Harvest Quotas Research Articles

Past, present and future of fishery management on one of the world’s last remaining pristine great lakes: Great Bear Lake, Northwest Territories, Canada

Great Bear Lake, Northwest Territories, Canada supports important sport and aboriginal-subsistence fisheries and is among the last remaining pristine great lakes of the world. The lake’s unique ecology is characterized by a harsh subarctic climate, low productivity and species diversity, and high intraspecific diversity of lake trout. These aspects in combination with geographical remoteness present special challenges to the management of two exceptionally different fisheries. The history of its management has not been well documented or reviewed; therefore, our objectives in this paper were to summarize the history and status of Great Bear Lake’s fisheries and their management, and to identify gaps in knowledge, future challenges, and actions required to meet those challenges. Prior to 1970, management goals for the lake had not been established formally, and harvest numbers and biological characteristics of fish were unknown. To reduce data gaps, creel surveys, gillnet assessments, fish tagging, and subsistence monitoring were implemented. During the 1980s, Canada established the management goal of conserving a high quality sport fishery, while protecting aboriginal access to the subsistence fishery. On the basis of assessment data, lodge harvest quotas, lodge guest capacity limits, individual angler harvest limits, and angler licensing were among the management actions taken to achieve that goal. Since 2005, decision making has been guided by the “water heart,” a management plan for Great Bear Lake. Management has since evolved into a complex co-management system among aboriginal, territorial, and federal governments. Changes in regulations, sport trophy and tourism industries, subsistence resource use, and social and cultural norms and practices contributed to changes in the Great Bear Lake fishery and its management. In the future, anthropogenic and climate change are the two main challenges facing co-management of the lake’s resources. We recommend the adoption of an ecosystem approach to management, establishment of a fishery technical committee, reformulation of the current plan, explicit commitment to evaluation, conducting community-based monitoring, and development and use of a joint strategic plan among co-managers to describe how to interact and implement the Great Bear Lake management plan.

Climate change vulnerability and adaptation in resource dependent communities: a case study from West Greenland

This paper reports on a project conducted over 4 field seasons in the town of Qeqer - tar suaq in West Greenland, identifying and examining vulnerability and adaptation to climate change. Drawing upon semi-structured interviews with community members (n = 132), key informant interviews with policy makers (n = 10), and analysis of secondary sources, we docu- mented changes in sea ice regimes, temperatures, and wind. Vulnerabilities to these changes are primarily associated with hunting and fishing. Constrained access and availability of key wildlife resources and increased harvesting dangers are affecting individuals and households closely linked to the subsistence economy. Adaptations that are being employed combine both reactive and anticipatory interventions autonomously undertaken at an individual and household level, including traveling to new fishing grounds, seeking alternative sources of income when harvest- ing activities are not possible, preparing for the unexpected, and an increased reliance on boat transport. The role of women in supporting male hunters/fishers, knowledge of environmental conditions, the existence of alternative sources of income, diversity and flexibility in harvesting, and willingness to alter livelihoods, are important factors that underpin adaptive capacity. Institu- tional constraints, however, are a major impediment to adaptation and have reduced the flexibility which has enabled historic adaptation to changing conditions. While alternative income sources are increasingly important in light of recent stresses, occupational hunters face restrictions on money-earning from non-harvesting activities, and various harvesting quotas fail to reflect recent alterations in species availability with changing climatic conditions. More broadly, hunting regu- lations have contributed to the erosion of the moral economy of harvesting and have weakened social networks, increasing vulnerability to projected future changes in climate.

