Seasonal changes in condition, nutrition, gonad maturation and energy content in barbel, Barbus sclateri, inhabiting a fluctuating river |
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Authors: | Lourdes Encina Carlos Granado-Lorencio |
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Institution: | (1) Aquatic Ecology Station P. Albert I of Monaco, Monaco Pavilion, I. Cartuja, E-41092 Sevilla, Spain |
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Abstract: | The objective of this study was to investigate the seasonal cycle of condition, nutrition and gonad development, as well as
the magnitude of seasonal variations in energy content of somatic and gonad tissues in juveniles, males and females of Sclater's
barbel, Barbus sclateri, from the upper Guadalete River (south Spain). The influence of reproductive cycle on somatic changes
was also investigated and discussed. Measurements of condition factor (K), somatic index (SI), gonadosomatic index (GSI) and
somatic and gonad energy content (J g-1 dw) were made in individual specimens taken from the Guadalete River monthly for 12 months. This freshwater ecosystem is
characterised by strong seasonal fluctuations in water and flow level, temperature and food supply. It was found that in general
juveniles, males and females of barbel exhibited a similar condition, nutrition and somatic energy cycle throughout the year,
with the highest values in spring and the lowest in summer. Depletion of K, SI and somatic energy storage from spring until
mid-summer seems to be associated with high metabolic demands during this period, and in adult fish also with spawning-related
activity. The gonad index and energy content of the gonad were the highest in April and the lowest in summer for both sexes.
Spawning took place during late spring – early summer, with fish quiescent by mid summer. The energy required for ovarian
development (3970 J g-1 dw) was greater than the one for testes development (2763 J g-1 dw). Data on gonad energy content indicated a period (March to April) of intense energy accumulation (64% males and 37% females)
which was related to the decline in the average somatic energy content in males and females. The somatic energy content was
linearly related to K and SI. In the same way, GSI correlated positively with gonad energy. Linear trends were found between
somatic parameters (K, SI and energy content) and gonad parameters (GSI and energy content).
This revised version was published online in July 2006 with corrections to the Cover Date. |
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Keywords: | energy storage life-history styles reproduction |
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