1. Schooling & Migration Groupings of fishes Schooling characteristics
Fish migrations
Examples

2. Grouping of Fishes Social grouping of fishes
Shoals: unorganized
Schools: organized & with polarized swimming
Groupings caused due to resources
Aggregations
Feeding
Spawning

3. Social
Groupings

4. Why of Schools? Predation avoidance Dilution effect Trafalgar effect
Confusion effect

5. Battle of Trafalgar – Admiral Nelson

8. Why of Schools? Reduction of predatory success
Dilution effect
Trafalgar effect
Confusion effect
Increase feeding efficiency

9. Why of Aggregations? Reduction of predatory success
Dilution effect
Trafalgar effect
Confusion effect
Increase feeding efficiency
Synchronize spawning activities

11. Fish Migrations Mass movement between habitats Oceanodromy (SW)
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)

12. Oceanodromy
Scombridae
Albacore
Thunnus alalunga

13. Diadromy
(Birth, Growth, Reprod.)

14. Migration Benefits & Costs
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

16. Why Diadromy? Rapid Growth to Adult Size
High Oceanic Productivity at high latitudes
Low Oceanic Productivity at low latitudes
Survival benefits of offspring

19. Tsukamoto et al

23. General Oncorhinchus spp. migration path

24. How do fish orient themselves?
Sun position and polarized light
Geomagnetic and geoelectric fields
Currents (rheotaxis)
Olfaction
Temperature isolines

27. Metamorphosis of leptocephalus larva into glass eel stage and then to early pigmented eel stage

29. Tsukamoto et al

30. Tsukamoto et al

31. Tsukamoto et al

32. Tsukamoto et al

33. 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

35. Black Marlin sport fishery tagging

36. 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

37. 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 = (M*n)/R
Accuracy Estimates Available

38. Binary Code Tag
Pit Tag

39. Otolith marking

41. Bluefin Tuna – Archival tags
Traditional tagging (need to recapture fish)

42. Average Annual Catches of Yellowfin tuna
PURSE SEINE
Average Annual Catches of Yellowfin tuna

43. Pop-up satellite tags

44. Pop-up satellite tags

45. Pop-up Satellite tags