By Salam Rajesh
Invasive Alien Species of plants and animals often are considered as threat to native species of plants and animals that are of food, medicinal, socio-religious and commercial values in any given society that consider certain types of plants and animals as intricately relevant to their lives and economies.
In general classification, Invasive Alien Species of plants and animals are those plants and animals that were introduced either intentionally or unintentionally into a given landscape or ecosystem from other outside sources. For instance, Tilapia fish (Tunghanbi) is originally from East Africa and was introduced in India in 1952.
Like in most countries around the world, water bodies in Manipur – lake, marshes, rivers, paddies and ponds – are more or less dominated by introduced fish species such as Asian carps, some of which have since become invasive by nature.
Chennai-based National Biodiversity Authority (NBA) of India had in February 2022 released lists of Invasive Alien Species (IAS) of plants and animals in the country that needed priority attention for their control and management to prevent local biodiversity loss and species decline.
Not surprisingly, many of those listed IAS are abundantly found in the Manipur central floodplains and in the uplands, quite common enough for people to neglect them just as any other local species they see in their mundane lives.
Figuring on the top of the NBA list for IAS plants, Manipur has plenty of aquatic and semi-aquatic plants like water hyacinth, water lettuce, alligator weed and paragrass to ponder on what to do with these ‘nuisance’ plants, so much so as the NBA had suggested for the complete removal of these IAS plants manually country-wide by the target year 2030.
Similarly, for the IAS fishes as listed by the NBA, Manipur too has Asian carps like Common carp, Silver carp and Grass carp, and Tilapia, where the NBA suggested complete removal country-wide by manual means two significant ‘nuisance’ IAS fishes – Common carp (Cyprinus carpio) and Tilapia (Oreochromis mossambicus).
On deliberating what to do with the NBA’s suggestion for the complete removal of undesired IAS plants and fishes throughout the country, including Manipur, one can reflect on what is happening on this front in the West.
For instance, take this case study from Alaska. Biologists in South-central Alaska carried out a dramatic restoration program where they treated an entire lake with rotenone, a plant-derived piscicide, to wipe out an invasive population of the fish Northern Pike.
After the treatment, post-surveys confirmed that the pike population was gone. The next step was in rebuilding what was lost. In June 2013, the Alaska Department of Fish and Game (ADF&G) stocked 6,836 hatchery-reared Arctic char fingerlings into the now pike-free lake, jump-starting the recovery of a native fishery that had been pushed out by the predator pike. This account drew on the ADF&G’s technical reports and project summaries documenting the rotenone treatment and subsequent restocking with native fish.
In another instance, during December of 2009, the State of Illinois took an extraordinary step to protect the Great Lakes from an invasive fish that had been moving through the waterways of the Mississippi River basin. Officials treated a section of the Chicago Sanitary and Ship Canal with rotenone that kills fish by disrupting their ability to use oxygen.
The Chicago Sanitary and Ship Canal is a man-made connection between the Mississippi River and Great Lakes drainage systems. The canal created an unintended ecological pathway through which invasive aquatic species could move between two historically separate ecosystems.
Asian carp, particularly bighead carp and silver carp, had become a major concern because of their ability to consume large quantities of food and reproduce rapidly. Silver carp were also known for their jumping behavior when disturbed by boats, while bighead carp could grow to large sizes. These invasive fishes were feared to compete with native species and disrupt food webs.
In yet another third instance, during 2006, Yellowstone National Park deliberately treated a mountain lake with rotenone to remove fish that had been introduced there decades earlier. High Lake had been stocked with introduced Yellowstone cutthroat trout although it was in the range of the native Westslope cutthroat trout.
According to research published in Biological Science, the program was not simply a matter of adding a chemical and allowing it to spread downstream. Yellowstone installed a neutralization station below the lake’s outlet waterfall, where potassium permanganate was used to deactivate the rotenone.
The station was monitored round the clock for 22 days, while fish held in cages downstream were used to check that the toxin had been neutralized before treated water continued into East Fork Specimen Creek.
The justification for the program was that the trout in the wider watershed were afffected by their genetics. Fish introduced in the region had mated with Westslope cutthroat trout, and the resulting population did not qualify for conservation populations of Yellowstone. The process of restoration involved removing the non-native or hybridized fish from the region and introducing Westslope cutthroat trout to revive native species.
The International Union for Conservation of Nature and Natural Resources (IUCN) considers Invasive Alien Species as one of the leading drivers of biodiversity loss globally, contributing to species extinctions, ecosystem degradation, and significant economic and social impacts. They threaten food and water security, human and animal health, and undermine efforts to achieve global biodiversity and sustainable development goals.
In response, IUCN is developing a Union-wide Invasive Alien Species Strategy. The strategy will provide an enabling framework to support IUCN Members, Commissions and Secretariat in scaling up efforts to prevent the introduction of invasive species and to reduce their impacts.
The development of the IUCN strategy builds on the mandate established in the IUCN Program, and aligns with global commitments under the Kunming-Montreal Global Biodiversity Framework during 2022, in particular with reference to Target 6 on invasive alien species.
Water hyacinth, an invasive aquatic plant that forms vast monotypic stands that impact human activities, such as traditional capture fishery and water transport amongst others, is considered a domineering nuisance aquatic plant all over the world.
Manipur, too, is not free from the worry created by IAS plants and fishes. The Loktak wetland complex, and similarly in most water bodies across the State, is plagued by the IAS species, of which water hyacinth figures on the top, and can be similarly said of the common carp and the tilapia.
It is indeed high time that the State administration, and other relevant academic and scientific institutions, figures out what to do with these domineering species, so as to preserve the integrity of the State’s biological diversity on the one hand while reviving and restoring native species of food, medicinal, socio-religious and commercial values.
It is not too late to re-think on strategies to confront the Invasive Alien Species, and help restock and re-vitalize the State’s biological diversity.
