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Hazel Oxenford - One of the best experts on this subject based on the ideXlab platform.
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Simple family-level Parrotfish indicators are robust to survey method
Ecological Indicators, 2018Co-Authors: Henri Vallès, Hazel OxenfordAbstract:Abstract Given the current degradation of Caribbean coral reefs, considerable regional emphasis has been put into monitoring the state of key exploited reef fish herbivores, namely surgeonfishes and Parrotfishes, through underwater visual fish surveys (UVFS). However, like all survey methods, UVFS suffer from sampling errors that could mask real spatio-temporal trends in fish metrics. Here, we compare trends in simple reef fish herbivore metrics, i.e. average individual fish weight, fish abundance and fish biomass, between UVFS and fish trap surveys, an alternative survey method. Because both methods fundamentally differ in the underlying nature of their sampling errors, we argue that fish metrics exhibiting high consistency between methods will more likely reflect real environmentally-induced trends and should thus be emphasized in monitoring programs. We conducted repeated surveys using both methods concurrently at six sites along a fishing pressure gradient in a Caribbean island. We then examined between-method consistency in fish metric trends across sites and precision in fish metric estimates for each method using surgeonfish and Parrotfish data at different levels of aggregation, i.e. species-, family- and functional-level (both herbivorous families combined). We found high and robust between-method consistency only for Parrotfish data aggregated at the family level, which also exhibited the highest overall precision in metric estimates. All other fish groups exhibited poorer between-method consistency and poorer precision in their metrics, indicating comparatively higher sensitivity to method-specific sampling errors. Overall, our study supports that family-level Parrotfish metrics are particularly robust to survey method, which considerably increases their value as indicators for Caribbean reef monitoring programs.
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Parrotfish size as a useful indicator of fishing effects in a small Caribbean island
Coral Reefs, 2015Co-Authors: Henri Vallès, David Gill, Hazel OxenfordAbstract:There is an urgent need to develop simple indicators of fishing effects for the implementation of ecosystem-based fisheries management in the Caribbean. In this study, we compare the ability of three simple metrics (average individual fish weight, fish density, and fish biomass) derived from the Parrotfish assemblage and from an assemblage of highly valued commercial fish species to track changes in fishing pressure at spatial scales relevant to small Caribbean islands. Between June and August 2011, we conducted five consecutive visual fish surveys at six reefs ≤10 km apart along the west coast of Barbados, representing a spatial gradient in fishing pressure. We used these data to identify the fish metrics most strongly correlated with fishing pressure and describe their functional relationship with fishing pressure. Overall, average individual Parrotfish weight and biomass and density of commercial fish species were the metrics most strongly correlated with fishing pressure, although for the latter two, such correlations depended on the range of fish body sizes analyzed. Fishing pressure accounted for most of the variability in all correlated fish metrics (adj R 2 ≥ 0.75). However, functional relationships with fishing pressure differed qualitatively between metrics. In particular, average individual Parrotfish weight was the metric most sensitive to incremental changes in fishing pressure. Overall, our study highlights that assemblage-level average individual Parrotfish weight deserves a place in the toolbox of Caribbean reef managers as a simple indicator of both fishing effects on Parrotfish assemblages and overall fishing pressure on the reef fish community.
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Parrotfish Size: A Simple yet Useful Alternative Indicator of Fishing Effects on Caribbean Reefs?
PloS one, 2014Co-Authors: Henri Vallès, Hazel OxenfordAbstract:There is great need to identify simple yet reliable indicators of fishing effects within the multi-species, multi-gear, data-poor fisheries of the Caribbean. Here, we investigate links between fishing pressure and three simple fish metrics, i.e. average fish weight (an estimate of average individual fish size), fish density and fish biomass, derived from (1) the Parrotfish family, a ubiquitous herbivore family across the Caribbean, and (2) three fish groups of “commercial” carnivores including snappers and groupers, which are widely-used as indicators of fishing effects. We hypothesize that, because most Caribbean reefs are being heavily fished, fish metrics derived from the less vulnerable Parrotfish group would exhibit stronger relationships with fishing pressure on today’s Caribbean reefs than those derived from the highly vulnerable commercial fish groups. We used data from 348 Atlantic and Gulf Rapid Reef Assessment (AGRRA) reef-surveys across the Caribbean to assess relationships between two independent indices of fishing pressure (one derived from human population density data, the other from open to fishing versus protected status) and the three fish metrics derived from the four aforementioned fish groups. We found that, although two fish metrics, average Parrotfish weight and combined biomass of selected commercial species, were consistently negatively linked to the indices of fishing pressure across the Caribbean, the Parrotfish metric consistently outranked the latter in the strength of the relationship, thus supporting our hypothesis. Overall, our study highlights that (assemblage-level) average Parrotfish size might be a useful alternative indicator of fishing effects over the typical conditions of most Caribbean shallow reefs: moderate-to-heavy levels of fishing and low abundance of highly valued commercial species.
