Data on growth performance and survival of black scallops (Mimachlamys varia (Linnaeus, 1758)) reared under suspended conditions in waters of the Basque coast (SE Bay of Biscay)

This dataset presents the growth performance and survival of black scallops (Mimachlamys varia) reared under suspended conditions using different growing systems at two different sites of the Basque coast (SE Bay of Biscay). Monthly data on environmental variables (temperature, salinity, oxygen saturation and chlorophyll “a” concentration) in the water column is also provided. Juveniles obtained from a hatchery with a mean length of 23.6 ± 4.12 mm and a mean wet weight of 2.06 ± 1.09 g were deployed in cages and pots at two experimental sites: a raft installed in sheltered waters and a longline located at offshore waters. The experiment was run from June 2019 to August 2020 (447 days). Black scallops were collected every one or two months and at each sampling time a cage and a pot were retrieved from each site. Black scallop survival and growth performance were determined. This database is useful for (i) assessing the viability of the species on the Basque coast, (ii) determining the time needed for black scallops to reach commercial size, (iii) promoting species diversification in the emerging offshore aquaculture sector in the Basque Country and, (iv) for comparison with other biogeographical areas.


a b s t r a c t
This dataset presents the growth performance and survival of black scallops ( Mimachlamys varia ) reared under suspended conditions using different growing systems at two different sites of the Basque coast (SE Bay of Biscay). Monthly data on environmental variables (temperature, salinity, oxygen saturation and chlorophyll "a" concentration) in the water column is also provided. Juveniles obtained from a hatchery with a mean length of 23.6 ± 4.12 mm and a mean wet weight of 2.06 ± 1.09 g were deployed in cages and pots at two experimental sites: a raft installed in sheltered waters and a longline located at offshore waters. The experiment was run from June 2019 to August 2020 (447 days). Black scallops were collected every one or two months and at each sampling time a cage and a pot were retrieved from each site. Black scallop survival and growth performance were determined. This database is useful for (i) assessing the viability of the species on the Basque coast, (ii) determining the time needed for black scallops to reach commercial size, (iii) pro-moting species diversification in the emerging offshore aquaculture sector in the Basque Country and, (iv) for comparison with other biogeographical areas.
© 2022 The Author(s

Value of the Data
• The survival data presented herein are useful for understanding the feasibility of black scallop ( Mimachlamys varia ) in offshore waters of the Basque coast and is of importance for the diversification of mollusc species. • Growth performance of black scallop presented in these data are useful for estimating the culture period necessary for commercial farming of black scallops on the Basque coast. • Data on growth and survival of black scallops reared under different culture systems at two different sites are valuable for selecting the best location and culture system for black scallops on the Basque coast.
• Environmental variable data are helpful to understand the growth performance and survival of black scallops reared in offshore waters of the Basque coast. • The dataset is useful for researchers in aquaculture and shellfish producers as information on black scallop culture under suspended conditions is scarce.

Data Description
Here we provide a dataset of the survival and growth performance of black scallops reared from June 2019 to August 2020 under different growing systems at two different sites of the Basque coast (SE Bay of Biscay), together with environmental variables data recorded in the water column. The raw data is available at https://data.mendeley.com/datasets/rptzp8pxx4/1 .
The raw data consists of three tables: Table "Growth": Growth performance of black scallops reared under suspended conditions using different growing systems at two different sites of the Basque coast. Table "Survival": Survival of black scallops reared under suspended conditions using different growing systems at two different sites of the Basque coast.
Table "Environmental variables": Environmental variables measured monthly in offshore waters of the Basque coast.
The data allow to assess the survival (e.g., Fig. 1 ) and growth performance (e.g., Fig. 2 ) of black scallops reared under suspended conditions in waters of the Basque coast. Black scallops reached commercial size in less than one year of culture on the Basque coast (starting from a mean length of 23.60 mm), which is consistent with another similar dataset of black scallops reared under suspended conditions in the Ionian Sea, Southern Italy [5] .

Experimental Design, Materials and Methods
The study was conducted at two experimental sites for aquaculture studies on the Basque coast: a raft installed in sheltered waters in the harbour of Mutriku, and a longline located in offshore waters of Mendexa, at two miles off the coast ( Fig. 3 ). Black scallop juveniles were obtained from a hatchery in Brittany (France), with an initial mean length of 23.60 ± 4.12 mm and an initial mean wet weight of 2.06 ± 1.09 g. Black scallops were transported from Brittany to the Basque Country in boxes covered with towels moistened with seawater ( Fig. 4 ). After a 12 h journey, black scallops were distributed in cages (415 mm diameter, 80 mm height, 8 mm mesh size) and pots (636 × 245 × 140 mm, 6 mm mesh size) ( Fig. 5 ). 160 individuals were introduced in each cage, while 360 individuals were placed in pots, which is the equivalent to 1183 individuals m −2 in cages and 2246 individuals m −2 in pots, respectively. At each site, cages and pots with black scallops were deployed at 3 m depth ( Fig. 6 ). The experiment was run from June 2019 to August 2020. Samplings were carried out approximately every one or two months, but the frequency was not exactly the same at both sites during the first months of the experiment. At each sampling time, one cage and one pot were retrieved from each site ( Fig. 7 ) and survival was calculated counting live organisms with respect to the initial number of organisms. Subsequently, a subsample of 100 black scallops was used to determine the shell height using a digital calliper and the wet body and tissue weight with a balance ( Fig. 8 ), except when live individuals were less than 100 (then all individuals were measured). On the other hand, environmental   variables (temperature, salinity, oxygen saturation and chlorophyll "a") were measured monthly on the longline at 3 m depth where black scallops were deployed using a CTD sensor.