Francesc Sardà

Institut de Ciències del Mar, Barcino, Catalonia, Spain

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Publications (104)116.83 Total impact

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    ABSTRACT: The Norway lobster, Nephrops norvegicus, can be captured by haul nets only during the emergence from its burrow. In the last few decades, an extensive field research revealed distinct diel (24-h–based) catchability patterns at different depths. Laboratory experiments suggested that burrow emergence (used as a proxy of catchability) is endogenously controlled via a circadian system. Results were usually presented in terms of mean effects without a quantification of inter-individual variability and arrhythmia. Here, we studied the burrow emergence of 52 adult Nephrops by an infrared actograph endowed with an artificial burrow. Animals were exposed to 12-12 h light-darkness cycle, simulating photic condition of the lower shelf. Forty-five animals showed rhythmic emergence (87%), while seven were arrhythmic (13%). Rhythmic animals were clustered according to their timing of emergence: 54% at dusk and 4% at dawn. Moreover, other animals showed fully diurnal or nocturnal emergence (10% and 19%, respectively). The comparison of our results with those derived from temporally scheduled trawling indicates that bimodal catch patterns observed in shelf populations are poorly observed during individual experiments in the laboratory, where the same light conditions are simulated. Nephrops burrow emergence seems to be the result of a mixed endogenous-exogenous control, while arrhythmia could also be present in the wild.
    Scientia Marina 11/2014; 77(4):641-647. · 1.01 Impact Factor
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    ABSTRACT: The field measurements of swimming activity rhythms of fishes are scant for the difficulty of counting individuals at a high frequency over a large period of time. Cabled observatory video monitoring allows such a sampling at a high frequency. Unfortunately, automated animal visual counting is still a major bottleneck. We developed a new automated video-imaging protocol for the 24-h continuous counting of fishes in calorimetrically calibrated time-lapse photographic outputs, taken by a shallow water (20 m depth) cabled video-platform, the OBSEA. All the images were acquired within a standardized Region Of Interest, represented by a 2 x 2 m methacrylate panel, endowed with a 9-colour calibration chart, and calibrated using the recently implemented “3D Thin-Plate Spline” warping approach.
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    ABSTRACT: High frequency monitoring and the reducing of disturbance of sampling activities have a vital importance in the study of fish communities. The aim of this paper is to describe temporal patterns in habitat utilization by a coastal fish assemblage throughout the year 2012. A high frequency long term photo identification monitoring has been carried out with this objective. At about 63.000 individuals representing 28 species were identified, suggesting the occurrence of different day-night rhythms among them. Future comparisons with physical parameters will be developed to get a better understanding of their movement patterns.
    5TH MARTECH International Workshop On Marine Technology, Girona (Spain); 10/2013
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    ABSTRACT: The rhythmic behavior of marine species generates uncertainties in population and biodiversity assessments if the frequency of sampling is too low and irregular over time. Few attempts have been made to link community changes to the rhythmic behavior of individuals within populations. Cabled video observatories can be used to explore community changes over different temporal windows as a result of the activity rhythms of individuals within populations. In this study, we used, for the first time, a coastal cabled observatory (OBSEA) to video monitor activity rhythms of different fish species within an artificial reef area at a high frequency. During 1 mo, 30 min daily count patterns were continuously measured and compared with the corresponding solar irradiance. A significant (p < 0.05) day-night patterning was observed in the majority of recognized taxa by Chi-Square periodogram analysis. Three types of rhythms were identified in waveform plotting: (1) diurnal (Chromis chromis, Coris julis, Diplodus annularis, D. cervinus, D. sargus, D. vulgaris, Serranus cabrilla, Dentex dentex, Symphodus sp.); (2) nocturnal (Atherina sp. and Scorpaena sp.); and (3) crepuscular (Apogon imberbis, Oblada melanura, and Spicara maena). Diurnal species clustered around maximum averaged irradiance (computed from a cosinor analysis). The results were discussed evaluating whether visual count time series represent a reliable proxy for the swimming activity rhythms of individuals and whether the complex habitat use of coastal fishes would require the use of spatial networks of cameras.
