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opencc-zeroAug 2020View details →

Accelerated reproduction is not an adaptive response to early life adversity in wild baboons

In humans and other long-lived species, harsh conditions in early life often lead to profound differences in adult life expectancy. In response, natural selection is expected to accelerate the timing and pace of reproduction in individuals who experience some forms of early life adversity. However, the adaptive benefits of reproductive acceleration following early adversity remain untested. Here we test a recent version of this theory, the internal predictive adaptive response (iPAR) model, by assessing for the first time whether accelerating reproduction following early life adversity leads to higher lifetime reproductive success. We do so by leveraging 48 years of continuous, individual-based data from wild female baboons in the Amboseli ecosystem in Kenya, including prospective, longitudinal data on early life adversity, reproductive pace, and lifetime reproductive success.We find that while adversity in early life led to dramatically shorter lifespans, individuals who experiencedearly adversity didnot accelerate their reproduction compared to those who did not experience early adversity. Further, while accelerated reproduction predicted increased lifetime reproductive success overall, these benefits were not specific to females who experienced early life adversity. Instead, females only benefited from reproductive acceleration if they also led long lives. Our results call into question the theory that accelerated reproduction is an adaptive response to early life adversityin baboons and other long-lived species.

opencc-zeroAug 2020View details →

Better together? how intergroup associations affect energy balance and feeding behavior in wild bonobos

When the benefits of interacting with out-group members exceed the associated costs, social groups may be expected to be tolerant towards each other. However, in many species exhibiting intergroup tolerance, the nature of benefits gained from intergroup encounters remains unclear. We investigated the potential costs and benefits associated with intergroup associations in bonobos, a species with varying degrees of intergroup tolerance, by testing whether these associations conferred energetic benefits to participants under different socioecological contexts, and whether the consequences of these associations substantially differed from within-group competition. We used measures of socioecological factors (i.e. fruit abundance and group size), feeding and ranging behaviors, and a physiological marker of energy balance (i.e. urinary c-peptides of insulin) collected over a 19-month period from two neighboring wild communities in the Kokolopori Bonobo Reserve, DRC. We found that intergroup associations did not affect individuals' energy balance, but they did alter individuals' ranging and feeding behavior. Specifically, bonobos travelled longer distances, visited larger fruit patches, and increased the time spent feeding on fruits on days they associated with the neighboring group. These adaptations in feeding behavior may be strategies to offset the energetic costs of increased travel distances. In the absence of obvious energetic benefits and with clear strategies employed to offset energetic costs, it is likely that intergroup associations in bonobos provide benefits unrelated to energy acquisition, such as social benefits. Our study sheds light on the potential incentives promoting social networks to extend beyond and across groups in a tolerant species.

Data from: Standardization and validation of a panel of cross-species microsatellites to individually identify the Asiatic wild dog (Cuon alpinus)

The Asiatic wild dog or dhole (Cuon alpinus) is a highly elusive, monophyletic, forest dwelling, social canid distributed across south and Southeast Asia. Severe pressures from habitat loss, prey depletion, disease, human persecution and interspecific competition resulted in global population decline in dholes. Despite a declining population trend, detailed information on population size, ecology, demography and genetics is lacking. Generating reliable information at landscape level for dholes is challenging due to their secretive behaviour and monomorphic physical features. Recent advances in non-invasive DNA-based tools can be used to monitor populations and individuals across large landscapes. In this paper, we describe standardization and validation of faecal DNA-based methods for individual identification of dholes. We tested this method on 249 field-collected dhole faeces from five protected areas of the central Indian landscape in the state of Maharashtra, India. Results We tested a total of 18 cross-species markers and developed a panel of 12 markers for unambiguous individual identification of dholes. This marker panel identified 101 unique individuals from faecal samples collected across our pilot field study area. These loci showed varied level of amplification success (57-88%), polymorphism (3-9 alleles), heterozygosity (0.23-0.63) and produced a cumulative misidentification rate or PID(unbiased) and PID(sibs) value of 4.7x10-10 and 1.5x10-4, respectively, indicating a high statistical power in individual discrimination from poor quality samples. Conclusion Our results demonstrated that the selected panel of 12 microsatellite loci can conclusively identify dholes from poor quality, non-invasive biological samples and help in exploring various population parameters. This genetic approach would be useful in dhole population estimation across its range and will help in assessing population trends and other genetic parameters for this elusive, social carnivore.

