The effects of Aphanius iberus predation on an aquatic community: diel changes and the role of vegetation

Abstract

The predation effects of a cyprinodontid fish (Aphanius iberus) on the aquatic invertebrate community structure of a Mediterranean shallow system with vegetation were investigated. Field studies were performed in March and July of 2009 in a pond adjacent to the salterns of San Pedro del Pinatar (Murcia, Spain) to evaluate two distinct settings of A. iberus population dynamics. In March, the A. iberus population had a low density, mainly dominated by large fish, whereas in July, the population had a higher density, mainly dominated by small, young-ofthe-year fish. To analyse the fish, vegetation and possible diel effects on the invertebrate community, we compared the aquatic invertebrate body size distribution (biomass size spectra) found under the following conditions: 1) during different seasons with different fish population structures to include possible ontogenic shifts, 2) in vegetated and non-vegetated areas to include sites with different resource availability, and 3) under day and night conditions to investigate possible diel cycles. We hypothesise that 1) because the main predator (A. iberus) has a high preference for vegetated areas and is expected to show a reduced mobility out of these areas, no diel differences in the aquatic invertebrate community structure would be apparent; 2) differences in the aquatic invertebrate size spectra would be found when comparing the non-vegetated area to the vegetated area (an area with higher resource availability but also higher predation pressure); and 3) differences in the aquatic invertebrate size spectra would be apparent when comparing different seasons due to an ontogenic shift in the A. iberus diet. Our results showed that in the vegetated areas, where fish were much more abundant, the assemblages of aquatic invertebrates had a characteristic size spectrum, showing a higher size diversity and a higher total biomass than the assemblages observed in the non-vegetated areas. Moreover, the observed differences were not affected by diel changes because none of the analysed parameters showed significant differences between the day and night samplings.

Assessing Benthic Macroinvertebrates in Relations to Environmental Variables and Revitalisation Works

“…Macrophytes can influence invertebrate distribution and abundance by affecting food availability [15] and predation due to refuge provisioning [16]. It is also known that the decreased abundance of macroinvertebrates and their taxa richness decline may be related to both natural and anthropogenic factors, such as seasonal effects, site-specific physical characteristics [17] and severe pollution [18,19].…”

Contribution to the knowledge of the distribution of Chaoborus species (Diptera: Chaoboridae) in the NE Iberian Peninsula, with notes on the spatial and temporal segregation among them

“…larvae typically inhabit open waters (Saether, 1972) they are sometimes associated with other mesohabitats, such as emergent or floating-leaved plants (Smiley & Tessier, 1998;Iglesias et al, 2007), where they can avoid visual predators (Folsom & Collins, 1984;Burks et al, 2001). It is well known that aquatic vegetation influences the structure of macroinvertebrate communities, not only by providing food resources (e.g., Burdett & Watts, 2009) but also by offering physical refuge from predation (e.g., Hampton & Duggan, 2003;Paukert & Willis, 2003;Gascón et al, 2013). Although we cannot rule out the possibility that chaoborids were performing diel vertical migration using sediment as a refuge, as has been documented (Bass & Sweet, 1984;Gosselin & Hare, 2003), our study suggests that in shallow water bodies, vegetation structure may play an important role as a refuge for chaoborid larvae.…”