I am interested in applied marine ecology and ichthyology, particularly as the they relate to the management of marine habitats and fisheries. My specific interests include Essential Fish Habitat, Marine Protected Areas, coral reef fisheries management, reef fish spawning aggregations, early life history and recruitment, fish tagging and migration studies, fisheries management planning, fish habitat management, and Environmental Impact Assessment. Supervisors: PhD advisor: Dr. Robert G Boutiler (deceased), MSc and postdoc advisor: Dr. Wayne Hunte, Postdoctoral advisor: Dr Ken Able, Postdoctoral advisor: Dr. Grant Gilmore, and Postdoctoral advisor: Dr. Francis Juanes
Coral reefs provide ecosystem goods and services for millions of people in the tropics, but reef ... more Coral reefs provide ecosystem goods and services for millions of people in the tropics, but reef conditions are declining worldwide. Effective solutions to the crisis facing coral reefs depend in part on understanding the context under which different types of conservation benefits can be maximized. Our global analysis of nearly 1,800 tropical reefs reveals how the intensity of human impacts in the surrounding seascape, measured as a function of human population size and accessibility to reefs (" gravity "), diminishes the effectiveness of marine reserves at sustaining reef fish biomass and the presence of top predators, even where compliance with reserve rules is high. Critically, fish biomass in high-compliance marine reserves located where human impacts were intensive tended to be less than a quarter that of reserves where human impacts were low. Similarly, the probability of encountering top predators on reefs with high human impacts was close to zero, even in high-compliance marine reserves. However, we find that the relative difference between openly fished sites and reserves (what we refer to as conservation gains) are highest for fish biomass (excluding predators) where human impacts are moderate and for top predators where human impacts are low. Our results illustrate critical ecological trade-offs in meeting key conservation objectives: reserves placed where there are moderate-to-high human impacts can provide substantial conservation gains for fish biomass, yet they are unlikely to support key ecosystem functions like higher-order predation, which is more prevalent in reserve locations with low human impacts. marine reserves | fisheries | coral reefs | social-ecological | socioeconomic T he world's coral reefs are rapidly degrading (1–3), which is diminishing ecological functioning and potentially affecting the well-being of the millions of people with reef-dependent livelihoods (4). Global climate change and local human impacts (such as fishing) are pervasive drivers of reef degradation (1, 5). In Significance Marine reserves that prohibit fishing are a critical tool for sustaining coral reef ecosystems, yet it remains unclear how human impacts in surrounding areas affect the capacity of marine reserves to deliver key conservation benefits. Our global study found that only marine reserves in areas of low human impact consistently sustained top predators. Fish biomass inside marine reserves declined along a gradient of human impacts in surrounding areas; however, reserves located where human impacts are moderate had the greatest difference in fish biomass compared with openly fished areas. Reserves in low human-impact areas are required for sustaining ecological functions like high-order predation, but reserves in high-impact areas can provide substantial conservation gains in fish biomass.
von Herbing, IH and M. Tupper. The implications of localized fishery stocks. Natural Resource, Agriculture, and Engineering Service. Ithaca, New York, 1997
The effects of a non-extractive marine reserve on the recruitment dynamics of haemulid fishes and... more The effects of a non-extractive marine reserve on the recruitment dynamics of haemulid fishes and their predators on Barbados coral reefs were studied using visual census and mark-recapture methods. Size and abundance of piscivores (including large adult grunts) known to prey on grunts were greater within the reserve than on adjacent reefs, whereas size and abundance of older juvenile grunts did not differ between protected and exploited reefs. Recruitment and early juvenile abundance were lower within the reserve and were ...
Marine Protected Areas (MPAs) are often advocated by ecologists as a method of conserving valuabl... more Marine Protected Areas (MPAs) are often advocated by ecologists as a method of conserving valuable fish stocks while ensuring the integrity of ecological processes in the face of increasing anthropogenic disturbance. In the Turks and Caicos Islands there is little evidence that current MPAs are ecologically beneficial but there are indications that boundary changes may enhance queen conch and finfish production. Implementing boundary changes usually requires political will and, hence, quantifiable economic ...
Journal of Experimental Marine Biology and Ecology, 2017
Density-dependent settlement, growth and mortality are often the major factors controlling recrui... more Density-dependent settlement, growth and mortality are often the major factors controlling recruitment success of recently-settled marine fishes. During this stage, juvenile fishes generally have spatial refuges from predation, and forage in limited but risky areas near refuges. Little is known about the mechanisms by which the tradeoff between feeding and refuge use lead to density dependent mortality. Foraging arena theory predicts that feeding activity should depend strongly on juvenile density and predation risk. Selection should act on the time that juveniles spend foraging, so as to strike a balance between growth and mortality. Because the risk of predation also varies with habitat, it is expected that variation in foraging times and resulting growth and mortality rates will be habitat-specific and density-dependent. This study tested these concepts by respirometric measurement of the metabolic cost of feeding and shelter site defense in young-of-year cunner (Tautogolabrus adspersus) in the northwest Atlantic. Metabolic costs were applied to time budgets measured in the field to estimate in-situ energy budgets. Contrary to expectation, time and energy spent on foraging increased as habitat complexity or conspecific density decreased. Time and energy spent on refuge defense increased with increasing predation risk (as mediated by habitat complexity) or conspecific density, highlighting the importance of refuge for a species that enters torpor at night and during the winter. Future recruitment studies should include examination of spatial habitat use by juveniles, and the behavioral and physiological mechanisms for adjusting behavior to varying food density and predation risk.
