Influence of mesoscale eddies on a commercial fishery in the coastal waters of the Andaman and Nicobar Islands, India

Mesoscale eddies enhance the productivity in a stratified coastal environment by upwelling. The seas around the Andaman and Nicobar Islands have been found to have frequent mesoscale eddy activity. Commercial fishing grounds coincide with upwelling areas associated with cyclonic and anticyclonic eddies and also with areas between two adjacent eddies. There are different eddy zones supporting different types of fishing gears and fish. The current study aims at identifying the different zones of mesoscale eddies in the Andaman Sea and compares the productivity and fishing activity in each of them. Data collected from 454 commercial fishing trips in the Andaman Sea along with maps of sea level anomaly and Moderate Resolution Imaging Spectroradiometer (MODIS) global level 3 mapped thermal infrared (IR) daytime sea surface temperature (SST) from the Aqua and Terra satellites were used for the study. Known upwelling areas such as the periphery of anticyclonic and the core of cyclonic eddies showed higher catches in longlines, ring seines among the fishing gears, and among all the fish species groups. Downwelling areas such as the periphery of cyclonic and the core of anticyclonic eddies showed lower catches with ring seines and the fish species groups. Areas in between adjacent eddies were explored in this study and the fish captures in such areas were found to be different with types of fishing and the target fish group. The study shows results that link eddy activity with the performance of a fishery

A remote sensing approach to explore the available water spread for fisheries development in the reservoirs of Godavari River Basin, Telangana, India

Reservoirs have tremendous fisheries potential amongst the inland water resources and aptly referred as ‘sleeping giants’, as the fish yield potential of these resources are yet to be tapped. Existing gaps in the availability of absolute information and data on the inland water resources hinder the applicability and implementation of various fisheries development programmes, which in turn impact inland fisheries production. The present study was carried out in the reservoirs viz., Sri Ram Sagar, Kaddam and Swarna from the Godavari Basin, covering the period 2016-2021, as a case study to demonstrate the use of remote sensed data in fisheries stock enhancement planning. The perennial and seasonal water spread area of the reservoirs under study, estimated through composite water maps prepared using Sentinel 2A data ranged between 8 to 19 and 4 to 29%, respectively. Further, the potential area for enclosure fish culture (both cage and pen culture) in these reservoirs were found to range between 14.89% (Sir Ram Sagar) to 48.54% (Kaddam). The field validated results revealed less than 0.1% of the perennial water spread area mapped in these reservoirs is under use for cage culture. This highlights under-utilisation of these reservoirs and demonstrates scope for developing enclosure fish culture or other culture-based fisheries for enhancing the fish production. The study also demonstrates the use of geospatial tools in development planning for expanding enclosure fish culture in the reservoirs and in turn enhancing fisheries production from the reservoirs in India. Keywords: Composite water maps, Enclosure fish culture,  Geospatial tools, Godavari River, NDWI, Reservoir, Sentinel 2A data, Water spread area</jats:p

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Not AvailableInland lentic waterbodies have a major role in contributing to nutritional and livelihood security of the rural poor in India. Generating a spatio-temporal resource inventory of the small waterbodies has immense potential in evidence-based fisheries development planning, so as to enhance the fish production (quantity) and productivity (quantity per unit area). The present study provides a framework for mapping these waterbodies using high resolution Cartosat 1 PAN and IRS ResourceSAT LISS IV merged imagery, determining the spatio-temporal water spread area and effective water spread area available for fish culture using Sentinel 2 Multi Spectral Imagery, for the years 2016–18. It provides an approach for determining the number of fingerlings required and estimating the production potential under standard production parameters, based on the extent of water available for fish culture in the waterbodies. The framework was piloted in Chhattisgarh, a landlocked State in Central India, which has a large number of inland waterbodies. A total of 121,529 waterbodies, with an area of 202,016 ha were mapped, of which 97% had an extent less than 5 ha. The total extent of waterbodies was 37% higher than the most recent estimate by Government of India. Availability of water in the waterbodies of the state, for a duration of at least 8 and 11 months in a year, was found to be 74% (149,484 ha) and 50% (102,167 ha) respectively, which indicates the vast scope for promotion of intensive aquaculture in the state. Minimum number of fingerlings required for stocking the available water was estimated as 403 million. This framework can be replicated across the country and other regions with poor in-situ data, for effective management of inland waterbodies through location-specific data-driven intervention planning

