Relevant Degree Programs
India - costs and benefits of trawl fisheries China - threatened species and spatial planning Southeast Asia - emergence of biomass trawling IndoPacific - ecology and conservation of the seahorse Hippocampus kuda global - CITES and marine conservation ... and other projects compatible with my group's priority interests
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Graduate Student Supervision
Doctoral Student Supervision (Jan 2008 - Nov 2019)
Securing a healthy and biodiverse ocean is vital to our human wellbeing. However, marine conservation is challenging, especially for data-poor species, whose habitats and threats are understudied. My dissertation explored how to address such challenges at two large spatial scales (in China and globally), with a focus on the little studied seahorses (Hippocampus spp.). In the first two data chapters, I explored the utility of various sources of information about species and habitat covariates in species distribution models (SDMs). My results from the first chapter showed that local ecological knowledge provided useful biogeographic data of five Chinese seahorse species to predict their distributions, which were mainly associated with ocean temperature. My second chapter at the global scale indicated that integrating citizen sciences, museum collections, and research-grade data with continuous predictors derived the best SDM models; these models predicted reliable habitat maps for 33 out of 42 species that were primarily associated with depths, proximity to macrohabitats (e.g., sponges), pH, and ocean temperature.In the third analytical chapter, I explored global threat patterns and conservation status for 42 seahorse species with two cumulative-human-impact (CHI) models (spatial and non-spatial) and random forest (RF) models. I found that human-impact indices (from the CHI models) can be used to predict conservation status at high accuracies (87% and 96%) in RF models. Applying a non-spatial CHI model derived indices better predicted conservation status, while using a spatial CHI model identified distribution patterns of threats.In the fourth data chapter, I integrated the derived biogeographic and threat maps in a novel framework to set conservation priorities for seahorse habitats in China and globally, using Marxan software. I found that the two major outputs of Marxan (i.e., selection frequency and best solution) were useful to determine feasible priority solutions at large spatial scales. My results identified valuable datasets and approaches to advancing ecological and conservation knowledge for data-poor marine species, an essential precursor to action for the ocean.
International trade regulations are important tools to ensure sustainable use of wildlife, but their effects on marine fishes are rarely examined. In this thesis, I evaluated patterns and changes in international trade of marine fishes whose exports are regulated under the Convention on the International Trade in Endangered Species of Wild Flora and Fauna (CITES). I focused on the case study of seahorses (Hippocampus spp.), which were the first marine fishes with exports controlled under CITES (Appendix II) in 2002, but also investigate international trade for all animal species on Appendix II.In my first two research chapters, I investigated how implementation of CITES at the national level affected seahorse fisheries and trades. My study focused on Thailand, the country that has long exported the most seahorses. In Chapter 2, I showed that fishers reported different catch rates over varying reporting time periods. This correlation could greatly influence catch estimates and have implications for management that draws on fishers’ knowledge. In Chapter 3, I found that seahorse catch and domestic trade did not change after the Thai government set an export quota for seahorses, even though formal export data showed notable declines in volume. In my next two research chapters, I considered trade dynamics at the global scale. In Chapter 4, I found that once the CITES Appendix II listing came into effect, total weight of seahorses in documented global trade decreased, recorded seahorse exports became dominated by few countries, and prices for seahorses increased. In Chapter 5, I explored trade patterns for all CITES Appendix II animal species. I discovered that the USA appears to be the centre of reported wildlife trade but also that several Asian countries were emerging as important importers. I also found that the trade in marine fishes and non-coral invertebrates involved more countries with more connections than other Appendix II taxa.My thesis highlights the opportunities and limitations of using export controls in managing the trade in marine fishes. These findings have implications for the implementations of global agreement, wildlife trade monitoring and conservation effort prioritizing.
