基于高通量测序的象山港海域黑鲷(Acanthopagrus schlegelii)食性分析

选取象山港黑鲷个体为研究对象，以18S rDNA为靶标，利用Illumina Miseq高通量测序方法研究黑鲷饵料生物组成特征，分析不同龄组黑鲷的食性异同。通过序列比对，共在黑鲷胃含物中鉴定出41个属中的62种饵料生物，分属9个门，其中节肢动物门（Arthropoda）、绿藻门（Chlorophyta）和软体动物门（Mollusca）是黑鲷饵料生物的优势组成门类。从饵料生物相对丰度和出现频率上分析，石莼（Ulva lactuca）、熊本牡蛎（Crassostrea sikamea）、胸刺水蚤（Centropages hamatus）、日本蟳（Charybdis japonica）、毛蚶（Scapharca subcrenata）和褐菖鲉（Sebastiscus marmoratus）是黑鲷的优势饵料物种，所占饵料生物总相对丰度的比重达60.90%。相似性分析检验（ANOSIM）结果显示：1至4龄黑鲷个体的饵料生物组成不存在显著性差异。与传统食性分析方法相比，高通量测序法在黑鲷饵料生物检测灵敏性上显现了较为明显的优势，保障黑鲷等重要物种的种群稳定对于该海域具有重要的生态和经济意义。

Diet composition and feeding habits of black sea bream (Acanthopagrus schlegelii) in Xiangshan Bay based on high-throughput sequencing

Xiangshan Bay is a semi-closed bay in the central coast of Zhejiang Province, China. It is also a centralized distribution area of various fishery resources, and many economic fish species breeding there every year. However, due to long-term overfishing, ocean development and environmental pollution, deterioration of ecological environment was found in this sea area, which also caused the increasingly recession of local fishery resources. In recent years, after fishery resources conservation, fishery resources in this water have been restored. It also provides a good habitat for reef-loving species such as the black sea bream Acanthopagrus schlegelii. A. schlegelii is an important fish species targeted by recreational and commercial fisheries in Xiangshan Bay. Maintaining population stability of this species is economically and ecologically important for the embayment. Knowledge of the feeding ecology is of great value for conservation strategies, as it is thoroughly linked to subjects such as resource partitioning, habitat preferences, prey selection, predation, competition and energy transfer within and between ecosystems. However, relatively little work has been done on this aspect in A. schlegelii. In this study, 21 individuals of A. schlegelii were collected in Xiangshan Bay, and diet composition and feeding habits were analyzed by high-throughput sequencing methods targeting 18S rDNA gene. By Illumina high-throughput sequencing, 913,254 target fragments with length of about 420 bp were obtained. The minimum sequence number of samples was 30,826, while the maximum one was 52,374. A total of 554 OTU (operational taxonomic units) were obtained from 21 samples after clustering. And 62 species in 9 categories were identified in the stomach contents of this species after sequence alignment, in which Mollusca, Arthropoda and Chlorophyta exhibited the highest abundance, followed by Chordata, Platyhelminthes, Bacillariophyta and Annelida. Ulva lactuca, Crassostrea sikamea, Centropages hamatus, Charybdis japonica, Scapharca subcrenata and Sebastiscus marmoratus were dominant prey items for A. schlegelii in Xiangshan Bay. The above prey items accounted for 60.90% of the total abundance of gastric contents. In addition, a number of species, including Caprella scaura, Oithona sp., Melosira sp., Cyclotella sp., Chlorella stigmatophora, Picochlorum sp., Torodinium robustum, and Chromadorina sp., with quite low abundance were also detected. These prey items were distributed in different ecological communities, including macroalgae, shellfish, zooplankton, phytoplankton, macrozoobenthos, fish, and crab. These data suggests that A. schlegelii is a relatively large omnivorous consumer. Result from the analysis of similarities (ANOSIM) showed no significant difference in diet composition for fish among different age groups. This indicates that A. schlegelii did not alter feeding habits after 1 year old. Considering the limited sample size, however, further studies are still needed to address this conclusion. Compared with the traditional analysis methods, high-throughput sequencing has the characteristics of less sample demand, less workload, and more species detection. Meanwhile, due to its sensitivity, some species with low abundance that could not be found by traditional methods can also be detected. Hence, high-throughput sequencing technology has obvious advantages in fish diet studies and can provide strong support for marine organisms feeding and ecological studies.