Oceanographic preferences of yellowfin tuna (Thunnus albacares) in warm stratified oceans: A remote sensing approach

Yellowfin tuna (Thunnus albacares, Bonnaterre, 1788; YFT) face extensive exploitation pressure worldwide owing to the attractive economics of these fisheries. A better understanding of how oceanography influences the distribution of YFT (or highly migratory species more generally) will improve the ability for fisheries management policies to achieve conservation (e.g., maintain a stocks reproductive capacity), economic (e.g., maximize gross domestic product), and social (e.g., optimize successful fishing opportunities) objectives. Such ecosystembased linkages, when combined with real-time remote sensing data, provide the predictive framework for enhancing favourable fishing opportunities and limiting excessive harvest. We examined factors influencing YFT distribution and behaviour using pop-up satellite archival tags and remotely sensed oceanographic data from two regions in the northern Indian Ocean. Tagged individuals did not exhibit significant deep diving or diurnal behaviour, and preferred ambient temperatures of 26–30°C and 25–29°C in the Arabian Sea (AS) and the Bay of Bengal (BoB), respectively. In general, tagged YFT were found to be in waters with sea surface temperatures of 26–29°C, 60% of the time andwithin a sea surface height-anomaly of ±6 cm 70% of the time. YFT avoided moving below the relatively shallow oxycline depth, which is indicative of the stratified waters of the AS and the BoB. Low dissolved oxygen levels are likely a limiting factor for tuna movement given their high oxygen demand. The northern Indian Ocean provides an opportunity to study climate impacts on fish distribution and movement, and our findings provide a basis for understanding how habitat and migratory patterns may be altered under climate change

Probing the defect-induced magnetocaloric effect on ferrite/graphene functional nanocomposites and their magnetic hyperthermia

FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULORecently, the development of an alternative magnetic refrigerant for the conventional fossil fuels attracts the researchers. We discussed the structural defect-induced magnetocaloric effect (MCE) in Ni0.3Zn0.7Fe2O4/graphene (NZF/G) nanocomposites for the first time. Single-phase spinel ferrite nanocomposites with an average size of 7-11.4 nm were achieved by using the microwave-assisted coprecipitation method. The effect of graphene loading on the structural and magnetism of NZF/G nanocomposites was elaborated. Raman analysis proved that the interface interaction between NZF and graphene yielded different densities of structural defects. In view of magnetism, superparamagnetic NZF nanoparticles showed a magnetic entropy change (-Delta S-M(max)) of -0.678 J.kg(-1) K-1 at 135 K, whereas the NZF/G nanocomposites exhibited superior -Delta S-M(max) at cryogenic temperatures and the defect-induced MCE change was indeed similar to the I-D/I-G intensity ratio. The nanocomposites exhibited different magnetic orderings between 5 and 295 K, and it was varying for I-D/I-G, 1.83 gt; 1.68 gt; 1.57 as antiferromagnetic (AFM) gt; AFM/ferrimagnetic (FiM) gt; FiM, respectively. Till now, NZF/G nanocomposites showed an inverse MCE of 4.378 J.kg(-1) K-1 at 35 K and a refrigerant capacity of 88 J.kg(-1) for 40 kOe, which was greater than the ferrites reported so far. Finally, MCE and magnetic hyperthermia were correlated at ambient conditions. These results pave the way for ferrite/graphene nanocomposites for cooling applications.123422584425855FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO2018/19096-1The authors greatly acknowledge FONDECYT Postdoctoral Research project no.: 3160170, CONICYT PIA/APOYO CCTE AFB170007 and CONICYT BASAL CEDENNA FB0807, Government of Chile and FAPESP Postdoctoral Fellowship Process Number (2018) 19096-1, Government of Brazil for financial assistance. We extend our gratitude to Prof. Lorena, Universidad Austral de Chile, Valdivia, for the Raman spectral measurements (FONDEQUIP EQM 160050 project)