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Abstract

Background: Several species of fish are commercialized in Brazil, among them many have the potential to use the leathers for making clothes, shoes, and others.Objective: This study aimed to carry out physicochemical and mechanical tests, as well as the morphological characterization of leathers from different fish species, Oreochromis niloticus, Arapaima gigas and Cynoscion virescens, as well as directions of the leather specimens and their correlations regarding quality and strength.Main Body: A total of 10 specimens were removed by treatment, in certain thicknesses, taken diagonally, longitudinally, and transversely from leather as a length function of the fish's body, to determine tensile strength and percentage of extraction (stretching) and progressive tearing using an EMIC dynamometer. The skins subjected to tanning process with chromium salts demonstrated thickness ranging 0.89 to 1.04 mm after tanning. The thickness of O. niloticus leather demonstrated significant differences in the regions, whose average value was 0.96 mm. However, when evaluating thickness of the leathers in relation to directions, longitudinal showed the greatest thickness 1.11 mm, transversal and diagonal directions showed no difference between them, whose average was 0.94 mm. The directions of removal of the specimens influenced tensile strength where longitudinal direction 15.12 N mm -2 demonstrated greater strength and diagonal 11.41 N mm -2 less strength. However, the progressive tear test behaved in an inverse way, where longitudinal direction showed lowest 46.79 N mm -1 strength and diagonal 63.89 N mm -1 higher strength. Transversal direction did not differ statistically between the other directions for two parameters evaluated. The traction of O. niloticus leather regions did not influence strength, however, the tearing variable demonstrated lower strength 49.65N mm -1 ) for tail region, while the head and central regions did not show significant difference between regions, whose average was 61.49 N mm -1 . When evaluating tensile strength of the leather, there were no significant differences, where an average value 13.46 N mm -1 was found depending on region, while for the direction of removal of the specimens, the average was 14.49 N mm -1 . The average value for longitudinal and transverse directions independent of the analyzed region was 130.13 and 117.43 N mm -1 , respectively. Tanning with vegetable tannin is recommended for the skins of the three fish studied. Leathers become high quality products, being the raw material for making various artifacts such as clothes and shoes. In addition, it is more environmentally friendly than conventional chemical tanning agents.