Browsing by Author "Morais, Pedro"
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- Behavioural lateralization and shoaling cohesion of fish larvae altered under ocean acidificationPublication . Lopes, Ana Filipa; Morais, Pedro; Pimentel, Marta S,; Rosa, Rui; Munday, Philip L.; Gonçalves, Emanuel João; Faria, Ana MargaridaRecent studies have shown that the behaviour and development of coral reef fish larvae is hampered by projected future CO2 levels. However, it is uncertain to what extent this effect also occurs in temperate species. The effects that elevated pCO2 (~2000 μatm) levels, which are expected to occur in coastal upwelling regions in the future, have on shoaling behaviour and lateralization (turning preference) of fish, were tested in temperate sand smelt Atherina presbyter larvae. The hypothesis that behavioural changes are caused by interference of high CO2 with GABA-A receptor function was tested by treating larvae with a receptor antagonist (gabazine). Routine swimming speed did not differ between control and high pCO2, but exposure to high pCO2 for 7 days affected group cohesion, which presented a more random distribution when compared to control fish. However, this random distribution was reversed after 21 days of exposure to high CO2 conditions. Lateralization at the individual level decreased in fish exposed to high pCO2 for 7 and 21 days, but gabazine reversed this decline. This adds to the growing body of evidence that the effects of a more acidified environment on fish larvae behaviour are likely due to altered function of GABA-A receptors. Overall, our results suggest that future pCO2 levels likely to occur in temperate coastal ecosystems could have an adverse effect on temperate larval fish behaviour.
- Benthic food webs support the production of sympatric flatfish larvae in estuarine nursery habitatPublication . Dias, Ester; Morais, Pedro; Faria, Ana Margarida; Antunes, Carlos; Hoffman, Joel C.Identifying nursery habitats is of paramount importance to define proper management and conservation strategies for flatfish species. Flatfish nursery studies usually report upon habitat occupation, but few attempted to quantify the importance of those habitats to larvae development. The reliance of two sympatric flatfish species larvae, the European flounder Platichthys flesus and the common sole Solea solea, on the estuarine food web (benthic versus pelagic), was determined through carbon and nitrogen stable isotope analysis. The organic matter sources supporting the production of P. flesus and S. solea larvae biomass originates chiefly in the benthic food web. However, these species have significantly different d13C and d15N values which suggest that they prey on organisms that use a different mixture of sources or assimilate different components from similar OM pools (or both).
- Ichthyoplankton dynamics in the Guadiana estuary and adjacent coastal area, South-East PortugalPublication . Faria, Ana Margarida; Morais, Pedro; Chícharo, Maria AlexandraThe species composition, abundance and distribution of the ichthyoplankton of the Guadiana estuary and adjacent coastal area were studied in relation to several environmental parameters. Sampling occurred during new moon Spring tides, at the ebb and flood, at nine stations, from March 2002 to February 2003. Temperature, salinity, dissolved inorganic macronutrients, seston and organic matter and chlorophyll a were determined at each station. A total of 22 and 34 fish eggs and larvae taxa were identified, respectively. The highest abundances were registered in the lower and middle part of the estuary, probably due to the presence of species that use the estuary as a preferential spawning ground, mainly Pomatoschistus spp. and Engraulis encrasicolus sensu lato. Temporal patterns of occurrence of ichthyoplankton allowed each species’ spawning season to be determined. Two taxa dominated the ichthyoplanktonic community during spring and summer (Pomatoschistus spp. and E. encrasicolus), whereas Sardina pilchardus was particularly abundant during autumn and winter. The forcing variables responsible for community structure were chlorophyll a and seston for eggs, while temperature, salinity and nitrite explained the larval component. Comparisons of the results with previous ichthyoplankton studies of the Guadiana estuary conducted before the Alqueva dam was built also indicate that river flow has an important impact on the distribution and abundance of ichthyoplankton in the estuary.