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Las especies de túnidos tienen una visión bien desarrollada. La morfología de la retina de juveniles de atún rojo (Thunnus thynnus) cultivados y salvajes fue investigada histológicamente. Los resultados obtenidos mostraron una mayor anchura del epitelio pigmentario y valores del índice de la retina más elevados en los individuos salvajes que en los individuos de cultivo. Introducción, Tuna species have well-developed vision. The morphology of the retina of Atlantic bluefin tuna juveniles (Thunnus thynnus) from cultured and wild fish were investigated histologically. The results showed a wider pigment epithelium and greater values of the retinal index in wild individuals than in cultured fish., FEMP, Newspec-Murcia

This study examines the anatomical development of the visual system of Atlantic bluefin tuna, Thunnus thynnus, during the first 15 days of life at histological level, with emphasis in the immunohistochemical characterization of different cell types. As an altricial fish species, the retina was not developed at hatching. The appearance of eye pigmentation and the transformation of the retina from an undifferentiated neuroblastic layer into a laminated structure occurred during the first two days of life. At 16 days after hatching (DAH), the ganglion cells were arranged in a single row in the central region of the retina and the outer segments of the photoreceptors were morphologically developed. Furthermore, at this age, all the retinal cell types were immunohistochemically characterized. The presence of ganglion cell axons was confirmed with the TUJ1 antibody and the existence of functional synapses in the plexiform layers with antibodies against SV2. Cone opsins were immunostained with antibodies against visinin and CERN-922 immunoreactive rods were also identified. Different subpopulations of amacrine cells were immunostained with antibodies against αTH and PV. Highly GS-immunoreactive Müller cells were also detected at this age. These observations suggested that the T. thynnus retina was fully functional at the end of the second week of life. Basic studies on early morphology of the visual system and larval behaviour are necessary to support applied research on larval rearing. Furthermore, they may have implications for understanding larval ecology in the wild., SI

One of the most promising aquaculture species is the Atlantic bluefin tuna ( Thunnus thynnus ) with high market value; disease control is crucial to prevent and reduce mortality and monetary losses. Microsporidia ( Fungi ) are a potential source of damage to bluefin tuna aquaculture. A new microsporidian species is described from farmed bluefin tunas from the Spanish Mediterranean. This new pathogen is described in a juvenile associated with a highly severe pathology of the visceral cavity. Whitish xenomas from this microsporidian species were mostly located at the caecal mass and ranged from 0.2 to 7.5 mm. Light and transmission electron microscopy of the spores revealed mature spores with an average size of 2.2 × 3.9 μm in size and a polar filament with 13–14 coils arranged in one single layer. Phylogenetic analysis clustered this species with the Glugea spp. clade. The morphological characteristics and molecular comparison confirm that this is a novel microsporidian species, Glugea thunni . The direct life-cycle and the severe pathologies observed makes this parasite a hard risk for bluefin tuna cultures., SI

In this study, we assessed the effect of environmental salinity and pH as independent factors on larval survival of Atlantic bluefin tuna (ABFT –Thunnus thynnus) together with their whole-body Na+/K+-ATPase and v-type H+-ATPase activities. Fertilized eggs of ABFT were obtained from a spontaneous spawning of broodstock in the farming facilities at El Gorguel (Cartagena, SE Spain) and were transferred to facilities of the Spanish Institute of Oceanography (IEO) in Mazarrón (SE Spain). In a first experiment, eggs (200 fertilized eggs L-1 per treatment, in 3 replicates) were exposed to different salinities treatments and constant pH 8.0 (control) until hatch was completed (50 h post- fertilization, hpf, at 23 ºC): 27, 30, 33, 36, 37, 38 (control), 39, 40, 43, 46 and 49 ppt. In a second experiment eggs (200 fertilized eggs L-1, in 3 replicates) were exposed to seawater salinity (SW: 38 ppt) and four reduced pH treatments until hatch was completed (50 hpf at 23 ºC): 8.0 (control), 7.7, 7.5 and 7.3. An inverse „„U-shaped‟‟ relationship was observed between environmental salinity and number of hatched larvae. An opposite pattern was observed for both Na+/K+-ATPase and H+-ATPase activities in hatched larvae, increasing both activities in groups exposed to extreme salinities. Thus, larval survival was higher at intermediate salinities and lower at the extreme salinities tested. These results suggest higher survival rates with lower active pumps activities. No significant differences in larval survival were observed with pH treatment, but lower H+-ATPase activity was detected at control environmental pH (pH 8.0). Survival results are discussed in terms of osmoregulatory cost adapting to a salinity and pH predicted for the near future scenarios., SI

Underwater noise has been identified as a relevant pollution affecting marine ecosystems in different ways. Despite the numerous studies performed over the last few decades regarding the adverse effect of underwater noise on marine life, a lack of knowledge and methodological procedures still exists, and results are often tentative or qualitative. A monitoring methodology for the behavioral response of bluefin tuna (Thunnus thynnus) when exposed to ship and wind turbine operational noises was implemented and tested in a fixed commercial tuna feeding cage in the Mediterranean sea. Fish behavior was continuously monitored, combining synchronized echosounder and video recording systems. Automatic information extracted from acoustical echograms was used to describe tuna reaction to noise in terms of average depth and vertical dimensions of the school and the indicators of swimming speed and tilt direction. Video recordings allowed us to detect changes in swimming patterns. Different kinds of stimuli were considered during bluefin tuna cage monitoring, such as noise generated by feeding boats, wind farm operational noise, and other synthetic signals projected in the medium using a broadband underwater projector. The monitoring system design was revealed as a successful methodological approach to record and quantify reactions to noise. The obtained results suggested that the observed reactions presented a strong relationship with insonification pressure level and time. Behavioral changes associated with noise are difficult to observe, especially in semi-free conditions; thus, the presented approach offered the opportunity to link anthropogenic activity with possible effects on a given marine species, suggesting the possibility of achieving a more realistic framework to assess the impacts of underwater noise on marine animals., AZIMUT IEO, SI

Atlantic bluefin tuna (Thunnus thynnus) larvae show strong piscivorous feeding behavior at the very early larval stage and this enables them to grow at high rates. We conducted a laboratory experiment in which Atlantic bluefin tuna larvae were offered larval prey for the first time at different ages to simulate the early onset of piscivory at three treatments: yolk-sac larvae (YSL), delayed onset of piscivory (DYSL) and a solely planktivorous diet (Rotifers). The otolith microstructure was then used to compare the larval size distribution at the onset of the experiment with the estimated previous size-at-age of the survivors at the end of the experiment by back- calculation. Within a cohort, our results show size-selective mortality of the largest larvae independent of the differences in the timing of onset of piscivory and differences in growth patterns. The results also corroborate the rapid response of Atlantic bluefin tuna to piscivory in terms of growth reflected in the otolith increment widths. Being bigger did not infer a survival advantage and mortality rates did not decline with increasing larval size. Smaller size at a given age could under certain conditions and stages of development confer a survival advantage of individual members of a larval cohort when suitable small-sized prey is available., SI

Atlantic bluefin tuna (ABT; Thunnus thynnus) is a highly regarded and consumed species, but farming is still in its infancy. Currently, nothing is known about the presence of circadian rhythmicity at central or peripheral tissues, or if there are daily rhythms in expression of genes involved in lipid metabolism. In order to elucidate clock gene regulation of genes of lipid metabolism in ABT, six clock genes (bmal1, clock, cry1, cry2, per1 and per2) were sequenced and 24 h expression of these genes determined in brain and liver of fish acclimated to a light:dark (L:D) photoperiod. Additionally, the daily expression of lipid metabolism and digestive enzyme genes in ABT was also determined in liver. All six clock genes displayed rhythmicity in the brain and liver, other than cry2, which did not show an acrophase in liver. In liver, all the transcription factors analysed other than srebp1 and srebp2 displayed rhythmicity, with lxr and pparα displaying diurnal expression, whereas pparγ was highly expressed at the end of the scotophase. Some of the target genes of lxr such as elovl5 and lpl also oscillated rhythmically, with acrophases during the photophase. In contrast, only three of the eight digestive enzyme genes studied displayed rhythmicity, at different times of the day, suggesting that either ABT display different feeding periods or the digestion of some nutrients (e.g. lipids) is prioritized over others. The present study showed that clock and lipid metabolism genes displayed strong daily rhythmicity in ABT brain and liver, which could be an area of considerable interest for the establishment of efficient feeding protocols in this new aquaculture species., SI

[ES] La acción antrópica es responsable de una gran cantidad de ruidos en el medio marino y en muchas ocasiones con consecuencias devastadoras para los ecosistemas afectados. El atún rojo del Atlántico (Thunnus thynnus) es una especie con una gran importancia económica gravemente afectada por la sobreexplotación, en los últimos 30 años han proliferado las instalaciones destinadas al engrase de los atunes para su posterior venta. Los atunes en cautividad se ven expuestos a una gran cantidad de ruido de origen antropogénico. Durante un mes se realizó un monitoreo para determinar el impacto de la contaminación acústica en el comportamiento de atunes en cautividad en las instalaciones del ICRA en Mazarrón (Murcia). Para ello, se han usado técnicas ópticas (cámara estereoscópica), de acústica pasivas (hidrófono) y acústica activa (ecosondas) en distintas configuraciones (ventral, dorsal y lateral). Los resultados de este estudio muestran una relación entre comportamientos poco habituales y sonidos a baja frecuencia. También se registraron vocalizaciones de los atunes asociadas con la generación de sonidos pulsados de baja frecuencia (100-180 Hz y duración inferior a un segundo)., [EN] The anthropic action is responsible for a great deal of noise in the marine environment and often with devastating consequences for the affected ecosystems. Atlantic Bluefin Tuna (Thunnus thynnus) is a species of major economic importance seriously affected by overexploitation, In the past 30 years there has been a proliferation of facilities for the greasing of tuna for subsequent sale. Tunas in captivity are exposed to a large amount of anthropogenic noise. During one month, a monitoring was carried out to determine the impact of noise pollution on the behaviour of tuna in captivity at the ICRA facilities in Mazarrón (Murcia) using optical techniques (stereoscopic cameras), passive acoustic techniques (hydrophone) and active acoustic techniques (echosounders) have been used in different configurations (ventral, dorsal and lateral). The results of this study show a relationship between unusual behaviors and low frequency sounds. Tuna vocalizations associated with the generation of low frequency pulsed sounds (100-180 Hz and duration less than one second) were also recorded.

