1. the last major exploitation of wild populations by mankind
Fishing
the last major exploitation of wild populations by mankind
© 2016 Paul Billiet ODWS

2. Fish stocks Fish farming is increasing
Fishing still represents a major exploitation of wild populations.
ACEL
Factory ship
© P Billiet
© 2016 Paul Billiet ODWS

3. A case study: The Peruvian Anchovy (Engraulis ringens)
ABC
Universidad de La Serena

4. The Peruvian Anchovy
This is a small (12-20cm), short-lived species maturing in 1 year
W. coast surface waters S. America
Cold currents up-welling from the sea bed bringing nutrients for phytoplankton
Plankton is at the base of the food chain.
© 2016 Paul Billiet ODWS

5. The Peruvian Anchovy The harvest doubled every year from 1955 to 1961
Experts estimated the maximum sustainable yield (MSY) at 10 to 11 million tonnes per year
Through the 1960s the harvest was about this level
The biggest fishing harvest in the world
Some used for human food
A lot for animal feed.
© 2016 Paul Billiet ODWS

6. The collapse of the anchovy fishery
1972 El Niño event
Warm tropical water into the area
Up-welling stopped
Phytoplankton growth decreased
Anchovy numbers fell and concentrated further south
Concentrated shoals of anchovy easy targets for fishing boats
Quotas not reduced
Larger catches were made
No young fish were entering the population (no recruitment)
No reproduction was taking place
The fish stocks collapsed and did not recover.
© 2016 Paul Billiet ODWS

7. What is causing the damage to fisheries worldwide?
Uncontrolled harvesting – even if quotas are imposed they need to be policed
Unrealistic and inflexible quotas
Insufficient data on fish populations
Improved technology in the fishing industry.
© 2016 Paul Billiet ODWS

8. The result Fish populations are reduced below recovery level
Other non-commercial species are being taken and killed at the same time
Other species (e.g. sea birds) are being deprived of a food resource
Total ban on some species now imposed: Peruvian anchovy Pacific salmon Newfoundland, Grand Banks cod North Sea Herring.
© 2016 Paul Billiet ODWS

9. Maximum Sustainable Yield (MSY)K
Numbers
Time 1 2 3
© 2016 Paul Billiet ODWS

10. Maximum Sustainable Yield (MSY)
Based upon: 1. the harvest rate 2. the recruitment rate of new (young) fish into the population
a population can be harvested at the point in their population growth rate where it is highest (the exponential phase)
Harvesting (output) balances recruitment (input)
Fixed fishing quotas will produce a constant harvesting rate (i.e. a constant number of individuals fished in a given period of time).
© 2016 Paul Billiet ODWS

11. Problems with MSY
Age structure: If all the age groups are harvested recruitment of young fish into the reproductive group will be reduced Use a net with a big enough mesh size that lets the young fish escape
Limiting factors: If the limiting factors in the environment change so does the population growth rate
Limiting factors set the carrying capacity (K) of an environment
Increasing limiting factors will cause K to drop
Fixed quotas cannot cope with this
Data: For MSY to work accurate data in fish populations is needed (population size, age structure, recruitment rates)
Usually these are not well known.
© 2016 Paul Billiet ODWS

12. What is required? Nets with bigger mesh size Regulated fishing methods
More data on fish populations (e.g. by fish tagging investigations – mark and recapture)
Constant monitoring to observe changes in environmental factors (e.g.El Niño events)
Policing of fishing industry – respect of quotas
International agreements
Greater exploitation of fish farming
But this is not without its own problems (space, diseases and pollution are all associated with intensive fish culture).
© 2016 Paul Billiet ODWS