Comparing on site human and video counts at Igarapava fish ladder, south eastern Brazil

Abstract

On site human observations and video images were collected and compared at the window of the Igarapava Dam fish ladder (IDFL), rio Grande , Southeastern Brazil, between March 1 st and June 30 th , 2004. We conducted four experiments with two humans (Observer 1 and Observer 2) observing fish passage in the IDFL window while a Sony 3CCD video camera (Observer 3) recorded fish passage at the same time. Experiments, each one hour in length, were distributed throughout the diel cycle using full spectrum lights. We identified fish species, the number of individuals for each species, and the real time that they passed. Counts from each human observer were compared to the video counts. The fish species most commonly observed in the window were -curimba (Prochilodus lineatus), mandi-amarelo (Pimelodus maculatus), piau-três-pintas (Leporinus friderici) and ferreirinha (Leporinus octofasciatus). The number of species and individuals were indistinguishable for the three observers. But, the number of species and individuals were significantly different among experiments. Thus, the three observers register the same number of species and count the same number of individuals even when these two response variables differ significantly among experiments. Based on these results, we concluded that the video count was an accurate method to assess fish passage at the IDFL.Observações in loco e vídeo filmagens foram coletadas na janela da escada de peixes da UHE Igarapava (EPUG), rio Grande, sudeste do Brasil, entre 1 o de março e 30 junho de 2004. Realizaram-se quatro experimentos com dois observadores humanos (Observador 1 e Observador 2) que observaram a passagem de peixes na janela da EPUG enquanto uma vídeo câmera Sony 3CCD (Observador 3) registrou simultaneamente a passagem de peixes. Os dois observadores humanos registraram in situ a passagem de peixes no visor da escada enquanto a câmera os filmava ao mesmo tempo. Os experimentos, cada um com uma hora de duração, foram realizados durante o ciclo diário, utilizando-se iluminação de espectro completo. Registraram-se as espécies, o número de indivíduos e o horário de passagem. Os registros de cada observador humano in situ foram comparados com os dos vídeos. Consideraram-se curimba (Prochilodus lineatus), mandi-amarelo (Pimelodus maculatus), piau-três-pintas (Leporinus friderici) e ferreirinha (Leporinus octofasciatus) como espécies alvo, tendo em vista sua alta freqüência de ocorrência na escada de peixes da UHE Igarapava. O número de espécies e o número de indivíduos não foram estatisticamente diferentes entre observadores. Por outro lado, o número de espécies e o número de indivíduos que passaram pelo visor foram estatisticamente diferentes entre experimentos. Assim, demonstrou-se que os três observadores registraram o mesmo número de espécies e contaram o mesmo número de indivíduos, mesmo quando as duas variáveis diferiram significativamente entre experimentos. Concluiu-se que o sistema de vídeo imagem constitui um método eficaz para avaliação da passagem de peixes na escada ...

Fish passages in South America: an overview of studied facilities and research effort

“…Regarding research questions (sensu Roscoe, Hinch, 2010), most studies addressed efficiency questions, i.e., issues related to fish passage, such as abundance and species composition within the fishway (e.g., Bowen et al, 2006;Makrakis et al, 2007a;, or the proportion of fish ascending and descending the facility (e.g., Agostinho et al, 2007d;Fernandez et al, 2007a;Makrakis et al, 2010). A smaller number addressed mechanism questions, which investigated how passage is affected by operation (e.g., Pompeu, Martinez, 2005), environmental variables (e.g., Fernandez et al, 2007b;Pereira-Assis et al, 2009a), and swimming ability (e.g., Santos et al, 2007;Assumpção et al, 2012;.…”

Reproductive activity and recruitment of the yellow-mandi Pimelodus maculatus (Teleostei: Pimelodidae) in the Igarapava Reservoir, Grande River, Southeast Brazil

“…The feasibility of using video technology for estimating and evaluating fish passage was successfully tested at IFL. Thus, it allows us to document and count fish-ladder passage (Bowen et al, 2006). This technology was used by Bizzotto (2006) who collected data in the period of June, 2003to May, 2004 She demonstrated that adult yellow-mandis ( 33.6% of the total number of fishes) is the most abundant species in the IFL.…”

Is fish passage technology saving fish resources in the lower La Plata River basin?

“…At the same dam, Capeleti and Petrere (2006) reported that P. lineatus was more attracted by adjacent impassable spillways than by the ladder itself indicating that even in low-head dams, hydraulic patterns can strongly affect passage efficiency. At Igarapava Dam, P. lineatus, P. maculatus, Leporinus friderici and L. octofasciatus were identified as primary species using the fish ladder (Bowen et al, 2006). The 10-m high, 75-m long fish ladder at Salto Morais Dam on the Tijuco River was highly selective with only about 2% of fish (15 species) in the tailrace able to reach the higher sections of the fish ladder (Godinho et al, 1991 elongatus.…”