Feeding ecology of Sepiella maindroni based on stomach contents analysis and stable isotope

Sepiella maindroni was once an important economic species along the coast of China, but its resources were exceedingly depleted due to unreasonable exploitation, in addition, the natural habitat of S. maindroni is also being destroyed. To prevent resource recession, relevant departments were restored by enhancing and releasing conservation measures. After several years of efforts, it’s a sure sign of resource recovery initial. In order to understand the feeding conditions of S. maindroni after resource changes, 278 samples were collected from Zhongjieshan Islands in October 2021, and their feeding habits were analyzed by stomach contents. The results of stomach contents showed that the S. maindroni mainly feed on seven groups, including fish, shrimp, and so on, among which shrimp account for the largest proportion (IRI=45.04%), followed by fish (IRI=26.74%) and crab (IRI=24.37%). Stable isotope was also used to analyze S. maindroni for revealing the long-term feeding characteristics of long-term feeding characters. The δ¹³C values of the S. maindroni ranged from −18.21‰ to −15.85‰, with an average value of −17.01‰±0.68‰. The δ¹⁵N values ranged from 8.19‰ to 12.28‰, with an average value of 10.18‰±1.01‰. Pearson analysis showed that the δ¹³C value of muscle was not significantly correlated with the mantle length, but the δ¹⁵N value was significantly positively correlated with the the mantle length (P<0.01). According to the δ¹⁵N value, the average trophic level of the S. maindroni in the Zhongjieshan Islands was 3.34±0.31. Stable stable isotope values showed that the contribution rate of food source from high to low is Zooplankton, Cephalopod, Crustaceans, fish and Shellfis. As the mantle length changed, the S. maindroni tended to feed on higher trophic level baits, such as fish and Cephalopods. S. maindroni has extensive feeding habit, moreover, it also has to do with the species richness of the ocean where it lives. With the development of the individual, the feeding organs and digestive organs gradually mature, and the activity and feeding ability are enhanced, and the predation ability is stronger. The bait organisms tend to be small fish and Cephalopods. In this study, the ecological characteristics of S. maindroni in the waters of Zhongjieshan Islands were described, which can provide basic information for the resource recovery of this species and the structural characteristics of the food web in this area.