Browsing by Author "Beldade, Ricardo"
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- An interference visual census technique applied to cryptobenthic fish assemblagesPublication . Beldade, Ricardo; Gonçalves, Emanuel JoãoWe compare the accuracy of an interference visual census technique (IVC), in which dismantling of the habitat is performed, to traditional underwater visual census (VC) and anaesthetic census. We compare the performance of these techniques applied to a temperate cryptobenthic fish assemblage using two strategies: sampling over the whole depth extent of the rocky bottom, and stratified sampling over the main microhabitats present at the study site. T h e number of species encountered was lower using the traditional VC. Fish density estimates were significantly higher using the interference technique compared to the traditional VC, in the transect strategy. These differences were larger for clingfishes and some gobies which occurred preferably under cobble and small rocks. No differences were found when comparing the IVC and anaesthetic census in the habitat strategy, for each microhabitat considered. We conclude that dismantling the habitat increases the performance of the visual census technique and is therefore a valuable approach when applied to temperate cryptobenthic fish assemblages.
- Composition and temporal dynamics of a temperate rocky cryptobenthic fish assemblagePublication . Beldade, Ricardo; Erzini, Karim; Gonçalves, Emanuel JoãoTemporal variation in a temperate cryptobenthic ¢sh assemblage at the Arra¤bida Marine Park (Portugal) was assessed by visual surveys during 2002 and 2003. A total of 9596 ¢sh from 11 families and 30 species was recorded. There were no changes in structure or density at the assemblage level between years, whereas diversity changed signi¢cantly due to a higher number of abundant species in the second year. A similar seasonal trend was found between years, with a signi¢cant overall density increase in autumn. This is partially explained by the arrival of new recruits of some of the most abundant species in the assemblage. Assemblage diversity and structure also changed across seasons. A group of species encompassing Gobius xanthocephalus,Tripterygion delaisi, Parablennius pilicornis, Gobius paganellus, Lepadogaster candollii and Lepadogaster spp. were analysed in detail. The temporal patterns of two of the most abundant species, G. xanthocephalus and T. delaisi, mimicked the overall temporal patterns of the assemblage.We suggest that the inter-annual stability in density of this subtidal ¢sh assemblage may be similar to what has been reported for the intertidal and that strong post-settlement processes are probably shaping this assemblage.
- Depth distribution of nearshore temperate fish larval assemblages near rocky substratesPublication . Beldade, Ricardo; Borges, Rita Alexandra; Gonçalves, Emanuel JoãoIn this study, we compare the composition, abundance and structure of a temperate fish larval assemblage at different depth intervals (0–4, 4–8 and 8–12 m) in the extreme nearshore environment. We used a plankton net attached to an underwater scooter to sample in close proximity to the rocky substrate (<50 cm). A total of 868 larvae from 27 taxa in 13 families were caught. The majority of larvae belonged to benthic reef-associated species (Blenniidae, Gobiidae, Gobiesocidae and Tripterygiidae), the four most abundant comprising 76% of the total larvae caught. A non-metric multidimensional scaling analysis (MDS) showed that there was a single multispecific larval patch near the substrate in the extreme nearshore up to 12 m depth. Nonetheless, distinct larval abundances were found in this relatively small depth range, with the majority of species being more abundant at the deepest interval, particularly Pomatoschistus pictus and Gobius xanthocephalus. Tripterygion delaisi was an exception being more abundant at the shallowest depth as young larvae. The density of pre-flexion larvae was not significantly different across depth intervals, but post-flexion larval density increased with depth. The full size range (from hatching to settlement) of P. pictus was present at the extreme nearshore. The innovative sampling technique used here revealed high densities of larvae close to the bottom, and depth was found to be an important factor influencing the distribution of several taxa and ontogenetic stages. The nearshore component of coastal fish larval assemblages near rocky substrates has been poorly studied, and our results suggest that the high densities of larvae found to aggregate in these environments must be taken into account when studying distribution and functional aspects of these assemblages.
- First record of Chromogobius britoi (Teleostei: Gobiidae) on the mainland European coastPublication . Beldade, Ricardo; Van Tassel, James L.; Gonçalves, Emanuel JoãoChromogobius britoi is a recently described and poorly studied goby currently known only from the Macaronesian islands of Madeira and the Canarian archipelago. This species was captured for the first time on the Atlantic mainland coast of Europe (at Arra´ bida Marine Park, Portugal). The habitat, depth preferences and morphological characters of the species are revised.
- Opeatogenys gracilis (Pisces: Gobiesocidae): An overlooked species or another ‘Mediterranean endemism’ found in Atlantic waters?Publication . Gonçalves, Emanuel João; Beldade, Ricardo; Henriques, MiguelThe occurrence of Opeatogenys gracilis outside the Mediterranean Sea is confirmed for the first time. This is probably a more common species than previously thought, but its apparent complete dependence on seagrass beds suggests the possibility of including it in the IUCN threatened species list. Some sex differences are described and a complete meristic and morphometric description of the species is presented. The occurrence of the species in the north-east Atlantic indicates that it might be a recent dispersal from the Mediterranean Sea, or an overlooked part of the autochthonous fauna.
- Pelagic larval duration of 10 temperate cryptobenthic fishesPublication . Beldade, Ricardo; Pedro, T.; Gonçalves, Emanuel JoãoThe pelagic larval duration (DPL) for 10 temperate cryptobenthic species belonging to three families: Gobiidae, Gobiesocidae and Blenniidae was investigated. Overall, the Gobiesocidae presented short DPLs varying between 11 and 18 days, the Gobiidae’s DPL ranged between 14 and 39 days, and Parablennius pilicornis (Blenniidae) had an average of 33 days (range 31–37 days). Two subtypes of settlement marks were found among individuals of the same species.
- Vertical structure of very nearshore larval fish assemblages in a temperate rocky coastPublication . Borges, Rita Alexandra; Beldade, Ricardo; Gonçalves, Emanuel JoãoSmall-scale vertical patterns of larval distribution were studied at a very nearshore larval Wsh assemblage, during the spring–summer period of several years, at two depth strata (surface and bottom) using sub-surface and bottom trawls. A total of 4,589 larvae (2,016 from surface samples and 2,573 from bottom samples) belonging to 62 taxa included in 22 families were collected. Most larvae belonged to coastal species. Although inter-annual variations in larval density and diversity could be found, total larval abundance was always higher near the bottom whereas diversity was higher at the surface. A marked distinction between the structure of surface and bottom assemblages was found. Sixteen taxa explained 95% of the similarity among surface samples. Larvae which contributed most to this similarity included species like clupeiformes, sparids and serranids, and also blenniids, tripterygiids and some labrids. In the bottom samples, fewer species were present, with only six taxa, almost exclusively from species which lay demersal eggs, contributing to 95% of the similarity between samples. Larvae present at the surface were signiWcantly smaller than at the bottom. For some of the most abundant species found at the bottom, only small larvae occurred at the surface while the whole range of sizes was present at the bottom, indicating that larvae may be completing the entire pelagic phase near the adults’ habitat. These results indicate that larval retention near the reefs probably occurs for these species, although for others dispersal seems to be the prevailing mechanism.