Invasive fish species pose threat to native population in Batim lake

Panaji: A major presence of Mozambique tilapia and African catfish in the freshwater catch during the annual fish harvesting at Batim lake raised concerns about the growing dominance of invasive fish species, as populations of native ones are showing a sharp decline.


The fish catch on Tuesday morning at Batim lake, renowned as a scenic birding hotspot, itself showed a downward tick. A few keri, inzull and other species were netted by the fishermen but pintoll, tigur and valloi were missing in the catch.


African catfish (Clarias gariepinus) and Mozambique tilapia (Oreochromis mossambicus) have been posing a threat to native fish and their habitat. Tilapia was introduced for aquaculture in closed systems. But their populations have grown alarmingly as they escaped into other open small and major water bodies in most parts of Goa.


“The catch this year and over the past few years has reduced quite a bit. We don’t find much of our local species such as tigur, ainsollam, ghuri and other fish,” Agnelo Correia, a farmer said.


Correia, who had obtained fishing rights through auction for this season, said various factors could be responsible for the decline.


The fishing on Tuesday was carried out in only a small area of the pond in the dried-up lake. Spreading the nets to the entire pond could yield a more varied catch, including native ones.


Overall, experts make a case for assessment of the growing dominance of invasive species and decline in native fish populations.


Sreekanth G B, senior scientist at ICAR-CCARI, Old Goa, said, “We need to develop a management framework for the control of the invasive fish species, though complete eradication is a daunting task.”


The scientist, who has been studying invasive fish species management, said that awareness and a precautionary approach could be adopted to reduce the pathways of invasion in future. “Invasive fish compete for food and space and also prey on the native fish populations,” Sreekanth added, referring to the two species found in Batim lake.
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