Exploited for pets: the harvest and trade of amphibians and reptiles from Indonesian New Guinea

Over-exploitation of wildlife is a significant threat to global biodiversity, but addressing the sustainability of harvests can be difficult when trade is conducted illegally. The wildlife trade is driven chiefly by consumer demand, largely in developed nations (but increasingly in Asia), and more species are traded to meet international demand for pets than for any other purpose. We surveyed traders of amphibians and reptiles in the Indonesian provinces of Maluku, West Papua and Papua between September 2010 and April 2011. We recorded 5,370 individuals representing 52 species collected solely for the pet trade. At least 44 % were either fully protected or had not been allocated a harvest quota, making their harvest and trade illegal. Approximately half were listed within the Convention on International Trade in Endangered Species of Wild Fauna and Flora. Trade operates via a complex chain, with hunters receiving little income compared to middlemen and exporters. Examination of Indonesian harvest quotas for amphibians and reptiles suggests limited knowledge of species distributions, with quotas often set for species in provinces where they do not occur. Illegal trade is due, partly, to an inadequate understanding of the species being traded and is facilitated by poor monitoring and enforcement at key trade hubs. As a first step to combatting illegal trade, and to better understand the effects of harvest on wild populations, we recommend the need for increased monitoring and enforcement, improving the knowledge base of species traded and educating consumers about the effects their demand for pets has on these species.

Carcass weight, condition and reproduction of wild boar harvested in north‐western Poland

Wild boar were studied in the Gryfino-Mysliborz region of Poland where high-density populations inflict great damage to farmlands. The reproductive tracts from carcasses bagged during the 2008/2009 hunting season were analysed for numbers of corpora lutea and embryos. The objective was to determine the reproduction rate in a wild boar population having access to high-protein food in cereal monocultures. Among the wild boar harvested (n = 165), 35.8% were piglets, 53.9% were yearlings and 10.3% were older boar. Among the 105 females examined, 60.9% did not reproduce. The presence of corpora lutea was found in 22.9% of females, whereas 16.2% of females had embryos. In piglets, 11.5% of females had corpora lutea and embryos. These proportions were higher in yearlings (41.1%) and in older females (45.4%). The average number was 6.3 of corpora lutea per ovulating female, with an average litter size of 5.9 embryos. The farrowing period was found to last from December to August. The proportion of piglets in the harvest quota must be increased to prevent these animals from boosting reproduction. Offering high-protein fodder in baiting stations and feeding sites should be banned.

Preferences for government enforcement of a common pool harvest quota: Theory and experimental evidence from fishing communities in Colombia

We examine individual harvesters' preferences for government enforcement of a quota imposed on the exploitation of a common pool resource. We develop a model of Nash behavior by identical risk neutral harvesters to explain individual equilibrium preferences for enforcement of an efficient harvest quota. If the quota is not enforced well, we demonstrate that individual harvesters will always prefer increased enforcement—either increased monitoring or increased penalties—of the quota. We conduct a test of this theoretical result with data from framed common pool resource experiments conducted in artisanal fishing communities in three regions of Colombia. Subjects were given the opportunity to express their preferences for enforcement by voting on two levels of enforcement of a harvest quota, with and without communication. The two enforcement strategies involved the same probability that the government would audit individual harvesters, but differed in the level of the penalty for noncompliance. Contrary to theory, individuals voted for the lower inefficient penalty about 80% of the time and groups implemented this weaker enforcement strategy over 90% of the time. Giving subjects the opportunity to vote on the enforcement strategy did not lead to more efficient harvests, nor did allowing subjects to communicate before voting.

Determination of long-tailed macaque’s (Macaca fascicularis) harvesting quotas based on demographic parameters

Santosa Y, Kusmardiastuti, Kartono AP, Rahman DA. 2012. Determination of long-tailed macaque’s (Macaca fascicularis) harvesting quotas based on demographic parameters. Biodiversitas 13: 79-85. Harvesting quota of long-tailed macaques for breeding purpose should be set up based on demographic parameters. The objectives of this research were to determine demographic parameters affecting the set up of harvesting quota and the sustainable harvesting quotas of long-tailed macaque in Indonesia. This study was expected to provide useful information for consideration of setting up harvesting quotas for long-tailed macaque in Indonesia. This study was conducted in November 2009-Januari 2010 using the equation of Q = Nt-MVP. The results showed varied harvesting quotas for different age classes of long-tailed macaque with an average number of 5 for infant males, 3 for infant females, 5 for juvenile males, 4 for juvenile females, 6 for sub-adult males, 8 for sub-adult females and 2 for adult males. The dominant variable determining quota wassurvival rate.

