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Evolution: Unnatural selection

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Abstract

Fishing and hunting by humans are the main causes of mortality in many populations of wild animals. The consequence is that large and rapid changes occur in certain characteristics that far exceed changes due to other agents.

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... 2007, Garel ym. 2007, Stenseth & Dunlop 2009). Tasapainotila ei synnykään siten kuin luonnontilassa on tavanomaista, vaan kehityksestä voi tulla tempoilevaa ja jopa kaoottista, ellei saalispoistumaa osata kannan kehitystä vakauttavalla tavalla säädellä. ...
... 2007, Garel ym. 2007, Stenseth & Dunlop 2009). ...
... 2007, Kuparinen & Merilä 2007, Proaktor ym. 2007, Stenseth & Dunlop 2009). ...
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Intensified forest management after the last war and taking up the practice of calf hunting in the 1970’s created the prerequisites for a growing population of moose in Finland. The population has been regulated with varying success during the last few decades. This study looks at the history of the development of the regulation of the Finnish moose population, the biological foundations for it and the policies concerning it. The study also considers the effect of the management practices on the moose in Finland. The observations presented here are used to discuss future alternatives and for presenting a utopia of regulation which aims at reaching a stable and sustainably exploited population. The effects on the moose population of the regulation practiced to date have been sizeable. The population growth has been curtailed for the purpose of minimising moose damage. It has been done by harvesting one third of the animals each year and the harvest has been implemented so as not to reduce its production efficiency. This has given rise to a highly productive and extremely well exploited moose population. It seems that at the turn of the millennium, Finland housed a population of moose that appears to be more productive than anywhere else in the world. Changing the population structure by selective hunting has had an effect on the development of moose population density. There have been intermittent phases of explosive growth and falling population densities. Nevertheless, even the highest population densities have been reasonable compared to Finland’s western neighbours and symptoms of fitness and health from wear on grazing areas, in individual moose, have been negligible. At the end of the observation period, in 2007, the population densities were more or less within the target. The proportion of males, however, was lower than ever before and the number of calves per female and the proportion of twins were decreasing. The population has also changed genetically, as the proportion of males with cervina type antlers has increased in relation to those with the palmated type. Moose population regulation and management has been a multilateral series of events in natural resource policy, which has been based on scientific research and the experience gained from the continual follow-up of the population. Continual change has been characteristic of this process. The size and structure of the population, the aims of its regulation and management and the methods of follow-up and hunting have all undergone change. Information has been imprecise, the matters have been complicated and politically controversial, as well as socially difficult and polarised and decisions have had to be made in a hurry. Values have also changed. A valued game animal has become one that is harmful to the national economy. Its value has become interpreted as negative from the point of view of the social economy. On average, the results of the population regulation have been unsatisfactory. The population developed more or less according to target only during 1984–1992, which is when the co-operation between the relevant actors was efficient, aims and responsibilities were clear, the decision making was centralised and the biological sustainability of the populations had higher priority than the economic and harvesting aims. During the course of the 1990’s, however, the hunting law was renewed, the Hunters’ Central Organisation was reorganised and the responsibility for moose management shifted to the local level. In this process of re-organisation and law renewal, previous follow-up methods and practices lost their effectiveness. The development of the moose population became more unpredictable. Aiming for a biologically and socially sustainable population is the objective of the regulation utopia which looks to the future and is presented at the end of the study. One of its characteristics is discarding the aim of maximising the production efficiency of the population, which is what has been increasing the occurrence of problems caused by moose. Key words: Age structure, Alces alces, antler types, cervid genetics, exploitation, moose, moose management, moose policy, population dynamics, productivity, rapid contemporary evolution, regulation goals, sex ratio, weight development
... In addition, substantial changes in growth and maturation were observed in heavily exploited stocks during the 20th century. According to Stenseth and Dunlop (2009) phenotypic changes in harvested systems have recently been shown to be much more rapid than changes reported in natural systems. ...
... According to Stenseth and Dunlop (2009), although the evidence for harvesting-induced evolution is still under debate, management strategies should be designed under the assumption that it can occur. If properly controlled, the genetic reversion of the exploited populations can cause an evolutionary gain in production. ...
Article
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The decline in stocks of commercial fish species has been documented in several regions of the world. This decline is due partially to the effect of evolutionary pressure caused by the management of fishing activity, which reduces the size of fish after a few generations. In this paper, the population dynamics of the Pintado Pseudoplatystoma corruscans, one of the main commercial species of freshwater fish in Brazil, were simulated considering different scenarios of fishing mortality and different minimum and maximum lengths of capture. The results show that selective fishing based on the different proposed selectivity curves can result in an evolution-mediated increase in the growth rate of the fish, the biomass and the catch. This suggests that appropriate changes in Brazilian legislation can contribute to the sustainability of fisheries and to conservation of the fish stocks exploited by man.
... That selection leads to evolution is not in doubt, however, the relevant question in relation to management is how detrimental and rapid fisheries-induced evolution is compared with the direct detrimental effects of overfishing (7). The answer is a critical element of any formal evolutionary impact assessment of fishing activity (4,8). Theoretical studies of fisheries-induced evolution have focused on concepts and on finding the optimal value of a trait under selection (3,(9)(10)(11). ...
... Our theoretical calculation is an attempt at a general evolutionary impact assessment of fishing (4,8). It demonstrates that strong selection pressure by commercial fishing is expected to induce modest rates of changes in growth-related traits. ...
Article
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Commercial fisheries exert high mortalities on the stocks they exploit, and the consequent selection pressure leads to fisheries-induced evolution of growth rate, age and size at maturation, and reproductive output. Productivity and yields may decline as a result, but little is known about the rate at which such changes are likely to occur. Fisheries-induced evolution of exploited populations has recently become a subject of concern for policy makers, fisheries managers, and the general public, with prominent calls for mitigating management action. We make a general evolutionary impact assessment of fisheries by calculating the expected rate of fisheries-induced evolution and the consequent changes in yield. Rates of evolution are expected to be approximately 0.1-0.6% per year, and the consequent reductions in fisheries yield are <0.7% per year. These rates are at least a factor of 5 lower than published values based on experiments and analyses of population time series, and we explain why the published rates may be overestimates. Dealing with evolutionary effects of fishing is less urgent than reducing the direct detrimental effects of overfishing on exploited stocks and on their marine ecosystems.
... It should be noted that some biological mechanisms could potentially cause delayed responses to ameliorative management actions, thus blurring the expected synchrony of cause and effect. Assuming that run-times are heritable, Fishery Induced Evolution effects (FIE; for brief overviews see Heino andDieckmann 2009 andStenseth andDunlop 2009; for summary reviews see Allendorf et al. 2008;Fenberg and Roy 2008;Jørgensen et al. 2007;Law 2007;Kuparinen and Merilä 2007) could result in salmon populations' responses to previous fishery-selection pressures becoming manifest as delayed changes. Any such prior-induced changes might then have carried over into our study period. ...
... It should be noted that some biological mechanisms could potentially cause delayed responses to ameliorative management actions, thus blurring the expected synchrony of cause and effect. Assuming that run-times are heritable, Fishery Induced Evolution effects (FIE; for brief overviews see Heino andDieckmann 2009 andStenseth andDunlop 2009; for summary reviews see Allendorf et al. 2008;Fenberg and Roy 2008;Jørgensen et al. 2007;Law 2007;Kuparinen and Merilä 2007) could result in salmon populations' responses to previous fishery-selection pressures becoming manifest as delayed changes. Any such prior-induced changes might then have carried over into our study period. ...
Technical Report
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Modelling an Atlantic salmon (Salmo salar) population as three phenotypically homogeneous sub-stocks showed different sub-stock dynamics and time-trends, a finding which was robust to three quite extreme variations of marine-mortality scenarios. A process-centred demographic analysis of a phenotypically mixed population (river North Esk, eastern Scotland) separated the life-cycle into two portions: density-dependent (spawner to smolt), represented by a stock-recruitment relationship; density-independent at sea and in both the estuary and river during return to spawning sites. Extensive data spanning three decades was judiciously used to parameterise the model for three phenotypically distinct sub-stocks (early running multi-sea-winter; late-running multi-sea-winter; and one-sea-winter). Quantification of different population parameters was achieved for the putative substocks, illuminating historical population-trends and underlying mechanisms. The approach forms a template for similar model decompositions at other rivers with similar data. Broad implications for salmon management more widely included the enhanced benefits of a process-based life-cycle model that described more phenotypically homogeneous sub-stocks (than a single-stock formulation) for the transport of population parameter values (or derived Biological Reference Points) from well documented (parameter-donor) catchments to data-sparse (parameter recipient) catchments. Full text at: http://www.gov.scot/Publications/2015/10/7173
... As most females are not living more than two or three breeding seasons, selective pressure should favour an increased reproductive effort early in life and so, juveniles should invest more in reproduction at the risk of reduced adult size or shorter lifespan (Festa-Bianchet 2003;Garel et al. 2007). As the generation time in our population was especially low (i.e. about 2 years, Gaillard, Vassant & Klein 1987) compared to what can be expected for similar sized large herbivore (e.g. 7 years, Gaillard et al. 2008), the selective advantage of reproducing yearly should be higher in wild boar than in similar-sized ungulates (see Stenseth & Dunlop 2009 for similar arguments). The low threshold mass we reported here, along with the short generation time, involves a high potential impact on population growth to changes in recruitment parameters. ...
