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

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

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

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

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

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

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

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

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

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

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

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