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Freshwater Zooplankton: An introduction & Their Role In Aquaculture

Aman Singh1, S.K.Sharma2, Varun Mishra1, Ekta Singh1



1Research Scholar, College of Fisheries, Guru Govind Singh Marg, MPUAT, Udaipur 313001(India), m: 91-9782241997



2Professor, College of Fisheries, Govind Singh Marg, MPUAT, Udaipur- 313001(India), m:

91-9352519189

Corresponding author: varunmisra.misra@gmail.com



INTRODUCTION:



Plankton:

The plankton are minute, microscopic organisms of plants & animal origin. They spend their whole life in the water. For their movement, they depend on the mercy of physical conditions of the water body and environment e.g. depth, water current, wind, light, air etc.

Classification of plankton

1. On the basis of quality:

a.) Phytoplankton - Plant plankton

b.) Zooplankton - Animal plankton

2. On the basis of size:

a.) Macroplankton - The larger units of plankton, visible to the unaided eye.

b.) Netplankton (mesoplankton) - Plankton secured by the plankton net equipped with

No. 25 silk bolting cloth.

c.) Nanoplankton (microplankton) - Very minute plankton not secured by the

plankton net with No.25 silk bolting cloth.

3. On the basis of local environmental distribution:

a.) Limnoplankton - lake plankton.

b.) Rheoplankton (potamoplankton) - running - water plankton.

c.) Heleoplankton - pond plankton.

d.) Halioplankton - salt - water plankton.

e.) Hypalymyroplankton - brackish -water plankton.

4.On the basis of origin:

a.) Autogenetic plankton - plankton produce locally.

b.) Allogenetic plankton - plankton introduced from other localities.

5.On the basis of content:

a.) Euplankton - true plankton.

b.) Psedoplankton - debris mingled in plankton.

6. On the basis of life history:

a.) Holoplankton - organisms free-floating

throughout their life.

b.) Metoplankton - organisms free-floating

only at certain times or stage of lifecycle.



What Are zooplankton?


Zooplankton are small animals that float freely in the water column of lakes and oceans and whose distribution is primarily determined by water currents and mixing. The zooplankton community of most lakes ranges in size from a few tens of microns (Protozoa) to >2 mm (macrozooplankton). In terms of biomass and productivity, the dominant groups of zooplankton in most lakes are Crustacea and Rotifera and these protocols emphasize those groups. Zooplankton play a pivotal role in aquatic food webs because they are important food for fish and invertebrate predators and they graze heavily on algae, bacteria, protozoa, and other invertebrates. Zooplankton communities are typically diverse (>20 species) and occur in almost all lakes and ponds. Zooplankton are rarely important in rivers and streams because they cannot

maintain positive net growth rates in the face of downstream losses.

  • zooplankton are small floating or weakly swimming organisms.

  • animal origin that drift with water currents for their movement.

    • Very important as primary consumers.

    • Important food base for secondary consumers, including fish.



Major groups of freshwater zooplankton

Rotifers

1.The rotifers (Rotifera, commonly called wheel animals).

2. Most rotifers are around 0.1 - 0.5 mm long (although their size can range from 50 μm to over two millimeters).

3. Rotifers are an important part of the freshwater zooplankton, being a major food source.

4.Filter-feeding with corona.

5.Mostly littoral, sessile, but some are completely planktonic.

Rotifers as food for fish

1.Too small to be important as food for most fish.

2.May be important in diets of some larval fish.

Cladocerans

1.Small crustaceans (0.2-3.0 mm) with head, and body. covered by bivalve carapace.

2.Swim by using large 2nd antennae

3.Size of phytoplankton ingested proportional to body size.

4.Rate of filter feeding increases with size and temperature.

5.Filter phytoplankton, detritus for food (some are predators).

6.Selective filtering by cladocerans can remove big "chunks" of the phytoplankton, and alter phytoplankton succession.

Rotifer

Cladocerans as food for Fish

1. Large species favored by many fish (visual and filter-feeders).

2. More energy return from bigger species.

3. Eliminates large forms, small ones flourish (big forms often predatory).

Fish Species

Copepods

1. Microcrustaceans in same size range as Cladocerans.

2. Several different groups based on differences in body structure.

3. 2 major groups: cyclopoids and calanoids.

Copepod



Proximate composition of zooplankton

The proximate composition of mixed zooplankton.

As percentage of dry weight are:

  • Protein range from - 40.27 to 63.24%

  • Chorbohydrate range from - 1.68 to 4.55%

  • Carbon range from - 21.34 to 35.17%

  • Lipid range from - 16.23 to32.09%

Role in aquaculture

  1. Zooplankton are preferred natural food for larval stage of fish and prawn.

  1. The rotifer Brachionus species can be mass cultivated in large quantities and is an important live feed in aquaculture.

  2. Live usual as dried Cladocerans for excellent food for the aquarium fishes or ornamental fishes.

  3. Aquatic organisms in the ecosystem depends on the area and volume of the water body and the level of plankton primary production.

5. Improve growth and survival rate of Heterobranchus longisfilis larval when fed on enriched zooplankton, compared to un-enriched.

6. Balance diet for fish and prawn.

7. Rotifers and Cladocerans are important component of most freshwater communities.

8. The population of zooplankton is a function of availability of suitable food for aquatic organisms.

9. The importance of long chain omega-3 Polyunsaturated fatty acids in rotifers as food for Sea bream larvae.

ENVIRONMENTAL FACTORS


Zooplankton are susceptible to variations in a wide number of environmental factors including water temperature, light, chemistry (particularly pH, oxygen, salinity, toxic contaminants), food availability (algae, bacteria), and predation by fish and invertebrates. It is generally desirable to have as much information on these variables as possible. Clearly, this will frequently be practical. Some variables are relatively easy to measure (e.g. temperature), but others are more difficult (e.g. fish-predation intensity, toxic contaminants). Many environmental factors affect zooplankton only at extreme levels (e.g. toxic contaminants, salinity, oxygen) and will not be important in all lakes. Ideally, most sample collections should be accompanied by measures of water temperature, pH, and algal biomass (chlorophyll-a concentration or phytoplankton biomass). Temperature and pH can be measured using portable field instruments whereas the estimation of phytoplankton biomass requires more involved techniques (see Findlay and Kling, EMAN protocols for phytoplankton).

Seafood - Fish - Crustacea

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