Article
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1. Identifying which factors influence age and size at maturity is crucial for a better understanding of the evolution of life-history strategies. In particular, populations intensively harvested, hunted or fished by humans often respond by displaying earlier age and decreased size at first reproduction. 2. Among ungulates wild boar (Sus scrofa scrofa L.) exhibit uncommon life-history traits, such as high fertility and early reproduction, which might increase the demographic impact of varying age at first reproduction. We analysed variation in female reproductive output from a 22-year long study of an intensively hunted population. We assessed how the breeding probability and the onset of oestrus responded to changes of female body mass at different ages under varying conditions of climate and food availability. 3. Wild boar females had to reach a threshold body mass (27–33 kg) before breeding for the first time. This threshold mass was relatively low (33–41% of adult body mass) compared to that reported in most other ungulates (about 80%). 4. Proportions of females breeding peaked when rainfall and temperature were low in spring and high in summer. Climatic conditions might act through the nutritional condition of females. The onset of oestrus varied a lot in relation to resources available at both current and previous years. Between none and up to 90% of females were in oestrus in November depending on the year. 5. Past and current resources accounted for equivalent amount of observed variations in proportions of females breeding. Thus, wild boar rank at an intermediate position along the capital–income continuum rather than close to the capital end where similar-sized ungulates rank. 6. Juvenile females made a major contribution to the yearly reproductive output. Comparisons among wild boar populations facing contrasted hunting pressures indicate that a high demographic contribution of juveniles is a likely consequence of a high hunting pressure rather than a species-specific life-history pattern characterizing wild boar.
... Palaeoecological and fire-history studies suggest that during the past period, the frequency of fire events was increased by human presence in the landscape (Bahuguna and Upadhyay, 2002). It is one of the Earth's most potent agents of ecological change (Allendorf and Hard, 2009;Stenseth and Dunlop, 2009), which has potentially far-reaching ecological consequences. Every forest fire brings with it significant losses of various types: human, economic, forest resources reduction, biogeocenoses destruction (Singh et al., 2016), and such alteration produces severe impacts on soils leading to their loss and erosion after fire occurrence, along with greenhouse gas emissions, change of climate patterns, and loss of ecosystem values and environmental services. ...
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The Uttarakhand State of India is rich in forest wealth with 45.4% forest cover (India State of Forest Report (2021). However, forest cover may change due to a number of anthropogenic and environmental factors. One of the factors leading to forest degradation is forest fires. Forest fires are related to factors that may be biotic, such as heavy accumulation of Chir pine (Pinus roxburghii, a dominant forest forming tree) needles on the forest floor influencing fuel load accumulation and flammability, or abiotic, such as climate, topography, or soil type influencing fuel moisture and fire spread. This study was carried out using satellite images of study area where fire was classified using the geographical information system (GIS) into four frequency classes (no fire, low fire, moderate fire, and high fire). We sampled a total of 160 quadrates for trees, 320 for shrubs and 480 for herbaceous plants to assess vegetation diversity for each forest fire frequency class. No fire was recorded for 13,619 sample points, which covers an area of 84% of the study area, whereas low fire frequency was recorded for 1784 sample points covering an area of 11%. In the present study, significant differences in species diversity were observed across the fire frequency classes. While species diversity increased in the low fire frequency class, an increase in fire frequency led to a decline in diversity and increased dominance of certain fire-tolerant species. Our results show that species richness and density decreased in higher fire frequency classes, which could be due to a poor regeneration process. We found that tree species diversity was higher for the low fire frequency class, followed by moderate fire frequency class, no fire frequency class, and was lowest for the high fire frequency class. The diversity of herbs decreased with increasing fire frequency, from a minimum of 12 species in the high fire frequency class to a maximum of 37 in the no fire frequency class. Some of the fire-adapted species were Myrica esculenta, Pyrus pashia, Lyonia ovalifolia, Carissa spinarum, Pyracantha crenulata, Desmodium microphyllum, and Micromeria biflora the regeneration of which should be promoted rehabilitate the fire damage forest ecosystem of Uttarakhand.
... Results from the current study emphasise that management needs to consider the long-term, evolutionary impacts of regulations. A number of recent studies have highlighted the potentially negative population-level consequences that can arise through harvest or improper management of fish and wildlife resources, resulting either from evolutionary or plastic changes to populations (Olsen et al. 2004;Darimont et al. 2009;Stenseth & Dunlop 2009;Sutter et al. 2012). Together, these studies, coupled with the present results, emphasise the need to consider potential population-dependent evolutionary responses to human resource use, and the need for a precautionary approach to reduce the risk of undesirable evolutionary population changes. ...
... , 2008 ; Darimont et al . , 2009 ) , warning us about the consequences of ignoring potential evolutionary effects ( Stenseth and Dunlop , 2009 ) . ...
Article
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Large terrestrial carnivores, e.g. wolves or bears, often play a key ecological role from their position at the apex of trophic systems. Changes to their populations reverberate through ecological communities; consequently their widespread decline in numbers and shrinking distribution due to human persecution has brought about a loss and reconfiguration of biological diversity in many systems. Although many large carnivore populations are now under conservation-minded management, political and economic constraints make compromises necessary. A common compromise is to permit limited harvests, with the premise of sustainability and the objective to increase tolerance and funding for carnivore recovery and conservation. Here we question whether a large carnivore that has to “look over its shoulder” for human hunters can still fully perform its ecological role at the apex of a trophic system. We use information about carnivore behavior, ecology, trophic interactions, and the effects of human exploitation to argue that exploitation of large carnivores, even if sustainable numerically, undermines the commonly expressed rationale for their conservation, namely the restoration and preservation of ecosystem functionality. Our argument centers around (i) the necessity of behavioral adjustments in large carnivores to anthropomorphic risk, which may limit their contribution to the “landscape of fear”, and (ii) the observation that many of the same features that put large carnivores at the apex of trophic systems also make them vulnerable to human exploitation and persecution, with implicit consequences for their ecological functionality and evolution. Although hunting large carnivores can improve public acceptance, managers must be aware of the trade-offs.
... In conclusion, age and length at maturation may reflect variation in reproductive potential and may have direct implications for management of walleyes. Furthermore, it is important to monitor and understand the role of adaptive versus plastic effects on maturation traits because changes from the adaptive effects may be more difficult to reverse (Conover et al. 2009;Stenseth and Dunlop 2009). Based on our results, we suggest that interpreting variation in maturation schedules based solely on A 50 and L 50 would be inappropriate because these indices are unsuitable for informing adaptive changes and because they are sensitive to sampling methods and biases. ...
Article
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Maturation schedules, key determinants of fish stocks' harvest potential and population dynamics, are influenced by both plastic and adaptive processes. Various indices are used to describe maturation schedules, and these have differential advantages for discriminating between plastic and adaptive processes. However, potential sampling-related biases associated with different maturation indices have not been fully evaluated. We analyzed three maturation indices for walleyes Sander vitreus in Lake Erie; Saginaw Bay, Lake Huron; and Oneida Lake, New York: age and length at 50% maturity, midpoint of age-specific maturity ogives (age-specific length at which probability of maturity = 0.50), and midpoints of probabilistic maturation reaction norms (PMRNs; age-specific length at which probability of maturing in the following year = 0.50). We then compared estimated maturation indices to evaluate sensitivity of different maturation indices to sampling-induced biases and to assess the relative importance of plastic versus adaptive processes in structuring interstock and temporal variation in maturation schedules. Our findings suggest that although small changes in sampling month, gear, and agency-related effects can bias estimates of age and length at 50% maturity and midpoints of maturity ogives, PMRN estimates appear to be robust to these biases. Furthermore, PMRN estimates are suggestive of potential adaptive variation in maturation schedules among walleye stocks and over time. For instance, Oneida Lake walleyes (which had relatively slow growth and low mortality rates) matured at a smaller size for a given age (smaller midpoints of PMRNs) than the other stocks. Temporally, walleyes in the western basin of Lake Erie matured at a larger size in recent years, as evidenced by increasing midpoints of PMRNs (1978–1989 versus 1990–2006 for Ohio Department of Natural Resources data and 1990–1996 versus 1997–2006 for Ontario Ministry of Natural Resources data). Our study highlights the necessity of monitoring maturation schedules via multiple maturation indices and the need to account for sampling-induced biases when comparing maturation schedules.
