A Production Calendar Based on Water Temperature, Spat Size, and Husbandry Practices Reduce OsHV-1 μvar Impact on Cultured Pacific Oyster Crassostrea gigas in the Ebro Delta (Catalonia), Mediterranean Coast of Spain

Since 2006, the production of Pacific oyster Crassostrea gigas in the Ebro Delta area has dramatically declined from around 800 metric tons (MT) per year to 138 MT in 2011. This decline in production has had a significant socio-economic impact in a region where the shellfish sector is a traditional economic activity for many families. The identified agent responsible for this reduction in C. gigas production was Ostreid Herpesvirus microvar (OsHV-1 μvar), which has been associated with C. gigas spat mortalities in France, and in many other countries. In Spain the episodes of mortality became critical for the regional shellfish production between 2008 until 2014, with mortality percentage up to 100%. In this study, local hatchery C. gigas spat was used as sentinel animals for epidemiological studies and management tests carried out with the aim of reducing oyster mortality in the Ebro Delta area. A production calendar mainly based on water temperature dynamics was designed around an optimal schedule for spat immersion. The mmersion calendar included two optimal periods for spat immersion, in summer when temperatures are ≥25◦C and at the end of autumn and beginning of winter when they are ≤13◦C. Such production planning has reduced mortalities from 80% (in 2014 and previous years) to 2–7.5% in 2015 in cemented oysters. Furthermore, other recommendations related to spat immersion size, culture density and methodology, and cementing calendar, which helped to achieve the results presented, were also recorded and transferred to local producers. This work presents a successfully tested management strategy reducing OsHV-1 μvar impact by designing new field management practices mainly focused on the handling and timing of spat immersion. This approach could be used as a management model in areas presenting similar production practices and environmental characteristics.info:eu-repo/semantics/publishedVersio

Application of “taxocene surrogation” and “taxonomic sufficiency” concepts to fish farming environmental monitoring. Comparison of BOPA index versus polychaete assemblage structure

“Taxocene surrogation” and “taxonomic sufficiency” concepts were applied to the monitoring of soft bottoms macrobenthic assemblages influenced by fish farming following two approaches. Polychaete assemblage evaluation through multivariate analysis and the benthic index BOPA were compared. Six fish farms along the Spanish Mediterranean coast were monitored. Polychaete assemblage provided a suitable picture of the impact gradient, being correlated with total free sulphides. BOPA did not support the impact gradient described by the polychaete assemblage, providing erroneous categorizations. The inclusion of several polychaete families, which were locally identified as indicative of affection to recalculate BOPA, resulted in an improved diagnosis and correlation with the impact gradient. Nevertheless, frequent misclassifications occurred. These results suggest that the structure of polychaete families, sulphides and granulometry conform an appropriate strategy for fish farming monitoring. Biotic indices need to be specifically designed for concrete activities, and regionally validated, because of the environmental plasticity of benthic invertebrates.This research was funded by the Spanish National Plans of Aquaculture (JACUMAR)

Fisiología de la nutrición y del estrés en las primeras fases de vida del pulpo común (Octopus vulgaris). Resultados del proyecto OCTOPHYS

El cultivo del pulpo común (Oclopus vulgaris) está severamente limitado por las altas mortalidades que se producen durante su cultivo larvano, aunque en la actualidad, las causas especfficas de tan alta mortalidad siguen siendo desconocidas. Este proyecto pretende adquirir conocimientos básicos sobre la biología y fisiologia de las paralarvas a través de un enfoque multidisciplinarque incluye aspectos innovadores relacionados con la fisiologia de la nutrición y el estrés. Los objetivos propuestos están basados en un fuerte input zootécnico y prevén el uso de herramientas biométricas, bioquímicas, enzimáticas, moleculares y proteómicas, con el fin último de optimizar la condición y supervivencia de las paralarvas. Incluyen asimismo la búsqueda y selección de biomarcadores capaces de detectar y cuantíñcar el estrés nutricional.The culture oflhe common octopus (Octopus vulgaris) is hindered by high mortalities encountered during its paralarval rearing, allhough at present, Ihe specific causes forlhe high mortalities observed remain unidentified. This project aims at galhering a beller understanding of Ihe basic biology and physiology ofthe paralarvae, through a multidisciplinary and integrated approach, which includes Ihe study oflhe physiology 01 nutrition and!he evaluation 01Ihe stress condition. The objectives proposed are basad on a strong zootechnical input and foresee Ihe use of biometric, biochemical, enzymatic, molecular biology and proteomic tools, pointing towards the ultimate optimisation of Ihe paralarval condition and survival. They also include Ihe study ofthe nutritionally-derived stress and Ihe selection ofbiomarkers capable of its detection and quantification

