Tracking the fishes of Brahmaptura

This study on the Brahmaputra revealed the presence of 222 species of fishes belonging to 105 genera under 37 families and 12 orders, comprising as much as 75 per cent of the 296 species reported from India’s northeastern region, and 25.31 per cent of approximately 877 freshwater fish species across India. The Brahmaputra drainage system boasts an impressive range of ichthyo-faunistic (fish fauna) resources or geographical terrains suited to a wide variety of fishes, with a combination of torrential (hill stream) and plain water species as well as cold and warm water species. The majority of the species belong to the order Cypriniformes(114 species), followed by Siluriformes (57 species) and Perciformis (29 species). Among the families, Cyprinids were found to be the most dominant group with 80 species followed by Balionidae(17 species), Cobitidae and Bagridae with 13 species each and Channidae with nine species. Of the 222 fish species found in the state, around 210 species are reported to have food value. During the study, only 50 species were found to have considerable commercial importance as food fish. In addition, 24 species have importance as game or sport fish, and around 150 species have potential ornamental value. Of the total fish species, 40 are found to be endemic to the state, that is, they are found only in Assam. Recent reports on catch statistics indicate that there has been a drastic reduction in the abundance of fishes accompanied by changes in the distribution range of several fishes due to habitat modification, overexploitation and other anthropogenic causes. As far as the current conservation status of the recorded fish species is concerned, it has come to light that one third of the species, i.e., 41 species, are Vulnerable; 40 species are at Lower Risk-near threatened; 22 are Endangered, and one specie is Critically Endangered. About nine species fall within the category of Lower Risk--least concern. The majority of the species (93), a large proportion, have not yet been evaluated (Not Evaluated). Alien fish species such as Hypophthalmichthys molitrix, Ctenopharyngodon idella, Cyprinus carpio, Clariasgariepinus, and Oreochromis mossambicus have been identified in the present study because of their occurrence in the natural water bodies of the Brahmaputra drainage system.

A range of habitats

Depending upon their unique topography five types of fish habitats have been identified in the Brahmaputra: fast flowing rivers, sluggish pools, confluences, river meanders, and flood plain wetlands or beels. The fact that pools and meanders are comparatively richer in fish biomass than rapids and open rivers indicates that faster currents have an adverse impact on fish biomass. There is greater fish biomass in clear rather than in turbid water. Again, depending on the availability of species around the year, the fishes of Brahmaputra can be divided into four different categories: those found throughout the year; pre-monsoon and monsoon; post-monsoon; and winter and dry season when the water level is at its minimum. Apart from the fish species, the Brahmaputra is home to nine species of freshwater prawn. The river’s flood plains also possess a total of 76 species of macrophytes or aquatic plants belonging to 36 families and 55 genera. Poaceae is the dominant family with seven species, followed by Polygonaceae, Nympheaceae, Lemnaceae and Hydrocharitaceae. The study showed that there are more monocot species than dicots and pterydophytes. Ecologically, five types of growth forms are found among the macrophytes: anchored floating leaf (5.26 per cent), obligatory submerged (15.79 per cent), free floating (11.84 per cent), anchored floating stem (25 per cent), and emergent plant (42.10 per cent).

Bustling fish landing centres

The Brahmaputra has as many as 42 fish landing sites on both banks of the Brahmaputra, their names echoing the undulating cadence of the river. Among them Dholaghat, Guijan ghat, Dehing Mukh (Dibrugarh), Disangmukh, Kokilamukh, Nimati ghat, Biswanath ghat, Jogighopa, Dhekiajuli, Tezpur, Uzan bazaar (Guwahati), Chunari ghat, Cehunari kamakhyabari, Tulsibari, Joleswar ghat (Goalpara), Dhubri ghat and Bura buri are the major fish landing centres. The monthly fish yield of the main fish landing centres showed a higher catch in the main river in post-monsoon months. The winter and pre-monsoon months were more favourable as fishing seasons in wetlands. There are 216 fishery cooperatives in the state with 43,394 members. It was observed that they are somewhat lax in following the rules and regulations governing fisheries even though their livelihoods depend on it. There are significant regulations pertaining to the use of the small-meshed mosquito net for fishing, the months of observing a closure of fishing activity, and catching broods and juveniles.

