Stochastic bycatch, informational asymmetry, and discarding

The existing literature (i) examines bycatch and discard behavior in a static framework and (ii) treats bycatch as a deterministic process uniform across vessels. Using a dynamic representative agent model in a two-stock resource, this paper explores strategic interactions between a social planner and two groups of harvesters, one of which imposes a stochastic “technological externality” (bycatch) on the other. In addition to limitations on entry and the number of trips taken in each industry, three bycatch control instruments are compared to the unconstrained case: taxes, trip limits, and value-based quotas. Implementation and enforcement costs aside, taxes dominate both types of quota, and value limits outperform trip limits by eliminating one type of discarding. In simulations, relative performance depends upon variance in the bycatch process, differences in the ex vessel prices of stocks, relative efficiency of the harvester types, and fixed costs on the trip and industry margins.     

乡村文化记忆资源的“文—旅”协同评价模型与应用——以苏州金庭镇为例

乡村文化记忆资源是乡村“文—旅”协同的链接点。基于文化记忆理论从文化信息层、物质载体层与社会行为层解析其内涵和协同框架,构建“文—旅”空间协调度、文化记忆连续性和旅游市场认同度的协同评价模型,以苏州金庭镇为例进行实证分析。结果表明:（1）时间格局上,旅游景点与生活生产类空间关联性不断提升,与功能象征类空间依赖减弱,与社会表征类和精神意识类空间关系有所降低但维持高度耦合水平。（2）空间格局上,与生活生产类空间呈极核带状格局,与其余三类空间呈现一核多极格局。（3）旅游景点与生活生产类空间协同关系从“文—旅”空间协调度、文化记忆连续性转向旅游市场认同度为主导,其余空间以“文—旅”空间协调度为主导。（4）影响协同关系的机制包括记忆延续与文化交融、空间优化与旅游融合和社会支持与政策保障等。研究结论可为乡村旅游地的文化振兴和文旅融合提供理论指导和应用模式。     

Mate sampling behaviour of black grouse females (Tetrao tetrix)

We studied female mate sampling behaviour in lekking black grouse (Tetrao tetrix). Females mainly visited males occupying territories in the centre of the lek with relatively large territories. They were also more likely to visit males that had high attendance. The same factors were also correlated with male mating success. A multiple regression model including these factors explained more of the variance in female visits per male (53%) than in mating success (33%). The pattern of female sampling conformed with a pool comparison (best-of-n) tactic. Such a tactic is expected if the costs of sampling are low. Females of high body mass visited more males than lighter females, however, which indicates that females may vary in their search tactics and suggests that there may be search costs. The existence of costs is further suggested by the fact that if the mate from a previous year was still present, females always mated with the same male in the following year. Though search costs were not measured directly, our findings suggest that some costs are negligible (e.g. energetic exhaustion or predation) whereas others (timing of mating) may be more important.     

Addressing social attitudes toward lethal control of wildlife in national parks

The extraordinary population growth of certain ungulate species is increasingly a concern in agroforestry areas because overabundance may negatively affect natural environments and human livelihoods. However, society may have negative perceptions of killing wildlife to reduce their numbers and mitigate damage. We used an online survey that included a choice experiment to determine Spanish citizens’ (n = 190) preferences toward wildlife population control measures related to negative effects of ungulate overabundance (negative impacts on vegetation and other wildlife species and disease transmission to livestock) in 2 agroforestry national parks in Spain. We used latent-class and willingness-to-pay in space models to analyze survey results. Two percent of respondents thought a national park should have no human intervention even if lack of management may cause environmental degradation, whereas 95% of respondents favored efforts to reduce damage caused by overabundant ungulate species. We estimated human well-being losses of survey respondents when sustainable effects of deer overabundance on the environment became unsustainable effects and well-being gains when sustainable effects transitioned to no visible effects. We found that the type of wildlife-control program was a very relevant issue for the respondents; indirect control in which killing was avoided was the preferred action. Sixty-six percent of respondents agreed with the option of hunters paying for culling animals to reduce ungulate impacts rather than management cost coming out of taxes, whereas 19% of respondents were against this option and willing to pay for other solutions in national parks. Our results suggest that killing wildlife in national parks could be a socially acceptable tool to manage overabundance problems in certain contexts, but it could also generate social conflicts.     

Female oviposition-site preference and egg hatching success in the damselfly Calopteryx splendens xanthostoma

By removing males and controlling the rate of water flow past oviposition patches in an experimental area, we showed that female Calopteryx splendens xanthostoma preferred to oviposit in fast flowing water rather than slow flowing water. A series of manipulations revealed the fitness benefits to females for this preference: eggs placed in fast-flowing water developed significantly faster and showed significantly lower mortality than eggs placed in slow-flowing water. A major factor determining this difference was the deposition and growth of encrusting algae which prevented the successful hatching of eggs in slow-flowing water.     

Polygyny in the red-winged blackbird: do females prefer monogamy or polygamy?

