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- Effect of temperature on the growth, survival, development and foraging behaviour of Sardina pilchardus larvaePublication . Garrido, Susana; Cristovao, A.; Caldeira, C.; Ben-Hamadou, Radhouan; Baylina, N.; Batista, H.; Saiz, E.; Peck, M. A.; Re, P.; Santos, A.M.P.The effect of water temperature on the growth, survival, development and foraging behaviour of European sardine Sardina pilchardus larvae was examined in the laboratory. First, the capability of early sardine larvae to cope with starvation was assessed at temperatures from 10 to 22 degrees C. Second, we examined under ad libitum feeding conditions and across the range of temperatures experienced by sardines during spawning along the Atlanto-Iberian coast (13-17 degrees C) the ontogenetic changes in growth, survival and foraging behaviour of sardine larvae. Unfed larvae had similar maximum survival times (11-12 d post hatching, dph) from 13 to 15 degrees C, but the survival time was significantly shorter at the coldest and warmest temperatures tested. The survival of exogenously feeding larvae increased with temperature, but younger endogenously feeding larvae had higher survival at colder temperatures. The cumulative mortality after 25 dph, however, was similar at the 3 temperatures. Not only larval growth rate increased with increasing temperature, but ontogenetic development also occurred sooner and at smaller sizes. Notochord flexion, which is a developmental milestone for fish, occurred 10 d earlier at 17 rather than at 13 degrees C. The time spent swimming and the foraging behaviour (orientations to prey, feeding strikes and successful capture) significantly increased throughout the ontogeny and with temperature. This study highlights how even modest changes in spawning temperature can lead to large changes in the survival and growth of larval sardine. This study also reveals some of the mechanisms whereby inter-annual and seasonal variability in temperature can have significant ecological impacts at the population level.
- Reproduction and respiration of a climate change indicator species: effect of temperature and variable food in the copepod Centropages chierchiaePublication . Cruz, Joana; Garrido, Susana; Pimentel, Marta S.; Rosa, Rui; Santos, A. Miguel P.; Re, PedroThe 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.
- Forecasting shifts in habitat suitability across the distribution range of a temperate small pelagic fish under different scenarios of climate changePublication . Lima, André R.A.; Baltazar-Soares, Miguel; Garrido, Susana; Riveiro, Isabel; Carrera, Pablo; Piecho-Santos, A. Miguel; Peck, Myron A.; Silva, GonçaloClimate change often leads to shifts in the distribution of small pelagic fish, likely by changing the matchmismatch dynamics between these sensitive species within their environmental optima. Using present-day habitat suitability, we projected how different scenarios of climate change (IPCC Representative Concentration Pathways 2.6, 4.5 and 8.5) may alter the large scale distribution of European sardine Sardina pilchardus (a model species) by 2050 and 2100. We evaluated the variability of species-specific environmental optima allowing a comparison between present-day and future scenarios. Regardless of the scenario, sea surface temperature and salinity and the interaction between current velocity and distance to the nearest coast were the main descriptors responsible for the main effects on sardine's distribution. Present-day and future potential “hotspots” for sardine were neritic zones (<250 km) with water currents <0.4 m s−1 , where SST was between 10 and 22 °C and SSS > 20 (PSU), on average. Most variability in projected shifts among climatic scenarios was in habitats with moderate to low suitability. By the end of this century, habitat suitability was projected to increase in the Canary Islands, Iberian Peninsula, central North Sea, northern Mediterranean, and eastern Black Sea and to decrease in the Atlantic African coast, southwest Mediterranean, English Channel, northern North Sea and Western U.K. A gradual poleward-eastward shift in sardine distribution was also projected among scenarios. This shift was most pronounced in 2100 under RCP 8.5. In that scenario, sardines had a 9.6% range expansion which included waters along the entire coast of Norway up and into the White Sea. As habitat suitability is mediated by the synergic effects of climate variability and change on species fitness, it is critical to apply models with robust underlying species-habitat data that integrate knowledge on the full range of processes shaping species productivity and distribution.
- Physical-biological interactions in the life history of small pelagic fish in the Western Iberia Upwelling EcosystemPublication . Santos, A. Miguel P.; Chicharo, Maria Alexandra Teodosio; Santos, Antonina dos; Moita, Teresa; Oliveira, P. B.; Peliz, A.; Re, P.This paper reviews relevant investigations conducted in the Western Iberia Upwelling Ecosystem (WIUE) on the dynamics of small pelagic fish (SPF), its relationship to climate changes and processes related to the ‘ocean triad’ (enrichment, concentration, transport/retention). In the last decades, a decline in the productivity of several SPF species (e.g., sardine and horse mackerel) was observed in the WIUE, which is partially explained by environmental variability (e.g., changes in coastal upwelling). The main mechanism proposed to explain this decline is the increased frequency and intensity of upwelling events during the spawning season (winter) of these species, which is typically a period when convergence conditions prevail. Thus, this ‘anomalous’ situation promotes egg and larval dispersal away from the favourable coastal habitat (the shelf) and consequently has a negative impact on their survival and recruitment. However, the variability of local features like the Western Iberia Buoyant Plume (WIBP) and the Iberian Poleward Current (IPC) introduce important fluctuations in the transport patterns of the region, and could modulate the impact of these winter upwelling events in the survival of larvae. The retention on the shelf of larval sardine along convergence zones formed by the interaction of these two features plays an important role in their survival. Furthermore, the WIBP is a suitable environment for the growth of phytoplankton and for larval fish survival. From these findings it is clear that simplified Ekman transport models could not explain larval fish transport/retention patterns in this region and more realistic biophysical models should be used to simulate the local oceanographic conditions to understand larval dynamics and the success of recruitment of SPF in the Western Iberia.
