4 resultados para temporal and spatial changes

em SAPIENTIA - Universidade do Algarve - Portugal


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Tese de Doutoramento, Ciências do Mar, da Terra e do Ambiente, Ramo: Ciências do Mar, Especialização em Ecologia Marinha, Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2016

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A relatively high proportion of harvested seafood is still wasted due to spoilage, particularly in developing countries, or because they are by-catches or have little economic value, seemingly related to inherent problems linked to unattractive color, flavor, texture, small size, and high-fat content. Thus, many fish and seafood species are still underutilized.

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Recreational shore angling in the Atlantic Ocean between Moledo and Aveiro (Portugal) was examined using roving creel surveys (March/September 2001). Cooperation was high (90% of 2310 anglers approached). At least 39 species of fish were caught at a rate of approximately 0.5 fish angler h(-1). An estimated 7319 kg of Dicentrarchus labrax (L.), with 45.6% below the minimum legal size, and 2040 kg of sea breams (genus Diplodus), correspond to 5.75% and 1.19% of the commercial landings in the same geographical area, respectively. The results shed light on a number of issues relevant to integrated coastal management, including temporal and spatial distribution of fishing effort, species caught, sizes of fish, catch rates, and factors influencing catches and angler satisfaction. Whilst the results suggest that the catches of sea breams and sea bass by day-time recreational shore angling in northern Portugal are small compared with commercial fishing, other recreational activities, such as boat fishing and spear-fishing, must be assessed.

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Fish fauna were collected in two different subtidal shallow sites, seagrass and sand, using a small beam trawl in the Ria Formosa lagoon (South Portugal). Samples were taken at low and high tides, during day and night, and in each season. Fish assemblages associated with each site were significantly different, with seagrass site supporting greater fish abundance and higher number of species than sand. These site-related differences in fish assemblages were stronger than any other factor studied. Both sites showed seasonal variations in their fish assemblages, mainly because of recruitment of marine juvenile migrants during spring and summer. No significant tidal or diel changes were observed in the fish assemblages of either site, but there was a significant site-tide interaction, with higher fish abundance in seagrass at low tide. In sand, tide effect was evident only for certain species, with resident species more abundant at high tide and marine species more abundant at low tide. Within the Ria Formosa coastal lagoon, ichthyofaunal composition and structure is mainly influenced by site followed by season. (c) 2005 Elsevier Ltd. All rights reserved.