《生物资源评估》渔业资源数量变动的一般规律

1、第一章 渔业资源数量变动的一般规律第一节 研究资源数量变动的基本单位第二节 资源数量变动的基本原因及其一般规律第三节 捕捞对鱼类资源数量变动和渔获数量与质量所产生的影响第一节 研究资源数量变动的基本单位1、渔业资源总量：海洋和内陆水域中鱼类资源蕴藏量，还包括非鱼类的海洋经济动植物2. 经济渔业资源：海洋与淡水中达到捕捞规格的经济水生动物的总量。3. 预备资源：未达到可捕规格的补充群体总量。Types of fisheries resourcesFish species: pelagic fishdemersal fish(King 2007)Types of fisheries resourc

2、esShellfish species CrustaceansMolluscs(King 2007)Types of fisheries resourcesMajor group of commercially important species渔业统计年鉴 2015年全国海洋捕捞产量 （吨）Types of fisheries resourcesMajor group of commercially important species渔业统计年鉴 2015年全国部分海洋鱼类捕捞产量 （吨）渔业资源分类与管理Short-lived species with high fecundityLarg

3、e fluctuations in recruits and stock sizesDensity-independent factors more importantLarge variations in catchLong-lived species with low fecundityStrong stock-recruits relationshipDensity-dependent factors more importantMore constant yieldLife history types: r selection and K selection (Pinaka, 1970

4、)(King, 2007)Life History Types: (Winemiller 2005)Types of fisheries resourcesProtected: Marine mammals, Seabird Sea turtlesEndangered: Other long-lived speciesInvasive species 渔业资源的分布Distribution pattern:Sunlight and nutrientsPhytoplankton Primary productivityFisheriesMechanisms for high nutrients

5、in photic zonesTerrestrial sources for inshore areaConvection currentUpwelling渔业资源的分布Latitude: high species diversity but low population sizes in tropical area low species diversity but high abundance in temperate watersTemperate waters: worlds large fisheries based on relatively few cool-water spec

6、iesCoastal and tropical waters: small catches from a much greater variety of species种群（Population)种以下的分类单位，见“渔业资源生物学”定义及鉴定方 法。指在特定时间内,占据特定空间的同种有机体的集合群，是仅次于种的一个分类单位，也是渔业资源评估的单元。密度、出生率、死亡率、年龄分布、生物潜能、分散和增长型Stock亚种群或种下群（Subpopulation): 比种群范围更小，作为数量变动的基本单位更合适。单位资源群体（Unit Stock):相同品种的一群个体，它基本是一个具有自身 产卵场而且

7、不会因洄游迁入迁出而变化的独立的群体，有时多品种鱼群也可作为单位资源群体。费鸿年（1990）种族、种群、群体、亚种群是物种存在的具体形式鱼类群体是由可充分随机交配的个体群所组成，具有时间或空间的生殖隔离以及独立的洄游系统，在遗传离散性上保持着个体群的生态、形态、生理性状的相对稳定，是水产资源研究和管理的基本单位。第二节 资源数量变动的基本原因及其一般规律一、资源数量变动的基本原因 内因：生物因素 外因：环境因素（自然环境、人为环境）1. 生物因素繁殖：亲体数量，成活率生长：饵料和水文条件，密度、水温死亡：自然死亡（饵料、疾病、外界环境剧变） 卵-受精卵-仔稚鱼-成鱼补充死亡率达99.9% 2、

8、环境因素：水温、盐度、海流种间关系、敌害生物捕捞因素二、资源数量变动的基本模型1、Russell(英国，1931) 影响资源数量变动的四个因素 B2= B1 + (R+G) - (M+Y)B2= B1 + (R+G) - (M+Y)B2、B1: 时间2、1时的种群数量； R：补充量； G：生长； M：自然死亡； Y：捕捞死亡 当B2 B1，则资源处于增加状态；当B2 = B1，则资源处于平衡状态；当B2 B1，则资源处于减少状态。Schaefer & Beverton(1963) dB/dt=0, 资源处于平衡状态 F(f) = r(B) + g(B) - M(B) 平衡渔获量: Y = F(

9、f) B = r(B) + g(B) - M(B) B 把R、G、M综合考虑：Schaefer剩余产量模型 把R、G、M分别考虑：Beverton-Holt动态综合模型 渔业资源群体可分为两部分，即补充群体（recruitment）和 剩余群体(surplus)。（1）生物学含义 （2）渔业上的含义三、补充群体和剩余群体的数量变动1. 生物学的观点补充群体：鱼类经卵、仔鱼生长为幼鱼，再进入产卵场的群体。亦即第一次性成熟个体。（客观的）。剩余群体： 重复产卵群体为剩余群体。2. 渔业的观点补充群体：凡幼鱼长大到一定规格，进入渔场与渔具相遇，并被大量捕捞的群体。（主观的，人为的）。剩余群体：首次捕

