Presentation on theme: "The Common Fisheries Policy State of Resources and Ecosystems Rainer Froese, GEOMAR, Germany 10 December 2014 Sustainable Fisheries Internal Seminar S&D."— Presentation transcript:
The Common Fisheries Policy State of Resources and Ecosystems Rainer Froese, GEOMAR, Germany 10 December 2014 Sustainable Fisheries Internal Seminar S&D PECH Working Group
Overview Revisiting MSY, F msy, B pa and B msy State of Resources State of the Ecosystems Rebuilding stocks above MSY-Level Minimizing the Impact of Profitable Fishing Summary
Revisiting MSY, F, F msy, B pa and B msy MSY is the maximum catch that a stock can deliver long-term B msy is the biomass that can produce MSY B pa is the biomass below which recruitment may be compromised F is the fraction of the fish (present during the year) that are caught F msy is the F that leads to MSY and B msy, albeit in infinite time
State of the Resource: Stock Size The offical reference points for safe biological limits (B pa ) are often based on the lowest stock size ever observed (B loss ) With B pa properly estimated, 52% of the stocks were outside of safe biological limits, and 12% were severely depleted. (Froese et al. 2014)
State of the Resource: Stock Size CFP requires rebuilding of stocks above B msy There are no official reference points for B msy But 2*B pa can be used as a proxy for B msy In 2013, 88% of the stocks were below the proxy for B msy Froese et al. 2014)
State of the Resources: Fishing Mortality F Fisheries science holds that sustainable fishing mortality F msy has to be less than natural mortality M However, official estimates of F msy exceeded natural mortality M in 76% of the stocks Fishing mortality in 2013 exceeded natural mortality in 73% of the stocks, including those that were severely depleted (Froese et al. 2014)
State of the Resource: Maturity Fisheries science and common sense hold that fish shall reproduce before being caught In 74% of the stocks, the age at first capture was below the age at first maturity (Froese et al. 2014 )
State of the Ecosystems What is the minimum stock size that still allows species to fulfil their ecosystem role as prey or predators? Fisheries science holds that 2/3 of unexploited population size may be a lower limit for regular fish (with F ~ 0.8 F msy ) and ¾ may be a lower limit for forage fish (with F ~ 0.5 F msy ) (Froese et al. in prep)
Fishery Seals Harbour Porpoise Adult CodJuvenile Cod Other Demersal Fish Sprat Adult Herring Juvenile Herring Other Pelagic Fish Flatfish (Sea-) Birds Benthic Meiofauna Zooplankton Bacteria/Microorganisms Benthic Producers Benthic Macrofauna Detritus / DOM Phytoplankton 4 5 Trophic Level 3 2 Pelagic Macrofauna Food Web of the Western Baltic Sea Sprat is a central food organisms and „natural“ predators must compete for it with the fishery. Opitz & Garilao unpublished
State of the Ecosystems What is the age and size structure that allows a population to reproduce and fulfil its ecosystem role as prey or predator? The natural length at first maturity is about 1/3 to ½ of maximum length The natural average length of parents is about 2/3 of maximum length Starting fishing at about ½ of maximum length allows all fish to reproduce and leads to natural average length; it also maximizes catch and biomass for a given F (Froese et al. in prep.)
Long-term Catch as a Function of F/M and Length at First Capture Froese et al. in prep.
Biomass as a Function of F/M and Length at first Capture Froese et al. in prep.
Maximizing Profits of Fishers Profit of fishers is the difference between the value of the catch and the cost of fishing Cost of fishing is a function of the abundance of fish Highest profits are obtained at about 1.2 B msy 1.2 B msy is therefore the target biomass level in Australia
Follow the Money… Froese et al. in prep. Cost Value of catch Profit
Summary In 2013, about ¾ of the stocks were too small, were fished too hard, and were caught before reaching maturity For stocks to rebuild above levels that can produce MSY, F has to be smaller than F msy For minimizing impact of fishing and maximizing profits, F should not exceed 0.8 F msy and length at first capture should be about half of maximum length For forage fish (herring, sprat, anchovy, …) to fulfil their crucial ecosystem duties, F <= 0.5 F msy