Search

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

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.

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

The Spanish Institute of Oceanography owns a facility to reproduce Atlantic bluefin tuna (ABFT). This facility was built in 2015 and in August 2017, some fingerlings born in captivity were moved to this installation, and some wild tunas were added two months later. In November 2019, this batch consists in 69 2+ ABFT weighting 28 kg. Hopefully they can reach 40 kg at the beginning of June and spawn by the first time. Fertilized ABFT eggs were collected from cages owned by PisciAlba and obtained larvae were cultured in IEO facilities. At the end of July 2017, some fingerlings (Cultured batch –CB-, 2 gr mean weight) were move to ICRA facilities and placed in a 1000 m3 tank. At the end of September 2017 a total of 68 0+ ABFT fingerlings (Wild batch –WB-, 414 g mean weight), were captured from the Mazarron Bay and placed in another tank in ICRA. 4 months later, 81 tunas coming from both batches were weighted (2.5 kg mean weight), tagged and place together in a 3500 m3 tank. During all the time, temperature ranged between 17 and 27ºC, and food consisted in bait, mainly, Scomber scombrus (47% of the total food) and Clupea harengus (25%) but also Sardinella aurita, Engraulis encrasicolus and Scomber japonicus (11, 10 and 7% respectively). From February 2018 to November 2019, mortality has been 16.9% (10.9% in WB and 28.6% in CB) and tunas have grown to reach an average of 28 kg. Biomass in this moment is 1930 kg, which means a density of 0.55 kg/m3 . Feeding intake was high during the first six months (when tunas were smaller than 2.5 kg), but after this moment it has ranged between 2.5 and 7%, decreasing with the size of tunas and increasing slightly with higher temperatures (circles). Feeding conversion rate was quite stable during the period, averaging 13.8. According to forecast, at the end of next spring, average weight will be about 40 kg, with about 15 tunas greater than 50 kg. This means that they will be able to reproduce next summer if gonadal maturation develops properly.

Ventral measurements offer a wide spectrum of automation possibilities of BFT biomass estimations in cages and transfers - A synchronized stereoscopic video+echosounder system allows to asign biometrical data of bluefin tuna to a particular track in an echogram. - Ventral TS (partial TS, operationally defined) correlates with bluefin tuna length. - Partial TS vs Log(L) linear adjustments allow to predict tuna length from "blind" acoustic measurements even with single beam. Ongoing works and needs: -Measurements with broadband (chirped) echosounders and pulse compression technique from different aspects (new multibeam sonar campaings) - Better understanding of bluefin tuna structures contributions through measurements and numerical simulations (better knowledge of BFT anatomy and physiology, 3D biometrics, numerical simulations of TS) - New transfer tests to improve feasibility and technology/methodology cross-checking

Atlantic bluefin tuna is an emblematic scombrid species, but many physiological aspects during the larval stages are still unknown. The mechanisms of how fish larvae balance growth and activity are of great interest since metabolic costs are very high compared to juveniles and adults. However, there is a lack of information about metabolic costs in scombrid larvae. This lack of data is probably related to the challenges associated to larval handling before and during respirometry trials. In this study for the first time, we: i) estimate the relationship between routine metabolic rate and the larval dry weight (mass scaling exponent) at 26°C, ii) measure metabolism under light and darkness and iii) explore the influence of nutritional status (RNA:DNA ratio) on the inter-individual variability in metabolic rates. The relationship between metabolism and size (ranging from 0.6 to 23 mg) was near isometric (slope, b=0.99), in contrast to the allometric relationship observed in most species (b=0.87). Our results show no significant differences in oxygen consumption under light and darkness. A possible regulation (decrease) of their swimming activity with the consequent decrease in the oxygen consumption in light situations is discussed. Nutritional condition did not explain the inter-individual differences in oxygen consumption. This study first reports metabolic rates of Atlantic bluefin tuna larvae and discusses the challenges of performing bioenergetics studies with early life stages of Scombrids.

