food and feeding in fishes

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