SUMMARY Marine reserves are widely considered to potentially benefit reef fisheries through emigr... more SUMMARY Marine reserves are widely considered to potentially benefit reef fisheries through emigration, yet the empirical basis for predicting the extent of this for small reserves is weak. The effects of fishing pressure and habitat on biomass and catch per unit effort (CPUE) of three species of exploited reef fish were studied at South Caicos, Turks and Caicos Islands. Distribution and abundance of hogfish (Lachnolaimus maximus) and white margate (Haemulon album) were inversely correlated with cover of fleshy macroalgae. Nassau grouper (Epinephelus striatus) were positively associated with vertical relief, but were unaffected by algal cover. Mean size, density, and biomass of hogfish were higher in a small (4 km 2) marine reserve than on fished reefs, as was biomass of white margate. CPUE of hogfish was inversely related to distance from the centre of the reserve, suggesting that spillover of this species from the reserve to adjacent reefs may enhance local yields, possibly providing economic incentives for fishers to comply with reserve regulations. Fishing pressure, however, had no apparent effect on Nassau grouper. Larger fishes and those that migrate to spawn, such as economically valuable Nassau grouper, may move over too large a range to be effectively protected by small marine reserves. Small reserves may not protect all fish, but they can increase the biomass of smaller or more sedentary reef fishes and may be a useful tool for the conservation or management of species such as hogfish. Other policy options, such as seasonal spawning closures or total allowable catches, need to be considered for larger, more mobile fishes in the Turks and Caicos Islands.
In recent years there has been increasing interest in conserving fish habitats. However, fish–hab... more In recent years there has been increasing interest in conserving fish habitats. However, fish–habitat associations, particularly nursery habitat for early juvenile stages, are poorly known for most reef fishes. Using mark–recapture techniques, I examined among-habitat variation in settlement, post-settlement growth, and persistence, and movement in 3 large, vulnerable, and commercially important reef fishes: the humphead wrasse Cheilinus undulatus, the squaretail coralgrouper Plectropomus areolatus, and the camouflage grouper Epinephelus polyphekadion. Both the humphead wrasse and the coralgrouper appeared to utilize specific nursery habitats. Settlement, growth, and persistence of humphead wrasse were highest in branching coral structures mixed with bushy macroalgae (BCMA). Of all tagged C. undulatus recaptured in intermediate or adult habitats, 80% were tagged post-settlement in BCMA. Early juvenile P. areolatus were found almost exclusively in coral rubble habitats on the slopes of tidal channels, at a narrow depth range of 5 to 7 m. This dependence on one habitat type could render this species vulnerable to shipping or dredging operations or other forms of coastal development. E. polyphekadion appeared to be a habitat generalist, and no specific nursery habitat could be identified. In summary, spatial management (e.g. implementation of marine protected areas) should prioritize habitats for conservation according to their value as essential nursery or spawning habitats for target species needing protection.
Settlement and growth of age 0+ cod were monitored using snorkel and self-contained underwater br... more Settlement and growth of age 0+ cod were monitored using snorkel and self-contained underwater breathing apparatus (SCUBA) in four distinct habitat types (sand, seagrass, cobble, and rock reef) in St. Margaret's Bay, Nova Scotia. Newly settled cod were marked with acrylic dye, allowing repeated visual length estimates of individual fish. Settlement of cod did not differ between habitat types, but postsettlement survival and subsequent juvenile densities were higher in-more structurally complex habitats. These differences appear to be due to increased shelter availability and decreased predator efficiency in structurally complex habitats. Growth rate was highest in seagrass beds, while the efficiency sf cod predators was lowest and cod survival was highest om rocky reefs and cobble bottoms. Thus, trade-offs occur between energy gain and predation risk. In St. Margaret's Bay, the population structure of Atlantic cod may be less influenced by patterns of larval supply than by postsettlement processes such as habitat-specific growth and mortality.
Marine reserves are considered to be a central tool for marine ecosystem-based management in trop... more Marine reserves are considered to be a central tool for marine ecosystem-based management in tropical inshore ¢sheries. The arguments supporting marine reserves are often based on both the nonmarket values of ecological amenities marine reserves provide and the pragmatic cost-saving advantages relating to reserve monitoring and enforcement. Marine reserves are, however, only one of a suite of possible policy options that might be used to achieve conservation and ¢sheries management objectives, and have rarely been the focus of rigorous policy analyses that consider a full range of economic costs and bene¢ts, including the transaction costs of management. If credible analyses are not undertaken, there is a danger that current enthusiasm for marine reserves may wane as economic performance fails to meet presumed potential. Fully accounting for the value of ecological services £owing from marine reserves requires consideration of increased size and abundance of focal species within reserve boundaries , emigration of target species from reserves to adjacent ¢shing grounds, changes in ecological resilience and behavioural responses of ¢shers to spatially explicit closures. Expanding policy assessments beyond standard cost^bene¢t analysis (CBA) also requires considering the impact of social capital on the costs of managing ¢sheries. In the short term, the amount of social capital that communities possess and the capacity of the state to support the rights of individuals and communities will a¡ect the relative e⁄ciency of marine reserves. Reserves may be the most e⁄cient policy option when both community and state capacity is high, but may not be when one and/or the other is weak. In the longer term, the level of social capital that a society possesses and the level of uncertainty in ecological and social systems will also impact the appropriate level of devolution or decentralization of ¢sheries governance. Determining the proper balance of the state and the community in tropical ¢sheries governance will require broad comparative studies of marine reserves and alternative policy tools.
