TAXAS VITAIS DE LARVAS DE PEIXES NECESSÁRIAS À MODELAÇÃO DA DINÂMICA LARVAR NO ECOSSISTEMA DE AFLORAMENTO COSTEIRO IBÉRICO

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Publications

Assessing the impact of environmental forcing on the condition of anchovy larvae in the Cadiz Gulf using nucleic acid and fatty acid-derived indices

Publication . Teodosio, Maria; Garrido, Susana; Peters, J.; Miguel de Sousa Leitão, Francisco; Re, P.; Peliz, A.; Santos, A.M.P.

Understanding the environmental processes affecting fish larvae survival is critical for population dynamics,"conservation purposes and to ecosystem-based fishery management. Using anchovies (Engraulis encrasicolus) of the Cadiz Gulf as a study case and considering the "Ocean Triad" hypothesis, we investigate the larval ecophysiological status and potential survival in relation to oceanographic variables. Therefore, this study aims to describe the nutritional condition of anchovy larvae during spawning season (peak in summer) through nucleic acid- and fatty acid (FA)-derived indices and to analyze the effects of the major environmental parameters (Depth, Temperature, Salinity, Plankton biomass) on anchovy survival potential at early phases. Fish larvae were collected in August from 30 m to 400 m depth at 35 stations off the southern Iberian coast. A previous upwelling event influenced the oceanographic conditions of the more western stations off Cape Sao Vicente (CSV). Along the coast, the water became warmer from west to the east through Cape Santa Maria (CSM) ending at Guadiana estuary, where easterly winds originated the development of a counter current. The standardized RNA/ DNA (sRD) of anchovy larvae decreased throughout larval ontogeny, reflecting a reduction of growth during the development. Essential FA concentrations also decreased, but docosahexaenoic acid (DHA) in particular was highly conserved even after the reduction of total FA concentration in anchovy larvae related to the onset of swimming abilities (post-flexion phase). The oceanographic conditions (west upwelling, east counter current, and stratification) led to a nearshore aggregation of plankton and anchovy larvae with good ecophysiological conditions in the central area of the southern coast, where an optimal range of temperature and chlorophyll, as an indirect food proxy for anchovy larval development, were registered. The study proves that the oceanographic conditions of the study area are putative drivers of the ecophysiological condition of anchovy larvae to guarantee potential survival, supporting the "Ocean Triad" hypothesis with major repercussions for recruitment and population dynamics.

2017-02Journal article

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Born small, die young: Intrinsic, size-selective mortality in marine larval fish

Publication . Garrido, Susana; Ben-Hamadou, Radhouan; Santos, A. Miguel P.; Ferreira, S.; M A Teodosio; Cotano, U.; Irigoien, X.; Peck, M. A.; Saiz, E.; Re, P.

Mortality during the early stages is a major cause of the natural variations in the size and recruitment strength of marine fish populations. In this study, the relation between the size-at-hatch and early survival was assessed using laboratory experiments and on field-caught larvae of the European sardine (Sardina pilchardus). Larval size-at-hatch was not related to the egg size but was significantly, positively related to the diameter of the otolith-at-hatch. Otolith diameter-athatch was also significantly correlated with survival-at-age in fed and unfed larvae in the laboratory. For sardine larvae collected in the Bay of Biscay during the spring of 2008, otolith radius-at-hatch was also significantly related to viability. Larval mortality has frequently been related to adverse environmental conditions and intrinsic factors affecting feeding ability and vulnerability to predators. Our study offers evidence indicating that a significant portion of fish mortality occurs during the endogenous (yolk) and mixed (yolk /prey) feeding period in the absence of predators, revealing that marine fish with high fecundity, such as small pelagics, can spawn a relatively large amount of eggs resulting in small larvae with no chances to survive. Our findings help to better understand the mass mortalities occurring at early stages of marine fish.

2015Journal article

Open Access

Reproduction and respiration of a climate change indicator species: effect of temperature and variable food in the copepod Centropages chierchiae

Publication . Cruz, Joana; Garrido, Susana; Pimentel, Marta S.; Rosa, Rui; Santos, A. Miguel P.; Re, Pedro

The abundance of the calanoid copepod Centropages chierchiae has increased at the northern limits of its distribution in recent decades, mainly due to oceanic climate forcing, suggesting this as a key species in monitoring climate change. Laboratory experiments were conducted to study the combined effect of temperature, food type and concentration on the egg production rate (EPR) and hatching success (HS) of C. chierchiae. Females were fed on two monoalgal diets (Gymnodinium sp. and Phaeodactylum tricornutum) at two food concentrations and at three different temperatures (13, 19, 24C). Respiration rates of both genders were measured at four different temperatures (8, 13, 19, 24C). EPR was significantly different between temperatures and food concentrations, the maximum EPR being attained when the copepods were exposed to high food levels and at 19C. Prey type significantly influenced EPR; feeding on P. tricornutum resulted in higher egg production than Gymnodinium sp. HS was significantly lower at 13C than at 19 and 24C and higher with Gymnodinium sp. Respiration rates were sex independent and increased exponentially with temperature. To maintain basal metabolism, the minimum food intake of P. tricornutum ranged between 0.4 and 1.8 g C and for Gymnodinium sp. between 0.03 and 0.13 g C. Food intake was always higher than the metabolic demands, except for the highest temperature tested (24C). The present results confirm the sensitivity of C. chierchiae to temperature variations and may help in understanding the successful expansion of its distribution towards northern latitudes.

2013-10Journal article

Open Access

Effects of temperature, food type and food concentration on the grazing of the calanoid copepod Centropages chierchiae

Publication . Garrido, Susana; Cruz, Joana; Santos, A.M.P.; Re, Pedro; Saiz, Enric

Laboratory experiments were conducted to study the combined effect of temperature (8, 13, 19 and 24C), food type and food concentration on the grazing rates of the adult stages of the calanoid copepod Centropages chierchiae. As prey, the diatom Phaeodactylum tricornutum and the dinoflagellate Gymnodinium sp. (both ca. 15 m cell diameter) were used at a range of carbon concentrations similar to the ones experienced in nature (6.4 to 393.8 C L-1). Ingestion rates increased linearly with food concentration and did not differ between prey types. When comparing the effect of temperature, highest clearance and ingestion rates were obtained at 19C, whereas no difference was observed among the other temperatures. Daily rations varied between 1.2 and 183.5 body carbon day(1). Additional experiments were conducted to study the selective feeding behaviour of C. chierchiae when offered a mixture of different prey types. Selective feeding was dependent on food concentration; at low food levels, large cells were selected (Ditylum brightwellii), whereas at medium and high food concentrations no clear selection patterns were observed. In contrast to other studies, no positive selection of dinoflagellates over other algal food was found.

2013-08Journal article

Open Access