Stoichiometry of growth under variable scenarios of nutrient limitation: Differential homeostasis of body composition among growth phenotypes of the Manila clam

Fast- and slow-growing phenotypes from two separate breeding families of the Manila clam (Ruditapes philippinarum) were alternatively fed two monoalgal diets with high and low N content (C:N ratios of 4.9 and 13.5, respectively). After 35 days of food conditioning, clams were sacrificed, and the soft body was dissected out into five different tissue fractions to determine the corresponding ponderal ratios (tissue wt./body wt.) and a separate analysis of the elemental composition of these tissues. Previously reported C and N balances performed with the same conditioning diets were integrated and compared with tissue composition of the same phenotypes in order to assess the efficacy of mechanisms elicited to compensate for N deficit. Broad differences in dietary N content resulted in only minor changes in whole-body C:N composition which suggests a noticeable degree of homeostatic regulation of nutrient balances. This regulation was found to be stricter in fast-compared to slow-growing phenotypes and differed among the various body tissues. Using the threshold element ratio approach, physiological mechanisms were identified that partly compensate for large stoichiometric mismatches between low-N food and body tissues.This work was supported by the Spanish Ministry of Economy and Competitiveness through project AGL2013-49144-C3-1-R. K. Arranz was funded by a predoctoral research grant from Universidad del País Vasco/Euskal Herriko Unibertsitatea (UPV/EHU). SGIker technical and human support (UPV/EHU, MICINN, GV/EJ, ESF) is gratefully acknowledged.info:eu-repo/semantics/publishedVersio

Exploring patterns of variation in amphipod assemblages at multiple spatial scales: natural variability versus coastal aquaculture effect

A 5-factor design survey was carried out to examine the spatial distribution at different scales of amphipod assemblages and sedimentary variables in soft bottoms adjacent to coastal aquaculture installations. Natural variability of sediment variables showed the highest values at the scales of sites (10s of meters) and locality (1 to 10 km), while the greatest component of variation of amphipod assemblages occurred among replicates (on the scale of meters). Regarding the influence of coastal aquaculture, the highest variability of the environmental variables was observed among the different fish farms. On sandy localities, the influence gradient of coastal aquaculture was determined by total free sulphides, whilst, in muddy localities, the main variable was δ15N. This study has important consequences for the establishment of a clear and effective methodology for studying and monitoring the impact of fish farming, highlighting the complicated establishment of a widespread pattern of effects by coastal aquaculture. The necessity to apply a high replication effort at several spatial scales, especially at the scales of meters and 10s of meters, to increase the precision of estimates of assemblage composition should be taken into consideration.This study forms part of the project ‘Selección de indicadores, determinación de valores de referencia, diseño de programas y protocolos de métodos y medidas para estudios ambientales en acuicultura marina’ funded by the ‘Spanish National Plans of Aquaculture’ (JACUMAR)

Molecular identification, life cycle characterization, and hatchery seed production of dwarf oysters from the Ebro Delta (Spain)

Dwarf oysters in the Ebro Delta are only observed growing on local pen shells, Pinna nobilis L., currently under extinction risk. The species identification of these populations is uncertain, given recent genetic classifications of dwarf oysters of Ostrea stentina species complex. Hence, the first objective of this study was to confirm the identity of dwarf oysters associated to P. nobilis in the Ebro Delta. Then, we aimed to assess the viability of hatchery and nursery production of O. stentina for potential conservation programs using diets based on a mix of live microalgae species or the commercial Shellfish Diet 1800®. Our results showed that COI sequences obtained were specific to O. stentina. Significant differences in the growth and survival of larvae between diet treatments were observed in 3 days. For the live diet, the larval period lasted from 15 to 22 days (299.2 ± 4 µm) whereas it took up to 36 days using the Shellfish Diet 1800® (280 ± 7.2 µm), with an overall mortality of 72.3 vs. 99.3%, respectively for each diet. Besides, no seed survival was observed for the commercial diet after a 10-day-fixation attempt. In contrast, ca. 16% of the individuals on the live diet that were allowed to settle reached the juvenile stage and could be released to the environment. Histological examination of obtained seed did not present any sign of disease and showed gonadal development for both sexes at ca. 6 months of age (16.1–19.1 mm). The growth curve obtained was fitted to a Schnute-Richards growth model which returned ages of up to 10 years for maximum local sizes of 45 mm. We conclude that although the Shellfish Diet 1800® is not an adequate diet for O. stentina, its hatchery production is feasible and might provide support to future conservation actions.info:eu-repo/semantics/publishedVersio