Since many fisheries are size-selective, the establishment of marine protected areas (MPAs) is ex... more Since many fisheries are size-selective, the establishment of marine protected areas (MPAs) is expected to increase both the average size and abundance of exploited species, such as the valuable but vulnerable Nassau grouper (Epinephelus striatus). Increases in mean size and/or abundance of protected species within MPAs may also provide nonextractive economic value to recreationalists. In this research, we assessed scuba diver preferences for viewing Nassau grouper and the marginal trade-offs that divers exhibited between fish size and abundance and between dive group size and price in the Turks and Caicos Islands. We used results from a paired comparison conjoint survey to develop market share simulations of dive site choice. Market shares increased significantly for sites with increased Nassau grouper abundance and mean size. This implies that Nassau groupers provide nonextractive economic value to divers. Our results suggest that accounting for the nonextractive value of increased fish abundance and size may influence the economic viability of MPAs.
Settlement, growth and post-settlement mortality of the cunner (Tautogolabrus adspersus Walbaum) ... more Settlement, growth and post-settlement mortality of the cunner (Tautogolabrus adspersus Walbaum) was investigated on isolated boulder reefs in St. Margaret's Bay, Nova Scotia. Populations of cunner on these reefs were subjected to experimental manipulations of adult and recruit population density. Settlement of cunner was unaffected by the density of prior resident adults. Elevation of adult densities to approximately twice natural levels resulted in complete mortality of newly settled fish, while removal of adults resulted in enhanced growth and recruitment success over natural populations. This clearly demonstrates that natural populations of cunner in St. Margaret's Bay are sufficiently high to result in density-dependent growth and post-settlement mortality. Growth and mortality of newly settled fish were also suppressed by high recruit densities and enhanced by low densities of conspecific recruits. On all study reefs, newly settled cunner formed social dominance hierarchies, and both growth rate and post-settlement survival were positively correlated with fish size. Recruitment success of species such as cunner, for which post-settlement mortality is size-dependent, may be strongly influenced by processes affecting growth rate.
Difficulties in scaling up theoretical and experimental results have raised controversy over the ... more Difficulties in scaling up theoretical and experimental results have raised controversy over the consequences of biodiversity loss for the functioning of natural ecosystems. Using a global survey of reef fish assemblages, we show that in contrast to previous theoretical and experimental studies, ecosystem functioning (as measured by standing biomass) scales in a non-saturating manner with biodiversity (as measured by species and functional richness) in this ecosystem. Our field study also shows a significant and negative interaction between human population density and biodiversity on ecosystem functioning (i.e., for the same human density there were larger reductions in standing biomass at more diverse reefs). Human effects were found to be related to fishing, coastal development, and land use stressors, and currently affect over 75% of the world's coral reefs. Our results indicate that the consequences of biodiversity loss in coral reefs have been considerably underestimated based on existing knowledge and that reef fish assemblages, particularly the most diverse, are greatly vulnerable to the expansion and intensity of anthropogenic stressors in coastal areas.
Fisheries is a vital sector in the Philippine economy, providing a significant source of both dom... more Fisheries is a vital sector in the Philippine economy, providing a significant source of both domestic and export earnings while meeting essential food security and nutritional requirements. However, marine resources in the Philippines are facing increasing pressure from overfishing, destructive fishing practices, habitat destruction, declining water quality and limited management capacity. Marine Protected Areas (MPAs) are part of the management strategy to address these issues but the majority of MPAs around the world do not meet their management objectives. This paper discusses the identification and testing of management effectiveness indicators to evaluate MPA management for seven sites in the Philippines. The selection of 14 indicators was a participatory process that involved representatives from the academe, civil society groups, fishing associations, local government units (LGUs), national government agencies and research institutions. Overall, the majority of the indicators are rated positive but there is significant room for improvement, particularly in areas of resource use conflict, availability and allocation of resources and interaction between MPA managers and stakeholders. It is imperative that MPAs across the Philippines be managed and implemented as a network to maximize conservation and fisheries management. Moreover, given that the Philippines lies in the Coral Triangle area of the highest marine biodiversity in the world, increased political will and support for MPAs is urgently needed to meet global marine biodiversity targets and allow the Philippines to be an example of effective marine biodiversity conservation.
