Relationship Between the Spatiotemporal Distribution of Dominant Small Pelagic Fishes and Environmental Factors in Mauritanian Waters

The relationship between the spatiotemporal distribution of three dominant small pelagic fishes,including chub mackerel(Scomber japonicus),horse mackerel(Trachurus trecae)and round sardinella(Sardinella aurita),and the environmental factors in Mauritanian waters were analyzed by using 4 years of logbook data of commercial purse seine fisheries to improve the efficiency of fishery and management of sustainable exploitation.A Tweedie-generalized additive model(GAM)of 8-day average catches and the monthly geostatistical analysis of daily catches were used in this study to analyze the influence of environmental factors on catch per unit of effort(CPUEs)and to map the spatial distribution of three mixed dominant small pelagic fishes,respectively.A 10'×10' grid was used,and environmental factors were processed from remote sensing,including 8-day average sea surface temperature(SST),the nearest distance between SST fronts and CPUE position(Df),chlorophyll-a(Chl-a)concentration,salinity,and eddy kinetic energy.Results showed that 1)the distribution of three dominant small pelagic fishes might be related to the intensity of upwelling in Mauritanian waters;2)oceanic fronts might play a key role in the ecology of chub mackerel,horse mackerel,and round sardinella;3)Chl-a concentration might be associated with the feeding grounds of chub mackerel;4)the target species distribution appeared sensitive to gradient changes in the amount of salinity;5)three zones(northern,central,and southern)with variable abundances were delineated;and 6)a high concentration of the center of gravity in the central zone might be related to the strong upwelling of nutrient-rich waters.This study can provide new insights to enhance the fishery efficiency and sustainable exploitation management of purse seiners in certain area off Mauritania.

Characterization of refined fish oil from small fish in Mauritania

In this study,the effects of chemical refining on the physicochemical indices,environmental pollutants,lipid functional groups,relaxation characteristics,fatty acid profiles,and triglyceride(TG)molecular species in crude oil extracted from small fish in Mauritania were evaluated.The acid,peroxide,and iodine values of crude oil were identified as 5.52 mg KOH/g,1.73 meq/kg,and 200.78 g/100 g oil,respectively.After refining,these values were determined to be 0.29 mg KOH/g,0.76 meq/kg,and 210.80 g/100 g oil,respectively.The polychlorinated biphenyls and arsenic content of crude oil were identified as 32.30μg/kg and 1.00 mg/kg,respectively.After refining,these were not detected.The content of eicosapentaenoic acid(EPA)and docosahexaenoic acid(DHA)accounted for as much as 87.55%of the polyunsaturated fatty acids in the refined oil,indicating that high-quality fish oil is suitable as a food supplement.The correlation coefficient of the infrared spectra before and after refining was 0.968,and the relaxation time and peak shape data were almost similar before and after purification.Meanwhile,there were no significant differences(P≥0.05)in fatty acid profiles between the crude and refined oils,except for C16:0(P<0.01).Based on UPLC-Q E-MS/MS detection,137 TG molecules were identified in both crude and refined oils.Among the detected TG molecular species,64 contained EPA or DHA,which accounted for 46.83%and 46.00%of the total TG content in crude and refined oils,respectively.After refining,the content of the molecular species decreased by 31.95 mg/10 g,among which the three most variable molecular species were TG(16:0/18:1/22:6),(16:1/16:2/18:1),and(18:4/16:0/20:5),accounting for 29.26%of the decline of the molecular species.Overall,the refining process had little effect on the fatty acid profile and distribution of TG molecular species in fish oil.