Wetland Ecosystem And Fisheries

^@Harshavardhan D. Joshi, ^#Dr.ATR, ^#Milind B. Katare, ^@K.K. Ramteke and ^*M. P. Bhendarkar

^@Central Institute of Fisheries Education, Seven Bunglows, Versova, Andheri (w.),

Mumbai-400061, Maharashtra, India

^#KAFSU, College of Fisheries, Manglore, Karnataka, India

^*BSKKV, College of Fisheries, Ratanagiri, Maharashtra, India

Wetlands are one of the most productive ecosystems comparable to tropical evergreen forests in the biosphere and play a significant role in the ecological sustainability of a region. Wetlands form the transitional zone between land and water, where saturation with water is the dominant factor determining the nature of soil and the types of plant and animals community's living in and on it. An immense variety of species of micro-organism, plants, insects, amphibians, reptiles, birds, fish and mammals are the part of a wetland ecosystem.

Wetlands provide great volumes of food that attract many animal species. These animals use wetlands for part of or all of their lifecycle. Dead plants leaves and stems break down in the water to form small particles of organic material called "detritus". This enriched material is fed on by many small aquatic insects, shellfish and small fish that are food for larger predatory fish, reptiles, amphibians, birds and mammals. These zones would nowadays be classed as ecotones.

According to Ramser Convention, the area of marsh, fen, peatland or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt, including areas of marine water the depth of which at low tide does not exceed 6 meters are considered as wetland system. Also consisting of peat bogs like Ombrotrophic bogs, Soligenous bog and Maeshlands like Marshes, Fens, Swamps, floodplains etc.

WETLANDS FOR FISHERIES:

Wetland is an ecosystem which provides great volume of food that attracts many animal species like shellfishes, small fishes and predatory fishes. Capture and culture fisheries activities can be effectively carried out in these type of water logged areas provided the system is well managed.

1. CAPTURE FISHERIES:

Wetland naturally has its own biota where the capture fisheries can be planned provided it is sufficiently deep enough. Carrying out the fishing activities, capture fisheries is nothing but harvesting the natural habitats from water by means of various verities of gears such as cast net, gill net, traditional and advanced traps, trawl gears, seiens etc. Further, land which is suitable for recreation, mainly angling, sport fishing, and also tourism spot act as fishing ground. We can develop ornamental capture fisheries with respect to colorful fishes and ornamental plants.

The major problem during operation of nets in wetlands area is vegetation. Most of the time operations fail or various operational problems occur like damage of net, arresting of net in vegetation. Most aquatic vegetation problems are the result of elevated levels of nutrients, primarily nitrogen and phosphorous, in the pond/lake's water and sediments. These nutrients are always present in some amounts and naturally build up over time.

In the floodplains area, the gill net near the periphery of the wetland area can be used. Pit or pond like structure near floodplains area in which fish get entrapped during heavy rain-fall. Bamboo traps and advance mechanized traps in this area can also be used for effective capturing of the fishes. In the Marshes, fens and swamps, the traps play a vary important role and these traps can easily be removed with fish when placed in vary dense vegetative areas.

The creeping habit of prawn and crabs at the bottom in the shore regions, especially at night, are mostly caught by traps set in those areas. In the deeper areas of the wetlands, mostly gill nets are operated. In the shallow water which has less vegetation, mostly cast nets are operated.

CULTURE FISHERIES:

Aquaculture can be possible in the wetland area but before that the eradication of aquatic weeds is pre-requisite. There are various methods which are used for the eradication of aquatic weed; they are Mechanical method, Chemical Method and Biological Method.

a) Mechanical Method:

The mechanical method for controlling aquatic weeds are very important but followed on a limited scale.

There are various types of cutters or mechanical equipment which are used to eradicate aquatic weeds and fens and they are Water weed cutters and Weed harvesters.

