3.1. Main issues of RAS systems
As cited above, the technology is very dependent on the life stage of the cultured animal, e.g. it is different to manage newly hatched or small size animals; this is why on-growing and hatchery are considered separately, from here onwards. Cross-tabulating certain questions of the questionnaire it was shown that issues are dissimilar between them. In any case, it is difficult to assess the exact cause of each problem, as the information provided by the producers is not sufficiently detailed and different sources could result in the same consequence. For instance, water quality issues caused mainly by mechanical problems are usual in hatcheries (3 out of 3), whilst badly designed equipment is the most common cause of problems for on-growing systems (5 out of 6). Moreover, whether referring to biological or management problems (i.e. internal
or external causes), the answers obtained reveal that issues arise from an initial poor design. For researchers and consultants, clustering the most common issues cited indicates in this order, the main weaknesses: wrong system approach (i.e. inaccurate parameter design calculations, and being too optimistic); inappropriate management (including lack of training); maintenance issues (poor water qualities achieved); and poor system designs (e.g. equipment
selection). Likewise, the lack of response to unforeseen circumstances is also a common issue.