A bioeconomic model for estimating the optimal level of deer and tag sales

This paper presents a dynamic model that determines the optimal number of deer hunting permit sales, subject to the objective of maximizing the discounted economic benefits stream from both the consumptive and nonconsumptive uses of deer. This bioeconomic model integrates economic benefits estimated using the dichotomous choice contingent valuation method with biological growth constraints on deer. Using a hunting zone in California as a case study, the model found that the optimal levels of buck hunting permits sold should change on a rotational basis over time and that the current practice of not selling doe hunting permits for that zone is non optimal.     

Potential ecological and economic impacts of sea lice from farmed salmon on wild salmon fisheries

This paper examines the possible ecological and economic effects of sea lice from salmon farms on wild salmon populations and fisheries. A bioeconomic model is developed incorporating an age-structured population dynamics model of wild pink and chum salmon with mortality caused by farm-derived sea lice. Our model incorporates capture fisheries under two management policy scenarios. Results suggest that the ecological and economic effects are minor when the sea lice induced mortality rate is below 20%, while they can be severe if the mortality is greater than 30%. Sea lice have greater ecological and economic impacts on pink salmon than on chum salmon. The impact of farm lice epizootics on wild salmon is greater under a fixed exploitation rate than under a target escapement policy. As a result, a precautionary principle should be adopted, and appropriate management schemes and policy strategies should be developed to minimize these effects.     

关于林权抵押贷款贷款期限的探讨

从林农经济利益角度出发,运用经济分析和数学推理的方法,引入生物生长模型,在分析林木蓄积、林木资产价值和贷款资金的时间价值基础上,确立合理的采伐时间和最佳的采伐时间,进而确立可行的贷款期限和最低贷款期限、最佳的贷款期限。以马尾松为例,进行实际计算分析,得出可行的贷款年限为8～19年,8年为最低贷款年限,19年为最佳的贷款年限。     

木竹制品价值链构成与林权改革影响分析——浙江安吉案例

采用价值链分析法,选定开展了林权改革的浙江省安吉县为例,针对其木、竹制品价值链上的培育和加工环节设计调查问卷并分别访谈。调查数据显示,木制品和竹制品价值链上从原料培育及初加工直至产成品各环节成本利润对比悬殊。分析其中的影响因素后发现,采伐政策是造成木、竹加工业培育和初加工环节利润悬殊的主要影响因素之一。     

Effectiveness of harvest strategies in achieving multiple management objectives in a multispecies fishery

Fisheries management is characterised by multiple objectives, some of which may be complementary, while others may require trade‐offs between outcomes. Balancing these objectives is made more complex in the case of multispecies and multigear fisheries. In this paper, we develop a bioeconomic model that captures the key elements of such a fishery to test a range of potential harvest strategies to provide insights into how economic target reference points could lead to both desirable and undesirable management outcomes (e.g. discards). The model is developed as a long‐run optimisation model to identify target reference points to achieve multispecies maximum economic yield, and a dynamic recursive optimisation model, which includes more realistic representation of fishers’ behaviour, such as discards and trading of under‐caught species quotas. The potential economic, social and ecological impacts are evaluated using data envelopment analysis (DEA). The results suggest that the use of proxy target reference points can result in short‐term economic benefits at the cost of slower stock recovery and higher discarding. Limiting the number of species subject to quota controls may also prove beneficial in multispecies fisheries, while ensuring quota markets are efficient is likely to produce benefits irrespective of the harvest strategy adopted.     

Trajectories in human domination of ecosystems: Human appropriation of net primary production in the Philippines during the 20th century

The “human appropriation of net primary production” (HANPP) has been suggested as a comprehensive indicator to measure impacts of human land use on ecosystems. It accounts for (a) human-induced changes in biological productivity and (b) biomass harvest. This study presents an analysis of aboveground HANPP in the Philippines between 1910 and 2003, a period characterized by massive deforestation and increases in land use intensity and biomass extraction. Results show a steep increase of aboveground HANPP from just below 35% of potential productivity in 1910 to slightly above 60% in 1970 and constant values since then. Large-scale changes in land cover and agricultural practices were the main direct determinants of this trajectory in HANPP. Remarkably, HANPP grew at much slower pace than population did: While the amount of NPP appropriated by humans doubled throughout the period, population increased by a factor ten. Increasing efficiency in terms of biomass extraction per unit of area, relying on ever-increasing inputs, and changes in the nation's physical biomass trade balance were of major importance for this difference in growth rates. In the coming decades, the Philippines will have to face the challenge to meet increases in biomass demand without putting even higher strains on the ecosystems.     

A Bioeconomic Analysis of the Northern Baltic Salmon Fishery: Coexistence versus Exclusion of Competing Sequential Fisheries

We develop a bioeconomic model of the northern Balticsalmon fishery that takes into account thesimultaneous harvest of wild and reared salmon. Weassess the optimal harvest allocation between thecommercial offshore, inshore, and estuary fisheries,and the recreational river fishery that sequentiallyharvest the salmon stock. We restrict the solution tospawning stocks sufficient to preserve the wildsalmon. Empirical results suggest closure of theoffshore and inshore fisheries. Optimal managementenhances the wild stock, and results in substantialeconomic gains to the fishery. Current fisheryregulation improves the performance of the fisheryover open access, but fails to utilize the fullproductive potential of the resource.     

《电梯原理与维修》课程教改探讨

根据课程特点和高职学生的实际情况,文章对《电梯原理与维修》课程提出了六点教改意见。     

Valuing Mangrove-Fishery Linkages – A Case Study of Campeche, Mexico

This paper explores the value of mangrove systems as a breeding and nursery habitat for off-shore fisheries, focusing on mangrove-shrimp production linkages in Campeche State, Mexico. We develop an open access fishery model to account explicitly for the effect of mangrove area on carrying capacity and thus production. From the long-run equilibrium conditions of the model we are able to establish the key parameters determining the comparative static effects of a change in mangrove area on this equilibrium. We then estimate empirically the effects of changes in mangrove area in the Laguna de Terminos on the production and value of shrimp harvests in Campeche over 1980–90. Our findings suggest that mangroves are an important and essential input into the Campeche shrimp fishery, but that the low levels of deforestation between 1980 and 1990 mean that the resulting losses to the shrimp fishery are still comparatively small. Over-exploitation of the fishery due to open access conditions remains the more pervasive threat, and without better management any long-run benefits of protecting mangrove habitat are likely to be dissipated.     

沙县杉木人工林经验收获表的编制及应用研究

对杉木人工林的单位面积蓄积量、平均胸径、平均树高以及株数的生长模型采用民理查德方程来进行计算，并结合了相关公式编制了一份收获表，收获表在经检验后表明据有一定的科学依据，非常适宜，对林分生长收获的预估和小班资源数据更新有着非常重要的作用，文中最后给出了应用经验收获表进行生长收获预估的实例。