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116 results for “marine predator”
Perturbation drives changing metapopulation dynamics in a top marine predator
Metapopulation theory assumes a balance between local decays/extinctions and local growth/new colonisations. Here we investigate whether recent population declines across part of the UK harbour seal range represent normal metapopulation dynamics or are indicative of perturbations potentially threatening the metapopulation viability, using 20 years of population trends, location tracking data ( n = 380), and UK-wide, multi-generational population genetic data ( n = 269). First, we use microsatellite data to show that two genetic groups previously identified are distinct metapopulations: northern and southern. Then, we characterize the northern metapopulation dynamics in two different periods, before and after the start of regional declines (pre-/peri-perturbation). We identify source–sink dynamics across the northern metapopulation, with two putative source populations apparently supporting three likely sink populations, and a recent metapopulation-wide disruption of migration coincident with the perturbation. The northern metapopulation appears to be in decay, highlighting that changes in local populations can lead to radical alterations in the overall metapopulation's persistence and dynamics.
Archive data for: Loss of predation risk from apex predators can exacerbate marine tropicalization caused by extreme climatic events
<p>1. Extreme climatic events (ECEs) and predator removal represent some of the most widespread stressors to ecosystems. Though species interactions can alter ecological effects of climate change (and vice versa), it is less understood whether, when, and how predator removal can interact with ECEs to exacerbate their effects. Understanding the circumstances under which such interactions might occur is critical because predator loss is widespread and ECEs can generate rapid phase shifts in ecosystems which can ultimately lead to tropicalization.</p> <p>2. Our goal was to determine whether loss of predation risk may be an important mechanism governing ecosystem responses to extreme events, and whether the effects of such events, such as tropicalization, can occur even when species range shifts do not. Specifically, our goal was to experimentally simulate loss of an apex predator, the tiger shark (<i>Galeocerdo cuvier</i>) effects on a recently damaged seagrass ecosystem of Shark Bay, Australia by applying documented changes to risk sensitive grazing of dugong (<i>Dugong dugon</i>) herbivores. </p> <p>3. Using a 16-month field experiment established in recently disturbed seagrass meadows, we used previous estimates of risk-sensitive dugong foraging behavior to simulate altered risk-sensitive foraging densities and strategies of dugongs consistent with apex predator loss, and tracked seagrass responses to the simulated grazing.</p> <p>4. Grazing treatments targeted and removed tropical seagrasses, which declined. However, like in other mixed-bed habitats where dugongs forage, treatments also incidentally accelerated temperate seagrass losses, revealing that herbivore behavioral changes in response to predator loss can exacerbate ECE effects and promote tropicalization, even without range expansions or introductions of novel species. </p> <p>5. Our results suggest that changes to herbivore behaviors triggered by loss of predation risk can undermine ecological resilience to ECEs, particularly where long lived herbivores are abundant. By implication, ongoing losses of apex predators may combine with increasingly frequent ECEs to amplify climate change impacts across diverse ecosystems and large spatial scales.</p>
Data from: Biogeophysical and physiological processes drive movement patterns in a marine predator
Background: Blue sharks (Prionace glauca) are among the most abundant and widely distributed of oceanic elasmobranchs. Millions are taken annually in pelagic longline fisheries and comprise the highest component of auctioned fin weight in the international shark fin trade. Though studies of blue sharks outnumber those of other large pelagic sharks, the species' complicated and sexually segregated life history still confound current understanding of Atlantic movement patterns. Lack of detailed information regarding movement and vertical behavior continues to limit management efforts that require such data for stock assessment and sustainable catch modeling. Therefore, this study aims to describe behavioral and ecological patterns distinct to aggregating and migrating blue sharks, and compare the findings to existing Atlantic movement models. Results: Data collected from 23 blue sharks instrumented with pop-up satellite archival tags were used in statistical predictive regression models to investigate habitat use during a localized aggregation in the northwest Atlantic, while undergoing seasonal migrations, and with respect to environmental variables. Deployment durations ranged from 4 to 273 days, with sharks inhabiting both productive coastal waters and the open ocean, and