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Interspecific differences in foraging behaviour and functional role of Caribbean Parrotfish
Marine Biodiversity Records, 2009Co-Authors: Sónia C. Cardoso, Hazel Oxenford, Marta C. Soares, Isabelle M. CôtéAbstract:Herbivory is one of the most important biological processes influencing coral reefs. In the highly diverse Indo-Pacific reef fish communities, different herbivores can have strikingly different functions. We investigated the extent of functional diversity among herbivorous Parrotfish of the more species-depauperate Caribbean Sea. We carried out observations of seven species of Parrotfish (Scarus taeniopterus, Sc. vetula, Sc. iserti, Sparisoma viride, Sp. aurofrenatum, Sp. rubripinne and Sp. chrysopterum) on four Barbadian coral reefs to collect information on foraging techniques, rates, and targets, and found marked interspecific variation. Species of the genus Scarus had higher foraging rates than those of the genus Sparisoma . Different species took varying amounts of live coral, turf algae and macroalgae. A functional categorization based first on foraging technique (contact or no contact with the substratum) and secondarily on the more conventional criterion of foraging target (macroalgae, turf algae and live coral) allowed us to classify Sc. taeniopterus and Sc. iserti as ‘scrapers’, Sp. aurofrenatum , Sp. rubripinne and Sp. chrysopterum as ‘grazers’, Sp. viride as a ‘bioeroder’ and Sc. vetula as a ‘bioeroder/scraper’. This functional group affiliation, together with species-specific foraging rates, allows us to predict the role of Caribbean Parrotfish on major coral reef processes and their impact on coral reef benthic communities.
Peter J. Mumby - One of the best experts on this subject based on the ideXlab platform.
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Spatial Patterns of Parrotfish Corallivory in the Caribbean: The Importance of Coral Taxa, Density and Size
2016Co-Authors: George Roff, Mary H. Ledlie, Juan Carlos Ortiz, Peter J. MumbyAbstract:The past few decades have seen an increase in the frequency and intensity of disturbance on coral reefs, resulting in shifts in size and composition of coral populations. These changes have lead to a renewed focus on processes that influence demographic rates in corals, such as corallivory. While previous research indicates selective corallivory among coral taxa, the importance of coral size and the density of coral colonies in influencing corallivory are unknown. We surveyed the size, taxonomy and number of bites by Parrotfish per colony of corals and the abundance of three main corallivorous Parrotfish (Sparisoma viride, Sparisoma aurofrenatum, Scarus vetula) at multiple spatial scales (reefs within islands: 1–100 km, and between islands:.100 km) within the Bahamas Archipelago. We used a linear mixed model to determine the influence of coral taxa, colony size, colony density, and Parrotfish abundance on the intensity of corallivory (bites per m2 of coral tissue). While the effect of colony density was significant in determining the intensity of corallivory, we found no significant influence of colony size or Parrotfish abundance (density, biomass or community structure). Parrotfish bites were most frequently observed on the dominant species of reef building corals (Montastraea annularis, Montastraea faveolata and Porites astreoides), yet our results indicate that when the confounding effects of colony density and size were removed, selective corallivory existed only for the less dominant Porites porites. As changes in disturbance regimes result in the decline of dominant frame-work building corals such as Montastraea spp., the projected success of P. porites on Caribbea
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Experiment mimics fishing on Parrotfish: insights on coral reef recovery and alternative attractors
Marine Ecology Progress Series, 2014Co-Authors: Robert S. Steneck, Suzanne N. Arnold, Peter J. MumbyAbstract:Dominance shifts in ecosystems can occur rapidly, resulting in alternative stable states. While some coral reef ecosystems shift and recover relatively quickly, others recover slowly or not at all over periods of centuries. We explore the role of large (fishing-susceptible) Parrotfish in triggering algal phase shifts as alternative attractors that may lock reefs into coral-depleted alternative stable states. We designed an experiment to modestly reduce herbivory only from large Parrotfish in the immediate vicinity of experimental coral settlement nursery habitats. We used vertical pegs ('Parrotfish deterrents' or PDs) around coral settlement plates on 2 Belizean fore reefs. Time-lapse videos and a year's accumulation of bite-marks on plates confirmed that only herbivory from large Parrotfish declined significantly due to PDs. Patches of macroalgae developed around PDs reducing coral recruitment in this treatment only. Two dominant reefdwelling coral genera (Porites and Agaricia) recruited to our settlement plates. The fast-growing, high-light requiring, reef-building coral Porites was more negatively affected by phase shifts; this coral failed to recruit at and above mid-levels of algal abundance. We illustrate the direct roles eco logical processes such as herbivory from large Parrotfish play in regulating algal abundance, which in turn reduces the recruitment potential of reefs and thus the ecosystem's capacity to recover. Combining our empirical results with an individually-based ecological simulation model, we determined that these processes cascade to drive alternative states and create a 'hysteresis' effect delaying or preventing recovery of the coral reef ecosystem.
