Hunting by humans played a major role in extirpating terrestrial megafauna on several continents and megafaunal loss continues today in both terrestrial and marine ecosystems. Recent declines of ...large marine vertebrates that are of little or no commercial value, such as sea turtles, seabirds and marine mammals, have focused attention on the ecological impacts of incidental take, or bycatch, in global fisheries. In spite of the recognition of the problem of bycatch, few comprehensive assessments of its effects have been conducted. Many vulnerable species live in pelagic habitats, making surveys logistically complex and expensive. Bycatch data are sparse and our understanding of the demography of the affected populations is often rudimentary. These factors, combined with the large spatial scales that pelagic vertebrates and fishing fleets cover, make accurate and timely bycatch assessments difficult. Here, we review the current research that addresses these challenging questions in the face of uncertainty, analytical limitations and mounting conservation crises.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Recent case studies have highlighted high bycatch mortality of sea turtles and marine mammals in artisanal fisheries, but in most countries there are few data on artisanal fishing effort, catch, or ...bycatch. With artisanal fisheries comprising >95% of the world’s fishermen, this knowledge gap presents a major challenge to threatened species conservation and sustainable fisheries initiatives. We report on results from an intensive pilot study to evaluate whether interview surveys can be effective in assessing fishing effort and threatened species bycatch. Fisheries and bycatch data from interviews with >6100 fishermen in seven developing countries were collected in <1
year for approximately USD $47,000, indicating that this approach may rapidly yield coarse-level information over large areas at low cost. This effort provided the first fisheries characterizations for many areas and revealed the widespread nature of high bycatch in artisanal fisheries. Challenges to study design and implementation prevented quantitative estimation or spatial comparisons of bycatch during this pilot research phase, but results suggested that annual sea turtle bycatch may number at least in the low thousands of individuals per country. Annual odontocete bycatch may number at least in the low hundreds per country. Sirenian bycatch occurred in all study areas but was frequent only in West Africa. We discuss lessons learned from this survey effort and present a revised protocol for future interview-based bycatch assessments.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Fishers, scientists, and resource managers have made substantial progress in reducing bycatch of sea turtles, seabirds, and marine mammals through physical modifications to fishing gear. Many ...bycatch-avoidance measures have been developed and tested successfully in controlled experiments, which have led to regulated implementation of modified or new fishing gear. Nevertheless, successful bycatch experiments may not translate to effective mitigation in commercial fisheries because experimental conditions are relaxed in commercial fishing operations. Such a difference between experimental results and real-world results with fishing fleets may have serious consequences for management and conservation of protected species taken as bycatch. We evaluated preimplementation experimental measures and postimplementation efficacy from primary and gray literature for three case studies: acoustic pingers that warn marine mammals of the presence of gill nets, turtle excluder devices that reduce bycatch of turtles in trawls, and various measures to reduce seabird bycatch in longlines. Three common themes to successful implementation of bycatch reduction measures are long-standing collaborations among the fishing industry, scientists, and resource managers; pre- and postimplementation monitoring; and compliance via enforcement and incentives.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NMLJ, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
Over the past 3 decades, the status of sea turtles and the need for their protection to aid population recovery have increasingly captured the interest of government agencies, non-governmental ...organisations (NGOs) and the general public worldwide. This interest has been matched by increased research attention, focusing on a wide variety of topics relating to sea turtle biology and ecology, together with the interrelations of sea turtles with the physical and natural environments. Although sea turtles have been better studied than most other marine fauna, management actions and their evaluation are often hindered by the lack of data on turtle biology, human-turtle interactions, turtle population status and threats. In an effort to inform effective sea turtle conservation a list of priority research questions was assembled based on the opinions of 35 sea turtle researchers from 13 nations working in fields related to turtle biology and/or conservation. The combined experience of the contributing researchers spanned the globe as well as many relevant disciplines involved in conservation research. An initial list of more than 200 questions gathered from respondents was condensed into 20 metaquestions and classified under 5 categories: reproductive biology, biogeography, population ecology, threats and conservation strategies.
Seabirds are facing a growing number of threats in both terrestrial and marine habitats, and many populations have experienced dramatic changes over past decades. Years of seabird research have ...improved our understanding of seabird populations and provided a broader understanding of marine ecological processes. In an effort to encourage future research and guide seabird conservation science, seabird researchers from 9 nations identified the 20 highest priority research questions and organized these into 6 general categories: (1) population dynamics, (2) spatial ecology, (3) tropho-dynamics, (4) fisheries interactions, (5) response to global change, and (6) management of anthropogenic impacts (focusing on invasive species, contaminants and protected areas). For each category, we provide an assessment of the current approaches, challenges and future directions. While this is not an exhaustive list of all research needed to address the myriad conservation challenges seabirds face, the results of this effort represent an important synthesis of current expert opinion across sub-disciplines within seabird ecology. As this synthesis highlights, research, in conjunction with direct management, education, and community engagement, can play an important role in facilitating the conservation and management of seabird populations and of the ocean ecosystems on which they and we depend.