10、捞后剩余的群体。定义的外延如果渔场只限于产卵场，如果渔业还利用索饵场、越冬场例如黄海鲱和蓝点马鲛：性成熟年龄为龄，大量捕捞年龄为龄和当年生鱼。补充过程：补充量补充年龄补充方式： （1）一次性补充（刀刃型）。 （2）分批补充：同一世代随生长速率不同而分 批。 （3）连续补充：随时生长，随时补充到成体中，主要是热带鱼种。影响因素补充群体数量变动的原因复杂：亲体数量、水文环境（温、盐、流）、敌害、饵料。剩余群体数量变动的原因：捕捞为主要因素，世代数量。一般补充量较产卵量少很多：饵料和死亡除一些中上层鱼类的补充年间波动很大，一般鱼类的补充量都比较稳定，特别是寿命较长的底层鱼类。第三节 捕捞对鱼类资源数

11、量变动和渔获数量与质量所产生的影响表1-1，长命鱼类和短命鱼类年存活的比较年死亡率%年龄0123456782010008006405124103282622101687010003009027821表1-2，世代强度相同的各龄存活数（年死亡率20%） 在一年中出现的每一年龄的鱼类数字（行，横向）和在其生命期间连续年龄中一个世代的鱼类数目（斜向）相同。在某一年中各年龄的资源数量的下降反映出鱼类的死亡率。年份年龄0123419891000800640512410199010008006405124101991100080064051241019921000800640512410199310008

12、00640512410通常世代强度逐年变化不定：表1-3，每一年龄的鱼类存活数及变化的世代强度（年死亡率20%）任何一年资源的年龄组成还取决于世代的波动率。若波动不大，年龄组成仍反映死亡率的平均衰减情况。年份年龄01234198910008809603074101990900800704768246199113007206405636141992600104057651245119931000480832461410自然死亡捕捞死亡Z= M+F第四节 渔业数据 Catch data: commercial & recreational Age/size composition data Cat

13、ch-at-age data Fishing effort data Abundance index data Weight-length, age-length data Fecundity data Maturation data Gear selectivity data Tagging dataSome typical fisheries dataFisheries-dependent monitoring programLogbook, port sampling, sea sampling (observer program)Fisheries-independent progra

14、m (scientific survey)stratified random survey, systematic survey Surveying fishermendeveloping questionnaires to understand social problems fishing industries face.Programs to collect data for stock assessment and managementMonitoring ProgramsFisheries independent program has good representative of

15、fish stocks, but expensiveFisheries dependent program provide greater quantities of data at lower costs than fisheries independent programsExample: size measurementFisheries-dependent Monitoring ProgramTarget: fishermen, dealers, processors, buyers,Logbook: voluntary and mandatorySea and dock sampli

16、ng:Design: When, where, from whom, and how to sampleImportant considerations: randomness, efficiency, practical, cost-effective, achievable, back-up plan. To measure: biological, fisheries, and social variables A typical form for fishermen Fisheries Dependent MonitoringMultiple fisheries dependent m

17、onitoring programs are commonMultiple programs Allow several unique sampling designsHelp address problems with data qualitySpatial and temporal coverageAddress concerns of different groupsQuality of fisheries data Accuracy Precision Sampling representative Temporal and spatial coverageThe quality of

18、 information depends onCoverage of vessels with onboard observersFishing behavior of vessels(1) Type of data(2) Design of survey programs(3) Experience of technicians(4) Nature of fisheries(5) Management strategy/plan(6) Interactions of fishermen and managers(7) Environmental factors(8) Economic, so

19、cial, and/or ecological valuesFactors influencing data qualityData diversity: sources of dataLength of time seriesNumber of variablesSample sizes: effective sample sizes (lots of data from one sampling site versus a few samples per site from many sites), e.g., size composition data estimatesSample r

20、angesQuantity of the dataFactors Influencing Data Quantity(1) Economic and/or social values of fisheries(2) Stage of fisheries development(3) Ecological importance of fisheries(4) Spatial and temporal distributionsSource of Error Measurement error Model error Process error Operating errorNature of t

21、he errorsMagnitude of the errorsMethod to collect the informationon-board observer programlog-book The quality of information depends onCoverage of vessels with on-board observersFishing behavior of vesselsExample: Biased Errors in Catch dataDiscardingAt-sea discarding: discard part of the catch bac

22、k into the sea before landing10% of the total world catch discarded(e.g. 80 million cod discarded in the cod fishery off the northern coast of Norway in the 1986-87 fishing season)Factors influencing discarding:MarketHolding capacityRegulationsNature of fisheriesBiased estimates of the total catchBi

23、ased estimates of age compositionBiased estimates of stock size?Biased estimates of exploitation rate?Direction of the biases?Consequences to fisheries population dynamics study if we dont include discarded catch Sample Survey DesignsBased on statistical principle Why?Where?When?How?Types of Samplin

24、gNonprobability SamplesJudgmentUse experience to select sampleExample: sentinel fixed stationsQuotaSimilar to stratified sampling except no random samplingChunk (convenience)Use elements most availableSimple Random SampleEach population element has an equal chance of being selectedSelecting 1 subject does not affect selecting othersMay use random number table, computerSimple Ra