29. Apr 2021

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  1. Feeding types- filter feeders, carnivores, omnivores and their trophic levels. Ontogenic changes in feeding- Forage theory- Mismatch hypothesis of Cushing. Presented by- Parul FRM Dpt. (2020FS06M) CCSAU,Hisar FRM-509
  2. Categories of food Food available in the nature can be classified as Plankton, Nekton, Benthos and Detritus • Plankton : Plankton is microscopic organisms with little or no power of locomotion. They drift at the mercy of water currents. They are broadly grouped into 2 categories depending on the presence or absence of plant pigments. 1. Phytoplankton – having chlorophyll in the cells e.g. Diatoms, Dinoflagellates 2. Zooplankton – without chlorophyll e.g. Copepods, crustacean larvae, other microscopic invertebrates
  3. Cont….  Nekton : Nekton are actively swimming organisms capable of independent movement. They actively maintain their position despite the drifting water currents. They may be present at the surface (pelagic) or at the bottom (demersal) of water column. e.g. fishes, shrimps, cuttlefishes and squids.  Benthos : These are bottom dwellers with little (sessile) or no movement (sedentary). They are mostly invertebrates living on the substratum. e.g. annelid worms, bivalves, gastropods etc., benthos are of two types i) phytobenthos and ii) zoobenthos.  Detritus : It is the dead and decayed organic matter of both plant and animal origin. Decomposing bits of leaves, twigs, barks, water plants and animals form detritus. It can be in particulate or suspended form associated with rich microbial flora and fecal matter.
  4. Type of feeding Natural feed. Supplementary feeds. Complete feeds.
  5. Natural feeds  Natural feed is found naturally in the pond .It may include detritus, bacteria, plankton worms, insects, snails, aquatic plants and fish. Their abundance greatly organic depend on water quality .
  6. Supplementary feeds  Supplementary feeds are feeds regularly distributed to the fish in the pond. They usually consist of cheap material locally available such as terrestrial plants, kitchen wastes or agricultural by products.
  7. Complete feeds  Complete feeds may also be regularly distributed. They are made from a mixture of carefully selected ingredients to provide all the nutrients necessary for the fish to grow well. They must be made in a form which the fish find easy to eat and digest. These feeds are quite difficult to make on the farm and are usually quite expensive to buy
  8. Filter feeders Filter feeders are a sub group of suspension feeding animals that feed by streing suspended matter and food particles from water, typically by passing the water over a specialized filtering structure. Some animal that used this method of feeding are clams, krill, sponges, Balvn whales and many fish. Filter feeders can play on important role in clarification water and are therefore ecosystem. They are also important in bioaccumulation and as a result as indicator organisms.
  9.  Feeding on both plant and animal matter.  An omnivore will eat a variety of meat and vegetable matter.  Their teeth and digestive tract possess same of the traits of both the carnivore and herbivore.  Although omnivores can and will eat vegetable matter, they cannot digest some type grains and plants.  Ex- Etroplus suratensis, Cyprinus carpio, Tor putitora, Clarias batrachus Omnivorous
  10.  They are meat eating and generally requiring live foods.  They have large mouth with sharp pointed teeth.  Carnivorous has a short intestinal tract and a relatively large stomach designed to hold on entire fish.  Wallago attu, Mystus singhala, Channa striatus. Carnivorous
  11.  Carcinovorous- Mainly feeding on crustacean. Ex-Black bass Insectivorous-Mainly feeding on insects . Ex- Trout
  12.  Malacovorous- Feeding manly molluscs like snail/clam, black crab. Piscivorous– Feeding on fish other than its own species. But generally they preyupon small fishes of other species rather than their own. Ex-barracuda.
  13.  Cannibalistic Feeding on the young ones of the same species. Ex-channa marulias, lates calcarifer  Larvivorous Feeding mainly in insect and crustacean larvae /fish larva. Ex-Gambusia offinis
  14. Dependence on food type  In nature, the type of food available does not remain the same throughout.  Therefore, fish may change over to other available food or restrict to a limited type and the fishes are classified as: 1. Euryphagic : Fishes feeding on a mixed diet with no preference to any certain type. 2. Stenophagic : Fishes feeding on limited kinds of food. 3. Monophagic : Fishes consuming only one kind of food.
