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1.
Small cetacean bycatch in gillnet fisheries may be reduced by deterring odontocetes from nets acoustically. However, different odontocete species may respond differently to acoustic signals from alarms. Therefore, in this study a striped dolphin and a harbour porpoise were subjected simultaneously to sounds produced by the XP-10 experimental acoustic alarm. The alarm produced 0.3s tonal signals randomly selected from a set of 16 with fundamental frequencies between 9 and 15kHz, with a constant pulse interval of 4.0s (duty cycle 8%) and a Source Level range of 133-163dB re 1muPa (rms). The effect of the alarm was judged by comparing the animals' respiration rate and position relative to the alarm during test periods with those during baseline periods. As in a previous study on two porpoises with the same alarm, the porpoise in the present study reacted strongly to the alarm by swimming away from it and increasing his respiration rate. The striped dolphin, however, showed no reaction to the active alarm. Based on harbour porpoise audiograms and the specific audiogram of the striped dolphin in the present study, and the low background noise levels during the experiment, both animals must have heard the alarm signals clearly. This study indicates that cetacean species are not equally sensitive to human-made noise disturbance. Therefore, source levels of acoustic alarms should be adapted to the species they are supposed to deter. In addition, alarms should be tested on each odontocete species for which they are intended to reduce bycatch.  相似文献   

2.
Harbour porpoise bycatch may be reduced by deterring porpoises from nets acoustically. In this study, two harbour porpoises were subjected to three acoustic alarms. The effect of each alarm was judged by comparing the animals' position and respiration rate during a test period with that during a baseline period. The XP-10 alarm produced 0.3 s tonal signals randomly selected from a set of 16 with fundamental frequencies between 9 and 15 kHz, with a constant pulse interval of 4.8 s (duty cycle 6%). The 2MP alarm produced 0.3 s tonal signals randomly selected from a set of 16 with similar fundamental frequencies but with random pulse intervals of between 2 and 5 s (duty cycle 8%). The frequency spectra and source levels of the 2MP and XP-10 alarms varied depending on the signal selected. The HS20-80 alarm produced a constant, but asymmetrical frequency modulated sinewave between 20 and 80 kHz with total pulse duration of 0.3 s. with random pulse intervals of between 2 and 5 s (duty cycle 4.6%). The porpoises reacted to all three alarms by swimming away from them and by increasing their respiration rate. The XP-10, which on average had the highest source level, had the strongest effect.  相似文献   

3.
The high under-water sound pressure levels (SPLs) produced during pile driving to build offshore wind turbines may affect harbor porpoises. To estimate the discomfort threshold of pile driving sounds, a porpoise in a quiet pool was exposed to playbacks (46 strikes/min) at five SPLs (6 dB steps: 130–154 dB re 1 μPa). The spectrum of the impulsive sound resembled the spectrum of pile driving sound at tens of kilometers from the pile driving location in shallow water such as that found in the North Sea. The animal's behavior during test and baseline periods was compared. At and above a received broadband SPL of 136 dB re 1 μPa [zero-peak sound pressure level: 151 dB re 1 μPa; t90: 126 ms; sound exposure level of a single strike (SELss): 127 dB re 1 μPa2 s] the porpoise's respiration rate increased in response to the pile driving sounds. At higher levels, he also jumped out of the water more often. Wild porpoises are expected to move tens of kilometers away from offshore pile driving locations; response distances will vary with context, the sounds' source level, parameters influencing sound propagation, and background noise levels.  相似文献   

