Browsing by Author "Sousa, Liliana Carvalho"
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- Dominance and growth of Diplodus sargus (Pisces: Sparidae) in small captive groupsPublication . Gonçalves, Ana Sofia Ribeiro; Sousa, Liliana Carvalho; Almada, Vítor CarvalhoThe dominance hierarchies and the growth rate of the commercially important fish Diplodus sargus were assessed in this study. Specifically, we tested the hypothesis that, if stable dominance orders were established, dominant fish would grow faster and show better condition factors than losers at the end of the experiment. Eight groups of six individuals were followed for 6 weeks and, for each group, we measured the linearity of the hierarchies on a weekly basis, and the week to week stability of the hierarchical structures. These dominance structures were linear and stable from week to week. We found no significant correlation between the dominance index with either growth rate or final condition factor. Thus, in short time windows over few weeks, aggressive competition seems not to cause differences in growth, although effects at a longer term like those induced by stress cannot be ruled out.
- Tidal variation in a rocky inter-tidal fish population : The case of white seabream Diplodus sargus juvenilesPublication . Gonçalves, Ana Sofia Ribeiro; Sousa, Liliana Carvalho; Coelho, Pedro Duarte; Almada, Vítor CarvalhoThe 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.