Read the Feature Paper: Estimates of seabird incidental catch by pelagic longline fisheries in the South Atlantic Ocean
Other Commentaries on this paper: Next step for reducing seabird bycatch; ...Requisite improvements to the estimation of seabird by‐catch in pelagic longline fisheries
Response from the authors: Incidental catch of seabirds: strengthening observer programs and increasing cooperation
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The depletion of fish stocks from global fisheries has been a long‐standing concern. More recently, incidental catch of non‐target (termed bycatch) vertebrates also has been proposed as a serious ...conservation issue. Here we present a bycatch assessment for loggerhead and leatherback sea turtles that are incidentally caught by global pelagic longlines. We integrate catch data from over 40 nations and bycatch data from 13 international observer programmes. Despite infrequent rates of encounter, our analyses show that more than 200 000 loggerheads and 50 000 leatherbacks were likely taken as pelagic longline bycatch in 2000. Our analyses suggest that thousands of these turtles die each year from longline gear in the Pacific Ocean alone. Given 80–95% declines for Pacific loggerhead and leatherback populations over the last 20 years, this bycatch level is not sustainable. Adopting a large‐scale, synthetic approach is critical to accurately characterize the influence of global fisheries bycatch on globally distributed and imperilled pelagic vertebrates.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The diet of African hippopotamids can be documented through stable carbon isotope ratios (¹³C/¹²C) analyses of enamel and other tissues. The common hippopotamus Hippopotamus amphibius is widely ...assumed to be a pure grazer; however, the ¹³C/¹²C ratios of modern H. amphibius show a higher fraction of dietary C₃ biomass than estimated from traditional observations. Isotope profiles of modern hair and modern tooth enamel confirm that H. amphibius has a variable diet in both the short- (seasonal) and long- (sub-decadal) time scales. Isotopic analyses of extant mammals from the same parks as the analyzed hippos provide comparative examples for diets of C₃-browsers and C₄-grazers. Oxygen isotope ratios (¹⁸O/¹⁶O) show that the hippo is consistently the most ¹⁸O-depleted mammal in any one ecosystem; this directly reflects its semi-aquatic habitat.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
Minimizing fisheries bycatch, the incidental capture of non-target species, is a global environmental challenge. In many regions, bycatch of imperiled species is one of a number of issues that ...threatens species viability and impedes the development of sustainable fisheries. effectively
addressing bycatch of species of conservation concern and improving fisheries sustainability require cross-sectoral integration of information on the biological, socioeconomic, and political contexts of each fishery. several gaps present simultaneous challenges, including: limited engagement
with fisher communities, a lack of data, a need for more robust analyses of available data, and a need for coordinated governance from local to global scales. here we present a framework to address fisheries bycatch that builds on established methods in community collaboration and engagement,
field-based interviews, quantitative bycatch analyses, and ocean policy governance. although these individual approaches to reduce bycatch are well established, there has yet to be a comprehensive application of an integrated approach. We review these essential approaches and present a broadly
applicable model for their integration.
Fisheries bycatch threatens populations of marine megafauna such as marine mammals, turtles, seabirds, sharks and rays, but fisheries impacts on non-target populations are often difficult to assess ...due to factors such as data limitation, poorly defined management objectives and lack of quantitative bycatch reduction targets. Limit reference points can be used to address these issues and thereby facilitate adoption and implementation of mitigation efforts. Reference points based on catch data and life history analysis can identify sustainability limits for bycatch with respect to defined population goals even when data are quite limited. This can expedite assessments for large numbers of species and enable prioritization of management actions based on mitigation urgency and efficacy. This paper reviews limit reference point estimators for marine megafauna bycatch, with the aim of highlighting their utility in fisheries management and promoting best practices for use. Different estimators share a common basic structure that can be flexibly applied to different contexts depending on species life history and available data types. Information on demographic vital rates and abundance is required; of these, abundance is the most data-dependent and thus most limiting factor for application. There are different approaches for handling management risk stemming from uncertainty in reference point and bycatch estimates. Risk tolerance can be incorporated explicitly into the reference point estimator itself, or probability distributions may be used to describe uncertainties in bycatch and reference point estimates, and risk tolerance may guide how those are factored into the management process. Either approach requires simulation-based performance testing such as management strategy evaluation to ensure that management objectives can be achieved. Factoring potential sources of bias into such evaluations is critical. This paper reviews the technical, operational, and political challenges to widespread application of reference points for management of marine megafauna bycatch, while emphasizing the importance of developing assessment frameworks that can facilitate sustainable fishing practices.
Full text
Available for:
BFBNIB, NUK, PNG, UL, UM, UPUK
PDF
