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Using eOceans diver data to describe contemporary patterns of marine animal populations: A case study of sharks in Thailand
Abstract
Many marine animals around the world are threatened by a variety of anthropogenic activities, yet there is often a paucity of data to monitor patterns in abundance and distribution or to evaluate human interventions. The new citizen science program eOceans helps to fill this gap by gathering observations of various marine animals from worldwide ocean explorers. In 2012, a dedicated Thailand-wide census of sharks, and other animals, began as a collaboration between eOceans scientists and the dive tourism industry. Using the observations from 9524 dives (9357 h underwater) logged by 169 divers on 153 sites, we describe the spatial and temporal patterns of sharks in coastal Thailand. A total of 12 shark species were encountered, most commonly (67%) as individuals, and were observed on 11% of all dives, on 59% of sites, in all months and years. The two most frequently encountered species were blacktip reef (Carcharhinus melanopterus) and leopard sharks (Stegostoma fasciatum). Many species had peak encounter rates in summer, but aggregated in various seasons in different years. Mating events and nursery sites were rarely observed, and only for blacktip reef and whitetip reef (Triaenodon obesus) sharks. These results could be of value to species- or region-specific biologists, ecologists and fisheries scientists, as well as to managers and policy makers that could use the findings to monitor future trends and prioritize conservation strategies. Moreover, this study highlights the value that collaborative citizen science projects could have in support of marine science, management and conservation efforts worldwide.
... Whilst a number of positive outcomes were reported, project limitations were also observed in several studies. The most common issue related to inconsistent data, particularly with regards to data collection bias and different sampling efforts (see Ward-Paige et al., 2018). For example, Andrzejaczek et al. (2016) found variations in whale shark data due to differing year-to-year sampling efforts, whilst Noviello et al. (2021) observed that most recreational divers will participate during daylight hours only, creating temporal biases and reducing the likelihood of identifying nocturnal species. ...
... The possible extension of project timeframes was underpinned by the idea that tourists could be a cost-effective resource (see Ashley et al., 2022;Cerrano et al., 2017;Mannino et al., 2021;McCoy et al., 2018;McDonough MacKenzie et al., 2019) and as posited by Gouraguine et al. (2019), CS monitoring has the potential to be an important alternative to conventional programs, especially in areas where funding is unavailable. It was additionally suggested that successful CS project models that involve tourists could now be replicated in other geographies (see Hudgins et al., 2017;Lorenzo et al., 2011) or slightly modified to explore other environmental challenges, particularly the monitoring of similar threatened or endangered species under a changing climate (see Baumbach et al., 2019;Roberts et al., 2022;Ward-Paige et al., 2018;Tolimieri et al., 2017). ...
... Such a project shows how CS and tourist experience can be combined', and that by including such experiences, tourists may leave with a greater awareness of the challenges faced by polar environments and adopt modified behaviours that support their protection upon their return home . These points indicate the potential of the mutually beneficial role that tourist-driven or -supported CS projects could offer scientists and tourism industry stakeholders (Hesley et al., 2017;Ward-Paige et al., 2018). Indeed, whilst scientists or researchers are primarily motivated to protect natural environments for ecological reasons, tourism industry stakeholders are predominantly concerned with the economic value that natural assets offer and the importance of providing high quality tourist experiences in natural environments. ...
There has been a proliferation of studies that have examined the impacts of public participation in Citizen Science (CS) that respond to environmental challenges and the recovery of ecosystems, endangered species or other important natural assets. However, comparatively few studies have explored how tourists may play a critical role in the generation of CS data and thus it has been posited that many potential opportunities remain unrealised. By systematically analysing studies that have utilised tourist-generated data in response to environmental challenges or issues, this paper seeks to establish an appraisal of what has so far been established in extant literature and to identify future possibilities for the inclusion of tourists in CS. Via our literature search, a total of 45 peer-reviewed studies were identified via the PRISMA search protocol. Our findings reveal numerous positive outcomes were reported that highlight the significant, yet largely untapped, potential of tourist integration in CS, with studies also offering a range of recommendations on how tourists could be included more effectively to expand scientific knowledge. Notwithstanding, several limitations were observed, and it is critical that future CS projects that utilise tourists for data collection purposes are acutely aware of the challenges they may encounter.
... Additionally, marine tourism operators, guides, and tourists are proving to be highly motivated to document their ocean (e.g. species and anthropogenic threats) and leverage the economic value of their industry towards improved science, management, and conservation for the ocean and their livelihoods (Brunnschweiler et al. 2014;Ward-Paige et al. 2018). ...
Globally, more than 121 million people enjoy nature-based marine tourism, making it one of the largest marine industries. Ocean degradation threatens this industry and management has not kept pace to ensure long-term sustainability. In response, some individuals within the industry are taking it upon themselves to monitor the ocean and provide the data needed to assist management decisions. Fiji is one such place. Aims Between 2012 and 2016, 39 Fijian dive operators, in collaboration with eOceans, conducted the Great Fiji Shark Count to document sharks on their dives. Methods Using 146 304 shark observations from 30668 dives, we document spatial and temporal patterns of 11 shark species at 592 sites. Key results Sharks were observed on 13 846 dives (45% of recorded dives) at 441 (74%) sites. Generally, our results matched those from other more limited surveys, including from baited remote underwater video systems. We found high variability in shark presence, species richness, and relative abundance through space and time. One trend was surprising: the most common species, Whitetip Reef Shark, decreased over the study period at eastern sites and increased at western sites; the cause is currently unknown. Conclusions Our results can guide management and conservation needs, future scientific questions, and provide a baseline for future assessments. Implications This study demonstrates the value of longitudinal observation data that includes absences for describing marine fauna, and confirms the capacity of stakeholders to document the ocean. It also points the direction for broadscale participatory science methodologies to track the ocean. </sec
... The academic literature largely focuses on North America and Europe (Chandler et al. 2016), where more established organizations promote citizen science both nationally and trans-nationally (e.g., the Citizen Science Association and the European Citizen Science Association). While studies from Asia are less prevalent in the English-language academic literature, citizen science is not a new concept in this region, with projects ranging from examining trees blooming in Japan (Kobori et al. 2016), to monitoring forest resources in Cambodia (Brofeldt et al. 2018), and to documenting shark populations in Thailand (Ward-Paige et al. 2018). Some projects originated due to their cultural significance and are now being re-examined in a scientific context (Kobori et al. 2016). ...
Citizen science projects are designed to encourage involvement of the public with science. Understanding demographics of participants and factors that motivate or create barriers to participation are central in ensuring citizen science is effective. Citizen science is not new to Asia, but its implementation is underrepresented in the published literature of that geographic area, with the current focus largely on Western countries. Here, we consider the experience of citizen scientists participating in the Hong Kong Jellyfish Project. Survey responses (N = 87) indicate demographics similar to other citizen science programs, with participant gender reflective of the general population, and participants typically in full-time employment and highly educated. The main motivating factors for participation were: the project had meaningful goals, and participants wanted to contribute to science and to learn more about jellyfish. The main barriers to participation were: not being aware that absence of jellyfish was a valid observation, lack of knowledge, and lack of time. Notably, survey responses indicate inclusive bilingual communication made the project more appealing to respondents, improved participation, and increased motivation. Interestingly, these results indicate demographic traits, motivating factors, and barriers to participation of citizen scientists in Hong Kong are similar to elsewhere, and further research should be conducted to see if the same patterns persist across other cultural contexts. Where recognized, these motivational factors and barriers can inform the design of citizen science projects to more effectively attract and engage participants.
... Additionally, marine tourism operators, guides, and tourists are proving to be highly motivated to document their ocean (e.g. species and anthropogenic threats) and leverage the economic value of their industry towards improved science, management, and conservation for the ocean and their livelihoods (Brunnschweiler et al. 2014;Ward-Paige et al. 2018). ...
