Human-induced Mortality Research Articles

Human-Induced Mortality Causes Affecting a Newly Established Population of Ospreys Pandion haliaetus in Southern Iberia

Human-Induced Mortality Causes Affecting a Newly Established Population of Ospreys Pandion haliaetus in Southern Iberia

The Recolonisation of the Piketberg Leopard Population: A Model for Human–Wildlife Coexistence in a Changing Landscape

Important metapopulation dynamics are disrupted by factors such as habitat loss, climate change, and human-induced mortality, culminating in isolated wildlife populations and threatening species survival. Source populations, where birth rates exceed mortality and connectivity facilitates dispersal, contrast with sink populations, where mortality outstrips births, risking localised extinction. Recolonisation by individuals from source populations is pivotal for species survival. The leopard is the last free-roaming apex predator in South Africa and plays an important ecological role. In the Eastern and Western Cape provinces in South Africa, leopard populations have low densities and fragmented population structures. We identified a leopard population that, after being locally extinct for a century, appeared to recolonise an ‘island’ of mountainous habitat. We aimed to understand potential factors driving this recolonisation using recent camera trapping surveys and historical statutory destruction permits. We employed spatially explicit capture–recapture (SECR) methods to estimate the leopard density and explore potential factors which best explain density. We found that the recently recolonised Piketberg population now exhibits some of the highest densities reported in the region (~1.8 leopards/100 km2; CI 1.4–2.5). Livestock, human presence, elevation, and the camera trap grid appeared to explain leopard detection rates. When considering the historic data, the re-emergence of leopards in the Piketberg coincided with the cessation of the extensive state-sponsored and state-enabled culling of the species, and the change in land use from livestock production to crop agriculture, which likely contributed to the recolonisation. Elucidating these factors deepens our understanding of leopard metapopulation dynamics in relation to land use and species management and highlights the crucial role of private land and state agencies and associated policies in species persistence.

Tracking data highlight the importance of human-induced mortality for large migratory birds at a flyway scale

Human-induced direct mortality affects huge numbers of birds each year, threatening hundreds of species worldwide. Tracking technologies can be an important tool to investigate temporal and spatial patterns of bird mortality as well as their drivers. We compiled 1704 mortality records from tracking studies across the African-Eurasian flyway for 45 species, including raptors, storks, and cranes, covering the period from 2003 to 2021. Our results show a higher frequency of human-induced causes of mortality than natural causes across taxonomic groups, geographical areas, and age classes. Moreover, we found that the frequency of human-induced mortality remained stable over the study period. From the human-induced mortality events with a known cause (n = 637), three main causes were identified: electrocution (40.5 %), illegal killing (21.7 %), and poisoning (16.3 %). Additionally, combined energy infrastructure-related mortality (i.e., electrocution, power line collision, and wind-farm collision) represented 49 % of all human-induced mortality events. Using a random forest model, the main predictors of human-induced mortality were found to be taxonomic group, geographic location (latitude and longitude), and human footprint index value at the location of mortality. Despite conservation efforts, human drivers of bird mortality in the African-Eurasian flyway do not appear to have declined over the last 15 years for the studied group of species. Results suggest that stronger conservation actions to address these threats across the flyway can reduce their impacts on species. In particular, projected future development of energy infrastructure is a representative example where application of planning, operation, and mitigation measures can enhance bird conservation.

On the elephant trails: habitat suitability and connectivity for Asian elephants in eastern Indian landscape.

Identifying suitable habitats and conserving corridors are crucial to the long-term conservation of large and conflict-prone animals. Being a flagship species, survival of Asian elephants is threatened by human-induced mortality and habitat modification. We aimed to assess the habitat suitability and connectivity of the Asian elephant Elephas maximus Linnaeus, 1758 habitat in the state of Odisha in eastern India. We followed the ensemble of spatial prediction models using species presence data and five environmental variables. We used least-cost path and circuit theory approaches to identify the spatial connectivity between core habitats for Asian elephants. The results revealed that normalized difference vegetation index (NDVI; variable importance 42%) and terrain ruggedness (19%) are the most influential variables for predicting habitat suitability of species within the study area. Our habitat suitability map estimated 14.6% of Odisha's geographical area (c. 22,442 km2) as highly suitable and 13.3% (c. 20,464 km2) as moderate highly suitable. We identified 58 potential linkages to maintain the habitat connectivity across study area. Furthermore, we identified pinch points, bottlenecks, and high centrality links between core habitats. Our study offers management implications for long-term landscape conservation for Asian elephants in Odisha and highlights priority zones that can help maintain spatial links between elephant habitats.

