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81.
Sara M. Lewis Peter C. Wainwright 《Journal of experimental marine biology and ecology》1985,87(3):215-228
Herbivory is a primary factor in determining the structure of coral reef communities. Spatial variation among reef habitats in the intensity of herbivory has been documented, but underlying variation in species composition and abundance within the herbivore guild has received little attention. The distribution and relative abundances of herbivorous fishes and sea urchins across several habitats were studied on the Belizean barrier reef off the Caribbean coast of Central America. Marked variation in total herbivore density as well as major changes in the composition of the herbivore guild were found across reef habitats. Acanthurids (surgeonfishes) predominated in shallow areas (< 5 m) while scarids (parrotfishes) were dominant in deeper habitats. Significant differences among habitats in an experimental assay of grazing intensity were strongly correlated with herbivore abundance. The spatial distribution of herbivorous fishes across reef habitats does not appear to be simply explained by differences in reef topography, but may depend on complex interactions among proximity to nearby shelter, predator abundance, density of territorial competitors, and local availability of food resources. 相似文献
82.
The settlement and recruitment patterns of Chromis viridis were followed during three consecutive seasons along the reefs of Eilat, Red Sea. The findings, based on intensive field surveys and a translocation experiment, indicated a strong and repeatable preference for some, but not other, colonies of the branching coral Acropora eurystoma; with significantly more larvae settling onto preferred colonies that house conspecific adults and juveniles. Furthermore, these findings showed that, given high recruitment rates, settlement‐site selection could drive migration by adults and older juveniles. As only some C. viridis schools received direct settlement, it was suggested that settlement‐driven migration is responsible for the replenishment of those schools that do not receive settlement and to the colonization of previously unoccupied coral colonies. 相似文献
83.
M. A. MacNeil N. A. J. Graham M. J. Conroy C. J. Fonnesbeck N. V. C. Polunin S. P. Rushton P. Chabanet T. R. McClanahan 《Journal of fish biology》2008,73(7):1748-1763
This study shows how capture–mark–recapture (CMR) models can provide robust estimates of detection heterogeneity (sources of bias) in underwater visual‐census data. Detection biases among observers and fish family groups were consistent between fished and unfished reef sites in Kenya, even when the overall level of detection declined between locations. Species characteristics were the greatest source of detection heterogeneity and large, highly mobile species were found to have lower probabilities of detection than smaller, site‐attached species. Fish family and functional‐group detectability were also found to be lower at fished locations, probably due to differences in local abundance. Because robust CMR models deal explicitly with sampling where not all species are detected, their use is encouraged for studies addressing reef‐fish community dynamics. 相似文献
84.
Cortisol, the dominant corticosteroid in fish, and 11-ketotestosterone (11KT), the most potent androgen in fish, are both synthesized and (or) deactivated by the same two enzymes, 11beta-hydroxylase and 11beta-hydroxysteroid dehydrogenase. Cortisol is synthesized in response to stress (such as that caused by interaction with a dominant conspecific), whereas 11KT is synthesized during protogynous sex change. It has been hypothesized that corticosteroids (such as cortisol) inhibit 11KT synthesis via substrate competition, thereby providing a mechanism for the regulation of socially mediated, protogynous sex change. We tested this hypothesis by administering cortisol (50 microg g(-1) body weight) to female sandperch (Parapercis cylindrica) under social conditions that were permissive to sex change (i.e. in the absence of suppressive male dominance). Twenty-one days later, mean physiological cortisol concentration in cortisol-treated fish was 4.2-fold greater than that in 'socially stressed' female fish maintained in a semi-natural system. Although the dosage of cortisol was therefore considered to be favorable for engendering competitive inhibition of 11KT synthesis, all cortisol-treated fish changed sex, as did all sham-treated and control fish (n=7 fish per treatment). In addition, there was no effect of cortisol treatment on the rate of sex change or on the pattern of steroidogenesis. Thus, our results refute the hypothesis that protogynous sex change is regulated by substrate competition between corticosteroids and androgens. 相似文献
85.