Temporal quota corrections based on timing of harvest in a small game species

Theoretical models have shown that the effect of removing a given proportion of the population can be profoundly different if the harvest takes place late in the season compared to early. We explore the effect of these differences using theoretical models based on the concept of demographic value and empirical data on seasonal patterns of natural mortality risk in two contrasting populations of willow ptarmigan in Norway. Based on the theoretical models, we found that changes in the timing of harvest have a much stronger effect in populations with relatively low annual survival compared to populations characterized by longevity typical for species with slow life histories. Also, the timing of harvest is more influential in cases with constant mortality hazards compared to a situation with density-dependent natural mortality. Empirical data from two study populations of willow ptarmigan showed large deviations from the theoretical predictions of models with both constant and density-dependent mortality hazards. There were also large differences in both the temporal pattern and magnitude of annual survival between the two ptarmigan populations (54 vs 26% annual survival). Site differences illustrate the importance of knowledge of both the magnitude and temporal pattern of natural mortality hazard to be able to correctly predict the effect of changing the timing of harvest in a population. In the two ptarmigan populations, we show how harvest quotas can be adjusted in accordance to the empirical estimates of natural mortality risk and how this determines the effects of shifting from harvesting early to late in the annual cycle.

Conservation in Sustainable-Use Tropical Forest Reserves

trialspecies,therelativemeritsofdifferentapproachesto ensure the long-term persistence of those species remain highly contentious. Most would agree, however, that both establishing protected areas and exercising some form of restraint on extraction of forest resources are among the most effective of all viable conservation measures. Deforestation, wildfires, logging, and hunting are among the leading drivers of species losses in tropical forests, and de facto or de jure protection from these threats can be conferred by either effective enforcement of regulations or physical remoteness. Attempts to assess conservation success of protected areasatlargescaleshaverestedprimarilyonconventional use of remote sensing to quantify spatial or temporal differences in rates of change in land cover due to deforestation and wildfires, rather than on empirical demographic or community-level metrics (Gaston et al. 2008). Q2 However, the former approaches fail to detect most types of subcanopy anthropogenic disturbances that also result, directly or indirectly, in species losses (Peres et al. 2006). Moreover, the effects of habitat loss and degradation on population extirpations and declines are nonlinear, so vegetation cover alone is rarely a robust proxy for the viability of terrestrial biotas. Remotesensing data show vast tracts of apparently intact tropical forests, but in reality levels of hunting and other forms of extraction in these areas are often unsustainable (Peres & Lake 2003). Fundamental questions yet to be answered include whether ostensibly intact protected areas retain full complements of forest species and how the extent of cryptic patterns of disturbance is related to human population density in both protected and unprotected areas. I considered the global to regional emergence of sustainable-use reserves, emphasizing the world’s largest tropical forest region, Amazonia. Sustainable-use reserves often have intermediate levels of disturbance, so I examined the degree of use of natural resources by resident communities and used human population density as a proxy for level of extraction. In both protected and unprotected areas, I also estimated responses of game vertebrate assemblages to hunting on the basis of the relative biomassextractedfromasubsetoftheforestfauna.Iused analysesofcovariance(ANCOVA)toexaminetheassociationbetweenhumandensityandgamebiomassharvested across different reserve categories. Finally, I considered the long-term capacity of sustainable-use forest reserves to maintain populations of all resident species.

ON THE IMPULSIVE BEVERTON–HOLT EQUATION AND EXTINCTION CONDITIONS IN POPULATION DYNAMICS

Abstract This paper is devoted to investigate extinction and nonextinction conditions of the extended Beverton–Holt equation (BHE) for dynamics of populations in Ecology when potential discontinuities at sampling points are included in the model. The proposed model is described by means of four sequences of parameters. Two of them are the intrinsic growth rate and the carrying capacity sequences which are included in the basic BHE model. The other two ones, namely, the harvesting (i.e., the hunting or fishing quota) and the internal consumption (which can include positive and negative migrations in the considered population habitat) sequences are included to parameterize the model discontinuities. Such discontinuities are related to impulses in the corresponding continuous‐time logistic equation. The obtained results establish how the harvesting quota and/or the internal consumption has to be fixed to guarantee the population nonextinction or, eventually, its extinction. Finally, some controllability results related to the search of a carrying capacity sequence such that the solution of the proposed impulsive BHE tracks a reference one are obtained.