Context
Globally, more than 121 million people enjoy nature-based marine tourism, making it one of the largest marine industries. Ocean degradation threatens this industry and management has not kept pace to ensure long-term sustainability. In response, some individuals within the industry are taking it upon themselves to monitor the ocean and provide the data needed to assist management decisions. Fiji is one such place.
Aims
Between 2012 and 2016, 39 Fijian dive operators, in collaboration with eOceans, conducted the Great Fiji Shark Count to document sharks on their dives.
Methods
Using 146 304 shark observations from 30 668 dives, we document spatial and temporal patterns of 11 shark species at 592 sites.
Key results
Sharks were observed on 13 846 dives (45% of recorded dives) at 441 (74%) sites. Generally, our results matched those from other more limited surveys, including from baited remote underwater video systems. We found high variability in shark presence, species richness, and relative abundance through space and time. One trend was surprising: the most common species, Whitetip Reef Shark, decreased over the study period at eastern sites and increased at western sites; the cause is currently unknown.
Conclusions
Our results can guide management and conservation needs, future scientific questions, and provide a baseline for future assessments.
Implications
This study demonstrates the value of longitudinal observation data that includes absences for describing marine fauna, and confirms the capacity of stakeholders to document the ocean. It also points the direction for broadscale participatory science methodologies to track the ocean.
... Additionally, community knowledge and acceptance of science are known to be important features in decision making [12][13][14], but are limited because discoveries are largely inaccessible (e.g., paywalls, technical language, lack of involvement). Therefore, integrating participatory and community science and management (e.g., citizen science) within a local context would have added benefits of improved literacy and acceptance [15][16][17], downstream conservation impacts [14,18], and enabling early warnings and actions that can lead to community resilience to change [19][20][21][22][23][24]. ...
The human response to the COVID-19 pandemic set in motion an unprecedented shift in human activity with unknown long-term effects. The impacts in marine systems are expected to be highly dynamic at local and global scales. However, in comparison to terrestrial ecosystems, we are not well-prepared to document these changes in marine and coastal environments. The problems are two-fold: 1) manual and siloed data collection and processing, and 2) reliance on marine professionals for observation and analysis. These problems are relevant beyond the pandemic and are a barrier to understanding rapidly evolving blue economies, the impacts of climate change, and the many other changes our modern-day oceans are undergoing. The “Our Ocean in COVID-19” project, which aims to track human-ocean interactions throughout the pandemic, uses the new eOceans platform (eOceans.app) to overcome these barriers. Working at local scales, a global network of ocean scientists and citizen scientists are collaborating to monitor the ocean in near real-time. The purpose of this paper is to bring this project to the attention of the marine conservation community, researchers, and the public wanting to track changes in their area. As our team continues to grow, this project will provide important baselines and temporal patterns for ocean conservation, policy, and innovation as society transitions towards a new normal. It may also provide a proof-of-concept for real-time, collaborative ocean monitoring that breaks down silos between academia, government, and at-sea stakeholders to create a stronger and more democratic blue economy with communities more resilient to ocean and global change.
... Additionally, community knowledge and acceptance of science are known to be important features in decision making [12][13][14], but are limited because discoveries are largely inaccessible (e.g., paywalls, technical language, lack of involvement). Therefore, integrating participatory and community science and management (e.g., citizen science) within a local context would have added benefits of improved literacy and acceptance [15][16][17], downstream conservation impacts [14,18], and enabling early warnings and actions that can lead to community resilience to change [19][20][21][22][23][24]. ...
The human response to the COVID-19 pandemic set in motion an unprecedented shift in human activity with unknown long-term effects. The impacts in marine systems are expected to be highly dynamic at local and global scales. However, in comparison to terrestrial ecosystems, we are not well-prepared to document these changes in marine and coastal environments. The problems are twofold: 1) manual and siloed data collection and processing, and 2) reliance on marine professionals for observation and analysis. These problems are relevant beyond the pandemic and are a barrier to understanding rapidly evolving blue economies, the impacts of climate change, and the many other changes our modern-day oceans are undergoing. The "Our Ocean in COVID-19" project, which aims to track human-ocean interactions throughout the pandemic, uses the new eOceans platform (eOceans.co) to overcome these barriers. Working at local scales, a global network of ocean scientists and citizen scientists are collaborating to monitor the ocean in near real-time. The purpose of this paper is to bring this project to the attention of the marine conservation community and researchers wanting to track changes in their area. As our team continues to grow, this project will provide important baselines and temporal patterns for ocean conservation, policy, and innovation as society transitions towards a new normal. It may also provide a proof-of-concept for real-time, collaborative ocean monitoring that breaks down silos between academia, government, and at-sea stakeholders to create a stronger and more democratic blue economy with communities more resilient to ocean and global change.
... Economic incentives derived from shark diving have justified and supported the establishment of shark sanctuaries and marine protected areas (MPAs) (Vianna et al., 2018) as well as community-based management of these areas (Brunnschweiler, 2010) and the creation of alternative livelihoods for people who would otherwise fish sharks for an income (Eriksson, Johansson, & Blicharska, 2019). The shark diving experience can have positive effects on the knowledge, attitude, and behavior of tourists towards sharks, increasing ecocentric views and agency in shark conservation through participatory research, funding, and advocacy (Apps, Dimmock, & Huveneers, 2018;Mieras, Harvey-Clark, Bear, Hodgin, & Hodgin, 2017;Sutcliffe & Barnes, 2018;Ward-Paige, Westell, & Sing, 2018;Whatmough, Van Putten, & Chin, 2011). ...
Shark diving tourism is an activity that can contribute significantly to coastal economies, while also offering tremendous help to shark conservation efforts. Nevertheless, like any form of wildlife-based tourism, shark diving poses management challenges revolving around ethical and safety considerations. Safety in shark diving normally focuses on operational self-efficacy and adherence to shark diving codes of conduct to prevent incidents such as shark bites and to minimize ecological harm. However, safety issues in shark diving can arise from personal choices to exceed standard certification limits. Any detrimental results are capable of casting doubts on the sustainability of shark diving, thus jeopardizing its future as well as shark conservation. This study addressed compliance with shark diving codes of conduct and standard diving safety by examining the knowledge, attitude, and behavior of people who engage in free scuba diving with predatory sharks. The research made use of mixed methods of data collection, including interviews with shark divers at two popular shark diving destinations in Southeast Africa (n = 86) and an online questionnaire survey among shark divers (n = 89). The results showed that divers had positive attitudes towards sharks and shark diving. However, a notable proportion declared that they had exceeded certification limits and broken codes of conduct during shark diving. In particular, diving experience and being a professional diver were correlated significantly with poor safety attitudes and behavior. The results highlight the need to create an understanding among scuba divers of the connection between shark diving safety and conservation, including the negative implications of safety breaches, whether big or small, for the future of shark diving tourism and of sharks.
... Furthermore, transect protocols are incompatible with most dives conducted by a diving center. To overcome this concern, some projects have developed simplified data recording protocols (Bonney et al., 2009;Edgar and Stuart-Smith, 2009;Freitag et al., 2016;Vermeiren et al., 2016), for example, those based on opportunistic observations (Huveneers et al., 2009;Couturier et al., 2015;Ward-Paige et al., 2018). ...
Divers have widely participated in citizen science (CS) projects and are one of the main groups of marine citizen scientists. However, there is little knowledge about profiles of, and incentives for potential divers to join CS projects. To date, most studies have focused on the SCUBA diving industry; nevertheless, there is a diversity of divers, not all using SCUBA, who engage in different activities during their dives. Differences in diver profiles could affect their willingness and ability to contribute to CS. In this study, we compare the diving profile, interests, preferences and motivations to participate in CS of five diver types (artisanal fishermen, recreational divers, instructors, scientific divers, and others). All divers have strong interests in participating in CS projects, with no major differences among diver types. In general, they are interested in a wide variety of themes related to CS but they prefer simple sampling protocols. Divers are motivated to participate in CS to learn about the sea and contribute to science. Some important differences among diver types were found, with artisanal fishermen having significantly more dive experience than other diver types, but less free time during their dives and limited access to some communication channels and technologies. These characteristics make them ideal partners to contribute their local ecological knowledge (LEK) to local CS projects. In contrast, recreational divers have the least experience but most free time during their dives and good access to cameras and communications channels, making them suitable partners for large-scale CS projects that do not require a high level of species knowledge. Instructors and scientific divers are well-placed to coordinate and supervise CS activities. The results confirm that divers are not all alike and specific considerations have to be taken into account to improve the contribution of each diver type to CS. The findings provide essential information for the design of different types of CS projects. By considering the relevant incentives and opportunities for diverse diver groups, marine CS projects will make efficient gains in volunteer recruitment, retention, and collaborative generation of knowledge about the marine environment.