Growing human populations place multiple pressures on social-ecological systems, including coastal oceans. However, the effects of long-term and/or overlapping stressors remain poorly understood, particularly over large spatial scales. My dissertation evaluated how pressures from fishing and co-occurring stressors correspond to current ecological conditions in the Danajon Bank, a coral reef ecosystem in the central Philippines. I used long-term local ecological knowledge (LEK) to map fishing practices (1950-2010) and high spatial resolution satellite imagery to map coastal habitats. This innovative suite of methods enabled me to examine patterns over broader spatial scales and longer time periods than those usually assessed. I met five primary objectives: (1) quantify the spatio-temporal dynamics of fishing effort and gear use; (2) examine the influence of fisheries governance; (3) map the spatial distribution of benthic (seafloor) habitats; (4) model the spatial distribution of living corals in relation to co-occurring stressors and biophysical conditions; and (5) explore the conservation implications of these relationships. While individuals’ fishing practices were fairly consistent over time, this small-scale fishery has changed dramatically. First, total fishing effort (days per year fished by all fishers) accelerated between 1960 and 2010 because of rapid growth in the number of fishers. Aggregate fishing effort increased almost 2.5-fold and spatially-explicit fishing effort increased over 20-fold. Second, the areal extent of fishing grounds expanded greatly. Third, use of fishing gears changed over time. Diversity of fishing gears increased, as did fishing effort with destructive, active, and non-selective gears. Considering the timing of these changes, I found a lasting influence of fishing policies, and small improvements in the sustainability of fishing gears following implementation of co-management. Finally, I found that the probability that an area supported living corals was affected by fishing through both long- & short-term mechanisms, and I documented strong coral-landscape relationships. My research demonstrates that to strengthen ocean conservation, it will be essential to reduce the frequency and intensity of stressors, remove some areas from exploitation, foster resilience traits of ecosystems, gather data to better understand systems, and strengthen the institutions that can support these endeavors.
In this thesis I explore how to develop conservation action strategically for data-poor marine fishes. The dearth of information about populations, habitats and threats for many marine fishes makes it difficult to know how or where to initiate conservation strategies. My PhD research explores what type of information is essential for conservation management, and how it can be generated and applied for data-poor marine fishes. I use the case study of seahorses (Hippocampus spp), because they are notoriously understudied and yet their trade is regulated under the Convention on International Trade in Endangered Species (CITES). I further focus on Thailand, the largest exporter of seahorses, which has come under considerable international scrutiny. In my first two chapters I generated the spatial data that are vital to support conservation and management efforts. My results showed that using local knowledge to inform a presence / absence study, one that incorporated detection probabilities, was the most expedient way to produce the necessary spatial data. In my next two chapters I explored two approaches to understanding incidental capture of data-poor species in non-selective fishing gear. I found that vulnerability analysis yielded greater return on fewer data than data-poor fisheries stock assessment. However, data-poor fishery stock assessment made it possible to estimate stock status and revise management measures. For my fifth chapter, I applied findings from my previous chapters to meet CITES obligations, by assuming the role of a Thai government agent confronted with the external technical advice that I had generated. I found that implementation was most successful if I addressed three main questions: (1) What are the pressures on species?; (2) Is management in place to mitigate those pressures?; and (3) Are the species responding as hoped to management? My thesis highlights ways that management can move forward with limited data to address conservation issues for marine species. Some of these ways include valuing the use of local knowledge and using new advances in data-poor assessment methods in fisheries. Whenever fisheries are involved, conservationists need to respect the challenges that managers face in simultaneously seeking to protect wild species and meet human needs.
This dissertation provides new evidence for why women should be included in small-scale fisheries assessments. Women are commonly overlooked in fisheries science and management because they are assumed not to fish, or to fish very little. My research focuses on community-based managed fisheries in the Central Philippines. I begin with a literature review of women’s fishing around the world, revealing that it is common, diverse, and dynamic. Women fishers also often focus on species and habitats different from those in men’s fishing. Notably, however, the review also identified a considerable data gap in quantitative assessments of women’s fishing.I designed my case study specifically to quantify women’s contributions to the total community catch and effort. I found that women – who totaled 42% of all fishers – generated about one quarter of the total fishing effort and of the catch biomass. Explicit consideration of women’s fishing cast a spotlight on gleaning, an overlooked fishing method in which animals are collected in intertidal habitats. Almost all the women and half of the men gleaned. I found that gleaning primarily targeted sessile invertebrates, and was an important source of food, particularly when other fishing was not available. Marine management that affects gleaners – such as no-take marine protected areas (MPAs) placed in intertidal areas – needs to consider distinct ecological and social features of gleaning. On that basis, I used a gender lens to examine community-based management in the form of no-take MPAs. In this cultural context resource management is a male sphere, both in perception and in practice. Women were less likely to feel that the MPA had a positive effect on their fishing, with MPAs mostly identified as a management measure for finfish. Women were also less likely to participate actively in MPA management. In summary, my focus on women should prompt reexamination of how fishing is defined, who counts, and who is counted. Integration of women’s issues into fisheries management requires attention to gleaning, and exploration of alternative management methods. To overlook women, however, creates substantial underestimation of fishing labour and catch – with consequent worsening of our prospects for fisheries management globally.
