# Automated Monitoring of Bluefin Tuna Growth in Cages Using a Cohort-Based Approach
## 4 Conclusions and Further Work  
The autonomous monitoring system operational from 28 July 2020 to 23 May 2021 in a fattening cage at Grup Balfego (West Mediterranean) demonstrated its capacity to deliver thousands of accurate automatic measurements daily under ordinary circumstances using stereoscopic vision. This abundance of data enabled a detailed examination of tuna size evolution. It was determined that analysing the evolution of the median and percentiles over time is inadequate for accurately estimating the growth of a fish population with varying ages and lengths. Instead, a modal analysis, employing [PERSON]'s method, was applied to identify different cohorts prior to analysing length and width evolution. The results indicated that from July 2020 to May 2021, the growth in length ranged approximately between 6 and 26 cm (2% to 21%), and the growth in width varied between 3.0 and 8.0 cm  
Figure 11: Estimated weight using SFL-A-W relationship (M3) from [11; 12] with automatic system measurements in July 2020 and May 2021. Figure 10: Comparison of measured weights (W) at harvesting (May 2021), estimated weights using SFL-W relationship from [10] with SFL from harvests, and estimated weights using SFL-A-W relationships (M3) from [11; 12] with automatic system measurements (SFL and A). (9% to 17%), depending on fish length. It was proven that, due to the special conditions in cages, both length and weight exhibited higher annual growth compared to the wild. Additionally, variability in fattening levels among fish of the same lengths was observed. Moreover, utilising fish length and width enhanced the accuracy of weight estimation. Expressions derived from sacrificed fish in our earlier work [11; 12] based on formulae relating weight and dimensions (length, width, and height) of BFT tuna fattened in captivity were validated. The results reinforced the notion that, for cage-farmed tuna, incorporating length and width dimensions refines weight estimation. While the automatic system was applied to size adult Atlantic bluefin tuna, the procedure could be adapted for other species by adjusting segmentation parameters, blob filtering criteria, and the geometric model. As part of our future work, we intend to leverage deep learning techniques to expedite computing time, enabling the system to operate effectively in commercial operating environments. Additionally, new algorithms for fish tracking and counting will be developed. While this study provides initial positive results and conclusions regarding fish growth in cages, it underscores the need for a more complex model. This expanded model should delve into various aspects of growth, such as actual versus expected growth in the wild, growth linearity, the evolution of the condition factor, and the adaptation to changes in the imaging setup, water temperature, and turbidity. Such a comprehensive investigation requires a dedicated project with diverse setups, encompassing feeding regimes and fish ages, among other factors. Conceptualisation, G.-A.-G., I.P.-A., V.E. and F.A. ; methodology, P.M.-B., G.A.-G., I.P.-A. and V.E. ; software, P.M.-B., J.M.-P., V.P.-P., A.M.-F. and V.A.-V.; validation, P.M.-B., V.P.-P., A.M.-F. and F.A. ; formal analysis, P.M.-B., V.P.-P., A.M.-F. and F.A. ; investigation, P.M.-B., J.M.-P., V.P.-P., A.M.-F. and P.O.-C.; resources, G.A.-G., P.O.-C., I.P.-A., V.E. and F.A. ; data curation, P.M.-B., V.P.-P. and A.M.-F; writing--original draft preparation, P.M.-B. ; writing--review and editing, G.A.-G., V.E. and F.A. ; visualisation, P.M.-B., V.P.-P., A.M.-F. and F.A. ; supervision, G.A.-G., I.P.-A., V.E. and F.A. ; project administration, G.A.-G. and V.E. ; funding acquisition, G.A.-G., I.P.-A., V.E. and F.A. All authors have read and agreed to the published version of the manuscript. This study forms part of the ThinkInAzul programme and was supported by the MCIN with funding from the European Union's NextGenerationEU (PRTRTR-C17.I1) and the Generalitat Valenciana (THINKINAZUL/2021/007, THINKINAZUL/2021/009, and AICO/2021/016).