The Study Of Auditory Capacities In Fish

Sound plays a very important role in many marine organisms,especially in fish sound communication,location,foraging and defense behaviors.The acoustic signals can be convert into electrical signals by sensory hair cells in the inner ear of fish.The study of fish auditory has been for more than a century,and early researchers have argued that fish do not have inner ear and cannot hear the sound.By now,studies from different aspects,such as behavior,anatomy,and electrophysiology have confirmed that fish not only can hear the sound,but also have the ability to feel the sound pressure,particle vibration,identify the frequency,identify the direction and so on.On the study of fish auditory characteristics,the disciplines that have been covered include: zoology,acoustics,anatomy,physiology,neurophysiology,animal psychology,fishery science,etc.In the past,people studied the fish auditory characteristics,mainly to improve the existing fishing gear or the development of new fishing gear to improve fishing efficiency.Nowadays,with the continuous decline of global fishery resources,due to the protection of the environment and the sustainable development of the world’s fishery,to develop and management the acoustic taming marine ranching which are the mainly study objects in hearing capacities of commercial fishes in China.Moreover,to make our measurement technology and experimental methods in fish hearing threshold research to reach the international level,and also to provide a reference for using the acoustic methods in fish domestication and control,fish release,and dynamic management of fishery resources in the future.In this paper,electrophysiological methods of electrocardiogram(ECG)and auditory brainstem response(ABR)method are used to study the hearing capacities of Paralichthys olivacues,Hexagrammos otakii,and Carassius auratus Linnaeus in difference species,body shape type,physiological structure,and auditory organ.To demonstrate the applicability of different experimental methods on different experimental objects,and accurate analysis the hearing thresholds in these fishes.The main results are as follows:1.Study on hearing capacities of Paralichthys olivacues by using ECG methodThis study object is to use ECG method to measure the hearing threshold of Paralichthys olivacues by fish auditory sensation measuring devices.The acoustic stimulus frequencies of the study are set up as follow: 60 Hz,100 Hz,150 Hz,200 Hz,300 Hz,400 Hz,500 Hz,700 Hz,for measuring the hearing threshold of 20 ind text fish,and then the audiogram could be drawn and analyzed.The ECG signal of 20 ind tex fish have all been obtained and the results are as follow: The hearing threshold of Paralichthys olivacues performances a “V” shape from 60 Hz to 700 Hz frequency bandwith.In 60~200 Hz frequency bandwith the hearing threshold is lower than 100 d B(re 1μPa),the most sensitive frequency is 100 Hz,and the hearing threshold is 94.1±1.61 d B,the fish is more sensitive in this frequency bandwidth;Above 300 Hz frequency bandwith,the hearing threshold is increased with the frequency and the value is 107.5±1.61~134.85±1.66 d B,the hearing sensitive becomes gradually decline.2.Study on hearing capacities of Hexagrammos otakii by using ECG methodThis study object is to use ECG method to measure the hearing threshold of Hexagrammos otakii by fish auditory sensation measuring devices.The acoustic stimulus frequencies of the study are set up as follow: 60 Hz,100 Hz,150 Hz,200 Hz,300 Hz,400 Hz,500 Hz,700 Hz,1000 Hz,for measuring the hearing threshold of 20 ind test fish,and then the audiogram could be drawn and analyzed.The ECG signal of 20 ind text fish have all been obtained and the results are as follow: The hearing threshold of Hexagrammos otakii performances a “V” shape from 60 Hz to 1000 Hz frequency bandwith.In 60~200 Hz frequency bandwith the hearing threshold is lower,and the most sensitive frequency is 150 Hz,the hearing threshold is 96.5±1.57 d B;the secend more sensitive frequency bandwidth is 300~400 Hz,the hearing threshold is 105±1.26~106.1±1.36 d B;Above 500 Hz frequency bandwith,the hearing sensitive becomes gradually decline,the hearing threshold is from 116.4±1.23 d B up to130.2±1.63 d B.3.Study on hearing capacities of Carassius auratus Linnaeus by using ECG and ABR methodsIn this study,the ECG and ABR methods have been using for the comparative study the auditory characteristics of Carassius auratus Linnaeus.In the ECG method,the acoustic stimulus frequencies of the study are set up as follow: 100 Hz,200 Hz,300 Hz,400 Hz,500 Hz,600 Hz,700 Hz,800 Hz,900 Hz 1000 Hz,1500 Hz,2000 Hz for measuring the hearing threshold of 20 ind test fish;and in the ABR method the acoustic stimulus frequencies of the study are set up as follow: 100 Hz,200 Hz,300 Hz,500 Hz,800 Hz,1000 Hz,1500 Hz,2000 Hz for measuring the hearing threshold of another 20 ind test fish,and then the audiogram could be drawn and analyzed.The results show that: The hearing threshold of Carassius auratus Linnaeus performances a “W” shape from 60 Hz to 2000 Hz.In the ECG method,in 100~200 Hz frequency bandwidth the hearing threshold is 98±0.84~115±0.72 d B;in 300~800 Hz,the Carassius auratus Linnaeus become more and more sensitive and the most sensitive frequency is 800 Hz,and the hearing threshold is 70±0.84 d B;Above 800 Hz frequency bandwith,the hearing sensitive becomes gradually decline.In the ABR method the result of auditory sensitive trend similarty to the ECG method,the most sensitive frequency is also in 800 Hz and the hearing threshold is 76±0.90 d B,but higer than the ECG method as 3.5±0.75 d B(P>0.05).To sum up,for the sensitive frequency of these fish,Paralichthys olivacues is at 100 Hz,Hexagrammos otakii is at 150 Hz,and Carassius auratus Linnaeus is at 800 Hz.For the hearing threshold,Carassius auratus Linnaeus is the minimum,under150 Hz the Paralichthys olivacues is lower than the Hexagrammos otakii,but over 150 Hz the Hexagrammos otakii is lower than the Paralichthys olivacues.The body type of Paralichthys olivacues is flat and Hexagrammos otakii is spindle they all have no swim-bladder,they can use lateral line to sense the water particle vibration and more sensitive to the low frequency sounds,but not sensitive in sense the sound pressure,so that the hearing capacities are relatively poor.Because of the swim-bladder and the Weber’s organs Carassius auratus Linnaeus,it has a wide sense in frequency bandwidth and an outstanding hearing capacity.In this study,duing to limited experimental conditions,the bio-impedance of the test fish could not be measured,but according to the physical resistance law and experimental verification,the voltage of electric stimulus and shock times having been optimizing for different fish species;Second,the ECG and EEG signals under free exercise conditions is unable to obtain,so that we cannot to study the further scientifically verify the impact of anesthetic agents on hearing thresholds of fish;Finally,because the hearing threshold is measured in the laboratory,it could not fully represent the actual response in the field study such as the effective range of sound domestication.In consideration of the sound characteristics in sound pressure and particle motion,we will do the correlational studies in the future study of fish hearing capacities.We will try to obtain the real-time tracking for ECG and EEG signals in free swimming fish to measuring the hearing threshold in fishes.Therefore,to study the auditory capacities in commerce speices,it could provide a reference for controlling fish behaviors,creating a moder marine fishery with ecology health,eco-freidly and biological resource conservation,to ensure the harmonious development in human and marine organisms.