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How to sample larval fish for taxonomical and ecophysiological studies in shallower temperate coastal ecosystems?

Publication . Chícharo, Luís; Faria, Ana Margarida da Silva; Morais, P.; Araújo Amaral, Ana Margarida; Mendes, Carlos; Chicharo, Maria Alexandra Teodosio

Recruitment predictions for fish are often difficult to make due to the intrinsic variability of species and the incomplete sampling procedures. The aim of this study was to analyse the fish larval catches (abundance, diversity, size and damage) from a standard 500 mm ichthyoplankton net and different light traps (structure, size and light intensity) in temperate coastal turbid waters. Catches from different gear were always made on the same date or season, same location and same tidal phase. Results showed that light traps captured significantly bigger larvae (almost post-flexion) than those captured with the ichthyoplankton net, nevertheless the diversity was lower. Clupeidae species were the most represented taxon; nevertheless, the traps also caught Atherinidae, Gobiidae, Sparidae, Soleidae and Labridae. The light traps were less stressful devices, allowing the capture of live and active larvae. This showed other possible uses for the light trap, e.g. larval behavioural and physiological studies. Light traps constitute a good complementary sampling option for post-flexion larvae, being aware of species selectivity associated with their use.

2009Journal article

Open access

Influence of starvation on the critical swimming behaviour of the Senegalese sole (Solea senegalensis) and its relationship with RNA/DNA ratios during ontogeny

Publication . Faria, Ana M.; Muha, T.; Morote, E.; Teodosio, Maria

Food availability can affect larval survival directly through starvation and indirectly through the effects on larval growth rate, swimming performance and vulnerability to predators. In the present study we evaluate the effects of starvation on growth, nutritional condition and swimming behaviour of the Senegalese sole (Solea senegalensis) throughout ontogeny (8 to 14 days after hatching). Biochemical analysis (RNA/DNA ratios) and behavioural experiments (critical swimming speed, Ucrit) were conducted on larvae reared under 3 feeding treatments: fed ad libitum, deprived of food for 48 hours and deprived of food for 96 hours. Growth was significantly affected by feeding treatment, while only slight decreases in RNA/DNA ratio and swimming performance were registered. Late stage larvae of the three feeding treatments had slower critical speeds than the pre-flexion and flexion stages, which is probably related to the benthic lifestyle acquired by the species at the end of the larval period. These physiological and behavioural changes are in accordance with previous results, which show that flatfish larvae are more resistant to starvation than pelagic species and that they become less active later in development.

2011Journal article

Open access