In this thesis I quantify habitat use, movement, and vulnerability for seahorses and other sedentary fishes to understand how they may respond to habitat related threats. Surviving habitat change depends on either acclimatizing or escaping. Sedentary animals could be especially vulnerable if they require specific habitats or their ability to escape is reduced. However, dynamic coastal environments could promote greater flexibility in fish living there.Populations of the sedentary seahorse Hippocampus guttulatus living in a dynamic estuary seem flexible in their habitat use, but individuals may be less so. I explored H.guttulatus habitat associations using underwater surveys and displacement experiments in the Ria Formosa lagoon. Seahorse populations declined substantially (73-94%) compared to previous surveys, but declines were unassociated with measured habitat changes. At low densities, H.guttulatus lived in a range of habitats but in warmer, deeper locations. When displaced, H.guttulatus moved to a variety of environments but individual seahorses moved towards locations with familiar depths and current speeds. Individual variability could help protect populations in degrading habitat but individuals may still need to move to survive. Hippocampus guttulatus can move further than their small home ranges would suggest, which might help them escape habitat loss and degradation. In aquarium experiments I showed that small acoustic tags could be used on captive H.guttulatus with minimal effects on movement and behaviour. I displaced tagged H.guttulatus and found they moved ten times further than typical home range movements. While H.guttulatus shows some capacity for acclimatizing and escaping, their sedentary nature could confer vulnerability to habitat loss and degradation. Models simulating fish movement across artificial seascapes predicted sedentary fish should be more sensitive to habitat loss and fragmentation than more mobile fish. Comparative analyses of movement and vulnerability among marine benthic fish species supported these results. Among fishes threatened by habitat degradation, those that rarely move beyond home ranges were more threatened than those that migrate or disperse.My thesis identified general relationships between movement and vulnerability in marine fishes, which could help prioritize conservation, while raising further questions about the additional effects of habitat specialization and environmental variability.
This dissertation casts new light on reconciling fisheries and conservation. This reconciliation is particularly challenging for small-scale fisheries, because they are data-poor, but it is necessary to sustain biodiversity and food security. My research focuses on a typical small-scale fishery in the Central Philippines that catches seahorses.I begin by providing an historic reconstruction of seahorse catch rates, the first of its kind despite a multi-decade, global trade for seahorses. I quantified fisher perceptions of the decline in trade to set historic baselines. Results showed that relying solely on recent decades of data could underestimate IUCN Red List extinction risk for historically exploited fish such as my study species, Hippocampus comes.My research contributed robust approaches to incorporating fisher knowledge into quantitative assessments. I developed a novel approach to correct for inaccuracies in fishers’ memories of past events and showed, for the first time, that conservation assessments are sensitive to assumptions made when analyzing local knowledge. Comparisons I made between catch rate trends estimated by resource users and those obtained using standard approaches (catch landings or underwater surveys) suggest that fisher interviews or logbooks are a reasonable proxy for more costly ‘scientific’ methods. In contrast, interviews do not allow inferences about the absolute value of catch rates at scales relevant to management/conservation.My findings raise questions about the assumed sustainability of small-scale fisheries and identified new strategies to protect them. I conducted a novel analysis of spatial fishing behaviour that illustrates the capacity of small-scale fisheries to exert considerable cumulative pressure on marine systems, despite their seemingly benign gears.Finally, I conducted the first study on how depth refugia might help sustain coral-reef fish populations by combining fisheries modeling with IUCN Red List conservation assessments. Results emphasize the importance of locating some protected areas at depths inaccessible to small-scale fishers. Such tactics will contribute towards safeguarding biodiversity and food security in coral reef ecosystems.In summary, my thesis takes valuable steps towards finding solutions for marine biodiversity and fisheries crises; it uses pragmatic approaches to deduce key information that is highly relevant to the futures of coral-reef fish and small-scale fisheries.
