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Wreckfish (Polyprion americanus) is a promising new species for aquaculture diversification due to its fast growth, late reproductive maturation, and high market price. Nowadays, low larval survival is considered the biggest limitation in wreckfish farming. Here, the fertilization, hatching, and survival rates of 20 spawning events from an established wreckfish broodstock have been analyzed in order to characterize the main bottlenecks in wreckfish early and larval development. The ontogenesis of the skeletal system and the incidence of skeletal deformities have been assessed in 632 samples from larval rearing trials using an acid free double staining protocol. Furthermore, the effect of different rearing temperatures (13 vs 16 ºC) and light intensities at water surface (600, 900 and 1200 lux) on the skeletal development have been also explored. Results showed as while a variable egg fertilization rate (61.75 ± 34.62%) were achieved, a very poor hatching (4.52 ± 9.27%) and survival rate (0.01 ± 0.00%) until 71 days post hatching (dph) were observed. Swimbladder inflation was first seen at 7 dph, and at 11 and 25 dph a 61-63% of fish functional swimbladder. The first skeletal structures to be formed were those related with breathing and feeding activities (e.g., cleithrum, Meckel¿s cartilage and ceratobranchials) and were visible in larvae of 4-5 mm of standard length (SL). Ossification of the vertebral column progressed in an anterior-to-posterior direction, being fully ossified at 7-14 mm of SL. Regarding the skeletal deformities, a high incidence (63%) of jaw deformity (particularly lower jaw deformity) was observed in larvae of 4-5 of SL, progressively decreasing (up to 5%) in larvae of >6 mm of SL. Deformed vertebrae (compressed, fused, and/or displaced) were mainly located at the 13 to 15th vertebra, and were associated to lordosis, most probably due to the no swimbladder inflation. No clear relationship between temperature and the incidence of lower jaw deform

Background: Understanding sex determination (SD) across taxa is a major challenge for evolutionary biology. The new genomic tools are paving the way to identify genomic features underlying SD in fish, a group frequently showing limited sex chromosome differentiation and high SD evolutionary turnover. Turbot (Scophthalmus maximus) is a commercially important flatfish with an undifferentiated ZW/ZZ SD system and remarkable sexual dimorphism. Here we describe a new long-read turbot genome assembly used to disentangle the genetic architecture of turbot SD by combining genomics and classical genetics approaches. Results: The new turbot genome assembly consists of 145 contigs (N50 = 22.9 Mb), 27 of them representing >95% of its estimated genome size. A genome wide association study (GWAS) identified a ~ 6.8 Mb region on chromosome 12 associated with sex in 69.4% of the 36 families analyzed. The highest associated markers flanked sox2, the only gene in the region showing differential expression between sexes before gonad differentiation. A single SNP showed consistent differences between Z and W chromosomes. The analysis of a broad sample of families suggested the presence of additional genetic and/or environmental factors on turbot SD. Conclusions: The new chromosome-level turbot genome assembly, one of the most contiguous fish assemblies to date, facilitated the identification of sox2 as a consistent candidate gene putatively driving SD in this species. This chromosome SD system barely showed any signs of differentiation, and other factors beyond the main QTL seem to control SD in a certain proportion of families

Wreckfish (Polyprion americanus) is considered to be a good candidate for European aquaculture. The main biometric parameters were recorded from 86 wild-caught fish (2.6-18 kg of total weight) for 14 months and the gonadosomatic index (GSI), hepatosomatic index (HIS) and viscerosomatic index (VSI) were obtained. Biochemical analyses of muscle, liver and gonads from wild wreckfish showed that wreckfish has a high level of protein in muscle, 84% of dry weight (DW), and low level of lipids (7% DW). Capture season, sex, size or weight of the fish did not have a strong effect on the variability observed in the levels of proteins, lipids and fatty acids of the different tissues. Reared wreckfish have more lipids in mature gonads than wild fish, which may be due to a more lipid-rich diet. However, some polyunsaturated fatty acids (PUFA) such as arachidonic acid (ARA) and docosahexaenoic acid (DHA) reached higher values in wild female gonads than in reared gonads, which could indicate the wreckfish has high requirements in these fatty acids. This study obtained valuable data on the biology and biochemical composition of wreckfish to estimate its nutritional requirements, which could be useful for the future of this species in aquaculture.

