Investigation on behavioral preferences of Lutjanus erythropterus juvenile towards artificial reef models with different pore shapes and sizes

The construction of artificial reefs is crucial for maintaining marine ecology and protecting fishery resources. The pore shape and size are the key elements for the structural design with a significant impact on the aggregation of fish. We designed and made the artificial reef models with different pore shapes (Round, square, diamond) and different sizes (1.0, 2.0, 3.0, 4.0 cm) for Lutjanus erythropterus, a common reef-dwelling fish in the artificial reef area. Then we observed the attractive effect on the juveniles and observed their behavioral changes in an indoor experimental pool. The results show that without the artificial reef model, the juveniles mainly concentrated in the peripheral area of experimental pool. But when the reef model was placed, the average distribution ratio of the juveniles in the reef area increased significantly (p<0.05). For the pore shape study, there was no significant difference in the average distribution rate of the juveniles in the artificial reef placement area (VI area) among the three treatment groups (p>0.05), with the proportion of the diamond treatment group being the highest (19.84±6.08)%. However, for the pore size study, there were significant differences among the three treatment groups (p<0.05), 4.0 cm size group (About 2.0 times the body height of juvenile) being the highest (25.36±5.04)%, while 1.0 cm size group (About 0.5 times the body height of juvenile) being the lowest (14.54±3.09)%. In terms of activity ability, there were obvious differences between the artificial reef model experimental group and the blank control group. The average speed of juveniles decreased from (13.36±5.21) cm·s⁻¹ in the control group to (4.29±1.59) cm·s⁻¹ in the reef group, the average acceleration decreased from (106.93±69.17) cm·s⁻² to (54.45±21.47) cm·s⁻², and the percentage of activity time decreased from (68.01±8.61)% to (40.29±11.85)%, and all were the lowest in the circular 4.0 cm group, the square 4.0 cm group and the diamond 4.0 cm group. It is showed that at this stage, L. erythropterus juvenile has the strongest tropism to the artificial reef model with a circular pore shape and the size group of 4.0 cm, but the activity level is relatively low, showing the most significant attractive effect.