exhibiting long-distance seasonal movements exceeding 3700 km. While aggregating on the continental shelf of the northwest Atlantic, blue sharks displayed consistent depth use independent of sex and life stage, and exhibited varied response to environmental (temperature and chlorophyll a) factors. As sharks dispersed from the aggregation site, depth use was influenced by bathymetry, latitude, demography, and presence in the Gulf Stream. Mature females were not observed at the New England tagging site, however, two mature females with recent mating wounds were captured and tagged opportunistically in The Bahamas, one of which migrated to the Mid-Atlantic Ridge. Conclusions: Vertical behaviors displayed by blue sharks varied greatly among locales; depth use off the continental shelf was significantly greater, and individuals exhibited a greater frequency of deep-diving behavior, compared to periods of aggregation on the continental shelf. Sexual segregation was evident, suggesting mature and immature males, and immature females may be subjected to high levels of anthropogenic exploitation in this region during periods of aggregation. Analysis of the spatio-temporal tracks revealed that nine individuals traveled beyond the United States EEZ, including a mature female captured in The Bahamas that migrated to the Mid-Atlantic Ridge. These results reflect and augment existing Atlantic migration models, and highlight the complex, synergistic nature of factors affecting blue shark ecology and the need for a cooperative management approach in the North Atlantic.
Data from: Empirical evidence that large marine predator foraging behavior is consistent with area-restricted search theory
When prey is patchily distributed, predators are expected to spend more time searching for food in proximity of recent prey captures before searching in other areas. This behavior, known as area-restricted search, results in predators remaining localized in areas where prey had been detected previously because of the higher probability of encountering additional prey. However, few studies have tested these predictions on marine species because of the difficulties of observing feeding behavior. In this study, we utilized passive acoustic detections of echolocating dolphins to identify foraging behavior. C-PODs (click train detectors) were deployed for two years with an acoustic recorder attached to the same mooring during the second year. The time series of feeding buzzes, indicative of foraging behavior, revealed that both bottlenose (Tursiops truncatus) and common dolphins (Delphinus delphis) were more likely to stay in the area longer when foraging activity was high at the beginning of the encounter. The probability of foraging was also higher following previous foraging activity. This suggests that dolphins were feeding on spatially patchy prey and previous foraging experience influenced their movement behavior. This is consistent with the predictions of area-restricted search behavior, a nonrandom foraging strategy.
Data from: Size selection by a gape-limited predator of a marine snail: insights into magic traits for speciation
The intertidal snail Littorina saxatilis has repeatedly evolved two parallel ecotypes assumed to be wave adapted and predatory shore crab adapted, but the magnitude and targets of predator-driven selection are unknown. In Spain, a small, wave ecotype with a large aperture from the lower shore and a large, thick-shelled crab ecotype from the upper shore meet in the mid-shore and show partial size-assortative mating. We performed complementary field tethering and laboratory predation experiments; the first set compared the survival of two different size-classes of the crab ecotype while the second compared the same size-class of the two ecotypes. In the first set, the large size-class of the crab ecotype survived significantly better than the small size-class both on the upper shore and in the laboratory. In the second set, the small size-class of the crab ecotype survived substantially better than that of the wave ecotype both on the upper shore and in the laboratory. Shell-breaking predation on tethered snails was almost absent within the lower shore. In the laboratory shore crabs (Pachygrapsus marmoratus) with larger claw heights selected most strongly against the small size-class of the crab ecotype, whereas those with medium claw heights selected most strongly against the thin-shelled wave ecotype. Sexual maturity occurred at a much larger size in the crab ecotype than in the wave ecotype. Our results showed that selection on the upper shore for rapid attainment of a size refuge from this gape-limited predator favors large size, thick shells, and late maturity. Model parameterization showed that size-selective predation restricted to the upper shore resulted in the evolution of the crab ecotype despite gene flow from the wave ecotype snails living on the lower shore. These results on gape-limited predation and previous ones showing size-assortative mating between ecotypes suggest that size may represent a magic trait for the thick-shelled ecotype.
