Mesoscale Eddies and Yellowfin Tuna Catches in the Western Arabian Sea
SERGEY A. PIONTKOVSKI 1*AND KHALID A. AL-HASHMI 2
College of Agricultural and Marine Sciences, Sultan Qaboos University, P.O. Box 34, Al-Khod 123, Sultanate of
Daily maps of sea surface heights retrieved with 4-km spatial resolution from the MODIS-Aqua scanner and obtained over 13 years of remote sensing (from 2002 to 2015) were used to quantify monthly variations of 1108 cyclonic and 1090 anti-cyclonic eddies.
The seasonal cycle of eddy occurrence has demonstrated two peaks, both corresponding to the spring and fall Inter-monsoon seasons. The amount of eddies observed during Inter-monsoon seasons was by ~ 30% higher than those of the South-west (winter) and North-east (summer) monsoons. Seasonal cycles of eddy occurrence were compared to Yellowfin Tuna landings. Two peaks of landings corresponding to April and October (which are cores of the spring and fall Inter-monsoon seasons) were observed. A positive linear correlation between the total number of cyclonic plus anti-cyclonic eddies and Yellowfin Tuna landings was statistically significant. Also, it holds for the cyclonic and anticyclonic eddies analyzed separately. Results of the Principal Component Analysis incorporating 12 environmental parameters (including wind speed, sea surface temperature, dissolved oxygen, nutrients, chlorophyll-a, sardine catches, and key indices of atmospheric anomalies) demonstrated that mesoscale eddies might be treated as ecologically important regional phenomena affecting seasonal variations of Yellowfin Tuna landings over the Omani shelf.
Key Words: Arabian Sea; Mesoscale Eddies; Yellowfin Tuna
Physical Controls on Oxygen Distribution and DenitrificationPotential in the North West Arabian Sea
Bastien Y. Queste1, Clément Vic2, Karen J. Heywood1, and Sergey A. Piontkovski3
1Centre for Ocean and Atmospheric Sciences, School of Environmental Sciences, University of East Anglia, Norwich, UK
2Department of Ocean and Earth Sciences, University of Southampton, Southampton, UK
3College of Agricultural Marine Sciences, Sultan Qaboos University, Muscat, Oman
At suboxic oxygen concentrations, key biogeochemical cycles change and denitrification becomes the dominant remineralization pathway. Earth system models predict oxygen loss across most ocean basins in the next century; oxygen minimum zones near suboxia may become suboxic and therefore denitrifying. Using an ocean glider survey and historical data, we show oxygen loss in the Gulf of Oman (from 6–12 to <2 μmol/kg1) not represented in climatologies. Because of the nonlinearity between denitrification and oxygen concentration, resolutions of current Earth system models are too coarse to accurately estimate denitrification. We develop a novel physical proxy for oxygen from the glider data and use a high-resolution physical model to show eddy stirring of oxygen across the Gulf of Oman. We use the model to investigate spatial and seasonal differences in the ratio of oxic and suboxic water across the Gulf of
Oman and waters exported to the wider Arabian Sea.
Taxonomic Composition and Seasonal Changes of Fish Larvae
Assemblages in Coastal Waters of Muscat, Sea of Oman
1Nadir M. Al-Abri, 2Sergey A. Piontkovski, 3Mahnaz Rabbaniha, 2Khalid Al-Hashmi and 1Tatyana Chesalina
1Marine Science and Fisheries Center, Muscat, Sultanate of Oman
2College of Agricultural and Marine Sciences, Sultan Qaboos University, P.O. Box 34, Al-Khod 123, Sultanate of Oman
3Iranian Fisheries Research Organization, P.O. Box 14155-6116, Tehran, Iran