A necropsy of negative human-puma interaction in the high Andes: Are pumas in poor body condition more likely to attack livestock?

Globally, it is not yet clear whether particular individuals of apex predators with specific body conditions are more likely to attack livestock. In the Andes, attacks on livestock by pumas (Puma concolor) represent a recurring problem that, consequently, leads to the persecution and lethal removal of this predator by ranchers. However, although the anthropic motivations that lead to the lethal removal of pumas are known, the body conditions of the individuals that attack livestock are still unknown. From 2015 to 2016, three pumas were killed by ranchers after attacks on livestock in the department of Cuzco, at an average elevation of 4415 m, in southeastern Peru. The necropsy of these individuals revealed that they were all deviating from normal health and body conditions (cachexia, tarsal fracture, teeth problems and unusual stomach content). Although based on only three individuals, our findings allow us to hypothesize that these individuals did not meet the necessary body conditions for hunting wild prey. This could increase their states of hunger and lead them to forage in livestock landscapes, which in turn could serve as auxiliary foraging sites with more energetically profitable prey. We consider it essential to develop further research efforts to understand what ecological conditions cause pumas to be more vulnerable to human-induced mortality. This information is essential to further understand the characteristics of the ecological niche of these large predators in current anthropic contexts and, therefore, to direct coherent conservation strategies.

Long-Term Changes in a Pygmy Cormorant Microcarbo pygmaeus Wintering Population in Southern Bulgaria

Waterbirds are declining globally due to different threats that affect their abundance and shift both their breeding and wintering ranges. Cormorants disperse over vast distances during winter and are suitable indicators of the impacts of human-wildlife interactions and abiotic factors. During wintering periods, Pygmy Cormorants Microcarbo pygmaeus use regular roosts where they overnight on suitable perches, a refuge from adverse weather conditions and disturbances. Our study aimed to determine the wintering population size of the Pygmy Cormorant and its dynamics across 23-years (1996–2019) at seven roosting sites in the Maritsa River valley, Southern Bulgaria. This is a critical site for the species conservation where 3065–8180 birds are wintering annually. The wintering Pygmy Cormorant population showed a tendency to increase between 1996 and 2019 (λ = 1.03 ± 0.001). Each year Pygmy Cormorants were most abundant in December (mean ± SE, 2609 ± 185 individuals), while the lowest numbers were recorded in March (1207 ± 106). Pygmy Cormorants aggregated to roost between 4:00 PM and 5:30 PM throughout the study. The area of wintering foraging habitat of the Pygmy Cormorant increased significantly across all roosting sites in the study period from 2675.97 ha to 22564.35 ha. The number of Pygmy Cormorants at the roost was positively affected by the drop in the daily air mean temperatures and the decrease of the day length. Despite the global population increase, the Pygmy Cormorant faces a high risk of human-induced mortality during wintering and is thus regionally classified as endangered.

Characterising an interaction between coastal bottlenose dolphins (Tursiops truncatus) and the spot gillnet fishery in southeastern North Carolina, USA