Data from: Robust estimates of a high Ne/N ratio in a top marine predator, southern bluefin tuna
Genetic studies of several marine species with high fecundity have produced "tiny" estimates (≤10−3) of the ratio of effective population size (Ne) to adult census size (N), suggesting that even very large populations might be at genetic risk. A recent study using close-kin mark-recapture methods estimated adult abundance at N ≈ 2 × 106 for southern bluefin tuna (SBT), a highly fecund top predator that supports a lucrative (~$1 billion/year) fishery. We used the same genetic and life history data (almost 13,000 fish collected over 5 years) to generate genetic and demographic estimates of Ne per generation and Nb (effective number of breeders) per year and the Ne/N ratio. Demographic estimates, which accounted for age-specific vital rates, skip breeding, variation in fecundity at age, and persistent individual differences in reproductive success, suggest that Ne/N is >0.1 and perhaps about 0.5. The genetic estimates supported this conclusion. Simulations using true Ne = 5 × 105 (Ne/N = 0.25) produced results statistically consistent with the empirical genetic estimates, whereas simulations using Ne = 2 × 104 (Ne/N = 0.01) did not. Our results show that robust estimates of Ne and Ne/N can be obtained for large populations, provided sufficiently large numbers of individuals and genetic markers are used and temporal replication (here, 5 years of adult and juvenile samples) is sufficient to provide a distribution of estimates. The high estimated Ne/N ratio in SBT is encouraging and suggests that the species will not be compromised by a lack of genetic diversity in responding to environmental change and harvest.
Data from: Predictive modelling of habitat selection by marine predators with respect to the abundance and depth distribution of pelagic prey
1. Understanding the ecological processes that underpin species distribution patterns is a fundamental goal in spatial ecology. However, developing predictive models of habitat use is challenging for species that forage in marine environments, as both predators and prey are often highly mobile and difficult to monitor. Consequently, few studies have developed resource selection functions for marine predators based directly on the abundance and distribution of their prey. 2. We analysed contemporaneous data on the diving locations of two seabird species, the shallow-diving Peruvian Booby (Sula variegata) and deeper diving Guanay Cormorant (Phalacrocorax bougainvilliorum), and the abundance and depth distribution of their main prey, Peruvian anchoveta (Engraulis ringens). Based on this unique data set, we developed resource selection functions to test the hypothesis that the probability of seabird diving behaviour at a given location is a function of the relative abundance of prey in the upper water column. 3. For both species, we show that the probability of diving behaviour is mostly explained by the distribution of prey at shallow depths. While the probability of diving behaviour increases sharply with prey abundance at relatively low levels of abundance, support for including abundance in addition to the depth distribution of prey is weak, suggesting that prey abundance was not a major factor determining the location of diving behaviour during the study period. 4. The study thus highlights the importance of the depth distribution of prey for two species of seabird with different diving capabilities. The results complement previous research that points towards the importance of oceanographic processes that enhance the accessibility of prey to seabirds. The implications are that locations where prey is predictably found at accessible depths may be more important for surface foragers, such as seabirds, than locations where prey is predictably abundant. 5. Analysis of the relative importance of abundance and accessibility is essential for the design and evaluation of effective management responses to reduced prey availability for seabirds and other top predators in marine systems.
Data from: Scale-dependent foraging ecology of a marine top predator modelled using passive acoustic data
1. Understanding which environmental factors drive foraging preferences is critical for the development of effective management measures, but resource use patterns may emerge from processes that occur at different spatial and temporal scales. Direct observations of foraging are also especially challenging in marine predators, but passive acoustic techniques provide opportunities to study the behavior of echolocating species over a range of scales. 2. We used an extensive passive acoustic dataset to investigate the distribution and temporal dynamics of foraging in bottlenose dolphins using the Moray Firth (Scotland, UK). Echolocation buzzes were identified with a mixture model of detected echolocation inter-click intervals, and used as a proxy of foraging activity. A robust modelling approach accounting for autocorrelation in the data was then used to evaluate which environmental factors were associated with the observed dynamics at two different spatial and temporal scales. 3. At a broad scale, foraging varied seasonally, and was also affected by sea-bed slope and shelf-sea fronts. At a finer scale, we identified variation in seasonal use and local interactions with tidal processes. Foraging was best predicted at a daily scale, accounting for site-specificity in the shape of the estimated relationships. 4. This study demonstrates how passive acoustic data can be used to understand foraging ecology in echolocating species, and provides a robust analytical procedure for describing spatio-temporal patterns. Associations between foraging and environmental characteristics varied according to spatial and temporal scale, highlighting the need for a multi-scale approach. Our results indicate that dolphins respond to coarser-scale temporal dynamics, but have a detailed understanding of finer-scale spatial distribution of resources.
