Prey C:P ratio and phosphorus recycling by a planktivorous fish: Advantages in fish selection towards pelagic cladocerans.

MARIANA REISSIG,; CLAUDIA QUEIMALIÑOS,; B. MODENUTTI,; E. BALSEIRO,

ECOLOGY OF FRESHWATER FISH

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2015 vol. 24 p. 214 - 224

0906-6691

We examined prey preference of Galaxias maculatus as function of prey daily distribution. Likewise, we analysed prey elemental composition (C:P ratio)  to assess net phosphorus gain for fish metabolic investment. Fish phosphorus recycling was analysed in field experiments to evaluate nutrients supply depending on diet. Results revealed that C. dubia was a highly selected prey by all fish sizes at dawn and dusk, despite its low abundances in comparison with other zooplankters. Meanwhile, the littoral prey dominated only at sunset in gut contents. The high selection toward cladoceran coincided with the increase of their abundances at surface layers at night and dawn, and probably to the decrease of risk of G. maculatus of being preyed by piscivores. Analysis of elemental composition revealed that P content of C. dubia was significantly higher than other planktonic prey (Bosmina longirostris and Boeckella gracilipes). Phosphorus recycling experiments showed that G. maculatus would supply P in available forms for phytoplankton growth. Fish size was observed to influence P recycling since small fish had significant higher mass specific P release in the morning and midday when they preyed mainly upon C. dubia. Low prey C:P ratio appears as a factor that would add benefits to the classical visual fish selection towards cladocerans, since this preference would imply a net phosphorus gain for fish.