The impact of changes in dietary lipids and protein sources on texture was evaluated on farmed blackspot seabream (Pagellus bogaraveo) throughout 14 days of ice storage and compared with wild fish. A commercial diet formulated with a high proportion of lipids, and two diets formulated with an important reduction of lipid levels by 60% and adding either plant protein sources (LL diet) or fishmeal (LL + diet) were supplied during growth until commercial size was attained. In the wild fish, the raw fillet hardness was significantly higher than in farmed fish during the entire ice-storage period. In the farmed fish, an increase of muscle lipid accumulation and change of fiber density were responsible for the variations in texture in the raw fillet. The highest reduction was found in fish fed with diets LL+ and LL. The texture parameters studied on the cooked fillets showed no significant differences, neither attributable to the diets nor to the ice-storage period.

Background: Understanding sex determination (SD) across taxa is a major challenge for evolutionary biology. The new genomic tools are paving the way to identify genomic features underlying SD in fish, a group frequently showing limited sex chromosome differentiation and high SD evolutionary turnover. Turbot (Scophthalmus maximus) is a commercially important flatfish with an undifferentiated ZW/ZZ SD system and remarkable sexual dimorphism. Here we describe a new long-read turbot genome assembly used to disentangle the genetic architecture of turbot SD by combining genomics and classical genetics approaches. Results: The new turbot genome assembly consists of 145 contigs (N50 = 22.9 Mb), 27 of them representing >95% of its estimated genome size. A genome wide association study (GWAS) identified a ~ 6.8 Mb region on chromosome 12 associated with sex in 69.4% of the 36 families analyzed. The highest associated markers flanked sox2, the only gene in the region showing differential expression between sexes before gonad differentiation. A single SNP showed consistent differences between Z and W chromosomes. The analysis of a broad sample of families suggested the presence of additional genetic and/or environmental factors on turbot SD. Conclusions: The new chromosome-level turbot genome assembly, one of the most contiguous fish assemblies to date, facilitated the identification of sox2 as a consistent candidate gene putatively driving SD in this species. This chromosome SD system barely showed any signs of differentiation, and other factors beyond the main QTL seem to control SD in a certain proportion of families

Four different wreckfish (Polyprion americanus) broodstock batches were maintained in research facilities under different photo and thermo-period conditions, one in Greece, the Helenic Center for Marine Research (HCMR, n = 3) and three in Spain: Instituto Español de Oceanografía (IEO, n = 13) in Vigo, Aquarium Finisterrae (MC2, n = 21) in A Coruña and Consellería do Mar (CMRM, n = 11). The CMRM includes two centers that work together: Instituto Galego de Formación en Acuicultura (IGAFA) and Centro de Investigacións Mariñas (CIMA), both in Pontevedra. During the five years of the project DIVERSIFY (Exploring the biological and socio-economic potential of new-emerging candidate fish species for the expansion of the European aquaculture industry, 2013–2018) works focused on the reproductive biology of the species, broodstock, and larvae nutrition and development of incubation and larval rearing protocols have been carried out. In terms of reproduction, catch methods of new wild animals, the reproductive cycle, sperm characteristics evaluation, and spontaneous and induced spawning methods have been described for wreckfish. Regarding nutrition, the positive effect of two types of enrichment on the fatty acid profiles of Artemia and rotifer has been verified. The relationship between the fatty acid profile of the diets supplied to the broodstock and the fatty acid profile obtained in the oocytes and eggs of the females fed with different diets, has also been demonstrated. Finally, early larval ontogeny has been described and incubation and larval rearing protocols have been proposed based on the results obtained in the different experiments of temperature, growth, survival, and larval feeding that were carried out

Following the series of articles published on the fish species included in the EU-funded DIVERSIFY project (see April, May, June, July and October issues of International Aquafeed), which ran between 2013 and 2018, we present here the wreckfish (Polyprion americanus), which was the most challenging species in the project. The wreckfish is one of the largest Polyprionidae species, reaching a size of 100kg. It is a deep-water fish (100-to-1000m) found almost throughout the world and is characterised by an extended pelagic juvenile phase (Ball et al., 2000; Sedberry et al., 1999). It is one of the most interesting new species for aquaculture, due to its fast growth (Suquet & La Pomélie, 2002; Rodriguez-Villanueva et al., 2011), late reproductive maturation, high market price and limited fisheries landings and easy handling in captivity with no mortality recorded during the DIVERSIFY trials (Papandroulakis et al., 2008). Its large size makes it appropriate for processing and development of value-added products, which could be of interest for the EU market.