Data from: Body-size trends of the extinct giant shark Carcharocles megalodon: a deep-time perspective on marine apex predators
The extinct shark Carcharocles megalodon is one of the largest marine apex predators ever to exist. Nonetheless, little is known about its body-size variations through time and space. Here, we studied the body-size trends of C. megalodon through its temporal and geographic range to better understand its ecology and evolution. Given that this species was the last of the megatooth lineage, a group of species that shows a purported size increase through time, we hypothesized that C. megalodon also displayed this trend, increasing in size over time and reaching its largest size prior to extinction. We found that C. megalodon body-size distribution was left-skewed (suggesting a long-term selective pressure favoring larger individuals), and presented significant geographic variation (possibly as a result of the heterogeneous ecological constraints of this cosmopolitan species) over geologic time. Finally, we found that stasis was the general mode of size evolution of C. megalodon (i.e., no net changes over time), contrasting with the trends of the megatooth lineage and our hypothesis. Given that C. megalodon is a relatively long-lived species with a widely distributed fossil record, we further used this study system to provide a deep-time perspective to the understanding of the body-size trends of marine apex predators. For instance, our results suggest that (1) a selective pressure in predatory sharks for consuming a broader range of prey may favor larger individuals and produce left-skewed distributions on a geologic time scale; (2) body-size variations in cosmopolitan apex marine predators may depend on their interactions with geographically discrete communities; and (3) the inherent characteristics of shark species can produce stable sizes over geologic time, regardless of the size trends of their lineages.
Data from: Ecological opportunities and specializations shaped genetic divergence in a highly mobile marine top predator
Environmental conditions can shape genetic and morphological divergence. Release of new habitats during historical environmental changes was a major driver of evolutionary diversification. Here, forces shaping population structure and ecotype differentiation ('pelagic' and 'coastal') of bottlenose dolphins in the North-east Atlantic were investigated using complementary evolutionary and ecological approaches. Inference of population demographic history using approximate Bayesian computation indicated that coastal populations were likely founded by the Atlantic pelagic population after the Last Glacial Maxima probably as a result of newly available coastal ecological niches. Pelagic dolphins from the Atlantic and the Mediterranean Sea likely diverged during a period of high productivity in the Mediterranean Sea. Genetic differentiation between coastal and pelagic ecotypes may be maintained by niche specializations, as indicated by stable isotope and stomach content analyses, and social behaviour. The two ecotypes were only weakly morphologically segregated in contrast to other parts of the World Ocean. This may be linked to weak contrasts between coastal and pelagic habitats and/or a relatively recent divergence. We suggest that ecological opportunity to specialize is a major driver of genetic and morphological divergence. Combining genetic, ecological and morphological approaches is essential to understanding the population structure of mobile and cryptic species.