4.
To prevent grounding of ships and collisions between ships in shallow coastal waters, an underwater data collection and communication network is currently under development: Acoustic Communication network for Monitoring of underwater Environment in coastal areas (ACME). Marine mammals might be affected by ACME sounds since they use sounds of similar frequencies (around 12 kHz) for communication, orientation, and prey location. If marine mammals tend to avoid the vicinity of the transmitters, they may be kept away from ecologically important areas by ACME sounds. One marine mammal species that may be affected in the North Sea is the harbour porpoise. Therefore, as part of an environmental impact assessment program, two captive harbour porpoises were subjected to four sounds, three of which may be used in the underwater acoustic data communication network. The effect of each sound was judged by comparing the animals' positions and respiration rates during a test period with those during a baseline period. Each of the four sounds could be made a deterrent by increasing the amplitude of the sound. The porpoises reacted by swimming away from the sounds and by slightly, but significantly, increasing their respiration rate. From the sound pressure level distribution in the pen, and the distribution of the animals during test sessions, discomfort sound level thresholds were determined for each sound. In combination with information on sound propagation in the areas where the communication system may be deployed, the extent of the 'discomfort zone' can be estimated for several source levels (SLs). The discomfort zone is defined as the area around a sound source that harbour porpoises are expected to avoid. Based on these results, SLs can be selected that have an acceptable effect on harbour porpoises in particular areas. The discomfort zone of a communication sound depends on the selected sound, the selected SL, and the propagation characteristics of the area in which the sound system is operational. In shallow, winding coastal water courses, with sandbanks, etc., the type of habitat in which the ACME sounds will be produced, propagation loss cannot be accurately estimated by using a simple propagation model, but should be measured on site. The SL of the communication system should be adapted to each area (taking into account bounding conditions created by narrow channels, sound propagation variability due to environmental factors, and the importance of an area to the affected species). The discomfort zone should not prevent harbour porpoises from spending sufficient time in ecologically important areas (for instance feeding areas), or routes towards these areas.  相似文献   

5.
World-wide, underwater background noise levels are increasing due to anthropogenic activities. Little is known about the effects of anthropogenic noise on marine fish, and information is needed to predict any negative effects. Behavioural startle response thresholds were determined for eight marine fish species, held in a large tank, to tones of 0.1-64 kHz. Response threshold levels varied per frequency within and between species. For sea bass, the 50% reaction threshold occurred for signals of 0.1-0.7 kHz, for thicklip mullet 0.4-0.7 kHz, for pout 0.1-0.25 kHz, for horse mackerel 0.1-2 kHz and for Atlantic herring 4 kHz. For cod, pollack and eel, no 50% reaction thresholds were reached. Reaction threshold levels increased from approximately 100 dB (re 1 microPa, rms) at 0.1 kHz to approximately 160 dB at 0.7 kHz. The 50% reaction thresholds did not run parallel to the hearing curves. This shows that fish species react very differently to sound, and that generalisations about the effects of sound on fish should be made with care. As well as on the spectrum and level of anthropogenic sounds, the reactions of fish probably depend on the context (e.g. location, temperature, physiological state, age, body size, and school size).  相似文献   

6.
江豚(Neophocaena phocaenoides G. Cuvier)俗称江猪,属鲸目(Cetacea),齿鯨亚目(Odontoceti),鼠海豚科,是海豚类中最小型的一种,也是我国沿海最常见的一种近岸小型无鰭鼠海豚。一般体长不超过2米,体重约30-80公斤,如图1照片所示。 江豚与其他海洋哺乳动物一祥,能发出多变的声信号,而且每一种声信号都受其生态行为的支配。发声系统是它们赖以生存的重要官能。海豚用其发射的声信号测定水下目标的距离、方位和大小,以至判断其形状,因而能有效的绕过障碍,避开或驱逐来犯之敌。依靠其声信号能更有效的捕获足够的食物,营养自身,抚育后代。声信号是海洋哺乳类动物在自然界进行生存斗争的有利武器。声信号又是海洋哺乳动物的语言,借以进行“社会”联络和通讯,甚至教育它们的后代。为此。人们把它们的这种功能称作“第六官能”(sixth sense)。 观察海兽类的声学行为,测试分析其声信号的结构和物理特性,是揭示它们的回声定位系统的机制,破译其“语言”奥密所必不可少的一步。从而将为驯养它们成为人类的水下得力“助手”提供可靠的实验方案,也将为仿生学等新的学科研究提供有效的理论依据。 本实验是为了把江豚驯养成“水下警犬”使其在海湾、河口进行人工放养鱼群的放牧,以及协助人类进行水下作业等目的而进行的基础工作,也是研究海洋哺乳动物回声定位的发射与接收机制的探索。实验工作是在一定的半自然条件下,对江豚某些生态行为下的声信号作了较详细的记录与分析。  相似文献   

