1 group, exemplified by Acanthurus spp. and Haemulon spp., use lagoon patch-reef and rubble as nurseries in preference to back-reef and other lagoon habitats; in contrast, Sparisoma aurofrenatum and Scarus iserti preferentially use back-reef and, to a lesser extent patch-reef, as nursery, juvenile, and adult habitat. Temporal variation was greatest in the small size class and least in the large size class. Most settlement occurred during summer, which is when settlement in lagoon habitats was greatest, with a little settlement in winter in the back-reef habitat. For species that use lagoons as nurseries, lagoon habitats must provide advantages that offset the additional energy expense and predation experienced by both incoming larvae, as they cross over the reef and search for patch-reef and rubble, and juveniles, as they return to the reef during the juvenile-to-adult transition. Given the use of lagoon habitats as nurseries, there is a need for inclusion of lagoons in coral reef reserves.

Section: Discussionmentioning

confidence: 82%

Use of back-reef and lagoon habitats by coral reef fishes

Adams

Ebersole²

2002

“…During this period there is the potential for high mortality rates and exposure to strong currents. At this stage there is likely to be strong selective pressure for well developed locomotor capabilities as the fish avoid reefbased predators whilst locating suitable settlement sites (Sancho et al 1997). It may also be noteworthy that the highest relative swimming speeds were observed in Amphiprion malanopus, a species with a relatively short pelagic larval duration.…”

Section: Resultsmentioning

confidence: 99%

Relative swimming speeds in reef fish larvae

Bellwood¹,

Fisher²

2001

Although smaller animals move more slowly than larger animals (Alexander 1982), their relative speed in body lengths per second (bls -1 ) is almost invariably higher. In terrestrial systems, vertebrate offspring are relatively large at the onset of independent locomotion. Only in aquatic vertebrates can we see diminutive individuals capable of independent locomotion. While reef fish larvae have been assumed to be poorly developed and capable of only limited movement (Williams et al. 1984, Roberts 1997, recent works have highlighted the potential impact of active movement in shaping dispersal patterns and settlement success (Armsworth 2000, Cowen et al. 2000. These latter studies incorporate information on the remarkable swimming performance of late stage larvae of coral reef fishes, with long-term sustained swimming bouts covering the equivalent of up to 140 km, and short-term sustained swimming speeds of up to 65 cm s -1 (Stobutzki & Bellwood 1994, 1997, Leis & Carson-Ewart 1997. These swimming speeds appear to be quite extraordinary; however, they have not yet been compared to other fishes in terms of their relative swimming speeds.Studies investigating the swimming abilities of tropical reef fish larvae have concentrated almost entirely on the oldest larval stages. This reflects the limitations of the light traps which are commonly used to catch larvae for behavioural experiments (Choat et al. 1993). These larvae are at a relatively advanced state of development. We set out to determine: (1) whether the swimming ability exhibited by late pelagic stage individuals is exceptional or simply a reflection of the small size of reef fish larvae, and (2) how the relative swimming speeds of larvae are influenced by developmental stage. We selected 3 study species that varied in size at settlement and rate of development, and used captive breeding techniques to conduct swimming trials throughout the developmental period of each species (following Fisher et al. 2000).Materials and methods. Three species of reef fish were examined: Pomacentrus amboinensis (Pomacentridae, Pomacentrinae), Amphiprion melanopus (Pomacentridae, Amphiprioninae) and Sphaeramia nematoptera (Apogonidae). These species differ considerably in their age and size at settlement. P. amboinensis and S. nematoptera have long larval durations of 20 and 24 d and settle at approximately 15 and 13 mm total length (TL), respectively. In contrast A. melanopus has a very short larval duration of approximately 9 d and settles at ~7 to 8 mm TL. Rearing methods follow . Swimming experiments were carried out throughout the larval period of each species using swimming flumes following Stobutzki & Bellwood (1997) and Fisher et al. (2000). Three batches of young from each species were used in the swimming trials. At each experimental age, 8 to 12 fish were taken from each batch (without replacement) and the fastest individual swimming speed recorded (as U crit ; see below). Maxima rather than means were used to provide estimates of maximum swimming speeds. If larvae a...

“…Substrate composition consists of a mix of live tabular coral formations dispersed among dead coral boulders and fine rubble. Currents at the reef channel are bi-directional, influenced by both tides and waves (Sancho et al 1997.…”

Section: Methodsmentioning

confidence: 99%

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

Sancho¹,

Petersen²,

Lobel³

2000

Self Cite

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