Data from: Questioning assumptions of trophic behavior in a broadly ranging marine predator guild
We evaluated whether existing assumptions regarding the trophic ecology of a poorly-studied predator guild, northwest (NW) Atlantic skates (family: Rajidae), were supported across broad geographic scales. Four hypotheses were tested using carbon (δ13C) and nitrogen (δ15N) stable isotope values as metrics of foraging behavior: 1) species exhibit ontogenetic shifts in habitat and thus display a shift in 13C with differential use of the continental shelf; 2) species exhibit ontogenetic prey shifts (i.e., from smaller to larger prey items) and become enriched in 15N; 3) individuals acquire energy from spatially confined local resource pools and exhibit limited displacement; and 4) species exhibit similarly sized and highly overlapping trophic niches. We found someweak evidence for ontogenetic shifts in habitat-use (δ13C) for thorny and little skate and diet (δ15N) for thorny and winter skate and hypothesize that individuals exhibit gradual trophic niche transition, especially in δ15N space, rather than a clear and distinct shift in diet throughout ontogeny. Spatial isoscapes generated for little, thorny, and winter skate, highlighted distinct spatial patterns in isotopic composition across the coastal shelf. For little and thorny skate, patterns mimicked the expected spatial variability in isotopic composition of phytoplankton/POM, suggesting limited displacement and utilization of spatially confined resource pools. Winter skate, however, exhibited a much narrower range of δ13C and δ15N, suggesting individuals may pool resources from a more confined latitudinal range. Although high total trophic niche overlap was observed between some species (e.g., little and thorny skate), sympatric species (e.g., little and winter skate) exhibited potential trophic niche separation. These findings offer new insight into the trophic dynamics of a poorly studied, vulnerable group of predators, and highlight a need to re-examine assumptions pertaining to aspects of their ecology.
Data from: Markov switching autoregressive models for interpreting vertical movement data with application to an endangered marine apex predator
1.Time series of animal movement obtained from bio-loggers are becoming widely used across all taxa. These data are nowadays of high quality, combining high resolution with precision, as the tags are able to collect for longer times and store larger quantities of data. Due to their nature, high-frequency data sequences often pose non-trivial problems in time series analysis: non-linearity, non-Normality, non-stationarity, and long memory. These issues can be tackled by modelling the data sequence as a realization of a stochastic regime switching process. 2. We suggest a novel Markov switching autoregressive model where the hidden Markov chain is non-homogeneous, with time-varying transition probabilities, whose dynamics depend on the dynamics of some contemporary categorical covariates. 3. To illustrate the use of the method, we apply it to the depth profiles of four individuals of flapper skate (Dipturus cf. intermedia) in order to identify swimming behaviours. Individual time series were obtained from data storage tags that recorded pressure every two minutes. The environmental covariates used were lunar phase (a proxy for the spring-neap tidal cycle), lunar cycle, and diel cycle. For all individuals two states (or regimes) were always selected (the autoregressive order was either three or four), representing different regimes of animal activity, i.e., state 1 for resting or horizontal swimming or slow vertical movement; state 2 for fast ascending and descending. The cycle of the four lunar phases was the only environmental covariate that explained the hidden state dynamics in all individuals, whereas lunar cycle was selected for two individuals and diel cycle for one only. 4. The method is an efficient approach to fit one-dimensional tag data using categorical environmental covariates, and to classify the observations into a small number of states representing individual behaviours of tagged individuals.
Data from: Variable sea-ice conditions influence trophic dynamics in an Arctic community of marine top predators
Sea‐ice coverage is a key abiotic driver of annual environmental conditions in Arctic marine ecosystems and could be a major factor affecting seabird trophic dynamics. Using stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) in eggs of thick‐billed murres (Uria lomvia), northern fulmars (Fulmarus glacialis), glaucous gulls (Larus hyperboreus), and black‐legged kittiwakes (Rissa tridactyla), we investigated the trophic ecology of prebreeding seabirds nesting at Prince Leopold Island, Nunavut, and its relationship with sea‐ice conditions. The seabird community of Prince Leopold Island had a broader isotopic niche during lower sea‐ice conditions, thus having a more divergent diet, while the opposite was observed during years with more extensive sea‐ice conditions. Species' trophic position was influenced by sea ice; in years of lower sea‐ice concentration, gulls and kittiwakes foraged at higher trophic levels while the opposite was observed for murres and fulmars. For murres and fulmars over a longer time series, there was no evidence of the effect of sea‐ice concentration on species' isotopic niche. Results suggest a high degree of adaptation in populations of high Arctic species that cope with harsh and unpredictable conditions. Such different responses of the community isotopic niche also show that the effect of variable sea‐ice conditions, despite being subtle at the species level, might have larger implications when considering the trophic ecology of the larger seabird community. Species‐specific responses in foraging patterns, in particular trophic position in relation to sea ice, are critical to understanding effects of ecosystem change predicted for a changing climate.
