Utilization of satellite Remote Sensing for exploitation of anchovy, sardine and other commercially utilized fishes

Utilization of satellite Remote Sensing for exploitation of anchovy, sardine and other commercially utilized fishes

Wang Faji
Yellow Sea Fisheries Research Institute, Qingdao, China

Han Shixing
East China Sea Fisheries Institute, Shanghai, China

Jin Manyi
Chinese Academy of Fishery Science, Beijing, China

Abstract
The present paper deals with utilization of IR and visible images of NOAA satellite to analyse the formation and structure of fishing grounds of anchovy (Engraulis japonius), sardine (Sardinops melanosticta), blue-spotted mackerel (scomberomorus niphonius), mackerel (pneumatophorus japonicus ) and round scad (Decapterus maruadsi), and prediction experiments on the fishing grounds of blue-spotted mackerel, mackerel and round scads.

Intouduction
In 1986-1989, according to instruction from fishery Department of the Ministry of Agriculture, a series of experiments was conducted on satellite remote sensing technology applied to fisheries in Chinese coastal regions. The present paper discusses the utilization of satellite remote sensing images for analysing formation and structure of fishing grounds of anchovy, sardine, blue-spotted mackerel, mackerel and round scads.

Material and method

Data of fishing grounds: those used fishing records made by Chinese research vessels, experimental-fishing vessel and fishing vessels.
Data of satellite: those used were remote sensing data of meteorological satellite NOAA obtained by Chinese meteorological departments.
Technical measures and methods
1. Satellite images selected were processed by computer according to the procedures of image enhancement, mapping isotherms, atmospheric correction, projection transform and density slicing.
2. Processing of satellite images was done according to living habits of target species to get prediction index which could correctly reflect fishery information law.
3. To improve precision of prediction , analysis and prediction of fishing grounds were by using method of comprehensive study of information.
4. Various types of satellite remote sensing information were transferred by wire or wireless fax, telegram and mail:

Analysis of formation of fishing grounds

Fishing ground of anchovy in wintering migration.

The chief reason for fish's wintering migration is that the temperature in feeding grounds gradually drops and the fish are compelled to move to waters where the environment is favourable for their growth.

Anchovy are migratory pelagic fish in the Yellow sea and the East Chinese Sea. In every Autumn, as temperature declines, anchovy begin to make their wintering migration, Leaving spawning and feeding grounds southwards for deeper waters. The suitable temperature range for anchovy in wintering period is 8-15°C, optimal from 11 to 13°C.

Satellite IR images of December 1986-March 1987 systematically reflected variation characteristics water temperature in the Yellow Sea in winter. In the period of November-December, water temperature in the area north 34°N, west 124° E generally ranges from 9-12° C. Therefore, in the period of November - December anchovy may migrate over a vast area, the population scattering. After January of next year, water temperature in the yellow Sea changes considerably. As indicated in fig. 1, cold water mass in coastal area of northern jiangsu province obviously expanded toward of - sea and water temperature in the area north 34°N, west 124°E, generally droped to below 9°C. A "s" typed distribution of dense isotherms of 11-13°C occurred at the area where the coastal water north Jiangsu and the Yellow sea warm current converged. Owing to smaller range of this "s" typed area, it could be deduced that under the effect of barrier provided by coasted could water of northern Jiangsu province, anchivy began to aggregate and population density became higher. The result of routine investigation revealed that in November to December both average M value and catch of anchovy were at lower level (M value shows relative value of school density by acoustic method to survey and evaluate fish stack), and only after January next. Year , both M value and catch of anchovy would increase evidently. The areas with a larger M value value and fish catch were located in the limits of 11~13°C isotherms illustrated on satellite images dated 14 January 1987.
Fishing ground of sardine in spawning migration.

Sardine is coastal migratory pelagic fish. The fish make spawning from March to Jane every year, when sea surface water temperature reaches 14~15°C. Fishing ground of sardine in the distant areas of the East china sea and its adjacent waters is mainly distributed in convergence area of Tsushima warm current, Korean coastal waters and mixed water masses in the southern Japan Sea, and obviously near the side of Tsushima warm current. In fig. 3 it could be seen that central fishing ground is located in convergence area of cold and warm water masses where there are 15~17° C isotherms as illustrated on satellite images. The formation of fishing grounds like this is closely related with the feeding habit of sardine. Excluding postlarve stage, sardine feeds on phytoplankton in great quantities in very growth stage. As phytoplankton grows very well under favourable environment in which water temperature ranges from 15~17°C., suedine tends to aggregate in an area where cold and warm water masses converge within isotherms of 15~17°C.
Fishing ground of blue-spotted mackerel in spawning migration.

Water transparency is one of important factors, which have influence on ecological habit of living organisms, therefore it is possible to infer the location of fishing grounds of some species according to distbution patterns of transparency. The fact has proved that fishing grounds of blue spotted mackerel in the southern Yellow Sea are located in convergence area of clear and turbid water and obviously near the side of turbid water as illustrated on images of satellite.
Fishing ground of mackerel and round scads in feeding migration.

In the Taiwan straits, owing to the effect of topography and costal direction wind , there often occur in summer upwelling and eddy current which could bring bottom nutrients into sea surface, accelerating growth of live food organisms and forming favourable feeding ground for fishes. Bases on location of upwelling and eddy current illustrated on satellite IR images in the Taiwan straits in summer 1988, predictions about fishing groun of mackerel and round scads have successfully made. From the point of view of formation and structure of fishing grounds, above mentioned fishing grounds of anchovy, sardine and blue-spotted mackerel belong to front type and those of mackerel and round scads belong to upwelling and eddy current type.

Prediction effects
From the result of prediction experiments it has shown that satellite remote sensing technology play an important role in fishing production in Fujan province and Rongchen city, Shandong province.

The result of comparison experiments revealed that the catch could be increased by 10~30% when fishing operation of blue-spotted mackerel was guided by satellite remote sensing data.
Based on location of upwelling and eddy current illustrated on satellite images with routine investigation data, locations of fishing grounds of mackerel and round be quickly found out. The predicted locations of fishing grounds fundamentally coincided with those of practical fishing grounds.

Conclusion

Sea condition information on the boundaries of water masses, upwelling , eddy current and transparency obtained from satellite images can provide important data for predicting fishing grounds of anchovy , sardine etc.
Chinese coastal fishing grounds mostly belong to these of front, upwelling and eddy currently types, therefore the application of satellite remote, sensing technology to observe or study on the generation and disappearance of ocean front upwelling and eddy current is of great significance in prediction fishing grounds and guiding fishing production in Chinese coastal regions.

References

Zhu De-shan et al. Marine Fisheries Research, 11 ( 1990) , 1.
Cui Mingyan, Marine fishery, 8 ( 1986), 103.