Biology subjects

Arlinghaus, R.

Publications and source records attributed to Arlinghaus, R..

17 recordsLinked to original sources

bioRxiv2025

A large-scale dataset of functional mouse ganglion cell layer responses

We present the AO_SCPLOWLLC_SCPLOW-GCL dataset, a large-scale resource of functional two-photon Ca2+-imaging recordings with rich meta-data information from more than 80,000 cells in the ganglion cell layer (GCL) of the ex vivo mouse retina. Collected over nine years across more than 139 experimental sessions, the dataset provides recordings of light-evoked responses to various stimuli, including a shared set of core stimuli. To enable cell-type-specific analyses, cells are probabilistically assigned to 46 previously characterized functional groups, including retinal ganglion cells and displaced amacrine cells. Further, we assessed the influence of experimental and biological factors on the functional responses and found only small batch effects across experimenters, setups, and recording sessions, highlighting the datasets consistency. The AO_SCPLOWLLC_SCPLOW-GCL dataset offers a comprehensive and standardised reference for studying retinal computation at scale. It supports population-level analyses, computational modelling, and the development of machine learning approaches for biological time-series data. Future releases will expand the dataset with additional mouse lines and light stimuli, creating a growing resource for the vision science community.

neuroscience↗

bioRxiv2023

Nitric oxide mediates differential effects in mouse retinal ganglion cells

Neuromodulators have major influences on the regulation of neural circuit activity across the nervous system. Nitric oxide (NO) has been shown to be a prominent neuromodulator in many circuits and has been extensively studied in the retina. Here, it has been associated with the regulation of light adaptation, gain control, and gap junctional coupling, but its effect on the retinal output, specifically on the different types of retinal ganglion cells (RGCs), is still poorly understood. In this study, we used two-photon Ca2+imaging and multi-electrode array (MEA) recordings to measure light-evoked activity of RGCs in the ganglion cell layer in the ex vivo mouse retina. This approach allowed us to investigate the neuromodulatory effects of NO on a cell type-level. Our findings reveal that NO selectively modulates the suppression of temporal responses in a distinct subset of contrast-suppressed RGC types, increasing their activity without altering the spatial properties of their receptive fields. Given that under photopic conditions, NO release is triggered by quick changes in light levels, we propose that these RGC types signal fast contrast changes to higher visual regions. Remarkably, we found that about one-third of the RGC types, recorded using two-photon Ca2+imaging, exhibited consistent, cell type-specific adaptational response changes throughout an experiment, independent of NO. By employing a sequential-recording paradigm, we could disentangle those additional adaptational response changes from drug-induced modulations. Taken together, our research highlights the selective neuromodulatory effects of NO on RGCs and emphasizes the need of considering non-pharmacological activity changes, like adaptation, in such study designs.

neuroscience↗

bioRxiv2023

Corroborating age with oxygen isotope profiles in otoliths: consequences for estimation of growth, productivity and management reference points in northern pike (Esox lucius) in the southern Baltic Sea

Accurate and precise age estimates are crucial for assessing the life-history of fish and providing management advice for fisheries, but age validation studies remain rare or absent in many species. Aging from scales is common, as it is non-lethal, but potential for underaging old fish exists. Using 85 northern pike (Esox lucius) collected from the southern Baltic Sea in Germany as a model, we corroborated age readings based on annual cycles of oxygen isotopes ({delta}18O) in otoliths to infer the timing and validity of growth, so as to compare results with visual age estimations from scales and otoliths. Otoliths were accurate and precise, while age readings from scales systematically underestimated the age of old pike. Fitting population-level von Bertalanffy growth models to the size-at-age data estimated via{delta} 18O-profiling, otoliths or scales revealed a larger terminal length (L{infty}) and a lower body growth coefficient k in scale-aged fish compared to otolith and corroborated age data. Populating an age-structured model with structure-specific growth model parameters demonstrated that the maximum sustainable yield (MSY) was estimated to be about 37% lower using scale-informed growth models relative to growth models fitted to corroborated and otolith-based size-at-age data. Thus, pike populations assessed and modeled based on scale age readings might appear less productive than they really are. Using scale-based ages to inform management regulations may therefore result in too conservative management and lost biomass yield, while instilling unrealistic angler expectations as to the trophy potential of the fishery.

