Abstract
The study considered the influence of the hydrological cycle and gonadal development on the accumulation and use of energy in three fish species from an Amazonian flooded area. Fishes were sampled over a 24 hour period at monthly intervals between July 2004 and June 2005 using gillnets of different mesh sizes. Body cavity fat and gonadosomatic indices were determined, as well as energy content of gonads and muscles. Amongst the studied species, different means of energy allocation for reproduction were found: Acestrorhynchus falcirostris allocate energy from body cavity fat to its gonads; Pygocentrus nattereri uses mainly energy accumulated in the muscles for the process of gonadal maturation; and Hoplosternum littorale uses energy accumulated in their muscles and body cavity fat for reproductive processes. It is quite clear that the flood pulse regulates the gain and use of the energy reserves in fishes from the Amazonian floodplain.
Highlights
Patterns of energy allocation in fishes may change in accordance to the degree of sexual maturity of the individual, as timing of reproductive activity as well as maturation of the gonads require materials obtained from ingested food and energetic reserves deposited in various parts of the body (Tytler & Calow, 1985)
Such variations in energy allocation can lead to modifications of the physiological state of the fish, which can be detected by measuring biological parameters such as the index of body cavity fat, gonadosomatic index, and the energetic density of somatic and reproductive tissues
Individuals with immature (0.58% + 0.33) and ripe gonads (0.66% + 0.13) exhibited a lower amount of body cavity fat, while the highest values were found in individuals with spawned/recovering (1.99% + 0.12) and maturing gonads (1.66% + 0.19) (ANOVA, p < 0.01)
Summary
Patterns of energy allocation in fishes may change in accordance to the degree of sexual maturity of the individual, as timing of reproductive activity as well as maturation of the gonads require materials obtained from ingested food and energetic reserves deposited in various parts of the body (Tytler & Calow, 1985). Other studies have demonstrated that fish inhabiting areas with high seasonal variation in water level exhibit differences in the storage and allocation of energy reserves throughout the year (Carvalho, 1979; Junk, 1985; Finstad et al, 2003; Eggleton & Schramm, 2004; Dourado & Benedico-Cecílio, 2005). Such variations in energy allocation can lead to modifications of the physiological state of the fish, which can be detected by measuring biological parameters such as the index of body cavity fat, gonadosomatic index, and the energetic density of somatic and reproductive tissues. These estimates are useful for investigating the life history strategies
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