Genetic assessment of paternity and relatedness in a managed population of cougars

AbstractUnderstanding the social dynamics of large carnivores is critical to effective conservation and management planning. We made the first attempt to delineate both paternity and relatedness for a population of cougar (Puma concolor) using microsatellite data. We analyzed a long‐term genetic dataset collected from a hunted population in the Garnet Mountains of western Montana. We assigned paternity for 62.5% of litters sampled using both exclusion and likelihood analyses. Attempts at reconstructing unsampled paternal genotypes resulted in delineating possible sires for 8 more litters. Sires were on average younger than reported for males involved in pairings assessed via field data in other cougar populations. Although most mating pairs were unrelated, 5 of 17 pairings involved cougars with levels of relatedness corresponding to half‐sibling and full‐sibling or parent offspring relationship (r = 0.215–0.575). Relatedness among adult and subadult males was higher than relatedness levels among adult and subadult females. Relatedness among males in the Garnet population differed from patterns hypothesized to occur under male‐biased dispersal theories for cougars. The long‐term impact of the turnover of resident cougars in hunted populations is still unclear and warrants additional research. Our results highlight the utility of monitoring cougar demographic parameters using a combination of genetic and field data that in turn may assist managers with determining cougar harvest quotas or strategies, harvest seasons, sustainable harvest, and the appropriate management level of cougar populations. © 2011 The Wildlife Society.

Ecological attributes and trade of white-lipped pythons (Genus Leiopython) in Indonesian New Guinea

White-lipped pythons (WLP) (Genus Leiopython) have been collected from the wild in Indonesian New Guinea and exported for the pet trade since at least 1977. Despite the long duration of trade and recent taxonomic work recognising six different species, virtually nothing is known of the trade dynamics or ecology of these species. Surveys of wildlife traders in Indonesian New Guinea and measurement of 122 WLP provides the first information on trade and ecological attributes of the two most commonly traded species, L. albertisii and L. hoserae. Both species exhibit broadly similar ecological attributes; however, L. hoserae has a longer and wider head than L. albertisii. WLP prey mainly on mammals, although smaller snakes were found to feed on lizards. Reproduction appears to be seasonal with oviposition and hatching occurring in the summer months between December and March. Most trade was in L. albertisii and although traders differentiated between the two species on the basis of colour, both were traded under the name L. albertisii. Examination of CITES export data revealed that in 2004 Indonesia exceeded the government-allocated harvest quota of wild individuals. Although this quota was apparently not exceeded in other years, the results of this study suggest that the unmonitored domestic pet trade and the potential for misdeclaration of wild-caught individuals for export may account for many more snakes than are recorded.

Distribution, ecological attributes and trade of the New Guinea carpet python (Morelia spilota) in Indonesia

Carpet pythons (Morelia spilota) are medium-sized non-venomous snakes inhabiting most of continental Australia and a small area of New Guinea. They have been relatively well studied in Australia, but little is known about the New Guinea population, even though it is harvested and exported from Indonesia for the international pet trade. In total, 281 locality records were compiled for two distinct populations south of latitude 7°S in Papua New Guinea and the Indonesian province of Papua. Traders in Papua collected 274 carpet pythons (most of which were recently hatched neonates) for the pet trade. Data from a sample of 174 individuals revealed little sexual dimorphism in any traits, although males appear to grow larger than females despite females maturing at greater lengths. Fecundity was high (average 17 eggs) and reproduction was highly seasonal, with hatching in December and January. Harvest quotas for the province of Papua were exceeded in all years between 2000 and 2009 due to 50% of the national quota being allocated to West Papua province where this species is yet to be recorded. The present study provides distribution, trade and ecological information to inform conservation management of this species in Indonesia.

