Three-Dimensional Reconstruction and Comparison of Three Tuna Species’ Fish Body Structures Based on CT Scanning

To better understand the biological structure of bigeye tuna (Thunnus obesus), albacore tuna (Thunnus alalunga), and longtail tuna (Thunnus tonggol), computed tomography (CT) was used to scan their bodies, and the data are processed by Mimics software. The skeleton, swim bladder, and muscle of the three tuna species are reconstructed in three dimensions. The surface area and volume of the corresponding parts are measured. The results show that the surface areas of the skeleton of longtail tuna, bigeye tuna, albacore tuna accounted for 28.18%, 37.34%, 33.45% of their whole body surface areas respectively; the surface areas of swim bladder accounted for 0, 2.06%, 2.72% of their whole body surface area respectively; and the surface areas of muscle accounted for 71.82%, 60.6%, 63.83% of their whole body surface areas respectively. And the volumes of skeleton accounted for 28.18%, 8.05%, 3.84%, the volumes of swim bladder accounted for 0, 3.44%, 0.92%, and the volumes of muscle accounted for 94.84%, 88.51%, 95.24% of their body volumes respectively. The swim bladder of the longtail tuna has degenerated, while that of the bigeye tuna is conical, exhibiting the highest volume proportion among the three species. In contrast, the swim bladder of the albacore tuna is both flat and elongated, resembling an arc. Additionally, the surface area and the volume of the bigeye tuna’s swim bladder differ significantly from those of the albacore tuna. Regarding skeletal and muscular structures, the bigeye tuna has the highest skeletal volume proportion (8.05%), whereas the albacore tuna exhibits the highest muscle volume proportion (95.24%). These morphological differences are closely associated with their respective habitats. This study demonstrates the potential of CT technology in fish morphological research, providing a reliable, non-invasive method for analyzing internal structures, quantifying organ characteristics and improving the accuracy of acoustic stock assessment.