... First, one can assess the time scale necessary for a new pattern to emerge in a new or changing environment due to CC. Indeed, there is an ongoing debate on the time necessary for a fish population to adapt to abrupt changes such as CC or exploitation (Jørgensen et al. 2007;Kuparinen and Merilä 2007;Lilly et al. 2008;Andersen and Brander 2009;Stenseth and Dunlop 2009). Second, the transition period during the emerging process can be tentatively predicted if the model is made complex by replacing the random initial situation by the observed one, plus the addition of a proportion of 'stray' (Cury 1994), that is individuals that depart from the environmental natal homing. ...
Article
Eastern boundary upwelling ecosystems are highly productive and sustain the world’s largest fisheries, usually dominated by sardine and anchovy species. Stock size is highly variable from year to year due to the impact of the unstable physical environment on fish early stages. Biophysical models of early life-stage dispersal of marine organisms have been built by coupling (i) hydrodynamic models and (ii) life history models (i.e. egg and larva stages), and are therefore useful tools to investigate physical–biological interactions. Here, we review biophysical models of anchovy and sardine ichthyoplankton dispersals developed in the Benguela, Humboldt and Canary Current upwelling ecosystems. We also include a similar study conducted in the California Current upwelling on zooplankton. We then integrate this information into a comparative analysis of sardine and anchovy reproductive strategies in the different systems. We found that the main spawning periods match the season of (i) maximal simulated ichthyoplankton retention over the continental shelf in the northern Benguela, southern Humboldt and Canary (for sardine); (ii) maximal food concentration in the southern Benguela, California and Canary (for anchovy); and (iii) maximal shelf retention of ichthyoplankton and food concentration in the northern Humboldt (for both anchovy and sardine). This specificity of the northern Humboldt ecosystem could explain why it sustains the largest small pelagic fish stock. Finally, the possible effects of climate change on these patterns are discussed.
... Lastly, when management regulations only consider minimal legal size limits, it is worth considering that the selective harvesting of the largest individuals in a population may not only induce evolutionary changes in age-specific maturation, fecundity and longevity, but also may change the entire gene-pool towards less fit and small-bodied individuals (Stenseth & Dunlop 2009). The model does not address these issues but, by sparing a share of the largest individuals, one would expect a double benefit by maintaining higher recruitment, which can buffer against catch-induced declines, as well as countering against potential long-term evolutionary changes towards smaller and less fit individuals. ...
Article
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Abstract  Harvesting regulations for crustacean decapods generally focus on total catch and minimum legal size of individuals. However, there are trade-offs between total catch and minimum size, and possibly also for maximum size. The outcome of various harvesting restrictions was assessed by model iterations for one lake based on a long time series (29 years) of crayfish population size and annual harvesting. The paper explores how this decline might have been avoided by alternative harvest regulations based on a strong decline in the surveyed population and use of a deterministic model with two stable equilibria. The results of the model simulations suggested that the decline may have been avoided by reducing the annual catches by 15% without changing the minimum size regulation of 95 mm. The decline may also have been avoided by protecting the largest (and most fecund) individuals, e.g. by allowing harvesting of crayfish between 50 and 98 mm without reducing the total catches. The latter strategy might also have counteracted a long-term evolution towards smaller crayfish caused by selective harvesting of the largest individuals.
... Fisheries reference points and stock assessments may recognize that fish traits change overtime but because they rarely include time series longer than 3 or 4 decades they rarely incorporate how the life-history of fish (i.e. the behaviour and physiology that determine how they develop and reproduce throughout their life) can be evolving under the pressure of the commercial harvest (Stenseth and Dunlop 2009). The weight of a catch can be made up of many small individuals or a few large individuals, so it's not always obvious that either a) a mature fish is getting smaller over time, or b) a particular size of fish is more vulnerable than another. ...
Article
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Amendments to the Fisheries Act in 2012 effectively changed the focus of promoting fisheries sustainability in Canada from managing the habitat that sustains fish populations (Fish Habitat Management Program - FHMP) to managing the ongoing productivity of fish stocks related to Commercial, Recreational or Aboriginal (CRA) fisheries (Fisheries Protection Provisions - FPP). The new and central role of fisheries productivity is clearly stated in Section 6 of the Fisheries Act such that the Minister must consider “the contribution of the relevant fish to the ongoing productivity of commercial, recreational or Aboriginal fisheries” when evaluating the capacity of a proposed development or activity to cause “the death of fish or any permanent alteration to, or destruction of, fish habitat”. Since the amendment of the Act, the science and policy divisions of Fisheries and Oceans Canada (DFO) have been providing technical advice on the implications of the new focus on the FPP. The topic of this review is to discuss and evaluate appropriate indicator metrics that can link the changes in the components to productivity to a qualitative or quantitative change in CRA fisheries productivity. For a consistency of terminology within this paper, we will define “indicators” as metrics which have a direct link to CRA fisheries productivity, thus an indicator can also be a component of productivity metric. Advice from the recent drafts of the proposed FPP framework (Bradford et al. 2013, Koops et al. unpublished manuscript1) has suggested some desirable qualities in potential indicators. This literature review has gained insight into the use of different metrics by other fields of fisheries research, management and biomonitoring and also in their theoretical links to “ongoing productivity of CRA fisheries”. It sounds simplistic to say that any indicator can be linked to fisheries productivity given a proper set of assumptions, but this is generally true and a great strength of this field of research. The many linkages back to the intrinsic rate of population growth, carrying capacity or steepness coefficient offers flexibility to proponents to demonstrate quantitatively, if needed, how proposed alterations to habitat is expected to affect the CRA fisheries. In the great majority of cases, we would expect that proponents would measure only the indicator and reference the specific qualitative linkages proposed in this review and others. A common theme that has emerged throughout the literature review is that there is likely no “one-size-fits-all” indicator, or even set of indicators. This is not surprising as considerable effort was expended under the FHMP to find simple and ubiquitous metrics, yet it also proved challenging. A suite of indicators is likely most effective, but will also only be required for a particular size of project. Further, through the search for specific indicators we have discovered that some are already well parameterized for Canadian fish, offering reference points and relationships (often allometric) with other indicators.
... Because the processes of life are complicated there is no simple solution to the problem of surviving, as individuals and species, the unpredictable challenges that environments pose to populations. Human-induced perturbations (Allendorf and Hard, 2009;Darimont et al., 2009;Stenseth and Dunlop, 2009) have increased environmental uncertainty, greatly compromising species, ecosystem resilience, and the ability to withstand such perturbations (Berkes et al., 2003). Both natural (evolutionary) and unnatural (human-driven) forces are constantly putting pressure on populations and species to evolve toward new adaptive peaks or fitness optima (Schuler and Conte, 2009). ...
Article
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The brine shrimp Artemia is a micro-crustacean, well adapted to the harsh conditions that severely hypersaline environments impose on survival and reproduction. Adaptation to these conditions has taken place at different functional levels or domains, from the individual (molecular-cellular-physiological) to the population level. Such conditions are experienced by very few equivalent macro-planktonic organisms; thus, Artemia can be considered a model animal extremophile offering a unique suite of adaptations that are the focus of this review. The most obvious is a highly efficient osmoregulation system to withstand up to 10 times the salt concentration of ordinary seawater. Under extremely critical environmental conditions, for example when seasonal lakes dry out, Artemia takes refuge by producing a highly resistant encysted gastrula embryo (cyst) capable of severe dehydration enabling an escape from population extinction. Cysts can be viewed as gene banks that store a genetic memory of historical population conditions. Their occurrence is due to the evolved ability of females to “perceive” forthcoming unstable environmental conditions expressed by their ability to switch reproductive mode, producing either cysts (oviparity) when environmental conditions become deleterious or free-swimming nauplii (ovoviviparity) that are able to maintain the population under suitable conditions. At the population level the trend is for conspecific populations to be fragmented into locally adapted populations, whereas species are restricted to salty lakes in particular regions (regional endemism). The Artemia model depicts adaptation as a complex response to critical life conditions, integrating and refining past and present experiences at all levels of organization. Although we consider an invertebrate restricted to a unique environment, the processes to be discussed are of general biological interest. Finally, we highlight the benefits of understanding the stress response of Artemi
... Fourth, there are important gaps in the understanding of how natural and sexual selection shaped fish life histories in the first place. This makes it difficult to assess how fishing or other anthropogenic influences that act on top of natural selection may set up new selection gradients (Stenseth and Dunlop 2009). The science of fisheriesinduced evolution is basically evolutionary ecology with an added twist, and a broad field-based and experimental approach is needed to provide the foundations for interpreting and predicting fisheries-induced evolutionary change. ...