ecology↗

bioRxiv2022

Size-selective mortality fosters evolutionary changes in collective learning across ontogeny and decision-making in zebrafish, Danio rerio

Size-selective harvesting evolutionary alters the life-history, behavioural and physiological traits in exploited fish populations. Changes in these traits may cause alteration in learning and decision-making abilities, either due to energetic trade-offs with brain investment that may vary across development or via correlations with boldness, sociability or other personality traits. Whether size-selective harvesting evolutionarily alters learning and decision-making abilities in fish remains unexplored, despite the global scale of fisheries. We tested the hypothesis that persistent removal of large-bodied individuals typical of many fisheries reduces learning ability in adults but not in juveniles, increases cognitive flexibility but reduces decision-making ability in adults. We examined associative learning through ontogeny, and reversal learning and collective decision-making in adults in three selection lines of zebrafish (Danio rerio) generated through positive, negative and random size-selective harvesting for five generations. Fish groups of each selection line were tested across ontogeny using a colour-discrimination paradigm with a food reward. The associative reversal task was conducted with a social reward, and the propensity to make group decisions was tested in an associative task. All selection lines showed significant learning ability and improved performance across ontogeny. Consistent with our hypothesis, the large-harvested line fish revealed a significantly reduced learning speed as subadults and adults, while the small-harvested line fish showed slower error rate compared to controls as 4-month old adults. We found no evidence of memory decay, and the selection lines did not vary in associative reversal ability. Decision-making speed did not vary across lines, but the large-harvested line made faster decisions during the probe trial. We conclude that size-selective harvesting typical of many fisheries evolutionarily alters learning and decision making. As this is likely to negatively and persistently affect resource acquisition and survival in exploited populations, we suggest that the cognition-related mechanism we identify may increase natural mortality.

ecology↗

bioRxiv2022

Rhythm of relationships in a social fish over the course of a full year in the wild

Animals are expected to adjust their social behaviour to cope with challenges in their environment. Therefore, for fish populations, in temperate regions with seasonal and daily environmental oscillations, characteristic rhythms of social relationships should be pronounced. To date, most research concerning fish social networks and biorhythms has occurred in artificial laboratory environments or over confined temporal scales of days to weeks. By contrast, little is known about the social networks of wild, freely roaming fish, including how seasonal and diurnal rhythms modulate social networks over the course of a full year. The advent of high-resolution acoustic telemetry enables us to quantify detailed social interactions in the wild over time-scales sufficient to examine seasonal rhythms at whole-ecosystems scales. Our objective was to explore the rhythms of social interactions in a social fish population at various time-scales over one full year in the wild by examining high-resolution snapshots of dynamic social network. To that end, we tracked the behaviour of 36 adult common carp, Cyprinus carpio, in a 25 ha lake and constructed temporal social networks among individuals across various time-scales, where social interactions were defined by proximity. We compared the network structure to a temporally shuffled null model to examine the importance of social attraction, and checked for persistent characteristic groups ("friendships") over time. The clustering within the carp social network tended to be more pronounced during daytime than nighttime throughout the year. Social attraction, particularly during daytime, was a key driver for interactions. Shoaling behavior substantially increased during daytime in the wintertime, whereas in summer carp interacted less frequently, but the interaction duration increased. Characteristic groups were more common in the summer months and during nighttime, where the social memory of carp lasted up to two weeks. We conclude that social relationships of carp change diurnally and seasonally. These patterns were likely driven by predator avoidance, seasonal shifts in lake temperature, visibility, forage availability and the presence of anoxic zones. The techniques we employed can be applied generally to high-resolution biotelemetry data to reveal social structures across other fish species at ecologically realistic scales.

animal behavior and cognition↗

bioRxiv2021

Specific Detection of Endogenous S129 Phosphorylated α-Synuclein in Tissue Using Proximity Ligation Assay

