Daniel Pauly


Research Interests

World fisheries
Marine life
Global catch
Management of fisheries
Fish growth and ecophysiology

Relevant Thesis-Based Degree Programs


Great Supervisor Week Mentions

Each year graduate students are encouraged to give kudos to their supervisors through social media and our website as part of #GreatSupervisorWeek. Below are students who mentioned this supervisor since the initiative was started in 2017.


Professor Pauly is an extraordinary supervisor and person. He has believed in me, guided me and mentored me since I first joined the graduate program. He is there for all his students, ready and willing to help them with any obstacles they encounter. He is exceptionally kind and understands the challenges that graduate students face daily. He has been especially supportive of international graduate students like me, who must deal with the difficulty of being far from their families and homelands. He is respectful and he is encouraging. I continue to learn from him every day, and he never ceases to surprise us (my peers and I) with his immense knowledge of most things. I could not have dreamt of a better supervisor. I will forever be grateful to Dr. Pauly for his mentorship and for his support.

Myriam Khalfallah (2019)


Many people know Dr. Pauly as a world-renowned fisheries scientist and an author or co-author of over 30 books and 1000 scientific articles. I am honoured to know him for his honesty, inclusivity, humour, and encouragement in his role as my supervisor. Dr. Pauly never fails to provide positive feedback and constructive criticism in order to guide me along my academic journey. Under his leadership, I always feel as though I am part of a strong and diverse team, where my voice matters and is heard. These are just a few of the reasons why Dr. Pauly is a #GreatSupervisor. 

Rebecca Schijns (2019)


Professor Pauly is a "GreatSupervisor" not only because he has very proficient professional knowledge and creative ideas, which is able to give me effective guidance to my study and research, but also because of his serious and responsible attitude to his work and my study. He always shows the very high patient to me to encourage me to do the right things. In spare time, he is humourous and erudite and teaches us a lot of things about life, culture, and nature. Get along with him motivate my great interest in work and life. He is the best supervisor I have met. He is totally worthy of the "GreatSupervisor".

Lu Zhai (2019)


Graduate Student Supervision

Doctoral Student Supervision

Dissertations completed in 2010 or later are listed below. Please note that there is a 6-12 month delay to add the latest dissertations.

The de facto protection of Marine Protected Areas (2022)

Marine Protected Areas (MPAs) are the most common tool used to conserve marine resources. Officially, 8% of the world’s ocean are protected by MPAs. However, due to inadequate implementation, MPAs often fail to achieve the desired outcomes, causing vital ecosystem services to be jeopardized. Currently, there is no clear understanding of how much of our oceans is de facto protected. This thesis fills this gap through a global assessment of MPAs' status by providing insights into the different types of existing MPAs.The first chapter of this thesis emphasizes these points. The second chapter compares the evolution of fisheries in four territories in the Pacific, using comprehensive catch data from 1950 to 2018, and shows that Exclusive Economic Zones are viable tools for coastal countries to manage fisheries. It also shows that MPA designation may fall victim to political convenience, resulting in so-called ‘paper parks.’ The third chapter identifies areas of the Pacific that are important for conservation by superposing the migration routes of 11 large pelagic fish species and presents possible ‘blue corridors’ to protect those fish stocks. To understand the protection level or status of MPAs, a ‘one-question questionnaire’ was sent to over 3,000 academics, NGO staff, fishers, journalists and civil servants with a relationship to MPAs in their country. This represented an affordable and replicable methodology to assemble local knowledge about MPAs and to perform comparative analyses of the stakeholders’ answers. The returns from this questionnaire are analyzed in the fourth and fifth chapters, with the former emphasizing the range of answers and the latter the type of answers, by stakeholder occupation.The sixth chapter summarizes the arguments of the previous chapters and illustrates their application through an exemplary documentary film produced by the candidate. The film is a case study of a ‘paper park’ in Argentina and highlights the role of science communication in creating community support for greater marine protection in their area. Overall, this thesis advances our understanding of the de facto protection status of MPAs around the world and provides a basis for increasing their effectiveness.

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Data-poor fisheries: case studies from the southern Mediterranean and the Arabian Peninsula (2020)

Considerable gaps of knowledge regarding the state of the marine fisheries occur in most economically developing countries despite the importance of fisheries as a source of food security and livelihood for their inhabitants. Global studies in fisheries science have often disregarded the data-poor fisheries in economically developing countries due to a combination of factors including the high cost and data requirements of classical stock assessments. However, other methods, less costly and equally reliable, such as the catch reconstruction approach combined with catch-based indicators and the most recent ‘CMSY’ stock assessment method have been developed to help assess the state of marine living resources. The countries of the Southern Mediterranean and the Arabian Peninsula (SMAP) are examples of where marine fisheries are not as well assessed as in other regions, aggravated by the frequency of political and socio-economic instability, the latest being the so-called “Arab Spring”, which has deeply impacted the regions. The "catch reconstruction" method, which improves official catch statistics, is applied here to re-estimate marine fisheries catches for the SMAP for 1950-2015 and to reconstruct a century of Mediterranean marine fisheries catches for Egypt (i.e., 1917-2017) to which two catch-based indicators, i.e., the Marine Trophic Index and the Mean Temperature of Catch were also applied. In the third part of this thesis the CMSY method is used to assess several commercially important fish stocks of the SMAP to provide decision makers with alternative policy options for better fisheries management and more effective marine conservation strategies.