Data from: Mortality, perception, and scale: understanding how predation shapes space use in a wild prey population

Attempts to assess behavioral responses of prey to predation risk are often confounded by depredation of prey. Moreover, the scale at which the response of prey is assessed has important implications for discovering how predation risk alters prey behavior. Herein, we assessed space use of wild Ring-necked Pheasants (Phasianus colchicus) in response to spatial and temporal variation in recreational hunting. We radio-marked pheasants and monitored space use at two spatial scales: short-term seasonal home range, and nightly resting locations. Additionally, we considered temporal variation in predation risk by monitoring space use prior to and during the pheasant hunting season. Although we found no change in nightly resting location, pheasants subjected to predation risk expanded their home range and shifted home range location even when invulnerable to predation. Home range formation was plastic, with home ranges expanding and contracting as risk fluctuated before and during the hunting season. Depredation reduced the measured response within the population, obscuring the potential importance of perceived predation risk in shaping prey communities, particularly when not measured at the appropriate scale. By assessing space use of a wild prey population at multiple scales, considering spatial and temporal variation in predation risk, we show that not only does predation risk affect space use, but that the effects at the population level may be challenging to assess when not measured at the appropriate ecological scale because of the direct effects of differential mortality on the same behaviors.

Data From: Breeders are less active foragers than non-breeders in wild Damaraland mole-rats

Eusocial insect societies are characterised by a clear division of labour between non-breeding workers and breeding queens and queens often do not contribute to foraging, defence and other maintenance tasks. It has been suggested that the structure and organisation of social mole-rat groups resembles that of eusocial insect societies. However, the division of labour has rarely been investigated in wild mole-rats and it is unknown whether breeders show decreased foraging activity compared to non-breeding helpers in natural groups. Here we show that, in wild Damaraland mole-rats (Fukomys damarensis), breeding males and females show lower activity in foraging areas than non-breeding group members. Both breeders and non-breeders displayed variation in activity across the different seasons. Our results suggest that group living allows social mole-rat breeders to reduce their investment in energetically costly and potentially risky foraging tasks which could contribute to the extended life-span of breeding individuals in this species and other social mole-rats.

Data from: Demography, life history trade-offs, and the gastrointestinal virome of wild chimpanzees

In humans, senescence increases susceptibility to viral infection. However, comparative data on viral infection in free-living non-human primates—even in our closest living relatives, chimpanzees and bonobos (Pan troglodytes and P. paniscus)—are relatively scarce, thereby constraining an evolutionary understanding of age-related patterns of viral infection. We investigated a population of wild eastern chimpanzees (P. t. schweinfurthii), using metagenomics to characterize viromes (full viral communities) in the feces of 42 sexually mature chimpanzees (22 males, 20 females) from the Kanyawara and Ngogo communities in Kibale National Park, Uganda. We identified 12 viruses from at least four families with genomes of both single-stranded RNA and single-stranded DNA. Although fecal viromes of both sexes varied with chimpanzee age, viral richness increased with age in males but not in females. This effect was largely due to three viruses, salivirus, porprismacovirus, and chimpanzee stool-associated RNA virus (chisavirus), which occurred more frequently in samples from older males. This finding is consistent with the hypothesis that selection on males for early-life reproduction compromises investment in somatic maintenance, which has delayed consequences for health later in life, in this case reflected in viral infection and/or shedding. Fecal viromes may be useful for studying processes related to the divergent reproductive strategies of males and females, aging, and sex differences in longevity.

Data from: Healthy cardiovascular biomarkers across the lifespan in wild-born chimpanzees (Pan troglodytes)

Chimpanzees (Pan troglodytes) are a crucial model for understanding the evolution of human health and longevity. Cardiovascular disease is a major source of mortality during ageing in humans and therefore a key issue for comparative research. Current data indicate that compared to humans, chimpanzees have proatherogenic blood lipid profiles, an important risk factor for cardiovascular disease in humans. However, most work to date on chimpanzee lipids come from laboratory-living populations where lifestyles diverge from a wild context. Here, we examined cardiovascular profiles in chimpanzees living in African sanctuaries, who semi-free-range in large forested enclosures, consume a naturalistic diet, and generally experience conditions more similar to a wild chimpanzee lifestyle. We measured blood lipids, body weight and body fat in 75 sanctuary chimpanzees and compared them to publicly available data from laboratory-living chimpanzees from the Primate Ageing Database. We found that semi-free-ranging chimpanzees exhibited lower body weight and lower levels of lipids that are risk factors for human cardiovascular disease, and that some of these disparities increased with age. Our findings support the hypothesis that lifestyle can shape health indices in chimpanzees, similar to effects observed across human populations, and contribute to an emerging understanding of human cardiovascular health in evolutionary context.