Recruitment and population density of coral reef fishes were studied on artificial and natural re... more Recruitment and population density of coral reef fishes were studied on artificial and natural reefs on the west coast of Barbados. Recruitment of all species combined and of 3 common species (Thalassoma bifasciatum, Stegastes partitus and Halichoeres garnoti) occurred mostly from May to November. Recruitment rate varied little across reef types and reef locations. Population density of all species combined and of the 3 common species varied little throughout the year, but did vary across reefs and locations. The observation that patterns of seasonal and spatial variation in densities did not reflect the patterns of seasonal and spat~al variation in recruitment suggests that reef fish populations in Barbados may be primarily regulated by post-settlement events. Recruitment of all species combined and of the 3 common species was not affected by the density of all species combined. No evidence could be found for interspecific competition, i.e. a negat~ve relat~onship between the density of one species and the recruitment of another. However, recrultrnent of H garnoti was inhibited on some reefs by high dens~ties of conspecifics. Post-recruitment mortality of all species combined was not affected by denslty of all species. However, post-recruitment mortality of T bifasciatum and S. partitus was higher on reefs of hlgher conspecific density. These results provide ev~dence for the regulation of reef fish pop-ulat~ons In Barbados by post-settlement processes, and suggest that intraspecific interactions may be particularly important in limiting population size.
Does adult spillover (movement out of marine protected areas [MPAs]) of fish create a net export ... more Does adult spillover (movement out of marine protected areas [MPAs]) of fish create a net export of fish biomass from MPAs to adjacent fished reefs? Biomass of five commercial reef fish species was estimated by visual census within and outside three MPAs in Guam, Micronesia. For most species and sites, biomass was significantly higher within the MPAs than in adjacent fished sites. Movement of fishes into and out of the MPAs was determined by mark-recapture experiments, in which fishes were tagged both inside and outside of MPAs. Four out of five species studied showed little or no net movement out of MPAs. However, the orangespine surgeonfish (Naso lituratus) showed a net spillover of biomass from all three MPAs; 21.5% of tagged individuals and 29% of the tagged biomass emigrated from MPAs. Patterns of spillover were strongly influenced by physical habitat barriers, such as channels, headlands, or other topographic features. MPAs that are physically connected by contiguous reef structures will likely provide more spillover to adjacent fished sites than those that are separated by habitat barriers. This study demonstrates that MPAs can enhance export of fish biomass to fished areas, but spillover is species-specific and depends on factors such as species size and mobility.
Serranids are important components of artisanal and commercial catch worldwide, but are highly su... more Serranids are important components of artisanal and commercial catch worldwide, but are highly susceptible to overfishing. In Pohnpei (Micronesia), a recent coral reef Wsh market survey revealed a reliance on night-time spearWshing and a serranid catch composed primarily of juveniles and small adults of practically all epinepheline species. Fishing effort was concentrated in one of Wve municipalities and was disproportionate to the population distribution. Lagoon areas were fished preferentially to outer reef areas, with both catch size distribution and species composition similar between the two areas. Some species were unique to a particular gear type, but catch composition did not vary substantially between spear and line fishing. Existing seasonal sales bans, meant to protect reproductively active serranids, appeared to place additional pressure on other families during ban periods. The study identified the need for a comprehensive management plan that merges traditional measures, including size limits and gear restrictions, with precautionary management tools. SpeciWcally, the scale and scope of marine protected areas should be increased to protect juveniles and other life history stages over wider areas than currently employed.
Fish assemblages on four large (100 m 2) artificial reefs were censused in May, June and July, 19... more Fish assemblages on four large (100 m 2) artificial reefs were censused in May, June and July, 1986 and again in May 1988. The mean coefficient of variation of species' relative density decreased from 1986 to 1988, while the mean percent similarity of fish assemblages increased from 1986 to 1988. Fish assemblages on two of the large artificial reefs and on equal areas of the nearest natural coral reef were censused biweekly for 12 mo. Neither reef type (artificial or natural) nor reef location appeared to have an effect on assemblage structure. Fish assemblages on six small (1 m 2) concrete block reefs were censused biweekly for 12 mo; three of the six reefs were denuded at 3-mo intervals. Assemblages on these small reefs were less predictable than those on the large artificial and natural reefs. Predictability of fish assemblages on large and small reefs generally increased with number of species present, but was not consistently related to total number of individuals present. Values of assemblage similarity varied from agreement with Australian studies, which generally espouse recruitment-limited, non-equilibrial assemblage structure, to agreement with other Caribbean studies, which generally espouse stable, resource-limited assemblage structure. It is concluded that the dichotomy of results between Australian and Caribbean studies of reef fish assemblage structure is primarily a result of different sampling methodology and analysis coupled with different species pools, and requires no difference in biological mechanism.