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Jellyfish fisheries of the world (2017)

Fisheries for jellyfish (primarily scyphomedusae) have a long history in Asia, where people have been catching and processing jellyfish as food for centuries. More recently, jellyfish fisheries have expanded to the Western Hemisphere, often driven by demand from buyers in Asia as well as collapses of more traditional local finfish and shellfish stocks. Despite this history and continued expansion, jellyfish fisheries are understudied, and relevant information is sparse and disaggregated. Catches of jellyfish are often not reported explicitly, with countries including them in fisheries statistics as “miscellaneous invertebrates” or not at all. Research and management of jellyfish fisheries is scant to nonexistent. Processing technologies for edible jellyfish have not advanced, and present major concerns for environmental and human health. Presented here is the first global assessment of jellyfish fisheries, including identification of countries that catch jellyfish, as well as which species are targeted. A global catch reconstruction is performed for jellyfish landings from 1950 to 2013, as well as an estimate of mean contemporary catches. Results reveal that all investigated aspects of jellyfish fisheries have been underestimated, including the number of fishing countries, the number of targeted species, and the magnitudes of catches. Contemporary global landings of jellyfish are at least 750,000 tonnes annually, more than double previous estimates. Jellyfish have historically been understudied, resulting in the current dearth of knowledge on population dynamics and jellyfish fishery management. However, many of the tools used in traditional fisheries science, such as length-frequency analysis, can be applied to jellyfish, as demonstrated herein. Research priorities are identified, along with a prospective outlook on the future of jellyfish fisheries.

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Effects of seaweed farming on tropical shallow coral ecosystems (2016)

Seascapes are being transformed by human activities through a variety of spatially extensive extractive uses. This industrialization has the potential to radically alter the ecology of our oceans. Through focused ecosystem-based management of already degraded systems, it may be possible to create novel ecosystems that maximize benefits for humans, while increasing the diversity and abundance of dependent communities. In this thesis I examine seaweed farming on degraded coral reef ecosystems in order to examine 1) the relationship between seaweed farms and rabbitfish production globally, 2) the relationship between seaweed farms established on shallow coral reef ecosystems and fish assemblage composition, and 3) the diet composition of herbivorous fish in relation to the presence of seaweed farms. I found a correlation between seaweed farming and catches of rabbitfish (family Siganidae), implying farms may drive herbivorous fish catch in Southeast Asia. However, within regions, I found little evidence of increased abundance, biomass, and size of rabbitfish in areas with farms relative to those without. Therefore, the addition of farmed seaweeds was unlikely to subsidize rabbitfish diets, but replaced wild seaweeds removed by farmers. Investigation of seaweed farming activities on coral reef fish assemblages found farms negatively impacted diversity, abundance, and total biomass even in locations subject to blast fishing. These results have significant implications for the management of shallow coral ecosystems. Traditionally, areas of human use within seascapes are divided into distinct categories of use vs. wilderness. Increasingly seascapes have become patchworks of human use, and their impacts may result in different ecological functions. The designation of an area for restoration, protection, or a particular use must be based on several factors including the potential for the activity to alter ecosystem function as well as its ecological context. A novel ecosystems approach to degraded shallow coral reef ecosystems would dictate further human activities within radically altered systems account for both the current ecological function and the entire range of options for further use rather than only focusing on use and impacts solely in terms of traditional restoration.

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Fishing impacts on the trophic functioning of marine ecosystems, a comparative approach using trophodynamic models (2015)

Faced with the global overexploitation of marine resources and the rapid degradation of ecosystems’ integrity, many states agreed to the principle of an ecosystem approach to fisheries (EAF). In fact, overfishing induces strong decrease of targeted species biomass, which impact predators, their competitors, prey, and ultimately the ecosystems’ trophic networks. Thus, it is an important challenge to understand the trophic functioning of marine ecosystems and the related impacts of fisheries.In this spirit, my thesis was developed to address concerns about the potential impacts of fisheries on the underlying trophic functioning, and to better understand this trophic functioning and its variability through ecosystems. Two well-known trophodynamic models were used : Ecopath with Ecosim (EwE) and EcoTroph (ET). First, I developed EcoBase, i.e., an online repository to gather and communicate information from EwE models, which enabled to give a global overview of the applications of the EwE modeling approach. Then, the ET model was corrected and standardized through the creation of a software package in R. A new trophic control, i.e., foraging arena (FA) trophic control, was integrated to study its impacts on trophic flows and fishing effects on aquatic ecosystem trophic networks. I showed that that making ecosystem behavior more realistic by incorporating FA controls into EcoTroph decreased the resistance and the production of modeled ecosystems facing increasing fishing mortality. An analysis of case studies focusing on marine protected areas (MPAs) was then performed using EwE and ET. I analyzed the potential spillover effect from three MPAs, and showed that their potential exports were at the same order of magnitude as the amount of catch that could have been obtained inside the reserve. Finally, a meta-analysis of marine ecosystem trophic functioning was conducted using 127 EwE models, which showed that ecosystem types were distinguished by different biomass trophic spectra and associated trophic indices. These differences were mainly driven by different production, but also kinetic for some ecosystem types. In conclusion, trophodynamic models, as EwE and ET, appeared to be useful tools to better understand the trophic functioning of marine ecosystems, its variability through ecosystems, and the associated impacts of fisheries.

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In the wake of the dhow: historical changes in the marine ecology and fisheries of the Persian Gulf (2015)