... Furthermore, transect protocols are incompatible with most dives conducted by a diving center. To overcome this concern, some projects have developed simplified data recording protocols (Bonney et al., 2009;Edgar and Stuart-Smith, 2009;Freitag et al., 2016;Vermeiren et al., 2016), for example, those based on opportunistic observations (Huveneers et al., 2009;Couturier et al., 2015;Ward-Paige et al., 2018). ...
Context: Globally, more than 121 million people enjoy nature-based marine tourism, making it one of the largest marine industries. Ocean degradation threatens this industry and management has not kept pace to ensure long-term sustainability. In response, some individuals within the industry are taking it upon themselves to monitor the ocean and provide the data needed to assist management decisions. Fiji is one such place.
Aims: Between 2012 and 2016, 39 Fijian dive operators, in collaboration with eOceans, conducted the Great Fiji Shark Count (GFSC) to document sharks on their dives.
Methods: Using 146,304 shark observations from 30,668 dives, we document spatial and temporal patterns of eleven shark species at 592 sites.
Key results: Sharks were observed on 13,846 dives (45% of recorded dives) at 441 (74%) sites. Generally, our results matched those from other, more limited surveys, including from BRUVs. We found high variability in shark presence, species richness, and relative abundance through space and time. One trend was surprising: the most common species, Whitetip Reef Shark, decreased over the study period at eastern sites and increased at western sites - the cause is currently unknown.
Conclusions: Our results can guide management and conservation needs, future scientific questions, and provide a baseline for future assessments.
Implications: This study demonstrates the value of longitudinal observation data that includes absences for describing marine fauna, and confirms the capacity of stakeholders to document the ocean. It also points the direction for broadscale participatory science methodologies to track the ocean.
Coastal monitoring and management can be enhanced by citizen science (CS), especially because Information and Communications Technology (ICT) enables remote public engagement in CS. To date, this type of engagement would benefit from a thorough investigation to highlight its supportive role to coastal CS, identify its unique challenges, and propose solutions and research avenues to sustain its development. A systematic scoping review and qualitative analysis of scientific papers (N = 53) described the state of the art in remote public engagement in coastal CS. The analysis revealed unique advantages of remote engagement in coastal CS, including flexibility, social inclusivity, and organised communication management. Challenges, mainly associated with technology, could be solved by simplifying interfaces to streamline communication and participation in CS. The review identified research gaps and confirmed the potentially positive contribution of remote engagement in coastal CS, which could enhance coastal monitoring, management, public participation, and stewardship.
The oceans are in a state of rapid change - both negatively, due climate destabilization and misuse, and positively, due to strengthening of policies for sustainable use combined with momentum to grow the blue economy. Globally, more than 121 million people enjoy nature-based marine tourism - e.g., recreational fishing, diving, whale watching - making it one of the largest marine sectors. This industry is increasingly threatened by ocean degradation and management has not kept pace to ensure long-term sustainability. In response, individuals within the industry are taking it upon themselves to monitor the oceans and provide the data needed to assist management decisions. Fiji is one such place where the dive tourism industry is motivated to monitor the oceans (e.g., track sharks). In 2012, 39 dive operators in collaboration with eOceans commenced the Great Fiji Shark Count (GFSC) to document sharks (and other species) on 592 dive sites. Here, using 146,304 shark observations from 30,668 dives we document spatial patterns of 11 shark species. High variability demonstrates the value of longitudinal data that include absences for describing mobile megafauna and the capacity of stakeholders to document the oceans. Our results may be used to guide future scientific questions, provide a baseline for future assessments, or to evaluate conservation needs. It also shows the value of scientists collaborating with stakeholders to address questions that are most important to the local community so that they have the information needed to make science-based decisions.
The Mediterranean Sea is a hotspot for shark conservation. A decline in large pelagic shark populations has been observed in this vast region over the last 50 years and a lack of data on the local population status of various species has been pointed out. Throughout history, the relation between people and sharks has been revolving around a mixture of mystery, fear, and attraction. Recently, however, a remunerative ecotourism industry has been growing in areas of shark aggregation globally. This growth has been accompanied by the establishment of a citizen science (CS) movement aimed to engage and recruit ecotourists in data collection for shark research. Several CS projects have generated interesting results in terms of scientific findings and public engagement. In the Mediterranean Sea, shark aggregations are not as relevant to support locally-focused CS actions on shark diving sites as in other parts of the world. However, a series of other initiatives are taking place and CS could offer an excellent opportunity for shark conservation in the Mediterranean Sea. The dramatic decline of shark populations shown in the region calls for alternative ways to collect data on species distributions and abundance. Obtaining such data to set proper conservation and management plans for sharks in the Mediterranean Sea will be possible if existing CS initiatives collaborate and coordinate, and CS is widely acknowledged and deployed as a valuable tool for public education, engagement, and scientific discovery. After providing an overview of multiple facets of the relationship between humans and sharks, we focus on the possibility of exploiting new technologies and attitudes toward sharks among some groups of ocean users to boost participatory research. CS is a great opportunity for shark science, especially for areas such as the Mediterranean Sea and for large pelagic sharks whose populations are highly impacted.
The rapid expansion of human activities threatens ocean-wide biodiversity. Numerous marine animal populations have declined, yet it remains unclear whether these trends are symptomatic of a chronic accumulation of global marine extinction risk. We present the first systematic analysis of threat for a globally distributed lineage of 1,041 chondrichthyan fishes-sharks, rays, and chimaeras. We estimate that one-quarter are threatened according to IUCN Red List criteria due to overfishing (targeted and incidental). Large-bodied, shallow-water species are at greatest risk and five out of the seven most threatened families are rays. Overall chondrichthyan extinction risk is substantially higher than for most other vertebrates, and only one-third of species are considered safe. Population depletion has occurred throughout the world's ice-free waters, but is particularly prevalent in the Indo-Pacific Biodiversity Triangle and Mediterranean Sea. Improved management of fisheries and trade is urgently needed to avoid extinctions and promote population recovery.
Subtropical reefs provide an important habitat for flora and fauna, and proper monitoring is required for conservation. Monitoring these exposed and submerged reefs is challenging and available resources are limited. Citizen science is increasing in momentum, as an applied research tool and in the variety of monitoring approaches adopted. This paper aims to demonstrate an ecological assessment and mapping approach that incorporates both top-down (volunteer marine scientists) and bottom-up (divers/community) engagement aspects of citizen science, applied at a subtropical reef at Point Lookout, Southeast Queensland, Australia. Marine scientists trained fifty citizen scientists in survey techniques that included mapping of habitat features, recording of substrate, fish and invertebrate composition, and quantifying impacts (e.g., occurrence of substrate damage, presence of litter). In 2014 these volunteers conducted four seasonal surveys along semi-permanent transects, at five sites, across three reefs. The project presented is a model on how citizen science can be conducted in a marine environment through collaboration of volunteer researchers, non-researchers and local marine authorities. Significant differences in coral and algal cover were observed among the three sites, while fluctuations in algal cover were also observed seasonally. Differences in fish assemblages were apparent among sites and seasons, with subtropical fish groups observed more commonly in colder seasons. The least physical damage occurred in the most exposed sites (Flat Rock) within the highly protected marine park zones. The broad range of data collected through this top-down/bottom-up approach to citizen science exemplifies the projects’ value and application for identifying ecosystem trends or patterns. The results of the project support natural resource and marine park management, providing a valuable contribution to existing scientific knowledge and the conservation of local reefs.