One of the most important bottleneck in the farming of Atlantic bluefin tuna (ABT) is the growth and survival during the larval rearing phase, mainly related with the diet quality. For the last ten years the Spanish Institute of Oceanography (IEO) in Mazarrón (Murcia, SE Spain) has developed a technique for ABT larval rearing and juvenile production. Taurine and selenium are essential water soluble compounds in live preys and inert diets for ABT larvae and juveniles. To know the importance of dietary taurine and selenium on growth and survival of ABT larvae, two experiments have been carried out with different taurine (Exp1) and selenium (Selplex® ) (Exp2) doses added to rotifers enriched with ALGAMAC 3050® . Both experiments were finished at 14 days post hatching. ABT fertilized eggs were collected from captive breeders spawning spontaneously in floating cages in the area. The eggs, transported to the IEO facilities, were quantified, cleaned, selected by buoyancy and distributed randomly in 1400 L fiber cylindrical glass tanks at a density of 10 ABT eggs per liter, whereas prey density was maintained at 5 rotifers per mL. Temperature ranges were: 24.0±0.5ºC and 26.0±0.5ºC for Exp1 and Exp2, respectively. Fig 1 shows the growth results in size for both experiments at 14 dph. Survival in both cases was close to 10% with no significant differences due to the different treatments. The lowest growth in size was observed in larvae fed dose 0 in both experiments Standard length average (mm ± confidence intervals) in Exp1 and Exp2 at 14 dph. Letters indicate statistically significant differences (95%)

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

La presente comunicación muestra las últimas técnicas desarrolladas por el equipo de cultivo de túnidos del Instituto Español de Oceanografía (IEO) para la captura, la manipulación, el transporte y la adaptación a instalaciones en tierra, de juveniles de atún rojo (Thunnus thynnus). La técnica utilizada para la captura fue usando anzuelos sin muerte. El uso de bolsas de plástico llenas de agua de mar resultó muy eficaz al eliminar prácticamente los daños por abrasión, y permitiendo medir, pesar, marcar/identificar con pit-tags, y obtener muestras para caracterización genética, de forma no traumática. The present communication shows the last techniques developed by the tunid aquaculture team belonging to Spanish Institute of Oceanography (IEO), for capturing, handling, transporting and adapting to the land based facilities of bluefin tuna juveniles (Thunnus thynnus). The technique for capturing was using barbless hooks. The use of soft plastic bags filled with sea water was very effective avoiding practically the injures due to the abrasion, allowing to obtain the size and weight, the tagging with pit-tags and the samples collection for genetic characterization, in a non traumatic way.

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.

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)

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

This article shows the most relevant results obtained between August 2017 and October 2018 with two batches of 0+ tunas: cultured tunas (CT) born in the IEO facilities in June 2017 and wild tunas (WT) captured in Mazarron Bay in September 2017. Fertilized ABFT eggs were collected from cages owned by PisciAlba and obtained larvae were cultured in IEO facilities. At the end of July 2017, 500 fingerlings (CT, 2 g average weight) were move to ICRA facilities on 29th July and placed in a 1000 m3 tank. At the end of September 2017 mean weight were 350 gr. In that moment, a total of 68 0+ ABFT fingerlings (WT, 414 g mean weight), were captured from the Mazarron Bay and placed in a 3500 m3 tank in ICRA. From this moment temperature ranged between 18 and 27ºC, and feeding consisted in bait, mainly Sardinella aurita and Scomber scombrus, but also Scomber japonicus, Engraulis encrasicolus and Clupea harengus. During November 2017, mortality increased in CT without any symptoms of infectious disease. 80 healthier CT were then moved to a greater tank (2500 m3 ) and in March 2018, when completely recovered, they were placed together with WT and both batches were cultured in the same tank up to now. During the 13 months period mortality observed in CT was high (close to 85%) while mortality in WT was lower than 15%. Growth was also slightly faster in WT. Feeding intake ranged during the whole period between 3 and 26%, and feeding conversion rate estimated was close to 12. At the end of October 2018 mean weight of population was 11 kg.

In conclusion, the present study suggests that ABT juveniles can be grown on inert extruded dry feeds that result in good fish growth and accumulation of the health-promoting fatty acid DHA. Furthermore, a blend of VO and KO could be used as the dietary lipid source up to a dietary lipid level of 15 % without affecting fish performance. The expression of lipid metabolism genes in ABT liver showed a different response to dietary lipid level/fatty acid profile, consistent with previous data indicating limited n-3 LC-PUFA biosynthetic capability in ABT. However, gene expression showed some differences between the two trials, which highlight how the genetic background of different batches of ABT juveniles could affect the regulation of metabolic gene expression and thus be a factor in weaning success. The expression of antioxidant enzymes was also altered by diet, related to dietary contents of antioxidant nutrients. Thus, further studies are required in order to fully elucidate the lipid and fatty acid requirements of this iconic species in relation to dietary sources and production costs

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.

