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Projeto de investigação
COMPORTAMENTO AGONÍSTICO NOS JUVENIS DE SARGO DIPLODUS SARGUS: EFEITO NO CRESCIMENTO
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Agonistic behaviour and shoal composition of juvenile Diplodus sargus : First field observations
Publication . Gonçalves, Ana R.; Silva, Matheus Augusto Farias da; Vendrell, Catarina L.; Almada, Vítor Carvalho
Behavioural observations of juvenile
Diplodus sargus in natural habitats were conducted to
test whether agonistic interactions occur in natural circumstances
and, if they do, in which context they happen.
The level of aggression and the shoals composition
were also compared between distinct natural habitats.
Behavioural observations were also conducted in captivity,
and the level of aggression was comparedwith the
level recorded in natural conditions to investigate which
factors may promote aggressive behaviours. The observations
were performed at two sites in the Atlantic
Portuguese shore: São Pedro do Estoril (38°41′N,
9°22′W) and Cabo Raso (38°42′N, 9°29′W) from early
July to late August 2010 and from late July to early
October 2011, respectively. In nature agonistic behaviours
do occur, with a higher frequency in pools than in
open areas. However, even the highest values observed
in nature are significantly lower than those reported for
captive conditions. Shoal composition also changed in
different habitats, with more members and aggregates
more compact in open areas.We suggested that the high
levels of aggression observed in captive groups may be
an artefact caused by very high densities in confined
spaces and eventually by the accumulation of chemicals
that are known to be released by stressed fish and can be
detected by other conspecifics. The confinement imposed
in captivity may also affect shoal composition
limiting the number of members and inter-individual
distances in each group.
Tidal variation in a rocky inter-tidal fish population : The case of white seabream Diplodus sargus juveniles
Publication . Gonçalves, Ana Sofia Ribeiro; Sousa, Liliana Carvalho; Coelho, Pedro Duarte; Almada, Vítor Carvalho
The rocky inter-tidal habitat is a harsh and fluctuating environment, subject tofrequent disturbances. Field observations of juvenile white seabream Diplodussargus in inter-tidal rocky habitats were conducted to analyse the spatial distri-bution and feeding activity of this species in relation to the tidal cycle. Thedepth at which fish were observed did not change in most tidal phases whilefeeding activity changed with tidal level, showing the occurrence of tidal migra-tions and that feeding may be limited by habitat availability in shallow watersand thus be dependent on tidal changes. The present results show the exploita-tion of available feeding areas in the rocky inter-tidal by juvenile white seab-ream, which corroborates the importance of these habitats for the firstdevelopmental stages of this fish species.
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Fundação para a Ciência e a Tecnologia
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Número da atribuição
SFRH/BD/42226/2007