Fishing the last major exploitation of wild populations by mankind © 2008 Paul Billiet ODWSODWS

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

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

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 ODWSODWS

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 ODWSODWS

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 ODWSODWS

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 ODWSODWS

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 anchovy Pacific salmon Newfoundland, Grand Banks cod North Sea Herring © 2008 Paul Billiet ODWSODWS

Maximum Sustainable Yield (MSY) K Numbers Time © 2008 Paul Billiet ODWSODWS

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) © 2008 Paul Billiet ODWSODWS

Problems with MSY  Age structure: If all the age groups are harvested recruitment of young fish into the reproductive group will be reduced The 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 ODWSODWS

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) © 2008 Paul Billiet ODWSODWS