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Research Project
VARIAÇÃO ONTOGENÉTICA DE CAPACIDADES COMPORTAMENTAIS E SENSORIAIS EM LARVAS DE PEIXES COSTEIROS
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Effects of starvation on swimming performance and body condition of pre-settlement Sparus aurata larvae
Publication . Faria, Ana M.; Gonçalves, Emanuel J.; Chicharo, Alexandra
Body condition in larval fishes is an important determinant of survival in the natural
environment. However, few studies correlate body condition with behavioural traits critical for survival, such as swimming performance. In the present study, we compared normally fed larvae of gilthead seabream Sparus aurata Linnaeus, 1758, at various intervals post-hatch with larvae which were
starved for 1 to 3 d (for Ucrit) or 2 d (for swimming endurance). Feeding treatment (fed and or unfed)
had no effect on the relationship between Ucrit and larval size. However, in the endurance experiment, fed individuals swam twice as far as unfed larvae (19.7 km for fed larvae and 9.5 km for unfed
larvae). The RNA/DNA ratio was higher in fed larvae in the Ucrit experiment, but significant effects
were only detectable after a 3 d period of starvation. Fulton’s condition factor was significantly higher
in fed larvae in the endurance trial, which suggests that growth (in weight) of starved larvae was
affected by long-term swimming. Taken together, these results suggest that for aging and orientation
behaviours (activities in which critical speeds might be involved) are not affected by reduced feeding
over a few days, but that sub-lethal effects of starvation may affect dispersal potential (for which
endurance swimming is critical) and therefore compromise subsequent recruitment to the adult
population.
Ontogeny of swimming behaviour of two temperate clingfishes, Lepadogaster lepadogaster and L-purpurea (Gobiesocidae)
Publication . Faria, Ana M.; Gonçalves, Emanuel
Gobiesocids are typically reef-dwelling species whose larvae have been found in several nearshore rocky environments; this suggests a possible retention pattern for these species. Retention may occur due to the physical features of an area and/or active larval behaviour, such as swimming abilities. In the laboratory, we measured the ontogeny of swimming behaviour (routine speed and critical speed, U-crit) of 2 clingfish species, Lepadogaster lepadogaster and L. purpurea. L. lepadogaster larvae swam better than L. purpurea larvae, but this difference might be related to differences in water temperature, since the former is a spring spawner, whereas the latter spawns during winter. It is well known that water viscosity increases with decreasing temperature, making swimming more difficult. Routine and critical swimming speeds of larvae of both species increased with ontogeny (size) despite high variability at any ontogenetic state. U-crit ranged from 1 to 9.4 and 1.2 to 6.5 cm s(-1) in L. lepadogaster and L. purpurea, respectively. Routine speeds were similar to 18 to 19% of the maximum U-crit registered for both species. Interestingly, swimming speed started to decrease as settlement size (10 to 11 mm total length) was approached, concurrent with the development of a ventral sucking disk that allows individuals to attach to the bottom of the swimming chamber and counteract strong currents. This shift in swimming behaviour that is associated with settlement is probably an adaptation to the cryptobenthic mode of life of these fish.
Ontogeny of critical swimming speed of wild-caught and laboratory-reared red drum Sciaenops ocellatus larvae
Publication . Faria, Ana M.; Ojanguren, Alfredo F.; Fuiman, Lee A.; Gonçalves, Emanuel J.
Critical swimming speed (U,,it) provides a useful estimate of maximum swimming performance for fish larvae that can be used to assess transport and migratory potential. We measured U,it of red drum Sciaenops ocellatus larvae through its ontogeny and compared the swimming performance of laboratory-reared larvae to that of wild-caught individuals. U-crit increased with ontogeny (size), even though variability in U-crit at any ontogenetic state was large. U-crit for wild-caught larvae increased from 9.7 to 22.2 cm s(-1) over the range of 8.3 to 16.3 mm TL and from 1.1 to 20.5 cm s(-1) over the range of 3.0 to 19.1 mm TL for reared larvae. The ontogenetic increase in critical swimming speed occurred in 2 phases-an early phase of rapid improvement, and a later phase of slower improvement. This sharp change in the trajectory of swimming performance coincided with important changes in ecology, morphology, and hydrodynamics. During the early phase, larvae were pelagic, their growth was highly allometric, especially in the caudal region, and they swam in the inertial hydrodynamic regime. The onset of the later phase coincided with settlement into seagrass beds, isometric growth, and inertial effects on locomotion. Wild larvae generally exhibited greater values of U,it than reared larvae of a comparable size, but the difference was not statistically significant. The results of this comparison imply that research on reared larvae may provide naturalistic results for swimming performance and that hatchery-produced larvae may perform certain behaviours well when released into the wild.
Ontogeny of behavioural abilities in temperate reef fish larvae
Publication . Faria, Ana Margarida da Silva; Gonçalves, Emanuel; Chícharo, Alexandra
A maior parte das espécies associadas a recifes possui uma fase larvar pelágica, seguida de uma fase juvenil e adulta demersal. A fase pelágica pode apresentar consideráveis capacidades de dispersão. A visão tradicional, baseada em estudos de um conjunto limitado de espécies de sistemas temperados, pressupunha que as capacidades natatórias das larvas no plano horizontal eram muito limitadas e, dessa forma, irrelevantes para o potencial de dispersão. Segundo esta perspectiva, a dispersão era essencialmente explicada por fenómenos de transporte passivo e a única informação necessária para modelar a dispersão seriam as correntes e a duração da fase larvar. No entanto, nas últimas duas décadas, a investigação do comportamento natatório das larvas de recifes tropicais veio provar que as larvas estão longe de serem partículas passivas, e têm capacidades comportamentais consideráveis, capazes de influenciar os seus padrões de dispersão.
Apesar dos recentes avanços nos estudos de comportamento larvar em peixes de recifes tropicais, os estudos de comportamento em peixes temperados são ainda escassos. Nesse sentido, esta tese representa um significativo contributo para o estudo das capacidades natatórias de peixes de sistemas temperados. A ontogenia do comportamento natatório foi investigada em quatro espécies temperadas (2 Gobiesocidae, 1 Sparidae, 1 Soleidae) e uma espécie temperada-quente (Sciaenidae). Os resultados sugerem que a diferença de capacidades natatórias entre espécies tropicais e temperadas não é significativa quando aspectos taxonómicos, morfológicos e estados de desenvolvimento são tidos em conta. Adicionalmente, foi analisada a influência da condição nutricional no comportamento
natatório e observou-se que larvas em inanição são capazes de levar a cabo comportamentos de fuga a predadores e captura de presas, mas em termos de potencial de dispersão, estas larvas são significativamente afectadas, compromentendo assim a sua sobrevivência e futuro recrutamento.
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Funding agency
Fundação para a Ciência e a Tecnologia
Funding programme
Funding Award Number
SFRH/BD/21742/2005