The goal of this report is to help government agencies and other organizations involved in natural resource management, environmental protection, and policymaking related to both to make informed decisions about investing in citizen science. In this report, we explore the current use of citizen science in natural resource and environmental science and decisionmaking in the United States and describe the investments organizations might make to benefit from citizen science.
We find that:
• Many people are interested in participating in citizen science.
• Citizen science already contributes to natural resource and environmental science, natural resource
management, and environmental protection and policymaking.
• Citizen science is a rigorous process of scientific discovery, indistinguishable from conventional science
apart from the participation of volunteers, and should be treated as such in its design, implementation,
and evaluation. When properly designed and used, citizen science can help an organization meet its
needs for sound science.
• Citizen science can contribute to natural resource and environmental organizations’ goals for public
input and engagement.
• Many types of projects can benefit from citizen science. When planning to utilize citizen science, organizations
need to match their needs and goals for science and public input and engagement to the
strengths of particular citizen science projects and the ways in which the public can participate.
Depending on the organization’s needs and goals, citizen science can efficiently generate high-quality
data or help solve problems while fostering public input and engagement.
• Organizational leadership is needed to provide realistic expectations for citizen science, including its
limitations as well as its benefits. Leadership is also sometimes needed to lessen administrative hurdles
and to create a safe space for learning from project inefficiencies and failures.
Citizen science requires strategic investments. Beyond project-specific investments, organizations should consider developing or modifying policies and technologies designed to facilitate the field of citizen science as a whole.
The whale shark
Rhincodon typus
is a popular focal species in the marine tourism industry. We analysed 689 encounters with at least 142 individual sharks during 2008–2010 to assess their behaviour in the presence of swimmers at Tofo Beach, Mozambique. Sharks varied in size (estimated 3.0–9.5 m total length) and the majority (74%) were males. The sharks displayed avoidance behaviours during 64.7% of encounters. Encounter duration decreased significantly, from 12 minutes 37 s with undisturbed sharks to 8 minutes 25 s when sharks expressed avoidance behaviours, indicating that interactions with tourists affected the sharks’ short-term behaviour. However, during the 2.5-year study period we found no trend in the mean encounter duration, the overall expression of avoidance behaviour or the likelihood of an individual shark exhibiting avoidance behaviours. Potential effects of tourism may be mitigated by the non-breeding status and transient behaviour of sharks at this aggregation site.
Quantifying shark distribution patterns and species-specific habitat associations in response to geographic and environmental drivers is critical to assessing risk of exposure to fishing, habitat degradation, and the effects of climate change. The present study examined shark distribution patterns, species-habitat associations, and marine reserve use with baited remote underwater video stations (BRUVS) along the entire Great Barrier Reef Marine Park (GBRMP) over a ten year period. Overall, 21 species of sharks from five families and two orders were recorded. Grey reef Carcharhinus amblyrhynchos , silvertip C. albimarginatus , tiger Galeocerdo cuvier , and sliteye Loxodon macrorhinus sharks were the most abundant species (>64% of shark abundances). Multivariate regression trees showed that hard coral cover produced the primary split separating shark assemblages. Four indicator species had consistently higher abundances and contribute
Citizen science is promoted as a simple and cost-effective alternative to traditional approaches for the monitoring of populations of marine megafauna. However, the reliability of datasets collected by these initiatives often remains poorly quantified. We compared datasets of shark counts collected by professional dive guides with acoustic telemetry data from tagged sharks collected at the same coral reef sites over a period of five years. There was a strong correlation between the number of grey reef sharks (Carcharhinus amblyrhynchos) observed by dive guides and the telemetry data at both daily and monthly intervals, suggesting that variation in relative abundance of sharks was detectable in datasets collected by dive guides in a similar manner to data derived from telemetry at these time scales. There was no correlation between the number or mean depth of sharks recorded by telemetry and the presence of tourist divers, suggesting that the behaviour of sharks was not affected by the presence of divers during our study. Data recorded by dive guides showed that current strength and temperature were important drivers of the relative abundance of sharks at monitored sites. Our study validates the use of datasets of shark abundance collected by professional dive guides in frequently-visited dive sites in Palau, and supports the participation of experienced recreational divers as contributors to long-term monitoring programs of shark populations.
Amid declining shark populations because of overfishing, a burgeoning shark watching industry, already well established in some locations, generates benefits from shark protection. We compile reported economic benefits at shark watching locations and use a meta-analytical approach to estimate benefits at sites without available data. Results suggest that, globally, c. 590,000 shark watchers expend > USD 314 million per year, directly supporting 10,000 jobs. By comparison, the landed value of global shark fisheries is currently c. USD 630 million and has been in decline for most of the past decade. Based on current observed trends, numbers of shark watchers could more than double within the next 20 years, generating > USD 780 million in tourist expenditures around the world. This supports optimistic projections at new sites, including those in an increasing number of shark sanctuaries established primarily for shark conservation and enacted in recognition of the ecological and economic importance of living sharks.
Arguments for conservation of sharks based on their role in the maintenance of healthy marine ecosystems have failed to halt the worldwide decline in populations. Instead, the value of sharks as a fishery commodity has severely reduced the abundance of these animals. Conservation may be assisted by the development of an alternative approach that emphasizes the economic value of sharks as a non-harvested resource. Our study quantifies the value of a tourism industry based on shark diving. Using data collected from surveys, as well as government statistics, we show that shark diving is a major contributor to the economy of Palau, generating US1.2 million in salaries to the local community, and generated US10 800, a fraction of the worth of these animals as a non-consumptive resource. Fishers earn more selling fish for consumption by shark divers than they would gain by catching sharks. Shark diving provides an attractive economic alternative to shark fishing, with distribution of revenues benefiting several sectors of the economy, stimulating the development and generating high revenues to the government, while ensuring the ecological sustainability of shark populations.
Long-term fisheries independent gill net surveys conducted in Texas estuaries from 1975 to 2006 were used to develop spatially explicit estuarine habitat use models for 3 coastal shark species: bull shark Carcharhinus leucas, blacktip shark C. limbatus, and bonnethead shark Sphyrna tiburo. Relationships between environmental predictors and shark distribution were investigated using boosted regression trees (BRT). Bull shark was the most abundant species (n = 5800), followed by blacktip (n = 2094), and bonnethead sharks (n = 1793). Environmental conditions influenced distribution patterns of all species and relationships were nonlinear, multivariate, and interactive. Results showed very good model performance and suggested shark distribution is most closely linked to salinity, temperature, and proximity to tidal inlets. By interpolating the BRT models, maps of the probability of capture were produced using ordinary kriging. Results showed that the central region along the Texas coast contains the most important estuarine shark habitat. This area was characterized by warm temperatures, moderate salinities, and abundant tidal inlets. Bull sharks also extended into low salinity estuaries, while blacktip and bonnethead sharks were restricted to areas near tidal passes with moderate salinities. Juvenile sharks were frequently captured, suggesting the Texas coast may constitute important nursery areas for all 3 species. The development of these spatially explicit models allows for prioritization and conservation of areas in a region that has great potential for human disturbance and climate change impacts. These results provide new insight into the habitat requirements of coastal sharks in the northwestern Gulf of Mexico and practical information for managing this resource.
