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Fishing

Fishing. the last major exploitation of wild populations by mankind. © 2008 Paul Billiet ODWS. Factory ship. ACEL. Fish stocks. Though fish farming is increasing, fishing represents the last major exploitation of wild populations by mankind. © 2008 Paul Billiet ODWS.

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Fishing

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  1. Fishing the last major exploitation of wild populations by mankind © 2008 Paul Billiet ODWS

  2. Factory ship ACEL Fish stocks • Though fish farming is increasing, fishing represents the last major exploitation of wild populations by mankind © 2008 Paul Billiet ODWS

  3. Universidad de La Serena A case study: The Peruvian Anchovy (Engraulis ringens) © 2008 Paul Billiet ODWS

  4. The Peruvian Anchovy • This is a small (12-20cm), short-lived species maturing in 1 year • Anchovy live in the surface waters in large shoals off the coast of Peru and northern Chile • Here there are cold currents up-welling from the sea bed bringing nutrients for phytoplankton • Plankton is at the base of the food chain. © 2008 Paul Billiet ODWS

  5. The Peruvian Anchovy • The harvest of this fish doubled every year from 1955 to 1961 • Experts estimated the maximum harvestable 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 of the anchovy were used for human food • But a lot was ground into fishmeal for animal feed © 2008 Paul Billiet ODWS

  6. The collapse of the anchovy fishery • In 1972 there was an El Niño event that brought warm tropical water into the area • The up-welling stopped, • the phytoplankton growth decreased • the anchovy numbers fell and concentrated further south • The concentrated shoals of anchovy were easy targets for fishing boat eager to recuperate their harvest • The political will was not there to impose reduced quotas • 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 © 2008 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 © 2008 Paul Billiet ODWS

  8. The result • Fish populations are reduced below their 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 anchovyPacific salmonNewfoundland, Grand Banks codNorth Sea Herring © 2008 Paul Billiet ODWS

  9. K 3 2 • Numbers 1 Time Maximum Sustainable Yield (MSY) © 2008 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 quotaswill produce a constant harvesting rate (i.e. a constant number of individuals fished in a given period of time) © 2008 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 reducedThe answer is to 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 © 2008 Paul Billiet ODWS

  12. What is required? • Nets with bigger mesh size • Regulatedfishing 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) © 2008 Paul Billiet ODWS

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