Utilization of seagrass habitats by juvenile groupers and snappers in Banten Bay,Banten Province,Indonesia 总被引:2,自引:1,他引:1
Siti Nuraini Eira C. Carballo Wim L. T. van Densen Marcel A. M. Machiels Han J. Lindeboom Leopold A. J. Nagelkerke 《Hydrobiologia》2007,591(1):85-98
Coastal development in Banten Bay, Indonesia, decreased seagrass coverage to only 1.5% of its surface area. We investigated
the importance of seagrass as habitat for juvenile groupers (Serranidae) and snappers (Lutjanidae), by performing beam trawl
hauls on a weekly basis in two seagrass locations and one mudflat area, and monthly trawl hauls in three different microhabitats
(dense, mixed and patchy seagrass) in one of the seagrass locations. We studied the effects of location and microhabitat,
as well as temporal patterns (diel, weekly and monthly) on the probability of occurrence and abundance of the most abundant
grouper (Orange-spotted grouper, Epinephelus coioides) and snapper (Russell’s snapper, Lutjanus russellii). We found that both species were almost exclusively found in seagrass locations, with a preference for microhabitats of
high complexity (dense and mixed microhabitats). L. russellii had a higher probability of catch and abundance during the night, most probably because of its ability to avoid the beam
trawl during daytime sampling. In addition there was an effect of week and month on the presence and abundance of both species,
but patterns were unclear, probably because of high fishing pressure on juvenile groupers and snappers by push net fishermen.
Groupers and snappers mainly fed on abundant shrimps, and to a lesser extent on fish. Moreover, juveniles find protection
against predators in seagrass, which confirmed the critical role of quantity and quality of seagrass areas for juvenile groupers
and snappers in Banten Bay. 相似文献
86.
Derelict ships are commonly deployed as artificial reefs in the United States, mainly for recreational fishers and divers.
Despite their popularity, few studies have rigorously examined fish assemblages on these structures and compared them to natural
reefs. Six vessel-reefs off the coast of southeast Florida were censused quarterly (two ships per month) to characterize their
associated fish assemblages. SCUBA divers used a non-destructive point-count method to visually assess the fish assemblages
over 13- and 12-month intervals (March 2000 to March 2001 and March 2002 to February 2003). During the same intervals, fish
assemblages at neighboring natural reefs were also censused. A total of 114,252 fishes of 177 species was counted on natural
and vessel-reefs combined. Mean fish abundance and biomass were significantly greater on vessel-reefs in comparison to surrounding
natural reef areas. Haemulidae was the most abundant family on vessel-reefs, where it represented 46% of total fish abundance.
The most abundant family on natural reefs was Labridae, where it accounted for 24% of total fish abundance. Mean species richness
was significantly greater on vessel-reefs than neighboring natural reefs and also differed among vessel-reefs. Both mean fish
abundance and mean species richness were not significantly different between natural reefs neighboring vessel-reefs and natural
reefs with no artificial structures nearby. This suggests the vessel-reefs are not, in general, attracting fish away from
neighboring natural reefs in our area. Additionally, economically important fish species seem to prefer vessel-reefs, as there
was a greater abundance of these species on vessel-reefs than surrounding natural reef areas. Fish assemblage structure on
natural versus artificial reefs exhibited a low similarity (25.8%). Although no one species was responsible for more than
6% of the total dissimilarity, fish assemblage trophic structure differed strikingly between the two reef types. Planktivores
dominated on vessel-reefs, accounting for 54% of the total abundance. Conversely, planktivores only made up 27% of total abundance
on natural reefs. The results of this study indicate vessel-reef fish assemblages are unique and that these fishes may be
utilizing food resources and habitat characteristics not accessible from or found at natural reefs in our area. Production
may also be occurring at vessel-reefs as the attraction of fish species from nearby natural reefs seems to be minimal.
Electronic supplementary material Supplementary material is available for this article at and accessible for authorised users 相似文献
87.