The aim of this study was to characterise interactions between coastal bottlenose dolphins (Tursiops truncatus Montagu, 1821), and the autumn gillnet fishery in southeastern North Carolina, USA that targets spot (Leiostomus xanthurus). Beach based (conducted from April 1997 - January 1998) and aerial surveys (conducted from July 1998 - May 1999) were used to estimate the abundance of dolphins and gillnets in nearshore waters. Commercial spot landings records from Brunswick County, North Carolina were used as an index of prey abundance. Stranded bottlenose dolphins were evaluated using protocols developed to describe diagnostic evidence of human-induced fisheries mortality. During both survey periods, dolphin numbers, gillnet numbers and spot landings all peaked in October-November. Simultaneously, an increase in dolphin strandings bearing evidence of entanglement in gillnets (cuts, lacerations, or wrapping marks on their appendages) was observed. Four stranded dolphins were determined to have been killed in gillnets, and one dolphin was removed alive from a gillnet in October 1997. Six stranded dolphins were killed in gillnets in October and November 1998. Thus, 20-24% of the annual allowable human-induced mortality for all USA Atlantic coastal bottlenose dolphins could be attributed to monofilament gillnets targeting spot in October and November in southeastern North Carolina. Both recreational and commercial fishermen target spot in the autumn using gillnets and dolphin mortality may be attributable to both aspects of the fishery. Results of this study are cause for alarm because interactions between dolphins and coastal gillnets may be occurring at much larger spatial and temporal scales along the USA Atlantic coast. Understanding the relationships between the biological and anthropogenic variables leading to these interactions can facilitate conservative, pro-active, management ensuring that human-induced mortality is not negatively impacting populations of marine mammals, such as Atlantic coastal bottlenose dolphins.

Limitations of hypothesis-testing in defining management units for continuously distributed species

Estimating the risk to wildlife populations resulting from human-induced mortality relies on adequately defining population structure. For marine populations, including cetaceans, identifying population boundaries is difficult because most species have large continuous distributions with no obvious barriers to dispersal. For many species, the extreme ends of the range differ in morphology, indicating that population structure exists. However, the lack of distributional hiatuses often makes this structure difficult to detect. A common method of defining structure in such situations is to use genetic differentiation as a proxy for limited movement between areas. Genetic analyses of population structure usually take the form of hypothesis testing, which requires the a priori definition of hypothesised units and testing for significant genetic differentiation between them. Simulations are used to examine the performance of hypothesis testing to correctly define population structure. Results show that hypothesis testing is likely to lead the researcher to define fewer management units than are necessary to adequately protect local populations from over-exploitation. The need for the development of new methods of defining management units and for rigorous performance testing of all methods applied in a management context is highlighted.

Survival and cause-specific mortality of coyotes in Wisconsin

Abstract Understanding the drivers of population dynamics informs management actions and assures the public that harvest activities are not detrimental to the long-term stability of wildlife populations. We examined the survival and cause-specific mortality of 66 adult coyotes (34 males, 32 females) using GPS radiotelemetry in southwestern Wisconsin during October 2016 to March 2020. We paired our study with a literature review of coyote survival and mortality across the United States and Canada, focusing on the geographical distribution of studies, demographic aspects of survival, and the level of exploitation by humans on coyote populations. In Wisconsin, annual survival did not differ between sexes or across years but did vary among seasons and social statuses. The relative risk for a coyote dying was higher during the winter compared to the summer. A transient coyote had a higher relative risk of mortality compared to a resident coyote. Mean annual survival probability (sexes combined) was higher for a year-long resident compared to a year-long transient. The predominant sources of known mortality (n = 37) were harvest (83.8%) and vehicle collisions (13.5%). For our literature review, we identified 56 studies estimating coyote survival or mortality from 1971 to 2021 spanning the geographic range of coyotes. We found no distinct temporal or regional patterns in survival probability or the proportion of human-induced mortality, although fewer studies originated from the northeast region of the United States. Additionally, we detected weak correlation between survival probability and proportion of human-induced mortality, suggesting coyote harvest may be compensatory. Although our findings indicate that the Wisconsin coyote population had relatively higher human-induced mortality than populations in other regions, these mortality rates appear to be sustainable for this population under current landscape and habitat conditions.