Four different wreckfish (Polyprion americanus) broodstock batches were maintained in research facilities under different photo and thermo-period conditions, one in Greece, the Helenic Center for Marine Research (HCMR, n = 3) and three in Spain: Instituto Español de Oceanografía (IEO, n = 13) in Vigo, Aquarium Finisterrae (MC2, n = 21) in A Coruña and Consellería do Mar (CMRM, n = 11). The CMRM includes two centers that work together: Instituto Galego de Formación en Acuicultura (IGAFA) and Centro de Investigacións Mariñas (CIMA), both in Pontevedra. During the five years of the project DIVERSIFY (Exploring the biological and socio-economic potential of new-emerging candidate fish species for the expansion of the European aquaculture industry, 2013–2018) works focused on the reproductive biology of the species, broodstock, and larvae nutrition and development of incubation and larval rearing protocols have been carried out. In terms of reproduction, catch methods of new wild animals, the reproductive cycle, sperm characteristics evaluation, and spontaneous and induced spawning methods have been described for wreckfish. Regarding nutrition, the positive effect of two types of enrichment on the fatty acid profiles of Artemia and rotifer has been verified. The relationship between the fatty acid profile of the diets supplied to the broodstock and the fatty acid profile obtained in the oocytes and eggs of the females fed with different diets, has also been demonstrated. Finally, early larval ontogeny has been described and incubation and larval rearing protocols have been proposed based on the results obtained in the different experiments of temperature, growth, survival, and larval feeding that were carried out.

A major challenge in evolutionary biology is to find an explanation for the variation in sex-determining (SD) systems across taxa and to understand the mechanisms driving sex chromosome differentiation. We studied the turbot, holding a ZW/ZZ SD system and no sex chromosome heteromorphism, by combining classical genetics and genomics approaches to disentangle the genetic architecture of this trait. RAD-Seq was used to genotype 18,214 SNPs on 1,135 fish from 36 families and a genome wide association study (GWAS) identified a ~ 6 Mb region on LG5 associated with sex (P < 0.05). The most significant associated markers were located close to sox2, dnajc19 and fxr1 genes. A segregation analysis enabled narrowing down the associated region and evidenced recombination suppression in a region overlapping the candidate genes. A Nanopore/Illumina assembly of the SD region using ZZ and WW individuals identified a single SNP fully associated with Z and W chromosomes. RNA-seq from 5-90 day-old fish detected the expression along the gonad differentiation period of a short non-coding splicing variant (ncRNA) included in a vertebrate-conserved long non-coding RNA overlapping sox2. qPCR showed that sox2 was the only differentially expressed gene between males and females at 50-55 days post fertilization, just prior the beginning of gonad differentiation. More refined information on the involvement of secondary genetic and environmental factors and their interactions on SD was gathered after the analysis of a broad sample of families. Our results confirm the complex nature of SD in turbot and support sox2 as its main driver.

The first wreckfish (Polyprion americanus) juveniles have been produced in Galicia, Spain, after years of research in the reproduction and larval rearing of the species in the framework of the DIVERSIFY project (www.diversifyfish.eu). Early this year, researchers in Vigo, Illa de Arousa, Vilanova de Arousa and A Coruña have finally seen their efforts coming to fruition with the consistent acquisition of large quantities of fertilized eggs after spontaneous tank spawning of their captive reared broodstocks. Given the continuous supply of eggs, the planned research efforts for the development of larval rearing methods have been implemented and the result is a small number of hatchery-produced juvenile wreckfish happily swimming in the tanks of IGAFA and IEO....

One of the priority target within the European project DIVERSIFY is to set the optimal conditions for larval rearing of wreckfish (Polyprion americanus), as well as the development of a general culture protocol that ensures high larval survival. For this reason, the Hellenic Center for Marine Research (HCMR, Greece), Aquarium Finisterrae (MC2, Galicia, NW Spain), Instituto Galego de Formación en Acuicultura (HCMR, NW Spain) and Instituto Español de Oceanografía (IEO, NW Spain) are working with their respective broodstocks, to achieve viable sets and perform experiments commissioned in the project. In this work the first experiments that allowed wreckfish larvae to survive until day 24 of life and to collect growth data, as well as valuable information on larval ontogeny, are described.

Nutritional requirements of wreckfish are unknow so far and there are only a few references related to feeding habitats from commercial caught (Brick Peres & Haimovi, 2003) and feeding rates in captivity (Papandroulakis et al., 2004) . Recently some studies were done about composition of wild wreckfish (Roncarati et al.,2014, Linares et al., 2015). The optimum development of broodstock diets for wreckfish will be essential for the future of the aquaculture of this species. Dietary lipids and specially fatty acids play a critical role in the successful production of high quality gametes and eggs of marine fish (Izquierdo et al., 2001; Sargent et al., 2002). The aim of this work is collecting information about the influence of the feeding of wreckfish broodstock on oocytes composition with the aim of knowing the relationship of broodstock feeding on fecundity and spawn quality.

