Reporting on the recapture of electronic tagged fish by fishers in the Xingu River, Brazilian Amazon

Radiotagging a long-distance migratory characid fish: reproduction after surgery, tag losses, and effects in weight

Abstract Although biotelemetry studies bring useful information, tagging is a highly invasive procedure. For this reason, we assess if intracoelomic tagging alters survivorship, weight gain and/or reproductive capacity of a neotropical migratory fish. In August 2016, 60 fish were equally and randomly distributed among 3 treatments: Control (anesthesia), sham surgery (anesthesia and surgery), and true surgery (anesthesia, surgery and tagging). Surveys for weight and tag expulsion were performed periodically from surgery through spawning (November/2016), with a final survey occurring in May/2017. Mortality was higher in true surgery (25% died) and for males. Twenty percent expelled tags, and initial weight loss followed by gain were verified for all treatments. Females of all treatments spawned, and fecundity and fertility were not different. Then, future studies should consider the losses due to death and tag expulsion when defining the sample number. We also encourage further investigations about differences in mortality between sex and weight variation, as well as any other factor that leads to increase in mortality. This is the first study that investigated tagging effects in reproduction of neotropical fishes, and since the methods and tags used are not species-specific, we infer that similar effects could occur in other species.

Biotelemetry reveals migratory behaviour of large catfish in the Xingu River, Eastern Amazon

We used a combination of radio and acoustic telemetry to assess the movements of large catfish (Pimelodidae) in the Xingu River, a clearwater tributary of the Amazon River in Brazil. A total of 121 Phractocephalus hemioliopterus and 61 Pseudoplatystoma punctifer were tagged for monitoring within a 685 km segment, including the Belo Monte Hydroelectric Complex (BMHC), between February 2013 and July 2015. Long distance upstream movements were detected for P. hemioliopterus (up to 347 km) and for P. punctifer (up to 164 km) mainly during the transition between dry season and the rising water period. Both species moved through a long segment of rapids previously thought to function as barriers to migration. Several individuals exhibited long-distance bidirectional movements. Some tagged fish never left the release zone, indicating mortality, tag loss or resident individuals, which would characterize partial migration. The findings show evidence of migratory behaviour for large catfish within the Xingu River, emphasizing the influence of the hydrologic cycle on their movements. As part of the study area has become partially dewatered due to the BMHC, findings support the need of adequate management strategies to allow the movements of large catfish between spawning and feeding sites in the Xingu River.

Population and reproductive parameters of the red-tailed catfish, Phractocephalus hemioliopterus (Pimelodidae: Siluriformes), from the Xingu River, Brazil

ABSTRACT A field study of the sex ratio, length-weight ratio, body size at first gonadal maturation, and the breeding season of the red-tailed catfish, Phractocephalus hemioliopterus, was carried out in the region of the middle Xingu River in the eastern Amazon basin. The fish were sampled quarterly from September 2012 to January 2014 using gillnets and long lines. The sex ratio was balanced, and while males and females were similar in standard length, the females were heavier than the males, on average. The males presented negative allometric growth, and the females, isometric growth. The estimated size at first maturity was 77.8 cm. The variation in the gonadosomatic index and the greater frequencies of mature specimens indicated a reproductive peak at the beginning of the high-water (flood) period. As P. hemioliopterus is an important commercial fish, our findings will contribute to the future development of effective conservation and management strategies, such as minimum catch size and a close season that is appropriate for the region. These data will also provide important insights for the evaluation of potential impacts on the biology of this fish resulting from the construction of Belo Monte dam.