3. Results
Replies from aquaculture production companies were not as expected; although, overall, they represent the highest percentage (Table 1). Such numbers make clear (a) the excessive confidentiality that surrounds the RAS system industry (regarding to their design and operational methods); and (b) the lack of interest supporting the study, as many refusals to cooperate were received. The lack of a specific data compilation of RAS systems companies in Europe (corroborating the statement made by Martins et al., 2010) made it difficult to locate and contact them all.