Effects of harvest and climate on population dynamics of northern bobwhites in south Florida

Context Hunting-related (hereafter harvest) mortality is assumed to be compensatory in many exploited species. However, when harvest mortality is additive, hunting can lead to population declines, especially on public land where hunting pressure can be intense. Recent studies indicate that excessive hunting may have contributed to the decline of a northern bobwhite (Colinus virginianus) population in south Florida. Aims This study aimed to estimate population growth rates to determine potential and actual contribution of vital rates to annual changes in population growth rates, and to evaluate the role of harvest and climatic variables on bobwhite population decline. Methods We used demographic parameters estimated from a six-year study to parameterise population matrix models and conduct prospective and retrospective perturbation analyses. Key results The stochastic population growth rate (λS = 0.144) was proportionally more sensitive to adult winter survival and survival of fledglings, nests and broods from first nesting attempts; the same variables were primarily responsible for annual changes in population growth rate. Demographic parameters associated with second nesting attempts made virtually no contribution to population growth rate. All harvest scenarios consistently revealed a substantial impact of harvest on bobwhite population dynamics. If the lowest harvest level recorded in the study period (i.e. 0.08 birds harvested per day per km2 in 2008) was applied, λS would increase by 32.1%. Winter temperatures and precipitation negatively affected winter survival, and precipitation acted synergistically with harvest in affecting winter survival. Conclusions Our results suggest that reduction in winter survival due to overharvest has been an important cause of the decline in our study population, but that climatic factors might have also played a role. Thus, for management actions to be effective, assessing the contribution of primary (e.g. harvesting) but also secondary factors (e.g. climate) to population decline may be necessary. Implications Reducing hunting pressure would be necessary for the recovery of the bobwhite population at our study site. In addition, an adaptive harvest management strategy that considers weather conditions in setting harvest quota would help reverse the population decline further.

Management of the Piankatank River, Virginia, in Support of Oyster (Crassostrea virginica,Gmelin 1791) Fishery Repletion

The Piankatank River is a trap-type estuary on the western shore of Chesapeake Bay that has been managed for seed oyster production since 1963. Market oyster production in the river is minimal. Repletion efforts include shell planting and seed removal. We describe sequential changes in population demographics and habitat in relation to repletion activities on eight Piankatank River public oyster reefs from 1998 through 2009. Two reef groups (northern and southern) may be distinguished by density (oysters/m 2 ), biomass (g dry tissue weight), and shell volume (L/m 2 ) data. Age-at-length relationships were estimated from demographic data using a quadratic model. Observed mortality rates were high, and age 3+ oysters were essentially absent. A strong recruitment signal was observed in 1999 and 2002. Between 1998 and 2009, about 30% of the live oysters in the river were harvested as seed, corresponding to ;7.5% of the total shell base in an average year. Typically, for every 5 bushels of shell planted, 1 bushel of seed was harvested (20% return). Even with shell planting (;10 L/m 2 /y), the river shell budget showed a deficit with respect to the accretion rate required to balance sea level rise and natural degradation processes. During the study period, the mean river recruit-to-stock ratio was ;4. The unusual and consistently high recruit-to-stock ratios suggest that management for modest continuous seed removal may be accomplished without shell planting. Annual stock assessment to identify low recruitment years is recommended as a method to adjust annual seed harvest quotas.

Precision beats interval: appropriate monitoring efforts for management of a harvested Eurasian lynx Lynx lynx population

AbstractAdaptive management of wild populations requires good knowledge of the population status. The main way to evaluate management performance is through recurring surveys, which often also serve as a decision basis for harvest quotas. We evaluated the effect of different survey reliabilities and frequencies during 1‐4 years on management performance using a stochastic age and stage‐specific population model for an Eurasian lynx Lynx lynx population. As a proxy for management performance, we looked at the proportion of time that the population remained within a preferred interval, the proportion of time with no harvest, the average harvest number and the total number of surveys during the 50‐year period in the simulation. In general, management performance increased with increased monitoring accuracy. More interestingly, a more reliable survey performed less frequently performed better than a less reliable survey performed every year. The management performance was not perfect even with complete knowledge of the population size at the survey, as annual variation in reproduction and survival between the survey (decision based on year t) and harvest (performed in year t+1) sometimes cause the population to be outside the preferred interval. If financial resources are limited, we recommend managers to minimise the error in the survey rather than to increase the frequency of surveys.