BACKGROUNDSynucleinopathies are a group of neurodegenerative disorders that are pathologically characterized by the accumulation of protein aggregates called Lewy Bodies. Lewy bodies are primarily composed of -synuclein (asyn) protein, which is phosphorylated at serine 129 (pS129) when aggregated. Currently available commercial antibodies used to stain for pS129 asyn can cross react with other proteins, thus making it difficult to specifically detect endogenous pS129 asyn and to interpret pS129 asyn staining. OBJECTIVETo develop a staining procedure that detects pS129 asyn with high specificity and low background. METHODSWe use the fluorescent and brightfield in situ Proximity Ligation Assay (PLA) to specifically detect pS129 asyn in cell culture, mouse and human brain sections. RESULTSThe pS129 asyn PLA specifically stained for endogenous, soluble pS129 asyn in cell culture, mouse brain sections, and human brain tissue without significant cross-reactivity or background signal. CONCLUSIONSThis PLA method can be used to specifically detect pS129 asyn in order to further explore and understand its role in health and disease.

neuroscience↗

bioRxiv2021

Size-selective mortality fosters ontogenetic changes in collective risk-taking behaviour in zebrafish, Danio rerio

Size-selective mortality is common in fish populations and can operate either in a positive size-selective fashion or be negatively size-selective. Through various mechanisms (like genetic correlations among behaviour and life-history traits or direct selection on behaviour co-varying with growth rate or size-at-maturation), both positive- and negative size-selection can result in evolutionary changes in behavioural traits. Theory suggests that size-selection alone favours boldness, but little experimental evidence exists about whether and to what extent size-selection can trigger its evolution. Here we investigated the impact of size-selective mortality on boldness across ontogeny using three experimental lines of zebrafish (Danio rerio) generated through positive (large-harvested), negative (small-harvested) and random (control line) size-selective mortality for five generations. We measured risk-taking during feeding (boldness) under simulated aerial predation threat and in presence of a live cichlid. We found that boldness decreased with ontogenetic age under aerial predation threat, and the small-harvested line was consistently bolder than controls. Collective personality emerged post larval stages among the selection lines. In presence of a cichlid, the large-harvested line was bolder at the highest risk of predation. The large-harvested line showed higher variability and plasticity in boldness across life stages and predation risks. Collectively, our results demonstrate that size-selective harvesting may evolutionarily alter risk-taking tendency. Size-selection alone favours boldness when selection acts on small fish. Selection typical of fisheries operating on large fish favours boldness at the highest risk of predation and increases behavioural variability and plasticity. There was no evidence for positive size-selection favouring evolution of shyness.

ecology↗

bioRxiv2021

Data-poor stock assessment of fish stocks co-exploited by commercial and recreational fisheries: applications to pike (Esox lucius) in the western Baltic Sea

Information on catch and effort of recreational angling in mixed-use fisheries (co-exploited by commercial and recreational fishers) is often scarce, preventing the application of data-rich stock assessments typically performed for industrialized commercial fisheries. Here, we show how data-poor stock assessment methods developed for marine fisheries, particularly a class of models labelled as "catch-only" models (COMs), offer a possible solution. As a case study, we use COMs to assess a northern pike stock around the German Baltic island of Rugen. We fit multiple COMs to a time-series of total pike removals, and use their outputs as explanatory variables in superensemble models. We conclude that the stock is fully exploited and currently declining. Our study highlights the potential for using COMs to determine status of previously-unassessed coastal and freshwater stocks facing recreational fishing pressure, and demonstrates how incorporating recreational removals is crucial for achieving reliable insights into the status of mixed-use stocks.

zoology↗

bioRxiv2019

Harvesting-induced evolution of collectivebehavior in a fish

Intensive and size-selective harvesting is an evolutionary driver of life-history as well as individual behavioral traits. Yet, whether and to what degree harvesting modifies the collective behavior of exploited species is largely unknown. We present a multi-generation harvest selection experiment with zebrafish (Danio rerio) as a model species to understand the effects of size-selective harvesting on shoaling behavior. The experimental system is based on a large-harvested (typical of most wild capture fisheries targeting larger size classes) and small-harvested (typical of specialized fisheries and gape-limited predators targeting smaller size classes) selection lines. By combining high resolution tracking of fish behavior with computational agent-based modeling we show that shoal cohesion changed in the direction expected by a trade-off between vigilance and the use of social cues. In particular, we document a decrease of vigilance in the small-harvested line, which was linked to an increase in the attention to social cues, favoring more cohesive shoals. Opposing outcomes were found for the large-harvested line, which formed less cohesive shoals. Using the agent-based model we outline possible consequences of changes is shoaling behavior for both fishing and natural mortality. The changes in shoaling induced by large size-selective harvesting may decrease fishing mortality, but increase mortality by natural predators. Our work suggests an insofar overlooked evolutionary mechanism by which size-selective harvesting can affect mortality and in turn population dynamics of exploited fish.

