1、T1 收获理论要 点收获目标 为了使种群开发获得最大回报，管理应以使对象种群可长期持续获得最大产量为目标。To maximize the returns gained by exploiting a population, management should aim to harvest the maximum yield that the maximum yield that the population can produce sustainably over the long term.Key NotesThe goals of harvestingT1 HARVESTING THEOR
2、Y最大持续产量 长期收获最大产量的一种方法是最大持续产量即 MSY法。随着种群密度在很低的基础上开始增加，出生率超过死亡率，种群的净补充量增加。当种群密度达到最大环境容纳量时，死亡率上升，出生率下降。因此最大净补充量发生在中等密度、种群中存在许多繁殖个体、而种内竞争又相对较弱的情况下。这一最大净补充量即为人们可长期从种群中收获的最大量 MSY。One approach to deduce the maximum long-term yield is known as the maximum sustainable yield, or MSY approach. As a population
3、increases in density from very low numbers, the birth rate outstrips the death rate, so the net recruitment(births-deaths) into the population rises. As the population density approaches the maximum the environment can support, the death rate increases and the birth rate falls. The maximum net recru
4、itment therefore occurs at an intermediate density, when intraspecific competition is relatively low yet there are many reproductive individuals in the population. This maximum net recruitment is the maximum number that can be harvested from the population sustainably the MSY.Maximum sustainable yie
5、ld配额限制 在一定时期，可通过控制配额（收获对象生物量或个体数量），限制收获。配额控制允许收获者在每一季节或每年收走一定数量的猎物。配额限制通常应用于海洋渔业来获得 MSY， 但成功例不多。这表明配额限制实际上很冒险，有可能导致过捕，甚至种群灭绝。6500万年前，行星撞击地球造成恐龙灭绝想象图。Harvesting may be limited by controlling the quota (the biomass or number of individuals culled ) in a given period. Quota controls thus allow the harv
6、esters to remove a fixed number of the prey species every season or year. Quota limi-tataion is commonly applied in marine fisheries to achieve a MSY with limited success. The theory demonstrates that quota-limitation is intrinsically risky and may cause overexploitation and even extinction of the h
7、arvested populations.Quota limitation努力限制 配额限制潜在的危险或通过导入努力限制来缓和。努力限制具有明显的优点。因为当猎物种群数量减少时，人们往往会通过更加努力来获限正在减少中的数量。环境波动 利用种群增长模型预测被收获种群可获潜能的效果会受到环境波动的严重影响。因为环境波动会影响种群的出生率或死亡率。The ability of models of population growth to predict the harvesting potential of a population is esverely compromised by enviro
8、nmental variation which may affect recruitment or mortality.Environmental fluctuationThe risk inherent in quota-limitation can be alleviated by adopting an approach of limiting effort. This has a clear advantage- as a prey species becomes rarer, more effort will be required to seek out and catch the diminishing numbers.Effort limitation相关主题 种群和种群结构（ H1） 密度和密度制约（ H3）出生率、死亡率和种群增长（ H2） 种群动态 波动、周期和混沌（ H4）动态库模型 简单的模型不考虑种群的年龄结构，这使其预测能力有限，因为死亡率与繁殖力都是与年龄相关的。收获个体通常都是种群中体大、年高的个休，具有最高的繁殖潜能。精确地考虑到不同年龄群出生率、生长和死亡率的动态库模型对对象种群的预测效果更好。举例来说，考虑到不同年龄群的动态库模型意味着可理论上检测海洋渔业中使用不同大小网具的影响效果。
