Tambaqui Colossoma macropomum (CUVIER 1818) is a large Amazonian characid highly appreciated for its meat and therefore over explored by the fishing activity. For the last decades, tambaqui has been the first native fish produced by the Brazilian aquaculture industry. The Amazon Basin is characterized by the presence of acidic and basic waters with pH ranging from 4 to 7.2. In the wild, tambaqui migrates from alkaline white waters where it spawns, to regions of black and acidic water during the rainy season. During this migration, tambaqui swim through waters with different hydrogen potentials that could easily have some effect on its sexual determination process, which has not yet been identified. Hence, the present study aimed at unveiling the possible effect of a peculiar Amazonian environmental feature, pH, on the sex determination of tambaqui. For this, tambaqui larvae at 12 days (post hatch) were kept at pH 6.7, 7.5 (control) and 8.2 for 45 days (until they reached 4 cm of standard length), and then transferred to ponds to grow for sex identification by histology. Although the group treated with more acidic water showed a slight bias towards males, there was no significant difference in both treatments compared to the control group. Therefore, we concluded that the water pH does not influence the sex determination mechanism on C. macropomum.

Tambaqui巨大巨像（CUVIER 1818）是一种大型亚马孙酸，因其肉而广受赞誉，因此在钓鱼活动中倍受青睐。在过去的几十年中，tambaqui一直是巴西水产养殖业生产的第一批本地鱼类。亚马孙河流域的特点是存在pH为4至7.2的酸性和碱性水。在野外，tambaqui在雨季从产卵的碱性白水迁移到黑色和酸性水区域。在这种迁移过程中，tambaqui会在具有不同氢势的水域中游动，这很容易对其性决定过程产生某些影响，但尚未被发现。因此，本研究旨在揭示特有的亚马逊环境特征pH对tambaqui性别决定的可能影响。为了这，将第12天（孵化后）的丹巴基幼虫分别在pH 6.7、7.5（对照）和8.2下保持45天（直到它们达到标准长度的4 cm），然后转移到池塘中生长以便通过组织学鉴定性别。尽管用更多酸性水处理的组对男性略有偏见，但与对照组相比，两种处理均无显着差异。因此，我们得出结论，水的pH值不会影响性别决定机制。C.大花。