Prey C:P ratio and phosphorus recycling by a planktivorous fish: advantages of fish selection towards pelagic cladocerans

Abstract

Prey selection by the small planktivore Galaxias maculatus and phosphorus gain depending on diet has been examined related to predator–prey daily distribution. Prey elemental composition (C:P ratio) was analysed as a factor of selectivity. Field experiments were carried out to evaluate the effect of prey on phosphorus recycling. Results revealed that the pelagic cladoceran Ceriodaphnia dubia was a highly selected prey by all fish sizes at dawn and dusk, despite its low abundances in comparison with other zooplankters, while the littoral were ingested only during day. The high selectivity for C. dubia showed that G. maculatus moved to pelagic zone during night to consume this prey but returned to littoral areas during day due to the increase in predation risk. Analysis of elemental composition revealed that P content of C. dubia was significantly higher than other planktonic or littoral prey (Bosmina longirostris, Boeckella gracilipes and chironomids). Phosphorus recycling experiments showed that G. maculatus would transport and supply P in available forms for primary producers. Fish size was observed to influence P recycling as YOY had significant higher mass-specific P release in the morning and mid-day 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, as this preference would imply a net phosphorus gain for fish.Fil: Reissig, Mariana. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Laboratorio de Fotobiologia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; ArgentinaFil: Queimaliños, Claudia Patricia. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Laboratorio de Fotobiologia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; ArgentinaFil: Modenutti, Beatriz Estela. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Laboratorio de Limnologia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; ArgentinaFil: Balseiro, Esteban Gabriel. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Laboratorio de Limnologia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; Argentin

Stable isotope analysis of trophic structure, energy flow and spatial variability in a large ultraoligotrophic lake in Northwest Patagonia

“…Meanwhile, adults also reflect a high consumption of pelagic prey enriched in 15 N relative to insect larvae and closer to P3. In this sense, Reissig et al (2015) observed a high selection of small puyen towards pelagic prey for all fish sizes during night in the neighboring Lake Moreno. These authors demonstrated that juveniles and adults of small puyen use low light "windows" as refuge from large visual predators as P. trucha and introduced salmonids to exploit high quality pelagic resources.…”

“…Due to their high mobility, fish function as a strong link between bentho-littoral and pelagic habitats by feeding on prey from both habitats (Schindler and Scheuerell, 2002;Vander Zanden and Vadeboncoeur, 2002;Barriga et al, 2012;Reissig et al, 2015). In Patagonian lakes, exotic salmonids, particularly rainbow trout, play a major role in habitat coupling through predation in both bentho-littoral and pelagic habitats (Juncos et al, 2013).…”

“…However, there has been little research on whole food-web structure and the role of fish in connecting habitats within this oligotrophic lake. In particular, two native fish, the galaxiids Galaxias platei and Galaxias maculatus, are also an important link between bentho-littoral and pelagic habitats (Barriga et al, 2012;Reissig et al, 2015). This occurs in two ways: Galaxias spp.…”

“…This occurs in two ways: Galaxias spp. are an important link between their lower trophic invertebrate prey in both pelagic and bentho-littoral habitats and their piscivorous predators (Rechenq et al, 2011;Milano et al, 2013;Reissig et al, 2015), and Galaxias spp. will undergo ontogenetic migration from pelagic juvenile stages to bentho-littoral and deep-benthic adult stages, therefore connecting the two habitats through their lifecycle stages (Barriga et al, 2002).…”

Plankton crustaceans in bays with different trophic status in Llanquihue lake (41° S Chile)

“…In unpolluted conditions the calanoids copepods would have an important role as grazer on phytoplankton and in turn would be eaten by zooplanktivorous fishes in Argentinean and Chilean Patagonian lakes (Soto and Zuñiga, 1991;De los Rios-Escalante, 2010;Reissig et al, 2015;Trochine et al, 2015). Additionally, the natural ultraviolet radiation exposure that increased in Patagonia affect zooplankton assemblages because the species have different tolerance to UV radiation under trophic gradient (Marinone et al, 2006;De los Ríos-Escalante, 2010;Hylander et al, 2012).…”