The fluorescent introduction has begun in the southern hemisphere: presence and life-history strategies of the transgenic zebrafish Danio rerio (Cypriniformes: Danionidae) in Brazil

Transgenic ornamental fish that fluoresce are becoming popular in the aquarium trade worldwide. Some transgenic zebrafish (TZF) records in natural water bodies have been published, but there are no data on their biological attributes in the new areas. This study aimed to evaluate the distribution, trophic ecology, and reproductive condition of the non-native TZF in headwater creeks located in the largest Brazilian ornamental aquaculture center. Insect fragments – identified as chitinous material in the 'false stomach'- and aquatic insects were the most consumed item. TZF adults were found in breeding conditions during almost all sampling periods. The Gonadosomatic Index of females and males showed peaks during the rainy season and matched with the rising water levels. Breeding females and males were found at small body sizes, indicating early maturation, and these transgenic females produced a moderate amount of small oocytes. Sex-ratio assessment showed that females and males had the same frequencies in one site, while females were significantly more frequent than males at another location. Management recommendations, such as utilization of best management practices (e.g. screens on outlets), not using unapproved genetically modified organisms in aquaculture, and awareness with fish farmers about transgenic animals, are suggested to avoid new introductions.