A comparison between the northwestern Hawaiian islands (NWHI), a large, remote, and lightly fished area, and the main Hawaiian islands (MHI), an urbanized, heavily fished area, revealed dramatic differences in the numerical density, size, and biomass of the shallow reef fish assemblages. Grand mean fish standing stock in the NWHI was more than 260% greater than in the MHI. The most striking difference was the abundance and size of large apex predators (primarily sharks and jacks) in the NWHI compared to the MHI. More than 54% of the total fish biomass in the NWHI consisted of apex predators, whereas this trophic level accounted for less than 3% of the fish biomass in the MHI. In contrast, fish biomass in the MHI was dominated by herbivores (55%) and small-bodied lower-level carnivores (42%). Most of the dominant species by weight in the NWHI were either rare or absent in the MHI and the target species that were present, regardless of trophic level, were nearly always larger in the NWHI, These differences represent both near-extirpation of apex predators and heavy exploitation of lower trophic levels in the MHI compared to the largely unfished NWHI. The reefs in the NWHI are among the few remaining large-scale, intact, predator-dominated reef ecosystems left in the world and offer an opportunity to understand how unaltered ecosystems are structured, how they function, and how they can most effectively be preserved. The differences in fish assemblage structure in this study are evidence of the high level of exploitation in the MHI and the pressing need for ecosystem-level management of reef systems in the MHI as well as the NWHI.
New technologies are rapidly changing the way we collect, archive, analyze, and share scientific data. For example, over the next several years it is estimated that more than one billion autonomous sensors will be deployed over large spatial and temporal scales, and will gather vast quantities of data. Networks of human observers play a major role in gathering scientific data, and whether in astronomy, meteorology, or observations of nature, they continue to contribute significantly. In this paper we present an innovative use of the Internet and information technologies that better enhances the opportunity for citizens to contribute their observations to science and the conservation of bird populations. eBird is building a web-enabled community of bird watchers who collect, manage, and store their observations in a globally accessible unified database. Through its development as a tool that addresses the needs of the birding community, eBird sustains and grows participation. Birders, scientists, and conservationists are using eBird data worldwide to better understand avian biological patterns and the environmental and anthropogenic factors that influence them. Developing and shaping this network over time, eBird has created a near real-time avian data resource producing millions of observations per year.
Essential to any model, conservation or management plan are measures of the distribution and abundance of a species. Countless methods for estimating these parameters exist, making it essential to assess the limitations and biases associated with a particular sampling protocol. Here, we compare between 2 methods commonly used to survey nearshore fish assemblages. Although most commonly employed, underwater visual census (UVC) may yield biased estimates of abundance depending on the strength of a fish's behavioural response (i.e. avoidance, attraction) to the presence of divers. Baited remote underwater video (BRUV) techniques have shown promise in overcoming some of the limitations of UVC, but are unable to provide an absolute measure of density in turbulent environments. We compare the abilities of these 2 methods to survey the nearshore rocky reef ichthyofauna of Southeast Australia. We found that relative to BRUV, UVC recorded more individuals (in terms of all species, herbivores, cryptic species, and most territorial species), higher richness at both the species and family level, and higher biodiversity as measured using the Shannon Index. These findings remain even when the data were adjusted for differences in sampling effort. In contrast, BRUV recorded proportionally more mobile predators, and a more taxonomically distinct population, though only when taxonomic evenness was not taken into account. Twenty species were unique to UVC and 17 species unique to BRUV. Considering this, studies aimed at cataloguing diversity should apply multiple methods, However, when logistical or financial constraints limit biodiversity studies to only 1 method, UVC will likely provide a more complete estimate of temperate reef fish diversity than BRUV.
The Caribbean reef shark (Carcharhinus pere-zi), an abundant coral-reef-associated apex predator, is one of the most economically and ecologically important, yet least studied species of large shark in the greater Caribbean region. The relative abundance and population structure of C. perezi off Cape Eleuthera, The Bahamas, was surveyed by standardised longline surveys from May 2008 to October 2011, which resulted in the capture of 331 sharks. Abundance peaked in the summer and was lowest during the winter. Females were 1.6 times more abundant than males and the assemblage was dominated by immature female sharks (45.5 %). The abundance of mature male and female sharks peaked a month apart in June and August, respectively. All 331 sharks were tagged and released with 15.4 % being recaptured after periods at liberty between 5 and 1,159 days (Mean = 333.4 ± 42.7 SE). The mean distance between tagging and recapture was 1.77 km for recaptures in excess of 6 months, indicating seasonally stratified philopatry in this species. C. perezi inhabiting Bahamian waters have developed complex habitat use patterns that are both spatiotemporally and demographically segregated, most probably in response to the large and diverse habitat mosaic available on the Bahamas Banks compared to contemporary study sites. This study represents an important step in understanding the spatiotemporal population structure of C. perezi and illustrates the potential for studies examining behavioural plasticity in response to environmental variation and anthropogenic disturbance.
Citizen science enlists the public in collecting large quantities of data across an array of habitats and locations over long spans of time. Citizen science projects have been remarkably successful in advancing scientific knowledge, and contributions from citizen scientists now provide a vast quantity of data about species occurrence and distribution around the world. Most citizen science projects also strive to help participants learn about the organisms they are observing and to experience the process by which scientific investigations are conducted. Developing and implementing public data-collection projects that yield both scientific and educational outcomes requires significant effort. This article describes the model for building and operating citizen science projects that has evolved at the Cornell Lab of Ornithology over the past two decades. We hope that our model will inform the fields of biodiversity monitoring, biological research, and science education while providing a window into the culture of citizen science.
In this paper, we analyse long-term whale shark Rhincodon
typus sightings collected by ecotourist operators and evaluate the validity of conclusions drawn from the data for scientific and conservation purposes. To date information about the basic ecology and movements of whale sharks is sparse, and only recently has the species received global conservation attention. A dive company in Phuket, Thailand, documented whale shark sightings in the Andaman Sea for 10 years along 300 km of coastline. Whale shark sightings, corrected for effort, dropped by 96% between 1998 and 2001. Combining the seasons from 1992 to 1998, the number of whale shark sightings increased significantly from October to May. The sizes of sharks observed suggest that the majority were juveniles. We discuss the limitations of using ecotourist operators as non-specialist volunteers for data collection but conclude that their use can be beneficial for long-term, broad geographic studies such as this.
Citizen science, the involvement of volunteers in research, has increased the scale of ecological field studies with continent-wide, centralized monitoring efforts and, more rarely, tapping of volunteers to conduct large, coordinated, field experiments. The unique benefit for the field of ecology lies in understanding processes occurring at broad geographic scales and on private lands, which are impossible to sample extensively with traditional field research models. Citizen science produces large, longitudinal data sets, whose potential for error and bias is poorly understood. Because it does not usually aim to uncover mechanisms underlying ecological patterns, citizen science is best viewed as complementary to more localized, hypothesis-driven research. In the process of addressing the impacts of current, global “experiments” altering habitat and climate, large-scale citizen science has led to new, quantitative approaches to emerging questions about the distribution and abundance of organisms across space and time.
Animal movements, residence times, and subsequently foraging strategies, should vary with habitat quality. We used acoustic and satellite telemetry, as well as stable isotopes, to look at movement patterns, macro-scale habitat use, and trophic ecology of blacktip reef sharks, Carcharhinus melanopterus, between two lagoons (eastern and western) at Palmyra Atoll, a US National Wildlife Refuge in the central Pacific. Sharks in the Palmyra lagoons have relatively small home ranges and appear to obtain most of their energy from the lagoon ecosystem. Sharks showed low levels of migration between lagoons over periods of several years, and individuals in the larger western lagoon tended to have longer residence times than those in the smaller eastern lagoon. Furthermore, for sharks in the western lagoon, there was no relationship between total length (TL) and δ15N, 13C relative isotope concentrations, or a Body Condition index (BC). For sharks in the eastern lagoon, TL was positively related to δ15N and negatively related to δ13C and BC. These results suggest that there are low levels of mixing of sharks between lagoons, and these are leading to differences in trophic ecology and potentially foraging success. Although the causative factors behind these differences are unknown, shark home range location can potentially lead to variation in trophic ecology, even over small spatial scales.
