What is a Potential Fishing Zone (PFZ)?

like 727 Posted By : ScienceIndia Administrator

Indian marine capture fishery is a typical multi-species tropical fishery. The first major rise in annual marine fish production occurred in the 1960s with the introduction of mechanization to the fleet. However, fishery remained mostly an individual affair and to date, it has not yet taken any significant corporate shape. This has inhibited the fleet from venturing away from the shore in many parts of the country until early 1990s, when primary studies towards locating resources with the help of satellites started. Fishery research organizations, with the help of Indian Space Research Organization (ISRO) laboratories conducted such primary studies with encouraging results. These efforts were utilizing data from the NASA, NOAA and ESA satellites such as the MetOp series for Sea Surface Temperature (SST) and MODIS & SeaWiFS for chlorophyll concentration.

Productivity of oceans depends on nutrient availability in the sun-lit upper waters, known as the euphotic zone. Oceanographic phenomena such as upwelling help contribute to much of this requirement, by entraining nutrients above the mixed layer depth and in turn, allowing phytoplankton to sustain a food-web with the help of photosynthesis. The stronger the upwelling, the deeper the upper mixed layer of oceanic water column. This allows colder nutrient-rich waters to surface, lowering SST. Thus, SST provides a clear signature for detecting upwelling zones with the help of remote-sensing data. Productive waters may initially attract only planktivorous fishes, but eventually also to bigger fishes, which prey upon them. This is the very reason for why and how SST was first harnessed as a tool of fishery resource predictions. Commercially important species, such as Tuna, are known to have temperature specificity as reflected in a positive correlation of specific temperature ranges with better hooking rates. Ocean-color missions have enhanced our understanding of ecosystem-level interactions in the oceans. Cooler SST signature with higher concentrations of chlorophyll relative to the surrounding waters indicates upwelling-induced productivity and has been correlated with higher Catch per Unit Effort (CPUE).

At the end of the 1990s, India launched its first satellite for the study of oceans – IRS-P4, known as Oceansat-1. Oceansat-1, with Ocean Color Monitor (OCM) sensor onboard, started providing chlorophyll concentration data. This was followed by the initiation of Potential Fishing Zone (PFZ) advisory program, as a free service to the Indian fisher community within Indian EEZ (Exclusive Economic Zone). Initially, this service used SST data from NOAA series of satellites. Eventually, data from more satellites, such as MODIS and MetOP, were also incorporated. The service initiated as a one-day delay product that was made available twice-weekly, and is now being provided in Near-Real Time (NRT) mode on daily basis. Today, the Indian Marine Fishery Advisory Services (MFAS) is a unique program with decade-plus long experience and a data-archive, reaching thousands of the Indian fishermen on daily basis. Controlled validation experiments that employed identical fishing boats to compare fish catch from PFZ area to that from a non-PFZ area were undertaken. Such experiments, carried out in the past decade, have shown mostly positive and encouraging results. Similarly, from fishermen feedback, PFZ advisories are found to be beneficial in obtaining more profit by reducing search time (and fuel consumption) for the fish-shoals. This, in turn, helps lowering India's carbon footprint by cutting carbon emissions per unit mass of fishes caught. While the ISO-certified PFZ service caters only to the operational Indian fisheries community; it contributes positively to the capacity building of the Indian Ocean-rim (IOR) countries by regularly providing training to researchers from these countries.

Author: Dr Nimit Kumar, Scientist (ISG), Indian National Center for Ocean Information Services (INCOIS), Hyderabad.