l-04(f&feeding) fisheries

8/7/2019 L-04(F&Feeding) fisheries

1/35

Food & Feeding Habits of Larval Stage of FishesDevelopmental Stages-Embryo: Developing fish prior to hatching.

Eleuthero-Embryo: After hatching until first feeding (Oviparous)/ parturition(Viviparous) groups.Larva: Developing fish after initiation of first feeding or parturition until a juvenile

stage (Attainment of full morphological features).

Larval Food:H atchlings- Feed on yolk reserves provided with them.F ry & fingerlings- Because of under-developing small & short intestine prefers to

feed on easily digestible items mainly zooplanktons (protozoans, rotifers,cladocerans and crustaceans larvae).

C hange of F ood Preference: Larvae of Caspian roach (Rutilus r. caspicus) After yolk-sac absorption (metamorphosis stage/ 5-8.5mm) on Volvox,

Rotifers & Copepod naupli. At fry stage (12mm) catches cladocerans At young stage (15mm) pick up insects from bottom

Larvae of culturable carps feed firstly on zoo-and later phytoplanktonand so on

N atural food item(s) dominance: In deep sea (copepods) & Freshwater (Cladocerans & rotifers)


2/35

M ode of Feedingof

Larval Stage of FishesAccording the habitat / food, fish larvae feed

in different ways-

Hatchlings feeding through yolkabsorption and assimilationLarval feeding by food-captureLarval feeding by food-filter Especial feeding through External Gills


3/35

Hatchlings Feeding{Yolk M aterial Absorption & Assimilation}

Yolk material absorption bysyncitial cells of periblastlayer.

Enzymatic digestion of yolkmaterial within above groupof cells.

Digested yolk nutrientreleased within peri-vitellinespace.

Transportation of nutrient toyoung one through peri-vitelline circulation.


4/35

Larval feeding by food-captureLarvae have a regular rhythmic swimmingpattern, where a few tail-beats alternate withperiods of rest, allow economical search of largest possible volume of water for food.

In larvae of My ctophum & Idiacanthus eyes aremounted on stalk to increase visual efficiency of food search (80 times) as compared to larvae of same size with non-ratable eyes.


5/35

Larval feeding by food-filterEspecially A mmocoetelarvae of Lamprey haveunique capability to filter phytoplankton.

Unique arrangement of teeth in larvae of eels andallied groups suggest filter feeding.

Moreover, Leptocephaluslarvae also have capabilityto absorb nutrients fromsea-water via skin.


6/35

Larval feeding through External GillsIn those group of fishes whose larvae bear external gills,

have capability to assimilate dissolved nutrients of water-medium along with D.O.

e.g. Lung-fish (Lepidosiren & Protopterus )Reed-fish (Pol y pterus )

Elasmobranchs (T . mormorata & Squalis acanthias{Spiny dog-fish} )

Larva

Protopterus


7/35

Food, M ethods of Feeding and Habitsof

Adult Fishes

Natural Food Items

D etritus

Benthos

N ekton

Plankton

{Qualitative C ategorization}


8/35

P lankton (Neuston)

Plankton - are category of microscopicorganisms being drifted along with water current whereas neuston are category of plankton which live on surface film of water.

C at eg ori es: (A-Size & B- Ecological Basis)A- Size-Basis-

N anno-plankton (diameter< 0.03mm)Micro-plankton (diameter 0.03-3.0mm)

Macro-plankton (diameter 3.0mm


9/35

B- Ecological Basis-

Haleco-plankton (Pond Plankton)Limno-plankton (Lake Plankton)

Rheo-plankton / Potamo-plankton(Running-water Plankton)Hypalmyro-plankton (Brackish water

Plankton)Halio-plankton (Marine Plankton)


10/35

N e kton : Group of large swimming organismswhich are found in all depths, having

independent movement (crustaceans,cephalopods, fish, snakes etc. )

B e ntho s: Group of organisms live on bottom{Phyto-and Zoo-benthos}, ecologically of following categories-

Rhizo-benthos (rooted in bottom)Hyper-benthos (attached with bottom-mud)Psammon-benthos (attached with sandy bottom)

Hapto/Peri-benthod (attached with sub-merged plants/substratum)Endo-benthos (boring on solid substratum)

D e tritu s: D ead and decomposing plant-materialsby aerobic-bacterial putrefaction action.


11/35

Natural Food Items

Emergency / Obligatory F ood

Incidental F ood

Secondary F ood

Main / Basic F ood

{Quantitative C ategorization}

N atural food preferred by fish under favorable conditions.

Consumed by fish if/ when available.

Rarely recorded in gut-content & entersalong with other items by chance.Taken by fish for survival under

unfavorable conditions.


