SPATIAL DISTRIBUTION OF Thunnus.sp, VERTICAL AND HORIZONTAL SUB-SURFACE MULTILAYER TEMPERATURE PROFILES OF IN-SITU AGRO FLOAT DATA IN INDIAN OCEAN

Agus Hartoko


Abstract


The study was the first ever attempt in fisheries oceanography sciences to explore the empiric correlation
between the spatial distribution of tuna (Thunnus.sp) and sub-surface in-situ temperature data. By means of
optimalization and use of an in-situ data of both vertical and horizontal which will be processed into a
multilayer subsurface seawater temperature of ARGO Float in Indian ocean. So far only sea surface
temperature (with temperature around 29 °C) data were used to look for the correlation for tuna spatial
distribution, while the Thunnus.sp swimming layer as widely known is in about 80 – 250m depth with
seawater temperature between 15 – 23 °C. The noble character of ARGO Float data is as in-situ data
recorded directly by the sensors, transmitted to the satellite, transmitted to the ground station and ready to be
used by researcher all over the world.In the study, about 216 seawater temperature coordinates of ARGO
Float and actual tuna catch data in the same day were used to represent the dry season (April – November
2007) analysis, and about 90 data were used for the rainy season (December – March 2007). The actual
tuna catch and its coordinates data were collected with permission from PT. Perikanan Samudra Besar,
(PT.PSB) Benoa – Bali Indonesia. Then both seawater temperature and tuna data were processed using a
Krigging method or spatial interpolation method.Based on a monthly actual tuna production by fishing fleet
of PT.PSB operated in Indian Ocean indicates that there were two cycles of low catch in March and July and
high catch in May and December 2007. In general, seawater temperature in depth of 80m, 100m, 150m and
200m of the dry season was 2 °C warmer than those of the rainy season. Range of seawater temperature will
decrease due to the water depth, range of seawater temperature at depth of 150m was between 14 – 22 °C
and at depth of 200m between 12 – 20 °C. Based on the regression and correlation between tuna catch and
seawater temperature revealed that seawater temperature at depth 150m has the highest coefficient of
correlation than to the seawater temperature at depth 100m and 200m.


Keywords


spatial distribution; subsurface seawater temperature; Thunnus.Sp; Indian ocean

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