Notochord flexion increases the swimming capacity of fish larvae, aids in the capture of mobile prey, and coincides with the timing of when the physiological capacities of larvae begin to develop significantly, allowing an early shift to piscivory. Therefore, reaching the flexion stage as soon as possible can be considered beneficial for the growth and survival of the larvae. Individual growth differences of larvae from the same cohort are very common before reaching flexion and the potential explanation is still unknown. In this study, we examined if the nutritional status of the larvae, measured by the RNA:DNA and DNA:DW ratios, explains the differences in the development of notochord flexion in laboratory-reared Atlantic bluefin tuna (ABFT; Thunnus thynnus) and Atlantic bonito (AB; Sarda sarda) larvae. Moreover, we described the ontogeny of the different stages and condition indices. The daily average condition of ABFT estimated by the RNA:DNA and DNA:DW ratios increased with larval age and developmental stage, whereas in AB it was not. In both species, bigger larvae at a specific age had higher nutritional condition than smaller larvae regardless of developmental stage. However, in ABFT the DNA:DW ratio indicated lower condition for the biggest larvae within developmental stages F0 (pre-flexion) and F3 (post-flexion). After removing the size effect, larger individuals of ABFT within flexion stages F1 and F2 had higher condition than any other larval stages, whereas in AB an indistinct trend within stages was found. Our results confirm that in ABFT the RNA:DNA ratio is correlated with faster development while the DNA:DW ratio is negatively correlated with the time to flexion. The trends found in the DNA:DW ratio points at cell growth mechanisms being a better indicator of larval condition that the RNA:DNA ratio. Our findings suggest that under culture, ad libitum conditions, larval nutritional conditions measured by nucleic acid ratios, might not be enough to explain developmental differences in fast growing species., SI

In this study, we assessed the effect of pH and salinity as independent factors on larval survival (LS) of Atlantic bluefin tuna (ABFT –Thunnus thynnus) together with their Na+/K+-ATPase and V-type H+-ATPase activities. Fertilized eggs of ABFT were obtained on 25 June 2016 from a spontaneous spawning of broodstock in the farming facilities at El Gorguel (Cartagena, SE Spain) of Caladeros del Mediterráneo Company. The fertilized eggs were transferred to facilities of the Spanish Institute of Oceanography (IEO) in Mazarrón (SE Spain). In a first experiment, eggs (n = 150 per treatment, in 3 replicates) were exposed to sea water salinity (SW: 38 ppt) and four pH treatments until hatch was completed (44 hours at 23 ºC): 8.0 (control), 7.7 (near future), 7.5 (far future) and 7.3 (lower). In a second experiment eggs (n = 150 per treatment, in 3 replicates) were exposed to eleven salinities treatments and constant pH 8.0 (control) until hatch was completed (44 hours at 23 ºC): 27 , 30 , 33 , 36 , 37 , 38 (control), 39 , 40 , 43 , 46 and 49 ppt. No significant differences in LS were observed with pH treatment, but lower H+-ATPase activity was detected at control environmental pH (pH 8.0). A ‘‘U-shaped’’ relationship was observed between hatching salinity and both Na+/K+-ATPase and H+-ATPase activities in whole larvae hatched, increasing both activities in groups exposed to extreme salinities. However, LS showed an inverse “U shape” curve respect to environmental salinity with higher values at intermediate salinities and lower LS at extreme salinities. These results suggest higher survival rates with lower active pumps activities. Survival results are discussed in terms of osmoregulatory cost adapting to a pH and salinity predicted for the near future scenarios. This work was funding by the European Union’s Horizon 2020research and innovation programme under Grant Agreement No. 678193.

Elongation of very long-chain fatty acid 4 (Elovl4) proteins are involved in the biosynthesis of very long-chain (> C24) fatty acids and in many teleost fish species they are key enzymes in the pathway for the production of docosahexaenoic acid (DHA; 22:6n-3) from eicosapentaenoic acid (EPA; 20:5n-3). Therefore, Elovl4 may be particularly important in Atlantic bluefin tuna (ABT; Thunnus thynnus) characterised by having high DHA to EPA ratios. The present study cloned and characterised both the function and expression of an elovl4 cDNA from ABT. The Elovl4 had an open reading frame of 915 base pairs encoding a putative protein of 304 amino acids. Alignment and phylogenetic analyses indicated that the Elovl4 isoform identified in the present study was an Elovl4b. Functional characterisation demonstrated that the Elovl4b enzyme had elongase activity towards all the polyunsaturated fatty acid (PUFA) substrates assayed. The ABT Elovl4b contributed to DHA biosynthesis by elongation of EPA and DPA to 24:5n-3, the latter being desaturated to 24:6n-3 by the action of fads2 (Δ6 desaturase). Additionally, the ABT Elovl4b has a role in the biosynthesis of very long-chain PUFA up to C34, compounds of key structural roles in neural tissues such as eye and brain, which had high levels of elovl4b transcripts. Surprisingly, while the relative expression of fads2, required for the production of DHA from EPA, was increased in liver of ABT fed a diet with reduced levels of EPA and DHA, expression of elovl4b was reduced. Results indicated that ABT has enzymes necessary for endogenous production of DHA from EPA and demonstrate that Elovl4b can effectively compensate for absence of Elovl2., SI

The present study aims to solve the problem related to the difficulty in measuring the bluefin tuna (Thunnus thynnus L.) larval length when the larvae curl for several reasons (freezing, fixing, handling or in notochord flexion phase). To do that, the relationship between the horizontal eye diameter and the notochord length has been studied in 1143 bluefin tuna larvae from the eye pigmentation up to the full notochord flexion (between 2 and 15 days post hatching) reared in the facilities of the Marine Aquaculture Plant in Mazarrón (Murcia, SE Spain) belonging to the Spanish Institute of Oceanography (IEO). Our results shown that the horizontal eye diameter (ED) could be used to estimate the notochord length (NL) of bluefin tuna larvae up to complete notochord flexion (around 15 days old), using the equation: NL= 1.81953 + 6.5031 ED (r2 = 89.79%, p, El presente estudio intenta resolver la problemática asociada a la dificultad de medir la longitud de larvas de atún rojo (Thunnus thynnus L.) cuando éstas se curvan debido a varios factores (al congelarlas, fijarlas, debido a la manipulación o en la fase de flexión de la notocorda). Para ello, se ha estudiado la relación existente entre el diámetro ocular (que usualmente no se ve afectada por los citados factores) y la longitud estándar en 1143 larvas de atún rojo desde la pigmentación del ojo hasta la completa flexión de la notocorda (entre dos y quince días después de la eclosión) cultivadas en las instalaciones de la Planta de Cultivos Marinos de Mazarrón (Murcia), del Instituto Español de Oceanografía (IEO). Nuestros resultados muestran que la medida horizontal del diámetro ocular (LO) puede ser utilizada para la estimación de la longitud de la notocorda (LN) de larvas de atún rojo que han completado la flexión de la notocorda (alrededor de 15 días de vida) usando la ecuación LN= 1,81953 + 6,5031 LO (r2 = 89,79%, p

En esta comunicación se presentan los resultados de crecimiento de alrededor de 80 juveniles de atún rojo criados entre el 15 de febrero de 2018 y el 22 de enero de 2019 (300 días) en un tanque de 22 m de diámetro y 10 m de profundidad de la Instalación del IEO para el Control de la Reproducción del Atún rojo (ICRA). Los datos de crecimiento en talla y en peso se obtuvieron de forma no invasiva mediante un sistema de estéreo-video cámaras. El peso medio inicial fue de 2,90 kg (CV=14,2%) y el final 14,1 kg (CV=23%) con una tasa específica diaria de crecimiento (SGR%) de 0,73. El índice de conversión FIFO estuvo en torno a 14 con una tasa de conversión de alrededor de 4 (considerando 70% de agua en la carnada). The growth of around 80 bluefin tuna juveniles, reared between 15th February 2018 and 22nd January 2019 (300 days) in a 22m diameter and 10m depth tank held in the IEO bluefin tuna reproduction facility (ICRA) are shown in the present study. The growth data in size and weight have been obtained in a non invasive way by means of a stereo-video camera system. The initial and final mean weight were 2.90 kg (VC=14.2%) and 14.1 kg (VC=23%) with a specific daily growth rate of 0.73, a FIFO index about 14 and a conversion rate close to 4 (considering 70% water in the bait)

