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A pesar del gran interés ecológico y económico que tiene el mero (Epinephelus marginatus), y el importante esfuerzo investigador realizado desde los años 90, no se han definido las condiciones para su óptimo engorde en cautividad. En general, las mejores condiciones de cultivo son las que proporcionan un ambiente similar al existente en el medio natural, y en el mero, estas condiciones estarían relacionadas con sus hábitos sedentarios, que al ocupar cuevas en el fondo, le permitiría destinar gran parte de la energía adquirida a crecimiento. Las diferentes condiciones de cultivo ensayadas en este estudio muestran que la presencia de refugios (CR) no mejoró el engorde respecto al cultivo sin refugios (SR), mientras que el grupo cultivado en jaula (JAU) mostró el menor peso medio a lo largo del estudio, con 123,1±67,5 g a los 645 días de edad (DDE), frente a SR y CR, que fueron similares, pero con una mayor dispersión en los peces CR (151,6±42,3 g y 164,7±84,6 g, respectivamente). El aumento del diámetro del refugio (225 DDE) y la retirada de la jaula (400 DDE) mejoraron los parámetros de engorde, aumentando el peso un 62% frente al 29% del periodo previo, y un 47% a 530 DDE respecto al 12% del periodo previo, respectivamente, pero no disminuyó la dispersión. La falta de refugios no perjudicó el engorde respecto a su presencia, mientras que el cultivo en jaula requiere un suministro de alimento mejorado.

El cultivo de Seriola dumerili constituye una opción a la diversificación y crecimiento de la producción de peces marinos, que aprovecharía, además, los sistemas de producción e instalaciones en el mar comúnmente usadas para especies como Sparus aurata. Sin embargo, este crecimiento podría estar amenazado por las patologías especificas e inespecíficas de ambas especies, principalmente las causadas por ectoparásitos. Este estudio muestra, en grupos de dorada (GD), seriola (GS) y dorada y seriola juntas (GDS-GSD), una evolución estable del número de huevos de Zeuxapta seriolae (GS: 35±10, y GDS-GSD: 67±24) y de Sparicotyle chrysophrii (GD: 59±10, y GDS-GSD: 22±4), mientras que los huevos de Neobebedenia melleni colectados en GS (2483±364) y GDS-GSD (3168±474) fueron entre un 15 y 20% más altos que en GD (508±100). No se encontraron diferencias en el hematocrito, glucosa, proteína, colesterol y triglicéridos de cada especie cultivada sola o de forma conjunta durante el estudio, pero los niveles de glucosa plasmática en seriola fueron un 50% más altos, y el colesterol un 30% más bajo que en la dorada. NewSpec

We combine consistently dated benthic carbon isotopic records distributed over the entire Atlantic Ocean with numerical simulations performed by a glacial configuration of the Norwegian Earth System Model with active ocean biogeochemistry, in order to interpret the observed Cibicides δ13C changes at the stadial-interstadial transition corresponding to the end of Heinrich Stadial 4 (HS4) in terms of ocean circulation and remineralization changes. We show that the marked increase in Cibicides δ13C observed at the end of HS4 between ~2000 and 4200 m in the Atlantic can be explained by changes in nutrient concentrations as simulated by the model in response to the halting of freshwater input in the high latitude glacial North Atlantic. Our model results show that this Cibicides δ13C signal is associated with changes in the ratio of southern-sourced (SSW) versus northern-sourced (NSW) water masses at the core sites, whereby SSW is replaced by NSW as a consequence of the resumption of deep water formation in the northern North Atlantic and Nordic Seas after the freshwater input is halted. Our results further suggest that the contribution of ocean circulation changes to this signal increases from ~40 % at 2000 m to ~80 % at 4000 m. Below ~4200 m, the model shows little ocean circulation change but an increase in remineralization across the transition marking the end of HS4. The simulated lower remineralization during stadials than interstadials is particularly pronounced in deep subantarctic sites, in agreement with the decrease in the export production of carbon to the deep Southern Ocean during stadials found in previous studies.