7.
This paper presents the design of an ultralow-power acoustical receiver circuit intended to track small aquatic animals. The receiver forms a crucial component of a versatile data logger capable of sensing and storing a variety of biologically important data such as geographic position, ambient temperature, pressure, etc. The size of the final tag will be determined by the size of the cylindrical hydrophone, which will serve as housing for all electronic components, the external sensors, the timing crystal, and the battery. The receiver circuit was prototyped on a 0.5-mum complementary metal-oxide-semiconductor (CMOS) chip. Extensive lab tests proved all system component functional. The fully operational receiver consumes 21 muW at 3 V. Results from a preliminary field test, conducted with a source generating a sound pressure level of 180 dB re 1 muPa, predict a tracking range of 100-120 km  相似文献   

8.
Western Hong Kong is home to two species of marine mammals: Indo-Pacific humpbacked dolphins (Sousa chinensis) and finless porpoises (Neophocaena phocaenoides). Both are threatened in many parts of their range in southeast Asia [for example, International Biological Research Institute Reports 9 (1997), 41; Asian Marine Biology 14 (1997) 111]. In 1998, when the new Hong Kong International Airport opened in western Hong Kong, small tankers (about 100 m long, cargo capacity about 6300 metric tons) began delivering fuel to the Aviation Fuel Receiving Facility (AFRF) just off Sha Chau Island, north of the airport. Calibrated sound recordings were taken over a 4-day period from a quiet, anchored boat at distances 80-2000 m from aviation fuel delivery activities at the AFRF. From the recordings, 143 sections were selected for analysis. Narrowband spectral densities on the sound pressures were computed, and one-third octave band levels were derived for center frequencies from 10 to 16,000 Hz. Broadband levels, viz. 10-20,000 Hz. were also computed. The results showed that the Sha Chau area is normally noisy underwater, with the lowest broadband levels measured corresponding to those expected during a storm at sea (sea state 6). This background noise is believed to come largely from heavy vessel traffic in the Urmston Road to the north and east of Sha Chau and from vessels in the Pearl River Estuary to the West. The sound levels from the AFRF tankers are comparable to the levels measured from similar- and smaller-sized supply vessels supporting offshore oil exploration. The strongest sounds recorded were from a tanker leaving the AFRF at distance 100 m from the hydrophone, for which the one-third octave band level at 100 Hz was 141 dB re 1 microPa (spectrum level 127 dB re 1 microPa2/Hz) and the 10-20,000 Hz broadband level was 146 dB. At distances of 100 m or more and frequencies above 300 Hz, the one-third octave band levels were less than 130 dB (spectrum level 111 dB re 1 microPa2/Hz) and decreased with increasing frequency and distance. At distances greater than about 500 m, AFRF-associated sounds were negligible, masked by the generally high noise level of the area and attenuated by poor transmission in the very shallow water (<10 m). Because it is believed that humpbacked dolphins and finless porpoises are not very sensitive to sounds below 300 Hz, the Airport Authority Hong Kong (AA) stipulated that dedicated terminal vessels not radiate underwater sounds at spectrum levels greater than 110 dB re 1 microPa2/Hz at frequencies above 300 Hz and distances greater than 300 m. The spectrum levels at 300 Hz and higher frequencies of sounds from the tankers arriving, departing, or off-loading at AFRF were less than 110 dB re 1 microPa2/Hz even at distances of 200 m or less. The AA stipulation was met. However, it is presently unknown whether the generally strong noise levels of western Hong Kong inhibit acoustically based feeding and communication, or result in increased stress or permanent shifts in hearing thresholds.  相似文献   

9.
World-wide many cetaceans drown incidentally in fishing nets. To reduce the unwanted bycatch in gillnets, pingers (acoustic alarms) have been developed that are attached to the nets. In the European Union, pingers will be made compulsory in some areas in 2005 and in others in 2007. However, pingers may effect non-target marine fauna such as fish. Therefore in this study, the effects of seven commercially-available pingers on the behaviour of five North Sea fish species in a large tank were quantified. The species tested were: sea bass (Dicentrarchus labrax), pout (Trisopterus luscus), thicklip mullet (Chelon labrosus), herring (Clupea harengus), and cod (Gadus morhua). The fish were housed as single-species schools of 9-13 individuals in a tank. The behaviour of fish in quiet periods was compared with their behaviour during periods with active pingers. The results varied both between pingers and between fish species. Sea bass decreased their speed in response to one pinger and swam closer to the surface in response to another. Thicklip mullet swam closer to the bottom in response to two pingers and increased their swimming speed in response to one pinger. Herring swam faster in response to one pinger, and pout and cod (close relatives) showed no behavioural responses to any of the pingers. Of the seven pingers tested, four elicited responses in at least one fish species, and three elicited no responses. Whether similar responses would be elicited in these fish species in the wild, and if so, whether such responses would influence the catch rate of fisheries, cannot be derived from the results of this study. However, the results indicate the need for field studies with pingers and fish. Based on the small number of fish species tested, the present study suggests that the higher the frequency of a pinger, the less likely it is to affect the behaviour of marine fish.  相似文献   