  15.  Food webs largely define ecosystem, and the tropic levels define the position of organisms within the webs.  But there tropic levels are not always simple integers, because organisms often feed at more than one tropic level.  The feeding habits of a juvenile animal, and consequently its trophic level, can change as it grows up.  Trophic levels
  16. 1)In plants and detritus 2)In herbivores and detritivores (primary consumer )  In secondary consumers.  At the base of the food chain lies the primary producer  Primary producers are principally green plant and certain bacteria. Daniel Pauly sets the values of tropic levels to one
  17.  They convert solar energy into organic energy.  Above the primary producers are the consumers who ingest live plants or the prey of other.  Decomposers, such as bacteria, molds and fungi make use of energy stored in already dead plant and animal tissues.  Fungi, like mushroom, absorb nutrients from the organisms by secreting enzymes to break up the chemical compounds that make up dead plants and animals.  Trophic levels can be represented by numbers, starting at level 1 with plants.  Further trophic levels are numbered subsequently according to how far the organism is along the food chain.
  18.  Level 1: Plants and algae make their own food and are called primary producers.  Level 2: Herbivores eat plants and are called primary consumers.  Level 3: Carnivores which eat herbivores are called secondary consumers.  Level4: Carnivores which eat other carnivores are called tertiary consumers.  Level5: Apex predators which have no predators are at the top of the food.
  19. Three different food chains are recognised. Carnivore chain- where the energy passed from smaller to large organisms. Parasite chain- where the energy is passed from large to small organisms. Saprophyte chain- where the energy is passed from dead organic matter to micro organisms. Food chain and food web
  20.  Food is passed through all parts of these chains before decomposed to inorganic nutrients by bacteria and fungi. The species population within a community or ecosystem forms many food chain which interconnect or cross each other in a complex pattern is referred as food web. Food web
  21. Ontogenic change in feeding  Ontogenic change in feeding refer to the change in organism resource use pattern as it increases in size from birth or hatchling to its maximum.  Besides the body size, many other important factors like predation risk and susceptibility to physical factors also affect the feeding behaviour of the organism.  So many species undergo exterisive ontogenic shifts in food and habitat use based on their resource utilizing abilities and predation risk.  As most fish species continue to grow in their life(wootton,1998).  The substantial increase in body size that a fish achieves during ontogeny has an implication for species interaction(werner & gilliam, 1984)
  22.  The diets of most fishes change with growth, but the timing of there change varies from species to species and is often associated with change in lifestyles or habitats(blaber,2000)  The ultimate objective of ontogenetic change is to maximize energy intake, enhance growth rate and minimize the risk of predation.  The rapid growth of fish is obvious in the first year, and as it grows it is capable of handling large size foods.  This is also the period when their diets change rapidly.  Ontogenic shifts are not only for the species that metamorphose, but also approximated in many groups where morphology simply change allometrically with growth.  Yellow perch(Perca flavescens), small mouth bass (Micropterus dolomieui) and largemouth bass (M. Salmoides) shifts their diet from small entomostracans to insects and fish in later stage(clay, 1974)
  23. Some of the major factores affecting Ontogenic change in feeding in fishes
  24.  OFT is a behavioral ecology modal that helps predict how an fish behaves when searching for food.  Although obtaining food provide the fish with energy, searching for and capturing the food require both energy and time.  To maximize fitness, an fish adopts a foraging strategy that provides the most benefit for the best lowest cost, maximizing the net energy gained.  OFT helps predict the best strategy that an fish can use to achieve this goal. Optimal forage theory(OFT)
  25. Mismatch hypothesis of Cushing  The hypothesis focused on the timing, as a function of the blooms of primary producers.  Blooms of phytoplankton directly influence the increased population size of zooplankton, as the phytoplankton are the primary food source for zooplankton.  Most pelagic fish, in their larval stages, feed directly upon the phytoplankton and zooplankton.  So as logic follows, large population of phytoplankton will support large populations of zooplankton, and the presence of both will sustain larval fishing.  As Cushing noticed, however, there are climatic influences where temperature anomalies will inhibit phytoplankton blooms, or impact the range of the bloom.
  26. References  https.//en wiki Filter feeder.  omnivore- herbivore-carnivore-1380916  http ecourse online jasti.res in mod'pa/view php?id 85343  Dr. P.U. Zacharia Trophic levels and Food chain Head, Demersal Fisheries Division CMFRI. Kochi  326232367 Ontogenic Changes Feeding in Fishes.  berry
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