Search results for "Predation"

Diel feeding habits of juveniles of Mullus surmuletus (Linneo, 1758) in the lagoon of the Stagnone di Marsala (Western Sicily, Italy)

1999

Diet composition, feeding rhythm, gastric evacuation rate and daily ration were investigated in juvenile Mulhis surmuletus (Linneo, 1758). Fish were collected in the lagoon of the Stagnone di Marsala in western Sicily, in July 1995, during a 24 h sampling period. Copepoda, Polychaeta, Amphipoda and Tanaidacea were shown to be the most frequent prey items. The feeding index values showed two different daily feeding times. A unimodal trend in the daily rhythm of food consumption was derived, with a peak in feeding between 1200 and 2000 h. Gastric evacuation in juvenile M. surmuletus is best described by an exponential model, with a gastric evacuation rate R = 0.66 g h-1 (r = 0.88) (T = 24.45 …

Pinger affects fish catch efficiency and damage to bottom gill nets related to bottlenose dolphins

2009

There is some evidence that the presence of Tursiops truncatus in fishing areas represents a real economic threat to fishermen due the dolphin feeding on the entangled fish, damaging the nets and reducing the fish catch. We have carried out experiments to assess the efficiency of a pinger in decreasing the interaction between the dolphins and fishing nets, in a fishing area off the coast of southern Italy, where Tursiops truncatus is frequently observed to interact with bottom gill nets. Two identical monofilament bottom gill nets (900 m long), one equipped with pingers and the other without, were used to measure the effect of these pingers on the abundance of the catch and net damage. For …

Increased water temperature decreases predation rate of an important sea star predator on sea urchins.

2011

Cross-validation of δ15N and FishBase estimates of fish trophic position in a Mediterranean lagoon: The importance of the isotopic baseline

2013

Abstract FishBase, a relational database freely available on the Internet, is to date widely used as a source of quantitative information on the trophic position of marine fish species. Here, we compared FishBase estimates for an assemblage of 30 fish species sampled in a Mediterranean lagoon (Acquatina lagoon, SE Italy) with their trophic positions calculated using nitrogen stable isotopes. To assess the influence of the trophic level used to compute the baseline indicator on the robustness of isotopic estimations, we compared the trophic position of fish calculated using the average δ 15 N signature of either basal resource or primary consumer taxa measured at three stations located in th…

Food web reconstruction gives evidence of increased trophic levels in no-trawl areas: the red mullet, Mullus barbatus L. case in northern Sicily

2018

This study was aimed at identifying the food web of the red mullet, Mullus barbatus in order to understand how it is affected by trawling disturbance. To achieve this objective: a) the main features of the red mullet habitat were investigated; b) the food web of this habitat was studied in two no-trawl areas and in two areas open to trawling. The working hypothesis is that trawling affects the biochemistry of the sediment and the trophic structure of the benthic assemblage. It was predicted: a) less biomass, smaller size and higher production rate in the benthic assemblages of protected gulfs; b) higher average trophic level for both the red mullet and its predators in protected gulfs; c) a…

Fish-seastar facilitation leads to algal forest restoration on protected rocky reefs

2015

AbstractAlthough protected areas can lead to recovery of overharvested species, it is much less clear whether the return of certain predator species or a diversity of predator species can lead to re-establishment of important top-down forces that regulate whole ecosystems. Here we report that the algal recovery in a Mediterranean Marine Protected Area did not derive from the increase in the traditional strong predators, but rather from the establishment of a previously unknown interaction between the thermophilic fish Thalassoma pavo and the seastar Marthasterias glacialis. The interaction resulted in elevated predation rates on sea urchins responsible for algal overgrazing. Manipulative ex…

Crushing predation of the spiny star Marthasterias glacialis upon the sea urchin Paracentrotus lividus

2009

Literature data report that only fish predators are able to crush sea urchin tests in Mediterranean rocky reefs. This experimental study showed that the spiny star Marthasterias glacialis is able to break Paracentrotus lividus tests and that the breaking event is more likely to occur for small-sized sea urchins than for big ones. Our results show that the role of M. glacialis in regulating P. lividus population density can be important in specific locations. They may have important implications, moreover, for the use of tethering techniques aimed at identifying predator types of sea urchins.

Mimicry between unequally defended prey can be parasitic: evidence for quasi-Batesian mimicry

2010

The nature of signal mimicry between defended prey (known as Mullerian mimicry) is controversial. Some authors assert that it is always mutualistic and beneficial, whilst others speculate that less well defended prey may be parasitic and degrade the protection of their better defended co-mimics (quasi-Batesian mimicry). Using great tits (Parus major) as predators of artificial prey, we show that mimicry between unequally defended co-mimics is not mutualistic, and can be parasitic and quasi-Batesian. We presented a fixed abundance of a highly defended model and a moderately defended dimorphic (mimic and distinct non-mimetic) species, and varied the relative frequency of the two forms of the …

THE EFFECT OF ALTERNATIVE PREY ON THE DYNAMICS OF IMPERFECT BATESIAN AND MÜLLERIAN MIMICRIES

2004

Both Batesian and Müllerian mimicries are considered classical evidence of natural selection where predation pressure has, at times, created a striking similarity between unrelated prey species. Batesian mimicry, in which palatable mimics resemble unpalatable aposematic species, is parasitic and only beneficial to the mimics. By contrast, in classical Müllerian mimicry the cost of predators' avoidance learning is shared between similar unpalatable co-mimics, and therefore mimicry benefits all parties. Recent studies using mathematical modeling have questioned the dynamics of Müllerian mimicry, suggesting that fitness benefits should be calculated in a way similar to Batesian mimicry; that i…

Prey community structure affects how predators select for Müllerian mimicry

2012

Müllerian mimicry describes the close resemblance between aposematic prey species; it is thought to be beneficial because sharing a warning signal decreases the mortality caused by sampling by inexperienced predators learning to avoid the signal. It has been hypothesized that selection for mimicry is strongest in multi-species prey communities where predators are more prone to misidentify the prey than in simple communities. In this study, wild great tits ( Parus major ) foraged from either simple (few prey appearances) or complex (several prey appearances) artificial prey communities where a specific model prey was always present. Owing to slower learning, the model did suffer higher mort…