Data from: Latitudinal variation in ecological opportunity and intraspecific competition indicates differences in niche variability and diet specialization of Arctic marine predators
Individual specialization (IS), where individuals within populations irrespective of age, sex, and body size are either specialized or generalized in terms of resource use, has implications on ecological niches and food web structure. Niche size and degree of IS of near-top trophic-level marine predators have been little studied in polar regions or with latitude. We quantified the large-scale latitudinal variation of population- and individual-level niche size and IS in ringed seals (Pusa hispida) and beluga whales (Delphinapterus leucas) using stable carbon and nitrogen isotope analysis on 379 paired ringed seal liver and muscle samples and 124 paired beluga skin and muscle samples from eight locations ranging from the low to high Arctic. We characterized both within- and between-individual variation in predator niche size at each location as well as accounting for spatial differences in the isotopic ranges of potential prey. Total isotopic niche width (TINW) for populations of ringed seals and beluga decreased with increasing latitude. Higher TINW values were associated with greater ecological opportunity (i.e., prey diversity) in the prey fish community which mainly consists of Capelin (Mallotus villosus) and Sand lance (Ammodytes sp.) at lower latitudes and Arctic cod (Boreogadus saida) at high latitudes. In beluga, their dietary consistency between tissues also known as the within-individual component (WIC) increased in a near 1:1 ratio with TINW (slope = 0.84), suggesting dietary generalization, whereas the slope (0.18) of WIC relative to TINW in ringed seals indicated a high degree of individual specialization in ringed seal populations with higher TINWs. Our findings highlight the differences in TINW and level of IS for ringed seals and beluga relative to latitude as a likely response to large-scale spatial variation in ecological opportunity, suggesting species-specific variation in dietary plasticity to spatial differences in prey resources and environmental conditions in a rapidly changing ecosystem.
Data from: Local forage fish abundance influences foraging effort and offspring condition in an Endangered marine predator
1. Understanding the functional relationship between marine predators and their prey is vital to inform ecosystem-based management. However, collecting concurrent data on predator behaviour and their prey at relevant scales is challenging. Moreover, opportunities to study these relationships in the absence of industrial fishing are extremely rare. 2. We took advantage of an experimental fisheries closure to study how local prey abundance influences foraging success and chick condition of Endangered African penguins Spheniscus demersus in the Benguela Ecosystem. 3. We tracked 75 chick-provisioning penguins with GPS-time-depth devices, measured body condition of 569 chicks, quantified the diet of 83 breeding penguins and conducted 12 forage fish hydro-acoustic surveys within a 20 km radius of Robben Island, South Africa, over three years (2011–2013). Commercial fishing for the penguins' main prey, sardine Sardinops sagax and anchovy Engraulis encrasicolus, was prohibited within this 20 km radius during the study period. 4. Local forage fish abundance explained 60% of the variation in time spent diving for 14 penguins at sea within 2 days of a hydro-acoustic survey. Penguin foraging effort (time spent diving, number of wiggles per trip, number of foraging dives and the maximum distance travelled) increased and offspring body condition decreased as forage fish abundance declined. In addition, quantile regression revealed that variation in foraging effort increased as prey abundance around the colony declined. 5. Policy implications. Our results demonstrate that local forage fish abundance influences seabird foraging and offspring fitness. They also highlight the potential for offspring condition and the mean-variance relationship in foraging behaviour to act as leading indicators of poor prey abundance. By rapidly indicating periods where forage resources are scarce, these metrics could help limit seabird-fisheries competition and aid the implementation of dynamic ocean management.