10.
《Journal of Sea Research》1999,41(3):225-232
We investigated the occurrence of harbour porpoises in the North Sea off Schleswig-Holstein by conducting aerial surveys with emphasis on calves. Fourteen per cent of the sighted porpoises off the islands of Sylt, Amrum and southern Rømø were calves, whereas the average calf proportion for the whole North Sea as established during the 1994 SCANS survey was only 5.4%. The significantly higher proportion of calves off Sylt and Amrum indicates that these coastal waters are used as a preferred calving ground for harbour porpoises. Analysis of stranding data showed that the identified calving ground does not extend south of Amrum and that harbour porpoise calves are present off Sylt and Amrum all year round. The combination of sighting and stranding data demonstrates the special importance of the investigated area for harbour porpoises as a calving and nursing ground. The area should therefore be protected.  相似文献   

11.
This paper presents a new study of the effects on communications within the coastal harbor system of such environmental factors as nonstationary signal propagation characteristics and nonstationary atmospheric noise. Propagation of signals during daylight hours is predominantly by ground-wave propagation over sea water. During the evening hours, sky-wave and ground-wave propagation takes place. The noise at receiving sites during daylight hours is predominantly set by the level of galactic or man-made noise some 40 to 45 dB above thermal. During the evening hours, the level of atmospheric noise may at times reach some 90 dB above thermal. For daylight hours, it is shown that usable quality will not be achieved for distances greater than 400 mi; while at night, usable quality will be achieved beyond 200 mi with less than 20-percent probability. The conditional distribution of intraarea signal-to-interference ratio at the receiving antenna is shown to be approximately lognormal with a standard deviation of 23 dB during the day and a standard deviation of 16 dB during the night, for an area of high atmospheric noise. It is also shown that channel frequency separations of greater than 9 kHz are necessary if the probability of detecting crosstalk is to be kept below 25 percent during interfering transmissions from the same coverage area under low noise conditions. The probability of detecting intelligible crosstalk from a eochannel interferer transmitting at night from a different coverage area located from 400 to 1200 mi away could be as high as 58 percent.  相似文献   

12.
多频海底声学原位测试系统研制和试用   总被引：9，自引：2，他引：9  
海底沉积物的声学特性(最重要的是声速和声衰减)以及它们与物理(包括土力学)特性之间的关系是沉积物声学中两个重要的研究项目.介绍了新研制的实时监控多频海底声学原位测试系统.该系统可测量浅表层沉积物的声速.探测频率为8,10,12,15 kHz,可根据实际情况选择发射波形、接收增益和采样长度,采样率为0.5~2.0 MHz,工作水深为300 m.系统具有倾斜传感器、8通道扩充等功能.用该系统在杭州湾测得了四种频率的沉积物原位声速.  相似文献   

13.
The harbour porpoise (Phocoena phocoena) is the focus of a range of conservation efforts and policies, including the Habitats Directive, aimed at reducing the bycatch of non-target species in gillnet fisheries. This paper describes the governance process and analyses the governance mechanisms and conflicts surrounding ongoing fisheries management planning with a focus on two Natura 2000 sites in the Danish part of the Skagerrak Sea designated to protect harbour porpoises. Responsibility for developing fisheries management for Natura 2000 sites is solely the remit of the fisheries agency, including mechanisms related to stakeholder involvement. This approach fuels the efficiency of the decision making process, while full transparency and/or co-decision becomes less of a given within a ministry for an economic sector compared with the environment ministry. In relation to porpoises, conflicts are driven mainly by the economy and the varying perceptions of the bycatch issue, with great differences between government, NGO's and fishers. Interviews with fishers and fishing effort data reveal intra-sectoral conflicts pertaining to the incompatibility of active trawling and passive gillnetting in the areas. The paper questions the overall approach to managing the harbour porpoise bycatch issue in light of Natura 2000 and discusses the role of science and its high level of influence in this planning process.  相似文献   

