The distribution of bigeye tuna, Thunnus obesus, and three-dimensional thermal structure estimated from satellite altimeter
Akiko Takano(1) and Hidekatsu YAMAZAKI(1)
Tokyo University of Marine science and technology,
4-5-7, Konan, Minato-ku,Tokyo,
Images of sea surface height (hereafter SSH) derived by satellite altimeter have been used in Japanese tuna fishery. Fishermen empirically know that most of favorable fishing grounds locate at boundaries between high and low SSH area. Although good fishing ground appears near the boundary of different water masses, the dynamics and the mechanism of fish concentration are not well understood. In order to improve the accuracy of fish distribution, one needs to know oceanographic conditions where fish concentrate.
In this contribution, we propose an empirical approach to estimate three-dimensional thermal structure in real time using satellite altimeter data. Making use of a two layer system model (Goni et al, 1996), an empirical regression model for three-dimensional thermal structure is derived combining absolute dynamic topography (ADT) by AVISO, in-situ data of temperature and salinity measured by Argo data, and monthly mean objective analysis data of temperature and salinity.
We have applied the proposed technique to estimate three-dimensional thermal structure of mid-Pacific ocean. We show a good agreement between the model result and observed temperature profiles taken from XBT. We also demonstrate that the location of bigeye tuna (Thunnus obesus) fishing ground appears near the boundary of different water masses.