New study finds significant ecological degradation in the Veli-Akkulam lake

The study reveals a stark decline in the biomass of species such as prawns, cichlids. Experts call for urgent ecosystem-based management and eco-restoration to conserve the lake, with special focus on managing invasive species.

Published - September 12, 2024 09:57 pm IST - THIRUVANANTHAPURAM

The Veli-Akkulam lake.

The Veli-Akkulam lake. | Photo Credit: Special arrangement

A new study has revealed significant ecological degradation in the Veli-Akkulam lake, primarily driven by bioinvasion.

The study led by researchers of the University of Kerala and presented at the International Conference on Coastal Resilience (ECSA 60) in Hangzhou, China, highlighted dramatic shifts in the lake’s trophic status and food web over the past three decades.

The research, which employed the Ecopath Model to assess ecological efficiency and food web structure, revealed a decline in the Veli-Akkulam lake’s indigenous aquatic species and an increase in invasive species.

C.M. Aravindan of the University of Kerala first mapped the ecosystem in the 1990s, revealing a rich presence of native species such as prawns, indigenous cichlids, barbs, and catfishes.

However, the current study reveals a stark decline in the biomass of these species. For instance, the biomass of prawns dropped from 57.60 tonnes per sq km to a mere 0.110 t/sq. km, while indigenous cichlids have diminished from 41.6 tonnes per sq km to 0.350 tonnes. The study was carried out by A. Biju Kumar, S.R. Regi, and Smrithy Raj of the Department of Aquatic Biology and Fisheries, University of Kerala, and G.B. Sreekanth of

ICAR-Central Coastal Agricultural Research Institute, Goa. The research was supported by the University of Kerala and the Ecomarine Project of the European Union.

Invasive species

It found that by the 2000s, the native species were replaced by the exotic and invasive Mozambique tilapia (Oreochromis mossambicus), which has now been overtaken by the Nile tilapia (Oreochromis niloticus). Further complicating the ecosystem are other invasive species like the Amazon African catfish (Clarias gariepinus) and Amazon sailfin catfish (Pterygoplichthys pardalis).

Nile tilapia (Oreochromis niloticus) caught from the lake.

Nile tilapia (Oreochromis niloticus) caught from the lake. | Photo Credit: Special arrangement

Professor Biju Kumar, the lead researcher, described this phenomenon as “invasion meltdown,” where multiple non-native species not only establish themselves but also exacerbate the impacts on native life forms. In addition to invasive fish species, water hyacinth, an invasive plant, was also found in the lake system, as per the study.

Impact on livelihood

Beyond ecological impacts, this shift has severely affected the livelihoods of local fishers, according to the researchers. The number of fishers dependent on the lake has slipped rom over 100 in the early 1990s to fewer than 20 today, they found.

They have recommended urgent ecosystem-based management and eco-restoration to conserve the lake, with special focus on managing invasive species. Ranching the lake with indigenous species that have high ecological conversion efficiency, such as benthic molluscs, cichlids, mullets, and native crustaceans, could help to restore balance to this ecosystem, they said.

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