Dictys Cretensis et Dares Phrygius De bello et excidio Trojae ... /

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Food choice in Siganus fuscescens: influence of macrophyte nutrient content and availability

Using multiple-choice feeding experiments, the selection of six species of macrophytes by the herbivorous rabbitfish Siganus fuscescens was examined. The rabbitfish showed distinct food choice in the laboratory; however, selection of macrophytes by S. fuscescens was not related to their absolute nutrient content (nitrogen, carbon, energy and ash free dry mass). Nutrient assimilation estimates showed that the macrophytes which were most preferred were those that S. fuscescens assimilated best. In S. fuscescens, the macrophytes that were preferred passed through the gut significantly faster than the less preferred species. Gut transit time had a significant effect on the absolute value of a food item in terms of net nutrient gain per unit time. This study showed that food value could be inferred from the absolute nutrient content of the macrophytes. Thus both the ability to assimilate nutrients as well as the absolute nutrient content of macrophytes must be quantified when assessing food value. (C) 2004 The Fisheries society of the British Isles.

Density-Dependent Effects of Coral Reef Restoration on Herbivory and Community Interactions

Coral reefs are among the most productive ecosystems in the world. Yet, with their recent declines due to disease, climate change, and overfishing, restoration of these habitats is one of the main concerns for ecologists, resource managers, and government organizations. Coral reef restoration aims to promote key ecosystem processes to shift these habitats to their historical state of high coral cover, but few studies have focused on effective ways to promote resilience. In addition, little is known about the impact of restoration on the fish communities. The aim of this study is to understand how the community of herbivorous fishes is affected by the density of coral outplants inside a special protection area located in the Florida Keys National Marine Sanctuary. Grazing rates, number of visits and time spent foraging were compared using video footage of sites previously devoid of corals, and six months after coral restorations had occurred. Coral transplantations did not appear to attract herbivores nor increase grazing rates of fishes. Instead Sparisoma and Acanthurus fishes appear to respond to changes in the environment by modifying their grazing behavior. However, there was an observed increase in visits by Acanthurus species after transplantation for all the sites sampled within the reef. These fishes seemed to prefer low coral cover sites for grazing. This study highlights the importance of examining coral restorations impacts at the community level. Understanding how restoration influences herbivores and other guilds of reef fishes will allow individuals to not only determine if these habitats are returning to their “original” state, but provide more information on the ways these systems cope with changes in the environment.

Spatial behavior of two coral reef fishes within a Caribbean Marine Protected Area

A better understanding of the key ecological processes of marine organisms is fundamental to improving design and effective implementation of marine protected areas (MPAs) and marine biodiversity. The movement behavior of coral reef fish is a complex mechanism that is highly linked to species life-history traits, predation risk and food resources. We used passive acoustic telemetry to study monthly, daily and hourly movement patterns and space use in two species, Schoolmaster snapper (Lutjanus apodus) and Stoplight parrotfish (Sparisoma viride). We investigated the spatial overlap between the two species and compared intra-specific spatial overlap between day and night. Presence-absence models showed different diel presence and habitat use patterns between the two species. We constructed a spatial network of the movement patterns, which showed that for both species when fish were detected by the array of receivers most movements were made around the coral reef habitat while occasionally moving to silt habitats. Our results show that most individuals made predictable daily crepuscular migrations between different locations and habitat types, although individual behavioral changes were observed for some individuals across time. Our study also highlights the necessity to consider multiple species during MPA implementation and to take into account the specific biological and ecological traits of each species. The low number of fish detected within the receiver array, as well as the intraspecific variability observed in this study, highlight the need to compare results across species and individuals to be used for MPA management.