Evaluating Bayesian stable isotope mixing models of wild animal diet and the effects of trophic discrimination factors and informative priors

<blockquote> 1. Ecologists quantify animal diets using direct and indirect methods, including analysis of faeces, pellets, prey items and gut contents. For stable isotope analyses of diet, Bayesian stable isotope mixing models (BSIMMs) are increasingly used to infer the relative importance of food sources to consumers. Although a powerful approach, it has been hard to test BSIMM performance for wild animals because precise, direct dietary data are difficult to collect. 2. We evaluated the performance of BSIMMs in quantifying animal diets when using δ13C and δ15N stable isotope ratios from the feathers and red blood cells of common buzzard Buteo buteo chicks. We analysed mixing model outcomes with various trophic discrimination factors (TDFs), with and without informative priors, and compared these to direct observations of prey provisioned to chicks by adults at nests, using remote cameras. 3. Although BSIMMs with different TDFs varied markedly in their performance, the statistical package SIDER generated TDFs for both feathers and blood that resulted in model outputs that accorded well with direct observations of prey provisioning. Using feather TDFs derived from captive peregrines Falco peregrinus resulted in estimates of diet composition that were also similar to provisioned prey, though blood TDFs from the same study performed poorly. The inclusion of informative priors, based on conventional analysis of pellet and prey remains, markedly reduced model performance. 4. BSIMMs can provide accurate assessments of diet in wild animals. TDF estimates from the SIDER package performed well. The inclusion of informative priors from conventional methods in Bayesian mixing models can transfer biases into model outcomes, leading to erroneous results. </blockquote>

Estimation of environmental, genetic and parental age at conception effects on telomere length in a wild mammal

Understanding individual variation in fitness-related traits requires separating the environmental and genetic determinants. Telomeres are protective caps at the ends of chromosomes that are thought to be a biomarker of senescence as their length predicts mortality risk and reflect the physiological consequences of environmental conditions. The relative contribution of genetic and environmental factors to individual variation in telomere length is however unclear, yet important for understanding its evolutionary dynamics. In particular, the evidence for transgenerational effects, in terms of parental age at conception, on telomere length is mixed. Here, we investigate the heritability of telomere length, using the 'animal model', and parental age at conception effects on offspring telomere length in a wild population of European badgers (Meles meles). While we found no heritability of telomere length and low evolvability (<0.001), our power to detect heritability was low and a repeatability of 2% across individual lifetimes provides a low upper limit to ordinary narrow-sense heritability. However, year (25%) and cohort (3%) explained greater proportions of the phenotypic variance in telomere length. There was no support for cross-sectional or within-individual parental age at conception effects on offspring telomere length. Our results indicate a lack of transgenerational effects through parental age at conception and a low potential for evolutionary change in telomere length in this population. Instead, we provide evidence that individual variation in telomere length is largely driven by environmental variation in this wild mammal.

The strength and form of natural selection on transcript abundance in the wild

Gene transcription variation is known to contribute to disease susceptibility and adaptation, but we currently know very little about how contemporary natural selection shapes transcript abundance. Here, we propose a novel analytical framework to quantify the strength and form of ongoing natural selection at the transcriptome level in a wild vertebrate. We estimated selection on transcript abundance in a cohort of a wild salmonid fish (Salmo trutta) affected by an extracellular myxozoan parasite (Tetracapsuloides bryosalmonae) through mark-recapture field sampling and the integration of RNA-seq with classical regression-based selection analysis. We show, based on fin transcriptomes of the host, that infection by the parasite and subsequent host survival is linked to upregulation of mitotic cell cycle process. We also detect a widespread signal of disruptive selection on transcripts linked to host immune defence, host-pathogen interactions, cellular repair and maintenance. Our results provide insights about how selection can be measured at the transcriptome level to dissect the molecular mechanisms of contemporary natural selection driven by climate change and emerging anthropogenic threats. We anticipate that the approach described here will enable critical information on the molecular mechanisms and targets of natural selection to be obtained in real time.

opencc-zeroSep 2021View details →

Are native and non-native pollinator friendly plants equally valuable for native wild bee communities?

