GUWAHATI, Oct 10 - Wetlands of Assam that act as natural fisheries are undergoing rapid degradation in the face of anthropogenic pressure and climatic change. This is leading to decline in the fish production which in turn is impacting mass livelihood.
A study conducted by ICAR-Central Inland Fisheries Research Institute through its Guwahati Regional Centre on the vulnerability of beels of the State found that the degradation was affecting spawning and reproductive behaviour of fishes.
The study, conducted in the beels of Dhubri district during 2018-19, was done under a research project �Impact of climate change in inland fisheries and development of adaptation strategies� by a team comprising Dr BK Bhattacharjya, BK Das, UK Sarkar, D Debnath and Sona Yengkokpam.
�The study focused on vulnerability of beels, their users and the fishes in them. It showed that due to natural factors like climate change, siltation and encroachment, Sara Beel was converted into a seasonally open beel from a perennially open one. This beel had a connection with the Gaurang river 20 years ago,� Dr BK Bhattacharjya, principal scientist and head (acting) at ICAR-CIFRI Guwahati Regional Centre, told The Assam Tribune.
The study revealed that over the past 30 years, about 70 per cent of the beels experienced reduction in water-spread area. High level of siltation, encroachment, detachment of marginal areas due to construction of roads, etc., caused reduction in the water-spread area from the original area, mostly in the dry season.
�As a result, spawning and reproductive behaviour of the Indian major carps have been impacted. Flood in Assam during the rainy season is as severe a problem for the fisheries sector as waterless-ness during the dry season, which makes a wetland all the more vulnerable. As per information available, most of beels of Assam experienced major flood in 1988, 2014, 2017 and 2019,� he said.
To cope with the impact of climate change and for promoting sustainable wetland fisheries, various adaptation strategies were identified by the scientists. These are temporary pre-summer enclosures, deep-pool refuge, autumn stocking, submerged branch pile refuge, and floating aquatic macrophyte refuge (jeng/katal).
�Enclosure aquaculture in the form of pens and cages can not only prevent fish from escaping during flood, these structures can be shifted to deeper areas of the wetlands in case of reduced water depth during the dry season, making these technologies climate-resilient. Enclosure culture technologies are simple but useful tools for producing stocking material (advanced fingerlings) and table fish that potentially can improve socio-economic condition of beel fishers,� he said.
According to Bhattacharjya, introduction of exotic fishes in natural water bodies from nearby ponds and culture fisheries could take place due to natural disasters like flood, which potentially can affect icthyofaunal biodiversity in those water bodies.
�Majority of the beels of Assam reported exotic fishes like Cyprinus carpio (common carp), Ctenopharyngodon idella (grass carp), Hypophthalmichthys molitrix (silver carp), Hypophthalmichthys nobilis (bighead carp) and Piaractus brachypomus (pacu). Surprisingly, Pacu, a highly invasive species locally known as �Rupchanda�, was reported in a few beels (like Hakama beel) that threatened small indigenous fishes of that wetland,� he said.
Worryingly, there has been a decrease in fish catch per person per day in a majority of the beels as compared to the past 30 years.
�With increase in population, the number of fishermen has also increased causing reduced catch per capita. But the phenomenon could also be attributable to the degrading nature of the fish habitats in terms of reduced water-spread area, pollution, loss of riverine connection, etc., and reduced number of fish species in the beels studied,� he said.
According to the study, fishermen themselves have to share some of the blame for the present sorry state of affairs of the beels, �because the code of conduct for responsible fisheries (such as fishing ban, gear restriction, maximum sustainable yield with minimum fishing efforts, etc.) applicable to sustainable utilisation of inland fisheries are mostly violated by the users themselves.�
Studies have also shown that beels of Assam are heavily weed-infested (with floating macrophytes) that pose serious problems for fisheries including difficulty in fishing. Further, catch of wild fish stocks from the beels has got reduced over the years because of poor riverine recruitment, over-fishing and siltation.
�Certain indigenous fish species like Ompok pabda and Puntius sarana were becoming rare apparently because of loss of riverine connection with the beels. Water quality deterioration and occasional disease occurrence are also reported from beels,� Bhattacharjya said.
According to a survey, majority of the beel fishers felt that there was (i) change in precipitation patterns in different seasons, (ii) prolonged dry spells during the pre-monsoon and monsoon seasons, (iii) accelerated siltation of the wetlands and (iv) decline in abundance of major/big-sized indigenous fish species like Channa marulius, Chitala chitala, Sperata aor, S seenghala, etc.
Man-made factors (improper sluice gates, laying of railway tracts, brick factories) pose serious problems of water availability/retention leading to prolonged dryness in some of the beels (e.g., Dhir Beel). Commercially important and high-value wild fish stocks such as C. chitala, W attu and M. cuchia became non-existent due to decrease in water depth and weed infestation/decomposition. Use of fine mesh (mosquito net, monofilament) nets is noticed in Dhir Beel leading to overfishing subsequently decline in SIFs, the study found.