Data from: Effects of seal predation on a modelled marine fish community and consequences for a commercial fishery
We constructed a size- and trait-based dynamic marine community model of the Celtic Sea/Biologically Sensitive Area, including grey seals Halichoerus grypus (Fabricius 1791) and harbour seals Phoca vitulina vitulina (Linnaeus 1758) to examine potential resource conflict between seals and commercial trawl fisheries. The model incorporates seal diet preference, population size and commercial fishery catch, with survey data to quantify ecological interactions between seals and fisheries. Total annual consumption by seals was an order of magnitude less than the catch of the modelled trawl fishery. Increasing fishing pressure reduced fish spawning stock biomass (SSB) much more than a proportionally equivalent increase in seal predation. For most fish species, quadrupling seal predation showed little effect on the predicted fishery catch. These results arise from relatively low seal abundance and partial niche partitioning. The fishery harvested a wider range of fish lengths and species than seals consumed. The fish community was dominated by small fish lengths and seals predated on these more than suggested by their calculated diet preference. Seal predation disproportionately affected several fish species not targeted by the fishery, but seal predation did not significantly affect the SSB of any of the species that constitute 90% of the total landings of the fishery. Synthesis and applications. Predation of fish by grey and harbour seals is unlikely to harm commercial trawl fisheries in south-west Irish waters. This conclusion differs from those of some model-based studies of other North Atlantic systems, demonstrating the need for ecosystem-specific evidence in considering such conflicts. In systems with low niche overlap between seals and fisheries, the two are largely decoupled in effect, leaving fishing pressure as the overwhelming determinant of targeted fish stock status.
Data from: The role of a dominant predator in shaping biodiversity over space and time in a marine ecosystem
1. Exploitation of living marine resources has resulted in major changes to populations of targeted species and functional groups of large-bodied species in the ocean. However, the effects of overfishing and collapse of large top predators on the broad-scale biodiversity of oceanic ecosystems remain largely unexplored. 2. Populations of the Atlantic cod (Gadus morhua) were overfished and several collapsed in the early 1990s across Atlantic Canada, providing a unique opportunity to study potential ecosystem-level effects of the reduction of a dominant predator on fish biodiversity, and to identify how such effects might interact with other environmental factors, such as changes in climate, over time. 3. We combined causal modelling with model selection and multimodel inference to analyse 41 years of fishery-independent survey data (1970–2010) and quantify ecosystem-level effects of overfishing and climate variation on the biodiversity of fishes across a broad area (172 000 km2) of the Scotian Shelf. 4. We found that alpha and beta diversity increased with decreases in cod occurrence; fish communities were less homogeneous and more variable in systems where cod no longer dominated. These effects were most pronounced in the colder north-eastern parts of the Scotian Shelf. 5. Our results provide strong evidence that intensive harvesting (and collapse) of marine apex predators can have large impacts on biodiversity, with far-reaching consequences for ecological stability across an entire ecosystem.
High mortality rates in a juvenile free-ranging marine predator and links to dive and forage ability
<p class="western">1. High juvenile mortality rates are typical of many long-lived marine vertebrate predators. Insufficient development in dive and forage ability are considered key drivers of this. However, direct links to survival outcome are sparse, particularly in free-ranging marine animals that may not return to land.</p> <p class="western">2. In this study, we conduct exploratory investigations toward early mortality in juvenile southern elephant seals <i>Mirounga leonina</i>. 20 post-weaning pups were equipped with (1) a new generation satellite relay data tag, capable of remotely transmitting fine-scale behavioural movements from accelerometers, and (2) a location transmitting only tag (so that mortality events could be distinguished from device failures). Individuals were followed during their first trip at sea (until mortality or return to land). Two analyses were conducted. First, the behavioural movements and encountered environmental conditions of non-surviving pups were individually compared to temporally concurrent observations from grouped survivors. Second, common causes of mortality were investigated using Cox's proportional hazard regression and penalised shrinkage techniques.</p> <p class="western">3. Nine individuals died (two females and seven males) and 11 survived (eight females and three males). All but one individual died before the return phase of their first trip at sea, and all but one were negatively buoyant. Causes of death were variable, although common factors included increased horizontal travel speeds, decreased development in dive and forage ability, and habitat type visited (lower sea surface temperatures and decreased total (eddy) kinetic energy).</p> <p class="western">4. For long-lived marine vertebrate predators, such as the southern elephant seal, the first few months of life following independence represent a critical period, when small deviations in behaviour from the norm appear sufficient to increase mortality risk. Survival rates may subsequently be particularly vulnerable to changes in climate and environment, which will have concomitant consequences on the demography and dynamics of populations.</p> <p class="western"> </p> <p class="western"> </p>