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Table of contents There is increasing evidence that fishing may cause rapid contemporary evolution in freshwater and marine fish populations. This has led to growing concern about the possible consequences such evolutionary change might have for aquatic ecosystems and the utility of those ecosystems to society. This special issue contains contributions from a symposium on fisheries-induced evolution held at the American Fisheries Society Annual Meeting in August 2008. Contributions include primary studies and reviews of field-based and experimental evidence, and several theoretical modeling studies advancing life-history theory and investigating potential management options. In this introduction we review the state of research in the field, discuss current controversies, and identify contributions made by the papers in this issue to the knowledge of fisheries-induced evolution. We end by suggesting directions for future research.
... We now turn to harvest, one of the most potent agents of anthropogenic trait change (Allendorf and Hard 2009;Darimont et al. 2009;Stenseth and Dunlop 2009), which has potentially far-reaching ecological consequences. In a classic study, Coltman et al. (2003) showed that trophy hunting in a population of bighorn sheep (Ovis canadensis) drove reductions in horn and body size and removed high breeding value males from the population, thereby potentially influencing population growth. ...
Article
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Human-induced trait change has been documented in freshwater, marine, and terrestrial ecosystems worldwide. These trait changes are driven by phenotypic plasticity and contemporary evolution. While efforts to manage human-induced trait change are beginning to receive some attention, managing its ecological consequences has received virtually none. Recent work suggests that contemporary trait change can have important effects on the dynamics of populations, communities, and ecosystems. Therefore, trait changes caused by human activity may be shaping ecological dynamics on a global scale. We present evidence for important ecological effects associated with human-induced trait change in a variety of study systems. These effects can occur over large spatial scales and impact system-wide processes such as trophic cascades. Importantly, the magnitude of these effects can be on par with those of traditional ecological drivers such as species presence. However, phenotypic change is not always an agent of ecological change; it can also buffer ecosystems against change. Determining the conditions under which phenotypic change may promote vs prevent ecological change should be a top research priority.
... Starting fishing at maximum year-class biomass minimises the impact a given catch has on stock biomass [4]. Moreover, the delayed onset of fishing is likely to reduce unnatural selection pressure [5] because the fish have reproduced already several times before being caught. ...
Article
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The Common Fisheries Policy (CFP) of the European Union has neither lived up to its aim of enhancing the sustainability of fish stocks nor that of improving the economic competitiveness of the fishing industry. This paper discusses the failure of the CFP from a biological, economical, legal and political perspective.
... Evolutionary changes induced by fishing can have far-reaching consequences, possibly altering yield, recovery potential, stock stability, profits from a fishery, species interactions, and migration patterns (Jørgensen et al. 2007). As these evolutionary effects may be slow or difficult to reverse (Conover et al. 2009;Dunlop et al. 2009b;Enberg et al. 2009;Stenseth and Dunlop 2009), the precautionary approach warrants that managers consider evolution when planning and implementing sustainable harvesting practices. In particular, the establishment of marine reserves may reduce the evolutionary effects of fishing, but appropriate reserve placement taking into account the spatial patterns of fisheries-induced selection pressures is crucial to their success. ...
... Although body size is recognized as a crucial factor determining a species' sensitivity to fishing (Le Quesne and Jennings 2012;Dulvy et al. 2014), age and size at maturation appear to be important for such sensitivity as well (Jennings et al. 1999). Earlier maturation at smaller size results in shorter generation time, increased likelihood of surviving until maturation, and higher intrinsic rate of increase (Hutchings 2008;Stenseth and Dunlop 2009;Le Quesne and Jennings 2012). As such, short-lived species, such as the capelin (Mallotus villosus), often recover quickly from population declines (Hutchings 2000;Gjøsaeter et al. 2009). ...
Article
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Under exploitation and environmental change, it is essential to assess the sensitivity and vulnerability of marine ecosystems to such stress. A species' response to stress depends on its life history. Sensitivity to harvesting is related to the life history “fast–slow” continuum, where “slow” species (i.e., large, long lived, and late maturing) are expected to be more sensitive to fishing than “fast” ones. We analyze life history traits variation for all common fish species in the Barents Sea and rank fishes along fast–slow gradients obtained by ordination analyses. In addition, we integrate species' fast–slow ranks with ecosystem survey data for the period 2004–2009, to assess life history variation at the community level in space and time. Arctic fishes were smaller, had shorter life spans, earlier maturation, larger offspring, and lower fecundity than boreal ones. Arctic fishes could thus be considered faster than the boreal species, even when body size was corrected for. Phylogenetically related species possessed similar life histories. Early in the study period, we found a strong spatial gradient, where members of fish assemblages in the southwestern Barents Sea displayed slower life histories than in the northeast. However, in later, warmer years, the gradient weakened caused by a northward movement of boreal species. As a consequence, the northeast experienced increasing proportions of slower fish species. This study is a step toward integrating life history traits in ecosystem-based areal management. On the basis of life history traits, we assess the fish sensitivity to fishing, at the species and community level. We show that climate warming promotes a borealization of fish assemblages in the northeast, associated with slower life histories in that area. The biology of Arctic species is still poorly known, and boreal species that now establish in the Arctic are fishery sensitive, which calls for cautious ecosystem management of these areas.
... Hunting drives new trait development in wild animal populations, influencing broader ecological dynamics [14,56], which could eventually be a precursor to speciation in some cases. Stenseth & Dunlop ([56], see also [57]) compared rate of phenotypic change in 40 populations subject to human harvesting against the rate seen in 20 systems experiencing selection from natural forces only (e.g. ...
Article
A central topic for conservation science is evaluating how human activities influence global species diversity. Humanity exacerbates extinction rates. But by what mechanisms does humanity drive the emergence of new species? We review human-mediated speciation, compare speciation and known extinctions, and discuss the challenges of using net species diversity as a conservation objective. Humans drive rapid evolution through relocation, domestication, hunting and novel ecosystem creation—and emerging technologies could eventually provide additional mechanisms. The number of species relocated, domesticated and hunted during the Holocene is of comparable magnitude to the number of observed extinctions. While instances of human-mediated speciation are known, the overall effect these mechanisms have upon speciation rates has not yet been quantified. We also explore the importance of anthropogenic influence upon divergence in microorganisms. Even if human activities resulted in no net loss of species diversity by balancing speciation and extinction rates, this would probably be deemed unacceptable. We discuss why, based upon ‘no net loss’ conservation literature— considering phylogenetic diversity and other metrics, risk aversion, taboo trade-offs and spatial heterogeneity. We conclude that evaluating speciation alongside extinction could result in more nuanced understanding of biosphere trends, clarifying what it is we actually value about biodiversity. © 2016 The Author(s) Published by the Royal Society. All rights reserved.
... Exploitation of fish populations can induce evolutionary responses in life histories(Kuparinen and Merilä 2007). For example, harvesting the largest individuals in a population may induce selective changes in age-specific maturation, fecundity and longevity, and possibly induce maturity at smaller sizes(Stokes and Law 2000;Reznick and Ghalambor 2005;Allendorf and Hard 2009;Stenseth and Dunlop 2009). Given the low exploitation rate of kōura, it is doubtful that harvest selection is currently occurring in the Te Arawa lakes. ...
... In addition to modifications to ecosystems structures, human activities may also affect the evolution of species traits (Western 2001). Many authors claim that fishing has been a source of evolutionary changes in natural populations (Olsen et al. 2004;Jorgensen et al. 2007; Stenseth & Dunlop 2009). However, there is debate about the generality, strength and pace of the 'fisheriesinduced evolution' (FIE) (Marshall & McAdam 2007;Browman, Law & Marshall 2008;Brown et al. 2008;Hilborn & Minte-Vera 2008; Andersen & Brander 2009). ...
Article
Changes in life-history traits have been observed in many fish species over past decades. This led to the “fisheries-induced evolution” hypothesis proposing that fisheries may be causing genetic changes to populations through selective harvesting. Another hypothesis, which is not mutually exclusive, is that observed changes are due to phenotypic plasticity in response to environmental changes. Using an individual-based demogenetic model, we investigate the relative importance of selective fishing and environmental change scenarios on the Atlantic salmon Salmo salar. In simulation experiments, results show that poor oceanic growth conditions resulting from environmental change drove mainly phenotypic responses, such as a shift towards a multiple-sea-winter life-history accompanied by a decline in population size. These changes were attributable to the longer time needed to reach maturation and the resulting increase in cumulative mortality during the oceanic phase. Increased selective fishing against multiple-sea-winter fish mainly induced an evolutionary effect in the form of a lower maturation threshold in females, increasing the proportion of one sea winter fish. The maturation threshold of males was not modified by selective fishing due to their earlier reproduction and return after a single winter at sea, thereby avoiding most of the selective effect of fishing. Policy implications: The results suggest that given the present configuration of traditional fisheries, fishing is likely to worsen the effects of oceanic environmental change. Management strategies avoiding targeting multiple-sea-winter fish may need to be considered in order to ensure the populations’ resilience to poor oceanic conditions for growth.
