Influence of life history and seasonal hydrology on lipid storage in three neotropical fish species
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abstract
The seasonal dynamics of energy (lipid) storage in three neotropical fish species with differing life histories were evaluated. Lipid content was substantially greater in the liver than in dorsal musculature of all three species. Two piscivores (Cichla temensis and Serrasalmus manueli) showed large, statistically significant seasonal fluctuations in liver lipid content. Liver lipid content increased during high water, through the falling water, and into the early dry season for both piscivores. Seasonal variation in dorsal muscle lipid content was large and statistically significant for C. temensis, but was small and nonsignificant for S. manueli. Cichla temensis appeared to finance costs associated with reproduction by accumulating lipids during the fallingwater period when migratory prey allowed the species to subsidize their energetic dynamics. Semaprochilodus kneri, a migratory algivore and detritivore, showed no significant seasonal variation in dorsal muscle lipid content and minimally significant seasonal variation in liver lipid content. Statistically significant effects of lipid content on 13C was observed when tissue lipid content varied by >12%, while biological interpretation of food web statistics based on 13C values appears robust to minor variations in lipid content. Nonetheless, when lipid content varied by larger amounts (e.g. >35% for C. temensis and S. manueli liver tissue) lipids appeared to have a large potential effect on 13C and food web statistics calculated from such measurements may have been biased. Surprisingly, even large variation in tissue lipid content did not affect 15N.