Despite an expansion of marine protected areas (MPAs), a big gap exists in monitoring and evaluating their effectiveness. In less developed countries such as the Philippines, community-based (CB) MPAs have flourished. This thesis focused on exploring how local communities identify indicators of MPA effectiveness and subsequently monitor and evaluate an MPA. I first examined the process of MPA policy development, and found that global targets may be unknown or meaningless to local communities because of limited localization of international and national policies. In response, I recommend the participation of legitimate multi-level representatives from a network of alliances that can effectively act to harmonize MPA policies. With the active engagement of communities in the central Philippines, I identified sets of indicators and criteria for evaluating CBMPA effectiveness and found they change over time as MPAs and local conditions evolved, e.g., communities associated with younger MPAs preferred the input and output types of indicators while those associated with older MPAs preferred outcome indicators. Changes in community expectations as the MPAs evolve also influenced the criteria for evaluation. Analyses of community indicator development, monitoring and evaluation processes indicated that the strongest determinant of participation was social association among the residents. The highest participation levels were recorded for men and youth. The suite of indicators used did not detect changes in the CBMPAs over two years of tracking. However, the monitoring process resulted in a shift from passive to active participation. During monitoring, community volunteers collected socio-economic data more easily than both enforcement and ecological data in terms of cost, time, skills and social fit. Standardized monitoring and evaluation can be sustained through legislation and institutionalization of management bodies. Also, CBMPA effectiveness indicators need to be developed iteratively to reflect the changing needs and perspectives of local stakeholders. The wider application of the methods and approaches generated from this thesis needs to be explored for other CBMPAs. Such research ensures that the effectiveness of MPA is evaluated. This is significant due to the commitment of countries to report on the progress of their MPAs by 2010, as set by the Convention on Biological Diversity.
My research, focused on the industrial shrimp fishery in southern Gulf of California, aimed to determine whether tropical shrimp trawling is a problem for viability of incidentally captured small fish species. My first objective was to use life history information to evaluate possible impacts on four small fish species from their incidental capture. I applied length based indicators and qualitative criteria to information on captured sizes, reproduction, and distributions across the study site. My results suggested potential for overfishing silver stardrum and bigscale goatfish, largely because most sampled individuals were immature. Silver stardrum may be particularly affected because its occurrence and density declined during the trawling season whereas goatfish apparently recruited to the study area. Most sampled sandperch were mature, suggesting greater resilience to trawling. In contrast, sampled lumptail searobin, although mature, had not yet spawned, indicating potential for adverse fishing effects. Because human behaviour affects the success of fisheries management, my second objective was to shed light on the social dimensions of tropical shrimp fisheries management. My interviews with industrial trawl fishers suggested that proper enforcement and reliable governance are essential for a sustainable fishery. If enforcement were strong, then most fishers would support trawl free areas. The effort data I gathered point to areas where protection might be socially acceptable. My third objective considered the biological appropriateness of trawl closures for small fishes. The divergent distributions of bigscale goatfish and silver stardrum, just two of many small species in bycatch, implied that trawl restrictions would have to cover many depths and latitudes. Further, although my matrix model was of limited use for assessing population status of silver stardrum, it clearly indicated that precautionary management should focus on increasing survival of younger fish. This could be achieved with trawl closures where smaller fish live. While the approaches I used identified small fishes that might be vulnerable to trawling, they are too data intensive to be viable for the hundreds of such species in bycatch, and too inconclusive to confirm impact. It may be necessary to apply precautionary methods such as trawl closures to avoid potential effects of indiscriminate trawling.