Density‐Dependent Sex Ratio Adjustment and the Allee Effect: A Model and a Test Using a Sex‐Changing Fish

Positive density dependence (i.e., the Allee effect; AE) often has important implications for the dynamics and conservation of populations. Here, we show that density-dependent sex ratio adjustment in response to sexual selection may be a common AE mechanism. Specifically, using an analytical model we show that an AE is expected whenever one sex is more fecund than the other and sex ratio bias toward the less fecund sex increases with density. We illustrate the robustness of this pattern, using Monte Carlo simulations, against a range of body size-fecundity relationships and sex-allocation strategies. Finally, we test the model using the sex-changing polygynous reef fish Parapercis cylindrica; positive density dependence in the strength of sexual selection for male size is evidenced as the causal mechanism driving local sex ratio adjustment, hence the AE. Model application may extend to invertebrates, reptiles, birds, and mammals, in addition to over 70 reef fishes. We suggest that protected areas may often outperform harvest quotas as a conservation tool since the latter promotes population fragmentation, reduced polygyny, a balancing of the sex ratio, and hence up to a 50% decline in per capita fecundity, while the former maximizes polygyny and source-sink potential.

Live coral trade impacts on the mushroom coral Heliofungia actiniformis in Indonesia: Potential future management approaches

The poorly regulated aquarium trade in live corals poses yet another threat to fragile coral reef ecosystems. The Indonesian authorities routinely allocate some of the highest trade quotas in South Sulawesi to Heliofungia actiniformis despite a lack of data on the impacts of current collection practices on this species. Semi-structured interviews with fishermen and in situ surveys revealed a size-selective fishery towards small polyps. This resulted in a shift of size-frequency distributions, and reduced overall abundances at harvested sites. Total mortality rates calculated using a catch curve approach at harvested sites were significantly higher compared to those known from unharvested sites for polyps sized 0–11 cm. Recorded exploitation rates were 0.1 and 0.7 for polyps sized 0–4 cm and 4–11 cm respectively. The application of a utility per recruit approach, calculated with a Thompson and Bell model, revealed maximum potential economic yield to occur at a size of 5 cm, corresponding to an age of 5 years. This is 5 years before the attainment of reproductive maturity, and 15 years before the attainment of maximum biomass yield per recruit. A predictive model indicated the need for a 5 cm size limit to curb economic overfishing, and protect attached anthocauli stalks capable of maintaining the trade through continued asexual reproduction. In addition, a reduction of exploitation rates for polyps in the 4–11 cm size bracket to 0.5 is urgently needed. Calculations reveal that this would in fact be possible without lowering current profits. Achieving long term sustainability will in addition to a reduction of harvest quotas necessitate an effective protection of spawning stocks through stricter enforcement of existing marine protected areas.

Modeling the impacts of hunting on the population dynamics of red howler monkeys ( Alouatta seniculus)