Around the world, researchers are using the observations and experiences of citizens to describe patterns in animal populations. This data is often collected via ongoing sampling or by synthesizing past experiences. Since elasmobranchs are relatively rare, obtaining data for broad-scale trend analysis requires high sampling effort. Elasmobranchs are also relatively large and conspicuous and therefore it may be possible to enlist recreational divers to collect data on their occurrence and relative abundance from daily dive activities. For this, however, a good understanding of the value of data collected by recreational divers is essential.
Here, we explore the value of recreational divers for censusing elasmobranchs using a diverse set of data sources. First, we use a simulation experiment to explore detection rates of the roving diver technique, used by recreational divers, across a range of fish densities and speeds. Next, using a field survey, we show that inexperienced recreational divers detect and count elasmobranchs as well as experienced recreational divers. Finally, we use semi-structured interviews of recreational dive instructors to demonstrate the value of their recollections in terms of effort and their descriptions of spatial and temporal distributions of sharks in Thailand.
Overall, this study provides initial ground-work for using recreational divers for monitoring elasmobranch populations. If used appropriately, citizen-collected data may provide additional information that can be used to complement more standardized surveys and to describe population trends across a range of spatial and temporal scales. Due to the non-extractive nature of this data, recreational divers may also provide important insight into the success of conservation initiatives, such as shark sanctuaries and no-take zones.
Incidental hooking of Carcharias taurus is a threat to their populations’ recovery on the east coast of Australia. Photo-identification techniques were used to investigate the frequency of hooking at 25 aggregation sites along the east coast of Australia between 2006 and 2008. Of the 673 sharks identified, 113 sharks were identified with signs of 119 incidences of hooking. For sharks with both their left and right flank photographed during a single survey day, up to 29% of females and 52% of males were identified with retained fishing gear or an attributed jaw injury. The largest number of sharks identified (222) were from a year-round aggregation of immature and mature sharks at Fish Rock, New South Wales, Australia. Forty-eight per cent of all sharks identified with retained fishing gear were first identified at this site. Fish Rock, a designated critical habitat for C. taurus, allows most forms of line fishing except fishing with bait or wire trace while anchored or moored. As interactions with fishing gear can result in debilitating disease, morbidity and death, the high incidence of hooked individual C. taurus is considered a key threatening process that is likely to reduce this shark population’s ability to recover.
Background:
Increasingly, underwater visual censuses (UVC) are used to assess fish populations. Several studies have demonstrated the effectiveness of protected areas for increasing fish abundance or provided insight into the natural abundance and structure of reef fish communities in remote areas. Recently, high apex predator densities (>100,000 individuals x km(-2)) and biomasses (>4 tonnes x ha(-1)) have been reported for some remote islands suggesting the occurrence of inverted trophic biomass pyramids. However, few studies have critically evaluated the methods used for sampling conspicuous and highly mobile fish such as sharks. Ideally, UVC are done instantaneously, however, researchers often count animals that enter the survey area after the survey has started, thus performing non-instantaneous UVC.
Methodology/principal findings:
We developed a simulation model to evaluate counts obtained by divers deploying non-instantaneous belt-transect and stationary-point-count techniques. We assessed how fish speed and survey procedure (visibility, diver speed, survey time and dimensions) affect observed fish counts. Results indicate that the bias caused by fish speed alone is huge, while survey procedures had varying effects. Because the fastest fishes tend to be the largest, the bias would have significant implications on their biomass contribution. Therefore, caution is needed when describing abundance, biomass, and community structure based on non-instantaneous UVC, especially for highly mobile species such as sharks.
Conclusions/significance:
Based on our results, we urge that published literature state explicitly whether instantaneous counts were made and that survey procedures be accounted for when non-instantaneous counts are used. Using published density and biomass values of communities that include sharks we explore the effect of this bias and suggest that further investigation may be needed to determine pristine shark abundances and the existence of inverted biomass pyramids. Because such studies are used to make important management and conservation decisions, incorrect estimates of animal abundance and biomass have serious and significant implications.
Captive and wild Carcharias taurus were used to assess whether spots present on their flanks were suitable as natural tags for individual shark recognition. Photographic images of seven captive sharks taken at monthly intervals for 14 months and at 3 years after the start of the study indicated that spot numbers, positions and sizes did not change. Eighty-nine wild sharks were photographically re-captured at least once subsequent to their initial image-capture; fourteen were re-photographed at least 23 months subsequent to their initial image-capture and a single individual after 14 years. Unique physical marks (e.g. partial fin loss) on six wild sharks were used to validate the pattern recognition process by providing unambiguous identification of individuals independently of their spots. Preliminary visual identification data on the eastern Australian C. taurus population show how spatial and temporal information on individual sharks can be collected without recourse to conventional tagging to address key questions about this species’ ecology and population biology.
Overexploitation threatens the future of many large vertebrates. In the ocean, tunas and sea turtles are current conservation
concerns because of this intense pressure. The status of most shark species, in contrast, remains uncertain. Using the largest
data set in the Northwest Atlantic, we show rapid large declines in large coastal and oceanic shark populations. Scalloped
hammerhead, white, and thresher sharks are each estimated to have declined by over 75% in the past 15 years. Closed-area models
highlight priority areas for shark conservation, and the need to consider effort reallocation and site selection if marine
reserves are to benefit multiple threatened species.
Effective conservation requires rigorous baselines of pristine conditions to assess the impacts of human activities and to evaluate the efficacy of management. Most coral reefs are moderately to severely degraded by local human activities such as fishing and pollution as well as global change, hence it is difficult to separate local from global effects. To this end, we surveyed coral reefs on uninhabited atolls in the northern Line Islands to provide a baseline of reef community structure, and on increasingly populated atolls to document changes associated with human activities. We found that top predators and reef-building organisms dominated unpopulated Kingman and Palmyra, while small planktivorous fishes and fleshy algae dominated the populated atolls of Tabuaeran and Kiritimati. Sharks and other top predators overwhelmed the fish assemblages on Kingman and Palmyra so that the biomass pyramid was inverted (top-heavy). In contrast, the biomass pyramid at Tabuaeran and Kiritimati exhibited the typical bottom-heavy pattern. Reefs without people exhibited less coral disease and greater coral recruitment relative to more inhabited reefs. Thus, protection from overfishing and pollution appears to increase the resilience of reef ecosystems to the effects of global warming.
Evidence for severe declines in large predatory fishes is increasing around the world. Because of its long history of intense fishing, the Mediterranean Sea offers a unique perspective on fish population declines over historical timescales. We used a diverse set of records dating back to the early 19th and mid 20th century to reconstruct long-term population trends of large predatory sharks in the northwestern Mediterranean Sea. We compiled 9 time series of abundance indices from commercial and recreational fishery landings, scientific surveys, and sighting records. Generalized linear models were used to extract instantaneous rates of change from each data set, and a meta-analysis was conducted to compare population trends. Only 5 of the 20 species we considered had sufficient records for analysis. Hammerhead (Sphyrna spp.), blue (Prionace glauca), mackerel (Isurus oxyrinchus and Lamna nasus), and thresher sharks (Alopias vulpinus) declined between 96 and 99.99% relative to their former abundance. According to World Conservation Union (IUCN) criteria, these species would be considered critically endangered. So far, the lack of quantitative population assessments has impeded shark conservation in the Mediterranean Sea. Our study fills this critical information gap, suggesting that current levels of exploitation put large sharks at risk of extinction in the Mediterranean Sea. Possible ecosystem effects of these losses involve a disruption of top-down control and a release of midlevel consumers.
