Planktivory in non-indigenous fish and implications for trophic interactions in a Mediterranean shallow lake

Abstract

-Similar to other Mediterranean lakes, Lake Vela displays a marked dominance of alien species, but the impact of such an assemblage on the lower trophic levels of shallow eutrophic lakes has been overlooked. In this study, zooplanktivory in the omnivorous fish assemblage of Lake Vela was examined from April to October 2003 (and also in January 2004. During this period, ichthyocenosis was characterized by abundance of juvenile fish, which strongly depended on zooplankton. Adult mosquitofish (Gambusia holbrooki) and pumpkinseed (Lepomis gibbosus) foraged on the same zooplanktonic prey than juveniles, although planktivory was less important in larger fish. Using multivariate analysis, it was possible to attribute most of the variability in planktivory to resource availability, as both fish foraged on the most abundant prey in each month. Albeit this opportunistic behaviour, mosquitofish was found to be positively selective towards small-sized littoral cladocerans, while pumpkinseed displayed positive selection towards Alona and Daphnia. In the absence of more efficient planktivores, pumpkinseed is now the main planktivore in Lake Vela and the main predator of Daphnia. However, due to low densities of Daphnia during most of the study period, Daphnia was virtually absent from the diet of pumpkinseed from June to October, a period during which this benthi-planktivore foraged chiefly on less-rewarding planktonic prey (small-sized cladocerans and cyclopoid copepods). Mosquitofish was an important planktivore in littoral and structured habitats. Flexible foraging behaviour partly explains the success of these two species in Lake Vela.

Invasive Asian clam distribution pattern reveals minimal constraints to downstream dispersal and imperceptible ecological impacts

“…Manual forward selection of environmental variables was used to reduce the environmental dataset to non‐redundant and significant variables (Monte Carlo permutation tests, P ≤ 0.05). Applying the variation partitioning technique described by Borcard, Legendre, & Drapeau (), CCA and partial CCA allowed the amount of variation of the macroinvertebrate dataset to be ascribed to the environmental matrix or to the clam matrix (see other examples in Castro & Gonçalves, ; Vidal et al, ). These procedures could clarify whether clams might explain some variation in the macroinvertebrate communities, after removing (i.e.…”

Effects of anticholinesterase drugs on biomarkers and behavior of pumpkinseed, Lepomis gibbosus (Linnaeus, 1758)

“…Consequently, it is licit to suggest that an additional effort must be made to fully characterize its ecotoxicity. Pumpkinseed is an invasive species in Europe and is presently becoming one of the most relevant planktivores/omnivores in many Mediterranean lakes and reservoirs, displacing the indigenous cyprinid community (see Castro and Gonc ¸alves, 15 and references therein). Rodrigues et al 16 refer a series of criteria required for a suitable test organism, and discuss the advantages of using pumpkinseed as a model organism in ecotoxicological studies.…”

“…Fishes were captured in Lake Vela, located in the Portuguese littoral-centre, which is a temperate shallow lake exhibiting a eutrophic status (for more information, see Castro and Gonc ¸alves 15 ). Fishes were captured using a seine net (variable mesh size, 1-2 cm), which was deployed in a semi-circle and then pulled to the shore.…”

Effects of Aquatic Macrophytes on Spatial Distribution and Feeding Habits of Exotic Fish Species Lepomis macrochirus and Micropterus salmoides in Shallow Reservoirs in South Korea

“…These pelagic species are preferred by consumers because they are easily pursued and captured by fish predators [49]. However, species such as Alona and Chydorus spp., which attach to the stems and leaves of macrophytes, are not as easily consumed by fish [50]. When easy-to-exploit resources such as planktonic species are exhausted, epiphytic species can be used as alternative food sources for secondary consumers [51].…”