... S1ofJørgensen et al. 2007). It also seems that fisheries-induced adaptive change can adversely alter the ability of a population to recover from overharvesting(Hutchings 2005;Walsh et al. 2006;Enberg et al. 2009;Stenseth and Dunlop 2009). ...
Thesis
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Maintenance of phenotypic, and in particular genetic, diversity between and within stocks should be an integral goal of fisheries management and conservation. After all, it is this diversity that provides populations with the ability to withstand and recover from commercial fishing and environmental change. Traditionally, most marine fish species were assumed to be genetically homogeneous on broad geographic scales. However, evidence is mounting of widespread phenotypic, behavioural and genetic variation, often on surprisingly fine spatial scales. Yet, many exploited marine stocks continue to be managed as single panmictic units. Moreover, there are persuasive indications that adaptive changes in life history traits are occurring on contemporary time scales in response to fishing. This thesis addresses spatial and temporal variation in life history traits of a commercially valuable stock of Atlantic cod (Gadus morhua) found in the waters around Iceland. Recently, intriguing patterns of phenotypic, behavioural, life history and genetic variation have been documented, leading to uncertainty over the appropriateness, and implications of, the continued management of this stock as a single homogenous unit. Furthermore, the age and size at which 50% of Icelandic cod are mature has decreased over at least the past two decades. The first part of thesis documents interannual (1993 to 2006), regional, bathymetric and biological variation in a bioenergetic and a morphometric index of condition, namely the liver condition index and relative body condition index, respectively. The analyses were based on data collected during the annual spring and autumn groundfish surveys. Individual stomach content data from the spring were examined to assess the relationship between condition of cod and consumption of capelin Mallotus villosus Liver condition was generally highest in deeper water and in the northern and eastern regions; where temperatures were relatively cold and capelin consumption relatively high. The relative body condition index showed contrasting regional and bathymetric patterns, and the two indices were not correlated, signifying that the two types of condition indices are not equivalent and thus not interchangeable. A continuous decline in condition of cod in waters off the east coast was observed throughout the study period, but in other areas there were no persistent temporal trends. Mature cod were found to be in significantly better condition than immature cod of the same age, and mature females were in better condition than mature males. Estimation of probabilistic maturation reaction norms for cohorts 1964 to 1999 revealed that Icelandic cod now mature at significantly smaller sizes and younger ages. These changes were found to have occurred independently of those in condition, temperature and growth. According to length-at-age data, the latter had also decreased through the study period. Weighting the groundfish survey data with regional abundance estimates to account for spatial heterogeneity in maturity status and sampling intensity did not qualitatively affect the temporal trends. These findings support the hypothesis that such changes in maturation schedules are not caused by environmental factors alone but could also reflect a genetic change, potentially in response to intensive fishing. Preliminary findings from an individual-based eco-genetic model, parameterised in detail for Icelandic cod and in the final stages of development, indicate that this will be a valuable tool for further investigation of the causes of the observed life history variation. Most importantly, the model provides the opportunity to explore the consequences of that variation for the persistence and productivity of the stock under contemporary exploitation patterns and also environmental variation.
... However, the prolonged and unusually high fishing mortalities observed for commercially exploited species are unrivalled by natural selection events on adult fish (Jackson 2001;Darimont et al. 2009;Stenseth and Dunlop 2009). Large effective population sizes, which minimise effects of drift, in combination with microgeographic differentiation in some marine fish species Hauser and Carvalho 2008) promote local adaptation to harvesting patterns and significant evolutionary rates by fishing. ...
Thesis
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Increasing evidence suggests that size-selective mortality imposed by commercial fishing results in directional changes in life histories of exploited species, including effects on maturation age, growth rate and body size. Whether these changes are the result of fisheries-induced evolution or other selective pressures in the natural environment and/ or phenotypic plasticity continues to be the subject of much debate. Currently, molecular genetic data revealing fisheries-induced shifts at candidate loci are lacking. Here, the hypothesis that harvesting can induce genetic change over few generations was tested directly by subjecting laboratory-reared offspring of wild-caught Trinidadian guppies, Poecilia reticulata, to divergent, size-specific selection over three generations. The smallest/ largest/ random twenty percent of males was selected each generation and changes in standard length, as well as in the frequencies of alleles at neutral microsatellite loci and putative candidate genes for selection were recorded. Significant divergence between differently selected lines was observed for male standard length (± 7%), size (± 8-12%) and age (± 4-6%) at maturation, compared to only 1% change in standard length over generations in the random breeding control line. Significant drift between lines, but no genetic erosion or inbreeding, was apparent over generations at microsatellite markers. Signatures of selection and significant genetic divergence between selected lines were detected at five out of 17 putative candidate loci (Pr39, M9, M30, M987 and prolactin) which confirmed strong Y-linkage of genes underlying male body size in guppies, as indicated by the phenotypic data. Additionally, significant genotype-phenotype associations were obtained for twelve of the candidate genes. For two of these loci (M30 and M1046) an association between the same single nucleotide polymorphism and a QTL for standard length had been observed previously. To our knowledge, this is the first study where selection on body size with known intensity and direction has been compared directly with both a phenotypic response and changes at individual genetic marker loci. Hereby, this study forms one of the first pieces of molecular genetic evidence for fisheries-induced evolution: by demonstrating that phenotypic shifts in body size resulting from size-selective harvesting, comparable to commercial fisheries in principle, are underlain by quantifiable genetic change.
... FIE has also been characterized as "unnatural selection" (Allendorf & Hard 2009, Stenseth & Dunlop 2009). Indeed, adaptation to fishing often occurs at the cost of adaptation to a population's www.annualreviews.org ...
Article
Increased mortality from fishing is expected to favor faster life histories, realized through earlier maturation, increased reproductive investment, and reduced postmaturation growth. There is also direct and indirect selection on behavioral traits. Molecular genetic methods have so far contributed minimally to understanding such fisheries-induced evolution (FIE), but a large body of literature studying evolution using phenotypic methods has suggested that FIE in life-history traits, in particular maturation traits, is commonplace in exploited fish populations. Although no phenotypic study in the wild can individually provide conclusive evidence for FIE, the observed common pattern suggests a common explanation, strengthening the case for FIE. This interpretation is supported by theoretical and experimental studies. Evidence for FIE of behavioral traits is limited from the wild, but strong from experimental studies. We suggest that such evolution is also common, but has so far been overlooked.
... Fourth, there are important gaps in the understanding of how natural and sexual selection shaped fish life histories in the first place. This makes it difficult to assess how fishing or other anthropogenic influences that act on top of natural selection may set up new selection gradients (Stenseth and Dunlop 2009). The science of fisheriesinduced evolution is basically evolutionary ecology with an added twist, and a broad field-based and experimental approach is needed to provide the foundations for interpreting and predicting fisheries-induced evolutionary change. ...
... Exploitation of fish populations can induce evolutionary responses in life histories (Kuparinen and Merilä, 2007). For example, harvesting the largest individuals in a population may induce selective changes in age-specific maturation, fecundity and longevity, and possibly induce maturity at smaller sizes (Stokes and Law, 2000;Reznick and Ghalambor, 2005;Allendorf and Hard, 2009;Stenseth and Dunlop, 2009). Given the low exploitation rate of kōura, it is doubtful that harvest selection is currently occurring in the Te Arawa lakes. ...