Sharks are increasingly being recognized as important members of coral-reef communities, but their overall conservation status remains uncertain. Nine of the 29 reef-shark species are designated as data deficient in the IUCN Red List, and three-fourths of reef sharks had unknown population trends at the time of their assessment. Fortunately, reef-shark research is on the rise. This new body of research demonstrates reef sharks' high site restriction, fidelity and residency on coral reefs, their broad trophic roles connecting reef communities and their high population genetic structure, all information that should be useful for their management and conservation. Importantly, recent studies on the abundance and population trends of the three classic carcharhinid reef sharks (grey reef shark Carcharhinus amblyrhynchos, blacktip reef shark Carcharhinus melanopterus and whitetip reef shark Triaenodon obesus) may contribute to reassessments identifying them as more vulnerable than currently realized. Because over half of the research effort has focused on only these three reef sharks and the nurse shark Ginglymostoma cirratum in only a few locales, there remain large taxonomic and geographic gaps in reef-shark knowledge. As such, a large portion of reef-shark biodiversity remains uncharacterized despite needs for targeted research identified in their red list assessments. A research agenda for the future should integrate abundance, life history, trophic ecology, genetics, habitat use and movement studies, and expand the breadth of such research to understudied species and localities, in order to better understand the conservation requirements of these species and to motivate effective conservation solutions.
Fishing pressure has increased the extinction risk of many elasmobranch (shark and ray) species. Although many countries have established no-take marine reserves, a paucity of monitoring data means it is still unclear if reserves are effectively protecting these species. We examined data collected by a small group of divers over the past 21 years at one of the world's oldest marine protected areas (MPAs), Cocos Island National Park, Costa Rica. We used mixed effects models to determine trends in relative abundance, or probability of occurrence, of 12 monitored elasmobranch species while accounting for variation among observers and from abiotic factors. Eight of 12 species declined significantly over the past 2 decades. We documented decreases in relative abundance for 6 species, including the iconic scalloped hammerhead shark (Sphyrna lewini) (-45%), whitetip reef shark (Triaenodon obesus) (-77%), mobula ray (Mobula spp.) (-78%), and manta ray (Manta birostris) (-89%) rays, and decreases in the probability of occurrence for 2 other species. Several of these species have small home ranges and should be better protected by an MPA, which underscores the notion that declines of marine megafauna will continue unabated in MPAs unless there is adequate enforcement effort to control fishing. In addition, probability of occurrence at Cocos Island of tiger (Galeocerdo cuvier), Galapagos (Carcharhinus galapagensis), blacktip (Carcharhinus limbatus), and whale (Rhincodon typus) sharks increased significantly. The effectiveness of MPAs cannot be evaluated by examining single species because population responses can vary depending on life history traits and vulnerability to fishing pressure.
© 2015 Society for Conservation Biology.
The overexploitation of sharks has become a global environmental issue in need of a comprehensive and multifaceted management response. Tracking studies are beginning to elucidate how shark movements shape the internal dynamics and structure of populations, which determine the most appropriate scale of these management efforts. Tracked sharks frequently either remain in a restricted geographic area for an extended period of time (residency) or return to a previously resided-in area after making long-distance movements (site fidelity). Genetic studies have shown that some individuals of certain species preferentially return to their exact birthplaces (natal philopatry) or birth regions (regional philopatry) for either parturition or mating, even though they make long-distance movements that would allow them to breed elsewhere. More than 80 peer-reviewed articles, constituting the majority of published shark tracking and population genetic studies, provide evidence of at least one of these behaviors in a combined 31 shark species from six of the eight extant orders. Residency, site fidelity, and philopatry can alone or in combination structure many coastal shark populations on finer geographic scales than expected based on their potential for dispersal. This information should therefore be used to scale and inform assessment, management, and conservation activities intended to restore depleted shark populations. Expected final online publication date for the Annual Review of Marine Science Volume 7 is January 03, 2015. Please see http://www.annualreviews.org/catalog/pubdates.aspx for revised estimates.
The successful management of shark populations requires juvenile recruitment success. Thus, conservation initiatives now strive to include the protection of areas used by pre-adult sharks in order to promote juvenile survivorship. Many shark species use inshore areas for early life stages; however, species often segregate within sites to reduce competition. Using a fisheries-independent gillnet survey from the Northern Gulf of Mexico (2000–2010) we describe distribution patterns and preferred habitat features of the juveniles of six shark species. Our results suggest that multiple shark species concurrently use the area for early life stages and although they overlap, they exhibit distinct habitat preferences characterized by physical variables. Habitat suitability models suggest that temperature, depth, and salinity are the important factors driving juvenile shark occurrence. Within each site, across the sampled range of physical characteristics, blacktip shark (Carcharhinus limbatus) preferred higher temperature (>30 °C) and mid-depth (~5.5 m); bonnethead shark (Sphyrna tiburo) preferred higher temperature (>30 °C) and mid-salinity (30–35 PSU), finetooth shark (Carcharhinus isodon) preferred low salinity (<20 PSU) with mid-depth (~4 m), scalloped hammerhead shark (Sphyrna lewini) preferred high temperature (>30 °C) and salinity (>35 PSU), Atlantic sharpnose shark (Rhizoprionodon terraenovae) preferred high temperature (>30 °C) and deep water (>6 m), and spinner shark (Carcharhinus brevipinna) preferred deep water (>8 m) and high temperature (>30 °C). The other investigated factors, including year, month, latitude, longitude, bottom type, inlet distance, coastline and human coast were not influential for any species. Combining habitat preferences with the sampled environmental characteristics, we predicted habitat suitability throughout the four sites for which physical characteristics were sampled. Habitat suitability surfaces highlight the differences in habitat use between and within sites. This work provides important insight into the habitat ecology of juvenile shark populations, which can be used to better manage these species and protect critical habitat.
Top oceanic predators, especially large predatory sharks (TOPS), appear to be experiencing varying degrees of population declines. Life history data (e.g. diet, reproductive status, age and growth, mortality) are critical for developing effective conservation strategies for TOPS. Presently, lethal sampling remains the most effective and accurate means of gathering these data. To meet such challenges, many scientists have utilized specimens obtained from recreational and commercial fisheries, but have needed to supplement those data with fishery-independent sampling. However, there is growing public and scientific debate as to whether lethal sampling of TOPS is justified for obtaining conservation data. Here we describe the development and use of non-lethal alternatives for collecting data on (1) trophodynamics; (2) maturity state and fecundity; and (3) growth and mortality rates necessary to enact conservation measures for threatened or even data-deficient TOPS.
Despite being a common apex-level predator on coral reefs throughout the tropical Indo-Pacific, surprisingly little is known
about whitetip reef shark (Triaenodon obesus) movements and biology. This study used photo-identification from community-contributed photographs to reveal patterns in
movements, reproductive biology, and fisheries interactions in this species that have not been previously revealed through
more traditional methods. At least 178 individual sharks were identified, and 26 movements were observed. These included movement
distances of up to 26.4 km, movement rates of up to 3.27 km/day (9.8 km in 3 days), and movements that required the transit
of a 140 m deep channel. Other animals showed high philopatry, being re-sighted at the same locality on multiple occasions
(up to 13 sightings for one individual) over periods of up to 7 years. Females showed higher philopatry than males and were
more likely than males to be found at shallow (
This study examined the characteristics of a blacktip reef shark Carcharhinus melanopterus population in turbid coastal habitats through a multi-year fishery-independent sampling and tag-recapture programme. Results revealed a highly structured population comprised almost entirely of juveniles and adult females with individuals between 850 and 1050 mm total length effectively absent. Mature males were also rarely encountered with adult sex ratio highly biased towards females (female:male = 7:1). Mating scars were observed on adult females between December and April, and parturition was observed from December to March. Regression analysis showed that catch rates were significantly higher during the summer wet season between November and May. Recapture data suggested a highly resident population with a recapture rate of 21% and a mean recapture distance of 0·8 km. In addition, 33% of recaptured animals were captured multiple times, indicating long-term residency. Most recaptures were, however, of adults with few juveniles recaptured. Widespread sampling at the study site and in adjacent areas suggested that the population was highly localized to a specific bay. The bimodal and sex-segregated population structure observed here differs from previous reports for this species, and in combination with reproductive observations, suggests population structuring to facilitate reproductive and recruitment success. These data also highlight the potential ecosystem functions performed by coastal habitats in sustaining C. melanopterus populations.
