food and feeding in fishes

1. Jayachandran PR
FOOD AND FEEDIG IN FISHES

2. DETRITUS
BENTHOSNEKTON
PLANKTON
Based on niches
Hutchinson 1967:
• Rhizobenthos
• Hyperbenthos
• Psammon
• Haptobenthos or
periphyton
• Endobenthos
(boring)
NATURAL
FOOD OF
FISHES
Phytobenthos
Zoobenthos
Settled detritus
Suspended
Pseudo
plankton
Euplankton
Phyto
plankton
Zoo
plankton
Epifauna
Infauna

3. Ecologically /water body
(Jhingran,1983)
1. Heleoplankton (pond)
2. Limnoplankton (lake)
3. Rheoplankton or
Potamoplankton
(running water)
4. Hypalmyroplankton
(brackish )
5. Halioplankton
(marine)
Meroplankton
Zoo
plankton
Phyto
plankton
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

5. TYPES OF FEEDING
(Schaperclaus, 1933)
Occasional
food
Emergency
food
Main and Natural food
Nikolsky(1963)
Basic food
Secondary
food
Incidental
food
Obligatory food

6. Based on amount of food
Monophagic
Eury phagicStenophagic
Surface
feeders
eg. Catla
Marginal
feeders
eg. Rohu
Bottom
feeders
Eg. Mrigal
Mid feeders
(cloumn
feeder)
nagendram fish
(Osteochilus
thomassi)
Based on trophic niche

7. Moitra 1963
Carnivorous Omnivorous
Herbivorous
Planktophagus
Detritophagus
Herbi -omnivore
Carni -omnivore
Insectivorous
Carciniphagus
Malacophagus
Piscivorous
Larvivorous
Cannibilistic

8. • Relative Gut Length(RGL)(𝐴𝑙 − 𝐻𝑢𝑠𝑠𝑎𝑖𝑛𝑦, 1949) =
𝑳𝒆𝒏𝒈𝒉𝒕𝒉 𝒐𝒇 𝒕𝒉𝒆 𝒈𝒖𝒕
𝑻𝒐𝒕𝒂𝒍 𝒃𝒐𝒅𝒚 𝒍𝒆𝒏𝒈𝒕𝒉
• Index of fullnes (Shorying,1952)=
𝒘 𝑿 𝟏𝟎 𝟒
𝑾
W=weight of gut content, W = weight of the fish
• Gastro somatic Index (GSI) (Desai, 1970) =
𝑾𝒆𝒊𝒈𝒉𝒕 𝒐𝒇 𝒕𝒉𝒆 𝒈𝒖𝒕
𝑻𝒐𝒕𝒂𝒍 𝒘𝒆𝒊𝒈𝒉𝒕 𝒐𝒇 𝒕𝒉𝒆 𝒇𝒊𝒔𝒉
• Rate of digestion:
(Expressed as no. Hours taken for digestion)
1. Direct method
2. X-ray method(for piscivorous)

9. 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

10. • Forage ratio and food selectivity indices
• Index of preponderance
• Index of relative importance (IRI) Srivastava, 1985 = (n+v)f
n & 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

11. Thank you