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- Feeding habits of the lizardfish Synodus saurus (Linnaeus, 1758) (Actinopterygii: Synodontidae), from the AzoresPublication . Barreiros, João P.; Sousa, Luis; Soares, Marta S. C.The feeding habits of the lizardfish Synodus saurus were study in the Azores archipelago, north-eastern Atlantic. Factors examined were diet composition, prey importance, season, fish size, feeding strategy and prey orientation in the oesophagus. The stomach contents of 308 specimens were collected and analyzed between March and November 2000. Synodus saurus is common in Azorean water. Though it prefers small gregarious pelagic fish, it also feeds on epibenthic and benthic prey. We found the following prey in its diet: 9 families of teleostean fishes (Carangidae, clupeidae, Cynoglossidae, Gobiidae, Labridae, Myctophidae, Spaidae, Spyraenidae and Synodontidae), two families of crustaceans (Cymothoidae and Scyllaridae) and one of cephalopods (Loliginidae). The European pilchard, Sardina pilchardus was the commonest prey. The diet of the lizardfish varies with the season, showing the greatest diversity (given by the Shannon-Wiener index) in October. There is a significant correlation with the sea temperature. The size of the predator is not correlated to the size of its prey. However, we observed a positive correlation between the size o the positive correlation between the size of the predator and the quantity of food in its stomach. The orientation of the prey in the oesophagus may partly depend on the predator’s size. However, analysis of the stomach contents provided no information on the selection of prey.
- Habitat use by the juvenile dusky grouper Epinephelus marginatus and its relative abundance, in Santa Catarina, BrazilPublication . Machado, Leonardo F.; Bertoncini, Áthila A.; Hostim-Silva, Maurício; Barreiros, João P.The dusky grouper (Epinephelus marginatus) is a species whose stock management deserves special attention. It has an important role in hard-bottom ecosystems and, as a protogynous hermaphrodite; it is especially susceptible to overfishing. Data on the species’ use of habitat, and on the way environmental and behaviour parameters influence its abundance can help to improve management and conservation strategies. The aim of this study was to evaluate the influence of bottom type, temperature and species behaviour on the abundance of E. marginatus, using a quadrate for visual census. An area of 80 mq., divided between rocky shore, rocky outcrop and sandy habitats was surveyed monthly. Densities of juveniles were: 1.16 groupers mˉ² over the rocky shore and 1.47 groupers mˉ² over the rocky outcrop, while no groupers were found over sand. Analysis of the yearly variation in abundance revealed a migratory pattern of dispersal and gathering. All size groups observed in this study were below the first maturation length.
- A typing error in Tokeshi's test of bimodalityPublication . Barreto, S.; Borges, Paulo A. V.; Guo, Q.“One way to describe patterns of species distribution is to plot the frequency histograms using species–range-size data (Gaston, 1994; Brown, 1995; Gaston & Blackburn, 2000). Usually the untransformed geographical ranges of species are distributed following a ‘hollow curve’, i.e. most species have narrow ranges and very few have widespread distributions. This highly ‘right-skewed’ curve has been regarded as unimodal (e.g. Gaston, 1994). In some cases, however, the species-range-size distribution shows a bimodal pattern (Hanski, 1982; Brown, 1984, 1995; Gaston, 1994; Gaston & Blackburn, 2000), in which to the left-hand mode is added a right hand mode generated by the widespread group of species that occur in almost all sampled sites. The ‘core-satellite species hypothesis’ (Hanski, 1982) and the ‘resource usage model’ (Brown, 1984, 1995) were proposed to explain the finding that a few species are regionally common (widespread) and locally abundant (the ‘core’ species in Hanski’s model; the generalists or broad-niched species in Brown’s model), while most species can be regarded as having smaller ranges and low local abundances (the ‘satellite’ species in Hanski’s model; the specialists or narrow-niched species in Brown’s model). […]”
- Preliminary notes on the reproductive biology of the lizardfish, Synodus saurus (Actynopterygii: Synodontidae) in the AzoresPublication . Sousa, Luis; Barreiros, João P.; Soares, Marta S. C.; Hostim-Silva, Maurício; Santos, Ricardo S.Between March and November 2000, 307 specimens of the lizardfish Synodus saurus (Linnaeus 1758) were captured on several coastal areas of Terceira Island, Azores. This species is an important coastal epibenthic predator. Although common, its biology, namely its reproduction, is virtually unknown. During the study period, 206 females (155 mm to 460 mm TL) and 101 males (269 mm to 290 mm TL), were captured. Sex ratio was 2:1 with more males in June. Gonados-somatic Index (GSI) for females and males attained its maximum values during Spring and Summer, showing that these are the most intensive reproduction periods. Hepato-somatic Index (HSI) suggests that this species may well recur on body reserves for energy metabolization in gonad development. Nevertheless, more studies are necessary in order to confirm this assumption. Ovarian histology, presenting different oocytarian phases, indicates that this species has an asynchronous posture. The male increment of June, associated to higher GSI values, suggests that this could represent a moment of intense competition for females, within the studied area.
- Interannual changes in the diet of the almaco jack Seriola rivoliana (Perciformes: Carangidae) from the AzoresPublication . Barreiros, João P.; Morato, Telmo; Santos, Ricardo S.; Borba, Alfredo Emílio Silveira deThe food habits of 232 almaco jack (Seriola rivoliana) were investigated in the Azores (NE Atlantic) between 1997 and 2000. Fish length ranged from 23 to 134 cm (SL), and 83.2% or the stomachs contained food. Their diet was exclusively piscivorous and dominant prey were juveniles or Trachurus picturatus (1997 to 1998) and Scomber japonicus (1999 to 2000). An apparent decrease of T. picturatus stock is interpreted as the main cause for the detected diet shift.