Regarding the research activities carried out by Oceanographic Centre of the Canary Islands (IEO-CSIC) during intersession, several studies on different topics were presented. Firstly, reproductive traits for the four main species have been analysed including all the data obtained since the monitoring system was launched in 2013. Although with some variations, the spawning season matched with winter and beginning spring for S. colias, T. picturatus and S. pilchardus. However, spawning individuals of S. aurita are present all year round. Sizes at first maturity (SFM) were also estimated, with slightly smaller sizes obtained for S. colias and T. picturatus (around 19 cm of total length) compared with the reference values (20 cm and 23 cm, respectively) (Jurado-Ruzafa and Santamaría, 2013; Lorenzo and Pajuelo, 1996). It seems that SFM remains stable for S. pilchardus (15 cm) (Méndez-Villamil et al., 1997). In the case of S. aurita, size at first maturity has been estimated for the first time in the Canary Islands, and has been recently published (Jurado-Ruzafa et al., 2022). Secondly, a first attempt to describe total catches of the Canary artisanal purse-seine fleet based on scientific observation shows that discards are more relevant than what was supposed, reaching the 25 percent of the total catches. The situation is even more concerning if only S. colias is considered, with discards around 40 percent of the total catches, mainly impacting on juveniles’ fraction, which is usually used as bait by commercial vessels but that are not officially reported. Finally, very preliminary results were shown to the working group about the potential adaptive plasticity in Scomber colias from the Canary Islands, based on otolith shape analyses. These results were obtained from analysing 748 otoliths extracted from August 2016 to December 2017. A DIvisive ANAlysis (DIANA) Clustering method using the fourth wavelet obtained from otolith contours resulted in the detection of five different morphotypes (or otolith phenotypes), with two of them representing 85 percent of the samples analysed, and whose individuals were slightly larger than for the other morphotypes. Further questions should be explored, addressing possible intraspecific variation in the growth rate among phenotypes; phenotypes proportions change in relation to seasonal variations; existence of different ecological strategies related to each phenotype and the presence of these otolith phenotypes in other geographical areas, as it has been described for T. picturatus (Tuset et al., 2019; Vasconcelos et al., 2021). References Jurado-Ruzafa, A. and M.T.G. Santamaría. 2013. Reproductive biology of the blue jack mackerel, Trachurus picturatus (Bowdich, 1825), off the Canary Islands. Journal of Applied Ichthyology, 29(3): 526–531. Jurado-Ruzafa, A., B. Sotillo de Olano, Z. Santana Arocha, B. G. Mañé, C. Estil-las, E. Hernández, S. Jiménez, G. González-Lorenzo and C. Perales-Raya. 2022. Reproductive traits of the round sardinella in the Canary Islands (Spain, NW Africa). Journal of the Marine Biological Association of the UK, (early view) 1-7. Lorenzo, J. M. and J.G. Pajuelo. 1996. Growth and reproductive biology of chub mackerel Scomber japonicus off the Canary Islands. South African Journal of Marine Science, 17(1): 275-280. Méndez-Villamil, M., J.M. Lorenzo, J.M. González and R. Soto. 1997. Periodo reproductor y madurez sexual de la sardina Sardina pilchardus (Walbaum, 1792) en aguas de Gran Canaria (Islas Canarias). Boletín del Instituto Español de Oceanografía, 13(1-2): 47-55. Tuset, V.M., A. Jurado-Ruzafa, J.L. Otero-Ferrer and M.T.G. Santamaría. 2019. Otolith phenotypic variability of the blue jack mackerel, Trachurus picturatus, from the Canary Islands (NE Atlantic): Implications in its population dynamic. Fisheries Research, 218: 48-58. Vasconcelos, J., A. Jurado-Ruzafa, J.L. Otero-Ferrer, A. Lombarte, R. Riera and V.M. Tuset. 2021. Thinking of Fish Population Discrimination: Population Average Phenotype vs. Population Phenotypes. Frontiers in Marine Science, 8(1489). BAses de Datos y Estadística de las pesquerías Artesanales de Canarias: Evaluación, Interacciones ambientales y Modelización de los Stocks Biología de recursos vivos de Canarias Estudio de las Pesquerías de AFRICa 2 PACA-BADE EPAFRIK-2 PACA-BIO

including iodothyronine deiodinases 1, 2 and 3 (dio1, dio2, dio3) was unaffected. Feeding Se enriched rotifers effectively increased Se in ABT larvae tissue. The improved growth observed in Se supplemented treatments might be related to an accelerated development as the flexion index was significantly higher in all Se enriched treatments compared to the non-supplemented control. A similar effect by Se supplementation has been previously described in Senegalese sole (Solea senegalensis) in relation to an enhanced thyroid hormone activity by Se supplementation (Ribeiro et al., 2012). The Se level of 0.10 µg g-1 dw measured in non-supplemented rotifers is below known requirements in fish (Antony Jesu Prabhu et al. 2016). In contrast, rotifers supplemented with the lowest Se level (Se3) contained 4.42 µg Se g-1, which might be sufficient to cover requirements for this mineral as selenoproteins displayed maximum expression in ABT larvae fed this treatment. The increased seleno-enzyme production might have contributed towards an improved antioxidant status in ABT larvae, indicated by a transcriptional downregulation of redox sensitive antioxidant enzymes cat and sod. In conclusion, rotifers without Se enrichment are suboptimal for ABT larvae at first feeding. A dietary Se level of 4.42 µg g-1 dw is recommended as it boosted growth performance and improved the antioxidant status in ABT larvae.