ecology↗

bioRxiv2019

Saving large fish through harvest slots outperforms the classical minimum-length limit when the aim is to achieve multiple harvest and catch-related fisheries objectives

We address the problem of optimal size-selective exploitation in an age-structured fish population model by systematically examining how density- and size-dependency in growth, mortality and fecundity affect optimal harvesting patterns when judged against a set of common fisheries objectives. Five key insights are derived. First, while minimum-length limits often maximize the biomass yield, exploitation using harvest slots (i.e., regulations that protect both immature and very large individuals) can generate within 95% of maximum yield, and harvest slots generally maximize the number of fish that are harvested. Second, density-dependence in growth and size-dependent mortality predict more liberal optimal size-limits than those derived under assumptions of no density and size-dependence. Third, strong density-dependence in growth maximizes the production of trophy fish in the catch only when some modest harvest is introduced; the same holds for numbers harvested, when the stock-recruitment function follows the Ricker-type. Fourth, the inclusion of size-dependent maternal effects on fecundity or egg viability has only limited effects on optimal size limits, unless the increase in fecundity with mass ("hyperallometry") is very large. Extreme hyperallometry in fecundity also shifts the optimal size-limit for biomass yield from the traditional minimum-length limit to a harvest slot. Fifth, harvest slots generally provide the best compromises among multiple objectives. We conclude that harvest slots, or more generally dome-shaped selectivity to harvest, can outperform the standard minimum-length selectivity. The exact configuration of optimal size limits crucially depends on objectives, local fishing pressure, the stock-recruitment function and the density and size-dependency of growth, mortality and fecundity.

ecology↗

bioRxiv2019

Intraspecific population admixture of a top piscivore correlates with anthropogenic alteration of freshwater ecosystems

Conservation of local genetic diversity is an important policy objective, but intraspecific genetic diversity can be transformed by natural ecological processes associated with anthropogenic changes in ecosystems. Environmental changes and a strong interconnection of drainage systems impact freshwater biodiversity from gene to population level. Populations can either become extinct or expand their range and accompanying secondary contacts can lead to genetic admixture. We investigated how the genetic population structure and the patterns of genetic admixture of Esox lucius L. (the northern pike) vary with the type of ecosystem and the integrity of the ecosystem assessed by measures under the European Water Framework Directive. The pike inhabits river, lake and brackish water ecosystems, where it is confronted with different ecological disturbances. We analysed 1,384 pike samples from the North, Baltic and Black Sea drainages and differentiated between metapopulations from each hydrogeographic region using genotypes from 15 microsatellites and mitochondrial cyt b sequences. Individual populations showed signs of genetic admixture ranging from almost zero to complete replacement by foreign genotypes. Hierarchical general linear modeling revealed a highly significant positive association of the degree of genetic admixture with decreasing ecological status. This may mean that populations in disturbed environments are more prone to influences by foreign genotypes or, alternatively, increased genetic admixture may indicate adaptation to rapid environmental changes. Regardless of the underlying mechanisms, our results suggest that anthropogenic alterations of natural freshwater ecosystems can influence genetic structures, which may lead to a large-scale reduction of intraspecific genetic diversity.

evolutionary biology↗

bioRxiv2019

Impact of recreational fisheries on aquatic and riparian biodiversity in artificial lake ecosystems: implications for conservation

Humanity is facing a biodiversity crisis, with freshwater-associated biodiversity in a particularly dire state. Novel ecosystems created through human use of mineral resources, such as gravel pit lakes, can provide substitute habitats for conservation of freshwater and riparian biodiversity. However, many of these artificial ecosystems may exhibit high recreational use intensity, which may limit their biodiversity potential.The species richness of several taxa (plants, amphibians, dragonflies, damselflies, waterfowl, songbirds) was assessed and a range of taxonomic biodiversity metrics were compared between gravel pit lakes managed for recreational fisheries (N = 16) and unmanaged reference lakes (N = 10), while controlling for non-fishing related environmental variation.The average species richness of all examined taxa was similar among both lake types and no substantial differences in species composition were revealed when examining the pooled species inventory. Similarly, there were no differences among lake types in the presence of rare species and in the Simpson diversity index across all the taxa that were assessed.Variation in species richness among lakes was correlated with woody habitat, lake morphology (surface area and steepness) and land use, but not correlated with the presence of recreational fisheries. Thus, non-fishing related environmental variables had stronger effects on local species presence than recreational-fisheries management or the presence of recreational anglers.Collectively, no evidence was found that anglers and recreational-fisheries management constrain the development of aquatic and riparian biodiversity in gravel pit lakes in the study region. Conservation of species diversity at gravel pit lakes could benefit from an increasing reliance on habitat enhancement activities.Competing Interest StatementThe authors have declared no competing interest.View Full Text