There are still many issues that require to be solved in larval rearing of Atlantic bluefin tuna (Thunnus thynnus; ABT) to prevent “mass-mortality” during this developmental stage. Initial data related to the feeding sequence of ABT larvae suggested that mortality observed during the first stages of life could be due partly to nutritional deficiencies. Previous studies demonstrated that copepods appeared to be a superior live prey compared to rotifers during the first two 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 passed on to being fed on Artermia enriched with Algamac 3050® (RA) up to 18 dah. After 13 dah, larvae fed C grew more than those fed R although there were no 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 dietary contents. Indeed, there was no activation in the expression of the enzymes involved in LC-PUFA biosynthesis. However, the different live prey elicited regulation of transcription factor, digestive enzyme, lipid metabolism and oxidative stress genes. At 18 dah larvae fed CY and CA were the largest size with larvae fed RA displaying the lowest growth with no 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, RA-fed larvae showed the highest level of the intermediate product n-3 docosapentaenoate, which could be reflecting up-regulation in the biosynthetic pathway although this was not supported by gene expression data.

[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.

It has been demonstrated at least in the Murcia area, that the captive ABFT (Thunnus thynnus) for fattening activities reproduce actively in the farming cages in the natural spawning season (early June – middle July). Tens of millions of fertilized eggs coming from these cages had been collected in the last years and cultured in the facilities of the Spanish Institute of Oceanography (IEO) in Mazarrón (Murcia, SE Spain) and grown up to juveniles, demonstrating as well their viability. Taking into account that an ABFT female could spawn roughly hundred thousands of eggs per kg during all the spawning season and thousands of tones of ABFT adults have been farmed in the Murcia coast during the last years, the total fertilized eggs could reach hundreds of billions every year. Obviously the conditions in the Murcia coast are different of the natural spawning areas not only regarding the feeding availability but also the massive presence of many egg and larvae predators. It would be recommendable to carry out prospecting surveys in the aim to shed some light on this possible effect of farmed ABFT on the recruitment at least in Murcia.

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

Being bigger is not always the best option to survive and mortality rates do not always decline with increasing larval size. Smaller size at a given age could under certain condition and at certain stages of development confer a survival advantage on individual members of a larval cohort. References

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.

Our results show that the use of an acoustic transducer in transfers offers the possibility of performing an automatic counting with error below 10%, which is decreased to 1.2% after improving structure and algorithms. Moreover, the proposed procedure for automatic sizing using stereoscopic system achieved an accurate estimation of SFL distribution compared to true data from harvests, automatically measuring 20% of the fish

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.

The increase of dry weight, standard length and low incidence of skeletal anomalies clearly show that A. tonsa represents an optimal live food organism for tuna larvae.

In conclusion, and in agreement with our previous trial, the present study showed that copepods were a superior live prey for first feeding ABT larvae compared to enriched rotifers, as indicated by the higher growth and flexion in- dex achieved by larvae fed COP. All dietary treatments in the present study ap- peared to satisfy LC-PUFA requirements as no significant effects were observed in the expression of the genes related to the homeostasis and biosynthesis of the- se compounds (ppara, srebpl , lxr, rxr, fads2d6, and elovl5). Addition of organic selenium and a-tocopherol did not enhance larval performance, probably indicat- ing that the levels contained in copepods (0.4µg.g-1 and 170mg.kg-1, respective- ly) were sufficient to fulfil nutritional requirements.

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.