Within the DIVERSIFY project for the diversification of species in European aquaculture, wreckfish is a special case because of its late sexual maturation, which does not occur until 7-8 years of age (Peleteiro and Brunzón, 2014), besides existing very few data on its reproductive biology because it is a demersal species whose adult specimens tend to live at the range of 100-1000 meters of deep. This work sets out the progress made in the study of the reproductive cycle of this species in stocks established in Galicia (Spain).

Se estudió mensualmente la evolución de la maduración sexual en 3 stocks de cherna (Polyprion americanus) ubicados en Galicia durante los meses de Marzo-Junio. Se obtuvieron muestras de ovocitos mediante canulación, y de esperma por presión abdominal. El análisis del diámetro de los ovocitos muestra que la maduración alcanza su máximo nivel entre finales de abril y mediados de mayo, cuando comienza una leve regresión. En el caso de los machos, la concentración y la movilidad de los espermatozoides del esperma sigue el mismo patrón, sincronizándose con el estado de maduración de las hembras. Estos datos se ajustan a los registros obtenidos en pesquerías naturales para esta especie (Brick y Klippel, 2003)., Se estudió mensualmente la evolución de la maduración sexual en 3 stocks de cherna (Polyprion americanus) ubicados en Galicia durante los meses de Marzo-Junio. Se obtuvieron muestras de ovocitos mediante canulación, y de esperma por presión abdominal. El análisis del diámetro de los ovocitos muestra que la maduración alcanza su máximo nivel entre finales de abril y mediados de mayo, cuando comienza una leve regresión. En el caso de los machos, la concentración y la movilidad de los espermatozoides del esperma sigue el mismo patrón, sincronizándose con el estado de maduración de las hembras. Estos datos se ajustan a los registros obtenidos en pesquerías naturales para esta especie (Brick y Klippel, 2003).

The wreckfish (Polyprion americanus) is a much appreciated species from the gastronomic point of view. The renowned quality this fish is well known, both nationally as in the international market. This makes wreckfish a good candidate for marine aquaculture diversification. Preliminary results on the biology (Wakefield et al., 2013) and culture (Peleteiro et al., 2014) of this species suggest that this is a fast grower. Wreckfish also acclimates easily to captivity and handling, and despite their large sizes, no mortality related to handling has been observed. This species readily accepts prepared diets in captivity, and is characterized by its low metabolism and inhabiting great water depths. The present research was designed to obtain information on biochemical composition, biometric parameters, sexual differentiation and maturity of wild caught wreckfish, which are important for a success culture of this species.

In order to determine the differences between wild and farmed blackspot seabream, a promising finfish species for aquaculture, some parameters affecting quality were evaluated, such as proximal and fatty acid profiles, texture, skin and muscle colours and muscle cellularity, along with an extensive sensory assessment. Proximal composition showed a higher fat proportion in the farmed group whilst higher collagen content was found in the wild group. The fatty acid profile of the farmed group showed important values of EPA and total n − 3 HUFA. Sensory evaluation registered changes in all tested features, especially seafood attributes linked to wild fish and fish oil attributes associated with the farmed group. Texture studies were focused on whole fish and on fillets, both raw and cooked. Raw wild fish fillet showed higher values for hardness and fracturability than farmed fillet. Cooked farm fish fillet rendered higher springiness values than those observed in the wild group. Significant variations were determined in colour studies with a higher lightness (L*) and redness (a*) on the skin of the wild fish and a higher hue than farmed fish. The analysis of fibre type showed that red muscle area was extensive in farmed fish in the cranial, medial and caudal areas. Additionally, the fibre morphology of the red muscle of wild fish showed a greater amount of smaller fibres than that observed in farmed specimens in the three studied areas. The fibres with smaller girth on white muscle were only found in the cranial section of the wild fish.

One of the selected species for the diversification of traditional marine species is the wreckfish Polyprion americanus due to its growth potential, high larval growth index during its pelagic life phase (Kentouri et al 1995, Papandroulakis et al 1997), the quality of its flesh and its high commercial value. Studies on wreckfish nutritional requirements and optimum diets are missing. There are only a few references related to feeding habitats from commercial caught (Brick Peres & Haimovi, 2003) and feeding rates in captivity (Papandroulakis et al., 2004) . Recently a study about composition of Mediterranean Sea wreckfish was published (Roncarati et al.,2014). The aim of this work is collecting information of the composition of different tissues of wild wreckfish to contribute the development of a specific formulation of a diet for wreckfish broodstock.