12/35

T ype of Food

Items

Quality of FoodItems

Specializationof F ood Items

Feeding

Habits

Steno-phagic (Labeo rohita, Ctenophar y ngodon idilla )

Eury-phagic (Cirrhinus mrigala, C y prinus carpio varieties)

Mono-phagic (Catla catla, H y pophthalmichth y sic molitrix)

Plankton F eeder (H. ilisha, C, catla )

Omnivorous (T or sps., Puntius sps)

H erbivorous (Schizothorax sps, O.gorami )

C arnivorous (Catfishes & Murrels)

Larvirous (G ambusia affinis, Chela sps., Ox y gaster sps.)

Insectivores ( Channa sp., Esomus sps.)

Cannibilistic (C. batrachus & Murrel species)

C arciniphagous (A nabas testidinius,

Malacophagous (G . chapra, C. garipienus )


13/35

M ode of Feeding

Basic Waysof Feeding

By Predation (S elective feeding on fish / aquatic animals)

By Parasitism (sucking body fluid from body of host)

By Grazing / Browsing (Indiscriminate feeding on all sort of items)

By Staining (S elective feeding on living microorganisms)

By Sucking (Indiscriminate feeding on semi-solid materials)


14/35

C ommonest M ethod of FeedingP rey C apture: It is commonest method of

feeding being followed by majority of commerciallyimportant fish-groups in Two-ways-

R am-feeding- Rapid swimming, ramming water through mouth and out through opercular opening.

Suction F eeding: Fish creates a strong inwarddirected water current by rapid expansion of buccal cavity while stationary.

In modern fishes, jaws are shortened to limit gapwhile expansibility of buccal cavity is maintainedresulting in increased water velocity throughsmaller mouth when cavity is expanded.

{Being completed in 3-phagic motions of Buccal cavity}


15/35

Mu scu lar mechanism involved in s u ction feeding


16/35

Diversified Way of Feeding of Lake Malawi Cichlid Fish(Petrotilapia tridentiger )

V ertical scraping of algae Scraping down algaeManipulate feeding Biting of fishSlow upward catch Slow downward feeding

Slow horizontal feedingF

ast suction feeding


17/35

F ood & F ee din g Habit{C omm e rcial Group of F is h es}

C arp s-

Catla catla Zooplankton, larvae of insects &crustaceans, unicellular algae,microscopic plants etc.

Labeo species Decaying plants, uni-multi(filamentous) algae, microscopicplants, mud etc.

Cirrhinus mrigala Decaying plants & animals, algae,detritus, mud etc.

H. molitrix Unicelluar algae, rotifers, protozoans,decaying plants etc.C. idella Aquatic vegetation

C. carpio varieties All sort of living / non-living, dead &

decaying materials etc.


18/35

F ood & F ee din g Habit{C omm e rcial Group of F is h es}

C arnivor es-

C. batrachus Insects, fish-fry, decaying matters etc.

H. fossilis Insects-worms-copepods-alge, debris etc.

Channa species Insects, fish-fry, frog-tadpoles etc.

Wallago attu Insects, fish-fry, frog-tadpoles etc.

My stus species Insects, fish-fry, frog-tadpoles etc.M is c e llan e ou s-

A . testudineus Insects, their larvae, aquatic plants etc.

O. goram y Insects, their larvae, algae, aquatic plants

O. mossambicus Insects-crustaceans-larvae, filamentousalgae, aquatic plants etc.


19/35

Food & Feeding Habit Associated M odificationin Digestive System of C ommercial

Group of Fishes

Oral Openings (Jaws & Labial Folds)

Bucco- pharynx (Gill-rakers, Teeth, Taste-buds & mucous glands)

Intestine & R ectum (Length, S piral-Valves & S alt-secreting glands)

Oes o phag u s ( D istensability)Mod ifi c ati o ns in

St om a c h (shape, Size & Musculature)


20/35

O ral O penings & Labial Folds

O ral O penings-Upturn in plankton feedersTerminal in column feedersDownward in bottom feeders

Labial Folds-Thin, smooth & short in plankton feedersThick, may be fringed / multiple lower ones in

column feedersThick, bulging & protractible in bottom feedersThick with tubercles & suckers / adhesive-pad on

lower side in hill-stream fishes


21/35

Labial FoldsL. dy ocheilus (continuous)

L. d ero (interrupted)

T. progenius (fan-shapes)

G . got y la (S uctorial-disc)

L. f isheri (horny jaw-ridge)


22/35

Bucco-pharynx (Gill-rakers)

In Predatory Carnivores, gill-rakers are modified in form of teeth like structures.

In plankton-feeders, gill-rakers are elongated & forming sieve-like network.

In purely herbivores, gill-rakers are serrated; in obligatory onethey are short, stumpy & stout.