Marine ecosystems have been altered by human activities over millenia, but ecological and fisheries data used to measure these changes are typically only available over the last few decades. Moreover, recent databases, such as the United Nations Food and Agriculture Organization’s (FAO) FishStat, do not reflect the true catch of seafood. The misreporting of catches, coupled with a lack of historical reflection can lead to mismanagement and poor policy decisions that jeopardize food security. While these issues are prevalent worldwide, they are especially problematic in places such as the Persian Gulf, where a rich seafaring history is at odds with recent mega-development projects.Developing methods to integrate a diversity of data types is essential for better quantifying changes in the distribution and abundance of marine organisms, as well as for clarifying underlying causes of ecological change. Within the field of historical marine ecology, studies have relied on anecdotal evidence, such as written accounts by explorers and interviews of different generations of resource users, to demonstrate the former abundance of certain species and the extent of their ranges. Intercoder reliability tests show that people's perceptions of historical anecdotes are generally consistent and speak to the reliability of using people's perceptions to acquire quantitative data. In the Persian Gulf, anecdotes can be used to examine changes in dugong abundance and distribution and assessing the efficacy of current management targets.Fishery catch reconstructions for the Persian Gulf from 1950-2010 show that officially reported catches potentially underestimate capture fisheries by a factor of 2, and that countries have primarily reported their artisanal and industrial catches, and substantially underreported their discards, recreational, subsistence, and illegal fishing sectors. In addition, recent advances in remote-sensing technology allow us to view stationary fishing gear such as weirs from space and mitigate gaps in catch reporting.This dissertation provides context to marine ecosystem management decisions in the Gulf. Because no empirical studies on the region have incorporated historical data, studies on the present ecosystems are based on distorted historical trends and impair our understanding of the management and policy prescriptions necessary for fisheries sustainability in the region.

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Past, Present and Future of Publicly-Funded European Union's Fishing Access Agreements in Developing Countries (2015)

Since the 19th century, with the expansion and industrialization of extractive industries, maritime jurisdictions have shifted from chiefly open-access to a regime regulated by the UN Convention on the Law of the Sea (UNCLOS). This thesis examines fishing access agreements, i.e., legal tools that allow one country to fish in the waters of another one following mutually-agreed terms. The emphasis is on the particular fisheries access agreements funded by EU-taxpayers, and the aim is to test the common belief that their economic, social, and environmental provisions have improved over time vis-à-vis the host countries. To date, only little has been published on this topic, and thus this examination of their provisions is of paramount importance for the policy realm. Chapters 1 and 2 challenge the legal ground of such agreements, which rests on the questionable notion of fisheries 'surplus' that must be made available to other countries according to UNCLOS. Flaws in the estimation of surplus are noted: in most cases, the surplus cannot be calculated due to inaccurate catch estimates, and ceding a potential surplus to foreign countries results in hard-to-justify decreases in domestic catches. Chapter 3 argues that since their inception, the level at which these agreements have been subsidized remained extremely high (around 75%); the remainder (paid by fleets' operators) represented only a small fraction of their gross revenue, highlighting a potential imbalance in allocation of benefits. Finally, Chapter 4 demonstrates that despite advances in most social and environmental provisions, the one regarding the supervision of foreign vessels by observers (arguably the most critical provision of all) has declined. These results beg the question: how legitimate are such access agreements? While they are lauded for their transparency, they appear to remain mostly beneficial to European interests and poorly monitored. Also, due to the fishing expansion occurring in host countries and ongoing international trade reforms, one can only wonder whether such historical 'pay-fish-and-go' agreements still ought to continue.

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West African fisheries: past, present and 'futures?' (2015)

This thesis provides evidence for why more complete fisheries catch estimates should be included in fisheries assessments. West African fisheries suffer over-exploitation, illegal fishing and overcapacity. Certainly, overlooking small-scale sectors and attributing “zero” to existing gaps do not improve the situation. Under-reporting masks fisheries real trends and overcapacity, contributing to intensifying over-exploitation, whose impacts, along with the effects of climate change, could be disastrous. My research focuses on the fisheries of the Western part of the African continent. I begin by presenting methods to estimate the “invisible” catch through the case study of Senegal. I designed this “catch reconstruction” to illustrate the effects of illegal fishing on small-scale fisheries whose geographical range has increased significantly. I used reconstructed data for small-scale fisheries to quantify their contribution to employment and the economy, their profitability and the evolution of fisher’s income as compared to the national poverty line. I found that people increasingly rely on fisheries despite their low income, now dangerously close to the poverty line.Foreign fisheries also contribute to generating income, but also to income losses. I compare the performance of fisheries by China and Europe in West Africa in terms of reporting, illegal fishing and compensation. It appears that despite the inherent policy differences between China and Europe in terms of their Distant Water Fleet (DWF) operations, they both under-reported catches, fished illegally and undercompensated for fishing agreements. They also both contribute to reducing the biomass of fish available to local fishers, and hence to a reduction fishing opportunities and incomes.Fish stocks, and therefore, fisheries are also affected by climate change. I examine these effects and overlap them with some fisheries socio-economic indicators and found that artisanal fishers were more likely to “follow the fish” by expanding their fishing range, while industrial fishers seem to have more flexible as their range of adaptation strategies appears to be wider. In summary, the work on West African fisheries refutes the myth of “lack of data”, and I show that sufficient data exist to analyze the effects of current fisheries policy, and by implication, to formulate alternatives.

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Government-led development of India's marine fisheries since 1950: Catch and effort trends, and bioeconomic models for exploring alternative policies (2014)

At present, more than 50% of global marine fisheries catches are made in developing countries, and an increasingly large fraction of these catches are entering the world market. Thus, fisheries-related issues in developing countries must be addressed as part of any discussion of global fisheries issues. This thesis analyses the status of marine fisheries in India by reconstructing essential data and constructing biological and economic models. First, effort data were reconstructed over the period of 1950-2005 at the state level. This showed a continuous increase. Then, the catch data were updated and assembled from 1950-2005 at the species level for all states, which showed a gradual increase over time but began to level off toward the end of the period in question. CPUE, an index of relative abundance, was estimated per study area using the final time-series of catches and effective fishing effort from 1950-2005. This measure illustrated a continuous decline. Using the above-compiled data, i.e., time series of catch and CPUE, surplus production models (Fox-linear and Schaefer-non-linear) were created for India and its east and west coasts. Both types of model used in this study indicated that at present, fisheries yields in India are near MSY, but this is achieved at excessive levels of effort and is based on a spatial expansion that is unsustainable. Economic performance was evaluated by bioeconomic models for India in which three scenarios were generated for fishing cost based on the inclusion of different levels of subsidies. The results illustrate that economic overfishing is occurring in the Indian fisheries and the current level of fishing effort is almost twice that corresponding to fMEY, i.e., far beyond the level that maximizes economic rent. Overall, the analysis indicates that fisheries are operating unsustainably, pointing toward a serious problem. Thus, India should not continue on its present course of expanding its fisheries through massive subsidization, given the depletion of stocks and poor economic efficiency of this sector. India needs to curb its existing overcapacity and could effectively start with the phasing out of trawlers, which would increase the income of other sectors and their catch per effort.

