Green2009-herbivore monitoring

More documents

Recommendations

Info

Monitoring Functional Groups of Herbivorous Reef Fishes Browsers Browsers consistently feed on macroalgae. They select individual algal components and remove only algae and associated epiphytic material (Hoey and Bellwood 2008). Browsers play an important role in reducing coral overgrowth and shading by macroalgae, and may play an important role in reversing coral-algal phase shifts (see Reversing Coral-Algal Phase Shifts). Browsers include some unicornfishes that feed on algae throughout their lives (e.g. N. unicornis), and small individuals of other species that feed on algae when they are small (20cm SL e.g. N. annulatus: see Ontogenetic Changes in Feeding Modes). Browsers: unicornfish (left: Naso unicornis) and rudderfish (right: Kyphosus vaigiensis). Images by A. Hoey and G. Allen respectively. Also included are rudderfishes, batfishes (which will eat both plant and animal material: Bellwood et al 2006), a rabbitfish (S. canaliculatus: Fox and Bellwood 2008) and parrotfishes of the genus Calotomus (Choat 1991, Choat et al 2002) and Leptoscarus. Browsers: batfish (left: Platax teira). Image by G. Allen. 31
Monitoring Functional Groups of Herbivorous Reef Fishes Assigning Species to Functional Groups The practical application of monitoring key functional groups of herbivores requires assigning each species to a functional group in each geographic area. The following is an example of how to assign species to functional groups, based on a case study for the Asia Pacific Region. This study focuses on six families of herbivorous reef fishes that each play important roles in coral reef resilience: Acanthuridae, Ephippidae, Kyphosidae, Pomacanthidae, Labridae (Tribe Scarini) and Siganidae (see Key Families and Their Feeding Modes). Other herbivorous reef fishes are not included because: • Small, cryptic families (blennies and gobies) are not amenable to visual census techniques, and are unlikely to make a significant contribution in terms of ecosystem resilience. • Damselfishes are small, and hard to identify. They also comprise a wide variety of diets (herbivores, detritivores, algae grazers and planktivores), and it is a complex and difficult task to assign them to functional groups. Species that are herbivorous also tend to be small and contribute less in terms of ecosystem resilience, because they are territorial and farm algae for their own consumption (see Territorial Behaviour). • While some filefishes, triggerfishes and a wrasse (Pseudodax mollucanus: Cowman et al in press) may be herbivores, their trophic status has not been confirmed (Myers 1999, Randall et al 1996, G.P Jones unpubl. data). A species list for each family in the Asia Pacific Region was provided by Dr. Gerry Allen (Allen et al 2003). Each species was assigned to a functional group (see Functional Groups above) based on the best available literature, and expert opinion (Table 1). Species that did not belong to one of these functional groups were deleted, including species that feed exclusively on detritus (Ctenochaetus species) or plankton (some Acanthurus and Naso species: see Key Families and Their Feeding Modes). Ontogenetic changes in diet were taken into account for some species (see Ontogenetic Changes in Feeding Modes). For example, only juveniles of some species of unicornfishes were included, because they undergo an ontogenetic change from browsers to planktivores at around 20cm SL. However, ontogenetic changes in parrotfishes from carnivory to herbivory were not considered, because this change occurs at such a small size (32mm SL: Bellwood 1988) that juvenile parrotfishes that are still carnivores would not be counted using underwater visual census methods (see Monitoring Methods below). These species will provide the basis of a monitoring program for key functional groups of herbivores on reefs in the Asia Pacific Region. 32
Page 1 and 2: Monitoring Functional Groups of Her
Page 7 and 8: TABLE OF CONTENTS EXECUTIVE SUMMARY
Page 9 and 10: Executive Summary exposing hard, re
Page 11 and 12: Executive Summary Advice is also pr
Page 13 and 14: Background STATUS AND TRENDS The di
Page 15 and 16: Coral Reef Resilience Resilient ree
Page 17 and 18: Coral Reef Resilience In summary, h
Page 19 and 20: Coral Reef Resilience herbivores, b
Page 21 and 22: Herbivorous Coral Reef Fishes HERBI
Page 23 and 24: Herbivorous Coral Reef Fishes to wh
Page 25 and 26: Herbivorous Coral Reef Fishes The r
Page 27 and 28: Herbivorous Coral Reef Fishes reefs
Page 31: Monitoring Functional Groups of Her
Page 57 and 58: References CBD 2009 Identifying and
Page 59 and 60: References Hamilton, R.J. 2004 The
Page 61 and 62: References McCook, L. J., Folke, C.
Page 63 and 64: References Wainwright, P.C., Bellwo
Page 65 and 66: Glossary Fish Families and Common N
Page 67 and 68: Appendix 1 Timed Swims (Large Indiv
Page 69 and 70: Appendix 1 50 m Transects (Large In
Page 71 and 72: Appendix 2 APPENDIX 2 Biomass Const
Page 73 and 74: Appendix 2 Family Species a b Sourc
Page 75: INTERNATIONAL UNION FOR CONSERVATIO

Green2009-herbivore monitoring

Create successful ePaper yourself

Delete template?

Save as template?