    Marine Ecology Progress Series 07/2013; · 2.64 Impact Factor
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    ABSTRACT: In this study, we present and test the functioning of a automated multi-flume actograph that is able to simulate concomitant geophysical cycles (day-night and hydrodynamic cycles) characterizing the benthic environment of continental margins. The burrowing Norway lobster (Nephrops norvegicus, L.) was used to test the functioning of the device. The system is endowed with pumps and a pipe system for periodical current flow generation. Monochromatic blue light cycle (472 nm) was provided by submergible LED's lighting strips. Locomotor activity of 8 individuals was tracked by 4 HD video cameras during a 10 days trial. A customized automated video-imaging protocol in MATLAB calculated displacement of animals (cm/min). The functioning of the system was tested simulating an Atlantic continental shelf scenario (i.e. light intensity of 4 · 10−3 μE/m2/s and current flow at 10 cm/s). Robust time series outputs of nocturnal phase were reported, with the first laboratory evidence of the influence of current flow on burrow emergence of the species. Water flow increase inhibited lobster movement generating a dual reaction in relation to their burrow emergence phase. The method presented here could be pivotal to study unknown aspects of Norway lobster ecology.
    Journal of Experimental Marine Biology and Ecology 06/2013; 446:177-185. · 2.26 Impact Factor
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    ABSTRACT: The Citizen Science refers to the public participation in scientific activities and research projects related with environment and its biodiversity are taking advantage of new technologies such us internet and mobile phones with recording capabilities for an easy data collection and sharing. In this paper, we presented a Citizen Science experience with the OBSEA costal-cabled video-observatory, deployed in western Mediterranean in 2009. A local biodiversity survey is going to be conducted by citizens as generic non-experienced users, high-school students, and amateur divers helping to identify and classify fishes appearing within different digital products such as time-lapse images and footages. Accordingly, we implemented a protocol for the web-based species identification supervised by scientists, in order to evaluate the different performances for each group.
    International Symposium on Underwater Technology (UT13); 03/2013
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    ABSTRACT: Seasonality in marine fish communities is usually studied by using different sampling techniques (e.g. visual census in shallow water or trawling in deeper areas) that are hard to perform over long periods with a high frequency of data recording. Furthermore, the coupling with fluctuations in key habitat parameters (e.g. light, temperature, salinity, and turbidity) is not a simple task to accomplish. Cabled video-observatories implemented with multiparametric sensors for habitat monitoring are allowing for the first time the continuous and long term recording of marine communities' dynamic (e.g. day-night, seasonal, and predator-prey fluctuations). In this scenario, the OBSEA video-cabled observatory has been recently deployed (2009) within a coastal area in the western Mediterranean Sea (Vilanova i la Geltrú -Spain) at a depth of 20 m. It is endowed with a video camera and a CTD. The OBSEA is located in a sandy area in which are placed numerous artificial reefs that protect the ground from trawling. The OBSEA is placed in front of one of these reefs. Accordingly, we report here only the preliminary results of this study consisting of one month video-monitoring at 30 min frequency of the local fish community in association with environmental fluctuations. In the future this analysis will cover an entire year. Waveform analysis was carried out in order to detect the occurrence of significant daily periodicity in species abundance, while time series of community fluctuations were related to environmental parameters (temperature and pressure at the sea bottom). In both cases particular attention was directed to interacting species such as predators and preys. Preliminary results highlight how cabled observatories could contribute to study community's dynamic. Finally, the analysis of the entire year observations will allow to study changes of the artificial reef community among different seasons. Moreover, the long term data from OBSEA could permit to evaluate possible climate changes effects on the local fish community.
    International Symposium on Underwater Technology (UT13); 03/2013
