Utilizing Remote Sensing and GIS to Determine the Role of Temperature in Sardine and Tuna Distribution in the Gulf of Guinea

Abstract

The Gulf of Guinea is a part of the Atlantic Ocean that sinks in a corner towards the center of the African continent. It is an area that is home to many species of fish, including sardines (sardinella aurita) and tuna (katswonus pelanis). These two species of fish are particularly important economic and food sources for the zone/area in general and for the local population in particular. However, it must be said that over time, the sharp increase in the temperature of the Gulf of Guinea represents a huge risk for the fish stocks available in some parts of the Gulf. Faced with this problem, it is essential to conduct a study on temperature in the Gulf of Guinea to draw up the precise mapping of the areas potentially favourable for fishing these two species. In order to achieve our objectives, we have given priority to using remote sensing techniques as a means of studying and analysing the data. Firstly, it was the task of exploiting the sea surface temperature algorithm to determine the temperature of maritime waters, and then, thanks to the review of the literature, the different intervals of salinities, nitrate and bathymetry necessary for the life of these two species of fish were determined. Following this, it was discussed to proceed thanks to the MeToP-NOAA satellite image by a reclassification of the pixels taking into account the above-mentioned intervals, which, after calculation, made it possible to determine the different areas favorable to the tuna and sardine fishery. As for the results, we obtained six (06), of which four (04) correspond to the sea surface temperature of the Gulf of Guinea over the last thirty (30) years (1990 to 2020), which shows gradually the increase in sea surface temperature and two maps that show the areas favorable to tuna and sardine fishing. This study made it possible to highlight the consequences of the increase in sea temperature of the Gulf of Guinea (with an average of 2.7°C to 3.6°C) in the areas favorable to the fishing of sardines and tuna. With regard to fishing zones, all countries have areas that are very favourable to sardine fishing. However, only Gabon, Sao Tome and Principe, and the area of the island of Annobón (Equatorial Guinea) have areas favourable to tuna fishing. If nothing is done to regulate the climate, by 2030, we will have a temperature increase of up to 26°C for the hottest areas and 23.3 °C for the mildest areas. This would have a great impact on both species of fish but more on tuna because of its lower metabolism and high demand in the markets. Sardines, on the other hand, can, thanks to their faster metabolism, better adapt to changes in sea temperature and constitute an important source of economic and food income for the countries of the Gulf of Guinea.