Bees rely on floral pollen and nectar for food. Therefore, pollinator friendly plantings are often used to enrich habitats in bee conservation efforts. As part of these plantings, non-native plants may provide valuable floral resources, but their effects on native bee communities have not been assessed in direct comparison with native pollinator friendly plantings. In this study, we performed a common garden experiment by seeding mixes of 20 native and 20 non-native pollinator friendly plant species at separate neighboring plots at three sites in Maryland, USA, and recorded flower visitors for two years. A total of 3744 bees (120 species) were collected. Bee abundance and species richness was either similar across plant types (mid-season and for abundance also late season) or lower at native than at non-native plots (early season and for richness also late season). The overall bee community composition differed significantly between native and non-native plots, with 11 and 23 bee species found exclusively at one plot type or the other, respectively. Additionally, some species were more abundant at native plant plots, while others were more abundant at non-natives. Native plants hosted more specialized plant-bee visitation networks than non-native plants. Three species out of the five most abundant bee species were more specialized when foraging on native plants than on non-native plants. Overall, visitation networks were more specialized in the early season than in late seasons. Our findings suggest that non-native plants can benefit native pollinators, but may alter foraging patterns, bee community assemblage, and bee-plant network structures.

Wild at heart: programs to diminish negative ecological and evolutionary effects of conservation hatcheries

Hatchery programs are critical for conservation and management of many imperiled fishes. Most traditional aquaculture programs negatively affect ecological performance, genetic, and phenotypic diversity of hatchery-origin fish compared with wild counterparts. Here, we synthesize outcomes of three conservation programs aimed at enhancing 'wildness'. Each program focuses on a different species: lake sturgeon, razorback sucker, and Rio Grande silvery minnow. These species differ in key life history traits including size and age at sexual maturity, reproductive and migratory behavior, and habitat requirements. Threats to persistence of the focal taxa, however, exemplify common pressures experienced by freshwater fishes worldwide. Conservation hatchery programs for lake sturgeon, razorback sucker, and Rio Grande silvery minnow capitalize on natural spawning in the wild followed by collections of wild-fertilized eggs/larvae for hatchery rearing. Individuals are repatriated to the wild after rearing to body sizes less susceptible to mortality. Protocols include collections of eggs or larvae across the entire spawning period and at appropriate geographic scales to maximize retention of genetic diversity and, to increase the likelihood of preserving variation for heritable life history traits. Using direct and indirect evidence we show that hatchery programs that allow individuals to fulfill parts of the life-cycle in their native habitats can be conducted without compromising genetic diversity. Adoption of similar strategies in other imperiled fishes would improve understanding of species life history, and provide an incentive to protect native habitats so they may eventually support self-sustaining populations.

Data from: Maternally-derived anti-helminth antibodies predict offspring survival in a wild mammal

The transfer of antibodies from mother to offspring provides crucial protection against infection to offspring during early life. However, few studies have tested the consequences of variation in maternal antibody transfer for offspring fitness in the wild. Further, separating out the immunoprotective effects of antibodies from their association with nutritional resources provided by the mother is difficult. Here, we measured plasma levels of total and parasite-specific antibody levels in neonatal (<10 days old) wild Soay sheep over 25 years to quantify variation in maternal antibody transfer and test its association with offspring survival. Maternal antibody transfer was predicted by maternal age and previous antibody responses, and was consistent within mothers across years. Neonatal total IgG antibody levels were positively related to early growth, suggesting they reflected nutritional transfer. Neonatal parasite-specific IgG levels positively predicted first year offspring survival, independent of lamb weight, total IgG levels and subsequent lamb parasite-specific antibody levels. This relationship was in part mediated via an indirect negative association with parasite burden. We show that among-female variation in maternal transfer of immunity can have long-term effects on offspring growth, parasite burden and fitness in the wild, and is likely to impact naturally-occurring host and parasite dynamics.