Coral reefs provide ecosystem goods and services for millions of people in the tropics, but reef ... more Coral reefs provide ecosystem goods and services for millions of people in the tropics, but reef conditions are declining worldwide. Effective solutions to the crisis facing coral reefs depend in part on understanding the context under which different types of conservation benefits can be maximized. Our global analysis of nearly 1,800 tropical reefs reveals how the intensity of human impacts in the surrounding seascape, measured as a function of human population size and accessibility to reefs (" gravity "), diminishes the effectiveness of marine reserves at sustaining reef fish biomass and the presence of top predators, even where compliance with reserve rules is high. Critically, fish biomass in high-compliance marine reserves located where human impacts were intensive tended to be less than a quarter that of reserves where human impacts were low. Similarly, the probability of encountering top predators on reefs with high human impacts was close to zero, even in high-compliance marine reserves. However, we find that the relative difference between openly fished sites and reserves (what we refer to as conservation gains) are highest for fish biomass (excluding predators) where human impacts are moderate and for top predators where human impacts are low. Our results illustrate critical ecological trade-offs in meeting key conservation objectives: reserves placed where there are moderate-to-high human impacts can provide substantial conservation gains for fish biomass, yet they are unlikely to support key ecosystem functions like higher-order predation, which is more prevalent in reserve locations with low human impacts. marine reserves | fisheries | coral reefs | social-ecological | socioeconomic T he world's coral reefs are rapidly degrading (1–3), which is diminishing ecological functioning and potentially affecting the well-being of the millions of people with reef-dependent livelihoods (4). Global climate change and local human impacts (such as fishing) are pervasive drivers of reef degradation (1, 5). In Significance Marine reserves that prohibit fishing are a critical tool for sustaining coral reef ecosystems, yet it remains unclear how human impacts in surrounding areas affect the capacity of marine reserves to deliver key conservation benefits. Our global study found that only marine reserves in areas of low human impact consistently sustained top predators. Fish biomass inside marine reserves declined along a gradient of human impacts in surrounding areas; however, reserves located where human impacts are moderate had the greatest difference in fish biomass compared with openly fished areas. Reserves in low human-impact areas are required for sustaining ecological functions like high-order predation, but reserves in high-impact areas can provide substantial conservation gains in fish biomass.
von Herbing, IH and M. Tupper. The implications of localized fishery stocks. Natural Resource, Agriculture, and Engineering Service. Ithaca, New York, 1997
The effects of a non-extractive marine reserve on the recruitment dynamics of haemulid fishes and... more The effects of a non-extractive marine reserve on the recruitment dynamics of haemulid fishes and their predators on Barbados coral reefs were studied using visual census and mark-recapture methods. Size and abundance of piscivores (including large adult grunts) known to prey on grunts were greater within the reserve than on adjacent reefs, whereas size and abundance of older juvenile grunts did not differ between protected and exploited reefs. Recruitment and early juvenile abundance were lower within the reserve and were ...
Marine Protected Areas (MPAs) are often advocated by ecologists as a method of conserving valuabl... more Marine Protected Areas (MPAs) are often advocated by ecologists as a method of conserving valuable fish stocks while ensuring the integrity of ecological processes in the face of increasing anthropogenic disturbance. In the Turks and Caicos Islands there is little evidence that current MPAs are ecologically beneficial but there are indications that boundary changes may enhance queen conch and finfish production. Implementing boundary changes usually requires political will and, hence, quantifiable economic ...
Journal of Experimental Marine Biology and Ecology, 2017
Density-dependent settlement, growth and mortality are often the major factors controlling recrui... more Density-dependent settlement, growth and mortality are often the major factors controlling recruitment success of recently-settled marine fishes. During this stage, juvenile fishes generally have spatial refuges from predation, and forage in limited but risky areas near refuges. Little is known about the mechanisms by which the tradeoff between feeding and refuge use lead to density dependent mortality. Foraging arena theory predicts that feeding activity should depend strongly on juvenile density and predation risk. Selection should act on the time that juveniles spend foraging, so as to strike a balance between growth and mortality. Because the risk of predation also varies with habitat, it is expected that variation in foraging times and resulting growth and mortality rates will be habitat-specific and density-dependent. This study tested these concepts by respirometric measurement of the metabolic cost of feeding and shelter site defense in young-of-year cunner (Tautogolabrus adspersus) in the northwest Atlantic. Metabolic costs were applied to time budgets measured in the field to estimate in-situ energy budgets. Contrary to expectation, time and energy spent on foraging increased as habitat complexity or conspecific density decreased. Time and energy spent on refuge defense increased with increasing predation risk (as mediated by habitat complexity) or conspecific density, highlighting the importance of refuge for a species that enters torpor at night and during the winter. Future recruitment studies should include examination of spatial habitat use by juveniles, and the behavioral and physiological mechanisms for adjusting behavior to varying food density and predation risk.