The bluefin tuna Thunnus thynnus (L., 1758) is a teleost fish belonging to the Scombridae family and is an emblematic species that has fed the Mediterranean populations for millennia. From the 90´s starts the process called «bluefin tuna fattening» which involves capturing live specimens by purse seiners in spawning areas, transferring them to nearby farms to the coast, feeding them for several months with small pelagic fish rich in fat and sent to market later, especially Japan. This activity led to severe exploitation of natural populations, risking the future of the fishery. To mitigate this, the International Council for the Conservation of Atlantic Tunas (ICCAT) established from 2007 a recovery plan, with a drastic limitation of catches and several conservation measures, which have made the fishery of Atlantic bluefin tuna one of the most regulated. Clearly, despite the undoubted positive effects on the recovery of the stock, limited catches will continue in the near future. Therefore, to ensure the supply of this iconic species in the quantity and quality required by an increasingly important and selective market, the bluefin tuna production has to come inevitably by techniques of integrated aquaculture completely independent of natural populations, such as it happens today with species such as gilthead sea bream, sea bass or turbot. This activity also promotes the recovery of natural stocks by reducing the fisheries pressure. The Oceanographic Centre of Murcia, belonging to Spanish Institute of Oceanography (IEO, has been developing for more than 10 years, techniques for the captive breeding of bluefin tuna and production of juveniles who have been subsequently raised to market size in floating cages companies the sector, within the framework of research projects with the IEO.

Since 2000 the Spanish Institute of Oceanography (IEO) is participating in several European research projects (DOTT, REPRODOTT, SELFDOTT) on Atlantic bluefin tuna (ABFT) culture with the aim of contributing of the Domestication of this species, for improving the productive process and reducing the pressure on the wild stock as it has already happened with other full cycle cultured species. Greatest efforts are being developed from 2011 in collaboration with the companies Caladeros del Mediterraneo and Fortuna Mare (FM). As a result of that, between 3 and 15 thousand tunas have been produced in the IEO experimental hatchery and transported every year to offshore cages placed in El Gorguel (Cartagena, SE Spain) and the Fortuna Mare company has nowadays some thousands of tunas belonging to 0+ to 4+ age classes. It is expected that oldest tunas start to spawn from next summer, closing by the first time the life cycle of ABFT in captivity.Results have been improved the last season, and more than 15.000 fingerlings 35-40 days old (average weight of 3 gr) have been produced in July-August by the IEO. They have been moved to three 25 m diameter cages (FM property) and some of them have been moved to a new IEO land based facility named ICRA (Infraestructure for the Control of the Reproduction of Atlantic bluefin tuna). The target of the ICRA is to hold a broodstock to control the reproduction in indoor big tanks, and some large tunas will be move in the upcoming months.

Juvenile production of Atlantic bluefin tuna (Thunnus thynnus) is characterized by high mortalities and low growth rates during the larval stage. Startfeeding of Bluefin tuna larvae in hatcheries depends on the traditional food organisms rotifers and Artemia nauplii (Biswas et al., 2006), and skeletal malformations have been observed in 70% of larvae and juveniles (Libert et al., 2013). When copepods are used as live food, the results are generally improved compared to the use of traditional live feed organisms (Evjemo et al., 2003), with higher survival, increased growth, normal development, earlier onset of ossification and less skeletal anomalies compared to larvae fed rotifers and Artemia (Imsland et al., 2006). The aims of this study were to describe the bone development in the Atlantic Bluefin tuna fed copepods, and to evaluate the effects of start-feeding with enriched rotifers or with cultivated copepods on skeletal deformities.

Es necesario desarrollar metodos de conservacion de huevos de copepodos para garantizar su disponibilidad para su uso en la acuicultura. En este estudio, huevos de Acartia tonsa han sido tratados con formaldehido, bronopol y peroxido de hidrogeno, y posteriormente conservados en agua a distinta salinidad. Tambien se ha comprobado la eficacia de la glicerina liquida como conservante al garantizar unas condiciones anaerobias. Durante el primer mes de conservacion el bronopol fue el mejor tratamiento siendo significativamente superior al grupo control. El empleo de peroxido de hidrogeno es ineficaz, ya que su empleo impide una tasa de eclosion superior al 5%. A partir del primer mes, el uso de la glicerina es significativamente mejor que el resto de tratamientos ya que garantiza una tasa de eclosion de aproximadamente el 25% durante al menos 120 dias. No se han encontrado diferencias significativas con el empleo de agua de distinta salinidad. Developing methods to preserve copepod eggs is necessary to ensure their availability for use in aquaculture. In this study, Acartia tonsa eggs have been treated with formaldehyde, bronopol and hydrogen peroxide, and then stored in water at different salinities. We have also tried the efficacy of liquid glycerin as a preservative because it ensures anaerobic conditions. During the first month of conservation, the use of bronopol was the best treatment, being significantly higher than the control group. The use of hydrogen peroxide is useless because its use prevents a hatching rate above 5%. From the first month, the use of glycerin was significantly better than other treatments and it ensures a hatching rate about 25% for at least 120 days. No significant differences were found with the use of water at different salinities.