Overexploitation of wildlife populations occurs across the humid tropics and is a significant threat to the long-term survival of large-bodied primates. To investigate the impacts of hunting on primates and ways to mitigate them, we developed a spatially explicit, individual-based model for a landscape that included hunted and un-hunted areas. We used the large-bodied neotropical red howler monkey ( Alouatta seniculus) as our case study species because its life history characteristics make it vulnerable to hunting. We modeled the influence of different rates of harvest and proportions of landscape dedicated to un-hunted reserves on population persistence, population size, social dynamics, and hunting yields of red howler monkeys. In most scenarios, the un-hunted populations maintained a constant density regardless of hunting pressure elsewhere, and allowed the overall population to persist. Therefore, the overall population was quite resilient to extinction; only in scenarios without any un-hunted areas did the population go extinct. However, the total and hunted populations did experience large declines over 100 years under moderate and high hunting pressure. In addition, when reserve area decreased, population losses and losses per unit area increased disproportionately. Furthermore, hunting disrupted the social structure of troops. The number of male turnovers and infanticides increased in hunted populations, while birth rates decreased and exacerbated population losses due to hunting. Finally, our results indicated that when more than 55% of the landscape was harvested at high (30%) rates, hunting yields, as measured by kilograms of biomass, were less than those obtained from moderate harvest rates. Additionally, hunting yields, expressed as the number of individuals hunted/year/km 2, increased in proximity to un-hunted areas, and suggested that dispersal from un-hunted areas may have contributed to hunting sustainability. These results indicate that un-hunted areas serve to enhance hunting yields, population size, and population persistence in hunted landscapes. Therefore, spatial regulation of hunting via a reserve system may be an effective management strategy for sustainable hunting, and we recommend it because it may also be more feasible to implement than harvest quotas or restrictions on season length.

Population structure and demographic history of Genypterus blacodes using microsatellite loci

Three loci microsatellites were used to determine genetic variability and population structure at 15 locations within three zones where Genypterus blacodes is being fully exploited in Chilean waters. A total of 209 individuals were used: 77 from Cuadra Meulin (CM), 65 from the northern Magellan Strait (NMS), and 67 from the southern Magellan Strait (SMS). The genetic variability found, measured as observed heterozygosity, was Ho = 0.841 ± 0.016. The levels of population subdivision found were F st = 0.0032 ( p = 0.687 ± 0.004) and R st = 0.0059 ( p = 0.160 ± 0.003). Both the F st and R st values were near zero, with non-significant probability values, indicating that the three studied zones were not significantly different. The demographic history analyses did not exhibit significant differences between the observed and expected diversity, under a scenario of reduced effective population size. Therefore, the results obtained in the present study show that there was no population level genetic differentiation of G. blacodes between the analyzed zones in austral Chilean waters (between 41 and 57° S), confirming the presence of a single genetic stock. This result should be included in the management strategy by which harvest quotas are set, and used to improve the application of government management policies, with the aim of increasing the sustainability of this important fishery resource.

Predicting survival, reproduction and abundance of polar bears under climate change

Polar bear ( Ursus maritimus) populations are predicted to be negatively affected by climate warming, but the timeframe and manner in which change to polar bear populations will occur remains unclear. Predictions incorporating climate change effects are necessary for proactive population management, the setting of optimal harvest quotas, and conservation status decisions. Such predictions are difficult to obtain from historic data directly because past and predicted environmental conditions differ substantially. Here, we explore how models can be used to predict polar bear population responses under climate change. We suggest the development of mechanistic models aimed at predicting reproduction and survival as a function of the environment. Such models can often be developed, parameterized, and tested under current environmental conditions. Model predictions for reproduction and survival under future conditions could then be input into demographic projection models to improve abundance predictions under climate change. We illustrate the approach using two examples. First, using an individual-based dynamic energy budget model, we estimate that 3–6% of adult males in Western Hudson Bay would die of starvation before the end of a 120 day summer fasting period but 28–48% would die if climate warming increases the fasting period to 180 days. Expected changes in survival are non-linear (sigmoid) as a function of fasting period length. Second, we use an encounter rate model to predict changes in female mating probability under sea ice area declines and declines in mate-searching efficiency due to habitat fragmentation. The model predicts that mating success will decline non-linearly if searching efficiency declines faster than habitat area, and increase non-linearly otherwise. Specifically for the Lancaster Sound population, we predict that female mating success would decline from 99% to 91% if searching efficiency declined twice as fast as sea ice area, and to 72% if searching efficiency declined four times as fast as area. Sea ice is a complex and dynamic habitat that is rapidly changing. Failure to incorporate climate change effects into population projections can result in flawed conservation assessments and management decisions.