In omnivores also, gill-rakers are prominently serrated.


23/35

Bucco-pharynx (Teeth)

In herbivores, plankton-feeders & purely omnivores,only inferior pharyngeal teeth are present &posterior narrow pharyngeal region performmastigatory function.

In facultative omnivores (Eutropichth y es vacha , C. batrachus )minute teeth are present on jaws.

In predatory carnivores, various type jaws & alsosuperior+inferior pharyngeal theeth are present.

A typical H erbivore A typical C arnivore


24/35

V arious type teeth in exclusive predatory carnivores [ M arine]

P y lo d ictis olivarisChaulio d is sloani


25/35


26/35

Histological O rganization of Bucco-pharynx

In a typical teleost fish,bucco-pharyngeallining is composed of thick layer of stratifiedepithelial cells.

Below that is S tratumMalpighii layer.

S uperficially a largenumber of mucouscells are present.

S ub-mucosa iscomposed of denseconnective tissue.


27/35

Bucco-pharynx of C ulturable C arps

C . catla

C . m rigala C . carpio

H . m ollitrix

C . i d ella

L. rohita


28/35

Oesophagus (Distensibility)

It is so distesible thatcan accommodate anything that a fish can getinto mouth, even larger than that.

In herbivores/omnivores: S hort& narrow tube-like.In Predatory carnivores: Large &

distensible.Histologically, have mucous-

cells & taste-buds in mucosallayer.In mucosal fold of anterior region, stratified epithelial layer & in posterior region columnar epithelial layer is present.

T. S . of an Omnivorous fish

LP


29/35

Stomach (Shape, Size & Musculature)

On basis of food & feeding habit of fishes,stomach is characterized by shape, size &musculature.Histologically it is characterized by presence

of inner most thick layer of gastric-glands.In general in following group of fishes True

S tomach is absent: Cyprinids (carps), Holocephali

(Chimaera) & Dipnoi (Lung-fish).In above case false stomach is modifiedfrom anterior most part of intestine in form of Intestinal Bulb.


30/35

{A} O mnivores- S tomach is more often sac-shapelike-human & projecting thick enfolding of gastricglands.

Further in those more often feeding on fatty (wax)materials, it has presence of pyloric caecae also.


31/35

{B} P redatory- C arnivores- It is typically quiteelongated to accommodate large-sized prey,

projecting thick longitudinal enfolding of gastric-glands.

Further having pyloric caecae also.


32/35

{C } P lanktonivores (H. ilisha & G. chapra ) &Bottom-grubbers (M . cephalus, Acipenser &

Dormosa )-It is reduced & modified in form of

Gizzard like structure for triturating hard-sandcontaining food material.

Further having pyloric caecae also.


33/35

Histological O rganization of StomachHistologicallystomach is lined bythick well-vascularzedmuscular wall.

From interor side ithas columnar epithelial layer raised into primary &secondaryenfoldings.

Below columnar layer, gastric-glandsare positioned.


34/35

Intestine & Rectum {Length, Spiral- V alve System & Glands}Intestine-

S hort & straight in carnivorous-predatory fishes.

Long & highly coiled in herbivores (Phytoplanktoners), containing hepato-pancreatic tissue among coils but in purely herbivores (C. idella ) of moderate size .

In purely omnivores, it is shorter than herbivores (C. carpio ).Presence of intestinal caecae (N otopterus, Mastecembalus, Hilsa, Channa,

Harpodon ) provide more effective absorptive surface area & act as seatfor Lipase biosynthesis & secretion.Like micro-villi supported epithelial lining in intestine of teleostei to

increase effective absorptive surface area in chondrichthyes & dipnoifishes spiral-valve system is developed. It is also found but lessprominent in some primitive bony fishes (Amia, Polypterus &Osteoglossids ).

In R ectum of majority of marine chodrichthyes fishes &exceptionally in one of bony fish (L atimaeria ) salt-secretingrectal glands are found for osmoregulatory functions.


35/35

Histological O rganization of IntestineIn herbivorous-cum-omnivorous (C.

mrigala ), instestine has thin

muscular wall & mucosal partthrown into prominent folds.Mucosal foldings have micro-villibearing absorptive cells of Micro-villi are more prominent inproximal part to increase effectiveabsorptive surface area for digested nutrient assimilation.

Mucous-glands more in anterior,least in middle & increaseconsiderably in posterior parts.

In carnivorous-cum-omnivorous (C.batrachus ) fish, inestinal wall iscomposed of thick muscular wall &micro-villi supported epithelialenfoldings of columnar cells areless developed.

A

B

T. S .

Intestine of C. mrigala[A-Anterior

& B-P osteriorregions]

l-04(f&feeding) fisheries

Documents