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Some advantages of MPAs for fisheries
ColinA(woodMarineResearchIns4tute
DepartmentofBiologicalScienceUniversityofCapeTown
The Schaefer produc:on model
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Modelparameters:r=0.4y-1,K=100000t
HolyGrail
How do fishery dynamics alter with MPAs?
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MPAmodelparameters:r=0.4y-1,MPAscover20%ofarea,Effortdisplacementincluded,Movementmimicsresidentfishwithbroadcastspawning
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Think of a fishery in your area, and :ck the correct boxes.
1) Isthereaneffec4vecatchmonitoringsystem?2)Istherearobustassessmentprocedure?3)Isthereareliableobserversystem?4)Iscompliancewithregula4onsgood?5)Istheadministra4oncorrup4on-free?
Yes No
Yes No
Yes No
Yes No
Yes No
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HolyGrail
If you :cked no for one or more ques:ons, your fishery could end up here (if it is not here already).
Some:mes (very, very seldom) scien:sts get it wrong.
Mysterious New Whale Species Discovered in Alaska
Insurance quote
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Premium
Cover
Annual costs of insurance
4.5%ofthevalueofyourcar
1.5%ofthevalueofyourhouse
Howmuchshouldwepayhere?
Regula:on by TAC and effort control have some limita:ons.
Most types of fishing gear catch several species of fish at once, other than the one targeted
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These other species are usually less produc:ve. What happens to catches of these species when we reach for
the Holy Grail?
?
?
R.I.P.
Fisheries assessment is easy at high la:tudes, but difficult in the tropics. Why?
1. Thenumberofspeciesincreasesdrama4callyfrompoletoequator,buttheabundancesdiminish.Weneedtodomoreassessmentsinthetropics,yetthefinancialincen4veislessforeachspecies.Of±600exploitedfishspeciesinSA,16areassessed!
2. Withsomanysimilartropicalspecies,thereisgreattaxonomicconfusion,andcatchrecordsarenotreliablyassignedtospecies.
3. Seasonalsignalsareweakornon-existent,sowestruggletoreadthebandsintheotoliths,andtofollowcohorts.Wedonotknowthefish’svitalrates,suchasgrowthandmortality,andtheage-at-maturity.Theseareimportantparametersthatinfluenceproduc4vity.
MPAsareespeciallyusefulinthetropics!
Problem
Fisheries assessments are difficult in the tropics.
AND
Tropical countries have the worst governance and the weakest scien:fic capacity.
Modernfishingintensitypresentsamassiveselec4onpressureagainstpar4culartraits.Manyoftheseareheritable.
Farmers select the best strains for breeding
Farmersimprovetheirstock
Fishing does the opposite
Wekillthestrongandleavetheweaktobreed.Intensefishingweakenstheproduc4vityofthestock.Fishingalsoquicklyreducesgene4cvariability.Gene4cvariabilityisafundamentalrequirementforDarwinianselec4onandadapta4onin4mesof(climate)change.Ul4mately,fishproduc4ondependsongene4cvariability.MPAsarethebestmeanstomaintainnaturalselec4onpressuresandtopreservegene4cvariability.
MPAs can provide substan:al benefits to most of the world’s fisheries