Article
Freshwater crayfish or kōura (Paranephrops planifrons White, 1842) support important customary fisheries for Te Arawa iwi (tribal members) in the Te Arawa lakes, North Island, New Zealand. Until recently, however, there was limited published information on which to base fisheries regulations. We sampled over 9000 kōura in eight lakes using a traditional Māori harvesting method known as the tau kōura, which comprised bundles of bracken fern fronds (Pteridium esculentum) laid on the lake bed. We examined the catch rates and biological traits of kōura in the Te Arawa lakes and the implications for the current fishing regulations and kōura management. Kōura were present in all of the study lakes except Ōkaro, but harvestable quantities were only found in Rotorua, Rotomā and Rotoiti. The overall ratio of females to males was about 1:1. Egg-bearing kōura were found throughout the year, but only occasionally during the summer months. Kōura fecundity increased as a power function of orbit-carapace length (OCL). Size at onset of breeding for 50% of females, in lakes where kōura were present, ranged from 22.1 mm OCL to 27.5 mm OCL. In addition to existing regulations, the following management measures are recommended: (1) implementing a slot limit with a minimum size of 28 mm and a maximum size of 39 mm OCL, (2) banning the taking of egg-bearing kōura, (3) limiting deep-water harvest methods to the use of the tau kōura, and (4) implementing a tau kōura harvest season beginning on 1 December and ending on 31 March. To download use the following link http://authors.elsevier.com/a/1QtPBbiU1Ur7Y
... Harvest-based selection can be intensive enough to be relevant in an evolutionary sense (Pigeon et al. 2016), but there is uncertainty whether the rate of change can be as high as sometimes reported (Coulson et al. 2017). Many of the oft-cited papers on this subject speculate that hunter selection of ungulates with larger horns or antlers is intensive enough to cause detrimental evolutionary change throughout mountain sheep range, or even all hunted mammals (Harris et al. 2002, Festa-Bianchet 2003, Stenseth and Dunlop 2009, Hedrick 2011. Authors of other published works compared different taxa, sometimes in different areas (Skogland 1989, Garel et al. 2007, Hengeveld and Festa-Bianchet 2011, or make management recommendations to alleviate detrimental evolutionary effects of trophy hunting on ungulates with no evidence it is actually occurring (Festa-Bianchet 2003, Mysterud and Bischof 2010, Kuparinen and Festa-Bianchet 2016. ...
Article
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Differentially harvesting individual animals with specific traits has led some to argue that such selection can cause evolutionary change that may be detrimental to the species, especially if those traits are related positively to individual fitness. Most hunters are not selective in the type of animal they take, satisfied instead to harvest any legal animal. In a few exceptions, however, regulations may limit hunters to harvest animals of a minimum size or age regardless of their personal choice. Using information from a broad range of aquatic and terrestrial systems exposed to a myriad of potential and operational selective pressures, several authors have made expansive generalizations about selective harvest and its applicability to ungulates. Harvest-based selection can potentially be intensive enough to be relevant in an evolutionary sense, but phenotypic changes consistent with hunter selection are otherwise confounded with multiple environmental influences. Factors such as age, genetic contribution of females, nutrition, maternal effects, epigenetics, patterns of mating success, gene linkage, gene flow, refugia, date of birth, and other factors affecting selection interact with harvest to impede unidirectional evolution of a trait. The intensity of selection determines potential for evolutionary change in a meaningful temporal framework. Indeed, only under severe intensity, and strict selection on a trait, could human harvest prompt evolutionary changes in that trait. Broad generalizations across populations or ecological systems can yield erroneous extrapolations and inappropriate assumptions. Removal of males expressing a variety of horn or antler sizes, including some very large males, does not inevitably represent directional artificial selection unless the selective pressures are intensive enough to cause a unidirectional shift in allele frequencies that may act on some relevant life-history trait or process. Here I review the topic of harvest-based selection in male ungulates and discuss the inefficiency of trophy hunting in changing genetic expression of phenotype. © 2017 The Wildlife Society.
... Much attention and debate has centred on the potential for harvest-selection of life-history traits in cod and other exploited marine fishes (e.g., Olsen et al. 2004;Jørgensen et al. 2008), but there has been comparatively little discussion on the potential for harvest-selection on behavioural traits. This is despite the fact that behaviour affects catchability directly (Fernö and Olsen 1994), and thereby can result in a strong selectional differential (sensu Stenseth and Dunlop 2009). Even relatively slight behavioural differences between individuals may lead to large differences in the risk of fisheries mortality. ...
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Cod (Gadus morhua) are an iconic fish species of cultural, historical and economical significance across the Atlantic and adjacent seas. Among many scholarly investigations, this interest has prompted behavioural research, rendering cod one of the few commercially harvested marine fishes for which behaviour has been studied in a comprehensive manner. In our review of this behavioural work, we examine the variability in cod behaviour across five functional domains: foraging, predation, social interactions, migration and reproduction. Research to date suggests a high level of behavioural sophistication in cod that is underpinned by complex learning strategies and long-term memory. Cod also demonstrate substantial variability in how they respond to different ecological circumstances. Considerable variation is evident both within and between individuals, and in some instances, between populations. There are a number of pathways from which this variation appears to arise, such as asocial and social learning, environmental control of phenotypic plasticity and genetic control, but there are no known examples of behaviours that are purely the result of one of these mechanisms. Behavioural variation is therefore likely to result from a combination of these factors, underscoring the need for a quantitative, multivariate approach to understand behavioural variation in cod.
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Anthropogenic activities influence ongoing selective regimes leading to changes in phenotypic variation of plants and animals. The reduction of phenotypic variation may decrease populations' ability to cope with environmental changes. To counteract the increasing risk of extinction of affected populations, it is important to rescue intraspecific variability, assuring higher success of establishment and persistence under global changes. We evaluated whether it is possible to revert phenotypic changes caused by humans using as study case a bird‐dispersed palm that presents seed size reduction due to defaunation of large‐gaped frugivores. We investigated how defaunation changes the seed size profile of each population by evaluating the coefficient of variation, mean and percentage of large phenotypes of produced and dispersed seed sizes. Simple theoretical models were used to simulate the success of two restoration strategies: (a) direct reintroduction of missing phenotypes that were originally found in the species and (b) reintroduction of large‐bodied frugivores to restore the ecological function of large‐seed dispersal. Here we discuss the importance of rescuing phenotype states in restoration strategies. We found that defaunation changes the seed size profile by reducing the size of produced and dispersed seeds. By adding missing phenotypes one time, population mean seed size decreased back to phenotypically depauperated scenarios in eight generations. Conversely, large seed sizes could be rescued in approximately five generations after seed dispersal processes generated by large seed dispersers were re‐established. To rescue and sustain phenotypes such as large seed sizes in palm populations is necessary to restore the seed dispersal processes by large frugivores or add missing phenotypes continuously over time. The restoration of the seed dispersal processes by large frugivores has additional value over seed addition because it would benefit other bird‐dispersed species and, therefore, may be crucial to face ongoing global change scenarios. Synthesis and applications. Defaunation leads to character displacement within decades, having impact on populations, species and ecosystems. To prevent species extinction is paramount that phenotype variation is preserved. We propose the inclusion of phenotype restoration of wild populations as a goal for restoration framework.
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Globally, many fish species are overexploited, and many stocks have collapsed. This crisis, along with increasing concerns over flow-on effects on ecosystems, has caused a reevaluation of traditional fisheries management practices, and a new ecosystem-based fisheries management (EBFM) paradigm has emerged. As part of this approach, selective fishing is widely encouraged in the belief that nonselective fishing has many adverse impacts. In particular, incidental bycatch is seen as wasteful and a negative feature of fishing, and methods to reduce bycatch are implemented in many fisheries. However, recent advances in fishery science and ecology suggest that a selective approach may also result in undesirable impacts both to fisheries and marine ecosystems. Selective fishing applies one or more of the "6-S" selections: species, stock, size, sex, season, and space. However, selective fishing alters biodiversity, which in turn changes ecosystem functioning and may affect fisheries production, hindering rather than helping achieve the goals of EBFM. We argue here that a "balanced exploitation" approach might alleviate many of the ecological effects of fishing by avoiding intensive removal of particular components of the ecosystem, while still supporting sustainable fisheries. This concept may require reducing exploitation rates on certain target species or groups to protect vulnerable components of the ecosystem. Benefits to society could be maintained or even increased because a greater proportion of the entire suite of harvested species is used.
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Atlantic cod (Gadus morhua) is a large, cold-adapted teleost that sustains long-standing commercial fisheries and incipient aquaculture. Here we present the genome sequence of Atlantic cod, showing evidence for complex thermal adaptations in its haemoglobin gene cluster and an unusual immune architecture compared to other sequenced vertebrates. The genome assembly was obtained exclusively by 454 sequencing of shotgun and paired-end libraries, and automated annotation identified 22,154 genes. The major histocompatibility complex (MHC) II is a conserved feature of the adaptive immune system of jawed vertebrates, but we show that Atlantic cod has lost the genes for MHC II, CD4 and invariant chain (Ii) that are essential for the function of this pathway. Nevertheless, Atlantic cod is not exceptionally susceptible to disease under natural conditions. We find a highly expanded number of MHC I genes and a unique composition of its Toll-like receptor (TLR) families. This indicates how the Atlantic cod immune system has evolved compensatory mechanisms in both adaptive and innate immunity in the absence of MHC II. These observations affect fundamental assumptions about the evolution of the adaptive immune system and its components in vertebrates.
