How ocean science is feeding coastal India
Every morning, as fishing boats head out to sea, they carry more than just nets and bait; they carry insights from space. Thanks to the Indian National Centre for Ocean Information Services (INCOIS) under the Ministry of Earth Sciences, thousands of fishermen are guided by Potential Fishing Zone (PFZ) advisories, generated using high-resolution satellite data and oceanographic analysis.
These advisories, based on parameters such as sea surface temperature, chlorophyll concentration and ocean currents, pinpoint likely fish-rich areas, thereby helping fishermen cast their net with more confidence. The result? Better catches, higher incomes, lower fuel costs and a smaller carbon footprint.
PFZ advisories are generated using high resolution satellite data from multiple sources and then disseminated to the fishermen daily.
The impact is measurable. A survey by the National Council of Applied Economic Research, covering 757 fishermen across 34 districts in seven States, recorded 1,079 successful fishing trips guided by PFZ advisories. On average, each trip earned an additional ₹17,820, collectively netting extra income of ₹1.92 crore.
INCOIS director T.M. Balakrishnan Nair, who carried out a study on the efficacy of PFZ advisories along with his team of scientists, found that 52% of fishermen received the advisories and 35% actively used them.
In a follow-up study conducted in 117 Kerala villages between 2022 and 2023, Nair's team found a clear link between PFZ access and increased fish catch. The southwest coast, particularly Kerala, accounted for 37% of India's marine fish landings in 2023 with 69% of the catch comprising sardines and mackerel.
In villages with major fishing harbours and landing centres such as Azheekkal, Beypore, Chellanam, Fort Kochi, Munambam, Neendakara and Sakthikulangara, the daily catch often exceeded 100 tonnes and occasionally peaked at 500 tonnes.
'Our findings revealed significantly higher fish catches on days when PFZ advisories were used, and even on the following day, validating their effectiveness across a wide area,' explained the INCOIS director. The analysis also revealed an interesting trend: planktivorous fish dominated catches on PFZ days, while carnivorous species were more common the next day, indicating a transfer of productivity through the food chain.
The study, conducted between June 2022 and March 2023, found peak PFZ activity during July to September, coinciding with peak southwest monsoon. This period of increased ocean surface productivity, driven by monsoon winds, was marked by high chlorophyll levels and cooler sea surface temperatures due to coastal upwelling, which are ideal conditions for fish aggregation. During both the monsoon and post-monsoon seasons, planktivores and carnivores continued to dominate the catch.
Scientists observed that nearshore PFZ occurrences were most frequent during the pre-monsoon months, especially February and March, a period that usually sees lower fish catch compared to the monsoon and post-monsoon seasons. This highlights the seasonal variability of PFZ events, which are closely linked to changing environmental conditions.
The study found that planktonic prey, which is critical for planktivorous fish, peaked during the monsoon and post-monsoon periods. In contrast, prey species for carnivorous fish remained consistently available along the coast throughout the study period.
Interestingly, the highest fish catches were often recorded the day after PFZ advisories were issued. Scientists believe this is due to a combination of fish aggregation patterns and the time fishermen take to act on the information. This insight enhances understanding of how timing affects the effectiveness of PFZ advisories.
The research also underscored the value of using village-specific landing data to study coastal ecosystem productivity. Village-level catch data, when analysed alongside satellite-derived environmental information, can offer early indicators of ocean productivity and its link to fishery abundance, added Nair.
The study recommends further refining PFZ advisories by incorporating local factors such as dominant gear types, craft used and operational depths. It also calls for in-situ experiments and long-term monitoring at dynamic and persistent ocean fronts to better understand changes in environmental triggers and food chain shifts, which are key to improving future fisheries forecasts.
'The study validates that PFZ events are associated with higher catches. It also demonstrates the potential of using village-specific landing data to explore productivity dynamics in coastal ecosystems,' said Nair.
Other scientists involved in the study included Dhanya Mohan Lal, Harisha, Alakes Samanta, Sudheer Joseph and Sanjiba Baliarsingh.
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