通过小型探鱼无人船探测大型围网养殖区大黄鱼的分布特性

为了明确大黄鱼在大型围网养殖区内的分布规律，实验通过集成、构建具备大黄鱼探测以及水温、盐度、光照、pH、溶解氧等海洋环境探测功能的小型探鱼无人船，并在浙江省舟山市桃花岛大黄鱼围网养殖基地内开展了6次现场监测。结果发现，(1)在水平范围，大黄鱼主要分布在大型围网养殖区内礁石丰富且水流相对较缓的区域；(2)在垂直范围，大黄鱼主要分布在加权相对深度0.6～0.9的养殖海区中下层；(3)围网养殖海区内温度、盐度、pH、溶解氧等海洋环境条件整体变化较小，大黄鱼往往分布在光照强度分别为(5 921±2 702)、(50 799±50 988)、(5 990±542)、(3 494±695)、(6 836±4 761)及(15 395±5 531)lx等相对较弱的区域。本实验首次通过小型探鱼无人船系统研究了围网养殖区内大黄鱼的分布特性及相应的海洋环境因子对其分布的影响，结果为大黄鱼围网养殖区的操作平台选址、投喂管理、起网设计等提供了依据。

Distribution detection of Larimichthys crocea cultured in large net-enclosure aquaculture by Small Unmanned Surface Vehicle

Larimichthys crocea is one of the four traditional marine economic fishes in China. It is rich in protein, vitamins and unsaturated fatty acids. It is a high-quality marine aquatic product and the main cultured fish species in China. The main aquaculture methods of L. crocea are nearshore net cage, offshore net cage and net enclosure in shallow sea. Among them, the large-scale net-enclosure aquaculture is a newly developed high-end marine aquaculture mode in recent years. Several net-enclosure facilities have been constructed in Shandong province, Fujian province and other places in China for its advantages in providing the right conditions for growth which closer to the original environment for fishes. However, it is difficult to precisely determine the positions of the fishes and to feed and harvest L. crocea for its large aquaculture spaces. Therefore, it is of great significance in application to study the distribution characteristics of L. crocea in large-scale net-enclosure aquaculture culture. In order to obtain the distribution characteristics of L. crocea in the large-scale net-enclosure aquaculture culture area, a multi-function small unmanned vehicle equipped with the sensors of sonar fish detector, temperature, salinity, pH, illumination and dissolved oxygen has been successfully developed. Among them, the fish detector (DE-FR01 200 kHz) is consisted of the single beam energy converter which can integrate transmitting and receiving ultrasonic signals. The working principle is that the acoustic signal transmitted by the energy converter propagates in water, when encountering the medium different from water, part of the signal will be reflected back. According to the time between of signal transmission and receiving, it can be used to measure the distance between the target and the energy converter, then analyze and process the echo signal strength(hardness), and through 4G-Network communicates with shore-based system. Finally, the depth and hardness of the target are displayed in the software control terminal. Several field trials have been carried out in Taohua Island, Zhoushan City, Zhejiang Province. By analyzing the detected fish distribution position, water temperature, salinity and illumination of the marine environment in net-enclosure aquaculture culture area, the following conclusions are obtained: 1) In terms of horizontal distribution, L. crocea is mainly distributed in the areas with rich reefs and slow water flow in the large-scale net-enclosure aquaculture culture area;2) in the vertical distribution direction, the L. crocea is mainly distributed in the middle and lower layers of the aquaculture area with weighted relative depth of 0.6~0.9; 3) the overall changes of temperature, salinity, pH and dissolved oxygen are small in the net-enclosure aquaculture culture area(p>0.05). L. crocea is often distributed in areas with relatively weak illumination intensity of 5921±2702lx, 50799±50988x, 5990±542lx, 3494±695lx, 6836±4761lx, 15395±5531lx. In this study, the distribution characteristics of L. crocea in net-enclosure aquaculture culture area and the influence of marine environment on its distribution were studied systematically for the first time. The research results provide the basis for the site selection of operation platform, feeding management and catching design of L. crocea.