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 los últimos años, el Instituto Español de Oceanografía (IEO) ha maximizado sus esfuerzos en desarrollar mecanismos para la cría en cautividad del atún rojo (Thunnus thynnus), cuyo ciclo completo está a punto de cerrarse. Este trabajo presenta los resultados obtenidos tras realizar mediciones acústicas con una ecosonda científica y un transductor split-beam en jaulas marinas donde los atunes, nacidos en cautividad, se separan en tres tamaños. La combinación de los datos acústicos y de los muestreos biométricos (obtenidos ópticamente) permite establecer una relación entre la longitud de los peces y el valor del target stregth (TS) devuelto por dichos peces. In recent years, the Spanish Institute of Oceanography (IEO) has maximized its efforts on developing mechanisms for the breeding of bluefin tuna (Thunnus thynnus), whose complete cycle is near to be closed. In this paper, acoustic measurements performed on young tuna cages (with scientific echosounder and split-beam transducer) are presented. Tuna housed in the cages were born in captivity and they are divided in three cages according to their size. The combination of the acoustic and biometric data (obtained with stereoscopic system) allow to establish a relationship between representative tuna length in each cage and the target strength (TS).

En prensa

Se ha estudiado la influencia de la alimentación con nauplios del copépodo Acartia tonsa (COP), con rotífero Brachionus plicatilis (ROT) enriquecido en ácidos grasos y una mezcla de ambos (MIX), sobre el crecimiento y la supervivencia de larvas de atún rojo, Thunnus thynnus. Los resultados muestran que la presencia de nauplios de Acartia en la dieta (COP y MIX) favorece tanto el crecimiento como la supervivencia de las larvas de atún rojo, en comparación con la dieta compuesta exclusivamente por rotífero enriquecido (ROT) The influence of the feeding with nauplii of the copepod Acartia tonsa (COP), the rotifer Brachionus plicatilis (ROT) enriched on fatty acids, and a mixture of both (MIX) on the growing and survival of the bluefin tuna larvae have been studied. The results show that the presence of the Acartia nauplii in the feeding (COP and MIX) improves significantly the growth and the survival in comparison with the feeding based exclusively on rotifers (ROT). Proyecto ATAME

Bluefin tuna (ABFT) fingerlings born in captivity were raised during 15 months in sea cages. ABFT were fed with raw fish, and they grew during this period from 4 gr to 8 kg. Mortality rate was great, mainly during the first three months. This is the first experience of ongrowing ABFT born in captivity. EU (SELFDOTT), Caladeros del Mediterráneo, S.A. Instituto Español de Oceanografía

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

The number of offshore wind farms is growing up quickly in the lasts years. Several studies about its environmental acoustic impacts have been developed at the same time the industry expands, most of them related to the high level impulsive noise produced during the pile diving process associated to the construction stage. Nevertheless, the study of the impact of the operational noise of turbines is very limited. In this paper we investigate the behavioural response of Bluefin tuna when exposed to the operation noise of a turbine. We analysed tuna reaction in terms of three parameters: depth of the school, swimming pattern and changes in the swimming direction. The experiment was developedin a fixed commercial tuna cage in the Mediterranean Sea. The usual behaviour of Bluefin tuna in captivity conditions was previously analysed using a continuous monitorization. Variations in depth were observed when feeding boat approaches, which could be interpreted as a consequence of the acoustical stimulus. The turbine noise was acoustically characterized, and reproduced using a broad-band underwater source. To monitor tuna behaviour two echosounders and a video system were simultaneously used. When exposed to short duration noise tuna behaviour does not exhibit clear disturbances. Nevertheless, with long duration emission tuna reacted: school reduced the radio of thecircular swimming region, moved up to the surface and some individuals were disorientated. Tuna seems to be habituated after several repetitions is short time. Proyecto AZIMUT. This work was financially support from Spanish Government by grant AP2009-4459. We thank both personal and material facilities provided by Grup Balfegó and Nuevo Tomás y Carmen crew.

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.

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)

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.