Five hypotheses have been proposed to explain polygyny in the red-winged blackbird (Agelaius phoeniceus). We categorized the hypotheses into three groups based on female preference for unmated versus monogamously mated males: (1) the “polygyny threshold” model, “sexy son” hypothesis and the “asynchronous settlement” model, which assume that females prefer unmated males to mated males on breeding situations of homogeneous quality; (2) the “neutral mate choice” hypothesis, which assumes that females have no preference; and (3) the “cooperative female choice” model, which assumes that females prefer monogamously mated males to unmated males. We tested the direction of female preference in two field experiments. In both experiments, newly settling females were given a choice of two adjacent territories, one defended by an unmated male and the other by a monogamously mated male. Male mating status was randomized with respect to the variation in territory quality and male quality. Early in the breeding season, significantly more females settled with the unmated males than with the mated males. Although more females settled with the unmated males than with the mated males late in the breeding season, the difference was no longer significant. Female settlement late in the season appeared to be related to the tenure of the resident females: the new females avoided territories where the resident females were in early stages of their nesting, but settled on territories where the resident females were in late stages. The pattern of female settlement shows that females prefer unmated males to mated males. The preference is consistent with the polygyny threshold model, sexy son hypothesis and the asynchronous settlement model, and inconsistent with the neutral mate choice hypothesis and the cooperative female choice model. For this reason, the latter two hypotheses are unlikely to explain the occurrence of polygyny in our population of red-winged blackbirds. Received: 1 December 1994 / Accepted after revision: 28 October 1995     

Armaments and ornaments in the rock sparrow: a possible dual utility of a carotenoid-based feather signal

Females often base their mating preferences on male sexual secondary traits that are used to settle contests among males. Such traits are likely to be honest indicators of male quality if they are constantly used during costly male–male agonistic interactions. Carotenoid signals have been shown to work as a handicap because they are costly to produce. However, the role of carotenoids as “honest” signals during male contests is less clear, and it is not known whether a carotenoid-based trait can serve in both male–male competition and female choice. In this study, we studied the dual function of a carotenoid feather ornament in the rock sparrow (Petronia petronia), a bird species in which both sexes have a yellow throat patch whose size positively correlates with phenotypic measures. First, we investigated, in a field study, whether the size of a male’s yellow patch correlates with his ability to acquire a territory. Second, we tested the signal function of the yellow patch in two male–male interaction in captivity experiments. Finally, we measured female preference for males differing in throat patch size in a mate choice experiment. Our experiments revealed that the size of a male’s throat patch positively correlated with the number of nest boxes he was able to defend. Moreover, in controlled conditions, males with relatively large yellow patches had earlier access to food than those with small patches. Also, in an experiment in which a dummy rock sparrow with an experimentally manipulated yellow patch was positioned near a feeder, latency to feed by focal birds positively correlated with dummy patch size. Lastly, in a dichotomous mate choice experiment, females showed a proximity preference for males whose patch was experimentally enlarged. Taken together, these results suggest that the same carotenoid feather signal may be used in both male–male competition and female choice in this passerine bird.     

对退耕还林中农民选择权认识的经济学分析

农户决策行为和反应机制无疑是考察项目可持续性的一个重要方面。本文应用微观经济学理论．结合退耕还林工程的实际情况．提出理论假说：贫瘠土地退出种植是经济发展到一定水平的自发结果。并根据三省遐耕还林的实际调查数据。采用计量模型对退耕还林农户选择权认识问题进行检验。研究结果表明退耕还林工程的可持续性还存在一定隐患，退耕还林工程不仅要和当地的经济发展紧密结合。在操作方法上还需进一步改进。     

石化炼油厂碱渣废水处理工艺的选择

介绍了目前常规高浓度有机废水处理工艺各自的特点，提出在环评阶段如何选择炼油碱渣废水的处理工艺，并结合炼油厂自身特点向建设单位提供适宜的切实可行的碱渣废水处理工艺方案。     

Time constraints and multiple choice criteria in the sampling behaviour and mate choice of the fiddler crab,Uca annulipes

Active female sampling occurs in the fiddler crab Uca annulipes. Females sample the burrows of several males before remaining to mate in the burrow of the chosen partner. Females time larval release to coincide with the following nocturnal spring tide and must therefore leave sufficient time for embryonic development after mating. Here we show how this temporal constraint on search time affects female choosiness. We found that, at the start of the sampling period (when time constraints are minimal), females selectively sample the larger males in the population. Towards the end of the sampling period (when the temporal constraints increase the costs of sampling), females are less selective. Furthermore, we suggest that the number of males sampled (and other indices of ‘‘sampling effort’’) may not be reliable indicators of female choosiness and may not reflect the strength of female mating preferences under certain conditions. Burrow quality also emerged as an important criterion in final mate choice. Burrow structure potentially influences reproductive success, and mate acceptance based on burrow structure appears to involve a relatively invariant threshold criterion. Since there is no relationship between male size and burrow quality, females are using at least two independent criteria when choosing potential mates. We envisage mate choice as a two-stage process. First, females select which males to sample based on male size. They then decide whether or not to mate with a male based on burrow features. This sampling process explains how two unrelated variables can both predict male mating success. Received: 23 March 1995/Accepted after revision: 14 January 1996