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Assessment of the Red Sea Ecosystem with Emphasis on Fisheries (2012)

A comprehensive assessment of the Red Sea large marine ecosystem (LME), with emphasis on fisheries, was carried out using several approaches. The assessment started with a multidisciplinary rapid appraisal of the sustainability of the fisheries using standardized attributes in ecological, economic, social, technical and ethical fields. Then a time-series assessment of the fishery was carried out using data from interviews and the reconstruction of catch from 1950 - 2006. A case study to estimate the unreported catch by quantifying qualitative information on incentives to misreport was carried out for Eritrean fisheries. Finally, a comprehensive and detailed assessment was done in an ecosystem-based framework using the modelling tool Ecopath with Ecosim (EwE), which quantifies the trophic interactions of the organisms and fisheries. It was used to predict the impact of different scenarios of fisheries on the ecosystem and explore the conflict between artisanal and industrial fisheries. Uncertainty analysis was carried out for the different assessment methods employed.The results of the assessments have varying levels of detail: relative ranking of the sustainability of fisheries in the rapid appraisal assessment, relative quantitative changes over time in the interview analysis, actual historic quantitative assessment of the catches in the catch reconstruction, and finally a quantitative assessment with potential to predict future scenarios using ecosystem modelling. The results give a holistic understanding of the Red Sea ecosystem and its fisheries. The data and resources needed increased as the details of the outputs increased. The assessments complemented each other and there are similarities in the results. They all showed declines in all fisheries, except for beach seining. Sharks, the top predator of the system, showed the worst decline in all the assessments; and the interview and catch reconstruction methods gave strikingly similar results for sharks. The ecosystem modelling did not show direct impact between artisanal and industrial fishery sectors due to the lack of trophic interactions. In addition, the thesis demonstrates that fishery researchers and practitioners can utilize different assessment tools, given the resources at their disposal, to assist the management of resources to conserve ecosystems and livelihoods.

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Sea turtle conservation and ecosystem-based management with a focus on green turtles (Chelonia mydas) and seagrass beds (2010)

The design of effective species management and recovery plans for sea turtle populations requires targets that are informed by an understanding of knowledge gained at the level of individuals/populations in the context of the wider goal of protecting an ecosystem's structural and functional attributes. In this thesis I present the first detailed investigation of the multiple levels at which sea turtles, particularly green turtles (Chelonia mydas), interact with ecosystems. I begin by developing a framework for an age-structured population-level assessment of food consumption for hawksbill (Eretmochelys imbricata), loggerhead (Caretta caretta), and green turtles. This entailed construction of species-specific growth models for the western Atlantic, and subsequent integration of results with morphometric, survival, abundance, and food conversion efficiency to derive consumption estimates.At the ecosystem level, I developed models for the Caribbean and Hawai’í, where green turtles are present at very low abundances and reaching carrying capacity, respectively. In the Caribbean, results showed that green turtle grazing of seagrass substantially altered habitat complexity, reducing the refuge role of seagrass to reef fish and invertebrates, and leading to potentially dramatic changes in species biomass and composition. In Hawai‘i, by feeding on algae, green turtles were found to contribute to the resilience of reefs in the face of disturbance, a functional role that needs to be explicitly included in future studies of reef dynamics. Taken together, these findings highlight the need to consider trophic and indirect interactions in the evaluation of sea turtles’ role within ecosystems.Accurate and reliable estimates of foraging habitat extent are essential to inform realistic and sustainable turtle recovery targets, particularly given the current degraded state of coastal ecosystems. Using Landsat satellite imagery, I present a novel mapping approach for seagrass habitats at large scales. Such regional initiatives are also urgently needed if the international community is to meet aims to conserve 10 – 30 % of specific habitats. A comparison between reef extent, determined using remote sensing and existing data, showed that discrepancies ranged from + 1,316 % to - 64 %, underlining our limited ability to ascertain progress towards adopted global marine conservation targets based on current data.

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Fish as food in an age of globalization (2009)

The human appetite for seafood has intensified and so has overfishing and damage to marine ecosystems. However, the true demand for seafood is often not captured in the national or United Nations Food and Agriculture Organization (FAO) statistics. The underreporting of catches is prevalent worldwide, which inevitably leads to mismanagement, and justifies data improvements via catch reconstructions.For instance, marine fisheries catch reconstructions for 1950 to present for Mozambique and the United Republic of Tanzania show that the small-scale fisheries sectors in both countries are underreported. Overall, reconstructed marine fisheries catches for Mozambique and Tanzania were respectively 6.2 and 1.7 times greater than those reported by FAO. Similarly, shark catches have been underreported globally, and reconstruction of Ecuador’s mainland shark landings for 1979 to 2004 shows that shark landings were an estimated 7,000 tonnes per year, or nearly half a million sharks, and 3.6 times greater than those reported by FAO from 1991 to 2004.Over the past decades, as we realize fish catches are larger than officially reported and demand for seafood is outstripping the availability of wild resources, conservation groups have been attempting to change patterns of household consumption, particularly in North America and Europe. These groups aim to reduce overfishing and encourage sustainable fishing practices using tools like consumer awareness campaigns and seafood certification schemes. But many factors impede these efforts, such as the renaming and mislabeling of seafood, the absence of a significant price premium for certified seafood, and, most importantly, a lack of demonstrably improved conservation status for the species that are meant to be protected.This dissertation presents market-based initiatives that may strengthen current initiatives, e.g. global adoption of chain of custody standards, working higher in the demand chain, connecting seafood to climate change, and diverting small fish away from the fishmeal industry into human food markets. Also, conservation groups should consider investing as much effort into the elimination of harmful fisheries subsidies, the primary perverse incentive encouraging excess fishing capacity, as they put into altering consumer behavior. Finally, conservationists can learn from the latest research on the psychology of savings and investment. If these market efforts complement more marine protected areas and regulations, it may be possible to ensure fish as food and wildlife for both current and future generations.