Trends in bottlenose dolphin (Tursiops truncatus) strandings in South Carolina, USA, 1997-2003: implications for the Southern North Carolina and South Carolina Management Units

Trends in marine mammal stranding rates over multiple years can provide useful information on life history parameters, seasonal and spatial distribution and both natural and human-induced mortality rates when compared with baseline data. Data of bottlenose dolphin (Tursiops truncatus) stranding rates in South Carolina, USA from 1997-2003 were analysed. The objectives of this study were to: (1) compare recent trends in strandings with baseline data (1992-1996) for South Carolina; (2) compare strandings between the Southern North Carolina Management Unit (SNCMU) and the South Carolina Management Unit (SCMU); (3) determine annual, seasonal and spatial trends in bottlenose dolphin strandings; (4) investigate seasonal reproductive trends; and (5) determine the extent to which humans may affect stranding rates (human interactions). Bottlenose dolphins stranded in South Carolina are assumed to be from at least two of the seven management units recognised by the National Marine Fisheries Service in the Western North Atlantic: the SNCMU and the SCMU. During the study period, 302 bottlenose dolphin strandings were reported in South Carolina and stranding counts were analysed using a Generalised Linear Model. Results showed that there were significantly more bottlenose dolphin strandings in the spring and autumn as compared with summer and winter. The effect of season was highly significant for the number of neonate strandings, suggesting a bimodal reproductive cycle in spring and autumn for the study area. A significant increase in the number of strandings of all age classes was found in the autumn for the northern portion of the State (SNCMU), supporting the assumption that bottlenose dolphins from the north migrate into South Carolina waters during this time of year. Rope entanglements was the most common source of human interaction, with the crab pot fishery the most prevalent source of fishery mortality in South Carolina. This study demonstrates the usefulness of a long-term stranding database by increasing knowledge of temporal and spatial patterns and for monitoring neonate and human-induced mortality.

Pacific Salmon Strategy Initiative will conserve marine birds with fishery closures and gillnet license retirements

Due to their lack of selectivity, entanglement of marine birds, along with a wide range of other species, in gillnets is a conservation issue worldwide. In Pacific Canada, mortality from incidental take in salmon gillnet fisheries has been identified as one of the largest sources of human-induced mortality for marine diving birds, a conservation concern impacting both local breeders and visiting migrants. In 2021, to address historic declines in Pacific salmon populations, Fisheries and Oceans Canada introduced the Pacific Salmon Strategy Initiative (PSSI). The PSSI is transformative and includes long-term commercial closures and a license retirement program. The PSSI will move the fishery away from gillnets towards more selective fishing methods with lower release mortality of non-target salmon species. Gillnet fishery closures and license retirements related to new policies under the PSSI will reduce entanglement mortality of migratory marine birds and species at risk from Canada and elsewhere, as a significant conservation byproduct. Closures and license retirements are the most effective tools to reduce bird entanglement mortality in gillnets because of the lack of technical solutions to reduce bycatch and the challenges to fund and develop robust, long-term, interdepartmental monitoring programs to inform the management of incidental take.

Human-induced mortality an overlooked threat for raptors in Nepal

Summary Raptors play a unique role in ecosystem services and are regarded as effective indicators of ecosystem health. In recent years, varieties of anthropogenic factors have threatened the majority of raptor species worldwide. Nepal is considered a global hotspot for threatened and declining raptor species, but there is limited information on the direct human threats to the raptor populations living in the country. In this paper, we identify important anthropogenic threats to raptors in Nepal based on raptor mortality data collected by powerline surveys and from monitoring of GPS-tagged raptors, complete various reports, and social media. We found that powerlines, poisoning, and persecution, mainly shooting, are significant threats to raptors in Nepal that were largely overlooked previously. We report 54 electrocuted raptors affecting eight species, 310 poisoned raptors of 11 species, and five persecuted raptors of four species; among them vultures are the most affected (>88%). Based on our findings, to safeguard the future of Nepal’s raptors, we propose the retrofitting of power poles and the use of flight diverters on powerlines in the most affected areas to reduce raptor interactions with powerlines, as well as an effective conservation education programme to prevent the use of unintentional poisoning.