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    ABSTRACT: Field measurements of the swimming activity rhythms of fishes are scant due to the difficulty of counting individuals at a high frequency over a long period of time. Cabled observatory video monitoring allows such a sampling at a high frequency over unlimited periods of time. Unfortunately, automation for the extraction of biological information (i.e., animals' visual counts per unit of time) is still a major bottleneck. In this study, we describe a new automated video-imaging protocol for the 24-h continuous counting of fishes in colorimetrically calibrated time-lapse photographic outputs, taken by a shallow water (20 m depth) cabled video-platform, the OBSEA. The spectral reflectance value for each patch was measured between 400 to 700 nm and then converted into standard RGB, used as a reference for all subsequent calibrations. All the images were acquired within a standardized Region Of Interest (ROI), represented by a 2 × 2 m methacrylate panel, endowed with a 9-colour calibration chart, and calibrated using the recently implemented "3D Thin-Plate Spline" warping approach in order to numerically define color by its coordinates in n-dimensional space. That operation was repeated on a subset of images, 500 images as a training set, manually selected since acquired under optimum visibility conditions. All images plus those for the training set were ordered together through Principal Component Analysis allowing the selection of 614 images (67.6%) out of 908 as a total corresponding to 18 days (at 30 min frequency). The Roberts operator (used in image processing and computer vision for edge detection) was used to highlights regions of high spatial colour gradient corresponding to fishes' bodies. Time series in manual and visual counts were compared together for efficiency evaluation. Periodogram and waveform analysis outputs provided very similar results, although quantified parameters in relation to the strength of respective rhythms were different. Results indicate that automation efficiency is limited by optimum visibility conditions. Data sets from manual counting present the larger day-night fluctuations in comparison to those derived from automation. This comparison indicates that the automation protocol subestimate fish numbers but it is anyway suitable for the study of community activity rhythms.
    Sensors 01/2013; 13(11):14740-53. · 2.05 Impact Factor
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    ABSTRACT: The Norway lobster is a burrowing decapod of elevated commercial importance for the European fishery. Understand which factors affect its diel (24-h based) catchability is of importance for its stock assessment. Here we presented preliminary results on burrow emergence modulation on lobsters exposed to water flow cycles in the laboratory simulating internal tides.
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    ABSTRACT: To adequately describe seasonal rhythms in habitat utilization by fish communities, observations are needed that occur at a relatively high frequency and over large temporal windows. For the first time, images collected from a cabled video-observatory (the western Mediterranean expandable SEAfloor OBservatory; OBSEA) were utilized to examine habitat utilization by coastal fishes. Over the course of a year, hourly digital images of the water column and an artificial reef were obtained during daylight hours. For each image, the total number of species, an estimate of the abundance of individuals, and the Shannon Diversity Index were quantified. A total of 22 fish species commonly associated with nearshore western Mediterranean habitats were identified, and significant spatial (water column vs. artificial reef), seasonal (spring, summer, autumn, and winter), and daily (morning, midday, and sunset) differences in habitat utilization occurred. Four species (Diplodus vulgaris, Diplodus cervinus, Diplodus sargus, and Scorpaena porcus) were associated with the artificial reef, while one species (Pagrus pagrus) chiefly occurred in the water column. Chromis chromis and Diplodus annularis occurred at the site more frequently in the winter and autumn, respectively, while 14 other species utilized the site more frequently in either the spring (8 spp) or summer (6 spp). In addition, Dentex dentex and Spicara maena occurred more frequently at sunset, while D. cervinus displayed a crepuscular rhythm (occurring more frequently in the morning and at sunset). Species diversity was highest in the summer and lowest in the winter. If not taken into account when planning in situ sampling, such seasonal and/or diel differences may lead to spurious estimates of population sizes and biodiversity. We suggest that cabled video-observatories offer a non-invasive and reliable technology for faunistic sampling and population assessment in coastal water of the Mediterranean and likely elsewhere.