[ES] Se obtuvieron valores de potencia del blanco o Target Strength (TS) de ecoregistros de ecosondas de 200 kHz en un tanque de crecimiento de doradas (Sparus aurata) y ecoregistros de ecosondas de 200 kHz y 333 kHz en tanques de crecimiento de atunes (Thunnus thynnus), con el fin de relacionar los valores de TS obtenidos con el desarrollo larvario. Para esto se realizaban dos experimentos en tiempos distintos, en un tanque de 1.6m de alto y 2m de diámetro, se llevaron a cabo medidas diarias de longitud total (mm) y diámetro (mm) de la vejiga natatoria si estaba presente. Las medidas fueron realizadas en las instalaciones del Centro de Cultivo de Mazarrón, en el tanque G4, con un transductor situado en el fondo del tanque, además se realizaron dos cierres en el flujo de aire uno nocturno y otro diurno, con el fin de obtener valores de TS control sin el efecto de las burbujas de aire. Los análisis de los valores de TS evidenciaron dos grupos a lo largo del tiempo, correspondiente a las larvas con y sin la vejiga natatoria desarrollada. Los resultados de la distribución del TS muestran una relación directa con la longitud y con el diámetro de la vejiga natatoria de las larvas., [EN] Target Strength (TS) values of 200 kHz echo sounder ecoregisters were obtained in a gilthead growth tank (Sparus aurata) and 200 kHz and 333 kHz echo sounder ecoregisters in tuna growth tanks (Thunnus thynnus), with the in order to relate the values of TS obtained with larval development. For this, two different experiments were performed at different times, in a 1.6m high tank and 2m in diameter, daily measurements of total length (mm) and diameter (mm) of the swim bladder were performed if present. The measurements were made at the facilities of the Mazarrón Cultivation Center, in the G4 tank, with the transducer located at the bottom of the tank, two closures were made in the air flow one night and one day, in order to obtain values of TS control without the effect of air bubbles. When analyzing the values of TS, two groups are observed over time corresponding to the larvae with and without the developed swim bladder. The results of the distribution of the TS show a direct relationship with the length and with the diameter of the swim bladder of the larvae.

Taurine appears to be a crucial nutrient for teleosts, especially top predator species such as Atlantic bluefin tuna (Thunnus thynnus, L.; ABT). While dietary taurine supplementation has been highly recommended, there is a lack of studies on taurine assimilation and biosynthesis for this iconic species. The present study aims to provide insight into the molecular mechanisms involved in taurine biosynthesis and transport in ABT by studying tissue distribution and ontogenetic development of expression of cysteine dioxygenase (cdo), cysteine sulfinic acid decarboxylase (csad), 2-aminoethanethiol dioxygenase (ado) and taurine transporter (tauT) in response to graded levels of dietary taurine supplementation. The full open reading frame (ORF) for cdo and partial sequences for csad, ado and tauT were obtained, with the translated polypeptides being 202, 176, 166 and 324 amino acids, respectively. All three showed characteristics such as cupin motifs in Cdo and predicted N-glycosylation sites in Taut that are common to these genes in other species. Phylogenetic analysis showed that the ABT sequences clustered with sequences of other teleosts, and separately from mammals and molluscs. Tissue distribution varied, with adipose tissue, kidney, white muscle and testis/brain showing highest expression of cdo, csad, ado and tauT, respectively. Whole larvae expression of csad peaked at 15 dah, whereas the other genes generally increased throughout development to show highest expression at 25 dah. The nutritional trial was carried out by feeding ABT larvae from mouth opening to 14 days after hatching (dah) with rotifers (Brachionus rotundiformis) enriched with 4 different levels of taurine: 0.0 (tau0), 0.5 (tau0.5), 1.0 (tau1), and 2.0 g taurine per 106 rotifers (tau2). Rotifers effectively accumulated taurine with ABT larvae fed on treatment tau2 attaining the highest concentration of taurine. However, ABT larvae fed tau1 displayed higher growth and survival, and flexion index at 14 dah, than larvae fed the other taurine levels. Larvae fed tau1 also showed generally higher expression of tauT and cdo and digestive and antioxidant enzyme genes. While this study showed that larval ABT express taurine metabolism genes, suggesting possible synthesis that could contribute to the taurine pool in the fish, larval performance was enhanced by a level of dietary taurine (3.7 mg taurine g−1 rotifer) supplied by enrichment of rotifers at 1 g taurine per 106 rotifers., SI

Mass mortality is still one of the main constraints in larval rearing of Atlantic bluefin tuna (Thunnus thynnus L.; ABT). Early data related to the feeding sequence of ABT larvae suggested that mortality observed during the first stages of life could be partly due to nutritional deficiencies. Previous studies demonstrated that copepods ap- peared to be a superior live prey compared to rotifers during the first 2 weeks of life. Our overarching aim was to evaluate different feeding strategies during first feeding of ABT larvae from a performance, compositional and molecular perspective. In order to do so, two groups of ABT larvae were fed with either copepod (Acartia tonsa; C) nauplii or rotifers (Brachionus rotundiformis; R) enriched with Algamac 3050® from mouth opening to 13 days after hatching (dah). After this, the group C-larvae was fed either Artemia enriched with Algamac 3050® (CA), Acartia nauplii and copepodites (CC) or sea bream (Sparus aurata) yolk-sac larvae (CY), while the R group were fed on Artemia enriched with Algamac 3050® (RA) up to 18 dah. At 13 dah, larvae fed copepods (C) had grown better than those fed enriched rotifers (R) although there were no significant differences in survival. ABT larvae fed R accumulated highest eicosapentaenoate (EPA) but lowest docosahexaenoate (DHA) and total n-3 long- chain polyunsaturated fatty acids (LC-PUFA) than C-fed larvae, reflecting the dietary contents. There was no activation in the expression of the enzymes involved in EPA and DHA biosynthesis. However, the different live prey showed regulation of transcription factor, digestive enzyme, lipid metabolism and oxidative stress genes. At 18 dah, larvae fed CY and CA treatments were largest in size, with larvae fed RA displaying the lowest growth, with no significant differences in survival among the dietary treatments. The highest DHA contents were found in ABT larvae fed CC and CY, whereas the lowest contents were found in RA-fed larvae. Indeed, larvae fed RA showed the highest level of the intermediate product n-3 docosapentaenoate, which could reflect increased activity of the biosynthetic pathway although this was not supported by gene expression data., SI

[EN] In this work, acoustic and computer vision techniques are combined to develop an automatic procedure for biomass estimation of tuna during transfers. A side scan sonar working at 200¿kHz and a stereo camera, positioned facing towards the surface to record the ventral aspect of fish, are set as acquisition equipment. Moreover, a floating structure has been devised to place the sensors between cages in transfers, creating a transfer canal that allows data acquisition while fish swim from donor to receiving cage. Biomass assessment is computed by counting transferred tuna and sizing a representative sample of the stock. The number of transferred tuna is automatically deduced from acoustic echograms by means of image processing techniques, whereas tuna size is computed from the stereo videos using our automatic computer vision procedure based on a deformable model of the fish ventral silhouette. The results show that the system achieves automatic tuna counting with error below 10%, achieving around 1% error in the best configuration, and automatic tuna sizing of more than 20% of the stock, with highly accurate Snout Fork Length estimation when compared to true data from harvests. These results fulfil the requirements imposed by International Commission for the Conservation of Atlantic Tunas for compliant transfer operations., This work was supported by funding from the BIACOP project, ES13/41, from the EU Fisheries Control Programme through the Secretaría General de Pesca, Ministerio de Agricultura, Alimentación y Medio Ambiente (MAGRAMA), and by ACUSTUNA project ref. CTM2015-70446-R (MINECO/ERDF, EU). The BIACOP project has been possible thanks to the collaboration of the Spanish company Grup Balfegó S.L. that also supplied boats and divers to acquire underwater video in the Mediterranean Sea. Special personal acknowledgements to Manuel Guijarro and Antonio López, and to David Baizán from IMA – Acuicultura Integrada Multitrófica S.L.U., for their assistance with the design and construction of the floating structures.

[EN] This study presents various models based on formulae relating weight and dimensions (length, height and width) of Bluefin tuna, Thunnus thynnus (L.), fattened in captivity. The main aim of establishing these expressions is to design tools for indirectly predicting the weight of a Bluefin tuna from measurements of one or more dimensions obtained using non-invasive methods such as stereoscopic cameras. Measurements of maximum length, height and width following slaughter were taken of fish fattened in captivity (n = 2078). Different relationships drawn from the dimensions of the tuna against their weight are fitted with part of the data collection and later checked against a reserved sample set. The resulting formulae are compared with the formulae most commonly used in the case of wild tuna. The results of this study confirm that, for tuna fattened in cages, the availability of more than one dimension to estimate weight improves the predictive power of the model and reduces error in the estimate., This work was supported by funding from ACUSTUNA project ref. CTM2015-70446-R (MINECO/ERDF, EU). The authors are grateful for the support provided by Grup Balfegó.