Limited evidence of cloning and selfing within wild populations of coral-eating crown-of thorns seastar (Acanthaster cf. solaris)

Population outbreaks of crown-of-thorns seastars (CoTS; Acanthaster spp.) are contributing to extensive coral loss and reef degradation throughout the Indo west-Pacific, but the causes and underlying mechanisms of population maintenance and outbreaks are equivocal. Two recent publications suggest that, in addition to outbreeding sexual reproduction, asexual reproduction through larval fission and selfing may contribute to rapid increases in the local abundance of Acanthaster spp. We re-analysed two large microsatellite datasets (collectively representing 3,714 individuals) that investigated connectivity in the Great Barrier Reef and Pacific region to investigate if potential cloning or selfing can be evidenced in the population genetic structure. Within this dataset we identified only a small number (18, < 0.5%) of putative clones (repeated multi locus genotypes). We argue that several of these are due to sampling and processing errors rather than direct evidence of cloning. Analysis of the population genetic structure (i.e., pairwise genetic differences between individuals, deviations from Hardy-Weinberg-Equilibrium, and linkage disequilibrium) also yielded no genetic evidence for asexual reproduction. There was a tendency towards slight heterozygote deficits, so we cannot refute that selfing does occur, but this is mostly likely attributable to sampling artefacts. Although we cannot exclude that asexual reproduction occurs to some extent in Acanthaster populations, we find no evidence that these processes make a contribution to population structure or directly enhance larval supply.

Data from: Incubation recess behaviors influence nest survival of Wild Turkeys

In ground nesting upland birds, reproductive activities contribute to elevated predation risk, so females presumably use multiple strategies to ensure nest success. Identification of drivers reducing predation risk have primarily focused on evaluating vegetative conditions at nest sites, but behavioral decisions manifested through movements during incubation may be additional drivers of nest survival. However, our understanding of how movements during incubation impact nest survival is limited for most ground nesting birds. Using GPS data collected from female Eastern Wild Turkeys (n = 206), we evaluated nest survival as it relates to movement behaviors during incubation, including recess frequency, distance traveled during recesses, and habitat selection during recess movements. We identified 9,361 movements off nests and 6,529 recess events based on approximately 62,065 hours of incubation data, and estimated mean nest attentiveness of 84.0%. Numbers of recesses taken daily were variable across females (range: 1‒7). Nest survival modeling indicated that increased cumulative distance moved during recesses each day was the primary driver of positive daily nest survival. Our results suggest behavioral decisions are influencing trade-offs between nest survival and adult female survival during incubation to reduce predation risk, specifically through adjustments to distances traveled during recesses.

opennotspecifiedDec 2001View details →

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................................................................................................................................................. Fig. 3. SDSPAGE analysis of total bacterial protein extracts of the four roe deer isolates as well as other Bartonella species. Extracts of total bacterial protein were separated by SDSPAGE and stained with Coomassie brilliant blue. Lanes: M, molecular mass markers; 1, R1T; 2, R3; 3, R4; 4, R6; 5, Bartonella henselae; 6, Bartonella quintana; 7, Bartonella bacilliformis; 8, Bartonella elizabethae; 9, Bartonella clarridgeiae; 10, Bartonella alsatica; 11, Bartonella tribocorum; 12, Bartonella grahamii. in Bartonella schoenbuchii sp. nov., isolated from the blood of wild roe deer.

................................................................................................................................................. Fig. 3. SDSPAGE analysis of total bacterial protein extracts of the four roe deer isolates as well as other Bartonella species. Extracts of total bacterial protein were separated by SDSPAGE and stained with Coomassie brilliant blue. Lanes: M, molecular mass markers; 1, R1T; 2, R3; 3, R4; 4, R6; 5, Bartonella henselae; 6, Bartonella quintana; 7, Bartonella bacilliformis; 8, Bartonella elizabethae; 9, Bartonella clarridgeiae; 10, Bartonella alsatica; 11, Bartonella tribocorum; 12, Bartonella grahamii.

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................................................................................................................................................. Fig. 5. Phylogenetic tree based on 16S rRNA sequences (a) and gltA sequences (b) showing the position of strains R1T, R3, R4 and R6 in relation to the known Bartonella spp. The tree was rooted by using Brucella abortus (a) and Sinorhizobium meliloti (b) as the outgroup. in Bartonella schoenbuchii sp. nov., isolated from the blood of wild roe deer.

