What is a Fish?

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Schooling Migration
Groupings of fishes Schooling characteristics Fish
migrations Examples
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Grouping of Fishes

• Social grouping of fishes
• Shoals unorganized
• Schools organized with polarized swimming
• Groupings caused due to resources
• Aggregations
• Feeding
• Spawning

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Social Groupings
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Why of Schools?

• Predation avoidance
• Dilution effect
• Trafalgar effect
• Confusion effect

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Battle of Trafalgar Admiral Nelson
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Why of Schools?

• Reduction of predatory success
• Dilution effect
• Trafalgar effect
• Confusion effect
• Increase feeding efficiency

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Why of Aggregations?

• Reduction of predatory success
• Dilution effect
• Trafalgar effect
• Confusion effect
• Increase feeding efficiency
• Synchronize spawning activities

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Fish Migrations

• Mass movement between habitats
• Regular in time
• According to life history
• Oceanodromy (SW)
• Potamodromy (FW)
• Diadromy
• Anadromy (to FW to breed)
• Catadromy (to SW to breed)
• Amphidromy (not to breed, between SE FW)

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Oceanodromy
Scombridae Albacore Thunnus alalunga
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Diadromy
(Birth, Growth, Reprod.)
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Migration Benefits Costs

• Benefits
• Feeding
• Avoidance of adverse conditions
• Reproduction
• Costs
• Energy expenditure
• Shad up Connecticut River 50 energy reserves
• Increased predation
• For migration to evolve and be maintained,
  benefits must exceed costs

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Why Diadromy?

• Rapid Growth to Adult Size
• High Oceanic Productivity at high latitudes
• Low Oceanic Productivity at low latitudes
• Survival benefits of offspring

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Tsukamoto et al. 20002
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General Oncorhinchus spp. migration path
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How do fish orient themselves?

• Sun position and polarized light
• Geomagnetic and geoelectric fields
• Currents (rheotaxis)
• Olfaction
• Temperature isolines

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Metamorphosis of leptocephalus larva into glass
eel stage and then to early pigmented eel stage
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Tsukamoto et al. 20002
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Tsukamoto et al. 20002
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Tsukamoto et al. 20002
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Tsukamoto et al. 20002
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Tagging as a way of studying migrations

• Recovery tags
• Spaghetti tags
• Pit tags, binary code bars
• Recorder Tags
• Body markings
• Paint marks
• Otolith marking
• Satellite Pop-Tags

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Black Marlin sport fishery tagging
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Estimates of Population Size

• Proportional sampling
• Rp size of the range of the population (Rp),
  (uniform distribution)
• Rs size of sampling a region
• Ns/Np Rs/Rp.
• Np (Ns Rp)/Rs Population Abundance
• No Accuracy Estimate

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Estimates of Population Size

• Mark Recapture
• capture mark release - recapture
• Np population abundance
• M number of individuals that are marked
• n size of the second sample of organisms
• R number of marked organisms in second sample
• Np (Mn)/R
• Accuracy Estimates Available

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Binary Code Tag
Pit Tag
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Otolith marking
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Bluefin Tuna Archival tags
Traditional tagging (need to recapture fish)
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PURSE SEINE Average Annual Catches of Yellowfin
tuna 1996-98
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Pop-up satellite tags
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Pop-up satellite tags
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Pop-up Satellite tags