Biomass management targets and the conservation and economic benefits of marine reserves

The establishment of no‐take marine reserves has been increasingly promoted as a key measure to achieve conservation and sustainability goals in fisheries. Regardless of the wide range of benefits cited, the effectiveness of reserve establishment depends critically on fisheries management outside the reserves. We construct a bioeconomic model of a fishery that allows for the establishment of a no‐take marine reserve and evaluate how the choice of the off‐reserve management target influences the effectiveness of reserve establishment. We evaluate two biomass targets: (i) B_MSY or the biomass that produces the maximum sustainable yield (MSY) and (ii) B_MEY or the biomass that maximizes the net present value of the returns to fishing. The parameterized model shows that, for a wide range of scenarios, the fishery will be better off in terms of both conservation and economic objectives when the no‐take reserve is established in conjunction with the B_MEY target rather than with the B_MSY target. Model results further show that the opportunity cost of securing additional fish biomass, in both deterministic and stochastic environments, is lower when the reserve size is increased under the B_MEY target. This finding is important because marine reserves have been established as a key measure to restore depleted fish stocks, and the results suggest that this objective can be achieved with lower economic costs in a B_MEY managed fishery.     

深水网箱圆台形囊网的设计与制作

深水网箱囊网受水流推动,形状随水阻力大小而变化。囊网形状的变化与养殖容积有关,并直接影响了网箱养殖效果。通过分析认为,圆台形重力式柔性囊网有较好的抗流效果,更适合于深水网箱养殖作业。通过实物试验,报道了圆台形囊网在流速0.45-0.75 m·s-1时的外形设计、配重及制作方法,为强流下的深水网箱囊网制作提供参考。     

民间文化遗产旅游资源设计与开发研究——以河北曲阳石雕为例

以具有典型意义的河北省曲阳县羊平村为例,分析了曲阳县乡村民间文化旅游概况,阐述了其旅游资源丰富、区位条件优越、旅游业已经获得一定发展的优势,也总结了其道路绿化不足、环境污染严重、高层次人才缺乏、小型商品开发不足的劣势,在此基础上提出了应该以商旅互动、立足文化、动态参与、系统规划、统筹兼顾等原则指导乡村民间文化旅游的开发设计,并总结了相关发展战略。针对羊平村,从环境建设、石岗雕刻公园休闲区设计、黄石广场功能区设计、乡村旅游商品设计方面展开了重点建设项目探讨,以期能对我国民间文化旅游资源开发提供参考。     

Temperature modeling of a land-based aquaculture system for the production of Gracilaria pacifica: Possible system modifications to conserve heat and extend the growing season

Temperature control is a major cost for numerous aquaculture systems. Solar thermal engineering techniques can be used to identify inexpensive methods for conserving and capturing heat. Gracilaria pacifica, also known as the culinary ingredient ogo, is currently grown in land-based tanks at a site in Goleta, CA where influent sea water temperatures infrequently reach the 21–28 °C range that provides for optimal growth. The major objective of this study was to explore various designs of a G. pacifica tank culture system that maintain optimal water temperature year round to maximize growth. A model was constructed and calibrated by comparing results to a one-third scale pilot system operated in Davis, CA. For model calibration the most sensitive parameter such as cover optical properties were adjusted first and less sensitive parameters were adjusted later. The pilot system consisted of six tanks, three insulated with foam and a clear polyethylene cover (experimental), and three uninsulated and uncovered (controls). The model had weather data inputs including air temperature, humidity, wind speed, and solar radiation. The model was then compared to a full-scale system operated in Santa Barbara during the winter. The experimental pilot system was 4.93 °C warmer than the control pilot system under optimal weather conditions. The full-scale experimental system was 2.80 °C warmer than the control system under non-ideal conditions. The model demonstrated predictive accuracy under most weather conditions. Furthermore the model is robust enough to accept estimated values for many inputs and still produce accurate results, this suggests a simpler model may be feasible. A polyethylene cover and insulation are not sufficient in general for raising the water temperature to the optimum range during the winter; they may be during other times of the year when more solar energy is available, thereby extending the growing season.     

RNA/DNA ratio is an early responding,accurate performance parameter in growth experiments of noble crayfish Astacus astacus (L.)

Recent intensification efforts of astacid culture considerably depend on the appropriate assessment of the animal's physiological condition both for research and application. We conducted a 4 weeks feeding experiment to assess temporal resolution and accuracy of different response parameters (RNA/DNA ratio, RNA per wet weight, carapace length, wet weight, specific growth rate). Juvenile noble crayfish were exposed to five feeding regimes that differed in feeding frequency and food availability. Continuous growth was detected in all feeding regimes with individual increase up to 90% (wet weight) and 17% (carapace length), respectively. Morphometric parameters allowed separation of three weight‐groups or two length‐groups. During the experimental period RNA/DNA ratios showed both decrease (?17%) and increase (+35%), with superior accuracy than morphometric parameters, separating four groups. Based on RNA/DNA ratios, different feeding regimes were detected earlier, with two groups separated already after 3 weeks. RNA/DNA ratio was clearly superior to RNA per unit wet weight, as the latter failed to detect any differences between groups. In conclusion, RNA/DNA ratio is a valuable tool in nutritional studies with freshwater crayfish if overall growth is the key variable of interest.     

Comparison of experimental designs for estimating quantitative genetic parameters in fish

Four popular experimental designs for estimating variance components of additive genetic effects and (secondarily) dominance and maternal effects in fish (full‐sib families, half‐sib families, nested design and factorial design) were compared. The error variances of the estimators were formulated as functions of the true (hypothetical) values of genetic and environmental variances, depending on the experimental design considered, and whether the families were reared separately or mixed. Half‐sib families and rectangular (many sires×few dams) factorial design were most useful for the estimation of heritability. The nested design appeared much less adequate. The minimum experimental capacity for obtaining accurate estimates was 100 lots in separate rearing or 1000 fish in mixed rearing. A larger experimental capacity is required when dominance and maternal effects as well as heritability are to be estimated because these different estimations, requiring contradictory conditions, cannot be simultaneously optimized.     

秸秆膨化机度电产量的生产参数优化及影响因素分析

本文对影响秸秆膨化机度电产量的主要生产参数—秸秆含水率(X1)、秸秆粒度(X2)和螺杆转速(X3)进行了研究,揭示了度电产量与这些参数之间的内在规律,创建了秸秆度电产量与三个参数之间的数学模型,进行了生产参数优化,并就生产参数对度电产量的影响进行了分析。     

微电脑在二片式对拖网设计上的应用及捕捞效果分析

本文分析了二片式对拖网设计软件设计的基本原理及渔获效果的对比。结果表明,本软件设计先进、科学,具有良好的适用性、精确性、高度灵活性和快速简便性等优点;利用本软件设计的网具,具有良好的渔获效果。     

避风型渔港避风因素浅析

我国的东南沿海是最容易遭受热带气旋影响的脆弱地带,每年的5-11月,都会遭受热带气旋的影响,对渔港、渔船和渔民构成严重威胁.而渔港的避风能力是渔民最为关心的问题,通过近几年登陆我国的强台风等级以上的热带气旋对渔港、渔船及渔民造成损失的实例分析,从防波堤设计标准、避风锚地的底质、锚泊方式等3个方面对避风型渔港的避风因素展开讨论,得到了有价值的结论,为渔港、渔船和渔民减少灾害,为政府建设避风型渔港决策提供科学依据.     

遗传学实验教学改革与实践

在遗传学实验教学改革中,通过改进实验教学方法,更新和完善实验教学内容,完善考核方法,改善实验条件,加强师资建设等,不断提高实验教学质量。