1. The bigeye tuna is relatively large, with a body length of1-2m and a weight of over100kg. Its body is streamlined, its back is silvery white and its abdomen is white. Tuna is small, with a body length of 0.5- 1.5m and a body weight of 10-30kg. Its body is streamlined, its back is blue and black, and its abdomen is silvery white.

2. The dorsal fin of large tuna is long and firm, with obvious curvature; Tuna's dorsal fin is short and straight, without obvious bending.