Some advantages of MPAs for fisheries - SADSTIA · Some advantages of MPAs for fisheries ... ,...
18
Some advantages of MPAs for fisheries Colin A(wood Marine Research Ins4tute Department of Biological Science University of Cape Town
Transcript of Some advantages of MPAs for fisheries - SADSTIA · Some advantages of MPAs for fisheries ... ,...
Some advantages of MPAs for fisheries
ColinA(woodMarineResearchIns4tute
DepartmentofBiologicalScienceUniversityofCapeTown
The Schaefer produc:on model
0
2
4
6
8
10
12
0 0,1 0,2 0,3 0,4 0,5Equilibriu
mann
ualcatch(1
000t)
Fishingmortalityrate(y-1)
Modelparameters:r=0.4y-1,K=100000t
HolyGrail
How do fishery dynamics alter with MPAs?
0
2
4
6
8
10
12
0 0,1 0,2 0,3 0,4 0,5Equilibriu
mann
ualcatch(1
000t)
Fishingmortalityrate(y-1)
NoMPA
WithMPAs
MPAmodelparameters:r=0.4y-1,MPAscover20%ofarea,Effortdisplacementincluded,Movementmimicsresidentfishwithbroadcastspawning
cost
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
0
2
4
6
8
10
12
0 0,1 0,2 0,3 0,4 0,5Equilibriu
mann
ualcatch(1
000t)
Fishingmortalityrate(y-1)
NoMPA
WithMPAs
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
0
2
4
6
8
10
12
0 0,1 0,2 0,3 0,4 0,5Equilibriu
mann
ualcatch(1
000t)
Fishingmortalityrate(y-1)
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
0
2
4
6
8
10
12
0 0,1 0,2 0,3 0,4 0,5Equilibriu
mann
ualcatch(1
000t)
Fishingmortalityrate(y-1)
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
