Invasive non-native species of fish in upper Paraná river Basin, Brazil: variations of caloric content in Cichla kelberi

Abstract

The allocation of assimilated energy may be influenced by seasonal changes, growth, and reproductive cycle of fish, food consumption and environmental conditions. The objective of this research was to evaluate the energetic variations of Cichla kelberi in the upper Paraná River floodplain, analyzing the caloric content in muscles, gonadosomatic index (GSI), and the condition factor between assessed systems, sex, and stage of gonadal maturation. The results obtained in the present study permit assuring that this is a species that efficiently converts the resources of the environment into energy. Although presenting higher condition factor in the environment where there is a greater ease in getting food (Paraná subsystem), the energy identified in the muscles was the same in both subsystems. During the process of gonadal maturation there is optimization in energy accumulation in the muscles of females, before and after reproductive period, and somatic growth occurs significantly when the individual is not reproducing. Further detailed studies on ecological mechanisms influencing the success of the species, as the presence of competitors and preference for native preys, are needed to implement effective management measures aimed at preventing that the species proliferation in the environment is even more damaging to local biodiversity.O balanço energético em espécies de peixes pode ser influenciado por variações sazonais no crescimento e ciclo reprodutivo, consumo de alimento e condições ambientais. O objetivo desta pesquisa foi o de avaliar as variações energéticas em uma espécie piscívora introduzida, Cichla kelberi, no alto rio Paraná, analisando as variações do teor calórico nos músculos, índice gonadossomático e o fator de condição entre subsistemas da planície de inundação, sexo e grau de maturação gonadal. Os resultados obtidos no presente estudo indicam que esta é uma espécie que converte eficientemente os recursos que obtém do ambiente. Embora apresentando maiores valores do fator de condição no ambiente onde foi registrada uma maior facilidade na obtenção de alimento (subsistema Paraná), o conteúdo energético identificado nos músculos da espécie foi o mesmo em ambos os subsistemas. Durante o processo de maturação gonadal verificou-se acúmulo de energia nos músculos de fêmeas, antes e após período reprodutivo, e crescimento somático ocorreu significativamente quando o indivíduo não estava se reproduzindo. Outros estudos, enfocando os mecanismos ecológicos que influenciam o sucesso das espécies, como a presença de competidores e a preferência por presas nativas, são necessários para implementar medidas destinadas a impedir uma maior proliferação da espécie no ambiente e que comprometa a biodiversidade local.

Difference in reproduction energy content in muscles on fish from reservoirs in Paraná State, Brazil

“…In the present study, significant intra-and interspecific differences in caloric densities were observed, showing that they should be considered when modeling energy flow. Espínola et al (2012) observed that the condition factor of Cichla kelberi was lower in Baía River than in Paraná River, suggesting the influence of the flow regulation by an upstream reservoir (Porto Primavera), with increased transparency due to the retention of fine particles in that reservoir. This process could be facilitating the capture of preys with better nutritional value (Abujanra et al, 2009).…”

“…Changes characteristics of the water (quantity and quality of food resources available to the fish) produced by flood pulses or the reservoirs may cause alterations in the welfare of the fish. These alterations can be quantified by the condition factor (Abujanra et al, 2009;Espínola et al, 2012). Variations in the condition factor (relationship between extrinsic and intrinsic variables and physiology of fish) and the caloric content of fish species have been used as indicators of physiological status and of changes in body composition (Encina & GranadoLorencio, 1997;Paul et al, 1998).…”

“…For freshwater environments, some studies have been developed in the upper Paraná River floodplain (Doria & Andrian, 1997;Penczak et al, 1999;Benedito-Cecilio & Morimoto, 2002;Vismara et al, 2004;Rezende et al, 2008;Garcia et al, 2010, Espínola et al, 2012. Espínola et al (2008Espínola et al ( , 2010 examined the variation of the energetic content for two species of the Manso Reservoir, but the analyses relating to the energetic quantification of fish species have not yet been conducted between dammed environments.…”

Body condition and energy density of juvenile streaked prochilod Prochilodus lineatus (Valenciennes, 1837) in a Neotropical floodplain

“…This balance results in a significant increase in condition factor, and thus the increase in energy density may not reflect in improved body condition through the condition factor (Enrich-Prast & Esteves, 2005;Espínola et al, 2012). The paramters of condition factor and energy density present different patterns of variation, suggesting that their values could indicate different physiological conditions.…”