Aggressive Harvesting Research Articles

Pathogen‐mediated selection and management implications for white‐tailed deer exposed to chronic wasting disease

Abstract Pathogens can cause host extinction, affect population dynamics and influence natural selection. Host susceptibility to pathogens can vary by species, demographics and genetics which affect epizootic and population dynamics, ultimately determining population trends and evolution. Chronic wasting disease (CWD), a fatal neuro‐degenerative prion disease of cervids, has varying host susceptibility conferred by polymorphisms of the prion protein gene (PRNP) at codon 96 for white‐tailed deer Odocoileus virginianus. Deer with the homozygous Glycine allele (96GG) are most susceptible and a single Serine allele (96GS/96SS) reduces the risk of infection and mortality. We developed epizootiological models that demonstrate CWD infection and disease‐associated mortality were higher for the more susceptible (96GG) genotype; and, infection was higher for males than females. We used population models to evaluate future shifts in genotype frequencies under alternative harvest and infection rate scenarios. Genetic shifts towards less susceptible genotypes were predicted as CWD prevalence increased during the course of an outbreak. This further increased CWD prevalence, and likely environmental contamination from prion shedding, due to longer incubation periods. Alternative harvest management strategies directly influenced CWD prevalence and spread, the rate of genetic selection and deer population growth. Synthesis and applications. We show that chronic wasting disease (CWD) transmission varied by sex, age class and PRNP genotype, and that CWD disease‐associated mortality varied by genotype. Together, these forces lead to CWD‐mediated genetic selection for a white‐tailed deer population. We predict that genetic selection pressure increases when hunter harvest pressure is lowered, and conversely, increasing hunter harvest can reduce genetic selection rates of antlered deer. Our results support the control of CWD prevalence by aggressive harvest of adult males, because they have the highest infection rates. Our results have strong implications for evolution, disease ecology, geographical spread, disease mitigation and cervid population management.

Fisheries management under incomplete information by optimal stochastic control and Hidden Markov Model filter

This paper deals with mathematical modelling of strategies in harvesting of fish populations. Since too aggressive harvesting may have severe consequences, a cautious control of the process is called for. The determination of optimal harvesting based on the biomass size is made even more challenging since there is considerable uncertainty in the estimation of the stock size, the so-called incomplete information problem.Fishery management is in this paper established as an optimal control problem for a model based on nonlinear stochastic differential equations, with economic performance as objective. The so-called certainty equivalence principle, by which the estimate is used for the purposes of optimal feedback control as if it were the certain value of the state variable, is adopted. Markov controls are identified by solving the stationary Hamilton-Jacobi-Bellman equation. State estimates are obtained by a Hidden Markov Model filter, where the forward Kolmogorov equation governs the temporal evolution of estimates with the uncertain quantities. Fishery profit over time as economic performance is computed by Monte Carlo simulations, in order to compare the performances of the strategies considering control rules and precautionary approach.Two control rules in harvest policy – harvest control rule and effort control rule – are compared, with respect to their robustness given the uncertainty. The effort control rule produces a significantly higher cumulated profits, and is less sensitive to the uncertainty in stock assessment present in the system. Moreover, a precautionary approach taking the uncertainty associated with biomass estimates into account, can be achieved via quantile estimators. This approach produces an economic gain by making a more appropriately cautious decision, and leads to sustainable harvesting of fish resources.

The coloniality of private forest lands: Harvesting levels, land grants, and neoliberalism on Vancouver Island

This paper examines how colonial land grants and the neoliberalization of forestry policy have enabled an aggressive harvesting regime on a massive tract of private land on Vancouver Island, British Columbia. We detail the intensity of industrial logging activities of three forestry companies—Island Timberlands, TimberWest, and Western Forest Products—on private land on Vancouver Island. We draw on 11 years of harvesting volume records from the public British Columbia Harvest Billing System to examine the rate of harvest on private land by the aforementioned companies. The paper maps the harvesting volumes we report in relation to forest land ownership and the boundaries of land grants to demonstrate the enduring settler‐colonial character of fee simple forest land and industrial harvesting activities. We argue that neoliberal legislation introduced in 2003 deregulated forestry operations on private lands, facilitating the harvesting regimes we detail. We further suggest that settler‐colonial enclosures set in motion by the Esquimalt & Nanaimo Railway Company land grants starting in 1884 have been foundational to the establishment and management of private forest lands on Vancouver Island and continue to represent barriers for Indigenous communities as they assert their rights and title to private forest land.

