Cannibalism as a feeding strategy for mantis shrimp Oratosquilla oratoria (De Haan, 1844) in the Tianjin coastal zone of Bohai Bay

Abstract

17A representative semi-enclosed bay of China, Bohai Bay has experienced severe 18 interference in recent decades and is under threat from rapid human development. 19 Although the mantis shrimp Oratosquilla oratoria plays an important role in the 20 ecosystem and fishery, its feeding ecology and the impact of habitat changes on its 21 feeding habits are poorly known. In this study, we sought to identify the prey 22 consumed by O. oratoria through the separation of stomach contents and to describe 23 its trophic ecology during maturation, from March to July, in the Tianjin coastal zone 24 of Bohai Bay. A total of 594 specimens were collected and 347 (58.59%) stomachs 25 were found to have food remains. More than half of the O. oratoria individuals had 26 poor feeding activity, and the degree of feeding activity of females was higher than 27 that of males, but there was no significant difference in the visual fullness index and 28 the fullness weight index (FWI) between sexes for each month. And the feeding 29 activities of O. oratoria were consistent over the study months. A total of 207 prey 30 items yielded 231 readable sequences and 24 different taxa were identified. Prey 31 detected in O. oratoria consisted mainly of crustaceans, which accounted for 71.86 % 32 of the clones detected; 16.02% corresponded to fishes, 8.23% corresponded to 33 mollusks and the remaining 3.90% corresponded to other marine organisms. 34Cannibalism (occured frequently, 69.08%) in this study was noticeably higher than 35 that seen in previous studies and confirmed that cannibalism may be a significant 36 feeding strategy in the mantis shrimp O. oratoria in the Tianjin coastal zone of Bohai 37 Bay. The ecological environment in Bohai Bay has been affected by anthropogenic 38 activities and the macrofaunal biodiversity and abundance have noticeably declined, 39 which might make the food scarce for the mantis shrimp O. oratoria. Then, the 40 starvation obviously increased cannibalistic tendencies. 41 42It is a benthic, neritic and burrowing shrimp that is found on muddy bottoms in the 46 coastal waters of Siberia, Korea, China, Japan, Vietnam, and Australia [1, 2]. It has 47 become a commercially important species in these regions. 48In Bohai Bay, the mantis shrimp is heavily caught by bottom-trawl and trammel 49 nets, whose annual catches account for more than one-third of the crustacean catches 50 in the past ten years [3]. A substantial decrease in the stock size of large female 51 shrimps has been apparent since the fishing industry catch, in which larger individuals 52 are overexploited, and the season of spawning fastigium is delayed to mid-to-latter of 53 May, while some female shrimps also spawn into September [1,[4][5][6]. The abundance 54 of mantis shrimp pseudozoea is low before July [4, 6]. 55 Few studies have focused on the feeding ecology of O. oratoria. Its trophic 56 ecology in the coastal waters of the Chinese open sea, Huanghai Sea and Donghai Sea 57 was described with crustaceans being the main prey group, followe...