Globally, aquaculture contributes to sustainable food and nutritional stability. However, stress conditions constitute a major threat affecting farmed-fish welfare and fish farms’ performances. In this regard, the present study was aimed at measuring and comparing in-situ (offshore) the physiological stress responses caused by recurrent sampling operations for length–weight measurement. Studied fish were European sea bass Dicentrarchus labrax sub-adults and adults reared in intensive farming conditions in M’diq Bay, on the Moroccan Mediterranean coast. The physiological stress response was evaluated by measuring blood biomarkers, including cortisol, glucose, lactate, total cholesterol and total proteins levels, and hematocrit percentage. The hypercortisolemia, hyperglycemia, hyperlactatemia and hypoproteinemia detected in the post-sampling state in both age groups of D. labrax indicated stress tendencies and a high sensitivity to aquaculture practice-related stress factors, with major and minor responses detected in the same age and same stress conditions. It is also interesting to note that the fish age and the time-course of the sampling operation had a statistically significant effect in terms of the physiological response (with p < 0.01 and p < 0.001, respectively). In conclusion, the present study showed that sea bass subjected to various stressful situations in intensive farming conditions displayed a physiological stress response specific to its age, to the individual status, as well as to the duration of stressor.

The present study aimed to quantify and compare in situ the primary and secondary physiological stress responses, related to the changing operations of floating net cages, in both subadult (523 days post hatching [dph]) and adult (916 dph) European sea bass Dicentrarchus labrax under intensive farming conditions in the Moroccan M'diq Bay. The blood levels of cortisol, glucose, total cholesterol, total protein, and lactate, as well as the percentage of haematocrit, were measured before and after this operation. The results showed significantly elevated levels of cortisol and blood glucose in both age groups, whereas total cholesterol and protein levels were unaffected. In fact, blood lactate significantly decreased in subadults, whereas in adults this parameter was not affected by the operation. However, the haematocrit percentages measured after the operation were significantly higher than those found before the operation in both groups of fish, which is attributed to the increased rate of oxygen renewal in the new net cages and the lower water temperature inside the cages. With regard to the age-specific response during this essential operation plasma cortisol, blood glucose, and lactate concentrations, as well as plasma total protein levels, were significantly higher in subadults than in adults, in both pre- and post- stress measurement, with the presence of individual-specific response. It is concluded that aquaculture practices such as changing the aquaculture net cage could have repercussions in terms of the classic physiological responses to stress in D. labrax.

Aquaculture is considered one of the fastest-growing food production systems in the world; however, its development is still facing constraints in Morocco, particularly in its marine branch. There is, among others, a great need for integrated site selection to ensure the sustainable development of aquaculture. In an attempt to contribute to the sustainable concept of suitable fish farm sites selection in Morocco, the present work focused on a marine zone, known as M’diq Bay. Based on FAO and GFCM recommendations for the implementation of allocated zones for aquaculture (AZA) and carrying capacity (CC) concepts, site selection was performed in this bay using GIS-spatial multi-criteria evaluation (SMCE) method, aligned with the analytic hierarchy process (AHP) and weighted linear combination (WLC). This procedure allowed us to identify and select suitable areas for fish farming in M’diq bay. In addition, the carrying capacity approach was implemented on physical, productive, ecological, and socio-economic dimensions to define their sustainable levels and harmonious combination. The results showed that seven fish farms are possible to integrate and operate without generating negative effects on the bay ecosystem. The allowed zone for aquaculture was around 84 ha, representing only 0.6% of the bay's total area, with a maximum production level of 2,900 tonnes.

The objective of this study was to assess the biologic impact of four diets based on three species of microalgae on the Mediterranean mussels Mytilus galloprovincialis. For this purpose, flesh weight, linear growth, survival rate and the biochemical composition of mussel flesh have been evaluated. Mussels fed with a mixture of the three species; Nannochloropsis sp., Dunaliella sp., and Phaeodactylum sp., exhibited the highest lipid level (7.66%). This suggests that mixing several species in the same diet favors lipid production. Protein level was significantly higher in mussels fed with Dunaliella sp. (28.92%) compared to Phaeodactylum sp. (24.52%), Nannochloropsis sp. (22.94%) and a combination of the three species (26.07%). Wet weight gain was significantly higher in mussels fed with Dunaliella sp. (7.76 g) compared to mussels fed with the mixture of the three species (6.87 g). However, mussel shell length was not different among the four groups, and ranged between 41.7 mm and 42.3 mm. In conclusion, the data from this study suggest that a diet based on Dunaliella sp. can efficiently cover the protein requirements of the Mediterranean mussel, Mytilus galloprovincialis during the growth cycle.

Cost production and profitability analysis was performed for a marine fish farm, located in M’diq Bay, in Morocco. Currently, it is the alone farm in operation on Moroccan Mediterranean cost while three others had been ceased their activity. Created in 1998, it has experienced three main periods during its history, start-up period, followed by a crisis period followed by a recovery period on which the present study has been focused on. Production costs analysis has shown financial results yielding a very low profitability (0.24%). Two main constraints were found to be relevant, one environmental related to the weak local annual seawater temperature profile (18°C in average, 14-21°C in range) and the other technical related to feed and fingerlings management. The use of SGR and TGC tools, based on real growing and production data, have allowed to establish suitable start-up date for annual batches. Feed and fingerlings constraints have analysed in order to contribute in production costs improvement. Results showed that total costs could be reduced and profitability improved following pertinent inputs management optimization, marketing strategies improvement and production plan adjustment. Support measures provided by public powers offer suitable opportunity to improve farm’s financial results.