[The continuous trophic spectrum of food web in Dalian marine area, China.]

This study analyzed the values of δ¹³C and δ¹⁵N by the application of stable isotope technique from the marine mammals (Phoca largha, Neophocaena asiaorientalis sunameri, Balaenoptera acutorostrata) and major biological species in Dalian marine area based on the animals collected due to stranding and death after bycatch from January, 2008 to June, 2017, and the fisheries resources investigation between autumn, 2016 and spring, 2017 in the same area. The trophic level was then calculated in order to establish the continuous trophic spectrum of the food web in Dalian marine area. The results showed that the value of δ¹⁵N ranged from 8.0‰ to 14.7‰ and the value of δ¹³C ranged from -21.1‰ to -16.7‰ of the food web in Dalian marine area. The major biological species could be categorized into three groups, namely primary consumer, secondary consumer and top predator. The analysis of δ¹⁵N revealed that the trophic level ranged from 2.63 to 4.59 for the major biological species. The trophic level of B. acutorostrata, N. asiaorientalis sunameri, P. largha, echinoderm, cephalopods, gastropod, bivalve, crustacean and fish were 3.16, 4.11, 4.25, 3.24-3.84, 3.81-3.93, 3.65-4.13, 2.63-3.15, 3.58-4.12 and 3.20-4.59, respectively. The characteristics of the trophic structure demonstrated that the primary consumer was bivalve, the secondary consumers were B. acutorostrata, cephalopods, Echinoderms, gastropod and crustacean, and top predators were N. asiaorientalis sunameri, P. largha and fish. The value of δ¹⁵N increased with the increase in the body length, indicating the feeding of N. asiaorientalis sunameri tended to be at a higher trophic level with the growth and feeding ability enhanced. This study established the continuous trophic spectrum of food web in Dalian marine area and would provide the information for the marine mammal and fisheries resources protection.