Because it is not only slow and expensive but also requires manuel labor to complete the follow up operations, the use of mechanical controls is usually only feasible for smaller sized wetland areas or for spot treatments of smaller areas in larger wetland bodies. Various methods include cutting or pulling out the vegetation, raking and/or seining floating vegetation blown into corners by the wind or wave action.

b) Chemical Control Methods:

Some chemicals popularly known as herbicides can effectively control the noxious aquatic weeds. A large number of chemicals have been used as herbicides for the control and they are of six groups namely:

i) Inorganic chemicals: ( Sodium arsenite)

ii) Organic chemicals: ( xylene)

iii) Auxin type regulator: ( 2-4 Dichlorophenoxyacetate)

iv) Contact herbicides: P.C.P.

v) Algaecides: ( Resinamin Dacetate)

vi) Other growth regulators

c) Biological Control of Aquatic Weeds

In the biological control, a suitable organism is introduced. The organism either feeds upon the aquatic weeds or otherwise damages it severely and keeps it under check and spread to acceptable limits.The organism used to check the spread of weeds is called bio control agent or a bioagent which may be specific or non specific.

The method of biological control of aquatic macrophytes has many advantages over chemical control method. It is convenient, cheap, free from pollution hazards and the fertility of the pond is not altered.

Some examples of bio agents mainly herbivorous fishes are Grass carp (Ctenopharyngodon idella), Puntius javanicus, Common carp (Cyprinus carpio), Tilapia spp., Silver carp (Hypophthlmichthys molitrix), Gourami(Osphronemus gourami).

Other Animals as Bio agents are Manatee(Sea cow), Ducks & Geese, Aquatic Rats, Insects (like Water hyacinth weevil, Water hyacinth moth, Water hyacinth mite) and Fresh water snails(Marisa cornllarieties & Pomacea australis). In India Pillia globosa is used for eradication of Salvinia molesta.

2. CULTURE FISHERIES:

We can develop the aquaculture in the wetland area, and altering and eradication of aquatic weeds from the desirable depth of wetland area thereby forcefully the aquaculture activities could be performed.

PEN CULTURE:

A Pen is defined as "a fixed enclosure in which the bottom is the bed of the water body". The word 'pen' here is also used synonymous with 'enclosure' as it is used in enclosure culture.

Pen culture is a very important culture technique in the wetland area since the wetland itself is a nutrient rich body. High primary production, mostly found in wetland areas, and hence they are famous for the food due to which it attracts various fishes towards it. Particular area could be restricted with the help of net and eradicate all vegetation with the help of mechanical, chemical or biological methods and this water platform becomes a locked area for aquaculture and thus it serves as pen culture.

Rearing of young stages of fin and shellfish in wetland pens represents a new and relatively simple approach with potential to become an important seed raising systems in near future for profitable resources utilization.

Species with potential for rearing pens are Indian and Chinese carp, eels, catfishes, milkfishes, mullets, tilapia and both fresh water and brackish water prawns.

PEN CULTURE

CAGE CULTURE:

Cage culture may also be possible in wetland areas provided the depth is sufficient to mount cages. However, removal of aquatic vegetation is the prime duty before planning of cage culture practice. Cages are made with a rigid bottom, the frame of the bottom pushes vegetation of the wetland area and makes available water inside the cage and this water can used for the aquaculture.

Purpose of cage culture is to rear spawn and fry to fingerling size within 2 to 3 months. High density rearing is restorted to in this phase, with intensive high protein feeding. Due to availability of natural food and by also providing supplementry feed results in faster growth rate of the fishes. It is possible to rear Rohu, Catla, Mrigal, silver carp grass carp and common carp fry or spawn in fresh water wetland cage culture system.

Production of carp seed in wetland cages through appropriate technology reduces pressure on land for fish nurseries.

Construction of Pond near by the wetland area

In the floodplain or in the lagoon side area the ponds automatically fed by water due to increase and decrease of water level. Pumping to fulfill the water demand of the pond can be the another option.

Construction of Pond near by the wetland area

RAFT AND STAKE CULTURE:

There is also scope for the raft and stake culture in the wetland area.Clams, Oyster etc. production from this type of aquaculture is possible.

RAFT AND STAKE CULTURE

INTEGRATED FARMING:

 The wetland area which is generally waste land can be used as integrated fish farming with Makhana culture. This type of mixed culture will offer greater efficiency in resource utilization, will reduce risk by diversifying crops and will provide additional food and income. This system will be of special significance as it will improve the socio-economic status of weaker rural fisher community.