Imphal Review of Arts and Politics

Dept of Environment and Climate Change
Survival of indigenous fishes can be put in jeopardy if exotic invasive species of fishes are introduced in the state injudiciously

Understanding the Potential Negative Impacts of Alien Fish Species in Aquatic Ecosystem Will Help Revive Indigenous Fishes of Manipur

“Losing the indigenous fishes of our state, Manipur is same as losing our near and dear ones”, lamented by Langpoklakpam Kamal Singh of Khundrakpam Makha Leikai. The 79 years old Kamal narrated that during their childhood many indigenous fishes like Ngahou, Ngatin, Tharak, Pengba, Ngaton, Porom, Ngasep, Ngamu, Ngakha Mitngangbi etc. were abundantly available in rivers, ponds and lakes. He opined that with the introducing of insecticides, pesticides and weedicides etc. during the 1960s in the paddy fields in the state marked one of the important reasons for the declining of the indigenous fish and being dominated by alien fish species in the water bodies. Those fishes were very tasty. During their times, they used to preserve these fishes in earthern pots for future consumption. He felt very sad just remembering all those memories of catching fishes and enjoying the taste which will never come again.

Globally, invasive alien species have been considered as a grave threat to the biodiversity and ecosystem. Alien species are organisms that are not indigenous or native to a particular area. Invasive species are a subset of alien species that have the ability to rapidly spread and establish themselves in new environment, often causing harm to native ecosystem, species or human interests. Many studies in the past have confirmed that the invasive species also have the potential to significantly alter the regional and global climate. Alien fishes can have significant impact on river ecosystems. They often overcome native species for resource, alter habitat structure and disrupt food webs. This can lead to declines in native fish populations and even ecosystem-wide effects such as decreased water quality and altered nutrient cycling. According to National Biodiversity Authority (2019) fourteen fish species have been identified as inland invasive alien species of fishes. As to mention a few species are Clarias gariepinus (African catfish – Moreh Ngakra), Cyprinus carpio (Common carp – Pukloubi), Oreochromis mossambicus (Mozambique tilapia – Tunghanbi), Oreochromis niloticus (Nile tilapia – Tunghanbi), Aristichthys nobilis (Bighead), Pterygoplichthys multiradiatus (Sucker mouth armored cat fish) etc. Some of these species are found in the water bodies of Manipur. And there has been an increasing demand for alien fish species in Manipur.

Interacting with a farmer named, Toijam Megha Luwang from Nambol Kongkham, Bishnupur district who has been rearing fish for more than 15 years expressed that there is high demand of Vietnam Koi (Ukabi) in the local market presently. In his fish farm he is rearing Paku, Tunghanbi, Puklaobi, Grass carp, Silver carp etc. All these fish species have high profit within a short period time. He opined that farmers have now starting cross breeding with the native and other alien fishes using modern technology. Moreover, these fishes are tasty and of high demand by the people of the state. On the other hand, he also started his project of rearing indigenous fishes of the state in a separate pond with a hope to produce more local fish in the market.

Another fish farmer Thoudam Manbi Devi of Wangoi Makha Leikai who has been selling fishes at Khwairamband Nupi Keithel for the last 15 years says that many people have come in search of indigenous fishes such as Nganap, Meitei Ngamu, and Ngakijou etc. Almost all the indigenous fishes of the state are at the verge of extinction. This is very unfortunate. Those childhood days where she enjoyed the taste of indigenous fishes will not come back again, Manbi lamented. Even though, she wants to sell such fishes, it is not possible as the fish farmers rear mainly like Tunghanbi, Rou, Common carp, Silver carp, Paku and Koi etc. She has been selling these alien fishes for the last many years. In all the lukmai (tray) of Khwairamband Nupi Keithel and other local markets, people will hardly find indigenous fishes, she added.

In this regard, Dr Chanamthabam Basudha Devi, Principal Scientist (Fish and Fishery Science), ICAR Research Centre for NEH Region, Manipur Centre, Lamphelpat, Imphal expressed that as a part of blue revolution many fishes were introduced in the state in late 1960s. With the introduction of exotic fish in the river, it gradually becomes invasive commonly the Common carp and Tilapia, Grass carp in some location but not in the rivers. There is rapid growth of population of Grass carp in Loktak Lake. Even local aquatic edible plants are also losing day by day because of these alien fishes.

Moreover, climate change, water pollution, siltation, construction of infrastructure and deforestation are the major contributing factor for the loss of indigenous fishes of Manipur. As the alien fish can adapt easily at any environment, grow and reproduce quickly and spread aggressively, they dominate the indigenous species in term of space and food which lead to the loss of many indigenous fishes. As Manipur is a biodiversity hot spot area it is necessary to investigate any fish species before introduction into the water bodies in order to preserve the indigenous fish. During the floods the invasive fishes escape from the ponds to the rivers which are a major threat for disappearing of indigenous fish which flourished in the rivers. In the last 10-20 years the population of fish in the rivers has drastically decreased. As the river water becomes lentic from lotic, the fish that lived in the lotic ecosystem disappeared, she added. Dr Basudha expressed her desire to establish a recognized independent body to monitor, regulate, research and implement measures of alien fish species in the water bodies of Manipur to preserve the indigenous fishes.

To preserve the indigenous fish of the state, Department of Fisheries, Government of Manipur has taken up some steps. The department started its activities to increase the population of Ngakijou and Nganap using scientific techniques. For Pengba and Ngaton, the experimental works are successful. Seeds of Pengba and Ngaton are now made available. The seeds can be available at the subsidized rate for the farmers. It is reported that Crocodile fish (invasive) was found in the rivers being escaped from the aquarium. It is a banned species now. Thai Magur which is carnivorous is also banned in the state. There are also other banned fish species in the state. But the farmers still continue to rear this banned fish species considering its profit. The department has also taken an initiative to preserve the native ornamental fishes of the state.

Managing alien fish population is crucial to preserve the health and biodiversity of rivers. Overall, the presence of alien fishes in rivers underscores the importance of proactive management strategies such as monitoring, control measures, and public education to mitigate their impacts and protect native ecosystem. Thus, understanding the potential negative impacts of alien fish species in the water bodies will help in reviving the indigenous fishes of Manipur.

(The article is filed under the 4th State Level Media Fellowship Programme on Climate Change under the sponsorship of the Directorate of Environment and Climate Change, Government of Manipur).

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