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Master's Student Supervision

Theses completed in 2010 or later are listed below. Please note that there is a 6-12 month delay to add the latest theses.

Estimating the inland fisheries catch (1950-2019) of data-sparse countries and territories, with emphasis on Africa (2023)

The only official and global fisheries catch dataset in existence is that being annually compiled and distributed by the Food and Agriculture Organization of the United Nations (FAO) since 1950. However, the Sea Around Us team has identified, documented, and corrected inconsistencies in the global marine fisheries catch data published by FAO by performing ‘reconstructions’ of marine fisheries catch time series for all coastal countries and territories of the world. These reconstructions demonstrate that globally, the official marine fisheries catch is underreported by 50%. While the Sea Around Us currently does not offer a database for inland fisheries catches, the peer-reviewed literature does contain examples of inland fisheries catch underreporting. Therefore, this thesis addresses the underreporting of inland fisheries catches by producing mostly-partial inland fisheries catch reconstructions covering the years 1950 to 2019 for all countries and territories of the African continent, as well as 48 non-African countries and territories. The main results of this thesis are that the inland fisheries catch of the assessed countries and territories are underreported by 50% or more in 87% of cases, and also that the inland fisheries catch of African countries and territories are underreported by a factor of 2.4 from 1950 to 2019, although the reliability of reported catches has improved throughout the analysis period. These results are consistent with those of independent, peer-reviewed studies of inland fisheries catch underreporting. Moreover, these results demonstrate that African marine and inland fisheries catches are similarly underreported, while, overall, there is greater variation in underreporting of inland fisheries catches. These results support the notion that, like marine fisheries, inland fisheries are critical to humanity, and are similarly deserving of attention.

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Urea (ka)! The role of urea and oxygen in the relationship between length at first maturity and maximum length in ureotelic and non-ureotelic cartilaginous fishes (2023)

The Gill Oxygen Limitation Theory (GOLT) is a single unifying theory which uses the geometric constraints of fish gills to explain their growth, reproduction, and ecology. A major aspect of the GOLT describes that with growth, relative oxygen supply declines, leading to a critical hypercapnic/acidic threshold. This threshold is assumed to trigger maturation and explains why the relationship between maximum length (Lmaxᴰ) and length at maturity (Lmᴰ) is conserved across evolutionary distinct fishes (‘D’ represents the growth of the gills). While well documented in bony fishes, this relationship has only been minimally explored in cartilaginous species. This research addresses this knowledge gap through investigation of chimaera, ray, and shark species in which at least one Lmax/Lm data pair could be obtained from the literature. Using multivariate regression modeling, it was shown that Lmaxᴰ/Lmᴰ is similarly conserved across marine Chondrichthyes (Lmaxᴰ/Lmᴰ≈1.14). However, this relationship is lower than seen in bony fish (Lmaxᴰ/Lmᴰ≈1.35), suggesting that cartilaginous species mature at a greater fraction of their maximum size. Following up on this anomaly, it was hypothesized that the high concentrations of urea retained by marine Chondrichthyes (used for osmoregulation) is the likely reason for this delay. This hypothesis was tested through comparison of marine, euryhaline, and freshwater rays which all retain differing concentrations of urea. Modeling among these groups indicated that decreasing urea retention is correlated to an increase in Lmaxᴰ/Lmᴰ. Notably, freshwater rays (no retention of urea) display an Lmaxᴰ/Lmᴰ ratio (≈1.30) almost identical to bony fishes. It is suggested that the carbon dioxide required for urea production allows ureotelic species to offset the critical maturation threshold, through prolonged maintenance of a neutral internal pH, compared to non-ureotelic species. Furthermore, the increased oxygen demands associated with viviparity (live-bearing) is also correlated to a higher Lmaxᴰ/Lmᴰ ratio, independent of phylogeny or habitat. However, analogous to non-viviparous species is a similar relationship between Lmaxᴰ/Lmᴰ and urea retention, implicating the role of the gills and urea in maturation of these species. Overall, this thesis lends strong support to the existence of a critical maturation threshold while also suggesting a role for urea that was previously unknown.

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What has Canada caught, and how much is left? Reconstructing and assessing fisheries in three oceans (2020)

Canada’s marine fisheries occur in three oceans, designated by Pacific, Arctic and Atlantic Exclusive Economic Zones (EEZs), where management bodies utilize catch records in order to make decisions regarding the future of their fisheries. However, current catch reporting systems and stock assessment processes are flawed, as catch records are missing key fishery components and assessments may use time series that do not represent the full scale of change. These shortcomings can directly impact the perception of healthy fisheries and influence future management decisions. This research provides a comprehensive catch record for all available marine populations in Canada’s three surrounding EEZs from 1950-2017 in order to estimate their current status and provide reference points that may be useful for managers to secure marine resources for the future. Catch reconstructions initially done by the Sea Around Us group and external collaborators, are refined and updated to 2017. Using reconstructed time series, the most recent ‘CMSY’ stock assessment method allows reference points to be estimated and reveals that the majority of Canadian fisheries need rebuilding. As well, ‘CMSY’ analyses are used to investigate shifting baseline effects on selected official stock assessments that exhibit shortened catch time series. Overall, this research contributes to improving scientific baselines in order to gain a better understanding of Canadian fisheries from a historical and managerial perspective.