No-take marine reserves are a highly advocated tool to recover degraded marine ecosystems, but we have limited evidence as to how marine reserves facilitate recovery of marine communities. To address this limitation, we conducted monthly underwater visual censuses over three years on 423 reef fish species in eight sites where fishing had been excluded for different lengths of time. We then used our data to assess four impacts of protection within no-take marine reserves in the central Philippines: (1) magnitudes and rates of reef fish community recovery; (2) changes in reef fish diversity; (3) patterns of reef fish community succession; and (4) shifts in community interactions, based on distributions of pairwise correlations among reef fish species biomass. We found that total fish biomass increased with the duration of protection, but total fish abundance and species richness or diversity were both more influenced by site location than by reserve age. In addition, large-bodied herbivores drove the biomass recovery in older marine reserves, while small-bodied zoobenthivores and zooplanktivores influenced the higher abundance in offshore sites. Moreover, our results showed that ubiquitous large-bodied herbivore species (e.g. Chlorurus bleekeri) increased in biomass dominance in older reserves, whereas ubiquitous medium-bodied species (e.g. Thalassoma lunare) lost biomass dominance. Our non-metric multidimensional scaling (MDS) representation of reef fish community trajectories with duration of protection showed convergent trends in sites within similar locations relative to the mainland. Finally, the frequency distribution of pairwise correlation values among species biomass time-series within each site showed positive mean values regardless of protection-duration, as is typical of disturbed or high diversity systems. Indeed, less than ten percent of common species (those present in ≥50% of the 33 monthly surveys) within each site showed significant decline over time, while about 40 percent showed significant increase. In summary, our research provides comprehensive evidence on how marine reserves recover depleted reef fish communities. However, it also emphasizes that understanding of reef ecological processes could improve marine reserve site selection and design in order to meet specific conservation goals of marine reserve establishment.
This thesis provides the first direct comparison between – and integration of – community-based and science-based approaches to the establishment of marine protected areas (MPAs). MPAs are one potentially effective conservation tool, but are being established very slowly. My research shows that community involvement in placing MPAs can help meet many ecological goals, although biophysical data improve the conservation value of sitings.To assess the need for MPAs in British Columbia (BC), Canada, I mapped stressors resulting from human activities. This produced a powerful rationale for MPAs: very little of the ocean, and almost none of the continental shelf of BC, lies beyond the reach of human stressors.My work helps reconcile differing perspectives about the efficacy of community-based vs. science-based MPA selection. I explored and analyzed these approaches, separately and together, in two areas in BC. First, I generated a community-based plan for MPA placement through partnerships with two First Nations (indigenous peoples) in BC. They offered strong support for spatial protection measures, and individuals nominated overlapping areas. Second, I applied a decision support tool (Marxan) to determine MPA placement under scientific precepts. Conservation planning usually lacks detailed ecological information but the Marxan approach was robust to some missing data; in such cases, it was best to use available abiotic and biotic data to ensure that both habitats and species were represented. Third, I integrated community-based and science-based approaches, to find that they verified and complemented each other. Indeed, an integration of the two was preferred by participants and also achieved all conservation objectives. Finally, I took a novel and pragmatic approach to ocean zoning. I used spatial data for thirteen commercial fisheries on Canada’s west coast to select areas where fishing should be permitted, rather than prohibiting fishing under a MPA paradigm. The results revealed that small reductions in fisheries yields, if judiciously selected, could allow creation of large unfished areas that embraced diverse biophysical regions and habitat types. Such a pragmatic approach could achieve remarkable conservation gains.
Master's Student Supervision (2010 - 2018)
To confirm their effectiveness, long-term monitoring of marine protected areas (MPAs) is critical. Such longitudinal sampling can, however, pose problems of methodology, particularly as more preferred tools may evolve over time. My research sought to understand how two commonly used methods, line intercept transect (LIT) and photoquadrat (PQ), which were used sequentially in MPA monitoring, estimated percent coral cover in a series of MPAs in the central Philippines.It can be difficult to reconcile data from LIT and PQ because their different parameters and sample sizes can generate contradicting results. I specifically addressed the issues of (i) small sample sizes of LIT data because of a challenge in maintaining fixed transects and (ii) possible spatial autocorrelation of PQ data owing to a decision to place transects close together. The data also faced other problems, including numerous missing data points and inconsistent data labeling.Analyzing three years of data when both LIT and PQ were applied, I found that LIT estimated higher mean percent coral cover than PQ. However, subsampling LIT data – and thus increasing sample sizes – improved comparison of estimates by these two methods. This finding demonstrated that PQ data, with larger sample sizes from wider spatial ranges, detected significant temporal patterns of coral cover whereas LIT data did not. This result confirmed that more observations and a wider spatial extent of sampling increase the power to detect statistical significance. I also found that PQ data did not exhibit significant spatial autocorrelation, eliminating one of concerns in analyses.Two other aspects of monitoring also stand out in their importance for better assessment of coral cover. The first is the need for frequent communication between field biologists and researchers / analysts to assure the proper execution of sampling procedures and reporting of any changes to field methods. The second is the vital need to minimize errors by ensuring the accuracy of data encoding and use of standardized labeling systems over time. The quality of the data determines the accuracy of coral cover estimates, especially when different methods are used in MPA monitoring.
