Quantitative distribution of herbivorous reef fishes in the Gulf of Aqaba (Red Sea)

155

This study describes the patterns of species richness and abundance of herbivorous grazing fishes (Acanthuridae, Scandae, Siganidae) in 5 zones (reef slope, reef crest, reef flat, lagoon, back reef) of 3 reefs on the mid-continental shelf and of 3 reefs on the outer continental shelf in the central region of the Great Barrier Reef. Herbivorous fishes (all 3 families considered together) occur in assemblages which are characteristic of several major zones and this pattern of zonation is consistent on the 6 reefs. Assemblages in deep, outer-slope zones are distinctive from those in shallow zones, There are distinctive assemblages of herbivorous fishes on reef flats, reef crests and over sandy areas in both lagoon and back reef zones. Similarity in these patterns of zonation between reefs suggests that they will be maintained through time. Families display distinctive patterns of zonation also, but patterns differ between families. Acanthurids and scarids generally have higher numbers of species and individuals on reef crests and in lagoons than on reef flats or reef slopes; siganids have higher numbers of species and individuals in lagoons and back reefs than in the other 3 zones studied, Variation in species richness and abundance of individual families between zones was, however, not consistent among reefs at the same shelf location. Different guilds of herbivorous fishes were distributed differently between zones. Suckers feeding on fine sediments were most abundant near windward and leeward edges of reefs; suckers feeding over sand were most abundant in back reefs and lagoons; large and small croppers and scrapers were more abundant in shallow zones (reef crest, reef flat, lagoon) than in deep zones (reef slope, back reef).

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

Distribution and abundance of herbivorous grazing fishes in the central Great Barrier Reef. II. Patterns of zonation of mid-shelf and outhershelf reefs

Russ¹

1984

155

“…However, the comparative data of Bouchon-Navaro & Harmelin- Vivien (1981) suggest that scarids constitute a higher percentage of herbivores on Atlantic island reefs, a n d that acanthurids tend to b e dominant on Indo-Pacific islands. More recent data from Hawaii (Hayes et al 1982), the Florida Keys (Bohnsack 1982), the Philippines (Russ 1984b), and the Australian Great Barrier Reef (Russ 1984a) show some indication of a similar trend.…”

Section: Algal Feedingmentioning

confidence: 98%

Fish communities of interacting shallow-water habitats in tropical oceanic regions

Parrish¹

1989

274

201

ABSTRACT. Coral reefs occur in a variety of situations in the Atlantic, Pacific and lndian Oceans, which involve great differences in the degree of isolation from surrounding shallow-water environments, e.g. seagrass beds, mangroves and unvegetated sediments. Mangroves and seagrass beds appear to offer attractive habitat for fishes -including species commonly found on reefs -especially for settling postlarvae and developing juveniles. These habitats probably intercept large numbers of recruits, and may offer some advantages over coral reefs for early survival of young juveniles. They may act as accumulators of excess recruits, which could tend to smooth out the temporal patchiness of recruits available to reefs directly from the plankton. However, there is no clear evidence that, in general, reefs situated favorably to the shallow-water, vegetated habitats experience enhancement of these early life stages, by comparison with more remote reefs There are a few demonstrated mechanisms for movement of plant and animal material (alive, dead or reprocessed) between these shallow-water habitats. including recycling of reef organic production through an adjacent habitat and back to the reef. The absolute values of such fluxes assimilated by (or returned to) the reef may be small, but the means by which the material is exchanged may be particularly suitable to enhance fish populations. Relative trophic patterns among the various shallow-water, demenal habitats and among the oceans of the world are not entirely clear. This is partly because quantitative fish community studies and trophic studies in seagrass and mangrove habitats are inadequate. Among fish, carnivores appear to dominate in all habitats in almost all situations; usually benthic invertebrates are the major prey group. In a few reported situations, primarily in the Pacific, planktivory appears to be the dominant feeding mode.Algivory is important in all situations, but almost never dominant, and its importance varies widely within (as well as between] oceans and types of situations. It may be most significant on the open coasts of some isolated islands and atolls. Seagrass is a minor direct food source in all oceans and is best documented in the Atlantic. If important linkages occur among the shallow-water, adjacent, tropical habitats, they most likely involve fish recruitment and/or trophic processes involving invertebrates. Both are little-known subjects in these environments, that will require additional, focused research to clarify the nature and magnitude of any interactions that influence marine resources.

“…Several authors have reported distinct differences in the abundance and species composition of, and rates of grazing by, herbivorous fishes at different depths within coral reefs (e.g. Goldman and Talbot, 1976;Bouchon-Navaro and Harmelin-Vivien, 1981 ;Hay, 1981 ;Hatcher, 1982;Hatcher and Larkum, 1983;Hay and Goertemiller, 1983). The shallow zones occur on a gradient of decreasing incident wave energy from reef crest through reef flat to lagoon.…”

Section: Discussionmentioning

confidence: 99%

Distribution and abundance of herbivorous grazing fishes in the central Great Barrier Reef. I. Levels of variability across the entire continental shelf

Russ¹

1984

206

152

Visual censuses were used to study the distribution and abundance of herbivorous grazing fishes (Acanthundae, Scandae, Sigan~dae) on reefs in the central region of the Great Barrier Reef Three locations on the continental shelf (inshore, mid-shelf, outershelf), 3 reefs within each of these locations and, for the mid-and outershelf reefs, 5 zones within each of these reefs were examined The assemblages of herbivorous fishes on inshore reefs were distinctive from those on mid-and outershelf reefs with sianificantlv fewer numbers of species and individuals of acanthunds and scands nshoro A major cumponeni i^f t h i varidbiliiy in lhr-data I , withm-n PI [holwof-n-/one, coriiporn~iii. The wnhin-rwf conip<.ncnt of variiihil~ly ussoci~itcd largely wit" diftc-ronces in the ds'semhldgfs with depth, is greater than that between mid-and outershelf locations and between reefs within these locations When zones are examined individually and compared with reefs inshore the majority of species display significant cross-shelf change in abundance irrespective of the zone examined, with cross-shelf change accounting for often 80 to 90 % of the variability in abundance For most species much of this variability is due to an absence or low abundance on inshore reefs