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Jayachandran PR
FOOD AND FEEDIG IN FISHES
DETRITUS
BENTHOSNEKTON
PLANKTONBased on nichesHutchinson 1967:• Rhizobenthos• Hyperbenthos• Psammon• Haptobenthos or
periphyton• Endobenthos
(boring)
NATURAL FOOD OF
FISHESPhytobenthos
Zoobenthos
Settled detritus
Suspended
Pseudoplankton
Euplankton
Phytoplankton
Zooplankton
Epifauna
Infauna
Ecologically /water body(Jhingran,1983)1. Heleoplankton (pond)2. Limnoplankton (lake)3. Rheoplankton or
Potamoplankton (running water)
4. Hypalmyroplankton (brackish )
5. Halioplankton (marine)
Meroplankton
Zooplankton
Phytoplankton
Holoplankton
Omori and Ikeda (1984) Net plankton• Megaloplankton –>20 mm, jellyfish• Micronekton –20–200 mm, euphausids• Macroplankton –2–20 mm, copepods• Mesoplankton –200 µm–2 mm, cladocerans
Water bottle plankton • Microplankton –20-200µm, copepod nauplii, most phyto • Nanoplankton –2–20 µm,fungi, small diatoms,• Ultraplankton or picoplankton – <2 µm, Mainly bacteria
and cyanobacteria,.
Bacillariophyceae
Dinophycea
Cynophyceae
Chlorophyceae
TYPES OF FEEDING(Schaperclaus, 1933)
Occasional food
Emergency food
Main and Natural food
Nikolsky(1963)
Basic food
Secondary food
Incidental food
Obligatory food
Based on amount of food
Monophagic
Eury phagicStenophagic
Surface feeders
eg. CatlaMarginal feeders
eg. Rohu
Bottom feeders
Eg. Mrigal
Mid feeders (cloumn feeder)
nagendram fish (Osteochilus
thomassi)
Based on trophic niche
Moitra 1963Carnivorous Omnivorous
Herbivorous
Planktophagus
Detritophagus
Herbi -omnivore
Carni -omnivore
Insectivorous
Carciniphagus
Malacophagus
Piscivorous
Larvivorous
Cannibilistic
• Relative Gut Length(RGL)
• Index of fullnes (Shorying,1952)
W=weight of gut content, W = weight of the fish
• Gastro somatic Index (GSI) (Desai, 1970) =
• Rate of digestion:
(Expressed as no. Hours taken for digestion)
1. Direct method
2. X-ray method(for piscivorous)
1. Numeric- Occurrence method (Presence/absence), Number method (%), Dominance method, Point (numerical)method,
2. Volumetric- Eye estimation, Point (volumetric ) method, Displacement method
3. Gravimetric-
QUANTITATIVE AND QUALITATIVE ANALYSIS OF GUT CONTENT
• Forage ratio and food selectivity indices
• Index of preponderance
• Index of relative importance (IRI) Srivastava, 1985 = (n+v)fn & v - numerical and volumetric % of food, f - frequency of occurrence in %
Forage ratio= % food make total stomach % total population food in environment
FR=1, selected random, FR= <1, unavail/not selected, FR=>1 food selected /easily avail
STRUCTURAL MODIFICATION IN RELATION TO FEEDING HABIT
Thank you
