It has also snagged a spot on the International Union for Conservation of Nature's 100 of the world's worst invasive alien species and emerged as one of the biggest threats to the indigenous snow trout and 150 other native fish species found in the Himalayan waters. "This particular breed inhabits cold waters, but rising temperatures are pushing native fish species northwards, leading to a conflict with the brown trout. It is a conflict that the brown trout will dominate," says Arjun Singh, who has been working towards the conservation of the snow trout in the Kashmir region for over a decade.

Climate change gives them a further edge and compounds their impact. Apart from warmer temperatures, climate change has also resulted in more extreme weather events, such as droughts, floods, cyclones and faster-rising sea levels. Warmer waters will allow existing non-native species such as the common carp, Nile tilapia and African catfish to move into new areas. Changing conditions can also make water bodies less suitable for some native species. This year's first-ever census of Kerala's Ashtamudi lake found that 85 percent of the 51 species present in the lake are marine varieties.

Researchers attribute the reason to a decline in freshwater flow from the Kallada river due to climate change. That apart, changes in the course of rivers can lead to the introduction and increase in invasive species. "Sudden floods can trigger the production of fish at the wrong time. Some species can become stressed due to environmental changes, resulting in weaker immune systems and lower reproductive success, while others flourish and become competitive. An increase in water temperature can also result in a change in sex ratios, causing alterations in the time of spawning and migration," says Vidya Karnik, an independent biologist, who has spent a decade studying the Kaveri river.

Winner takes all In our country, the Zoological Survey of India lists 157 animal species as invasive. It includes 99 marine species and 19 species of freshwater fish. To become a successful invader, according to the Convention on Biological Diversity, an alien species must tick several boxes. A survey after the 2018 floods in Kerala found 30 alien fish species in its 44 rivers and 53 reservoirs. In two years, it had increased to about 3.5 per cent of the total fish species. Today, it is among the dominant species in several parts of the river. The know-how To counter these challenges, we must have a better understanding of how climate change affects invasive species. The life cycle of alien species and the impact of climate change on them is rarely monitored.

Source : MoneyControl