Life-history traits such as spawning migrations and timing of reproduction are adaptations to specific environmental constraints and seasonal cycles in many organisms’ annual routines. In this study we analyse how offspring fitness constrains spawning phenology in a large migratory apex predator, the Atlantic bluefin tuna. The reproductive schedule of Atlantic bluefin tuna varies between spawning sites, suggesting plasticity to local environ- mental conditions. Generally, temperature is considered to be the main constraint on tuna spawning phenology. We combine evidence from long- term field data, temperature-controlled rearing experiments on eggs and larvae, and a model of egg fitness, and show that Atlantic bluefin tuna do not spawn to optimize egg and larval temperature exposure. The timing of spawning leads to temperature exposure considerably lower than optimal at all spawning grounds across the Atlantic Ocean. The early spawning is constrained by thermal inhibition of egg hatching and larval growth rates, but some other factors must prevent later spawning. Matching offspring with ocean productivity and the prey peak might be an important driver for bluefin tuna spawning phenology. This finding is important for predictions of reproductive timing in future climate warming scenarios for bluefin tuna., SI

In this manuscript, we test how an understanding of geographical variation in larval fitness in relation to temperature and habitat use could be a useful method to improve our understanding of recruitment and develop better indices of annual recruitment. On the basis of the assumption that growth and survival of tuna larvae are influenced by temperature, we have developed a potential larval survival index for Atlantic bluefin tuna (Thunnus thynnus) by combining empirical data from egg and larval rearing experiments with temperature data from hydrodynamic models. The experiments were designed to test the full range of temperature variability that bluefin larvae would experience in the field and provide a mechanistic understanding of the processes driving egg and larval survival. We then developed a biological model using the temperature-related growth expressions and a size-dependent survival function for the larvae. The biological model was applied to a time-series of spatially explicit temperature data for the western Mediterranean from the Strait of Gibraltar to 6 E, which includes the major recognized bluefin tuna eastern stock spawning area, the Balearic Sea. Our results show that areas with high probabilities of larval survival coincide with those that would be considered as optimal based on other data sources (ichthyoplankton surveys, spawning female locations from commercial fisheries data, and adult tracking data). However, evidence of spawning has been found in areas with suboptimal thermal habitats, as predicted by the model, which we discuss regarding sampling effort and salinity fronts. There was a good match between the survival index and recruitment indices from standardized CPUE fisheries data. These results have implications for our understanding of the recruitment process of the eastern stock of Atlantic bluefin tuna, since they suggest that the combined effects of temporal and spatial variability of the environment drive recruitment success, which has important implications for the management of the species., SI

The development of formulated diets and feeds is essential to increase production of farmed tuna species. There is limited knowledge of this topic, mainly on Pacific Bluefin tuna (Thunnus orientalis) in Japan, whereas no major attempts have been made with Atlantic Bluefin tuna (Thunnus thynnus; ABT). In the present study, two trials were performed using inert formulated diets as on-growing feeds for weaned ABT juvenile in order to establish adequate dietary levels of both lipid and omega-3 long-chain polyunsaturated fatty acids (LC-PUFA). In a first trial, ABT (initial weight = 2.9±0.9g) were fed for 10 days with either a commercial (Magokoro®, MGK) or two experimental feeds with two different lipid levels (15 or 20%) using krill oil (KO) as the single lipid source in order to estimate the suitable lipid content. Fish fed MGK displayed the highest growth, followed by 15KO, with no differences in fish survival. Thus, a lipid content of 15% was considered better than 20% for ABT juveniles. In the second trial, fish (initial weight = 3.3 ± 0.6g) were fed either MGK, 15KO or a feed containing 15% lipid with a combination (1:1, v/v) KO and rapeseed oil (RO) (15KORO). Fish fed 15KO and 15KORO showed the highest growth in terms of weight and fork length (including weight gain and SGR). Increasing dietary lipid level or adding RO to the feeds did not increase liver lipid content. The liver fatty acid profile largely reflected dietary intake confirming very limited LC-PUFA biosynthetic activity for this teleost species. In this respect, liver of fish fed 15KO and 20KO displayed the highest contents of docosahexaenoic acid (DHA). The hepatic expression of genes of lipid and fatty acid metabolism, transcription factors, and antioxidant enzymes was investigated with many of the genes showing regulation by both dietary lipid and LC-PUFA contents. The present study showed promising results that suggested ABT juveniles can be on grown on inert dry feeds that supported good fish growth and the accumulation of the health-promoting fatty acid DHA. Further studies are required in order to fully elucidate lipid and fatty acid requirements of this iconic species regarding dietary sources and production costs., SI

The Atlantic Bluefin tuna is an emblematic species which is feeding the Mediterranean human populations for centuries. In the last two decades its wild stocks have been severely overfished having been established important capture limits with the consequent reduction of the production. For satisfying the high market, it is essential the increase the bluefin tuna production coming from the self-sustained aquaculture. The Spanish Institute of Oceanography (IEO) has recently built a land-based large scale facility (ICRA) for the control of the reproduction of this species, capable of hosting big size breeders. This facility is near the already existing IEO Aquaculture facility in Mazarrón, (Murcia, SE Spain), devoted to the research on Atlantic Bluefin tuna larval rearing and juveniles production. Both facilities are a model of how research centres of excellence can enhance cooperation to generate new knowledge on performance that can be transferred directly to operators and provide the technical basis needed to take the sector forward. Co-funded by European Regional Development Funds (FEDER) and Spanish Institute of Oceanography (IEO)

Hasta el momento actual, el cultivo integral de atún rojo se inicia con la recogida de puestas de huevos embrionados procedentes de reproductores ubicados en jaulas flotantes en el mar. Uno de los graves problemas que plantea esta técnica es que los huevos vienen acompañados de huevos de otras especies que también se están reproduciendo en el área. Algunas de estas especies tienen fases larvarias piscívoras y alcanzan dicha fase antes que el propio atún, y por tanto depredan sobre él. La presencia de algunas de estas especies en los cultivos larvarios de atún rojo supone una mortalidad por depredación que reduce en gran medida la producción de juveniles de esta especie. En este trabajo se ha testado la posibilidad de eliminar estos huevos separándolos por flotabilidad ya que en la mayoría de los casos es menor que la de los huevos de atún rojo, ya que estos tienen una flotabilidad especialmente elevada. Justificación, Until present time, Atlantic bluefin tuna full life cycle aquaculture in Europe has started with the collection of fertilized eggs from breeders located in floating cages in the sea. One of the most relevant issues of that technique is the presence of eggs of not desired fish species with concomitant reproduction season mixed with tuna, which due to their fast development can be able to predate bluefin tuna larvae at their earlier stages. This fact seriously threatens the survival of bluefin tuna larvae and juveniles production. In the present study, the possibility of doing away with these undesirable eggs by using a differential buoyancy technique has been tested, which in most cases it has been proved to be inferior to the buoyancy of bluefin tuna eggs.

Se ha realizado un video divulgativo del proyecto que puede visualizarse en: https://www.youtube.com/watch?v=X_fd8‐K1Xf8&t=13s Objetivos del proyecto BIACOP Mediante la utilización de sistemas de ecosondas y visión estereoscópica, el proyecto BIACOP propone dos objetivos principales: Objetivo 1: Desarrollo de un sistema totalmente automático para estimar la distribución de tallas de los atunes en jaulas flotante Objetivo 2: Desarrollo de una herramienta con ecosondas y sistemas estereoscópico para la de estimación de número de individuos y biomasa total de atún rojo durante el proceso de transferencia entre jaulas de transporte y de engrase, desde una perspectiva ventral., Los objetivos del proyecto han sido cumplidos en su totalidad y se han alcanzado resultados altamente prometedores, combinando tecnología de sensores acústicos y ópticos, que muestran que las técnicas desarrolladas posibilitan el conteo de los atunes en transferencias y su tallaje tanto en jaulas como en transferencias. Nuestros desarrollos permiten el tallaje y conteo con resultados independientes de fatigas y condiciones humanas.

These findings indicate that protein synthesis increase in proportion to the flexion stage which is strongly associated with the development of the digestive system and therefore the increase in the nutritional condition. Ontogenetic differences in the RNA and DNA content will be discussed in more detail. Also, the pattern obtained for Atlantic bluefin tuna larva will be compared with those of other species.

Después de casi veinte años investigando sobre el cultivo del atún rojo, se ha conseguido cerrar su ciclo en cautividad, aunque es necesario reducir la alta mortalidad larvaria para que su producción llegue a ser rentable. Dos posibles soluciones serían: mejorar el perfil nutricional de los rotíferos utilizados, enriqueciéndolos con minerales o vitaminas, o mejorar el cultivo de copépodos para abaratar los costes de su producción. En el experimento 1, se enriquecieron rotíferos con selenio o vitamina E a corto y largo plazo. Se estudió su efecto en el crecimiento poblacional y la cantidad que pueden llegar a retener. Se observó que ninguno de los enriquecedores utilizados influyeron en el crecimiento de los rotíferos y que la concentración de Se retenida tras 3 horas de enriquecimiento aumentaba de forma lineal con la cantidad administrada, obteniéndose valores entre 0,04 ± 0,048 y 25,57 ± 12,34 mg/kg PS. Por último, se vio que al añadir diariamente la misma cantidad de selenio (0,33 mg/106rot.) al medio de cultivo, la concentración de este elemento en los rotíferos se mantenía constante (0,85 ± 0,15 mg/kg PS). En el experimento 2, se alimentaron copépodos con distintas microalgas y una pasta comercial de Chlorella. A pesar de que se obtuvieron datos muy dispares, se podría decir que utilizando el alga Rhodomonas baltica se obtuvo un mayor número de huevos y una mayor supervivencia., After almost twenty years researching about the bluefin tuna cultivation, it has been possible to complete its life cycle in captivity, although it is necessary to reduce the high larval mortality to make its production profitable. Two possible solutions would be: improve the nutritional profile of the rotifers, enriching them with minerals or vitamins, or improve copepod culture to reduce the costs of their production. In the experiment 1, rotifers were enriched with selenium or vitamin E during a short and long term. It was studied its effect on population growth and the amount they can retain. It was observed that none of the enrichers used influenced rotifer´s growth, and that the concentration of Se retained after 3 hours of enrichment increased linearly with the amount administrated, obtaining values between 0,04 ± 0,048 and 25,57 ± 12,34 mg/kg DW. Finally, It also was observed that the concentration of Se in the rotifers was maintained constant (0,85 ± 0,15 mg/kg DW) when the same amount of this element (0,33 mg/106rot.) was added daily to the culture medium. In the experiment 2, copepods were fed with different microalgae and a commercial paste of Chlorella. Despite the disparity of the data obtained, it could be said that a higher number of eggs and a higher survival rate was obtained using the alga Rhodomonas baltica.