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Evaluating and enhancing the taxonomic resolution of shark and ray (Subclass Elasmobranchii) catch statistics in the Mediterranean and Black Seas (1950-2014) (2018)

To sustainably manage fisheries, the stock biology, ecology, and its past and present human exploitation must be known. To monitor fisheries, the Food and Agriculture Organization of the United Nations began collecting and harmonizing country catch reports in the late 1940s. In 1950, it issued its first global annual catch statistics, which have continued until the present. This official reported catch has been shown to vastly underrepresent the entirety of the world's catch. The small-scale fisheries sectors (i.e., artisanal, subsistence, and recreational) are largely unreported, in addition to incidental catches of non-target species, much of which is discarded. The latter component of the catch is often comprised of species that are more biologically vulnerable to overfishing than target species. Sharks and rays (subclass Elasmobranchii) are one such group of species. One in four elasmobranch species are estimated to be threatened with extinction, primarily as a result of overfishing. Unfortunately, elasmobranch catch data are notoriously underreported and imprecise.This thesis sought to elucidate the elasmobranch catches of the Mediterranean and Black Seas, where over half of shark and ray species are threatened with extinction but data deficiency and ambiguity consistently limit conservation action. A Taxonomic Resolution Index (TRI) was calculated for the catches of 24 countries over 65 years (1950-2014) to evaluate the quality of catch reporting over time. The TRI revealed that less than a quarter of commercial elasmobranch taxa are represented in Mediterranean and Black Seas catch data, and reporting quality has hardly improved. While many countries have improved their reporting since the 1950s, the original leaders (e.g., Malta and Georgia) have seen their position worsening over time. The species composition of reconstructed historical elasmobranch catch was also investigated. The fishery characteristics of species-specific catches were modeled and used to estimate unknown species-specific proportions within aggregated catch categories (e.g., "sharks and rays"). Over half a million tonnes of species-specific catch was disaggregated, increasing the species-specific proportion of reported catches by over 10%. These results, combined with a literature review, imply weak implementation and enforcement of existing protective regulations, despite precipitous declines of elasmobranchs in the Mediterranean and Black Seas.

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Considering the 'effort factor' in fisheries: a methodology for reconstructing global fishing effort and carbon dioxide emissions, 1950 - 2010 (2015)

Whether or not fisheries are sustainable not only affects ocean health, but also human health; a large portion of the population depends on marine ecosystems for food, livelihoods and social values. Our understanding of how fishing impacts the environment is lacking and under the threats of global climate change, the extent to which the ocean can continue to provide goods and services is questionable. Chapter 1 introduces some critical knowledge gaps in fisheries and problems with how marine resources have been managed in the past. Chapter 2 describes a methodology that can be used to quantify and reconstruct historical fishing effort to create a global fishing effort database. Historically fisheries management has not given adequate consideration to the ‘effort factor’, potentially resulting in the mismanagement of marine resources. The methodology was applied to the Exclusive Economic Zones of 9 maritime countries, and preliminary results suggest that, although fishing effort appears to be stabilizing, catch per unit of effort is decreasing. Chapter 3 uses the fishing effort calculated in Chapter 2 to estimate the CO₂ emissions from fishing over time. Fishing is not perceived as an important contributor to greenhouse gas emissions and climate change, despite using fishing vessels that rely on the combustion of fossil fuels (Wilson 1999). As in Chapter 2, the methodology was applied to 9 EEZs. It was found that the CO₂ per unit of catch (CO₂PUC; tonnes) increased, despite increases in fuel efficiency, and the industrial sector emitted 3 times more CO₂PUC than the small-scale sector in 2010. It was estimated that fishing contributes approximately between 2.8 – 5.2% to global CO₂ emissions annually. The final chapter, Chapter 4, discusses the preliminary results of the 9 sample EEZs within the context of the sustainability of fisheries and what it means to be sustainable.

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Actual and perceived decline of fishery resources in Turkey and Cyprus: A history with emphasis on shifting baselines (2014)

The FAO global statistics on fisheries catches is an important tool used to track overall patterns, as it represents the only global account of fisheries catch records from all member countries. However, the database is only as complete as the data sent to them by member countries, which often lack catch amounts from non-commercialized sectors. The aim here for Chapters 2 and 3 were to comprehensively account for total fisheries removals for Turkey and Cyprus from 1950-2010, by estimating catches for previously unaccounted sectors, using best available data. It was found that the total reconstructed catch for Turkey was about 80% higher (33 million t) than the 18.4 million t reported to FAO during the period from 1950 to 2010. The total reconstructed catch for Cyprus was about 2.6 times higher (243,000 t) than the 93,200 t reported to FAO for Cyprus for the same period, which thus excluded catches from the north of the country from 1974 to 2010. For Chapter 4, using total reconstructed catches and annual fleet dynamics statistics, total effort and Catch Per Unit Effort (CPUE) were calculated for Turkey as a whole, and each of its seas. Next, from field survey results from Turkey and Cyprus, each fisher’s ratio of initial to current CPUE and perceived change in resource abundance was computed for their career span, according to sector. Lastly, the two trends in ratio of initial to current CPUE and perceived change in resource abundance were compared to determine if ‘shifting baselines’ had occurred. For Turkey as a whole total effort increased by over 700% from 25 million kW days in 1967 to nearly 190 million kW days in 2010, while CPUE declined by about 380% from nearly 16 kg•kW¹•day-¹ in 1967 to 4 kg•kW-¹•day-¹ in 2010. Shifted baselines were evident in all but two surveyed sectors (i.e., the bottom trawlers of Turkey, and artisanal fishers of South Cyprus). The artisanal and recreational sectors of Turkey experienced the most severe changes, with declines in CPUE of about 40 times since about 1950.