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Hunters often target species that require resource investment disproportionate to associated nutritional rewards. Costly signalling theory provides a potential explanation, proposing that hunters target species that impose high costs (e.g. higher failure and injury risks, lower consumptive returns) because it signals an ability to absorb costly behaviour. If costly signalling is relevant to contemporary 'big game' hunters, we would expect hunters to pay higher prices to hunt taxa with higher perceived costs. Accordingly, we hypothesized that hunt prices would be higher for taxa that are larger-bodied, rarer, carnivorous, or described as dangerous or difficult to hunt. In a dataset on 721 guided hunts for 15 North American large mammals, prices listed online increased with body size in carnivores (from approximately $550 to $1800 USD/day across the observed range). This pattern suggests that elements of costly signals may persist among contemporary non-subsistence hunters. Persistence might simply relate to deception, given that signal honesty and fitness benefits are unlikely in such different conditions compared with ancestral environments in which hunting behaviour evolved. If larger-bodied carnivores are generally more desirable to hunters, then conservation and management strategies should consider not only the ecology of the hunted but also the motivations of hunters.
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Abstract. Exotic species—especially predators—are a potential threat to native species communities and ecosystems worldwide. Introduced exotic species may cause changes in anti-predator behaviour of prey species, thus affecting prey individuals’ time allocations for other crucial behaviours such as feeding and locating mates. To test this hypothesis, we investigated shoaling behaviour of the pygmy halfbeak, Dermogenys collettei, comparing populations with different degrees of exposure to an exotic predator (Cichla orinocensis). Contrary to predictions, halfbeaks exhibited shoaling behaviour in a low predation, forest stream habitat but not in a high predation, more open stream habitat. We argue that behavioural differences are likely driven by competition for resources leading to reduced shoaling, highlighting how costs and benefits of group-living affect population-level shoaling tendencies. Dermogenys collettei also did not increase shoaling behaviour when exposed to C. orinocensis, suggesting that adaptive behavioural responses to immediate predation risk are absent. We discuss the implications of our results for the conservation of small native freshwater fishes in Singapore and Malaysia and identify further areas of research on predator-prey interactions between exotic predators and indigenous aquatic fauna.
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Worldwide depletion of fish stocks has led fisheries managers to become increasingly concerned about rebuilding and recovery planning. To succeed, factors affecting recovery dynamics need to be understood, including the role of fisheries-induced evolution. Here we investigate a stock’s response to fishing followed by a harvest moratorium by analyzing an individual-based evolutionary model parameterized for Atlantic cod Gadus morhua from its northern range, representative of long-lived, late-maturing species. The model allows evolution of life-history processes including maturation, reproduction, and growth. It also incorporates environmental variability, phenotypic plasticity, and density-dependent feedbacks. Fisheries-induced evolution affects recovery in several ways. The first decades of recovery were dominated by demographic and density-dependent processes. Biomass rebuilding was only lightly influenced by fisheries-induced evolution, whereas other stock characteristics such as maturation age, spawning stock biomass, and recruitment were substantially affected, recovering to new demographic equilibria below their preharvest levels. This is because genetic traits took thousands of years to evolve back to preharvest levels, indicating that natural selection driving recovery of these traits is weaker than fisheries-induced selection was. Our results strengthen the case for proactive management of fisheries-induced evolution, as the restoration of genetic traits altered by fishing is slow and may even be impractical.
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Evolutionary effects of fishing can have unwanted consequences diminishing a fishery’s value and sustainability. Reserves, or no-take areas, have been proposed as a management tool for reducing fisheries-induced selection, but their effectiveness for migratory species has remained unexplored. Here we develop an eco-genetic model to predict the effects of marine reserves on fisheries-induced evolution under migration. To represent a stock that undergoes an annual migration between feeding and spawning grounds, we draw model parameters from Atlantic cod (Gadus morhua) in the northern part of its range. Our analysis leads to the following conclusions: (i) a reserve in a stock’s feeding grounds, protecting immature and mature fish alike, reduces fisheries-induced evolution, even though protected and unprotected population components mix on the spawning grounds; (ii) in contrast, a reserve in a stock’s spawning grounds, protecting only mature fish, has little mitigating effects on fisheries-induced evolution and can sometimes even exacerbate its magnitude; (iii) evolutionary changes that are already underway may be difficult to reverse with a reserve; (iv) directly after a reserve is created or enlarged, most reserve scenarios result in yield losses; and (v) timescale is very important: short-term yield losses immediately after a reserve’s creation can give way to long-term gains.
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Together with life-history and underlying physiology, the behavioural variability among fish is one of the three main trait axes that determines the vulnerability to fishing. However, there are only a few studies that have systematically investigated the strength and direction of selection acting on behavioural traits. Using in situ fish behaviour revealed by telemetry techniques as input, we developed an individual-based model (IBM) that simulated the Lagrangian trajectory of prey (fish) moving within a confined home range (HR). Fishers exhibiting various prototypical fishing styles targeted these fish in the model. We initially hypothesised that more active and more explorative individuals would be systematically removed under all fished conditions, in turn creating negative selection differentials on low activity phenotypes and maybe on small HR. Our results partly supported these general predictions. Standardised selection differentials were, on average, more negative on HR than on activity. However, in many simulation runs, positive selection pressures on HR were also identified, which resulted from the stochastic properties of the fishes' movement and its interaction with the human predator. In contrast, there was a consistent negative selection on activity under all types of fishing styles. Therefore, in situations where catchability depends on spatial encounters between human predators and fish, we would predict a consistent selection towards low activity phenotypes and have less faith in the direction of the selection on HR size. Our study is the first theoretical investigation on the direction of fishery-induced selection of behaviour using passive fishing gears. The few empirical studies where catchability of fish was measured in relation to passive fishing techniques, such as gill-nets, traps or recreational fishing, support our predictions that fish in highly exploited situations are, on average, characterised by low swimming activity, stemming, in part, from negative selection on swimming activity.
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Two and a half decades ago, macroecology was initially characterized as the study of the division of food and space among species on continents. Since then, macroecological research has been expanded to include the study of relationships between organisms and their environments by characterizing and explaining patterns of abundance, distribution, and diversity. Importantly, macroecology was meant to counter what was seen as increasingly reductionist and specialized approaches in ecology and to examine the roles and interactions among ecological and evolutionary explanations for large-scale patterns using integrated analyses. Macroecological investigations occur at spatial scales increasingly relevant to biodiversity and ecosystem functioning research, global change dynamics, and fisheries. This chapter highlights patterns and interactions among key macroecological variables within aquatic ecosystems, identifies approaches to overcome the challenge of identifying processes underlying macroecological patterns, reviews the emerging traits-based focus on aquatic functional diversity, and describes ecological and evolutionary effects of selective fisheries on aquatic ecosystem functioning.
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Paradigms of sustainable exploitation focus on population dynamics of prey and yields to humanity but ignore the behavior of humans as predators. We compared patterns of predation by contemporary hunters and fishers with those of other predators that compete over shared prey (terrestrial mammals and marine fishes). Our global survey (2125 estimates of annual finite exploitation rate) revealed that humans kill adult prey, the reproductive capital of populations, at much higher median rates than other predators (up to 14 times higher), with particularly intense exploitation of terrestrial carnivores and fishes. Given this competitive dominance, impacts on predators, and other unique predatory behavior, we suggest that humans function as an unsustainable "super predator," which—unless additionally constrained by managers—will continue to alter ecological and evolutionary processes globally. Copyright © 2015, American Association for the Advancement of Science.
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Are recreational fisheries resilient to harvest or prone to collapse? This paper reviews research published since that question was posed by Post et al. (2002, Fisheries 27, 6–17). A number of patterns and processes have been identified that suggest understanding the risk of collapse requires knowledge of the fishing effort response, degree of depensation in the fishery and the life history of the harvested species. Processes involving the behaviour of fish, behaviour of anglers and management responses to declining quality can all impact the degree of resilience of recreational fisheries and their risk of collapse. The spatial context of an individual fishery can be important as they are often embedded in lake districts and joined by mobile anglers so their local dynamics are not independent from other fisheries. Typical regulations that restrict the behaviour of individual anglers in open‐access fisheries can provide some resilience but cannot prevent collapse if the fishing effort is too high. Many uncertainties remain related to the occurrence and intensity of the key processes and therefore adopting an adaptive experimental management approach might be the most useful approach to minimise the risk of collapse in recreational fisheries.