In larval culture, long light photoperiod regimes are used to maximize ingestion rates by increasing the accessibility to prey and therefore enhancing larval growth. Intermittent feeding could provide a viable alternative to the commonly used continuous feeding regimes that aim to improve larval growth and survival. In this study, we investigate the effect of alternating light/darkness regimes with intermittent feeding on the growth and survival of piscivorous larvae of two Scombrid species: Atlantic bonito, Sarda sarda (Bloch, 1793) and Atlantic bluefin tuna Thunnus thynnus (Linnaeus, 1758). First we tested if the manipulation of a light regime generated intermittent feeding by analyzing the larval stomach content. Then, we conducted two laboratory experiments to identify the best alternating light regime that maximized larval growth and survival by comparing the results to those obtained using continuous light regimes. The manipulation of light was optimized to provide intermittent feeding opportunities for the larvae, since we discovered a clear interruption of feeding in darkness. An increase in specific ingestion throughout the day was observed in all experiments, reaching a maximum peak late in the day. Bluefin tuna larval growth rates were similar despite different alternating conditions whereas the bonito larvae grew best when provided with light at three hour intervals. In both species, growth under alternating light conditions was similar to the 15 hours continuous light treatment. No differences between the alternating and the continuous light treatments were observed in terms of their survival. Our results suggest that alternating light/feeding periods may have a beneficial effect on ingestion rates; possibly because feeding is less satiation-limited, metabolic costs are lower; or food digestion is more efficient under these conditions. Changes in the light regime, that result in pulse feeding, can thus be an optimal strategy to increase growth at no apparent survival cost in bonito or bluefin tuna larval cultures., SI

Este proyecto tiene como objeto final la configuración de un sistema que proporcione la estimación del número y la biomasa de atunes de forma automática en entornos semi-controlados. Para ello se llevarán a cabo desarrollos, que configuren la integración de los datos obtenidos por sistemas acústicos y ópticos en dicho entornos. En concreto este proyecto pretende: - Desarrollar un sistema automático que sea capaz de estimar la distribución de tallas y pesos de los atunes que habitan en una jaula flotante. - Desarrollar un sistema automático que cuantifique las capturas, tanto del número de individuos capturados como de la distribución de sus tallas y pesos, y por tanto de la biomasa total, durante el proceso de transferencia de los atunes entre jaulas. Para conseguir los objetivos será necesario realizar: 1. Una selección de componentes hardware y software que tengan un rendimiento apropiado para adquirir datos acústicos y ópticos en el medio marino 2. Fases de adquisición y almacenamiento de datos acústicos y ópticos para configurar bases de datos cuyo objetivos serán: a) evaluar las diferentes versiones del sistema durante la fase de desarrollo b) confeccionar estadísticas de valores y parámetros relacionales 3. Fases de pruebas y validación de los equipos y métodos desarrollados en situaciones reales de funcionamiento 4. Diseño e integración de aquellos elementos hardware del sistema acústico y del sistema de visión por computador que resulten necesarios para la configuración del sistema final 5. Implementación y desarrollo de algoritmos, tanto para el procesamiento de los datos acústicos, como para el procesamiento y análisis de las imágenes adquiridas, necesarios para el funcionamiento de la aplicación y del sistema final propuesto Las ventajas del sistema resultante frente a los ya existentes son: 1. Sistema totalmente automático: El sistema detectará de forma automática instantáneas adecuadas de los atunes en las que sea correcto adquirir valores biométricos de los mismos para caracterizar su talla y su peso. Para ello será necesario el procesamiento y sincronización de la señal acústica y óptica. 2. Sistema de gran precisión: El trabajar con dos tipos de datos (acústico y óptico) sobre los mismos individuos nos permite verificar los valores estimados sobre sus características biométricas y conseguir una mayor precisión y ajuste. 3. Sistema tolerante con aguas turbias o con poca transparencia: Los sistemas acústicos obtienen información con independencia de la turbidez o claridad del agua. El trabajar con datos acústicos nos permite dar referencias al sistema de visión sobre distancias de individuos detectados, consiguiendo una mejor aproximación del procesamiento de imágenes realizado. 4. Sistema respetuoso con el bienestar animal y su desarrollo: En este proyecto se propone un sistema no invasivo. Nuestro sistema estará dotado únicamente de los elementos tecnológicos y acústicos necesarios para extraer datos y del soporte de los mismos, y en todo caso del sistema de sujeción que confiera la necesaria estabilidad de los mismos. 5. Sistema para ventanas de transferencia de tamaño adecuado al atún rojo: La tecnología acústica proporciona información complementaria a los sistemas ópticos. La utilización de ambas tecnologías permitiría complementar la utilización de un sistema óptico estereoscópico, y mejorar la amplitud del campo efectivo de nuestro sistema, pudiendo prescindir de la información estereoscópica en los casos en que las distancias de trabajo dificultan su aplicación, o incluso ofrecer información puramente acústica. RESULTADOS La medida estereoscópica ventral automatizada de atunes en jaulas y transferencias ofrece nformación biométrica sin errores accidentales asociados a la medida del operador. Nuevas relaciones biométricas pueden estudiarse a partir de las herramientas desarrolladas. La utilización de una estructura de paso entre jaulas posibilita la instalación de sensores en posiciones estables y la repetibilidad de las condiciones de medida El uso de un transductor acústico en las transferencias ofrece el conteo automático con errores menores al 10 % Comisión Europea mediante la decisión ejecutiva de la Comisión de la UE de 10 de julio de 2013 (2013/410/UE), relativa a una participación financiera de la Unión en los programas de control de la actividad pesquera realizados por los estados miembros.

The study demonstrated that copepods were a better live prey for first feeding ABT larvae based on growth and survival. Differences in the expression patterns of lipid metabolism genes were observed between the two trials. Some of the responses in lipid gene expression could be due to dietary lipid and fatty acid composition, but there was no obvious direct correlation between gene expression patterns and growth or survival. Differences in performance and metabolism among larval groups between the trials could also partly reflect differences in broodstock nutrition in the two trials. Hence, further studies are required to investigate lipid requirements, lipid accumulation and metabolism during development of ABT larvae. Special importance should be given to the expression analysis of genes related to lipid metabolism and its regulation, combined with biochemical studies of tuna lipid metabolism in order to develop optimal feeds to facilitate the commercial culture of this iconic species.

Los escómbridos comprenden una familia de peces pelágicos con un gran potencial para la acuicultura debido a su rápido crecimiento y alto valor comercial. Con la excepción del Atún rojo del pacífico (Thunnus orientalis), especie en la que se ha completado el ciclo vital, la acuicultura integral de las especies pertenecientes a la familia de los escómbridos o es inexistente o se basa en la captura de especímenes adultos. Esta tesis pretende establecer las bases de la reproducción y cultivo larvario de dos especies de escómbridos: el atún rojo del Mediterráneo y el bonito Atlántico. Los objetivos a alcanzar pueden resumirse en tres: a) Desarrollar una tecnología de cultivo que permita capturar adultos, establecer las condiciones adecuadas para su mantenimiento y maduración en cautividad, recolectar huevos fertilizados de buena calidad y finalmente llegar a cerrar su ciclo en cautividad. b) Describir el desarrollo embrionario del Bonito Atlántico y el Atún rojo del Atlántico y evaluar el efecto de la temperatura sobre el mismo. c) Determinar la composición lipídica de huevos y larvas y estudiar su composición lipídica (con especial referencia a PUFAs) a lo largo del desarrollo, ensayando diversos alimentos y cuantificando los resultados obtenidos La tecnología para capturar y mover a jaulas atunes rojos está bien desarrollada, así que se ha focalizado en capturar, manipular, mover a tanques y adaptar a la cautividad en condiciones controladas escómbridos pequeños como el AB. Se ha logrado la maduración y puesta de AB y ABFT durante cuatro años, exponiéndose los resultados de número de huevos obtenidos, extensión de la época de puesta y datos biométricos como diámetro del huevo, número de gotas de grasa y tasa de eclosión. Cuando ha sido posible se ha determinado la fecundidad relativa de las hembras, y se ha conseguido cerrar el ciclo del bonito en cautividad. En el caso del ABFT estamos próximos a lograrlo, ya que actualmente existen en Murcia adultos de más de 20 kg (clase de edad 3+) nacidos en el Instituto Español de Oceanografía y engordados primero en las instalaciones del grupo Ricardo Fuentes y posteriormente en las jaulas de Fortuna Mare. Se ha descrito el desarrollo embrionario de los huevos de AB y ABFT y se ha estudiado el efecto de la temperatura sobre los mismos, estableciendo las más propicias para el cultivo. Además se ha establecido la composición lipídica de los huevos fecundados y su evolución a lo largo del desarrollo embrionario y la etapa de alimentación endógena de las larvas. Con relación al cultivo larvario, se han comparado los resultados obtenidos en ABFT con dos presas diferentes en cuanto a crecimiento, supervivencia y composición lipídica, con especial referencia a los ácidos grasos poliinsaturados y dentro de estos ácido docosahexaenoico y a la relación docosahexaenoico/eicosapentaenoico, considerada esencial para el éxito del cultivo. Asimismo se ha estudiado el comienzo de la fase piscívora de ambas especies, determinando el momento más adecuado para su inicio. Por último se incluye un proyecto biológico realizado para la construcción de una instalación en tierra de ABFT. Este proyecto es pionero en Europa y alberga el mayor tanque de cultivo de atún. El mantenimiento de reproductores en tierra es fundamental para desarrollar una acuicultura integral de ABFT, ya que permitirá independizarse totalmente de las condiciones meteorológicas y alargar su época de reproducción mediante el control del foto y termoperiodo. Esta tesis pretende contribuir a desarrollar la acuicultura de estas especies, sentando algunas bases para la reproducción y cultivo larvario. Aún queda camino por recorrer, pero la acuicultura integral comercial del AB, y especialmente del ABFT, será una realidad en poco tiempo., Scombridae comprise a family of pelagic fish species with a great potential for aquaculture due to fast growth rates and high commercial values. In the last years, it has been complete the life cycle in captivity of Pacific bluefin tuna (Thunnus orientalis), but with this exception, integral Aquaculture of species belonging to Scombriae does not exist or is capture-based. This thesis pretends to determine the basis for reproduction and larval rearing of two species of scombrids: Atlantic bluefin tuna (ABFT), Thunnus thynnus, and Atlantic bonito (AB), Sarda sarda. Objectives can be summarized in three targets: a) To develop a culture technology that allow us to capture adult fishes, establish adequate conditions to maintenance and reproduce them in confinement, collect fine quality eggs and finally to complete their cycle in controlled conditions in captivity b) To describe embryonic development of AB and ABFT and to determine the effect of temperature on it. c) To determine lipid composition of eggs and larvii (with special reference to PUFAs) and to study their evolution throughout larvae development, feeding with different live preys diets and to quantify obtained results. Technology to capture and move to the cages bluefin tunas is well developed, so this thesis focused on capturing, handling,moving to tanks and adapting to confinement in controlled conditions smaller scombrids as AB. Maturation and spontaneous spawning of AB and ABFT have been achieved during four years, and number of fertilized collected eggs, spawning season extension and some biometrics as egg diameter, number of oil globules and hatching rate are reported. When possible, relative fecundity had also been determined. Finally it had possible to complete the life cycle of bonito in confinement in controlled conditions. With regards to ABFT, completion of life cycle is close to be achieved so that nowadays there are adults averaging more than 20 kg belonging to age class 3+, born in IEO facilities and fattened during two years in Ricardo Fuentes and then in Fortuna mare cages. Embryonic development of AB and ABFT has been described and the effect of temperature has been studied, determining more adequate temperatures to culture. Lipid composition of fertilized eggs and their evolution throughout embryonic development and endogenous feeding stage have also been determined. With regards to larval rearing obtained results with two different live preys diets used as food to ABFT were compared, not only in growth and survival rates but also in lipid composition with special reference to polyunsaturated fatty acids, mainly docosahexanoic acid and docosahexanoic/eicosapentanoic acids rate, which is considered to be crucial for success in larval rearing. Moreover onset of piscivorous stage has been studied in both species, and the better moment to begin yolk sac larvae feeding has been established. In addition, a biological project to build a land based facility to ABFT is included. This project is pioneer in Europe, and it includes greater existing tank to culture tunas in the world. Maintenance of broodstocks in land based facilities is basic to develop integral aquaculture of ABFT, so it will allow us to be fully independent of weather conditions and to extend spawning season by control of photo and thermoperiod. Research showed in this thesis pretend to contribute to develop aquaculture of these species, setting some basis to reproduction and larval rearing. In spite further research must be done, integral commercial aquaculture of AB and mainly ABFT will become a reality shortly.