Overall, this thesis expands on our ecological understanding of a group of biologically diverse marine fishes by investigating how they are shaped by their habitats, prey, and predators. In my first data chapter, I used the seahorse Hippocampus whitei as a case study for investigating the ecological correlates of syngnathid abundance and distributions. Expanding on research that had looked at how either their habitats, prey, or predators affected their populations, I considered all three components in a single holistic approach. I investigated these correlations at two scales: among different seagrass beds (200-6000 m apart), and within a single seagrass bed (
The development of effective evidence-based management is limited by a lack of long-term records for many vulnerable marine species that are caught in small-scale fisheries. To address this data gap, I studied a small-scale fishery in southern Vietnam with a focus on seahorses (Hippocampus spp.), globally traded, cryptic fishes that are notably vulnerable to overexploitation. Using a combination of fisher interviews and catch landings surveys, I documented five fishing gears that regularly caught seahorses intentionally and/or incidentally: otter trawls, beam trawls, pair trawls, crab nets, and compressor diving. About 20% of fishers I studied specifically targeted seahorses and made the majority of their income from selling these fish; a novel finding. The seahorse catch consisted of three species – Hippocampus spinosissimus, H. kuda and H. trimaculatus – with catch composition varying by gear and fishing ground. Bottom trawl boats and compressor divers that targeted seahorses caught them at mean rates of 23 and 32 seahorses per day respectively, while those that caught seahorses incidentally caught 1 and 3 per day respectively. The total catch from the island from these two fishing methods was approximately 162,000–234,000 seahorses per year. This catch is up to four times higher than in other studied regions of Vietnam and throughout Southeast Asia. Fishers reported that seahorse catch rates had decreased by 86-95% from 2004 to 2014. Meanwhile, the landed value of seahorses had increased by 534% during the same time period, encouraging fishers to continue capturing and selling seahorses. These signs point toward a high-pressure fishery that is likely unsustainable. Fisheries management efforts in the area should be strengthened by enforcing marine protected areas and improving fishers’ compliance to regulation. My findings emphasize the transitions that can occur in a high-pressure small-scale fishery and highlight the need for effective management to ensure sustainable seahorse populations.
The incidental capture of marine organisms is a critical area of concern in fisheries management, and despite the dominance of small fishes in bycatch biomass around the globe, we know little about the impacts of bycatch on these small fishes. Here, I focus on one such small fish taxon, the seahorses (Hippocampus spp.). Seahorse populations are typically patchy, and they have a specialized life history that makes them more likely to be vulnerable to overfishing. I assessed the impacts of nonselective gear on seahorses in one country by examining potential impacts for three species in peninsular Malaysia. I also assessed the impacts of seahorse bycatch globally, by synthesizing a global array of studies. For my national analysis, I used data-poor assessment methods to estimate life history parameters for three species of seahorse in peninsular Malaysia (Chapter 2). For my global analysis, I extracted data found in a published and unpublished reports to generate a synthesis of global seahorse bycatch (Chapter 3). Nationally, my findings indicate the potential for overfishing for one species found in the southwest region of the peninsular Malaysia. Globally, my synthesis revealed that all fishing gears obtained seahorses in bycatch, but at very low rates of capture per vessel per day. Across all countries, fishers characterized seahorses as relatively rare in their bycatch and declining in catches. One key finding was that low CPUE scaled up to tens of millions of seahorses obtained globally as bycatch each year. My results address the impacts of bycatch on seahorses and discuss the implications for other small bycaught fish species, especially those that are demersal or rare.