SUMMARY Marine reserves are widely considered to potentially benefit reef fisheries through emigr... more SUMMARY Marine reserves are widely considered to potentially benefit reef fisheries through emigration, yet the empirical basis for predicting the extent of this for small reserves is weak. The effects of fishing pressure and habitat on biomass and catch per unit effort (CPUE) of three species of exploited reef fish were studied at South Caicos, Turks and Caicos Islands. Distribution and abundance of hogfish (Lachnolaimus maximus) and white margate (Haemulon album) were inversely correlated with cover of fleshy macroalgae. Nassau grouper (Epinephelus striatus) were positively associated with vertical relief, but were unaffected by algal cover. Mean size, density, and biomass of hogfish were higher in a small (4 km 2) marine reserve than on fished reefs, as was biomass of white margate. CPUE of hogfish was inversely related to distance from the centre of the reserve, suggesting that spillover of this species from the reserve to adjacent reefs may enhance local yields, possibly providing economic incentives for fishers to comply with reserve regulations. Fishing pressure, however, had no apparent effect on Nassau grouper. Larger fishes and those that migrate to spawn, such as economically valuable Nassau grouper, may move over too large a range to be effectively protected by small marine reserves. Small reserves may not protect all fish, but they can increase the biomass of smaller or more sedentary reef fishes and may be a useful tool for the conservation or management of species such as hogfish. Other policy options, such as seasonal spawning closures or total allowable catches, need to be considered for larger, more mobile fishes in the Turks and Caicos Islands.
In recent years there has been increasing interest in conserving fish habitats. However, fish–hab... more In recent years there has been increasing interest in conserving fish habitats. However, fish–habitat associations, particularly nursery habitat for early juvenile stages, are poorly known for most reef fishes. Using mark–recapture techniques, I examined among-habitat variation in settlement, post-settlement growth, and persistence, and movement in 3 large, vulnerable, and commercially important reef fishes: the humphead wrasse Cheilinus undulatus, the squaretail coralgrouper Plectropomus areolatus, and the camouflage grouper Epinephelus polyphekadion. Both the humphead wrasse and the coralgrouper appeared to utilize specific nursery habitats. Settlement, growth, and persistence of humphead wrasse were highest in branching coral structures mixed with bushy macroalgae (BCMA). Of all tagged C. undulatus recaptured in intermediate or adult habitats, 80% were tagged post-settlement in BCMA. Early juvenile P. areolatus were found almost exclusively in coral rubble habitats on the slopes of tidal channels, at a narrow depth range of 5 to 7 m. This dependence on one habitat type could render this species vulnerable to shipping or dredging operations or other forms of coastal development. E. polyphekadion appeared to be a habitat generalist, and no specific nursery habitat could be identified. In summary, spatial management (e.g. implementation of marine protected areas) should prioritize habitats for conservation according to their value as essential nursery or spawning habitats for target species needing protection.
Settlement and growth of age 0+ cod were monitored using snorkel and self-contained underwater br... more Settlement and growth of age 0+ cod were monitored using snorkel and self-contained underwater breathing apparatus (SCUBA) in four distinct habitat types (sand, seagrass, cobble, and rock reef) in St. Margaret's Bay, Nova Scotia. Newly settled cod were marked with acrylic dye, allowing repeated visual length estimates of individual fish. Settlement of cod did not differ between habitat types, but postsettlement survival and subsequent juvenile densities were higher in-more structurally complex habitats. These differences appear to be due to increased shelter availability and decreased predator efficiency in structurally complex habitats. Growth rate was highest in seagrass beds, while the efficiency sf cod predators was lowest and cod survival was highest om rocky reefs and cobble bottoms. Thus, trade-offs occur between energy gain and predation risk. In St. Margaret's Bay, the population structure of Atlantic cod may be less influenced by patterns of larval supply than by postsettlement processes such as habitat-specific growth and mortality.
Marine reserves are considered to be a central tool for marine ecosystem-based management in trop... more Marine reserves are considered to be a central tool for marine ecosystem-based management in tropical inshore ¢sheries. The arguments supporting marine reserves are often based on both the nonmarket values of ecological amenities marine reserves provide and the pragmatic cost-saving advantages relating to reserve monitoring and enforcement. Marine reserves are, however, only one of a suite of possible policy options that might be used to achieve conservation and ¢sheries management objectives, and have rarely been the focus of rigorous policy analyses that consider a full range of economic costs and bene¢ts, including the transaction costs of management. If credible analyses are not undertaken, there is a danger that current enthusiasm for marine reserves may wane as economic performance fails to meet presumed potential. Fully accounting for the value of ecological services £owing from marine reserves requires consideration of increased size and abundance of focal species within reserve boundaries , emigration of target species from reserves to adjacent ¢shing grounds, changes in ecological resilience and behavioural responses of ¢shers to spatially explicit closures. Expanding policy assessments beyond standard cost^bene¢t analysis (CBA) also requires considering the impact of social capital on the costs of managing ¢sheries. In the short term, the amount of social capital that communities possess and the capacity of the state to support the rights of individuals and communities will a¡ect the relative e⁄ciency of marine reserves. Reserves may be the most e⁄cient policy option when both community and state capacity is high, but may not be when one and/or the other is weak. In the longer term, the level of social capital that a society possesses and the level of uncertainty in ecological and social systems will also impact the appropriate level of devolution or decentralization of ¢sheries governance. Determining the proper balance of the state and the community in tropical ¢sheries governance will require broad comparative studies of marine reserves and alternative policy tools.