Se ha analizado la incorporación de isótopos estables y ácidos grasos en larvas de atún rojo (Thunnus thynnus) alimentadas con rotíferos enriquecidos con Algamac® y Origreen®. Los factores de enriquecimiento larva-rotífero para el isótopo de nitrógeno (15N/14N, δ15N) y de carbono (13C/12C, δ13C) mostraron valores diferentes en función de la dieta suministrada. Asimismo, se encontraron diferencias en los perfiles de ácidos grasos de las larvas, debidas a la dieta, salvo para el 18:1n-9 y el DHA. No se encontraron diferencias significativas en el crecimiento., Incorporation of nitrogen/carbon stable isotopes and total lipid fatty acids was analysed in Atlantic Bluefin tuna (Thunnus thynnus) larvae fed with rotifers enriched with Algamac® and Origreen®, respectively. Larvae-rotifer enrichment factors for nitrogen (15N/14N, δ15N) and carbon (13C/12C, δ13C) showed significant different values according to diet composition. Moreover, significant differences were also observed in larvae total lipid fatty acid profiles with the exceptions of 18:1n-9 and DHA. No growth significant differences were found.

Bone resorption in the first spine of the first dorsal fin of Atlantic bluefin tuna (ABFT) has long been considered for age estimation studies. In the present paper spine bone resorpion was assessed in wild (aged 1 to 13 years) and captive-reared (aged 2 to 11 years) ABFT sampled from the Mediterranean Sea. Total surface (TS), solid surface (SS) and reabsorbed surface (RS) were measured in spine transverse sections in order to obtain proportions of SS and RS. The spine section surface was found to be isometrically correlated to the fish fork length by a power equation. The fraction of solid spine bone progressively decreased according to a logarithmic equation correlating SS/TS to both fish size and age. The values ranged from 57% in the smallest examined individuals to 37% in the largest specimens. This phenomenon was further enhanced in captive-reared ABFT where SS/TS was 22% in the largest measured specimen. The difference between the fraction of SS of wild and captive-reared ABFT was highly significant. In each year class from 1- to 7-year-old wild specimens, the fraction of spine reabsorbed surface was significantly higher in specimens collected from March to May than in those sampled during the rest of the year. In 4-year-old fish the normal SS increase during the summer did not occur, possibly coinciding with their first sexual maturity. According to the correlations between SS/TS and age, the rate of spine bone resorption was significantly higher, even almost double, in captive-reared specimens. This could be attributed to the wider context of systemic dysfunctions occurring in reared ABFT, and may be related to a number of factors, including nutritional deficiencies, alteration of endocrine profile, cortisol-induced stress, and loss of spine functions during locomotion in rearing conditions., SI

En prensa

Los escómbridos comprenden una familia de peces pelágicos con un gran potencial para la acuicultura debido a su rápido crecimiento y alto valor comercial. Con la excepción del Atún rojo del pacífico (Thunnus orientalis), especie en la que se ha completado el ciclo vital, la acuicultura integral de las especies pertenecientes a la familia de los escómbridos o es inexistente o se basa en la captura de especímenes adultos. Esta tesis pretende establecer las bases de la reproducción y cultivo larvario de dos especies de escómbridos: el atún rojo del Mediterráneo y el bonito Atlántico. Los objetivos a alcanzar pueden resumirse en tres: a) Desarrollar una tecnología de cultivo que permita capturar adultos, establecer las condiciones adecuadas para su mantenimiento y maduración en cautividad, recolectar huevos fertilizados de buena calidad y finalmente llegar a cerrar su ciclo en cautividad. b) Describir el desarrollo embrionario del Bonito Atlántico y el Atún rojo del Atlántico y evaluar el efecto de la temperatura sobre el mismo. c) Determinar la composición lipídica de huevos y larvas y estudiar su composición lipídica (con especial referencia a PUFAs) a lo largo del desarrollo, ensayando diversos alimentos y cuantificando los resultados obtenidos La tecnología para capturar y mover a jaulas atunes rojos está bien desarrollada, así que se ha focalizado en capturar, manipular, mover a tanques y adaptar a la cautividad en condiciones controladas escómbridos pequeños como el AB. Se ha logrado la maduración y puesta de AB y ABFT durante cuatro años, exponiéndose los resultados de número de huevos obtenidos, extensión de la época de puesta y datos biométricos como diámetro del huevo, número de gotas de grasa y tasa de eclosión. Cuando ha sido posible se ha determinado la fecundidad relativa de las hembras, y se ha conseguido cerrar el ciclo del bonito en cautividad. En el caso del ABFT estamos próximos a lograrlo, ya que actualmente existen en Murcia adultos de más de 20 kg (clase de edad 3+) nacidos en el Instituto Español de Oceanografía y engordados primero en las instalaciones del grupo Ricardo Fuentes y posteriormente en las jaulas de Fortuna Mare. Se ha descrito el desarrollo embrionario de los huevos de AB y ABFT y se ha estudiado el efecto de la temperatura sobre los mismos, estableciendo las más propicias para el cultivo. Además se ha establecido la composición lipídica de los huevos fecundados y su evolución a lo largo del desarrollo embrionario y la etapa de alimentación endógena de las larvas. Con relación al cultivo larvario, se han comparado los resultados obtenidos en ABFT con dos presas diferentes en cuanto a crecimiento, supervivencia y composición lipídica, con especial referencia a los ácidos grasos poliinsaturados y dentro de estos ácido docosahexaenoico y a la relación docosahexaenoico/eicosapentaenoico, considerada esencial para el éxito del cultivo. Asimismo se ha estudiado el comienzo de la fase piscívora de ambas especies, determinando el momento más adecuado para su inicio. Por último se incluye un proyecto biológico realizado para la construcción de una instalación en tierra de ABFT. Este proyecto es pionero en Europa y alberga el mayor tanque de cultivo de atún. El mantenimiento de reproductores en tierra es fundamental para desarrollar una acuicultura integral de ABFT, ya que permitirá independizarse totalmente de las condiciones meteorológicas y alargar su época de reproducción mediante el control del foto y termoperiodo. Esta tesis pretende contribuir a desarrollar la acuicultura de estas especies, sentando algunas bases para la reproducción y cultivo larvario. Aún queda camino por recorrer, pero la acuicultura integral comercial del AB, y especialmente del ABFT, será una realidad en poco tiempo., Scombridae comprise a family of pelagic fish species with a great potential for aquaculture due to fast growth rates and high commercial values. In the last years, it has been completed the life cycle in captivity of Pacific bluefin tuna (Thunnus orientalis), but with this exception, integral Aquaculture of species belonging to Scombriae does not exist or is capture-based. This thesis pretends to determine the basis for reproduction and larval rearing of two species of scombrids: Atlantic bluefin tuna (ABFT), Thunnus thynnus, and Atlantic bonito (AB), Sarda sarda. Objectives can be summarized in three targets: a) To develop a culture technology that allow us to capture adult fishes, establish adequate conditions to maintenance and reproduce them in confinement, collect fine quality eggs and finally to complete their cycle in controlled conditions in captivity b) To describe embryonic development of AB and ABFT and to determine the effect of temperature on it. c) To determine lipid composition of eggs and larvii (with special reference to PUFAs) and to study their evolution throughout larvae development, feeding with different live preys diets and to quantify obtained results. Technology to capture and move to the cages bluefin tunas is well developed, so this thesis focused on capturing, handling, moving to tanks and adapting to confinement in controlled conditions smaller scombrids as AB. Maturation and spontaneous spawning of AB and ABFT have been achieved during four years, and number of fertilized collected eggs, spawning season extension and some biometrics as egg diameter, number of oil globules and hatching rate are reported. When possible, relative fecundity had also been determined. Finally it had possible to complete the life cycle of bonito in confinement in controlled conditions. With regards to ABFT, completion of life cycle is close to be achieved so that nowadays there are adults averaging more than 20 kg belonging to age class 3+, born in IEO facilities and fattened during two years in Ricardo Fuentes and then in Fortuna mare cages. Embryonic development of AB and ABFT has been described and the effect of temperature has been studied, determining more adequate temperatures to culture. Lipid composition of fertilized eggs and their evolution throughout embryonic development and endogenous feeding stage have also been determined. With regards to larval rearing obtained results with two different live preys diets used as food to ABFT were compared, not only in growth and survival rates but also in lipid composition with special reference to polyunsaturated fatty acids, mainly docosahexanoic acid and docosahexanoic/eicosapentanoic acids rate, which is considered to be crucial for success in larval rearing. Moreover onset of piscivorous stage has been studied in both species, and the better moment to begin yolk sac larvae feeding has been established. In addition, a biological project to build a land based facility to ABFT is included. This project is pioneer in Europe, and it includes greater existing tank to culture tunas in the world. Maintenance of broodstock in land based facilities is basic to develop integral aquaculture of ABFT, so it will allow us to be fully independent of weather conditions and to extend spawning season by control of photo and thermoperiod.