Reproduction of the endangered fan mussel Pinna nobilis under natural and captivity conditions

1. A mass mortality event that started in 2016 has put the fan mussel Pinna nobilis close to the brink of extinction, leading to the species being classified as Critically Endangered in the Red List of the International Union for Conservation of Nature. Under current circumstances, with the persistence of the disease caused by Haplosporidium pinnae in the open sea, isolated populations in coastal lagoons and estuarine bays appear to be the main chance for the survival of the species. 2. The low resilience of those populations highlights the importance of implementing additional measures to avoid the extinction of the fan mussel. One of these measures relies on completing its reproductive cycle in captivity. The reproductive window of the remaining fan mussel population in Alfacs Bay was explored to obtain gametes and to understand possible limitations in the reproductive activity in wild populations. For this purpose, during the reproductive season, several groups of individuals were relocated for short periods (~2 weeks) into the vivarium to obtain gametes under controlled conditions. Simultaneously, controlled temperature treatments and adapted food dosage for conditioning adult fan mussels out of their reproductive season in the wild were conducted in a recirculating aquaculture system. 3. The reproduction of natural populations was mostly restricted to May, featuring temperatures around 20°C. A low success of spawning was obtained in the vivarium, with a 0% success in 11 out of 20 of the trials (six to nine individuals each) and an overall success of 16% (25 out of 156 individuals). A 100% success (14 out of 14) was obtained with individuals conditioned for ~2 months in the recirculating aquaculture system. A second conditioning of six of those individuals was attempted after a ~3-month period, with a 33.3% success of spawning.We would like to thank the local government ‘Generalitat de Catalunya’ for all the permissions for the manipulation of individuals granted through the ‘Servei de Fauna i Flora’ and the Natural Park of the Ebro Delta. We would also like to thank the support of the Ministry for the Ecological Transition and the Demographic Challenge, through ‘Fundación Biodiversidad’ for supporting the work with PinnaSpat project, 2019 call for proposals. Some additional field campaigns in the Ebro Delta were also supported by the RecuperaPinna project, also funded through the ‘Fundación Biodiversidad’ in the 2020 call for proposals and EsMarEs (Ministerio para la Transición Ecológica, Spanish Government).info:eu-repo/semantics/acceptedVersio

A meta-analysis approach to the effects of fish farming on soft bottom polychaeta assemblages in temperate regions

Marine fish farms could cause environmental disturbances on the sediment due to uneaten food and fish faeces that impact the marine benthos. Polychaete assemblages are considered good indicators of environmental perturbations. The present study aimed to establish groups of polychaetes as potential indicators of fish farm pollution. This study was carried out in ten fish farms along the Spanish coast. Changes in polychaete assemblage were analyzed with meta-analysis and multivariate techniques. Abundance, richness and diversity showed significant decreases under fish farm conditions. Distribution patterns of polychaetes responded to combinations of physicochemical variables. The main ones are sulfide concentration, silt and clays percentage, and stable nitrogen isotope ratio. The results showed that some families are tolerant, Capitellidae, Dorvilleidae, Glyceridae, Nereididae, Oweniidae and Spionidae; while others are sensitive to fish farm pollution, Magelonidae, Maldanidae, Nephtyidae, Onuphidae, Paralacydoniidae, Paraonide, Sabellidae and also Cirratulidae in spite of being reported as a tolerant family.This study is part of the project “Selección de indicadores, determinación de valores de referencia, diseño de programas y protocolos de métodos y medidas para estudios ambientales en acuicultura marina” and was funded by the “Spanish National Plans of Aquaculture” (JACUMAR)