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Spatial patterns of Parrotfish corallivory in the Caribbean: the importance of coral taxa, density and size.
PloS one, 2011Co-Authors: George Roff, Mary H. Ledlie, Juan Carlos Ortiz, Peter J. MumbyAbstract:The past few decades have seen an increase in the frequency and intensity of disturbance on coral reefs, resulting in shifts in size and composition of coral populations. These changes have lead to a renewed focus on processes that influence demographic rates in corals, such as corallivory. While previous research indicates selective corallivory among coral taxa, the importance of coral size and the density of coral colonies in influencing corallivory are unknown. We surveyed the size, taxonomy and number of bites by Parrotfish per colony of corals and the abundance of three main corallivorous Parrotfish (Sparisoma viride, Sparisoma aurofrenatum, Scarus vetula) at multiple spatial scales (reefs within islands: 1–100 km, and between islands: >100 km) within the Bahamas Archipelago. We used a linear mixed model to determine the influence of coral taxa, colony size, colony density, and Parrotfish abundance on the intensity of corallivory (bites per m2 of coral tissue). While the effect of colony density was significant in determining the intensity of corallivory, we found no significant influence of colony size or Parrotfish abundance (density, biomass or community structure). Parrotfish bites were most frequently observed on the dominant species of reef building corals (Montastraea annularis, Montastraea faveolata and Porites astreoides), yet our results indicate that when the confounding effects of colony density and size were removed, selective corallivory existed only for the less dominant Porites porites. As changes in disturbance regimes result in the decline of dominant frame-work building corals such as Montastraea spp., the projected success of P. porites on Caribbean reefs through high reproductive output, resistance to disease and rapid growth rates may be attenuated through selective corallivory by Parrotfish.
Omar Domínguez-domínguez - One of the best experts on this subject based on the ideXlab platform.
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Phylogeography, population connectivity and demographic history of the Stoplight Parrotfish, Sparisoma viride (Teleostei: Labridae), in the Greater Caribbean
Coral Reefs, 2021Co-Authors: Francisco Javier Loera-padilla, Victor Julio Piñeros, Carole C. Baldwin, Courtney E. Cox, Nuno Simoes, Emanuell Ribeiro, Oscar M. Lasso-alcalá, Omar Domínguez-domínguezAbstract:Few genetic studies that provide biological, ecological and evolutionary information have been conducted for Parrotfishes, including Sparisoma viride, and none has covered the full geographic range of this species. Here, we examine the genetic patterns of the Stoplight Parrotfish ( S. viride ) in the Greater Caribbean and its relationship with the recognized biogeographic provinces in the region. Phylogeographic, population and coalescent analyses were performed to examine the genetic structure and connectivity of S. viride populations throughout its entire range within the Greater Caribbean. Two mitochondrial (control region and coxI ) and one nuclear ( RHO ) markers were used. The Stoplight Parrotfish shows high haplotypic diversity ( h ) and low nucleotide diversity ( π ) in the control region, and low genetic diversity in coxI and RHO . No evidence of genetic structure was found, indicating a panmictic population throughout the Greater Caribbean with highly symmetrical migration rates among previously defined Caribbean biogeographic provinces. The demographic history estimates indicate events of bottlenecks followed by a population expansion dated at 80,000 years ago (kya) during the Pleistocene epoch. These results suggest that the contrasting environmental conditions that define the Greater Caribbean provinces are not barriers to gene flow for S. viride . The phylogeographic patterns of Stoplight Parrotfish could be associated with the biological characteristics of the species (such as extensive pelagic larval duration and use of multiple habitats), historical demographic events and physical conditions of the Greater Caribbean, promoting the genetic homogeneity of the species in the region.