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Marine protected areas: a global exploration of their quantity and quality (2014)

Expansion in the number and extent of marine protected areas (MPAs) has been dramatic during the past century, but coverage remains limited and there are concerns that many MPAs are failing to meet their objectives. After updating the global database of MPAs maintained by the Sea Around Us, new estimates of global marine protected area were calculated and revealed a degree of progress towards protecting at least 10% of the global ocean by 2020. It is estimated that more than 6,000 MPAs covering 3.27% of the world’s oceans (∼11.9 million km²) have been designated to date. The protection these MPAs offer is generally weak with about one-fifth (∼2.2 million km²) of their combined area designated as no-take (i.e., where fishing and other extractive activities are prohibited). Additional large tracts of ocean will need to be protected to reach the 10% target, and hypothetical scenarios for such expansion were investigated. To improve understanding of the likely conservation effectiveness of MPAs, trends in their management effectiveness were explored. Results from a self-administered survey questionnaire, distributed to managers and other experts associated with a random sample of MPAs from around the world, revealed a wide range of MPA management effectiveness across different socioeconomic contexts. The results were intended to inform a model of MPA management effectiveness based on socioeconomic, governance and other contextual variables, but no clear relationships between contextual variables and MPA management effectiveness were identified. Overall, the survey findings confirmed results of other studies: while some MPAs are well supported with funding, staff and equipment, others lack even basic management elements. Additional research is essential to understanding the issues preventing MPAs from meeting their objectives, including effectively contributing to biodiversity conservation.

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Tuna be, or not tuna be: Using catch data to observe the ecological impacts of commercial tuna fishing in the Pacific Ocean at varying spatial scales (2014)

Tuna are arguably the world’s most valuable, versatile, yet vulnerable fishes. With current landings over 4 million tonnes annually, all species of tuna from all three major ocean basins are caught, traded, and consumed at various intensities around the globe. Understanding the implications of such an extensive industry is paramount to protecting the long-term health and sustainability of both the tuna fisheries as well as the ecosystems in which they operate. Given that the Pacific Ocean accounts for roughly two-thirds of the global commercial tuna catch, this thesis assesses the trends and ecological impacts of commercial tuna fishing at both the artisanal and industrial scale in this ocean. To observe the importance of tuna fisheries at a local scale, a case study of the Galápagos Islands is presented. In this context, it was observed that over-fishing and the subsequent depletion of large, low fecund serranids has resulted in a high level of ‘fishing down’ within the near-shore ecosystem. Consequently, as fishers are forced to expand to regions off-shore, tuna and coastal scombrids are becoming increasingly targeted. With regard to industrial fishing, tuna vessels (especially distant-water longliners) are known to generate a substantial amount of associated bycatch and discards. The second component of this thesis quantified the amount of bycatch (retained and discarded) generated by Pacific tuna fishing fleets from 1950 to 2010. Unreported retained bycatch amounted to 1.4 million t; the total discarded catch associated with tuna fishing was 3.6 million t of target species and 7.9 million t of non-target species; sharks were the most commonly discarded species. These totals represent about 14% of the reported landings during this time. Lastly, an analysis of the applicability of the ‘Catch-MSY’ method developed by Martell and Froese (2012) in the context of large pelagic fishes is presented. It was observed that this method produces MSY estimates highly correlated to those produced by complete stock assessments. Collectively, the results of this thesis suggest that the tools to adequately manage tuna exist; however, proper data collection is rare, and the implementation of adequate sustainable fishing measures by fisheries managers is still wanting.

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An analysis of temporal and spatial patterns in global seabird abundance during the modern industrial era (1950-2010) and the relationship between seabird decline and marine fisheries catch (2013)

Seabird populations worldwide are threatened by anthropogenic activities including hunting, introduced predators, habitat destruction, pollution, and fisheries, yet the cumulative effects of these threats on seabird populations is difficult to assess because seabird population studies are mainly limited to small temporal and spatial scales. The present study used global databases of seabird abundance, seabird distribution, and fisheries catch, to estimate global annual seabird population size, overall and by seabird family, 1950-2010; map observed global seabird population change within the same timeframe; and compare temporal and spatial patterns in seabird decline with fisheries, a major threat for which global temporally and spatially explicit data is available throughout the modern industrial era. The global seabird population was estimated to decline by 25% during the modern industrial era, from 1.023 billion individuals in 1950 to 0.768 billion individuals in 2010, and overall decline was observed in eleven of the fourteen seabird families. Maps of observed seabird population change indicated decline covering 90% of the world’s marine surface area, and most severe in the southern temperate and tropical oceans. There was a significant positive relationship between annual seabird decline and annual forage fish catch (a metric of forage fish depletion), as well as between observed seabird decline per spatial cell and year of maximum primary production to support fisheries per marine spatial cell (a metric of the timing of peak ecological footprint of fisheries), both indicating that fisheries presence may play a role in shaping spatial and temporal patterns in global seabird population change. The present study identifies the temporally, taxonomically and spatially pervasive nature of global seabird decline during the modern industrial era and a potentially globally important role of fisheries in this global seabird decline, thus indicating the need for a large-scale and precautionary approach to seabird and marine ecosystem management.