Limb salvage after aneurysmal degeneration of a cryopreserved vein allograft: Searching the autologous veins of the arm is worth the effort

We hereby report a case of limb salvage involving a 64-year-old man who was hospitalized with ischemic foot ulcers for two months. Endarterectomy with patching and stenting of the left iliofemoral artery failed. A composite bypass of two segments of the endarterectomized superficial femoral artery and a cryopreserved saphenous vein graft was implanted one week later. On day 4 postoperatively, an infection (Staphylococcus epidermidis and Pseudomonas aeruginosa) was treated empirically with antibiotics. Four months later, the femoro-tibial bypass thrombosed and the patency was restored by thrombolysis. The aneurysmal cryopreserved vein was excised. Iterative complications followed and final success was attained after implantation of autologous cephalic and basilic veins. Four years later, this femoro-tibial is still patent. After a gross observation, the explant was dissected and the most significant sections were processed for histology, followed by analyses in scanning electron microscopy, light microscopy and transmission electron microscopy. The explanted specimen showed a smooth flow surface proximally but a severe distortion distally, with an accumulation of poorly organized mural thrombi. The wall of the arterialized vein was accompanied with an important inflammatory reaction. The degradation of the collagen structure was evidenced in TEM. The fibrils of collagen were still individualized but were fragmented and did not display parallelly. The regular banding was preserved. The presence of Pseudomonas aeruginosa was shown inside the wall of the homologous vein. In case of sepsis, the most aggressive antibiotic treatments cannot fully eliminate the bacteremic colonizations within the wall of an alternative conduit. The cephalic and basilic autologous veins are proved to be preferable in absence of the autologous saphenous vein. The amputation was prevented and four years later the bypass is still patent. This is an outstanding result based upon the comorbidities of the patient. The most aggressive harvesting shall be recommended. This patient represented a considerable challenge and the clinical result is highly gratifying: the search for the autologous cephalic and basilic veins proved to be worth the effort.

Spatial Renewable Resource Extraction under Possible Regime Shift

AbstractHow will countries harvesting mobile natural resources react to the possibility of regime shift? We address the non‐cooperative exploitation of a migratory renewable resource in the presence of possible regime shift that affects its movement. Motivated by the anticipated effects of climate change, we model a regime shift that will alter the spatial movement patterns of the resource at some point in the future. We develop a stochastic spatial bioeconomic model to address the effects of this class of regime shift on non‐cooperative harvest decisions made by decentralized owners such as countries exploiting a migratory fish or other natural resource stock. We find that the threat of a future shift modifies the standard “golden rule”, and may induce more aggressive harvest everywhere, irrespective of whether the owner will be advantaged or disadvantaged by the shift. We also identify conditions under which the threat of regime shift induces owners to reduce harvest rates in advance of the shift. Our analysis suggests that different property rights structures (single ownership vs common property) or heterogeneous growth can give rise to previously unexplored incentives and can even reverse conventional wisdom about how countries will react to the prospect of future environmental change.

Spatial renewable resource extraction under possible regime shift

How will countries harvesting mobile natural resources react to the threat of regime shift? We address the non-cooperative exploitation of a migratory renewable resource in the presence of possible regime shift that a_ects its movement. Motivated by the anticipated effects of climate change, we model a regime shift that will alter the spatial movement patterns of the resource at some point in the future. We develop a stochastic spatial bioeconomic model to address the effects of this class of regime shift on non-cooperative harvest decisions made by decentralized owners such as countries exploiting a migratory fish or other natural resource stock. We find that the threat of a future shift modifies the standard golden rule and may induce more aggressive harvest everywhere, irrespective of whether the owner will be advantaged or disadvantaged by the shift. We also identify conditions under which the threat of regime shift induces owners to reduce harvest rates in advance of the shift. Our analysis suggests that different property rights structures (single ownership vs common property) or heterogeneous growth can give rise to previously unexplored incentives and can even reverse conventional wisdom about how countries will react to the prospect of future environmental change