ecology↗

bioRxiv2019

Fisheries-induced evolution of the circadian system and collective personality traits

Intensive and trait-selective harvesting of fish and wildlife can cause evolutionary changes in a range of life-history and behavioural traits. These changes might in turn alter the circadian system both at behavioral and molecular levels, with knock-on effects on daily physiological processes and behavioural outputs. We examined the evolutionary impact of size-selective mortality on collective risk-taking behavior and the circadian system in a model fish species. We exposed zebrafish (Danio rerio) to either large or small size-selective mortality relative to a control over five generations, followed by eight generations during which harvesting halted to remove maternal effects. Large size-selective mortality typical of many fisheries and specialized predators targeting larger size classes decreased collective risk-taking behavior compared to controls. The opposite occurred in response to small size-selective mortality typical of specialized fisheries and most gape-limited predators. The evolutionary changes in risk-taking behavior were linked to daily activity rhythms in response to small size-selective mortality, while no changes were observed in response to large size-selective mortality. We also found changes in the molecular circadian core clockwork in response to both size selective mortality treatments. These changes disappeared in the clock output pathway, resulting in similar transcription profiles of both size-selected lines. The results suggest a switch downstream to the molecular circadian core clockwork, leading to overall similar daily activity patterns across selection lines. Our experimental harvest left an evolutionary legacy in collective risktaking behavior and relatedly in the circadian system, both at behavioral and molecular levels. Changes to risk-sensitive behavior of exploited organisms can have far-reaching consequences for how space and time is used and may also affect catchability and natural predation.

evolutionary biology↗

bioRxiv2018

Managing river fish biodiversity generates substantial economic benefits in four European countries

Ecosystems and biodiversity produce benefits to society, but many of them are hard to quantify. For example, it is unclear whether European societies gain benefits from experiencing rivers that host high native biodiversity. Without such knowledge, monetary investments into ecologically oriented river management plans are difficult to justify. The objective of this study was to reveal how the public in four European countries values ecological characteristics of domestic rivers and the outcomes of hypothetical river basin management plans designed to improve river ecosystems, particularly fish biodiversity. We conducted a choice experiment among the populations in Norway, Sweden, Germany and France. We found similar preference structures in all countries with high marginal willingness-to-pay for improvements of abiotic river attributes (increased accessiblity of the river banks, improved bathing water quality, decreased river fragmentation). Citizens also benefited from certain fish species occurring in a river with native salmonid species being more valued than nonnatives, particularly in Norway, and from the degree of a rivers native biodiversity. Welfare measures calculated for selected river basin management plans (policy scenarios) revealed societal benefits that were primarily derived from ecological river management whereas a scenario focusing on hydroelectricity production generated the lowest utility. We conclude that ecological river management may produce high nonmarket economic benefits in all study countries, particularly through the management of abiotic river attributes and the restoration of declining or extinct fish species. Our results help to inform decisions on restoration efforts by showcasing the benefits that these measures have for the public.

ecology↗

bioRxiv2018

Impact of recreational fisheries management on fish biodiversity in gravel pit lakes with contrasts to unmanaged lakes