Senegalese sole (Solea senegalensis) is a species of great interest in aquaculture because it has a high commercial value and a fast development of eggs. The reproduction of Senegalese sole in captivity has been studied since the early 1980s (Rodriguez et al., 1982). While F1 females were shown to be able to produce fertilized eggs from natural spawning as long as they were accompanied by wild males (Mañanos, 2011), failure of F1 males to display normal courtship behaviour has been demonstrated (Carazo et al., 2009). The reason for this failure remains unclear and therefore, research in this subject is paramount to overcome this bottleneck in S. senegalensis culture. We have designed an experiment using two broodstocks maintained since 2010 in the aquaculture facilities of the Oceanographic center of Vigo, one of them (T1) constituted by wild females together with wild and F1 males and the other (T2) constituted by F1 females together with wild and F1 males. One year later we obtained a successful spawn in T2. The main goal of this research was to test whether the male responsible for this spawn was F1.

Durante los últimos años el sistema de cultivo de microalgas marinas ha evolucionado desde los cultivos extensivos y la producción en bolsas de grandes volúmenes para alcanzar la biomasa adecuada, pasando por sistemas de cultivo intensivo en continuo y llegando en la actualidad al uso de un sistema semicontinuo, a base de fotobiorreactores que aprovechando al máximo la luz, consigue alcanzar producciones óptimas en volúmenes y tiempos mucho más reducidos, economizando espacio, tiempo, material e incluso personal. Este experimento consistió en la validación para microalgas de un sistema de valoración y recuento automático de uso veterinario para análisisde esperma (SeA). Los resultados indican que este sistema no sólo es operativo, sino que puede ser de gran utilidad configurando la aplicacitli precisa para el análisis de los parámetros de calidad en el cultivo intensivo de frtoplancton., The marine microalgae conure system has evolved since Ihe beginning 01 aquaculture, where large volumes were produced to attain an adequale biomass, extensive culture, intensive continuous cultures and finally Ihe semi continuous systems Ihat are presently used, using photo bioreactOll, which optimize Ihe use 01 light and nutrients to attain optimal microalgae production in much lower volumes and shorter times, reducing space aIII time required, as well as costs relatedto material and hand labor. The objective 01 this experiment was to validate an automatic sperm count normally used in the veterinary industry (SeA), for rts use in microalgae count. Results indicate that the SeA is valid forthis use. Furthermore, SCAcan be of great utility and accuracy, when configured forthe analysis~ quality parameters in the intensive microalgae culture.

En las instalaciones de la planta de cultivos marinos del Centro Oceanoqráñco de Vigo (lEO) se cuHivan diversas especies de microaJgas seg1ÍI! sistema tradicional de producción en bolsas (5OOL) y, mayoritariamente; bajo un nuevo sistema de producción en lotobiorreac!ores (FBRs)de columna (1 ooUUd.) de ano rendimiento montados por la empresa AQUALGAE SL. Parte de la producción de microalgas se destina al OJltivoy enriquecimiento de alimento vivo (rotíferos y Artemia). Este experimento se diseñó con el fin de obtener resutados que nos permitan asegurara calidad del cultivo de rotífero, aportando como alimento las microalgas producidas en semicontinuoen los FBRs, para poder así sustituirtotalmenle el sistema tradicional de producción en bolsas, menos productivo, más laborioso y sin apenas control sobre la composición nutricional dela biomasa cosechada. Los resultados obtenidos demuestran la calidad y estabilidad nutricional de las microalgas producidas en los FBRs,11) habiendo dilerencias signilicativas en el crecimiento de las poblaciones de rotíferos, aunque el número total de huevos sí ha sido superior en ~ grupo alimentado con microalgas procedentes de los FBRs. Se discuten además las dilerencias se composición nutricional observadas., In lhe lacilijies 01 lhe Centro Oceanográfico de Vigo (lEO) several species 01 microalgae are produced according to the traditional batch OJltureil poIyelhylene bags (500 L) ando more recently, in high yield column photobiorreactors (PBRs), 100 L each column, installed by tIle ~ AQUALGAE SL. Part 01 lhe harvested microalgae biomass is used lor lhe culture and enrichment 01 live prey (rotiler and Artemia). The goal cíl!e lhis wor1