    Journal of Marine Biology 08/2012; 159:2809-2817.
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    ABSTRACT: The OBSEA laboratory has integrated an IP-Video camera that works 24 hours per day recording images of local fauna. These images have been analyzed in order to identify the different marine organisms in the vicinities. Peer Reviewed Postprint (published version)
    01/2012;
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    ABSTRACT: All marine species studied thus far show rhythmic temporal patterns in their behavioural, physiological, and molecular functions, which are collectively known as biological rhythms. Biological rhythms are generated by biological clocks that time biological functions and are synchronized by geophysical cycles, such as the solar light-dark cycle and tidal cycle. On continental margins, behavioural rhythms can be detected by diel (i.e., 24-hour based) or seasonal periodical trawling as a consequence of massive inward and outward displacements of populations to and from the sample areas. As a result, significant errors in population/stock and biodiversity assessments performed by trawling may occur if timing of sampling is not taken into account. The increasing number of cabled and permanent multiparametric seafloor observatories now allows direct, continuous, and long-lasting monitoring of benthic ecosystems and analysis in relation to several habitat cycles. This review describes the adaptation of this technology to investigations of rhythmic behaviour by focusing on automated video imaging. Diel fluctuations in the number of video-observed individuals can be used as a measure of average population rhythmic behaviour. The potential implementation of automated video image analysis in relation to animal tracking and classification procedures based on the combined use of morphometric tools and multivariate statistics is detailed in relation to populational and community studies. Based on video cameras mounted at multiparametric cabled observatories, an integrated time-series analysis protocol using chronobiomedical procedures is proposed to place video-recorded bioinformation in an oceanographic context.
    Oceanography and Marine Biology: An Annual Review. 01/2012; 50:233-284.
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    ABSTRACT: Unmanned aircraft systems (UAS) are remote-controlled devices capable of collecting information from difficult-to-access places while minimizing disturbance. Although UAS are increasingly used in many research disciplines, their application to wildlife research remains to be explored in depth. Here, we report on the use of a small UAS to monitor temporal changes in breeding population size in a Black-headed Gull Chroicocephalus ridibundus colony. This method makes it possible to obtain georeferenced data on nest locations without causing colony disturbance, which would not otherwise be possible via direct ground observations.
    Ibis 01/2012; 154(1):177-183. · 2.36 Impact Factor
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    Oceanography and marine biology 01/2012; 50:235-286. · 6.91 Impact Factor
  • Oceanography and Marine Biology : An Annual Review. 01/2012; 50:235-286.
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    ABSTRACT: Unmanned aircraft systems (UAS) are remote‐controlled devices capable of collecting information from difficult‐to‐access places while minimizing disturbance. Although UAS are increasingly used in many research disciplines, their application to wildlife research remains to be explored in depth. Here, we report on the use of a small UAS to monitor temporal changes in breeding population size in a Black‐headed Gull Chroicocephalus ridibundus colony. This method makes it possible to obtain georeferenced data on nest locations without causing colony disturbance, which would not otherwise be possible via direct ground observations.
    Ibis 01/2012; 154(1). · 2.36 Impact Factor
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    Mediterranean Submarine Canyons Ecology and Governance, First edited by Maurizio Würtz, 01/2012: chapter 3.8: pages 133-144; IUCN, Gland, Switzerland and Málaga, Spain., ISBN: 978-2-8317-1469-1
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    Marine Biodiversity World Conference; 09/2011

Publication Stats

1k Citations
116.83 Total Impact Points

Institutions

  • 1992–2012
    • Institut de Ciències del Mar
      Barcino, Catalonia, Spain
  • 1999–2011
    • Spanish National Research Council
      • Institute of Marine Sciences
      Madrid, Madrid, Spain
  • 1998
    • University of California, Santa Barbara
      • Marine Science Institute
      Santa Barbara, California, United States
    • University of Barcelona
      • Departament de Fisiologia
      Barcelona, Catalonia, Spain