A couple of trials to test the effects of photoperiod and light intensity on growth and survival of Atlantic bluefin tuna larva were carried out. With regard to light intensity, no significant differences were found between 500, 1000 and 2000 luxes. With regards to photoperiod meanwhile long photoperiods lead to a greater growth, intermediate photoperiods (16hL:8hD and 12hL:12hD ) improve significantly survival rates., Research Project ATAME (CT M2011-29525-C04).

The aim of this study was to determine whether mortality observed during the larval development of reared bluefin tuna (Thunnus thynnus) could be related to improper expression profiles of key genes involved in digestive or anti-oxidant response capabilities. Tuna larvae were sampled at hatching, 2, 5, 10, 15 and 20 dph (days post hatching) for the relative quantification of transcripts encoded by genes involved in digestive (trypsinogen 1 [TRYP1], alpha-amylase [AMY], aminopeptidase N [ANPEP]) and antioxidant (catalase 32 [CAT]) functions. The levels of expression of ANPEP related to the development and maturation of intestinal function increased from 5 to 20 dph. Furthermore, AMY and TRYP1 genes which are pancreatic enzymes implicated in carbohydrate and peptide digestions exhibit a typical peak of expression at 5 and 15 dph respectively. The antioxidant enzyme, CAT, exhibited higher mRNA levels during the first stage of larval development. In conclusion, our investigation indicates that the expression of genes involved in digestive and antioxidant physiological processes followed typical patterns which could not explain high mortality rate observed during the first stage of larval development, SI

Se ha estudiado el desarrollo ontogénico de las larvas de atún rojo, Thunnus thynnus, especialmente el momento de la flexión de la notocorda y su relación con la temperatura. El cultivo larvario se ha realizado en tanques replicados en un medio controlado. Los resultados contribuyen a mejorar el conocimiento existente sobre el desarrollo larvario del atún rojo en la naturaleza., Este trabajo se ha realizado en el marco del proyecto ATAME-IEO (Plan Nacional de I+D+i 2008-2011).

Una secuencia ontogénica de larvas y juveniles de atún rojo (Thunnus thynnus) cultivados mediante técnicas de acuicultura en 2012, fue transparentado y teñido para determinar la condrogénesis craneal normal. (y el inicio de la osificación) en individuos de entre 0 y 90 días después de la eclosión (DDE). Entre 0 y 20 DDE la longitud estándar aumenta lentamente mientras que la longitud de la cabeza aumenta de forma más rápida, entre 0 y 7 DDE. El inicio de la condrogénesis se produce tan pronto como a 1 DDE y todos los cartílagos craneales están presentes a 16 DDE. Asociadas a la temprana condrogénesis de seis de esos cartílagos, se han identificado diez tipos de malformaciones craneales. Tales malformaciones podrían potencialmente ser las responsables de más del 34% de la mortalidad antes de 24 DDE. An ontogenetic sequence of the Atlantic Bluefin tuna (Thunnus thynnus) larvae and juveniles reared in aquaculture conditions in 2012, was cleared and stained to determine normal cranial chondrification (and onset of ossification) for specimens ranging from 0 to 90 days post-hatching (dph). From 0 to 20 dph, standard length increases slowly while head length increases most rapidly between 0 and 7 dph. The onset of chondrification is initiated as early as 1 dph, and all cranial cartilages are present by 16 dph. Associated with the early chondrification of six of these cartilages, ten types of cranial malformations have been identified. These malformations potentially account for more than 34% of the mortality before 24 dph. NSERC Research grant (RC)

During the first 2 years of larval rearing trials with Atlantic bluefin tuna, survival was a challenging issue. As bacterial colonization of the gut has been shown to play a key role for other species, we studied the profiles of the microbiota associated with individual larvae at different stages in three distant hatcheries. The Bacterial Community Profile (BCP) was quantified based on PCR-DGGE analyses of partial amplicons from 16S rDNA. Considerable individual variability in BCP was observed before onset of feeding, and the BCP did not show regular fluctuation during ontogenesis. Microalgae were added to the rearing tanks in two of the three hatcheries, but it was not possible to distinguish the effect of location from the effect of algal addition on BCP. In one hatchery, the larvae were reared either with algal addition or in mesocosm, but due to high individual variability, no significant difference in BCP was detected between the two groups. It was hypothesized that this variability was caused by differences in health, physiological status and developmental stage of the larvae. A practical conclusion from the study is the need to analyse a considerable number of individuals to reflect statistically significant differences between the microbial communities associated with rearing groups., Sí

7 FP EU Commission

In reproduction, genotyping of a large number of broodstock throughout the Mediterranean indicated that although the samples were not in Hardy-Weinberg equilibrium, there was no signal of a single population structure. In the broodstocks maintained in Spain we obtained spontaneous (without the use of any hormonal treatments), long-term and high fecundity and fertility spawning in both years, whereas in Malta fish spawned successfully after GnRHa treatment. Parentage contribution analysis demonstrated that 15 individuals were engaged in the majority of the crosses (460 out of 530 crosses) of the 2009 spawning season, with the remaining 10 fish being responsible for 13% of the crosses. It is important to note that both GnRHa implanted and control broodstocks participated in spawning. The study of puberty in captive BFT indicated that reproductive maturation begins after the 3rd year in males and the 4th in females, but rearing conditions may result in further delays. It was also shown that sexual dimorphic differences may exist in the regulation of puberty in this species. In the study of broodstock nutrition, the experimental diet resulted in a superior growth, higher GSI values and a more advanced gonadal development, and lower occurrence of apoptosis of vitellogenic oocytes. A method was developed for the monitoring of fish size and behavior in captivity. The closing of the life-cycle of bonito (Sarda sarda) in captivity was achieved. In 2010 and 2011, encouraging survival and growth results allow us to assume that BFT domestication should be feasible in a next future. But, larval rearing is still at the research stage and has not reached the status of a commercial level. Mesocosm and pseudo-green methodologies implemented in large tanks have been substantially improved as it is evident from the survival of the best rearing trials (2.5 -3 % at 25DPH). The knowledge base in larval and fingerlings rearing have been substantially documented both at the academic and at the rearing levels and gave us clear indications for improving rearing techniques and biological performances. The logistics of the eggs transport should be further considered (temperature management) to guarantee the smooth transfer of eggs. Currents, luminosity parameters and feed quality which have a significant effect on vision, feed intake, growth and survival as soon as the early stages have to be fine tune. It is still impossible to sustain an acceptable growth and survival without YSL post 17DPH whatever the rearing methods. So, even if weaning of juveniles (post 25DPH) on artificial diet was achieved, the later have to be improved and lead to better results. An alternative feed source as copepods could significantly contribute to enhance the early performances of the larvae while it seems that an early weaning window could lead to feeding sequence simplification. Artificial rearing methods (pseudo green and clear water) implemented in small tanks although improved still does not performed as mesocosm or pseudo-green ones in large tanks and have to be further improved to meet the needs of an experimental comprehensive/comparative approach. 376 YOTYs have been captured from the wild. 233 living fish have been placed in two floating cages for the feeding trials. A technique for transporting from the wild and from the cages, to the land based facilities has been successfully developed. The stomach contents analysis of wild dead fish shown that juveniles are opportunistic and generalist feeders. The tuna feed formulation must include appropriate ingredients in order to achieve higher dietary amino acid and protein concentrations, lower total lipid content, higher dietary n-3 concentrations and higher vitamin C and E concentrations. A dry food has been developed and tested in wild and full reared juveniles. Dissemination activities were carried out including specialized sessions at the EAS meeting in Rhodes and a stakeholder workshop in Madrid., 7º FP EU Commission