Optimal harvesting strategy based on rearrangements of functions

We study the problem of optimal harvesting of a marine species in a bounded domain, with the aim of minimizing harm to the species, under the general assumption that the fishing boats have different capacities. This is a generalization of a result of Kurata and Shi, in which the boats were assumed to have the same maximum harvesting capacity. For this generalization, we need a completely different approach. As such, we use the theory of rearrangements of functions. We prove existence of solutions, and obtain an optimality condition which indicates that the more aggressive harvesting must be pushed toward the boundary of the domain. Furthermore, we prove that radial and Steiner symmetries of the domain are preserved by the solutions. We will also devise an algorithm for numerical solution of the problem, and present the results of some numerical experiments.

The performance and trade-offs of alternative harvest control rules to meet management goals for U.S. west coast flatfish stocks

U.S. federal fisheries managers are mandated to obtain optimum yield while preventing overfishing. However, optimum yield is not well defined and the concept of maximum sustainable yield (MSY) has often been applied to provide an upper bound for the optimum yield value, but determining the MSY, identifying the relative biomass that produces MSY and the associated fishing rate required (FMSY) is difficult. The Pacific Fishery Management Council, which manages groundfish stocks off the U.S. west coast, has employed proxy targets in lieu of species-specific estimates of MSY, BMSY, and FMSY. The proxy targets are life history specific, with flatfish stocks managed using a target BPROXY of 0.25 of unfished biomass and a harvest control rule that applies an exploitation rate equal to a spawner-per-recruit harvest rate of F0.30, with a linear reduction of catch to zero if the stock falls below 5% of unfished biomass (BLIMIT). A management strategy evaluation was performed to explore the performance of the current harvest control rule applied to flatfish stocks to meet management goals, along with alternative harvest control rules that explore varying the values for BPROXY,BLIMIT, and FSPR. Each of the harvest control rules explored maintained stocks at or near BPROXY when stock-recruit steepness was 0.85 or greater, with very low probabilities of reducing relative biomass below a minimum stock size threshold (set at 0.50 BPROXY of each harvest control rule). The most aggressive harvest control rule, which applied a BPROXY of 0.20 and a target harvest rate of F0.25, led to fishing rates that exceeded the operating model FMSY values for low steepness (0.75), reducing the stock below BPROXY with catches exceeding MSY. Trade-offs exist among alternative harvest control rules where the more aggressive harvest control rules resulted in higher average catches, but with an increase in the average annual variation in catches and a decrease probability of the relative biomass being with 10% of the BPROXY. The trade-offs among the performance metrics and alternative harvest control rules coupled with the risk to the resource across a range of life histories should be carefully considered by fishery managers when selecting a harvest control rule that will meet the goals of management.

WHY INCREASED UNCERTAINTY MAY LEAD TO MORE RISKY BEHAVIOR

AbstractThe purpose of this article is to investigate circumstances under which it may be optimal to deliberately harvest a fish stock to extinction applying a stochastic surplus growth model. It is known from the literature that deliberate extinction may result when there is critical depensation or when the discount rate is high compared to the intrinsic growth rate. Here it is shown that deliberate extinction may also be optimal when the degree of stochasticitry is high even with zero discounting. A high degree of stochasticity may have the same effect as critical depensation even though it is not present in the biological model. In other words, high uncertainty, instead of leading to more conservative harvesting as is usually expected, in this model result in more aggressive harvesting and more risky behavior. The main message is therefore always to try to keep the stock well above any critical limit.

Serotonin and Social Norms

How do people sustain resources for the benefit of individuals and communities and avoid the tragedy of the commons, in which shared resources become exhausted? In the present study, we examined the role of serotonin activity and social norms in the management of depletable resources. Healthy adults, alongside social partners, completed a multiplayer resource-dilemma game in which they repeatedly harvested from a partially replenishable monetary resource. Dietary tryptophan depletion, leading to reduced serotonin activity, was associated with aggressive harvesting strategies and disrupted use of the social norms given by distributions of other players’ harvests. Tryptophan-depleted participants more frequently exhausted the resource completely and also accumulated fewer rewards than participants who were not tryptophan depleted. Our findings show that rank-based social comparisons are crucial to the management of depletable resources, and that serotonin mediates responses to social norms.