Henri Vallès - One of the best experts on this subject based on the ideXlab platform.
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Simple family-level Parrotfish indicators are robust to survey method
Ecological Indicators, 2018Co-Authors: Henri Vallès, Hazel OxenfordAbstract:Abstract Given the current degradation of Caribbean coral reefs, considerable regional emphasis has been put into monitoring the state of key exploited reef fish herbivores, namely surgeonfishes and Parrotfishes, through underwater visual fish surveys (UVFS). However, like all survey methods, UVFS suffer from sampling errors that could mask real spatio-temporal trends in fish metrics. Here, we compare trends in simple reef fish herbivore metrics, i.e. average individual fish weight, fish abundance and fish biomass, between UVFS and fish trap surveys, an alternative survey method. Because both methods fundamentally differ in the underlying nature of their sampling errors, we argue that fish metrics exhibiting high consistency between methods will more likely reflect real environmentally-induced trends and should thus be emphasized in monitoring programs. We conducted repeated surveys using both methods concurrently at six sites along a fishing pressure gradient in a Caribbean island. We then examined between-method consistency in fish metric trends across sites and precision in fish metric estimates for each method using surgeonfish and Parrotfish data at different levels of aggregation, i.e. species-, family- and functional-level (both herbivorous families combined). We found high and robust between-method consistency only for Parrotfish data aggregated at the family level, which also exhibited the highest overall precision in metric estimates. All other fish groups exhibited poorer between-method consistency and poorer precision in their metrics, indicating comparatively higher sensitivity to method-specific sampling errors. Overall, our study supports that family-level Parrotfish metrics are particularly robust to survey method, which considerably increases their value as indicators for Caribbean reef monitoring programs.
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Parrotfish recruitment revisited: a key role for sea surface currents
Environmental Biology of Fishes, 2017Co-Authors: Henri VallèsAbstract:Despite considerable attention to the role of Parrotfish assemblages in maintaining coral reef ecosystem integrity, little is known about the factors affecting Parrotfish settlement, which could play an important role in structuring Parrotfish assemblages. Here, I expand on a previous study that sought to identify environmental correlates of the temporal patterns of recruitment of Sparisoma Parrotfishes onto standardized settlement units sampled at 52 consecutive 10-day intervals over an uninterrupted 17-month period on the west coast of Barbados (W.I.). By (1) including previously unavailable satellite-derived island-wide current speed data in the analyses and (2) using a more flexible (non-linear) analytical framework, the re-analysis increased the variance explained from 24% to 74%. Furthermore, island-wide current speed had stronger predictive power than all of the previously identified environmental correlates of Sparisoma recruitment, i.e. sea surface temperature and chlorophyll a concentration, and lunar phase, underscoring a dominant role for large-scale, transport-related physical processes in driving Parrotfish settlement. Relationships between Sparisoma recruitment and the environmental correlates were better explained as non-linear functions, with a hump-shaped relationship for current speed. Most variability in current speed reflected external forcing due to the passage through Barbados of a large, slow-moving, low-salinity intrusion of South American riverine origin. Considering the high recruitment variance explained and that satellite-derived data on key environmental correlates are publicly available, prediction of temporal patterns of Parrotfish settlement in Barbados might be more feasible than previously expected.
