Life-history Strategies of Elasmobranchii Rainer Froese IFM-GEOMAR Kiel

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

Most Fishes are Small Frequency distribution of maximum lengths in 23,685 species of fishes. Median = 15.9 cm.

Most Sharks are Large Myxini with median 49 cm; Cephalaspidomorphi with median = 22 cm; Holocephali with median = 99 cm; Elasmobranchii with median = 78 cm; Sarcopterygii with median = 125 cm; and Actinopterygii with median = 16 cm. small medium large very large

Most Fishes are Low-level Predators Frequency distribution of trophic levels for 7,500 species of fishes: median = 3.4 herblow-level predatoromnivoremidtop predator

Most Sharks are Mid-level Predators Trophic level by Class for 7,500 species with available data: Myxini with median = 4.2; Cephalaspidomorphi with median = 4.2; Holocephali with median = 3.5; Elasmobranchii with median = 4.0; Sarcopterygii with median = 3.4; and Actinopterygii with median = 3.4.

How to Estimate Productivity ParameterHighMediumLowVery low r max (1/year)> – – 0.15< 0.05 t d (years)< > 14 Interest rate (%)> 6517 – < 5 K (1/year)> – – 0.2< 0.1 Fecundity (1/year)> 10, – – 100< 10 t m (years)< 12 – 45 – 10> 10 t max (years)1 – 34 – 1011 – 30> 30 Modified after Musick (1999 )

Most Fishes have High Productivity Observed (n = 2,621) and modeled (n = 24,649) productivities of fishes. Source: FishBase 11/2004; Froese 2005

Sharks have Low or Very Low Productivity Class / ProductivityHighMediumLowVery lown r’ max Myxini Cephalaspidomorphi Holocephali Elasmobranchii Sarcopterygii Actinopterygii ,

Occupation of Size-Troph Space

Occupation of Size-Productivity Space

Occupation of size–productivity– troph-space for 20,480 species of fishes. Full cell width is 1000 species.

Occupation of size–productivity– troph-space for 620 species of sharks and rays. Full cell width is 1000 species.

Occupation of size–productivity– troph-space for 620 species of sharks and rays. Full cell width is 145 species.

Competition among Low-level Predators Length group Product.MyxCephHoloElasmoSarcoActino Medium 42,752 Low Very low3151 LargeMedium645 Low Very low Very large Very low55

Competition between Mid-level Predators Length group Product.MyxCephHoloElasmoSarcoActino Medium Low Very low55 LargeMedium368 Low Very low59161 Very largeLow61 Very low72

Competition among Top-Predators Length group ProductivityMyxCephHoloElasm o SarcoActino Medium 98 Low4779 LargeMedium188 Low Very low45244 Very largeMedium4 Low97 Very low172

Strategies vs Species Numbers Number of strategies used by phylogenetic Classes plotted over number of recent species in the Class, with linear regression line forced through the origin; slope = 0.37

Salinity Tolerance 12,889 14,091

Climate Zones 3,194 4,023 16,840

Oceans 4,448 5,592 9,839

Habitat 4,137 9,953 8,732

Relative Brain Size 519

Reproductive Guild

Migratory Behaviour 1,872

Summary Elasmobranchs are the second largest Class of recent fishes They use only 16 life-history strategies compared with 49 used by ray-finned fishes They are mostly large, marine, demersal, migratory, large-brained, long-living mid-level predators of low productivity Their low productivity makes them vulnerable to exploitation and to competition from ray-finned fishes with typically higher productivity

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