En el marco del proyecto SELFDOTT, el IEO han desarrollado técnicas para el cultivo larvario y la producción de juveniles de atún rojo (Thunnus thynnus). Uno de los mayores problemas encontrados es la alta mortalidad (>98%) de las larvas y los juveniles. Para evidenciar las causas potenciales de dicha mortalidad, se ha estudiado la aparición de malformaciones post-craneales durante la esqueletogénesis del desarrollo de larvas y juveniles de atún rojo entre 0 y 90 días después de la eclosión (DDE). Las malformaciones esqueléticas pudieran ser las responsables de parte de la mortalidad. En las primeras fases del desarrollo son frecuentes las malformaciones generales (lordosis, escoliosis, cifosis…) y puntuales (fusiones, compresiones…). Las malformaciones esqueléticas de la columna vertebral afectan al 70% de los peces: 32% con malformaciones puntuales en los centra, 36% con malformaciones en los arcos y 74% con malformaciones generales. Se han identificado dos periodos principales en los que aparecen las malformaciones: el primero, caracterizado por la aparición significativa de malformaciones puntuales en los arcos que se corresponden con el principio de la condrificación (alrededor de 11 DDE) y un segundo periodo caracterizado por la presencia sustancial de malformaciones generales al inicio de la osificación (alrededor de 23 DDE)., In the framework of the SELFDOTT project, the IEO has developed a technique for the larval rearing and the juvenile production of the bluefin tuna (Thunnus thynnus). One of the major problems encountered is a high mortality (>98%) of larvae and juveniles. In order to address potential causes of mortality, we studied the appearance of postcranial skeletal malformations during skeletogenesis of farmed Bluefin Tuna from 0 to 90 days post-hatching (dph). The skeletal malformations could be responsible for part of the mortality. General (i.e., lordosis, scoliosis and kyphosis) and punctual (e.g., fusion, compression) postcranial malformations are frequent in early life stages. Skeletal malformations of the vertebral column affect 70% of fishes: 32% of specimens with punctual centra malformations, 36% specimens with punctual arches malformations, and 74% specimens with general malformations. Two major period of malformation appearance have been identified. The first period is characterized by the significant appearance of punctual arches malformations corresponding to the beginning of chondrification (ca. 11 dph). The second period is characterized by the substantial presence of general malformations at the beginning of ossification (ca. 23 dph)., Ricardo Fuentes e Hijos, S.A.

Una secuencia ontogénica de larvas y juveniles de atún rojo (Thunnus thynnus) cultivados mediante técnicas de acuicultura en 2012, fue transparentado y teñido para determinar la condrogénesis craneal normal. (y el inicio de la osificación) en individuos de entre 0 y 90 días después de la eclosión (DDE). Entre 0 y 20 DDE la longitud estándar aumenta lentamente mientras que la longitud de la cabeza aumenta de forma más rápida, entre 0 y 7 DDE. El inicio de la condrogénesis se produce tan pronto como a 1 DDE y todos los cartílagos craneales están presentes a 16 DDE. Asociadas a la temprana condrogénesis de seis de esos cartílagos, se han identificado diez tipos de malformaciones craneales. Tales malformaciones podrían potencialmente ser las responsables de más del 34% de la mortalidad antes de 24 DDE., An ontogenetic sequence of the Atlantic Bluefin tuna (Thunnus thynnus) larvae and juveniles reared in aquaculture conditions in 2012, was cleared and stained to determine normal cranial chondrification (and onset of ossification) for specimens ranging from 0 to 90 days post-hatching (dph). From 0 to 20 dph, standard length increases slowly while head length increases most rapidly between 0 and 7 dph. The onset of chondrification is initiated as early as 1 dph, and all cranial cartilages are present by 16 dph. Associated with the early chondrification of six of these cartilages, ten types of cranial malformations have been identified. These malformations potentially account for more than 34% of the mortality before 24 dph., NSERC Research grant (RC)

El atún rojo Thunnus thynnus (L., 1758) y el bonito atlántico, Sarda sarda (Bloch, 1793) son dos teleósteos pertenecientes a la familia Scombridae. Se trata de dos especies con pesquerías importantes que se capturan desde la antigüedad. Mientras que el bonito se encuentra en fase de investigación y no existen empresas que lo cultiven en la actualidad, el caso del atún rojo es diferente. A partir de los años 90 se inicia en el Mediterráneo el llamado engrase, que consiste en capturar ejemplares vivos mediante arte de cerco en las zonas de puesta, trasladarlos a granjas cercanas a la costa, alimentarlos durante varios meses con pequeños peces pelágicos ricos en materia grasa, y una vez sacrificados de forma rápida para evitar la formación de lactato, enviarlos al mercado, especialmente al japonés. Pero la sobreexplotación de las poblaciones naturales ocasionó que el Consejo Internacional para la Conservación del Atún Atlántico (ICCAT) estableciera en 1999 un sistema de cuotas para limitar ... Versión del editor

Co funded by 7FP of the EU, the SELFDOTT project (From capture based to self sustained aquaculture and domestication of Bluefin tuna, Thunnus thynnus) over the last four years, has been devoted to enhance the existing knowledge on the reproductive biology of this species in captivity and to establish the knowledge-base for larval rearing, as the development of suitable eco-friendly formulated feeds. It has been counted on the participation of 11 public research Institutions and 3 private Companies belonging to 8 European Countries. Wild broodstocks placed in sea cages in Spain and Malta were used to study the gametogenesis in captivity as well as to examine the influence of diet on reproductive maturation and gamete quality. Also wild juveniles, captured in Spain were adapted to captivity in cages for the development of artificial feeding. The bluefin tuna broodstocks maintained in Spain and in Malta have produced massive spawnings during the natural spawning season (several tens million fertilized eggs between June and July). These eggs were sent to research hatcheries in Spain, France, Malta, Greece and Israel to carry out the research on the larval rearing and provide the knowledge basis on early stage ontogeny. The larval rearings carried out in Spain performed the best survival rate. It is hoped that a good number of these juveniles produced in 2011, will reach adulthood in a minimum of four years and reproduce, therefore achieving for the first time the closing of the biological life cycle of this species in captivity. SELFDOTT GA 212797 FP7 EC

Co funded by 7FP of the EU, the SELFDOTT project (From capture based to self sustained aquaculture and domestication of Bluefin tuna, Thunnus thynnus) over the last four years, has been devoted to enhance the existing knowledge on the reproductive biology of this species in captivity and to establish the knowledge-base for larval rearing, as the development of suitable eco-friendly formulated feeds. It has been counted on the participation of 11 public research Institutions and 3 private Companies belonging to 8 European Countries. Wild broodstocks placed in sea cages in Spain and Malta were used to study the gametogenesis in captivity as well as to examine the influence of diet on reproductive maturation and gamete quality. Also wild juveniles, captured in Spain were adapted to captivity in cages for the development of artificial feeding. The bluefin tuna broodstocks maintained in Spain and in Malta have produced massive spawnings during the natural spawning season (several tens million fertilized eggs between June and July). These eggs were sent to research hatcheries in Spain, France, Malta, Greece and Israel to carry out the research on the larval rearing and provide the knowledge basis on early stage ontogeny. The larval rearings carried out in Spain performed the best survival rate. It is hoped that a good number of these juveniles produced in 2011, will reach adulthood in a minimum of four years and reproduce, therefore achieving for the first time the closing of the biological life cycle of this species in captivity. SELFDOTT GA 212797 FP7 EC

El atún rojo, Thunnus thynnus (L., 1758) es un pez emblemático que viene alimentando a las poblaciones del Mediterráneo desde hace milenios. Desde finales de los años 90, se viene realizando una actividad denominada “engrase” que consiste en la captura de ejemplares vivos en las áreas de puesta del Mediterráneo, aprovechando su migración sexual anual, su transporte hasta granjas cercanas a la costa, su alimentación con pequeños pelágicos durante un tiempo que suele variar entre 6 meses y más de un año, su sacrificio y su venta, fundamentalmente en el mercado japonés. Debido a la alta demanda de dicho mercado unido a los altos precios que en él se pagan, los stocks naturales se vieron sometidos a una fuerte sobreexplotación que puso en riesgo la supervivencia del recurso. Para evitar el colapso de esta especie, la Comisión Internacional para la Conservación del Atún Atlántico (ICCAT) estableció en 2008 un Plan de recuperación, limitando drásticamente sus capturas así como elevando la talla mínima y estableciendo periodos de veda entre otras recomendaciones. Esto ha llevado a que las producciones sean cada vez más reducidas y que la producción mediante técnicas de acuicultura integral, pueda hacer que las poblaciones naturales recuperen la estructura que tenían hace cientos de años, sin renunciar al consumo de su carne en la cantidad y calidad que requiere un mercado, cada vez más importante y selectivo. A este respecto y desde finales de los años 90 se vienen desarrollando diferentes proyectos de investigación (DOTT, REPRODOTT, SELFDOTT), cofinanciados por los Programas Marco de la Unión Europea, al objeto de desarrollar técnicas de cultivo que permitan en un futuro la producción independiente de atún rojo mediante técnicas de acuicultura, sin necesidad de capturar ejemplares en el medio natural., Proyecto SELFDOTT

Principales resultados, conclusiones y recomendaciones del Proyecto SELFDOTT (Del cultivo basado en capturas, a la acuicultura independiente y la domesticación del atún rojo, Thunnus thynnus.), Comisión Europea 7º PM (KBBE-2007-1-2-09 Cooperation Work Programme: Food, Agriculture and Fisheries, and Biotechnology), SI