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Parrotfish size as a useful indicator of fishing effects in a small Caribbean island
Coral Reefs, 2015Co-Authors: Henri Vallès, David Gill, Hazel OxenfordAbstract:There is an urgent need to develop simple indicators of fishing effects for the implementation of ecosystem-based fisheries management in the Caribbean. In this study, we compare the ability of three simple metrics (average individual fish weight, fish density, and fish biomass) derived from the Parrotfish assemblage and from an assemblage of highly valued commercial fish species to track changes in fishing pressure at spatial scales relevant to small Caribbean islands. Between June and August 2011, we conducted five consecutive visual fish surveys at six reefs ≤10 km apart along the west coast of Barbados, representing a spatial gradient in fishing pressure. We used these data to identify the fish metrics most strongly correlated with fishing pressure and describe their functional relationship with fishing pressure. Overall, average individual Parrotfish weight and biomass and density of commercial fish species were the metrics most strongly correlated with fishing pressure, although for the latter two, such correlations depended on the range of fish body sizes analyzed. Fishing pressure accounted for most of the variability in all correlated fish metrics (adj R 2 ≥ 0.75). However, functional relationships with fishing pressure differed qualitatively between metrics. In particular, average individual Parrotfish weight was the metric most sensitive to incremental changes in fishing pressure. Overall, our study highlights that assemblage-level average individual Parrotfish weight deserves a place in the toolbox of Caribbean reef managers as a simple indicator of both fishing effects on Parrotfish assemblages and overall fishing pressure on the reef fish community.
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Parrotfish Size: A Simple yet Useful Alternative Indicator of Fishing Effects on Caribbean Reefs?
PloS one, 2014Co-Authors: Henri Vallès, Hazel OxenfordAbstract:There is great need to identify simple yet reliable indicators of fishing effects within the multi-species, multi-gear, data-poor fisheries of the Caribbean. Here, we investigate links between fishing pressure and three simple fish metrics, i.e. average fish weight (an estimate of average individual fish size), fish density and fish biomass, derived from (1) the Parrotfish family, a ubiquitous herbivore family across the Caribbean, and (2) three fish groups of “commercial” carnivores including snappers and groupers, which are widely-used as indicators of fishing effects. We hypothesize that, because most Caribbean reefs are being heavily fished, fish metrics derived from the less vulnerable Parrotfish group would exhibit stronger relationships with fishing pressure on today’s Caribbean reefs than those derived from the highly vulnerable commercial fish groups. We used data from 348 Atlantic and Gulf Rapid Reef Assessment (AGRRA) reef-surveys across the Caribbean to assess relationships between two independent indices of fishing pressure (one derived from human population density data, the other from open to fishing versus protected status) and the three fish metrics derived from the four aforementioned fish groups. We found that, although two fish metrics, average Parrotfish weight and combined biomass of selected commercial species, were consistently negatively linked to the indices of fishing pressure across the Caribbean, the Parrotfish metric consistently outranked the latter in the strength of the relationship, thus supporting our hypothesis. Overall, our study highlights that (assemblage-level) average Parrotfish size might be a useful alternative indicator of fishing effects over the typical conditions of most Caribbean shallow reefs: moderate-to-heavy levels of fishing and low abundance of highly valued commercial species.
Cardwell - One of the best experts on this subject based on the ideXlab platform.
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Androgen control of social status in males of a wild population of stoplight Parrotfish, Sparisoma viride (Scaridae).
Hormones and behavior, 1991Co-Authors: CardwellAbstract:In the protogynous stoplight Parrotfish (Sparisoma viride), large males defend territories that encompass the home-ranges of several mature females. However, high-quality habitat is in short supply, such that smaller, competitively inferior males do not defend territories. We investigated the role of 11-ketotestosterone (11KT) and testosterone (T) in the regulation of territorial behavior in a wild population of a protogynous reef fish, the stoplight Parrotfish, at Glover's Reef, Belize. Radioimmunoassay of plasma samples from individuals of known social status revealed that nonterritorial males have lower levels of T and 11KT than territorial males. Nonterritorial males allowed access to vacant territories underwent pronounced increases in T and 11KT. When sampled 1 week after territory acquisition, levels of T and 11KT in new territorial males were significantly higher than the levels in established territorial males, but by 3 weeks after territory acquisition, there was no significant difference. We further investigated the hypothesis that such short-term increases in androgen levels are a response to intense male-male interactions during territory establishment. Simulated territorial intrusion promoted increased plasma levels of both T and 11KT while access to vacant territories without neighboring territorial males did not. These findings suggest that the endocrine system plays a role in fine-tuning the levels of territorial aggression exhibited by male stoplight Parrotfish. We discuss these results in light of recent theory in behavioral endocrinology.