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Not AvailableMesoscale eddies are important ocean phenomena that enhance biological productivity by mixing of water column and influence fishery catches, especially in stratified seas such as Bay of Bengal and Andaman Sea. The current study was conducted around the Andaman and Nicobar Islands (ANI), India located in the Eastern Indian Ocean. The study tested the feasibility of targeted fishing in eddies, by characterizing the mesoscale eddies in the region, towards developing operational altimetry-based fishery advisories for the fishers. We analysed fish catch data from 15,370 commercial fishing trips from the Islands using five fishing gears during 2014–17 spatially vis-à-visthe eddies delineated from Maps of Sea Level Anomaly (MSLA). We show that 5-24% of the routine commercial catches occurred in eddies, fishery catches are positively influenced by different eddy zones and the fish catch using different fishing gear are significantly higher in some of the eddy zones. We generated experimental advisories showing locations of eddies and their zones, identified using Near Real-Time M-SLA data and guided the commercial fishers for targeted fishing in eddies. The fish Catch Per Unit Effort (CPUE) from the experimental fishing within the eddy zones was significantly (p < 0.01) higher than that from the traditional fishing grounds in the non-eddy areas. The spatio-temporal analysis of eddies around ANI during 2009–16 showed the occurrence of higher number of anticyclonic eddies, majority of which move westward and have a lifespan of less than 2 weeks and amplitude less than 4 cm. In the current study, the areas around ANI with frequent eddy occurrence and eddy density have been identified, which could aid in increasing the fishing intensity by targeting the pelagic fishes, using longlines, gillnets and ringnets. Thus, we show the possibility of using eddy fishing advisories generated from altimeter data, for augmenting the currently operational Potential Fishing Zone (PFZ) advisories that are generated using optical/thermal remote sensing data and disseminated to the coastal fishers in India. This will be helpful especially for the regions with and during periods of persistent cloud cover.National Remote Sensing Centre (NRSC), Indian Space Research Organization (ISRO), [RRSC -NRSC -2018

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Not AvailableMesoscale eddies are important ocean phenomena that enhance biological productivity by mixing of water column and influence fishery catches, especially in stratified seas such as Bay of Bengal and Andaman Sea. The current study was conducted around the Andaman and Nicobar Islands (ANI), India located in the Eastern Indian Ocean. The study tested the feasibility of targeted fishing in eddies, by characterizing the mesoscale eddies in the region, towards developing operational altimetry-based fishery advisories for the fishers. We analysed fish catch data from 15,370 commercial fishing trips from the Islands using five fishing gears during 2014-17 spatially vis-a-vis the eddies delineated from Maps of Sea Level Anomaly (M-SLA). We show that 5-24% of the routine commercial catches occurred in eddies, fishery catches are positively influenced by different eddy zones and the fish catch using different fishing gear are significantly higher in some of the eddy zones. We generated experimental advisories showing locations of eddies and their zones, identified using Near Real-Time M-SLA data and guided the commercial fishers for targeted fishing in eddies. The fish Catch Per Unit Effort (CPUE) from the experimental fishing within the eddy zones was significantly (p < 0.01) higher than that from the traditional fishing grounds in the non-eddy areas. The spatio-temporal analysis of eddies around ANI during 2009-16 showed the occurrence of higher number of anticyclonic eddies, majority of which move westward and have a lifespan of less than 2 weeks and amplitude less than 4 cm. In the current study, the areas around ANI with frequent eddy occurrence and eddy density have been identified, which could aid in increasing the fishing intensity by targeting the pelagic fishes, using longlines, gillnets and ringnets. Thus, we show the possibility of using eddy fishing advisories generated from altimeter data, for augmenting the currently operational Potential Fishing Zone (PFZ) advisories that are generated using optical/thermal remote sensing data and disseminated to the coastal fishers in India. This will be helpful especially for the regions with and during periods of persistent cloud cover.National Remote Sensing Centre (NRSC)Indian Space Research Organization (ISRO), [RRSC - NRSC - 2018