14.
To prevent grounding of ships and collisions between ships in shallow coastal waters, an underwater data collection and communication network (ACME) using underwater sounds to encode and transmit data is currently under development. Marine mammals might be affected by ACME sounds since they may use sound of a similar frequency (around 12 kHz) for communication, orientation, and prey location. If marine mammals tend to avoid the vicinity of the acoustic transmitters, they may be kept away from ecologically important areas by ACME sounds. One marine mammal species that may be affected in the North Sea is the harbour seal (Phoca vitulina). No information is available on the effects of ACME-like sounds on harbour seals, so this study was carried out as part of an environmental impact assessment program. Nine captive harbour seals were subjected to four sound types, three of which may be used in the underwater acoustic data communication network. The effect of each sound was judged by comparing the animals' location in a pool during test periods to that during baseline periods, during which no sound was produced. Each of the four sounds could be made into a deterrent by increasing its amplitude. The seals reacted by swimming away from the sound source. The sound pressure level (SPL) at the acoustic discomfort threshold was established for each of the four sounds. The acoustic discomfort threshold is defined as the boundary between the areas that the animals generally occupied during the transmission of the sounds and the areas that they generally did not enter during transmission. The SPLs at the acoustic discomfort thresholds were similar for each of the sounds (107 dB re 1 microPa). Based on this discomfort threshold SPL, discomfort zones at sea for several source levels (130-180 dB re 1 microPa) of the sounds were calculated, using a guideline sound propagation model for shallow water. The discomfort zone is defined as the area around a sound source that harbour seals are expected to avoid. The definition of the discomfort zone is based on behavioural discomfort, and does not necessarily coincide with the physical discomfort zone. Based on these results, source levels can be selected that have an acceptable effect on harbour seals in particular areas. The discomfort zone of a communication sound depends on the sound, the source level, and the propagation characteristics of the area in which the sound system is operational. The source level of the communication system should be adapted to each area (taking into account the width of a sea arm, the local sound propagation, and the importance of an area to the affected species). The discomfort zone should not coincide with ecologically important areas (for instance resting, breeding, suckling, and feeding areas), or routes between these areas.  相似文献   

15.
Harbour porpoises Phocoena phocoena are protected under the Habitats and Species Directive (92/43/EEC) and listed as a priority species in the City and County of Swansea's Biodiversity Action Plan (BAP). Increased coastal pressures demand better governance and this study adopted a dimensional analysis to produce a local management framework for harbour porpoise populations. Having established basic behavioural dynamics and identified critical habitats, a coastal zone use model was developed. This highlighted porpoise and coastal user interaction from a species perspective. Evidence was determined from observations and published research, and an Environmental Risk Assessment (ERA) was undertaken. An estimation of consequence probability was determined and revealed that continued coastal use, without mitigation, is likely to have significant local impacts on porpoise populations. A strengths, weaknesses, opportunities and threats (SWOT) analysis and legislative appraisal highlighted potential opportunities and deficiencies. Mitigation refers principally to industry, fisheries and recreation and suggestions include flexible zoning; speed and vessel restrictions; engineering solutions to noise intrusion and fisheries monitoring. A mixture of formal and informal regulations is recommended, together with educational projects and industry-funded research opportunities.  相似文献   

16.
Underwater noise due to snapping shrimp is highly impulsive, and often dominates the ambient noise environment of warm, shallow waters at frequencies above 1 kHz. We report here on the statistics of bandpass snapping shrimp noise data, and on the modeling of the joint distribution of the in-phase and quadrature components using bivariate versions of the generalized Gaussian (GG), generalized Cauchy, and Gaussian-Gaussian mixture models. We evaluate the performance of several generalized energy detectors for passive bandpass detection, by inserting stochastic signals into the noise data. Detection thresholds were measured for an integration time of 0.5 s and false alarm probabilities down to 1%. The locally optimum detector based on the mixture model gave the best weak signal detection performance, with an 8 dB reduction in detection threshold over conventional energy detection. A significance test detector based on the GG model performed 1-2 dB worse, but exhibited better strong signal performance  相似文献   

