Fisheries sector comprises mainly of fish catches form capture where the fish is captured from rivers or large reservoirs or Inland water bodies which have freshwater, in which case It is called inland capture fishery. The fishes captured from the seas contribute to Marine capture fishery. In capture fisheries, there is no effort made to grow the fish which are basically the wild fishes. Aquaculture or culture fisheries, has developed over past 3-4 decades where the fish are farmed in artificial or natural water bodies, something like agriculture. Fishes grown in fresh water/ brackish water, in the inland areas constitute the inland culture fishery. Brackish/ marine water fishes cultured in coastal culture systems along the coast or in cages/pens and artificial structures in the natural water bodies constitute the marine/ brackish water aquaculture.
Current Scenario of Indian Fisheries
Global fish production form capture has remained relatively stable over the past two decades while fish production through aquaculture has progressively increased. The Indian fisheries sector has come a long way since independence and has contributed immensely to the food basket of the country, with annual production levels of over nine million tons of fish (2014) and shellfish from capture fisheries and aquaculture. India is the third largest producer of fish and is playing an important role in global fisheries. Furthermore, with production over 4.88 million metric ton, the country occupies second position in the global aquaculture fish production. In the last six decades, Indian fisheries have made great strides, with the annual production increasing from 0.75 million tons of fish and shellfish in 1950 to about 9.6 million tons in the year 2014, indicating an increase of about thirteen fold. While capture fisheries have solely contributed production for the marine sector, aquaculture contribution in the inland fisheries sector has been significant in recent years. The production from capture fisheries in the last thirty four years has grown by only 227% i.e. from 2.08 million tons in 1980 to 4.72 million tons in 2014, but the aquaculture sector has shown a growth of over 1300% in the same period, i.e. 0.37 million tons million tons in 1980 to 4.88 million tons in 2014. The country has also emerged as one of the major countries in exports, recording a peak during the year 2014-15, with earnings of about Rs.33442 crores. However, here has been a decline of 5.46% during 2015-16 due to economic recession and steep decline in prices in the international market.
Role of Remote Sensing in Fisheries
Remote sensing is not entirely new to fishermen harvesting living marine resources. Traditional fishermen from ages have been using visual form of remote sensing with the help of naked eye. In the process of elevating themselves above the water surface, a fisherman has using crow’s nests on ships, hot-air balloons, and aircrafts. The sensor often used has been the naked eye usually aided by binoculars or telescopes. Visual form of remote sensing is common in many fisheries worldwide. The use of helicopters operating from modern Tuna Purse Seiners fishing on the high seas is common. In addition, aircraft carrying instruments for making oceanographic measurements have been used for supporting fisheries research studies for locating areas favorable for fishing and for locating shoals of fishes. The most successful among all the tools is satellite remote sensing in which a satellite fitted with sensor is used for viewing the ocean. The success is mainly because of its ability to cover vast area of ocean in the minimum possible time. Exploration of fishery resources using remote-sensing techniques is based on the development of methods for identification of feeding grounds where fish tend to accumulate. In general, physical factors such as wind and temperature affect the mixing of the water column. When such events occur, the input of nutrients to the photic zone promotes the growth of phytoplankton. The increase in phytoplankton biomass and zooplankton community grazing on it attracts pelagic fish to these areas. Similarly, the sinking of fecal pellets and senescent phytoplankton form regions of high biological activity will support the feeding of demersal fish as well. It has been established that fronts in thermal or chlorophyll gradients often indicate areas of high biological productivity. Moreover, from field and satellite data, optimal physical and biological conditions have been established for some commercial fish, such as the skipjack tuna and the Japanese common squid, both species commercially fished in Japanese waters, which allow identification of areas with high catch probability.
Remote Sensing of Ocean colour for locating productive fishing ground is being form ages even by traditional fishermen. In those cases naked eyes were used for pointed and they had to sail to the particular location. The potential of using space was first demonstrated by Kemmerer. In this study ocean colour measurement from Landsat were used to predict areas of high probability of occurrence of menhaden in the Gulf of Mexico. The following ocean colour measurements by the remote sensing satellites are used in fisheries resource applications:
- Locating ocean forts, their effluence and circulation patterns
- Quantitative determination of ocean colour that can then be directly related to
- Chlorophyll concentration.
- Identification of water masses
The satellite images and concurrent albacore catch data examined by Laurs &Beck clearly demonstrate that distribution and availability of albacore are related to ocean fronts. He also substitutes the conventional wisdom of many fishermen to use temperature ad colour gradients to locate potentially productive fishing areas for albacore. Shannon et al. 1983 predicted that the information available on chlorophyll gradients along with the thermal fronts could be possibly used for powerful management tool for fisheries purposes.
Research in India also was in these lines the Sea Surface Temperature (SST) information was being used for PFZ identification for over a decade. Chaturvedi.et al. (2000) attempted to establish inter-relationship between satellites derived chlorophyll and temperature profile data collected from survey vessels during 1997-98. The constraint in Indian waters was narrow temperature ranges could always not be linked to aggregation and availability of fishes. There was now a need for identifying another parameter that could be linked to temperature gradient. Ocean colour information effectively filled in the lacuna.
Ocean colour indicates the surface productivity of the ocean. Other processes such as temperature gradient, wind direction etc would help understanding the feature much better. Presently synchronous IRS-P4 OCM and NOAA-AVHRR SST data is used for the identification of PFZ. The fishery and oceanographic data collected by ship’s cruises are being used for the forecast validation. The features for PFZs. The advanced phase of productivity is indicated as chlorophyll features and probably in SST image and also as follow:
- Strong gradients;
- Persistence
- Features seen on both colour and SST image
- In the case of upwelling stabilization phase
- Centre of the core ring
- Edges of the warm core ring
- Anticyclone eddy
- Cyclonic eddy
- Fishing limits
- Vessel position in case of survey vessels
Satellite infrared thermal data
The satellite infrared thermal data is being used effectively for fisheries research in many countries. The data is used to define marine habitats of fishery resources using satellite data, which are collected contemporaneously with fishery/ biological data and ground truth measurements gathered by research and fishing vessels. It also describes and explains variability in circulation and water mass distributions using satellite data alone or in conjunction with physical oceanographic measurements, with a view toward understanding the influence of ocean variability on fishery resources and fishing grounds.
Source: Aqua Aquaria