- Field test of an autonomous observing system prototype for measuring oceanographic parameters from shipsPublication . Santos, Fernando P.; Rosa, Teresa L.; Hinostroza, Miguel A.; Vettor, Roberto; Santos, A. Miguel P.; Guedes Soares, C.A prototype of an autonomous system for the retrieval of oceanographic, wave, and meteorologic data was installed and tested in May 2021 on a Portuguese research vessel navigating on the Atlantic Ocean. The system was designed to be installed in fishing vessels that could operate as a distributed network of ocean data collection. It consists of an automatic weather station, a ferrybox with a water pumping system, an inertial measurement unit, a GNSS unit, an onboard desktop computer, and a wave estimator algorithm for wave spectra estimation. Among several parameters collected by this system’s sensors are the air temperature, barometric pressure, humidity, wind speed and direction, sea water temperature, pH, dissolved oxygen, salinity, chlorophyll-a, roll, pitch, heave, true heading, and geolocation of the ship. This paper’s objectives are the following: (1) describe the autonomous prototype; and (2) present the data obtained during a full-scale trial; (3) discuss the results, advantages, and limitations of the system and future developments. Meteorologic measurements were validated by a second weather station onboard. The estimated wave parameters and wave spectra showed good agreement with forecasted data from the Copernicus database. The results are promising, and the system can be a cost-effective solution for voluntary observing ships.
- Decapod larvae distribution and species composition off the southern Portuguese coastPublication . Pochelon, Patricia N.; Pires, Rita F. T.; Dubert, Jesus; Nolasco, Rita; Santos, A. Miguel P.; Queiroga, Henrique; dos Santos, AntoninaFor decapod crustaceans, the larval phase is the main responsible for dispersal, given the direct emission from adult habitats into the water column. Circulation patterns and behavioural mechanisms control the dispersal distance and connectivity between different areas. Information on larval distribution and abundance is required to predict the size and location of breeding populations, and correctly manage marine resources. Spatial distribution and abundance data of decapod larvae, and environmental parameters were assessed in winter surveys off the southern Portuguese coast. To better understand the oceanic structures driving larval distribution patterns, in situ physical parameters were measured and a hydrodynamical model used. Inter-annual, cross-shore and alongshore differences on decapod larvae distribution were found. Brachyuran crabs dominated the samples and similar taxa composition was observed in the most dynamic areas. Coastal taxa dominated the nearshore survey and were almost absent in the more offshore one, that registered much lower abundances. An upwelling front allowed a clear cross-shore species separation, also evident in the abundance values and number of taxa. Hydrodynamical conditions and adult habitats were the main factors explaining the observed patterns. Important missing information to understand the distribution patterns of decapod larval communities and the mechanisms behind them is given for the region.
- Assessing the impact of environmental forcing on the condition of anchovy larvae in the Cadiz Gulf using nucleic acid and fatty acid-derived indicesPublication . 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.
- RNA:DNA ratios as a proxy of egg production rates of AcartiaPublication . Cruz, Joana; Alexandra Teodosio Chicharo, Maria; Ben-Hamadou, Radhouane; Manuel Zambujal Chicharo, Luis; Garrido, Susana; Re, Pedro; Santos, A.M.P.Estimates of copepod secondary production are of great importance to infer the global organic matter fluxes in aquatic ecosystems and species-specific responses of zooplankton to hydrologic variability. However, there is still no routine method to determine copepods secondary production in order to eliminate time consuming experimental analyses. Therefore, we determined whether there is a correlation between Egg Production Rates (EPR) and RNA:DNA ratios of Acartia species, by measuring their seasonal and spatial variability and the influence of environmental factors for Acartia sp. collected in the Guadiana river estuary. EPR of Acartia tonsa was positively related with chlorophyll a concentration, freshwater inflow and biomass of dinoflagellates, while Acartia clausi was only related to dinoflagellates. Dinoflagellates seem to be the optimal food item influencing the reproduction of both Acartia species in the studied area. The biochemical index RNA:DNA was positively related to EPR, indicating that it is a good proxy of copepod production and a promising method to use in the future to estimate secondary production. (C) 2017 Elsevier Ltd. All rights reserved.
- Born small, die young: Intrinsic, size-selective mortality in marine larval fishPublication . 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.
- Review and prospects for autonomous observing systems in vessels of opportunityPublication . Rosa, Teresa L.; Santos, A. Miguel P.; Vettor, Roberto; Soar, C. GuedesThis paper focuses on the state of the art on Autonomous Observing Systems (AOS) used in Vessels of Opportunity (VOO) for collecting in situ atmospheric, oceanic and biogeochemical data. The designation Vessels of Opportunity includes all kinds of ships, even if not having scientific goals, which may carry proper devices that autonomously measure environmental variables. These vessels can be merchant, military, research, cruise liners, fishing, ferries, or even private yachts or sailing boats. The use of AOS can provide the opportunity for highly refined oceanographic data and improved derived data estimation, for local, regional or global scales studies. However, making the collected information accessible, both for scientific and technical purposes, provides a challenge in data management and analysis, which must, above all, ensure trusted useful data to the stakeholders. An overall review of the systems implemented is presented. This includes the definition of objectives, the recruitment of vessels and a review on the installation of proper acquisition devices; the selection and collection of Essential Oceanic Variables (EOV); the mechanisms for transmitting the information, and the quality control analysis and dissemination of data. The present and future capabilities of VOO for measuring EOV, within the Portuguese context are referred.