Since many fisheries are size-selective, the establishment of marine protected areas (MPAs) is ex... more Since many fisheries are size-selective, the establishment of marine protected areas (MPAs) is expected to increase both the average size and abundance of exploited species, such as the valuable but vulnerable Nassau grouper (Epinephelus striatus). Increases in mean size and/or abundance of protected species within MPAs may also provide nonextractive economic value to recreationalists. In this research, we assessed scuba diver preferences for viewing Nassau grouper and the marginal trade-offs that divers exhibited between fish size and abundance and between dive group size and price in the Turks and Caicos Islands. We used results from a paired comparison conjoint survey to develop market share simulations of dive site choice. Market shares increased significantly for sites with increased Nassau grouper abundance and mean size. This implies that Nassau groupers provide nonextractive economic value to divers. Our results suggest that accounting for the nonextractive value of increased fish abundance and size may influence the economic viability of MPAs.
Settlement, growth and post-settlement mortality of the cunner (Tautogolabrus adspersus Walbaum) ... more Settlement, growth and post-settlement mortality of the cunner (Tautogolabrus adspersus Walbaum) was investigated on isolated boulder reefs in St. Margaret's Bay, Nova Scotia. Populations of cunner on these reefs were subjected to experimental manipulations of adult and recruit population density. Settlement of cunner was unaffected by the density of prior resident adults. Elevation of adult densities to approximately twice natural levels resulted in complete mortality of newly settled fish, while removal of adults resulted in enhanced growth and recruitment success over natural populations. This clearly demonstrates that natural populations of cunner in St. Margaret's Bay are sufficiently high to result in density-dependent growth and post-settlement mortality. Growth and mortality of newly settled fish were also suppressed by high recruit densities and enhanced by low densities of conspecific recruits. On all study reefs, newly settled cunner formed social dominance hierarchies, and both growth rate and post-settlement survival were positively correlated with fish size. Recruitment success of species such as cunner, for which post-settlement mortality is size-dependent, may be strongly influenced by processes affecting growth rate.
Difficulties in scaling up theoretical and experimental results have raised controversy over the ... more Difficulties in scaling up theoretical and experimental results have raised controversy over the consequences of biodiversity loss for the functioning of natural ecosystems. Using a global survey of reef fish assemblages, we show that in contrast to previous theoretical and experimental studies, ecosystem functioning (as measured by standing biomass) scales in a non-saturating manner with biodiversity (as measured by species and functional richness) in this ecosystem. Our field study also shows a significant and negative interaction between human population density and biodiversity on ecosystem functioning (i.e., for the same human density there were larger reductions in standing biomass at more diverse reefs). Human effects were found to be related to fishing, coastal development, and land use stressors, and currently affect over 75% of the world's coral reefs. Our results indicate that the consequences of biodiversity loss in coral reefs have been considerably underestimated based on existing knowledge and that reef fish assemblages, particularly the most diverse, are greatly vulnerable to the expansion and intensity of anthropogenic stressors in coastal areas.
Fisheries is a vital sector in the Philippine economy, providing a significant source of both dom... more Fisheries is a vital sector in the Philippine economy, providing a significant source of both domestic and export earnings while meeting essential food security and nutritional requirements. However, marine resources in the Philippines are facing increasing pressure from overfishing, destructive fishing practices, habitat destruction, declining water quality and limited management capacity. Marine Protected Areas (MPAs) are part of the management strategy to address these issues but the majority of MPAs around the world do not meet their management objectives. This paper discusses the identification and testing of management effectiveness indicators to evaluate MPA management for seven sites in the Philippines. The selection of 14 indicators was a participatory process that involved representatives from the academe, civil society groups, fishing associations, local government units (LGUs), national government agencies and research institutions. Overall, the majority of the indicators are rated positive but there is significant room for improvement, particularly in areas of resource use conflict, availability and allocation of resources and interaction between MPA managers and stakeholders. It is imperative that MPAs across the Philippines be managed and implemented as a network to maximize conservation and fisheries management. Moreover, given that the Philippines lies in the Coral Triangle area of the highest marine biodiversity in the world, increased political will and support for MPAs is urgently needed to meet global marine biodiversity targets and allow the Philippines to be an example of effective marine biodiversity conservation.
Recruitment and population density of coral reef fishes were studied on artificial and natural re... more Recruitment and population density of coral reef fishes were studied on artificial and natural reefs on the west coast of Barbados. Recruitment of all species combined and of 3 common species (Thalassoma bifasciatum, Stegastes partitus and Halichoeres garnoti) occurred mostly from May to November. Recruitment rate varied little across reef types and reef locations. Population density of all species combined and of the 3 common species varied little throughout the year, but did vary across reefs and locations. The observation that patterns of seasonal and spatial variation in densities did not reflect the patterns of seasonal and spat~al variation in recruitment suggests that reef fish populations in Barbados may be primarily regulated by post-settlement events. Recruitment of all species combined and of the 3 common species was not affected by the density of all species combined. No evidence could be found for interspecific competition, i.e. a negat~ve relat~onship between the density of one species and the recruitment of another. However, recrultrnent of H garnoti was inhibited on some reefs by high dens~ties of conspecifics. Post-recruitment mortality of all species combined was not affected by denslty of all species. However, post-recruitment mortality of T bifasciatum and S. partitus was higher on reefs of hlgher conspecific density. These results provide ev~dence for the regulation of reef fish pop-ulat~ons In Barbados by post-settlement processes, and suggest that intraspecific interactions may be particularly important in limiting population size.
