Cristóbal Aguilera

The aim of this work was to run an economic assessment of investment in automatic feeding systems for grow‐out farms of different sizes producing European sea bass in the Mediterranean Sea. For this, we have used an economic model to simulate the annual income statement of a typical farm with different production volumes: a small‐sized farm with a production of 413 tons/year, a medium‐sized farm of 1122 tons/year, and a large‐sized farm of 2539 tons/year. With the values obtained in the simulation, we have carried out partial budget and investment analyses to estimate the economic value of this investment decision. To complement our economic assessment, a sensitivity analysis has also been run to include risk in the investment decision. Our findings show that the implementation of automatic feeding systems in sea bass grow‐out farms would be a good economic decision, regardless of the farm size, since there are technological options suitable for different farm sizes and capital investment capacities. Consequently, innovation and investment in feeding management should not be impeded or limited by the farm size.

The aim of this work is to evaluate how changes in a set of different key operational factors (e.g., the unit sales price, the fingerling unit cost, the feed unit cost, and so on) would impact on the economic performance of a typical grow-out farm producing European sea bass in the Mediterranean under different scenarios of production related to the farm size (production volume) and production strategy (size of the produced fish). A what-if analysis using a deterministic static model to simulate the annual income statement of a typical grow-out farm was carried out. Data was obtained from ten European facilities located in the Mediterranean Sea. Our findings show the importance of the farm’s scale and the production of larger fish to obtain better economic results. Another important conclusion is that increase in fish growth and survival rates, innovating in feed and improving the breeding and health conditions, could compensate the reductions in the sea bass sales prices more efficiently than using other alternatives.

Since 2006, the production of Pacific oyster Crassostrea gigas in the Ebro Delta area has dramatically declined from around 800 metric tonnes (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 immersion 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.

The objective of the study was to acclimatise wild-caught meagre (Argyrosomus regius) to captivity to produce viable eggs for aquaculture production. Twelve meagre (3 males and 9 females, mean weight = 20 ± 7 kg) were caught and transported to a land-based facility on 26 October 2006. During, March to June 2007, all three males were spermiating and five of the nine females were in vitellogenesis with mean maximum oocyte diameter ≥550 μm. No spontaneous spawning was observed. Two hormone treatments, either a single injection of gonadotropin-releasing hormone agonist (GnRHa, 20 μg kg⁻¹ for females and 10 μg kg⁻¹ for males) or a slow-release implant loaded with the same GnRHa (50 μg kg⁻¹ for females and 25 μg kg⁻¹ for males), were used to induce spawning on three different dates on 26 March 2007, 4 May 2007 and 18 April 2008. From each spawning event, the following parameters were determined: fecundity, number of floating eggs, egg size, fertilisation and hatching success, unfed larval survival, and proximal composition and fatty acid profile of the eggs. In 2007, two females that were injected on 26 March and 4 May spawned a total of 5 times producing 9,019,300 floating eggs and a relative fecundity of 198,200 eggs kg⁻¹ and two different females that were implanted on the same dates spawned 14 times producing 12,430,000 floating eggs and a relative fecundity of 276,200 eggs kg⁻¹. In 2008, a pair that was implanted spawned five times producing a total of 10,211,900 floating eggs and a relative fecundity of 527,380 eggs kg⁻¹. The latency period was 48–72 h. Parameters were compared between hormone treatments, date of hormone induction and parents determined by microsatellites. Percentage hatch and egg size were 70 ± 0.3% and 0.99 ± 0.02 mm, respectively, for GnRHa-implanted fish and were significantly higher (P < 0.05) compared to 30 ± 0.3% and 0.95 ± 0.03 mm, respectively, for injected fish. Few differences were observed in proximal composition and fatty acid profile and for all spawns mean (% dry weight) lipid content was 17.3 ± 3.0%, carbohydrate was 4.4 ± 1.9% and protein was 31.5 ± 6.4% and the essential fatty acids: Arachidonic acid (ARA, 20:4n-6) ranged between 0.9 and 1% (of total fatty acids), eicosapentaenoic acid (EPA 20:5n-3) 7.7–10.4% and docosahexaenoic acid (DHA 22:6n-3), 28.6–35.4%. All good quality spawns were obtained in the second and/or third spawn after GnRHa treatment, whereas all bad quality spawns were obtained either on the first spawn or after the fifth spawn. Both spawning protocols gave commercially viable (1,000,000+) numbers of good quality eggs that could form the basis of a hatchery production.

To assess the possibility of O. vulgaris ongrowing using tanks or cages in the bays of the Ebro Delta, we performed several growth trials of common octopus held in tanks. Effects of environmental factors (temperature and salinity) and zootechnical aspects (culture density) were studied. The thermal ranges that defined positive growth periods in the bays of the Ebro Delta were 19.5ºC to 23ºC (spring-summer) and 23.5ºC to 12.3ºC (autumn-winter), the latter being the most suitable period for ongrowing. Salinity did not affect survival (100%) or growth within the range tested (34-29 psu), though feeding rates (AFR, SFR) were directly related to salinity. On the other hand, after 60 days, final culture density increased three-fold (D1: 12.36 → 44.37 kg m–3; D2: 24.13 → 67.76 kg m–3), with optimal survival results ( > 90%) for the two densities tested. Growth and feeding rates showed a slight inverse relationship with density. Finally, growth and feeding rates showed a clear dependence on temperature in the two experiments (density and salinity). Our results conclude that industrial production of O. vulgaris in tanks is promising: this system offers an alternative to cages and allows for a more exhaustive control of culture.

A long-term epidemiological study ofCryptosporidium molnariin aquacultured European sea bass (ESB) and gilthead sea bream (GSB) was performed in different types of facilities on the Atlantic, Cantabric, and Mediterranean coasts. Four types of studies were carried out. In study A, fish raised from juveniles to marketable size (ongrowing stage) were periodically sampled in three different types of cultures. Studies B and C focused on hatchery and nursery facilities. In study D, occasional samplings were performed during mortality or morbidity outbreaks. As a general trend,C. molnariwas more prevalent in GSB than in ESB. Data on the distribution pattern ofC. molnariin total sampled GSB (studies A, B, and D) had a variance higher than the mean (overdispersion). In GSB (study A), the type of ongrowing system (sea cages, earth ponds, or indoor tanks) was found to have no significant effect. There was a significant relationship between the presence of the parasite and both fish weight and season. The highest infection values were recorded in spring. Prevalence and intensity had convex weight profiles, with a peak in 30- to 100-g fish. In study D, the prevalence of infection was higher in fish recently introduced in sea cages and in preongrowing systems. In studies B and C, fish were almost never infected before entering the postlarval and nursery facilities. The parasite seems to enter the host mainly through the water in production steps with less stringent water treatment. Recirculation systems and fish cannibalism could contribute to oocyst concentration and dispersion in aquaculture facilities.