Feeding strategies ofAtherina boyeri(Risso 1810) in a freshwater ecosystem

Abstract

Summary This study investigates the adaptation of certain feeding strategies by a population of Atherina boyeri inhabiting a freshwater ecosystem (Lake Trichonis, Greece) and links feeding habits with ecosystem interactions, using stomach content analysis and food availability. The use of Ivlev's electivity index (E) revealed the selection of different prey categories in respect to size, species and even gender. A. boyeri showed positive selection for larger zooplankters such as adult copepods and the egg‐bearing females of Eudiaptomus drieschi (0.53 < E < 0.92 and 0.24 < E < 0.99, respectively) or the cladocerans Diaphanosoma orghidani and Daphnia cucullata (0.25 < E < 0.53 and 0.23 < E < 0.37, respectively) in spring and/or summer. In contrast, the fish totally avoided rotifers and copepod nauplii, while showing negative selection for smaller prey items like copepodites (−1.00 < E < −0.14). A shift to larger prey was recorded as age increased. Larger specimens showed cannibalistic behaviour by consuming larvae of A. boyeri and the endemic, threatened, fish Economidichthys trichonis. The results provide certain indications that, through selective predation, A. boyeri is able to affect zooplankton abundance and community composition, the vertical distribution and migration of crustaceans and the abundance of other fish species, However, more research on the dynamics and feeding ecology of A. boyeri and other fish species is necessary.

Fish predation in the proximity of purse seine fishing lights: The case of Atherina boyeri (Actinopterygii: Atheriniformes: Atherinidae) in a Greek Lake

“…On the other hand, no copepod nauplii were found in the diet of A. boyeri in the two previous studies. The larvae of the bivalve Dreissena blanci were the most important prey of A. boyeri in Lake Trichonis, as it was also reported by Chrisafi et al (2007), although Doulka et al (2013) found this taxon second in abundance. It should be noted, that according to recent investigations (Chalkia et al 2012), Dreissena blanci had been misidentified as Dreissena polymorpha in both of these previous reports.…”

“…Also the cladocerans Alona sp. and Leptodora kindtii were not found, in contrast to Doulka et al (2013). On the other hand, no copepod nauplii were found in the diet of A. boyeri in the two previous studies.…”

“…One of the aims of this study was to investigate the feeding of Atherina boyeri in the proximity of purse seine artificial lights in Lake Trichonis and to compare its diet with two previous studies (Chrisafi et al 2007, Doulka et al 2013 in which the samples have been taken without the use of light. It must be pointed out, though, that direct comparisons are difficult to be made since both of the two previous studies have been conducted in monthly intervals for a full year, while the presently reported study for only seven months coinciding with the period of the main fishing activity with the use of light in Lake Trichonis.…”

“…Two previous studies on the diet and feeding strategy of A. boyeri in Lake Trichonis (Chrisafi et al 2007, Doulka et al 2013) revealed that it is a strictly zooplanktivorous species that acts as a visual predator and feeds not only according to the abundance of prey, but also selects prey categories in respect to size, species and even gender (Doulka et al 2013). It must be pointed out, however, that these studies have been conducted in specimens from samples taken without the use of light, and thus, there are no indications of how the presence of light can differentiate the feeding habits of this species.…”

“…In addition, Doulka et al (2013) showed that A. boyeri is capable of preying upon the larvae of the endangered fish, Economidichthys trichonis Economidis et Miller, 1990, for which field experiments have revealed intense positive phototactic behaviour (Kehayias, unpublished data). Therefore, it is highly probable that the larvae of this endangered species approach the purse seine lamp rafts deployed at night and suffer heavy predation by A. boyeri when the latter aggregates around the light (Kehayias et al 2015).…”