Dispersal Movements and Hot Spot Areas of Juvenile Bonelli’s Eagles on the Island of Crete, Greece

The Bonelli’s Eagle (Aquila fasciata) is the main avian predator in almost all the islands of the Greek archipelagos. The phase of its natal dispersal has never been studied in Greece, though it constitutes a crucial part of the species ecology and conservation. In an effort to investigate the movement patterns and settlement areas of young eagles, we tagged 30 fledglings on the island of Crete during 2019–2023 with GPS/GSM transmitters. Fledging date was set the first day with full satellite coverage and consecutive GPS fixes for individual birds while the initiation of the dispersal period was established when they performed consecutive long flights, overstaying away from their natal territory (>10 km). Mean fledgling date was calculated at May 27 (range = 20/5–8/6), whereas the dispersal period started on average on September 03 (range = 30/8–21/9), namely ca. 90–100 days after the abandonment of the nest. All juvenile birds wandered around over the entire island residing primarily in two distinct habitat types i.e. coastal cliffs and satellite islets around Crete and agricultural areas in the lowlands covered with olive groves and vineyards. Preliminary surveys show that the juvenile birds avoid active Bonelli’s Eagle territories and select rural areas near landfills, water reservoirs, fowl pens, and uninhabited islets, specializing on prey species that are readily available (i.e. gulls, corvids, rock pigeons, wild rabbits and poultry). This fact makes them particularly susceptible to human-induced mortality such as electrocution, drowning in open water tanks and poaching, which accounted for ca. 60% of the casualties of this age group. Overall, the study confirms that land use changes and human pressure are the major threats for the species on Crete, likewise in the rest of its distribution range in the Mediterranean.

Stay home, stay safe? High habitat suitability and environmental connectivity increases road mortality in a colonizing mesocarnivore

ContextAnthropogenic structures have considerable effects on ecosystems, disrupting natural population processes and representing a serious risk in terms of vehicle collisions. The golden jackal (Canis aureus) is a mesocarnivore species whose range is expanding in Europe. Roadkills are one of the main human-induced mortalities in Italy to the species.ObjectivesIdentify road-related characteristics and ecological factors related to golden jackal roadkill risk in Italy.MethodsWe used habitat suitability (Maxent) and connectivity (Circuit theory) models to derive 15 metrics potentially affecting roadkill risk. We tested their influence using Bayesian generalized linear models and generalized linear models comparing golden jackal roadkill locations to random locations. Furthermore, we tested if there were significant sex, age-related and seasonal differences among road-killed individuals.ResultsWe found that roadkill risk was higher in areas characterized by higher values of habitat suitability and connectivity, habitat fragmentation and along highways. It was lower with increasing distance to the source population and in the presence of guardrails. No significant differences were detected in terms of roadkill risk between sexes, age classes and seasonConclusionsThe identified factors affecting road mortality of golden jackals in Italy provide insights on how to mitigate wildlife-vehicle collisions. Crossing areas, and visual and acoustic warnings for wildlife, as well as the importance of managing fences along high traffic volume roads could help mitigate further damage. Finally, there is a need to further investigate the effectiveness of mitigation measures in the light of the golden jackal’s ongoing expansion in a human-modified landscape.

Exploring the Use of Seabirds as a Dynamic Ocean Management Tool to Mitigate Anthropogenic Risk to Large Whales

Vessel strike and entanglement in fishing gear are global threats to large whales. United States management actions to reduce human-induced serious injury and mortality to large whales have been inadequate, partially due to static, spatial protection schemes that fail to adjust to distribution shifts of highly mobile animals. Whale conservation would benefit from dynamic ocean management, but few tools exist to inform dynamic approaches. Seabirds are often found in association with whales and can be tagged at lower cost and in higher numbers than whales. We explored the use of satellite-tagged seabirds (great shearwaters) as dynamic ocean management tools for near real-time identification of habitats where humpback and North Atlantic right whales aggregate, potentially increasing anthropogenic risk. We identified shearwater habitat use areas in the Gulf of Maine with 50% kernel density utilization distributions at yearly, monthly, and weekly scales using satellite-telemetry data from 2013-2018. We quantified overlap using whale sightings and whale satellite telemetry data at two spatial scales: Stellwagen Bank National Marine Sanctuary and the Gulf of Maine. Within the sanctuary, shearwaters overlapped with >50% of humpback sightings in 4 of 6 (67%) years, 15 of 23 (65%) months, and 50 of 89 (56%) of weeks. At the Gulf of Maine scale, shearwater use areas overlapped >50% of humpback sightings in 5 of 6 years (83%) and 16 of 22 (73%) months, and encompassed humpback 50% utilization distributions (based on satellite telemetry) in 2 of 3 (66%) years and 7/12 (58%) months analyzed. Overlap between shearwaters and right whales was much lower, with >50% overlap in only 1 of 6 (17%) years and 3 of 23 (13%) months. These initial results demonstrate that satellite-tagged shearwaters can be indicators of humpback whale habitat use in both space and time. With further study, tagged shearwaters may provide near-real time information necessary to operationalize dynamic management to mitigate human impacts on humpback whales.