From brood banks to ethno-medicine based on fish varieties

The Brahmaputra’s considerable contribution towards hill fishery has been accelerated by the establishment of the first ever hatchery and brood bank of the Golden Mahseer courtesy an intiative of Assam (Bhoreli) Angling and Conservation Association (ABACA), an NGO established in the early 1950s for the conservation of the Golden Mahseer in particular. A total of12major angling spots have been identified, which is bound to increase the tourism potential of the state. Depending upon the availability of water, depth, and type of water body, the size and type of the species to be caught as well as the number of individuals involved in fishing, four different types of fishing gears are used by the fisher folk operating in the Brahmaputra basin -- nets, traps, hooks and lines, and unconventional methods. The fishing nets are mostly of the fixed and moving type, and a total of 37major fishing gears and 27 herbal drugs as piscicides were observed to be in use. The study has brought to light yet another fascinating fact, namely that indigenous healing systems have16 different treatments based on the medicinal properties found in 12 fish varieties, and the dolphin.

Bank erosion threatens fish life

Frequent changes in the course of channels and bank erosion with a high rate of siltation have been identified as major threats to the riverine biota (total aquatic organisms ) of the Brahmaputra as they have a great bearing on the faunal composition of the river. Heavy siltation not only raises the river bed but also blocks the mouth of the channels connecting the beels. This prevents the riverine fish from entering the wetland through the channels. Since there is no auto-stocking of fish and auto-removal of floating macrophytes during the monsoon months, it results in the extermination of wetland species. A sharp decline in the catch of the Indian Major Carps points to the loss of spawning grounds in the Brahmaputra and most of its major tributaries. The construction of embankments and dams upstream also contributes to this phenomenon. Further, deforestation in the Brahmaputra catchment indirectly accelerates siltation, which has an adverse impact on freshwater biota. The indiscriminate killing of fish by using pesticides and other illegal devices is another major threat to the already depleted fishery resources of the river as well as the floodplain lakes associated with it. Over-exploitation of resources, mainly fish from the wetlands, coupled with the conversion of the low-lying land of the beels for agricultural purposes have already threatened wetland habitats. Equally, the conversion of wetland habitats for human settlements, road construction, direct deforestation in wetlands, unsustainable levels of grazing, and fishing activities such as dredge disposal have a considerable economic and ecological cost. Finally, the use of machine boats for transportation also contributes the depletion of aqua resources to some extent.

 


Recommendations of the study

From the detailed study it is possible to suggest some measures  for the conservation of the aqua resources of the Brahmaputra:There should be efforts to create awareness about the importance of aqua faunal diversity and their proper utilisation among the fishing communities.

 

  • Checklists of the Brahmaputra’s aqua fauna should be regularly updated in order to facilitate the formulation and proper implementation of sustainable development programmes.
  • Ecological models of the river through the application of eco-hydrological tools based on Eco-4resources like plantation should be created to restore the river’s aquatic habitats and build a strong database on floods.
  • Advanced tools like remote sensing and GIS should be used to create appropriate models to predict and assess the prized fish stock from an economic and conservation point of view.
  • New opportunities should be created to divert fishing communities towards culture fishery, especially cage culture in the river, so as to decrease the stress on the wild stock.
  • Training should be provided for the rejuvenation of Brahmaputra’s endangered fish species like Tor sp. (species of Mahseer) in the river which have a high value as food and sport fish.
  • Breeding units should be installed in select places for the rejuvenation of species at risk.
  • There should be strict monitoring to check unauthorised and illegal collection and violation of fisheries laws.
  • Stretches of the Brahmaputra in the main fishing zones should be identified for effective restoration measures.
  • A roadmap should be prepared for the development of the Brahmaputra in general and its aquatic culture in particular in the interests of livelihood security. Policy makers need to consult with  fisheries scientists, policy makers, government agencies,  biologists,  environmentalists, fish farmers, fisheries cooperatives, financial institutions, NGOs and other stakeholders to bring about conditions for livelihood security in rural Assam in the true sense.

 

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