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Small but Mighty: A Global Reconsideration of Small-Scale Fisheries (2013)

Small-scale (SS) fisheries have sustained people for millennia and are pervasive in coastal communities across the globe. Now, the future of what was once believed to be an endless supply of resources remains uncertain given current conditions. The small-scale fisheries sector employs over 34 million fishers, which is at least 24 times more than industrial fisheries. The vast majority of these small-scale fishers reside in developing countries, and strongly rely on these resources for food security and poverty alleviation. Despite their significance, global marine fisheries have been deeply troubled in recent history due to overfishing and inadequate management practices. It is imperative that policy makers base their decisions on reliable data in order to adequately manage this troubling situation, however, current information regarding the small-scale fisheries sector is dubious at best. After compiling data as to what constitutes a small-scale fishery and the associated catch, by country, a multiple linear regression was used to predict data for countries where none was obtained. Human development index (HDI), inshore fishing area (IFA), and whether or not the data came from the FAO, can be used to explain the variance in catch, and predict catch where countries are missing data. The multiple linear regression in Chapter 3 provided the global SS fisheries catch estimate of 25 million tonnes, which is 19% higher than the previous estimates. It is crucial to note that this catch is almost equivalent to the estimated 29 million tonnes bound for human consumption from the industrial sector. In addition, it was seen that data originating from the FAO underestimates the catch in this sector, which is congruent with qualitative information obtained from the literature search in Chapter 1. Lastly, countries with a low HDI were found to catch more (5.29 t∙km²) per unit area than those that are highly developed (1.76 t∙km²).

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Using Shark Catch Data to Estimate the Magnitude and Global Distribution of the Shark Fin Trade (2012)

China’s economic growth in recent years has led to a rapid increase in shark fin soup consumption, fueling the demand for shark fins and encouraging fishers worldwide to engage in shark finning. Such practices have led to the overfishing and biomass decline of numerous shark species. Globally, shark catches are poorly reported both quantitatively and taxonomically, and legislation to protect sharks is insufficient. Additionally, data on the international trade of shark fins and other shark products are sparse and, when available, lack descriptive details, making effective shark fishery management challenging.In this thesis, shark-related legislation is reviewed on a global scale, and the legitimacy of the 5% wet fin to body weight ratio commonly specified in legislation is examined through an analysis of 50 species-specific wet fin to body weight ratios. Official FAO shark catch statistics were supplemented with outside information, and Best Catch Estimates (BCEs) of mean yearly shark catches were calculated for each EEZ between the years 2000 and 2009. Missing values for EEZs and the High Seas were estimated. Appropriate conversion factors were applied to BCEs to estimate the total weight of dry fins traded yearly. Results indicate that both legislation and official FAO shark catch statistics are inadequate and improved regulation, data collection, and monitoring of shark fisheries is necessary on a global scale.

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A global analysis of historical and projected mariculture production trends, 1950-2030 (2011)

Aquaculture is one of the fastest growing global food animal production industries and, according to the United Nations Food and Agriculture Organization (FAO), accounts for over 40 % of global seafood consumption. This proportion is anticipated to grow in the coming decades as global capture fisheries continue to stagnate and global demand for seafood continues to rise. As the significance of aquaculture grows, the marine and brackish (‘mariculture’) subsector is of particular interest for analysis because of its growing influence on the development of global aquaculture and its known negative impacts on marine biodiversity and coastal health.Based on known global data limitations and past experience with fisheries and aquaculture statistics reported to the FAO, there is reason to independently verify the FAO’s current global database of mariculture production statistics. Moreover, its low spatial and taxonomic resolution can create uncertainties in analysis, management, and planning. We therefore re-estimated and GIS-mapped historical mariculture production from 1950 to 2004 at a higher spatial and taxonomic resolution. Despite this new compilation, some uncertainty remains in the accuracy of reported mariculture production statistics at the country level, particularly in China. As such, mariculture statistics should still be used with caution. Through analysis of mean trophic levels, this new global database confirms that we are globally ‘farming up the foodweb’. This new database was combined with the scenarios framework of the United Nations Global Environmental Outlook (GEO-4) to reduce the uncertainty inherent in planning for, and anticipating the effects of, mariculture production’s global development trajectory by 2030. Based on the GEO-4 framework and a method using segmented linear regressions, we developed four plausible narrative storylines and model-based simulations of future mariculture, emphasizing the benefits and tradeoffs along different pathway of future development. One important result is that taking immediate action towards increasing ecological responsibility in mariculture production and development does not appear to preclude meeting currently projected food fish demand in 2030.

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Effects of global fisheries on the biomass of marine ecosystems: a trophic-level-based approach (2010)

Marine fisheries have been occurring for centuries but the last 50 years have seen a drastic increase in their reach and intensity. Fisheries now impact marine ecosystems worldwide and it is necessary to understand their impact, both historical and current, at this scale. A global perspective provides an efficient inter-disciplinary communication tool and allows to summarize and validate our current understanding of ecosystem functioning. The objectives of this thesis are to generate global estimates of biomass for marine ecosystems and evaluate the effects that fisheries have had on ocean biomass since the 1950s.A simple but versatile ecosystem model was used to represent ecosystems as a function of energy fluxes through trophic levels. Using primary production data, sea surface temperature, fisheries catch and trophic level of species, the model was applied on a half-degree grid covering all oceans.Estimates of biomass by trophic levels were derived for marine ecosystems in an unexploited state, as well as for all decades since the 1950s. Trends in the decline of marine biomass from the unexploited state were analyzed for all oceans, with a special emphasis on predator species since they are highly vulnerable to fishing.This thesis is the first application of a trophic modelling approach to a worldwide estimation of the effects of fishing. It provides an independent confirmation of previous reports by other researchers that were based on proxies of biomass or on meta-analyses of local datasets. The results presented highlight three main trends about the global effects of fishing: (1) predators are more affected than organisms at lower trophic levels; (2) declines in ecosystem biomass are stronger along coastlines than in the High Seas; (3) the extent of fishing and its impacts have expanded from north temperate to equatorial and southern waters in the last 50 years. More specifically, this work shows that many oceans historically exploited by humans have seen a drastic decline in their predator biomass, with about half of the coastal areas of the North Atlantic and North Pacific showing a decline in predator biomass of more than 90%. The spatial and temporal trends presented in this work provide a global synthesis of the effects of fishing on the biomass of marine ecosystems and point to a potential state of the world’s oceans if industrial fisheries maintain their current trajectory.

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