Optimum Operating Parameters for a Rotary Drum Shaker for Harvesting Jatropha curcas L.

The objective of this study was to determine the optimum amplitude and frequency of operation for the rotary shaker drum of an experimental canopy shaker used for harvesting Jatropha curcas L. A constrained optimization technique that required the removal of yellow and brown fruits to be as high as possible and the removal of green fruits to be as low as possible was used to determine the optimum operating parameters. The optimum operating condition that retained 90% of the green fruits on the plant was found to be an amplitude of 7.2 cm (2.9 in.) and a frequency of 2.4 Hz. The removal efficiencies for yellow and brown fruits were found to be 75.8% and 80.2%, respectively, for this operating condition. When the objective function of the optimization procedure was changed to limit the amount of green fruits harvested to be no more than 10% of the total fruits harvested to ensure oil quality, the optimum operating parameters were found to be an amplitude of 8.0 cm (3.2 in.) and a frequency of 3.2 Hz for the shaker drum. The removal efficiencies for the yellow and brown fruits for this operating condition were 83% and 89%, respectively. An evaluation of plant damage revealed that no serious damage occurred to Jatropha curcas L. plants when the vibratory shaker drum was operated even under aggressive harvesting conditions that involved an amplitude of 7.6 cm and a frequency of 5.0 Hz.

Household and local forest impacts of Morocco's argan oil bonanza

ABSTRACTMorocco's argan oil is now the most expensive edible oil in the world. Growing high-value argan markets have sparked a bonanza of argan activity. NGOs, international and domestic development agencies, and argan oil cooperatives have promoted the win–win aim of simultaneously benefiting locals and the argan forest. We test this win–win claim by surveying households before and after rapid appreciation in argan prices. The argan boom has benefited some rural households. Those well positioned to benefit increased their goat herds more than other households, which bodes poorly for forest impacts, and were more likely to send their girls to secondary school. While locals are keeping their goats out of argan trees during the harvest, they may also be resorting to more aggressive harvesting techniques. The boom has made households vigilant guardians of fruit on their own trees, but has not incited investments in longer term tree and forest health.

Gluteal Augmentation With Cryopreserved Fat

Gluteal augmentation with autologous fat is becoming a standard ancillary procedure for sculpting the buttock area. The high rate of resorption due to aggressive harvesting techniques or inadequate injection procedures often leads to repeated treatments. Currently, several techniques for storing fat by controlled freezing and thawing procedures can guarantee a high rate of cell viability, similar to that obtained with fresh tissue. This allows surgeons to compile fat tissue available for future repeat injections, decreasing additional costs and morbidity for patients. The authors describe a case of gluteal augmentation with cryopreserved fat in a 42-year-old man.

Intergenerational valuation of fisheries resources can justify long-term conservation: a case study in Atlantic cod (Gadus morhua)

Where the conventional model of discounting advocates aggressive harvest policies, intergenerational discounting could have been used to render the historic gross overfishing of Atlantic cod (Gadus morhua) economically unappealing compared with a more conservative long-term strategy. Under these discounting approaches, we compare the historic harvest trend from 1985 (and projected postcollapse earnings) with theoretical optimal harvest profiles determined by an ecosystem model. The optimal scenarios generate less initial harvest than the historic profile but maintain the resource and provide greater yields over the long term. At a discount rate equal to market interest, we demonstrate that it was more economic under conventional valuation to harvest the cod stock to collapse than it would have been to sustain the population. However, under intergenerational valuation, the sustainable optimal scenarios outperform the actual harvest profile. Application of conventional discounting by fishing consortiums may be partly to blame for depletion, yet management fell short of even that ideal.