................................................................................................................................................. Fig. 5. Phylogenetic tree based on 16S rRNA sequences (a) and gltA sequences (b) showing the position of strains R1T, R3, R4 and R6 in relation to the known Bartonella spp. The tree was rooted by using Brucella abortus (a) and Sinorhizobium meliloti (b) as the outgroup.

opennotspecifiedDec 2001View details →

Data for: Infectious disease and sickness behaviour: tumour progression affects interaction patterns and social network structure in wild Tasmanian devils

Infectious diseases, including transmissible cancers, can have a broad range of impacts on host behaviour, particularly in the latter stages of disease progression. However, the difficulty of early diagnoses makes the study of behavioural influences of disease in wild animals a challenging task. Tasmanian devils (Sarcophilus harrisii) are affected by a transmissible cancer, devil facial tumour disease (DFTD), in which tumours are externally visible as they progress. Using telemetry and mark-recapture data sets, we quantify the impacts of cancer progression on the behaviour of wild devils by assessing how interaction patterns within the social network of a population change with increasing tumour load. DFTD negatively influences devils' likelihood of interaction within their network, an effect which increases with increasing tumour load. Infected devils were more active within their network late in the mating season, a pattern with repercussions for DFTD transmission. Our study provides a rare opportunity to quantify and understand the behavioural feedbacks of disease in wildlife and how they may affect transmission and population dynamics in general.

A large wild salmon stock shows genetic and life history differentiation within, but not between, rivers

Anadromous salmonid fishes frequently exhibit strong geographic population structuring. However, population genetic differentiation of Atlantic salmon (Salmo salar) at fine geographic scales differs across equivalent spatial extents in different regions. So far, fine-scale genetic differentiation has not been assessed in rivers of the Baltic Sea, a region that contains an evolutionarily distinct Atlantic salmon lineage. Thus, Baltic salmon are currently managed on the river level, without focus on potential genetic structure and diversity within rivers. Here, we used microsatellites to characterize the genetic structure of wild juvenile salmon sampled throughout the interconnected, northern Baltic Tornio and Kalix Rivers. We found genetic differentiation within the two rivers, but not between them: salmon in the upper reaches differed from individuals in the lower reaches, regardless of river system. Further, examining smolts migrating from the river to the sea and adults returning from the sea to spawn, we found an association between the genetic structure and seasonal migration timing. Out-migrating smolts genetically assigned to upper river reaches were older and tended to reach the sea later in the season than smolts from the lower reaches. In contrast, mature adults originating from the upper reaches returned to the river early in the season. Our observation of genetic population structuring between downstream and upstream reaches of the large Tornio and Kalix rivers, and its association with migration timing, implies that careful temporal management of the northern Baltic fisheries would help to preserve the diversity and sustainability of the wild salmon stocks of these rivers.

Data from: First measurements of field metabolic rate in wild juvenile fishes show strong thermal sensitivity but variations between sympatric ecotypes

The relationship between physiology and temperature has a large influence on population-level responses to climate change. In natural settings, direct thermal effects on metabolism may be exaggerated or offset by behavioural responses influencing individual energy balance. Drawing on a newly developed proxy, we provide the first estimates of the thermal performance curve of field metabolism in a wild fish. We investigate the thermal sensitivity of field metabolic rate in two sympatric, genetically distinct ecotypes of Atlantic cod from the Skagerrak coast of southern Norway. The combined ecotype median of field metabolic rate increased with increasing temperature until around 16°C, coincident with the thermal optimum for growth for juvenile Atlantic cod. Individual cod experienced temperatures in excess of the thermal optimum for field metabolic rate, indicating some degree of thermal limitation of field metabolism in a complex natural environment with the potential for thermal refugia. The two cod ecotypes showed different thermal performance curves for field metabolic rate, revealing that genetic components to temperature sensitivity persist beyond acclimation effects. The cold-adapted fjord ecotype maintained higher field metabolic rates at cooler temperatures than the warm-adapted North Sea ecotype, which showed clear preference for warmer waters around the thermal optimum. Field metabolic rates of the two ecotypes were strongly influenced by year and location of sampling, implying more complex behavioural responses to environmental conditions. We emphasise that the energy uses reflecting physiological conditions in the field should be considered in the evaluation of the effect of climatic variables on fish population dynamics and demonstrate that otolith isotopes provide an analytical framework to answer this question.