Translocation in relict shy-selected animal populations: Program success versus prevention of wildlife-human conflict

Past human persecution of wildlife has acted as a major selection agent shaping many animal features including behaviour. A major component of behaviour with diverse consequences for conservation is the shyness/boldness continuum. Shyer individuals are often geographically restricted, less prone to wander out of their ecological refuges but, on the contrary, less likely to experience human-induced mortality and lead to human-wildlife conflict. In this essay we discuss how the success of translocations may interact both positively and negatively with animal personalities, based on several case studies of re-introductions and reinforcements involving remnant mammal and bird populations. Although shyness may be inconvenient to conservationists when dealing with raptor translocations in which eventual dispersal may be a desired trait in the long run, a trade-off may emerge between boldness and prevention of human-wildlife conflict when dealing with large carnivores. Some other trade-offs may also occur, such as that between boldness and desired philopatry at the initial stage of re-introductions.

Potential risk zone for anthropogenic mortality of carnivores in Gandaki Province, Nepal.

Anthropogenic pressures in human‐dominated landscapes often contribute to wildlife mortality. Carnivores are especially vulnerable to human‐induced mortality due to the perceived threat to livestock and humans. Despite having widespread conservation implications, carnivore mortality data have been largely underutilized within Nepal. This study utilized Maxent to identify high‐risk areas and explore the contribution of habitat attributes associated with carnivore mortality using the casualty database within the Gandaki province of central Nepal. We categorized the risk to carnivore species in three taxonomic groups, Felid, Viverridae, and Herpestidae, and identified a 3704‐km2 area within the province at high risk for carnivore casualty. The middle mountains were the riskiest physiographic zone, and the Annapurna Conservation Area represented the largest risk zone among the four protected areas. Agricultural land was the most problematic area in terms of carnivore casualty. The human population was positively associated with high‐risk areas and the number of casualties, whereas protected area cover had a negative association. This study identified that the common leopard was at the highest risk of mortality and therefore would benefit from the implementation of an action plan and species‐specific conservation strategies, especially within identified high‐risk zones. An expansion of protected areas in the middle mountain region would serve to greatly reduce carnivore casualty. Species distribution modeling can be further used with national‐level spatial and temporal mortality data to identify the most prominent casualty times and pinpoint potential casualty locations throughout the country.

Multi-seasonal systematic camera-trapping reveals fluctuating densities and high turnover rates of Carpathian lynx on the western edge of its native range

Camera-trapping and capture-recapture models are the most widely used tools for estimating densities of wild felids that have unique coat patterns, such as Eurasian lynx. However, studies dealing with this species are predominantly on a short-term basis and our knowledge of temporal trends and population persistence is still scarce. By using systematic camera-trapping and spatial capture-recapture models, we estimated lynx densities and evaluated density fluctuations, apparent survival, transition rate and individual's turnover during five consecutive seasons at three different sites situated in the Czech–Slovak–Polish borderland at the periphery of the Western Carpathians. Our density estimates vary between 0.26 and 1.85 lynx/100 km2 suitable habitat and represent the lowest and the highest lynx densities reported from the Carpathians. We recorded 1.5–4.1-fold changes in asynchronous fluctuated densities among all study sites and seasons. Furthermore, we detected high individual’s turnover (on average 46.3 ± 8.06% in all independent lynx and 37.6 ± 4.22% in adults) as well as low persistence of adults (only 3 out of 29 individuals detected in all seasons). The overall apparent survival rate was 0.63 ± 0.055 and overall transition rate between sites was 0.03 ± 0.019. Transition rate of males was significantly higher than in females, suggesting male-biased dispersal and female philopatry. Fluctuating densities and high turnover rates, in combination with documented lynx mortality, indicate that the population in our region faces several human-induced mortalities, such as poaching or lynx-vehicle collisions. These factors might restrict population growth and limit the dispersion of lynx to other subsequent areas, thus undermining the favourable conservation status of the Carpathian population. Moreover, our study demonstrates that long-term camera-trapping surveys are needed for evaluation of population trends and for reliable estimates of demographic parameters of wild territorial felids, and can be further used for establishing successful management and conservation measures.