Knowledge gaps pertaining to the remediation of freshwater lakes impacted by oil spills have persisted despite recent record highs for oil production and transportation across vulnerable regions in North America. The multiyear Freshwater Oil Spill Remediation Study (FOReSt), conducted at the IISD-Experimental Lakes Area in Canada, is focusing on the efficacy of minimally invasive methods for remediating oil spills in freshwater boreal lakes. In this thesis, the impacts and remediation of diluted bitumen (dilbit) and conventional heavy crude oil (CHV) spills were investigated (year 1), as were a variety of different remediation methods for spills of dilbit on different shoreline substrates (year 2). Two common small-bodied fish, fathead minnows (Promephales promelas) and finescale dace (Chrosomus neogaeus), were used to assess exposure to petrogenic polycyclic aromatic compounds (PACs) in model enclosed shoreline ecosystems impacted by spills and remediated using minimally invasive techniques. Short-term exposure to PACs, the most toxicologically relevant compounds in oil, was assessed in fish using biliary metabolite concentrations. In year one, finescale dace and fathead minnows residing in oil treated enclosures each had biliary pyrene metabolite concentrations that were positively correlated with pyrene concentrations in the water of the enclosures. Three months after the initial spills, fish in the enclosure receiving dilbit were significantly more exposed to PACs than fish in reference enclosures that did not receive oil. In year two, both finescale dace and fathead minnows residing in oil-treated exposures, regardless of shoreline substrate, showed increased exposure to PACs compared to fish in reference enclosures and the pristine lake environment two and a half months after the spills. No significant differences in exposure were observed among the remediation treatments. Biliary PAC metabolite concentrations were positively predicted by parent PAC concentrations in periphyton. PACs in periphyton two and a half months after oil introduction were positively correlated with PACs in the enclosures one week after spills, suggesting fish also had increased exposure to periphyton-bound alkyl-PACs. This thesis validates the use of small-bodied fish in assessing PAC exposure following freshwater oil spills and demonstrates the difficulties in estimating exposure using environmental concentrations in natural systems.

Algae blooms are becoming more frequent throughout the world, causing significant impacts on the environment and even on human health. Benthic cyanobacteria, such as the species of the genus Lyngbya C.Agardh ex Gomont, are one more component of the communities of intertidal and subtidal habitats of all the oceans. Nevertheless, these species present the ability to grow rapidly under certain conditions, even forming blooms that dominate the habitat, and eventually, may affect the rest of the species in the community harmfully. In this study, we present the results of an oceanographic survey carried out on the southern coasts of Fuerteventura and Lanzarote in November 2021, where the massive presence of Lyngbya sp. (species yet to be confirmed genetically) was detected on circalittoral bottoms and at depths greater than 100 m. Dense populations of this species were recognized visually, sampling with ROV-T Tasife, and were also identified by live samples collected with the Liropus ROV. Lyngbya populations presented different colors, mainly depending on the depth, being dark red in the shallowest waters at 80 m and whitish at around 150 m. The accumulations of filaments of this alga overgrown the bed and all the benthic species found there, especially some vulnerable habitat-forming species: cnidarian species such as the black corals Antipathes furcata, Antipathella wollastoni or Stichopathes gracilis, or sponges such as different species of the Axinellidae family. This is the first study assessing the impact of the algae bloom on the circalittoral benthic environment of The Canary Islands. The present study was funded by the project ESMARES2 from the IEO-CSIC, under the framework of the application of the Marine Strategy Framework Directive (MSFD), ordered by the Ministerio de Transición Ecológica y Reto Demográfico (MITERD) of Spain.

Since 2004, high resolution profiles of the 3D velocity of the water column have been collected at the westernmost sill of the Strait of Gibraltar (Espartel Sill), with the aim of monitoring the Mediterranean water outflow and evaluating its short and long term variability. Initially equipped with a 75 kHz up-looking Acoustic Doppler Current Profiler (ADCP) and a Conductivity/Salinity (CT) probe, the mooring line has been upgraded through years adding more, and more technologically advanced, instruments. In 2016, a 500 kHz ADCP was installed in down-looking mode, with the aim of covering the so far unsampled bottom layer, below the buoy deployed ∼20 m above the seafloor. Despite the implicit variability of such a long series, the averaged profile of the observed along-strait current systematically showed local minima ∼50 m above seafloor, which have been interpreted as the result of the interaction between diurnal and semidiurnal tidal currents (Sammartino et al., 2015). The prevailing semidiurnal tide drives periodic accelerations of the westward Mediterranean current flowing at the bottom, whereas diurnal constituents slow them down few meters above seafloor, giving rise to those local minima in amplitude. This mechanism is often related to severe drops in measurements accuracy. In 2019, the main ADCP was replaced by a 100 kHz model capable of collecting high resolution echograms of the water column with an additional vertical beam. This new information reveals the key role of scatterers concentration, which undergo diel vertical migrations, and affect the accuracy of current observations, which in turn rely on the amplitude of scattered echo recorded by the instruments. Actually, echo amplitude reaches average correlations of 0.7 with measurements uncertainty. In light of these new insights, accurate updates of the Mediterranean outflow calculations are performed (García-Lafuente et al., 2021) and new estimations of trend and long-term variability, are provided.