Gravel pit lakes constitute novel ecosystems that can be colonized by fishes through natural or anthropogenic pathways. Many of these man-made lakes are used by recreational anglers and experience regular fish stocking. Recreationally unmanaged gravel pits may also be affected by fish introductions, e.g., through illegal fish releases, thereby contributing to the formation of site-specific communities. Our objective was to compare the fish biodiversity in gravel pit lakes with and without the recent influence of recreational fisheries management. We sampled 23 small (< 20 ha) gravel pit lakes (16 managed and 7 unmanaged) in north-western Germany and compared fish community and diversity metrics obtained using littoral electrofishing and multimesh gillnet catch per unit effort data. Given the size of the lakes we sampled we expected species poor communities and elevated fish diversity in the managed systems due to stocking. The two lake types were primarily mesotrophic and did not differ in key abiotic and biotic environmental characteristics. Both lakes types hosted similar fish abundance and biomass, but were substantially different in terms of the fish community structure and species richness. Fish were present in all lakes with at least three species. We discovered a higher -diversity and a lower {beta}-diversity in managed gravel pit lakes compared to unmanaged lakes. Thus, recreational fisheries management appeared to foster homogenization of fish communities, likely because fisheries managers stock these lakes with desired fish species (e.g., piscivorous fishes and large bodied cyprinids). However, we also detected anthropogenic pathways in the colonization of unmanaged gravel pit lakes, presumably from illegal releases by private people. Importantly, hardly any non-native species were detected in the gravel pits we studied, suggesting that recreational fisheries management not necessarily promotes the spread of exotic species.\n\nSignificance StatementLittle is known about fish communities in artificially created gravel pit lakes. We compared those managed by recreational fishers with those lacking fisheries management in north-western Germany. We found fishes in all gravel pit lakes and demonstrated a higher -diversity but more homogenized fish communities in managed gravel pit lakes compared to unmanaged lakes. We did not detect the establishment of relevant abundances of non-natives fishes despite intensive fisheries management.

ecology↗

bioRxiv2017

Ecological, angler and spatial heterogeneity drive social and ecological outcomes in an integrated landscape model of freshwater recreational fisheries

Freshwater recreational fisheries constitute complex adaptive social-ecological systems (SES) where mobile anglers link spatially structured ecosystems. We present a general social-ecological model of a spatial recreational fishery for northern pike (Esox lucius) that included an empirically measured mechanistic utility model driving angler behaviors. We studied emergent properties at the macro-scale (e.g., region) as a result of local-scale fish-angler interactions, while systematically examining key heterogeneities (at the angler and ecosystem level) and sources of uncertainty. We offer three key insights. First, the angler population size and the resulting latent reginal angling effort exerts a much greater impact on the overall regional-level overfishing outcome than any residential pattern (urban or rural), while the residential patterns strongly affects the location of local overfishing pockets. Second, simplifying a heterogeneous angler population to a homogenous one representing the preference and behaviours of an average angler risks severely underestimating landscape-level effort and regional overfishing. Third, we did not find that ecologically more productive lakes were more systematically overexploited than lower-productive lakes. We conclude that understanding regional-level outcomes depends on considering four key ingredients: regional angler population size, the angler population composition, the specific residential pattern in place and spatial ecological variation. Simplification of any of these may obscure important dynamics and render the system prone to collapse.

ecology↗

bioRxiv2017

Spearfishing promotes a timidity syndrome and increases the safe operating distances in fish

In a landscape of fear, humans are altering key behaviors expressed by wild-living animals, including those related to foraging, reproduction and survival. When exposed to potentially lethal human actions, such as hunting or fishing, fish and wildlife is expected to behaviorally respond by becoming more timid, but proving such responses underwater in the wild has been challenging. Using a rich dataset collected in situ, we provide evidence of spearfishing-induced behavioral effects in five coastal fish species using the flight initiation distance (FID) as a proxy of predator avoidance and boldness. We document that spearfishing promotes a timidity syndrome (i.e., an increase of the average timidity of harvested populations) and that the wariness of preys wariness is influenced by individual size, level of protection offered through marine protected areas and the ability to recognize the risk posed by underwater human predators. In particular, we show that changes in the appearance of the observer (spearfisher vs. snorkeler) modulate the risk perception among the exploited species, and these differences are more evident outside marine protected areas where spearfishing is allowed. We also detected a positive correlation between FID and fish size, with larger specimens (that are more likely targets of spearfishers) revealing larger FID. The behavioral effects were most clearly expressed in the most heavily exploited species and declined towards the less desired and less targeted ones, which may be a result of learning mechanisms and plasticity and/or fisheries-induced evolution of timidity. Our study reveals a trade-off where intensive spearfishing negatively affects future spearfishing success through behavior-based alteration of catchability. Either rotating harvest or implementation of mosaics of protected and exploited areas might be needed to manage spearfishing-induced timidity in exploited stocks.

ecology↗