Research On The Swimming Behavior Of Antarctic Krill Based On Aquarium Experiment

Antarctic krill, usually refers to is the Euphausia superba Dana,as the perennial large crustacean zooplankton, widely distributed in the waters of the Antarctic continental shelf ring and mainly concentrated in the 200 m in shallow water and live in a cluster.Antarctic krill is key species in the southern ocean ecosystem, the change of the population will have a direct impact on the changes in the southern ocean ecosystem. At the same time, Antarctic krill rich in nutritional value, known as human quality protein resources, the commercial fishing value can not be underestimated. Because of the important position in the southern ocean ecosystem and its value as an important fishery resources, more and more people pay attention to Antarctic krill. At the same time, the research on the Antarctic krill has become a issue, such as the Antarctic krill biology, ecology, resource distribution has been gradually developed. But so far, it is still not comprehensive and accurate understanding of their habits and behavior. The study of domestic scholars on the Antarctic krill behavior is even less. Because of the conditions, underwater use HD camera real-time tracking and recording krill behaviour is very difficult, so the use the tank(or sink) to observe the behavior of individual krill in artificial conditions, is one of the present feasible method.In order to research the Antarctic krill swimming behavior, to further understand the biological characteristics of Antarctic krill, the research based on“Antarctic marine living resources development and utilization”project, we carry out experiments in February to April 2014, 2015 February to June in Shanghai Kaichuang fishery company trawling vessel.We use the tank simulate the natural environment to temporary culture the krill, underwater shooting record the krill swimming state, expressed swimming characteristics, to understand the krill swimming behavior; on the other hand, we refer to fish swimming speed determination method for the determination of krill critical swimming speed. The main conclusions of this study include:(1)There are two kinds of Antarctic krill swimming, which rely on the gastropod paddling and tail bending fold forward, the gastropod swaying always has a pair of gastropods at maximum thrust, the bending angle of different gastropod each; the gastropod swimming speed is relatively stable, while the tail swimming can produce larger speed in instantaneous, but is only one kind of stress so when the reaction in krill; provide the swimming speed(V) of gastropod and body length(L) is proportional to the linear regression equation is V=0.79L-20.96(R2 = 0.8528, n = 29, P < 0.05); in a certain range, change the frequency of pleopod swaying will change krill swimming speed, swimming speed and swaying frequency had a remarkably positive correlation(P < 0.05); when the swimming speed of more than 15cm/s,increasing the oscillation frequency has not changed its foot swimming speed, at this time to improve The swimming speed can only rely on increase the swing range of gastropod.(2)With the increasing of the length, the settling velocity of death krill increased significantly, when the body length of krill to 55 mm, the settling velocity up to 5.22cm/s, even the smallest individual krill, settlement speed is 1.87cm/s, the average settling velocity is 3.45cm/s; relationship between body length and the sinking speed is V= 0.0055Lj1.7143(P < 0.05, R2=0.927, n=59); statistical analysis of the frequency distribution of swimming angle, krill swimming angle range between 0~150 °, which means that there are some krill swimming pitch condition, most of the krill swimming angle between 37.5~62.5 °; base on the GAM model analysis of the relationship between the swimming angle and its body length and body weight, the contribution rate of krill swimming angle is more relative with body length than body weight; in to keeping in the water, krill gastropods were pulling power and when the gastropod to power its own buoyancy and its weight is equal, krill can be in a state of suspended, suspension angle ranged from 50 to 56 degree; when swimming angle is less than 50°krill have forward speed, speed was maximum at close to 0°; when the angle is larger than 56 degrees, generate backward horizontal displacement, when the velocity is small, the maximum value is only 1.90cm/s; the light have influence on the krill swimming angle, when hovering krill is above the irradiation of the light, which exhibit normal hover state, 53.5°angle; when light in side illuminated, krill cannot successful hovering, drop value at the bottom of the water tank; when light from below the irradiation, krill swimming angle will be overturned 180°, immediately and then fall down to the bottom of the tank; in the dark state krill can still maintain a normal state of swimming.(3)In the duration of 15 minutes, the velocity increment is 0.5BL/s, the measured krill maximum absolute critical swimming speed is 18.43cm/s, the maximum relative critical swimming speed is 5.18 BL/s, the average absolute critical swimming speed of 9.72 ±5.2cm/s, and the average relative critical swimming speed of 3.30±1.16BL/s; absolute and relative swimming speed with body length increases(P<0.05), 40 mm and 45 mm, 45 mm and 50 mm group average ucrit value has significant difference, the average value of other groups between the critical swimming speed is smaller; because of fatigue after the increase of krill could not complete the flow of swimming time with swimming speed decreased, a logarithmic function relationship between the two, formula: T =-3.1114Ln(V) +13.85(R2=0.8654, P < 0.05), swimming speed faster, the shorter sustained swimming time after fatigue; 45±2.5mm, velocity increment is 0.5BL/s, duration of 5, 10, 15, 20, 25 min, with the duration extension increases the experimental group 1 average relative critical swimming speed is decreased first and then increased, when the duration is 15 min, experimental group 1 krill average absolute critical swimming speed maximum, when the duration is 25 min, the experimental group 1 krill average absolute critical swimming speed minimum; body length 45±2.5mm, duration 15 min, velocity increment set 0.25, 0.75, 1, 0.5 1.25BL/s,with the speed of incremental extension increases average the experimental group 2 relatively critical swimming speed is decreased first and then increased, when continuous velocity increment is 0.5BL/s, the experimental group 2 krill average absolute critical swimming speed maximum, when the velocity increment is 1.25BL/s,the experimental group 2 of krill average absolute critical swimming speed minimum.