Modelling entanglement rates to estimate mortality of marine birds in British Columbia commercial salmon gillnet fisheries

Incidental mortality of marine birds in fisheries is an international conservation concern, including in Canada where globally significant populations of vulnerable diving species overlap with coastal gillnet fisheries. In British Columbia (BC), commercial salmon gillnet fishing effort was historically very high (>200,000 days fished annually in the early 1950's), and although this fishery has declined, over 6,400 days were fished annually in the 2006–2016 decade. Observations of seabird bycatch within the commercial fishery, however, are limited in both scope (comprising <2% of cumulative effort 2001–2016) and in time (being available only from 1995 onwards and only for a small number of areas). Using onboard fishery observer data from commercial, test and experimental fisheries (1995–2016), we developed two models to estimate the number of marine birds captured per set in sockeye (Oncorhynchus nerka) and chum (O. keta) salmon gillnet fisheries employing a Generalized Linear Mixed Modeling (GLMM) approach in a hierarchical Bayesian framework, with observer data post-stratified by fisheries management area and year. Using estimates of total commercial fishing effort (estimated number of sets, 2001–2016) we applied the models to extrapolate annual take for the main bird species (or groups) of interest. Multinomial probability estimates of species composition were calculated based upon a sample of 852 birds identified to species that were associated with sockeye or chum fisheries, enabling estimates (with CIs) of potential numbers of the mostly commonly observed species (common murres (Uria aalge), rhinoceros auklets (Cerorhinca monocerata), and marbled murrelets (Brachyramphus marmoratus)) entangled annually in commercial sockeye and chum salmon gillnet fisheries throughout BC. Conservative estimates of annual losses to entanglement were greatest for common murres (2,846, 95% CI: 2,628–3,047), followed by rhinoceros auklets (641, CI: 549–770) and marbled murrelets (228 CI: 156–346). Populations of all three of these alcids species are currently in decline in BC and entanglement mortality is a conservation concern. Gillnet mortality has been identified as a longstanding threat to marbled murrelet populations, which are recognized as Threatened in the Canada and the United States of America (USA). In addition, 622 (CI: 458–827) birds from 12 other species were estimated to be entangled annually. We conclude that cumulative mortality from incidental take in salmon gillnet fisheries is one of the largest sources of human-induced mortality for marine birds in BC waters, a conservation concern impacting both breeders and visiting migrants.

Disentangling conditional effects of multiple regime shifts on Atlantic cod productivity.

Regime shifts are increasingly prevalent in the ecological literature. However, definitions vary and detection methods are still developing. Here, we employ a novel statistical algorithm based on the Bayesian online change-point detection framework to simultaneously identify shifts in the mean and (or) variance of time series data. We detected multiple regime shifts in long-term (59–154 years) patterns of coastal Norwegian Atlantic cod (>70% decline) and putative drivers of cod productivity: North Atlantic Oscillation (NAO); sea-surface temperature; zooplankton abundance; fishing mortality (F). The consequences of an environmental or climate-related regime shift on cod productivity are accentuated when regime shifts coincide, fishing mortality is high, and populations are small. The analyses suggest that increasing F increasingly sensitized cod in the mid 1970s and late 1990s to regime shifts in NAO, zooplankton abundance, and water temperature. Our work underscores the necessity of accounting for human-induced mortality in regime shift analyses of marine ecosystems.