Sharks of the genus Carcharhinus encountered at Chumphon Pinnacle, Gulf of Thailand, have been misidentified by divers as grey reef sharks (Carcharhinus amblyrhynchos). Based on a set of characteristic diagnostic features, the sharks are identified as bull sharks (Carcharhinus leucas).
The quantification of spatial and temporal movement patterns of coral reef sharks is important to understand their role in reef communities and to aid the design of conservation strategies for this predatory guild. We observed 4 species of reef sharks aggregating in an inshore bay in the north of Western Australia for over 2 yr, using acoustic telemetry and visual censuses to examine how they partitioned this site in space and time. We fitted 58 sharks with acoustic transmitters: Carcharhinus melanopterus (36), C. amblyrhynchos (11), Negaprion acutidens (7) and Triaenodon obesus (4). Aggregations consisted primarily of C. melanopterus, although C. amblyrhynchos and N. acutidens were often present. We observed aggregations by visual census in summer (maximum of 44 sharks). Detections were highest during warmer months (Sep to Mar) for all species, although some individuals showed year-round residency. C. melanopterus, C. amblyrhynchos and N. acutidens had strong diel patterns of attendance at the aggregation site. Peak daily detections occurred from 13: 00 to 14: 00 h local time for C. melanopterus and C. amblyrhynchos; juvenile C. melanopterus and N. acutidens peaked at 05:00 and 10:00 h, respectively. There was considerable spatial overlap of core areas of use (50% kernel density estimates) at the northern end of the bay by all species; the southern end was used primarily by C. melanopterus and N. acutidens. Aggregations of C. melanopterus and C. amblyrhynchos consisted mainly of adult females, some of them pregnant. Courtship behaviour in C. melanopterus and T. obesus suggests that these aggregations are related to reproduction. All species displayed inter-annual site fidelity. The long-term presence of juvenile C. melanopterus and N. acutidens also suggests that this bay provides suitable conditions for younger age classes.
In the north-west Atlantic Ocean, stock assessments conducted for some commercially harvested coastal sharks indicate declines from 64 to 80% with respect to virgin population levels. While the status of commercially important species is available, abundance trend information for other coastal shark species in the north-west Atlantic Ocean are unavailable. Using a generalized linear modelling (GLM) approach, a relative abundance index was derived from 1994 to 2009 using observer data collected in a commercial bottom longline fishery. Trends in abundance and average size were estimated for bull shark Carcharhinus leucas, spinner shark Carcharhinus brevipinna, tiger shark Galeocerdo cuvier and lemon shark Negaprion brevirostris. Increases in relative abundance for all shark species ranged from 14% for C. brevipinna, 12% for C. leucas, 6% for N. brevirostris and 3% for G. cuvier. There was no significant change in the size at capture over the time period considered for all species. While the status of shark populations should not be based exclusively on abundance trend information, but ultimately on stock assessment models, results from this study provide some cause for optimism on the status of these coastal shark species.
Many marine populations and ecosystems have experienced strong historical depletions, yet reports of recoveries are increasing. Here, we review the growing research on marine recoveries to reveal how common recovery is, its magnitude, timescale and major drivers. Overall, 10-50% of depleted populations and ecosystems show some recovery, but rarely to former levels of abundance. In addition, recovery can take many decades for long-lived species and complex ecosystems. Major drivers of recovery include the reduction of human impacts, especially exploitation, habitat loss and pollution, combined with favorable life-history and environmental conditions. Awareness, legal protection and enforcement of management plans are also crucial. Learning from historical recovery successes and failures is essential for implementing realistic conservation goals and promising management strategies.
Worldwide, decision-makers and nongovernment organizations are increasing their use of citizen volunteers to enhance their ability to monitor and manage natural resources, track species at risk, and conserve protected areas. We reviewed the last 10 years of relevant citizen science literature for areas of consensus, divergence, and knowledge gaps. Different community-based monitoring (CBM) activities and governance structures were examined and contrasted. Literature was examined for evidence of common benefits, challenges, and recommendations for successful citizen science. Two major gaps were identified: (1) a need to compare and contrast the success (and the situations that induce success) of CBM programs which present sound evidence of citizen scientists influencing positive environmental changes in the local ecosystems they monitor and (2) more case studies showing use of CBM data by decision-makers or the barriers to linkages and how these might be overcome. If new research focuses on these gaps, and on the differences of opinions that exist, we will have a much better understanding of the social, economic, and ecological benefits of citizen science.
Ecology Letters (2010) 13: 1055–1071
Abstract
Whereas many land predators disappeared before their ecological roles were studied, the decline of marine apex predators is still unfolding. Large sharks in particular have experienced rapid declines over the last decades. In this study, we review the documented changes in exploited elasmobranch communities in coastal, demersal, and pelagic habitats, and synthesize the effects of sharks on their prey and wider communities. We show that the high natural diversity and abundance of sharks is vulnerable to even light fishing pressure. The decline of large predatory sharks reduces natural mortality in a range of prey, contributing to changes in abundance, distribution, and behaviour of small elasmobranchs, marine mammals, and sea turtles that have few other predators. Through direct predation and behavioural modifications, top‐down effects of sharks have led to cascading changes in some coastal ecosystems. In demersal and pelagic communities, there is increasing evidence of mesopredator release, but cascading effects are more hypothetical. Here, fishing pressure on mesopredators may mask or even reverse some ecosystem effects. In conclusion, large sharks can exert strong top‐down forces with the potential to shape marine communities over large spatial and temporal scales. Yet more empirical evidence is needed to test the generality of these effects throughout the ocean.
The effects of habitat on the ecology, movements, and foraging strategies of marine apex predators are largely unknown. We used acoustic telemetry to quantify the movement patterns of blacktip reef sharks (Carcharhinus melanopterus) at Palmyra Atoll National Wildlife Refuge, in the Pacific Ocean. Sharks had relatively small home ranges over a timescale of days to weeks (0.55 +/- 0.24 km2) and showed strong site fidelity to sand-flat ledges within the west lagoon over a three-year period. Sharks showed evidence of diel and tidal movements, and they utilized certain regions of the west lagoon disproportionately. There were ontogenetic shifts in habitat selection, with smaller sharks showing greater selection for sand-flat habitats, and pups (total length 35-61 cm) utilizing very shallow waters on sand-flats, potentially as nursery areas. Adult sharks selected ledge habitats and had lower rates of movement when over sand-flats and ledges than they did over lagoon waters. Fractal analysis of movements showed that over periods of days, sharks used patches that were 3-17% of the scale of their home range. Repeat horizontal movements along ledge habitats consisted of relatively straight movements, which theoretical models consider the most efficient search strategy when forage patches may be spatially and temporally unpredictable. Although sharks moved using a direct walk while in patches, they appeared to move randomly between patches. Microhabitat quantity and quality had large effects on blacktip reef shark movements, which have consequences for the life-history characteristics of the species and potentially the spatial distribution of behaviorally mediated effects on lower trophic levels throughout the Palmyra ecosystem.
Marine ecosystems are suffering severe depletion of apex predators worldwide; shark declines are principally due to conservative life-histories and fisheries overexploitation. On coral reefs, sharks are strongly interacting apex predators and play a key role in maintaining healthy reef ecosystems. Despite increasing fishing pressure, reef shark catches are rarely subject to specific limits, with management approaches typically depending upon no-take marine reserves to maintain populations. Here, we reveal that this approach is failing by documenting an ongoing collapse in two of the most abundant reef shark species on the Great Barrier Reef (Australia). We find an order of magnitude fewer sharks on fished reefs compared to no-entry management zones that encompass only 1% of reefs. No-take zones, which are more difficult to enforce than no-entry zones, offer almost no protection for shark populations. Population viability models of whitetip and gray reef sharks project ongoing steep declines in abundance of 7% and 17% per annum, respectively. These findings indicate that current management of no-take areas is inadequate for protecting reef sharks, even in one of the world's most-well-managed reef ecosystems. Further steps are urgently required for protecting this critical functional group from ecological extinction.
Citizen science as a tool for conservation in residential ecosystems
- Cooper