A recent study by the ICAR-Central Marine Fisheries Research Institute (CMFRI) has shed light on a crucial ecological puzzle: how monsoon rainfall trends directly led to the unexpected surge of young Indian oil sardines along Kerala’s coast in 2024. This phenomenon had significant ecological and economic repercussions.
Published in the journal *Current Science*, the research emphasizes that climate-driven oceanographic shifts are the primary architects behind the dramatic ‘boom-and-bust’ cycles observed in this crucial fishery. The findings highlight an urgent need for advanced, dynamic fishery forecast models and adaptive harvest regulations to better manage these fluctuations.
The Indian oil sardine population has seen wild swings in recent years. After a record-breaking catch of four lakh tonnes in 2012, numbers plummeted to a mere 3,500 tonnes by 2021. However, 2024 brought a surprising reversal: an unprecedented influx of juvenile sardines, typically around 10 cm in length, appeared along Kerala’s coastline. This surge was so substantial that mass beaching events were reported in districts like Kozhikode and Thrissur.
To understand this complex pattern, CMFRI researchers meticulously combined fisheries biology data with oceanographic observations collected from key locations like Kochi, Vizhinjam, and Kozhikode. Their analysis revealed that strong monsoon rainfall trends, combined with nutrient-rich upwelling in the ocean, created ideal conditions. This boosted the growth of microplankton – the essential food source for sardine larvae. The abundance of microplankton significantly increased the survival rate of these young sardines, resulting in the massive recruitment observed.
While the initial surge seemed positive, the sheer number of new sardines soon led to intense competition for limited food resources. This resulted in undernourished fish and stunted growth for the young ‘zero-year-class’ individuals. Principal Scientist U. Ganga, who spearheaded the study, noted the severe economic consequences: a dramatic crash in sardine market prices and the subsequent suspension of juvenile fishing activities.