1,720,969 research outputs found
Diel feeding periodicity and daily ration of shelf break fish species
No full textThe evaluation of the daily ration and feeding periodicity in a Mediterranean demersal fish assemblage under natural conditions is presented. Data were obtained during four trawl surveys conducted on the shelf-edge of the central Mediterranean Sea. Recently, researchers have begun to consider this area an essential fish habitat due to its extremely high productivity and diversity. The species which typified the assemblage were the fish Macroramphosus scolapax, Lepidotrigla cavillone, Mullus barbatus, Serranus hepatus, Argentina sphyraena and Glossanodon leioglossus. Fish were collected at three hour intervals throughout four 24 h sampling periods representing annual seasons. The study was based on the analysis of catch data and stomach fullness per setting time. Results show significant variation of feeding periodicity among species within daytime. The amount of food consumed daily, calculated according to the Elliott & Persson model, is compared to the patterns reported in literature for Atlantic fish species with similar trophic habits. Higher values of daily consumption could be related to the reproductive period for most of the above mentioned species
Interpretazione di immagini sonar nella cartografia di Posidonia oceanica. Analisi e descrizione dei sonogrammi.
No full textIn this paper a series of characteristics of Posidonia meadows of the central Tyrrhenian Sea are described based on a detailed analysis of SSS sonograms and ROV images, The correct interpretation of SSS signals is fundamental to have detailed maps of Posidonia oceanica meadows and, in some cases, particular aspects of the meadows characteristics could create errors
Identification and characterization of nursery areas of red mullet Mullus barbatus in the Central Tyrrhenian Sea
Full text linkRed Mullet Mullus barbatus is an important target of fishing activities in the central Tyrrhenian Sea, so it is essential to identify its critical habitats in order to manage this resource efficiently. Our research specifically focused on the identification and characterization of nursery areas. The use of spatial interpolation techniques enabled us to identify five nurseries that were highly persistent through time. Moreover, the estimate of juvenile density confirmed the strong aggregation effect of these nursery grounds, as a great portion of young individuals were concentrated in a relatively small surface of the study area. The environmental characterization of these areas showed that juveniles were mainly distributed on bottoms with a relatively high percentage of sand (>70%; P <0.05). Shannon biodiversity index analysis indicated that the southern nurseries reached the highest values of habitat quality (P < 0.0001). Multivariate analysis showed that nursery grounds were divided into three main groups, and analysis of spatial dynamics showed that two different strategies characterized Red Mullet juveniles when density changes over time. In particular, in some areas young individuals selected habitats in a density-dependent way following the basin model scheme, while in other zones they selected habitats in a density-independent way according to the proportional density model. Results also showed that juveniles followed the proportional density model strategy into nursery areas with the highest Shannon biodiversity index values
La cartografia come strumento di analisi per i paesaggi marini. Le praterie di Posidonia oceanica: un caso di studio.
No full textIn this study the regression of a Posidonia oceanica meadow of central Tyrrhenian Sea is analyzed through a detailed study of actual and historic cartography. A seascape analysis was carried out on the current map to evaluate the habitat fragmentation. Moreover this approach enabled us to test the efficiency of a landscape study for the management of a coastal ecosystem
Food preferences and rhythms of feeding activity of two co-existing demersal fish, the longspine snipefish, Macroramphosus scolopax (Linnaeus, 1758), and the boarfish Capros aper (Linnaeus, 1758), on the Mediterranean deep shelf
No full textThe feeding behaviour of two potentially competing species, the longspine snipefish, Macroramphosus scolopax, and the boarfish Capros aper was examined. While both species are very abundant along the Mediterranean coast and are regularly caught by demersal trawlers, they are of no commercial value. The diets of boarfish and longspine snipefish were investigated from samples collected between January 2001 and May 2002. Variations in the diet with fish size and season, as well as diet overlap and diversity were explored. Mysid shrimps, amphipods and gastropods were the most important food items in the diet of longspine snipefish. During ontogenetic development, M. scolopax occupies different trophic levels: the diet shifts from being predominantly composed of mysids (Anchialina agilis, Lophogaster typicus, Erythrops sp., Leptomysis spp.) in the smaller longspine snipefish [6.5 cm TL). Crustacean decapods and copepods were the most important prey in the stomachs of boarfish. Mysids (Lo. typicus), euphausiids and nematodes were present in the larger individuals (>8 cm TL). A more generalist diet, still containing copepods, crustacean decapods, gastropods (Limacina retroversa) and a large variety of amphipods (e.g. Phtysica marina, Stenotoe bosphorana) and mysids (e.g. A. agilis, Leptomysis spp., Erythrops sp.), dominated the diet of C. aper between 2 and 8 cm TL. Diet overlap between longspine snipefish and boarfish was very low and the differences in stomach species diversity were explained by season and fish size
Observations on the reproductive cycle, age and growth of the salema, Sarpa salpa (Osteichthyes : Sparidae) along the western central coast of Italy
No full textThe sexual maturation and the growth of the salema, Sarpa salpa (Linnaeus, 1758), along the Italian Mediterranean coast (central Italy), were Studied in fish (n = 105) killed incidentally by underwater explosions during the construction of Civitavecchia harbour in 1999 and specimens collected with trammel nets (n = 339). This species is characterized by a protandric hermaphroditism and the sex change process Occurs between 24 and 31 cm TL corresponding to a wide range of ages (3-7 years). Size at maturity (L-50) was 19.5 cm, at which almost all the individuals were males. Two distinct spawning periods were observed: one in spring, from March to May, and the other in autumn, from the end of September to November. During the first year, compensatory growth Occurred in the individuals born in the two periods: An annual regular pattern of ring deposition was identified in the otoliths: the translucent ring was laid down during the winter months, while the opaque ring was formed during the Summer months. Back-calculated lengths at age were used to estimate the parameters of the Von Bertalanffy growth equation which were: L-infinity = 37.27 cm, K = 0.27 year(-1) and t(0) = -0.53 year. Salema showed isometric growth (b = 3.04; P = 0.84 t = 0.19)
Feeding behaviour and daily ration of the spotted flounder Citharus linguatula (Osteichthyes: Pleuronectiformes) in the central Tyrrhenian Sea
Full text linkSpotted flounder Citharus linguatula (Linnaeus, 1758) is one of the most abundant species within demersal fish assemblages next to the continental shelf (up to 200 m depth) of the Mediterranean Sea. In spite of the ecological importance of this species in the central Tyrrhenian Sea, many aspects of its biology (e.g. feeding behaviour) are poorly described. In order to analyze how feeding habits are related to the ontogenetic changes in this species, 2636 specimens (between 9 and 26 cm of total length TL) were collected from November 2000 to January 2002. During ontogenetic development spotted flounder occupied different trophic levels: diet shifted from mysids, predominantly in the smaller spotted flounder (19 cm TL). Before the transition to the icthyophagous phase, a more generalist foraging behaviour including decapods (Processa sp., Alpheus glaber), molluscs (Turitella sp.) and benthic fish (Lesuerigobius spp., Gobius niger,Callionymus spp.. Arnoglossus laterna) dominated the diet. Seasonal analysis of the diet showed an increase in the presence of mysids in summer and autumn, and of decapods in summer and spring. Teleosteans are present throughout the year without significant variations. Daily ration values, computed from the Eggers method, ranged from 1.57% to 2.83% wet body weight, showing a negative relationship between reproduction and daily consumption rate
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