An enzyme‐based method for the rapid determination of sucrose, glucose and fructose in sugar beet roots and the effects of impact damage and postharvest storage in clamps

AbstractA high‐throughput enzyme‐coupled assay is described for the determination of sucrose, glucose and fructose in sugar beet roots. This method is sensitive, rapid and inexpensive and has been used to highlight the increases in sucrose loss following root stresses such as freezing or aggressive harvesting. Sugar beet roots lose 12.5% of their sucrose following an episode of impact damage greater than 2 J, rising to 19.7% loss after 8 J, with concurrent increases in glucose and fructose. Increases in glucose and fructose are particularly pronounced following a period of clamp storage (up to 2.3 and 3.3 µg mg−1 fresh weight, respectively).© 2001 Society of Chemical Industry

An Investigation of Wound Healing in Sugar Beet Roots Using Light and Fluorescence Microscopy

Following impact, wound healing was investigated in roots of sugar beet using fluorescence microscopy in conjunction with a conventional lignin test. Samples of sugar beet roots were harvested at different stages of development and impacted in the laboratory with a falling bolt delivering 1–4 Joules. A response in the form of deposition of brown material, presumed to be melanin, along the outer and inner walls of cells at the wound surface was observed within 3 d of impact. This material eventually became granular in appearance. Formation of a ligno-suberized boundary layer from cells present at the time of impact first occurred in 16-week-old roots 9 d after impact. Intensity of calcofluor fluorescence supported the findings made using light microscopy. As wound healing progressed with time, the intensity of calcofluor fluorescence declined, demonstrating interference by wound healing products with calcofluor binding. Aggressive harvest and subsequent storage dramatically reduced calcofluor fluorescence indicating that this dye may have potential value in the assessment of tissue damage.

COEXISTENCE OR EXCLUSION IN A COMPETITIVE COMMON‐POOL FISHERY: A REVISIONIST VIEW

ABSTRACT. One of the earliest applications of game theory to renewable resource modeling was Colin Clark's analysis, in 1980, of the competitive exploitation of a common‐pool resource. His model described the dynamics of a single Gordon‐Schaeffer fish stock, being harvested non‐cooperatively by two or more independently managed fleets. He showed that aggressive harvesting by all fleets (a Nash equilibrium) would lead to stock drawdown to a level which would successively eliminate all of the less efficient harvesters. Furthermore, when the fleets were closely matched, the survivor(s) of this aggressive competition would be forced, by the threat of competitors' reentry, to hold the stock in its severely degraded state, and hence to harvest at only marginal profitability. This outcome has often been compared to the open access “tragedy of the commons.” and to the outcome of the well‐known “prisoners' dilemma” game.In this article I will argue that, for closely matched fleets, a more likely outcome is that the fleets will tacitly agree, without overt communication, to focus simultaneously on a specific set of coordinated policies which will permit their continuing coexistence and profitable operation. This policy profile also forms a Nash equilibrium, one which is secured by the mutual ability of the fleets to quickly recognize and credibly punish any unilateral deviations from the anticipated actions. Thus the dynamic harvesting game more nearly resembles the repeated prisoners' dilemma than it does the classical single stage version.

INFLUENCE OF CULTIVAR, PLANTING TECHNIQUE AND HARVEST DURATION ON ASPARAGUS YIELD

Crowns and tranplants of `Martha Washington' (MW) and `Jersey Prince' (JP) asparagus were planted in 1985. Plots were harvested for 0,2,4 weeks (traditional schedule); 1,2,6 weeks (moderate harvest pressure); or 2,4,8 weeks (severe harvest pressure) in 1986, 1987, and 1988, respectively. All plots were harvested for 8 weeks after 1988. An AOV was performed to test the main effects of cv, planting technique and harvest schedules and interactions on early and total season yield of large, medium-sized and total spears. MW produced a significantly higher yield of both early and total season large spears than JP in all years. Total yields did not differ between cvs. There was no significant effect of planting technique on yield in any year. Harvest schedules imposed in the first 3 years had significant long term effects on yield. Although severe harvest pressure produced larger yields than the other schedules in 1986-1988, from 1989-1991 yields were lowest in the severe harvest pressure plots. The traditional harvest schedule produced similar yields to the moderate pressure schedule. There were no consistent interactions between cultivar, planting technique and harvest schedule These data indicate that a slightly more aggressive harvest schedule in the early years of an asparagus planting would not have long term deterimental effect on yield. However, severe cutting pressure can reduce yields compared to traditional cutting schedules for at least 3 years after initial harvest pressure treatment