Does adult spillover (movement out of marine protected areas [MPAs]) of fish create a net export ... more Does adult spillover (movement out of marine protected areas [MPAs]) of fish create a net export of fish biomass from MPAs to adjacent fished reefs? Biomass of five commercial reef fish species was estimated by visual census within and outside three MPAs in Guam, Micronesia. For most species and sites, biomass was significantly higher within the MPAs than in adjacent fished sites. Movement of fishes into and out of the MPAs was determined by mark-recapture experiments, in which fishes were tagged both inside and outside of MPAs. Four out of five species studied showed little or no net movement out of MPAs. However, the orangespine surgeonfish (Naso lituratus) showed a net spillover of biomass from all three MPAs; 21.5% of tagged individuals and 29% of the tagged biomass emigrated from MPAs. Patterns of spillover were strongly influenced by physical habitat barriers, such as channels, headlands, or other topographic features. MPAs that are physically connected by contiguous reef structures will likely provide more spillover to adjacent fished sites than those that are separated by habitat barriers. This study demonstrates that MPAs can enhance export of fish biomass to fished areas, but spillover is species-specific and depends on factors such as species size and mobility.
Serranids are important components of artisanal and commercial catch worldwide, but are highly su... more Serranids are important components of artisanal and commercial catch worldwide, but are highly susceptible to overfishing. In Pohnpei (Micronesia), a recent coral reef Wsh market survey revealed a reliance on night-time spearWshing and a serranid catch composed primarily of juveniles and small adults of practically all epinepheline species. Fishing effort was concentrated in one of Wve municipalities and was disproportionate to the population distribution. Lagoon areas were fished preferentially to outer reef areas, with both catch size distribution and species composition similar between the two areas. Some species were unique to a particular gear type, but catch composition did not vary substantially between spear and line fishing. Existing seasonal sales bans, meant to protect reproductively active serranids, appeared to place additional pressure on other families during ban periods. The study identified the need for a comprehensive management plan that merges traditional measures, including size limits and gear restrictions, with precautionary management tools. SpeciWcally, the scale and scope of marine protected areas should be increased to protect juveniles and other life history stages over wider areas than currently employed.
Fish assemblages on four large (100 m 2) artificial reefs were censused in May, June and July, 19... more Fish assemblages on four large (100 m 2) artificial reefs were censused in May, June and July, 1986 and again in May 1988. The mean coefficient of variation of species' relative density decreased from 1986 to 1988, while the mean percent similarity of fish assemblages increased from 1986 to 1988. Fish assemblages on two of the large artificial reefs and on equal areas of the nearest natural coral reef were censused biweekly for 12 mo. Neither reef type (artificial or natural) nor reef location appeared to have an effect on assemblage structure. Fish assemblages on six small (1 m 2) concrete block reefs were censused biweekly for 12 mo; three of the six reefs were denuded at 3-mo intervals. Assemblages on these small reefs were less predictable than those on the large artificial and natural reefs. Predictability of fish assemblages on large and small reefs generally increased with number of species present, but was not consistently related to total number of individuals present. Values of assemblage similarity varied from agreement with Australian studies, which generally espouse recruitment-limited, non-equilibrial assemblage structure, to agreement with other Caribbean studies, which generally espouse stable, resource-limited assemblage structure. It is concluded that the dichotomy of results between Australian and Caribbean studies of reef fish assemblage structure is primarily a result of different sampling methodology and analysis coupled with different species pools, and requires no difference in biological mechanism.
As a contributor to rural livelihoods, particularly those of coastal fishers, grouper aquaculture... more As a contributor to rural livelihoods, particularly those of coastal fishers, grouper aquaculture can generate potentially large financial benefits. The high value of grouper on the export market ensures that farmers are able to generate a profit even when stocks suffer heavy mortalities. Despite high initial investment costs, studies have shown that with appropriate support, even the poorest can benefit from grouper culture, with implications for both household well-being and community development. However, based on the information reviewed in this report, capture-based aquaculture may not be the best means to ensure a steady and sustainable supply of grouper for either the live or “non-live” fish trades. This is due to a number of problems including low availability of seed, destructive and wasteful seed collection techniques, removal of large numbers of early life history stages with subsequent impacts on adult populations and conflicts with capture fisheries, and pollution and disease resulting from culture operations.
This report is made possible by the generous support of the American people through the United St... more This report is made possible by the generous support of the American people through the United States Agency for International Development (USAID). The contents are the responsibility of The Nature Conservancy and its partners (CEBSE, FoPROBIM, C-CAM, and SusGren) and do not necessarily reflect the views of USAID or the United States Government.
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based on the information reviewed in this report, capture-based aquaculture may not be the best means to ensure a steady and sustainable supply of grouper for either the live or “non-live” fish trades. This is due to a number of problems including low availability of seed, destructive and wasteful seed collection techniques, removal of large numbers of
early life history stages with subsequent impacts on adult populations and conflicts with capture fisheries, and pollution and disease resulting from culture operations.