• migrate long distances too.

Types of Migration

Myers (1949) – 3 main categories:

• Diadromons fishes – migrate between sea & fresh water
  • Anadromous – major part sea but fresh water during breeding season e.g. Salmon & Hisla
  • Catadromous – major part fresh water but sea during breeding e.g. Anguilla (eel fish)
  • Amphidramons – fresh water to sea & vice versa. Eg. Gobies
• Potamodromons – migratory, confined to fresh water eg. Corps and trouts, Mahasees move up stream along Himalaya rivers
• Oceanodromons – migratory, confined to sea only eg. Tunnas, Mackerels

Causes of migration in fishes

Heape (1961) – 4 primary reasons of fish migration

• Gametic migration (Spawning/breeding migration)
  • Better survival & proper development of egg/larva
  • Stop feeding prior to migration or reduced drastically
  • Energy requirement (fat deposit) e.g. Chum salmon spp. 25,810 Ca & 28,390 cal by male and female respectively
• Alimental of Feeding Migration
  • Due to shortage of food (Suitable/wintering/spwing)
  • Better food facilities, better survival & fast growth
  • Grow fast in size & mature & produce more eggs.
• Climate or Wintering Migration
  • Due to inactive physical condition and low BMR (Basic Metabolic rate)
  • Depends on fish condition and environment
  • Achieved by hormonal and physiological changes
  • Deposit mainly as fat deposits
  • Among freshwater species (Grass corp.) more to wintering grounds.
• Osmoregulatory or Protective Migration
  • Spwing, feeding & wintering migration can all be regards as protection migration as they ensure further life of fish
  • These migration are not cyclical

Methods of study

1. Marking and tagging (Scale marking or removal)
2. Fisheries statistics (different areas at specific time)
3. Echo ranging techniques (modern & accurate)
   • Similar to echo location in bats by ultra sound emitted in small ship
   • Indicates presence of shoals and depth at which present
4. Direct observation (Land, ship or aircraft)

Marking and Tagging

1. Physical Marking
   • Caught and clip fins
   • Used for short term only
2. Internal Marking
   • Metallic marking introduced within the body cavity by marking guns
   • Electro marking detectors & prevent from conniving
3. External Marking
   • Body surfaces or gill over or pretention bose
   • Two celluloid disc esp. Flat fishes
4. Lea hydrostatic tagging
   • Used for long distance migrants like cods
   • Small celluloid cylinder, remains hermetically sealed
   • Information kept (address)
5. Numbered boit hook tagging
   • Red fish & deep sea fishes are used
   • When brought up dia
6. Plastic flag tagging
   • Used in cods
   • Attached in back of fish by braided nylon thread

Echo-ranging technqiue

1. Acoustic transpending compass system
   • Monitoring (position depth and direction)
   • Small radio transmitter is fitted
2. Ultrasonic transmiltor system
   • Fitted in body cavity
   • For migratory study (Sulmen)
   • Nocturnal movement can be found.