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Lecture 14

Lecture 14 Ecology and Evolution of Harvested Populations

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Doug Thomson

Lecture 14 BIO220 Ecology and Evolution of Harvested PopulationsDensitydependent growth rate can limit population sizeTern carrying capacity on islands is limited by nesting spaceAs time increases N increases until it reaches plateau that reflects capacity that depends on number of available nesting sitesMaximizing population growthPer capita rate of increase x population sizeoverall rate of population increaseIdeal harvesting strategy harvestK individualsyear so population is at maximum growth rateIdeal scenarioHarvest k2 per yearPopulation always in region of maximum growthoHighest rate of replenishmentAllowing harvesting and selfsustaining populationsBest case scenario does not account for random chance weather seasonyear to year flux predation etcHarvesting costs increase with increased carrying capacityMEY Maximum economic yield where benefitcost maximizedMSY maximum population growthHarvesting costs increase with increased KBCBCMEYMSYHarvestMEYHarvestMSYConsequences of MEYMSYConstant financial pressure to harvest moreoNot just for gross returns but for net returnsPopulations harvested to point where they have low population growth ratesoSame absolute amount removed each yearoBut population experiencing slower population growthoAnnual stock flux hard to track optimallyoWill lead to extinctionImprovements in technology make cost curve flatter but do not alter the population dynamicsUntil the fishery collapsesNet profitsmore pressure to fish and get more fishTight regulations enforcement quotas below estimated MSTnegative effects on population negative effects on society no jobsCatch quotasMSY natural insurance via ecological stabilityThere can be economic incentive to fish more even when industry is failing
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