A steep rise in fishing pressure, combined with climate-related changes, could seriously affect sardine populations along India's southwest coast, researchers have warned. Scientists from the Indian Institute of Tropical Meteorology (IITM) and the National Centre for Ocean Information Services (INCOIS) analyzed over five decades of fish catch data from India's west coast and found that large-scale weather changes influence winds and ocean conditions, which determine food availability and breeding habitats for sardines.
Study Highlights Risks to Coastal Livelihoods
India is among the world's largest marine fish producers, and sardines constitute a major portion of the country's catch. Thousands of coastal households depend on sardine fishing for their livelihoods. The study, led by IITM scientist Vinu Valsala, has been published in the journal Ecological Modelling and marks the first model of its kind developed for the Indian coast. Other contributors include Inakonda Veera Ganga Bhavani and Faseela Hamza.
Climate-Driven Population Model
The researchers built a climate-driven population model for the Indian oil sardine (Sardinella longiceps), named BIOFIM. When tested against actual landing data from 1965 to 2017, the model successfully reproduced real-world fluctuations in sardine catch, including a major crash between 1980 and 2000 and the subsequent recovery. Oil sardines are not only a food source but also a key link in the ocean food chain as a forage species, feeding on plankton and serving as prey for larger fish, seabirds, and marine mammals.
Atmospheric Pressure Emerges as Key Factor
One surprising finding was that atmospheric pressure had the strongest influence on year-to-year changes in sardine numbers, more than sea surface temperature or air temperature. Valsala explained that changes in atmospheric pressure affect wind patterns and ocean currents along India's southwest coast, which in turn influence coastal upwelling—the process that brings colder, nutrient-rich water to the surface, supporting marine food chains.
Temperature Sensitivity
The study also found that sardines grow best within a narrow temperature range of 25.5–26.5°C averaged over the upper 75 meters of the ocean. When temperatures exceed this range, feeding conditions worsen. Periods of low sardine biomass, such as 1980–84, 1996–98, and 2014–17, coincided with temperatures above 26.5°C, offering clues about how warming seas may affect fisheries in the future.
Fishing Pressure Threshold
The researchers noted that the fishery remained relatively stable under small changes, but projected a sharp decline if fishing pressure increased by 40–50%. When both fishing and natural mortality increased together, fish populations fell substantially, highlighting how environmental stress and overfishing can combine to threaten long-term sustainability.
Oil sardines have a short lifespan of about two and a half years, making them particularly sensitive to disruptions in breeding and survival.