Data from: Three dimensional tracking of a wide-ranging marine predator: flight heights and vulnerability to offshore wind farms
A large increase in offshore wind turbine capacity is anticipated within the next decade, raising concerns about possible adverse impacts on birds as a result of collision risk. Birds' flight heights greatly influence this risk, yet height estimates are currently available only using methods such as radar- or ship-based observations over limited areas. Bird-borne data-loggers have the potential to provide improved estimates of collision risk and here, we used data from Global Position System (GPS)-loggers and barometric pressure loggers to track the three-dimensional movements of northern gannets rearing chicks at a large colony in south-east Scotland (Bass Rock), located <50 km from several major wind farm developments with recent planning consent. We estimated the foraging ranges and densities of birds at sea, their flight heights during different activities and the spatial variation in height during trips. We then used these data in collision-risk models to explore how the use of different methods to determine flight height affects the predicted risk of birds colliding with turbines. Gannets foraged in and around planned wind farm sites. The probability of flying at collision-risk height was low during commuting between colonies and foraging areas (median height 12 m) but was greater during periods of active foraging (median height 27 m), and we estimated that ˜1500 breeding adults from Bass Rock could be killed by collision with wind turbines at two planned sites in the Firth of Forth region each year. This is up to 12 times greater than the potential mortality predicted using other available flight-height estimates. Synthesis and applications: The use of conventional flight-height estimation techniques resulted in large underestimates of the numbers of birds at risk of colliding with wind turbines. Hence, we recommend using GPS and barometric tracking to derive activity-specific and spatially explicit flight heights and collision risks. Our predictions of potential mortality approached levels at which long-term population viability could be threatened, highlighting a need for further data to refine estimates of collision risks and sustainable mortality thresholds. We also advocate raising the minimum permitted clearance of turbine blades at sites with high potential collision risk from 22 to 30 m above sea level.
Data from: Satellite telemetry reveals higher fishing mortality rates than previously estimated, suggesting overfishing of an apex marine predator
Overfishing is a primary cause of population declines for many shark species of conservation concern. However, means of obtaining information on fishery interactions and mortality, necessary for the development of successful conservation strategies, are often fisheries-dependent and of questionable quality for many species of commercially exploited pelagic sharks. We used satellite telemetry as a fisheries-independent tool to document fisheries interactions, and quantify fishing mortality of the highly migratory shortfin mako shark (Isurus oxyrinchus) in the western North Atlantic Ocean. Forty satellite-tagged shortfin mako sharks tracked over 3 years entered the Exclusive Economic Zones of 19 countries and were harvested in fisheries of five countries, with 30% of tagged sharks harvested. Our tagging-derived estimates of instantaneous fishing mortality rates (F = 0.19–0.56) were 10-fold higher than previous estimates from fisheries-dependent data (approx. 0.015–0.024), suggesting data used in stock assessments may considerably underestimate fishing mortality. Additionally, our estimates of F were greater than those associated with maximum sustainable yield, suggesting a state of overfishing. This information has direct application to evaluations of stock status and for effective management of populations, and thus satellite tagging studies have potential to provide more accurate estimates of fishing mortality and survival than traditional fisheries-dependent methodology.
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Allen Brain Atlas
Allen Brain Atlas is an Allen Institute collection of brain map atlases, datasets, APIs, and analysis tools covering mouse, human, and non-human primate brain resources.
Annotated Behaviour and Observability Dataset (ABODe)
ABODe is a University of Edinburgh DataShare dataset for behavior classification in group-housed mice using home-cage video, identities, bounding boxes, ground-plate positions, and annotator labels.
DANDI Archive for NWB datasets
DANDI is a BRAIN Initiative archive for publishing and sharing neurophysiology data, including electrophysiology, optophysiology, and behavioral data packaged as NWB and related standards.
International Brain Laboratory public data
The International Brain Laboratory public data releases expose standardized mouse decision-making experiments, including Neuropixels recordings, widefield calcium imaging, behavior, and session metadata accessed through the ONE API.
OpenNeuro
OpenNeuro is a free, open platform for sharing neuroimaging datasets, with public search, dataset pages, and download paths for web, S3, DataLad, and the OpenNeuro CLI.