Life-History Strategies of Fishes Rainer Froese IfM-GEOMAR

Classes of Fishes

There are Six Classes of Fishes ClassesCommon ancestor (million y) Orders (n) Families (n) Genera (n) Species (n, %) Myxini (hagfishes) Cephalaspidomorphi (lampreys) Holocephali (chimaeras) Elasmobranchii (sharks and rays) Sarcopterygii (lobe-finned fishes) Actinopterygii (ray-finned fishes) ,64028, Total ,84029, Source: FishBase 09/2006

Key Trait: Size smallmediumlargevery large 23,603 species

Size Matters Largest fish: Whale shark, 20 m, 34 t Smallest fish: attached male anglerfish, several tiny cyprinids & gobies, 1 cm, 0.01g Max growth rate, fecundity, speed, trophic level, life span increase with size Relative metabolism, growth, brain size, gill area and M decrease with size

What You Eat You Are (+1) Trophic level Phytoplankton Top predators Prey fish Zooplankton * *.*. *.*  10% *

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 Very low Low Medium High ,511 species

Productivity is a Proxy for Metabolism

Trait Correlation: Size vs Troph

Predators are Larger than Prey

Trait Correlation: Size vs Productivity

Phylogeny Limits Traits: Size Hagfish Lampreys Chimaeras Sharks & rays Lobe-finned Ray-finned small medium large very large

Phylogeny Limits Traits: Troph Hagfish Lampreys Chimaeras Sharks & rays Lobe-finned Ray-finned

Phylogeny Limits Traits: Productivity ClassProductivitySpeciesPercent MyxiniLow66100 CephalaspidomorphiLow1636 Medium25 HolocephaliLow37100 ElasmobranchiiVery low20621 Low52855 SarcopterygiiVery low1091 ActinopterygiiVery low470.2 Low Medium High3531.3

Life-History Strategies Of 80 possible combinations of size, trophic level and productivity, only 50 are used by recent fishes Three strategies are used by 60% of the species

Occupation of Size-Troph Space

Occupation of Size-Productivity Space

Occupation of Troph-Productivity Space

Occupation of size–productivity– troph-space for 20,480 species of fishes. Full cell width is 1000 species. Source: FishBase 11/2004

Occupation of size–productivity– troph-space for 620 species of sharks and rays. Full cell width is 1000 species. Source: FishBase 11/2004

Life Span and Growth Taylor 1958 Age at 0.95 L ∞ t max = 3/K

Life Span and Size

Life Span and Mortality where Ex is the average life expectancy after reaching age x and l are the probabilities of reaching x and subsequent ages. In adults mortality is constant and then Note that E is also the mean duration of the reproductive phase, where in stable populations one replacement spawner is produced per spawner

The Most Important Point in Life where growth rate is maximum where gonad growth rate is maximum where likely reproductive effort is maximum (l t m t function) where reproductive biomass of the cohort is maximum t opt = 1.65 E

The Most Important Point in Life t opt = 1.65 E L opt = 0.67 L ∞ W opt = 0.3 W ∞

Not Missing the Point Means… Include t opt in mean life expectancy Reproduce at t opt Mature so that reproductive phase E includes t opt –Early t m = t opt – E –Latet m = t opt

Example Atlantic Cod

Evolution Does Not Miss… 0.67 L ∞ = t opt 0.35 L ∞ = t opt - E live bearers sharks & rays low fecundity high fecundity survival of offspring Related to parent size survival of offspring indepenent of parent size

But Fishing Does… Start before first maturity Double mortality (if not more) E = 1/M Reduce reproductive phase by half Undermine the productivity on which it depends

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