Kochi, Sep 29 : The boom-and-bust cycles of Indian Oil sardine, a vital species for Kerala's fisheries and India's marine food basket, are strongly tied to monsoon rainfall and oceanographic changes, according to a new study by the ICAR-Central Marine Fisheries Research Institute (CMFRI).

The findings, published in Current Science, highlight how climate variability is reshaping sardine dynamics and call for the urgent adoption of dynamic forecasting and harvest rules.

Sardines, often called the 'lifeline' of Kerala's fishing communities, have shown dramatic fluctuations over the past decade.

After a record catch of four lakh tonnes in 2012, landings plummeted to just 3,500 tonnes in 2021.

In 2024, however, Kerala witnessed an unusual surge of juvenile sardines averaging just 10 cm in size.

This sudden influx led to ecological stress, including mass beaching in districts such as Kozhikode and Thrissur, and economic turmoil due to a collapse in market prices.

The CMFRI study, which combined fisheries biology with oceanographic data from Kochi, Vizhinjam, and Kozhikode, attributes the 2024 phenomenon to positive monsoon rainfall trends.

Enhanced nutrient-rich upwelling created favourable conditions for microplankton growth ' the key food source for sardine larvae.

This boosted larval survival rates and caused an unprecedented recruitment spike.

However, the abundance of young recruits soon created intense competition for food, resulting in poorly nourished fish with lower weight gain.

"This situation led to severe market impacts, including price crashes and suspension of juvenile fishing," U. Ganga, Principal Scientist and lead author of the study, said.

The researchers found that ecosystem productivity indicators ' particularly the microplankton component of chlorophyll-a ' played a more decisive role in sardine recruitment than the traditionally emphasised spawning stock biomass. They also observed that marine heatwaves, varying across eco-regions, likely influenced sardine maturation and spawning patterns. With climate change expected to intensify these fluctuations, CMFRI scientists recommend the development of species-specific, short-term forecast models and adaptive local harvest controls.

"Dynamic harvest strategies tailored to the highly environment-driven sardine fishery are essential for sustaining livelihoods and ensuring food security," Dr Ganga pointed out.

The study underscores the need for climate-smart fishery management to protect one of India's most crucial marine resources.

/IANS