Why overfishing an interdisciplinary problem?
- fish (species & abundance)/ ecology
- managerial practices (fishing/econ)
- regulations (institutionalization of a field)/ politics
lake victoria’s fisheries
- dynamic eco-history of the lake victoria basin
- high population density
- supports Africa’s largest inland fishery
history of fishing in the area
- intensified with new tech
- intro of new species influenced faunal compositon & balance
fish that flourished
even with gigantic nile perch “mputa”
- nile tilapia “ngege” ( has become abundant, commercially important )
- “mukene”, biomass 6x
changes
lake victoria system composition
multi-species system exploting native fish –> 3 species almost all catch ( 2 are non-native)
Similar changes have occured in which other lakes in the victoria basin?
Lake Nabugabo
Kyoga
Changes in perch population
- increased fishing
- decrease in stock
- decrease in size
lake ecology
not homogeneous
understanding habitat diversity is key to understand relative fish abundance and reproduction
ecological morphology
refers to resource availability (oxygen, nutrients, protection etc..)
Biodiversity Banks (3)
satellite lakes, rcky refugia, wetland refugia
Beach management Units
promising solution/control of socioecological system
BMUs structure
new institutions that regulate fishing in the lakes
- to fish, fisherman must register
- control gear used
- no territorial jurisdiction
- no jurisdiction over capture (type or quantity)
Overfishing is class case of …?
tragedy of the commons or open access resources
Collective Action Problem (CAT)
predicts a resource managed in common has more probability to be sustainably managed with certain characteristics
increasing probability of sustainable management
- small size (group +resources)
- well-defined boundaries
- high level of dependence on resource
- fair allocation
- locally devised access and rules
- clear territoriality
- resource harvest restrictions match recovery
flaws of BMU design
ID by CAT predictors
- lack of territorial jurisdiction
- no regulations on harvest
- fisheries highly unpredictables (spatial distribution, compositition..)
BMUs = insufficient institutional step
Why are fisheries so hard to manage?
- difficult to institutionalize, and generate territorial jurisdictions?
Data required to manage fisheries?
- ecological distributions of resources (ecological map, fish presence+mobility, ethnoecological mapping)
- spatial distributions of the fishing effort
- trade networks
How to create a map of ecological structure?
in lake nabugabo
- ecological structure (depth+ shoreline ecotones: lilies, grass, forest edge)
- quantify fish movement (tag)
- etnoecological mapping (cognitive map +interviews)
Collecting data on fishing effort
in lake Nabugabo
- use ecological map as base, recall interview designs to determine where BMU members fished during 5 days of each month
example of fishing recall qs
- where did you fish today? how long? why there?
catch landing surveys
both BMUs
boats, type of fish & gear
expected results
Lake Nabugabo
define specific ecological patches with significant fish species distribution ==> define exclusive territorial jurisdictions for the BMUs*
worth defending
consequences of no predictable pattern
in fishing efforts
- cannot design functional institutional structure
- no incentive for collective action
