Ecosystem-Based Fisheries Management Rainer Froese IfM-GEOMAR

Content Goals of ecosystem-based fisheries management Impact of fishing Ecosystems and life-history strategies Implications for ecosystem-based fisheries management Fishing down the food web What can be done?

Goals of Ecosystem-based Fisheries Management Sustainable and productive fisheries Minimum impact on the ecosystem Ecosystem as close to unfished state as possible

Impact of Fishing Fishing strongly alters the size spectrum of ecosystems (and populations) (Froese et al. 2000) Fishing reduces trophic diversity (fishing down the food web) (Pauly et al. 1998) Fishing strongly alters relative abundances, with collapse of previously abundant species and ‘outbreaks’ of prey species (Bakun 2005) and rare species (Myers et al. 2005)

Understanding Life-history Strategies of Fishes Species have evolved life-history strategies to succeed (survive, feed, reproduce) in given niche in a given ecosystem Key components of life-history strategies are size, trophic level, and productivity

Key Trait: Size Small < 6.6 cm Medium Large very large > 323 cm 23,603 species geom. mean 17.4 cm

Key Trait: Trophic Level 7,161 species herbi- vore omnivorelow-level predatormid-level predator top- predator

Key Trait: Productivity (modified after Musick 1999) ParameterHighMediumLowVery low r max (1/year)> – – 0.15< 0.05 t d (years)< > 14 Interest rate (%)> 6517 – < 5 K (1/year)> – – 0.15< 0.05 Fecundity (1/year)> 10, – – 100< 10 t m (years)< 12 – 45 – 10> 10 t max (years)1 – 34 – 1011 – 30> 30

Key Traits: Productivity ProductivitySpeciesPercent r’ max Very low Low Medium High ,511 species

Productivity is a Proxy for Metabolism (routine metabolism of 175 species)

Key Traits are Inter-related Trophic level increases with size Productivity decreases with size Trophic level decreases with productivity

Trait Correlation: Size vs Troph

Trait Correlation: Size vs Productivity

Trait Correlation: Trophic Level vs Productivity

Available Data are Biased Combined available data for 1,880 species are biased towards large, commercial, northern- hemisphere, temperate species Solution: Use modelling approach to expand data base

Expanding the Database: Trophic Level Trophic level of 97 species of Genus Epinephelus as a function of their body length. Top Medium Low

Residuals of Modelled Troph Residual Troph

Expanding the Database: Productivity (K) Von Bertalanffy growth parameter K plotted over maximum length for Family Serranidae High Medium Low Very low

Modelled vs Observed K

Life-History Strategies The extended data set contains 20,480 species, nearing a census Bias towards large northern species has disappeared Of 80 possible combinations of traits (life-history strategies) only 50 are used Three strategies are used by 60% of the species

Occupation of Size-Troph Space

Occupation of Size-Productivity Space

Occupation of Troph-Productivity Space

Summary of Above Species have evolved size, trophic level, and productivity to fit a given niche Fishing alters size, trophic level and productivity thus making species misfits for their niche and prone to collaps

Fishing Down the Food Web Pauly et al. (1998)

Goals of Ecosystem-based Fisheries Minimize direct impact on the environment Minimize impact on abundance –Only catch at optimum size Rebuild & preserve size spectrum –Don’t catch juveniles or mega-spawners Rebuild & preserve trophic diversity Rebuild & preserve productivity –Only catch at optimum size, after first and before second spawning

How ? Establish no-take zones Use non-destructive gears Use size-selective gears Use knowledge and technology Create incentives for ‘good’ fishing Involve stakeholders in monitoring and management

Reality Check DG Fish recommendation for TAC 2006: 28,400 tons (+ 15%)

Thank You Comments? Questions?