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The artificial selection of traits in wildlife populations through hunting and fishing has been well documented. However, despite their rising popularity, the role that artificial selection may play in non‐extractive wildlife activities, for example, recreational feeding activities, remains unknown. If only a subset of a population takes advantage of human‐wildlife feeding interactions, and if this results in different fitness advantages for these individuals, then artificial selection may be at work. We have tested this hypothesis using a wild fallow deer population living at the edge of a capital city as our model population. In contrast to previous assumptions on the randomness of human‐wildlife feeding interactions, we found that a limited non‐random portion of an entire population is continuously engaging with people. We found that the willingness to beg for food from humans exists on a continuum of inter‐individual repeatable behaviour; which ranges from risk‐taking individuals repeatedly seeking and obtaining food, to shyer individuals avoiding human contact and not receiving food at all, despite all individuals having received equal exposure to human presence from birth and coexisting in the same herds together. Bolder individuals obtain significantly more food directly from humans, resulting in early interception of food offerings and preventing other individuals from obtaining supplemental feeding. Those females that beg consistently also produce significantly heavier fawns (300–500 g heavier), which may provide their offspring with a survival advantage. This indicates that these interactions result in disparity in diet and nutrition across the population, impacting associated physiology and reproduction, and may result in artificial selection of the begging behavioural trait. This is the first time that this consistent variation in behaviour and its potential link to artificial selection has been identified in a wildlife population and reveals new potential effects of human‐wildlife feeding interactions in other species across both terrestrial and aquatic habitats. Human‐wildlife feeding interactions are increasingly popular, yet the role that they may play in the artificial selection of behavioural traits in wildlife populations remains unexplored. This work begins to unravel the complex dynamics and impacts of these interactions, opening up new dimensions for human‐wildlife studies.
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We examine alternative hypotheses for the decline of 20 cod Gadus morhua stocks in the North Atlantic. The year of the lowest observed biomass of spawners did not correspond to low juvenile survival for the cohorts that should have contributed to the stock in that year. However, fishing mortality was very high for the years preceding the collapse. The collapse of the cod stocks was not caused by a lack of resilience at low population abundance because all spawners were able to produce many potential replacements at low population size. We show that as populations collapsed, fishing mortality increased until the populations were reduced to very low levels. We conclude that increased fishing mortality caused the population declines, and often the collapses, of the cod stocks.
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In their Policy Forum (“Managing evolving fish stocks,” 23 November 2007, p. [1247][1]), C. Jorgensen et al. propose evolutionary impact assessments (EvoIAs) as a general tool for managing evolving resources. The basis for their proposal is that fisheries-induced evolution (FIE) is the most
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The ability of natural selection to drive local adaptation has been appreciated ever since Darwin. Whether human impacts can impede the adaptive process has received less attention. We tested this hypothesis by quantifying natural selection and harvest selection acting on a freshwater fish (pike) over four decades. Across the time series, directional natural selection tended to favour large individuals whereas the fishery targeted large individuals. Moreover, non-linear natural selection tended to favour intermediate sized fish whereas the fishery targeted intermediate sized fish because the smallest and largest individuals were often not captured. Thus, our results unequivocally demonstrate that natural selection and fishery selection often acted in opposite directions within this natural system. Moreover, the two selective factors combined to produce reduced fitness overall and stronger stabilizing selection relative to natural selection acting alone. The long-term ramifications of such human-induced modifications to adaptive landscapes are currently unknown and certainly warrant further investigation.
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Evolutionary impact assessment is a framework for quantifying the effects of harvest-induced evolution on the utility generated by fish stocks. CREDIT: N. KEVITIYAGALA/SCIENCE Darwinian evolution is the driving process of innovation and adaptation across the world’s biota. Acting on top of natural selection, human-induced selection pressures can also cause rapid evolution. Sometimes such evolution has undesirable consequences, one example being the spreading resistance to antibiotics and pesticides, which causes suffering and billion-dollar losses annually (1). A comparable anthropogenic selection pressure originates from fishing, which has become the main source of mortality in many fish stocks, and may exceed 1
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This essay comments on recent research on Darwinian fisheries science and on the future development of this field. From a practical point of view, the key question is: how fast are evolutionary changes caused by fishing happening? To answer this question, there is a need to understand intensities of selection generated by fishing, heritabilities and genetic correlations of the traits under selection, and whether the rates of change in traits predicted from this information are consistent with the changes observed. Although there is little doubt about the existence of phenotypic change in life-history traits of exploited fish stocks, there are few direct estimates of selection differentials caused by fishing. Results that are available, together with the relatively low heritabilities of life-history traits, suggest that the evolution caused by fishing occurs at a modest rate, and is likely to need a decadal time scale to be clearly observable. Given the pressing need for attention to fisheries in the short term, measures to control the longer-term evolutionary impact of fishing are most likely to be adopted if they also help to meet short-term objectives of management. With this in mind, the essay mounts a defence of large, old fish, the presence of which would be beneficial to stocks in the short term, and the conservation of which would set in motion selection for improved growth in the longer term.
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It is now clear that fished populations can fluctuate more than unharvested stocks. However, it is not clear why. Here we distinguish among three major competing mechanisms for this phenomenon, by using the 50-year California Cooperative Oceanic Fisheries Investigations (CalCOFI) larval fish record. First, variable fishing pressure directly increases variability in exploited populations. Second, commercial fishing can decrease the average body size and age of a stock, causing the truncated population to track environmental fluctuations directly. Third, age-truncated or juvenescent populations have increasingly unstable population dynamics because of changing demographic parameters such as intrinsic growth rates. We find no evidence for the first hypothesis, limited evidence for the second and strong evidence for the third. Therefore, in California Current fisheries, increased temporal variability in the population does not arise from variable exploitation, nor does it reflect direct environmental tracking. More fundamentally, it arises from increased instability in dynamics. This finding has implications for resource management as an empirical example of how selective harvesting can alter the basic dynamics of exploited populations, and lead to unstable booms and busts that can precede systematic declines in stock levels.
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Fishing of natural populations increases the variability of fish abundance. A unique data set from the southern California Current has allowed an evaluation of three hypotheses for why that should be so.
  • G Mertz
  • R A Myers
Mertz, G. & Myers, R. A. Can. J. Fish Aquat. Sci. 55, 478–484 (1998).
  • E Dzierzak
  • N A Speck
Dzierzak, E. & Speck, N. A. Nature Immunol. 9, 129–136 (2008).
  • H M Eilken
  • S.-I Nishikawa
  • T Schroeder
Eilken, H. M., Nishikawa, S.-I. & Schroeder, T. Nature 457, 896–900 (2009).
  • S M Carlson
Carlson, S. M. et al. Ecol. Lett. 10, 512–521 (2007).
  • T L Huber
  • V Kouskoff
  • H J Fehling
  • J Palis
  • G Keller
Huber, T. L., Kouskoff, V., Fehling, H. J., Palis, J. & Keller, G. Nature 432, 625–630 (2004).
  • J B Gurdon
  • D A Melton
Gurdon, J. B. & Melton, D. A. Science 322, 1811–1815 (2008).
  • H I Browman
Browman, H. I. et al. Science 320, 47 (2008).
  • K Choi
  • M Kennedy
  • A Kazarov
  • J C Papadimitriou
  • G Keller
Choi, K., Kennedy, M., Kazarov, A., Papadimitriou, J. C. & Keller, G. Development 125, 725–732 (1998).
  • N C Stenseth
  • T Rouyer
Stenseth, N. C. & Rouyer, T. Nature 452, 825–826 (2008).
  • S I Nishikawa
Nishikawa, S. I. et al. Immunity 8, 761–769 (1998).
  • A Kuparinen
  • Merilä
Kuparinen, A. & Merilä, J. Science 320, 47–48 (2008).
  • T Yokomizo
Yokomizo, T. et al. Genes Cells 6, 13–23 (2001).
  • A C Zovein
Zovein, A. C. et al. Cell Stem Cell 3, 625–636 (2008).
  • R A Myers
Myers, R. A. et al. Mar. Ecol. Prog. Ser. 138, 293–308 (1996).
  • D S Falconer
  • T F Mackay
Falconer, D. S. & Mackay, T. F. C. Introduction to Quantitative Genetics (Longman, 1996).
  • C Lancrin
Lancrin, C. et al. Nature 457, 892–895 (2009).
  • M F De Bruijn
de Bruijn, M. F. et al. Immunity 16, 673–683 (2002).
  • M J Chen
  • T Yokomizo
  • B M Zeigler
  • E Dzierzak
  • N A Speck
Chen, M. J., Yokomizo, T., Zeigler, B. M., Dzierzak, E. & Speck, N. A. Nature 457, 887–891 (2009).
  • C N K Anderson
Anderson, C. N. K. et al. Nature 452, 835–839 (2008).
  • C Jørgensen
Jørgensen, C. et al. Science 378, 1247–1248 (2007).