The aim of the study was to evaluate the long-term development of a hard bottom benthic assemblage over a period of 20 years
in an area off the mouth of a large river. The artificial reef of Fregene was selected because benthic assemblage data were
available for the period 1981–1992. This artificial reef is located in the mid Tyrrhenian Sea, 5 nautical miles north of the
two mouths of the Tevere River (Latium, Italy) and 1.5 nautical miles offshore from Fregene (Rome, Italy). The artificial
reef was deployed in March 1981 for fisheries enhancement in 10–14 m of water on a sandy-silty seabed. The Tevere River carries
suspended materials and a heavy load of organics since it transports Rome’s effluent, resulting in the eutrophic state of
area waters. Benthic sampling was conducted in 2001 by SCUBA diving; two standard surfaces of 400 cm2 were scraped from the vertical walls of the same uppermost block in four different periods. All organisms were identified
and counted. The methodology used is the same as that adopted in the previous periods, so that the 2001 data could be compared
with past collected data. The benthic assemblage was analysed by cluster analysis using the Bray-Curtis index and clustered
using the group average clustering algorithm. The SIMPER procedure was used to identify those taxa that characterize each
station group identified by cluster analysis. Changes in benthic assemblages and hydrological trends of the Tevere River were
investigated using the cumulative sum series method. The 20-year development of the benthic community, starting from the new
substratum, is composed of different phases characterised by different benthic assemblages. In particular five different phases
were distinguished: 1. Pioneer species recruitment (May 1981–June 1981); 2. Mytilus galloprovincialis (mussel) dominance (August 1981–November 1983); 3. M. galloprovincialis regression (July 1984–October 1985); 4. M. galloprovincialis absence (91–92); 5. Bryozoans bioconstruction dominance (2001). The dynamic succession of the observed benthic assemblages
exhibited a good relation with the Tevere River flow. The Tevere River flow, and the subsequent sedimentation process, seems
to have strongly influenced the benthic assemblage succession of the Fregene artificial reef.
Guest editors: G. Relini & J. Ryland
Biodiversity in Enclosed Seas and Artificial Marine Habitats 相似文献
88.
Gagliano M McCormick MI Meekan MG 《Proceedings. Biological sciences / The Royal Society》2007,274(1618):1575-1582
For organisms with complex life cycles, variation among individuals in traits associated with survival in one life-history stage can strongly affect the performance in subsequent stages with important repercussions on population dynamics. To identify which individual attributes are the most influential in determining patterns of survival in a cohort of reef fish, we compared the characteristics of Pomacentrus amboinensis surviving early juvenile stages on the reef with those of the cohort from which they originated. Individuals were collected at hatching, the end of the planktonic phase, and two, three, four, six and eight weeks post-settlement. Information stored in the otoliths of individual fish revealed strong carry-over effects of larval condition at hatching on juvenile survival, weeks after settlement (i.e. smaller-is-better). Among the traits examined, planktonic growth history was, by far, the most influential and long-lasting trait associated with juvenile persistence in reef habitats. However, otolith increments suggested that larval growth rate may not be maintained during early juvenile life, when selective mortality swiftly reverses its direction. These changes in selective pressure may mediate growth-mortality trade-offs between predation and starvation risks during early juvenile life. Ontogenetic changes in the shape of selectivity may be a mechanism maintaining phenotypic variation in growth rate and size within a population. 相似文献
89.
A process-based carbonate budget was used to compare carbonate framework production at two reef sites subject to varying degrees
of fluvial influence in Rio Bueno, Jamaica. The turbid, central embayment was subjected to high rates of fluvial sediment
input, framework accretion was restricted to ≤30 m, and net carbonate production was 1,887 g CaCO3 m−2 year−1. Gross carbonate production (GCP) was dominated by scleractinians (97%), particularly by sediment-resistant species, e.g.
Diploria strigosa on the reef flat (<2 m). Calcareous encrusters contributed very little carbonate. Total bioerosion removed 265 g CaCO3 m−2 year−1 and was dominated by microborers. At the clear-water site, net carbonate production was 1,236 g CaCO3 m−2 year−1; the most productive zone was on the fore-reef (10 m). Corals accounted for 82% of GCP, and encrusting organisms 16%. Bioerosion
removed 126 g CaCO3 m−2 year−1 and was dominated by macroborers. Total fish and urchin grazing was limited throughout (≤20 g CaCO3 m−2 year−1). The study demonstrates that: (1) carbonate production and net reef accretion can occur where environmental conditions approach
or exceed perceived threshold levels for coral survival; and (2) although live coral cover (and carbonate production rates)
were reduced on reef-front sites along the North Jamaican coast, low population densities of grazing fish and echinoids to
some extent offset this, thus maintaining positive carbonate budgets. 相似文献
90.