Response of herbivorous fishes to crown-of-thorns starfish Acanthaster planci outbreaks. II. Density and biomass of selected species of herbivorous fish and fish-habitat correlations

Abstract

Density, biomass and fish-habitat correlations were estimated for selected species of herbivorous fish on crown-of-thorns starfish (COTS) impacted and control reefs in the central Great Barrier Reef. The objective was to investigate a long-term numerical and/or biomass response to increased food availability (algal turfs) on COTS affected reefs. Out of 14 variates investigated, 2 showed evidence of a numerical response on COTS affected reefs. Importantly, total number of individuals and total biomass showed no response. Instead, a negative effect (i.e. higher abundances on control reefs) was detected for Zebrasoma scopas, although thls was attributable to very high abundances on one of the non-impacted reefs (Coil). Density of Sjganus corallinus was higher on COTS impacted reefs; however, this was not greater than variability over time. On COTS affected reefs, there was a negative correlation of herbivorous fish with thick turf algal abundance and a positive correlation with live coral cover, whereas on non-affected reefs, there were a similar number of positive and negative correlations w~t h thick turf algae and live coral. Additionally, a distinct cross-shelf trend in length frequency of Acanthurus nigrofuscus was observed. Differences in food availability, wave energy and intraspecific competition were hypothesized to be important factors In this observed distribution.

Long-term effects of the 1998 coral bleaching event on reef fish assemblages

“…They are commonly limited to single reefs or, at the most, to reef areas on a regional scale (e.g. Sano et al 1987, Hart et al 1996, Cheal et al 2002, Halford et al 2004). The 1997/1998 coral bleaching event was unique in that it affected coral reefs in all tropical seas and, hence, became the most extensive cause of coral mortality on record (Hoegh-Guldberg 2004).…”

“…Consequently, coral mortality may have implications for herbivores as well, and, accordingly, they were primarily responsible for the recorded overall increase in fish abundance in the coral plots following coral death. Given their large home ranges (Hart et al 1996) and their rapid response to disturbance, as well as the limited size of our coral plots and their proximity to continuous reef, we believe that the observed increase in herbivores 6 mo after the bleaching was largely due to redistribution or increased feeding ranges. Hart et al (1996) suggested that roving herbivores should be able to benefit from sudden increases in turf algae, and a similar increase in herbivores was noted following an outbreak of Acanthaster planci (Wass 1987).…”

The structure of reef fish metapopulations: modelling larval dispersal and retention patterns

“…Extensive larval exchange between local populations will limit opportunities for local adaptation (Holt & Gaines 1992) and increase the evolutionary importance of phenotypically plastic traits (Warner 1997). If local populations in this region are largely open, then there are important implications that affect, for example: population regulation (Caley et al 1996;Armsworth 2002); the resiliency of reef fish communities to local disturbance (Wellington & Victor 1985;Russ 1991;Hart et al 1996;Roberts 1997); the spread of invading species (Randall & Kanayama 1972;Oda & Parrish 1982); and metapopulation growth rates, because of risk spreading and spatial averaging (Kuno 1981;Metz et al 1983;Bascompte et al 2002). However, the model predicts that a few local populations can be expected to consistently replenish themselves with larvae.…”

Changes in trophic community structure of shore fishes at an industrial site in the Gulf of Aqaba, Red Sea

“…An increase in the abundance of some certain herbivorous fish species on degraded coral reefs has been described for bleached reefs by Lindahl et al (2001) and after experimental coral disturbance by Lewis (1998). In contrast, no change in the abundance and biomass of some herbivores was detected on reefs impacted by the crown-ofthorns starfish Acanthaster planci with subsequent algal overgrowth (Hart et al 1996).…”