Comparative analysis of foraging and habitat use by the sympatric Caribbean parrotfish Scarus vetuta and Sparisoma viride (Scaridae)

Abstract

On the fringing reef of Bonaire, Netherlands Antilles, a comparative study was made of habitat use, diet selection, foraging behaviour and food acquisition of the parrotfish species Scarus vetula and Sparisoma vinde. The species are sympatric and hve in the same reef habitats (depth zones). Both species show similar foraging selectivity, but exploit algal resources differently. Preferred food items are turf algae on substrates infested with endolithic algae, whereas crustose corallines are avoided. Foraging preferences are related to yield, i.e. the amount of AFDW (ash-free dry weight), protein and energy that can be harvested per bite. Foraging behaviour differs between the species. S. vetda takes more bites in long forays, has higher bite rates (no. of bites S-'), and makes fewer and smaller scars on grazing substrates than S. viride. Furthermore, S. vetula prefers flat substrate surfaces while adult S. viride graze by preference on concave surfaces. Species-specific differences in preference and utilization of grazing substrates are related to feeding mode. S. vetula employs a scraping feeding mode by which mainly epilithic algae are ingested. In contrast, S. viride is an excavating grazer that ingests large amounts of endolithic and crustose algae. Intake and assimilation of algal AFDW, protein and energy were quantified through a combination of laboratory feeding trials and field observations. S. vetula has lower food intake (mg AFDW bite-') than S. vin'de (0.8 X I O -~ X fish wet wt, FWW, and 2.3 X I O -~ X FWW respectively), resulting from smaller (shallower) bites. Assimilation efficiencies of total AFDW, protein and energy by S. vetula were higher than in S. viride grazing on the same dead coral substrates. In spite of different feeding modes and different fractions of the primary production harvested, daily amounts of assimilated nutrients and energy are similar for both species, resulting from higher feeding rates (no. of bites h-') and higher assimilation efficiency in S. vetula.

Live coral predation by parrotfishes (Perciformes: Scaridae) in the Abrolhos Bank, eastern Brazil, with comments on the classification of species into functional groups

“…guacamaia and Sc. vetula were rarely recorded feeding on live corals (Frydl, 1979;Bruggemann et al, 1994b;Bruckner & Bruckner, 1998;Miller & Hay, 1998;Rotjan & Lewis, 2006). In the present study adult Sc.…”

“…viride) by Reyes-Nivia et al (2004) (between 1.83 and 3.51 cm 2 ), but similar to the estimate obtained for Sp. viride by Bruggemann et al (1994b) (about 0.60 cm 2 for individuals with 45 cm TL). Differences between results from these studies are probably not related to actual differences in the size of bites from Sp.…”

“…viride and Sp. amplum, but to differences in the methodologies used, since in the study of Reyes-Nivia et al (2004) the greatest values of length and height measured directly in the field were used (thus possibly overestimating bite size) while in the study of Bruggemann et al (1994b), as well as in this study, all contours and irregularities of each scar were considered.…”

Tradeoffs between fisheries harvest and the resilience of coral reefs

“…The 30-cm threshold is beneficial for the reef as well as for the fishery yield because the fishery removes fewer, albeit larger, fishes, thus sustaining higher grazing rates for a similar catch. This benefit occurs even though larger-bodied fish have greater per capita grazing impacts (22,34,36), implying that the greater abundance of fish compensates for the targeting of the largest individuals.…”

Limited flexibility in resource use in a coral reef grazer foraging on seasonally changing algal communities

“…Indeed, production and nutritional quality in turf algal communities increases through the morning reaching its peak at noon (Bruggemann et al 1994a;Zemke-White et al 2002). In the southern Red Sea, S. ferrugineus seems to respond to the low nutritional quality of turfs in the morning both by lower feeding rates (Y.A., pers.obs.)…”