17.
The underwater acoustic noise of five representative whale-watching boats used in the waters of west Maui was measured in order to study the effects of boat noise on humpback whales. The first set of measurements were performed on 9 and 10 March, close to the peak of the whale season. The ambient noise was relatively high with the major contribution from many chorusing humpback whales. Measurements of boat sounds were contaminated by this high ambient background noise. A second set of measurements was performed on 28 and 29 April, towards the end of the humpback whale season. In both sets of measurements, two of the boats were inflatables with outboard engines, two were larger coastal boats with twin inboard diesel engines and the fifth was a small water plane area twin hull (SWATH) ship with inter-island cruise capabilities. The inflatable boats with outboard engines produced very complex sounds with many bands of tonal-like components. The boats with inboard engines produced less intense sounds with fewer tonal bands. One-third octave band measurements of ambient noise measured on 9 March indicated a maximum sound pressure level of about 123 dB re 1 microPa at 315 Hz. The maximum sound pressure level of 127 dB at 315 Hz was measured for the SWATH ship. One of the boats with outboard engines produced sounds between 2 and 4 kHz that were about 8-10 dB greater than the level of background humpback whale sounds at the peak of the whale season. We concluded that it is unlikely that the levels of sounds produced by the boats in our study would have any grave effects on the auditory system of humpback whales.  相似文献   

18.
Backscattering measurements were performed in shallow water on sand, gravel, and clay bottoms. The equipment included a parametric array that emitted pulses of differential frequencies (8 to 40 kHz) with a 3° directivity. The ranges did not exceed 50 m. The grazing angles varied from 4° to 90°. The bottom backscattering strength does not depend on the emitted pulse type (frequency and length). If one fits a Lambert law to the variations of the backscattering strength versus the grazing angle, the value at the origin fluctuates between-15 and-22 dB without any clear effect from the different bottom types. Statistical tests show that under the experimental measurement conditions: (1) the alternative received signal does not generally follow a normal distribution; (2) among five classical distributions in sonar and radar that have been fitted to the detected-integrated signal (exponential, Weibull, chi-2, log-normal, Rice), the best-fitted law is the log-normal; (3) signals backscattered by separated areas of the same bottom can hardly be regarded as stationary and, even less, homogeneous; and (4) with an anisotropic bottom topography the statistical properties depend on the aspect under which this topography is seen  相似文献   

19.
Using the phenomenon of the partial reflection of acoustic waves from anisotropic wind-velocity and temperature inhomogeneities in the lower troposphere is justified in determining the structure of these inhomogeneities. The data (obtained with the method of bistatic acoustic sounding) on signals reflected from stratified inhomogeneities in the lower 600-m layer of the troposphere are given. A detonation-type pulsed acoustic source was used. The methods of isolating a small (in amplitude) reflected signal against the background of noise and determining the reflecting-layer height and the partial-reflection coefficient from the measured parameters (time delay and amplitude) of a reflected signal are presented. The method of estimating the vertical gradients of the effective sound speed and the squared acoustic refractive index from the partial-reflection coefficient previously calculated is described on the basis of an Epstein transition-layer model. The indicated parameters are experimentally estimated for concrete cases of recording reflected signals. A comparison of our estimates with independent analogous data simultaneously obtained for the same parameters with monitoring instruments (a sodar and a temperature profiler) has yielded satisfactory results.  相似文献   

20.
The Ieodo Ocean Research Station(IORS) is an integrated meteorological and oceanographic observation base which was constructed on the Ieodo underwater rock located at a distance of about 150 km to the south-west of the Mara-do, the southernmost island in Korea. The underwater ambient noise level observed at the IORS was similar to the results of the shallow water surrounding the Korean Peninsula (Choi et al. 2003) and was higher than that of deep ocean (Wenz 1962). The wind dependence of ambient noise was dominant at frequencies of a few kHz. The surface current dependence of ambient noise showed good correlation with the ambient noise in the frequency of 10 kHz. Especially, the shrimp sound was estimated through investigations of waveform and spectrum and its main acoustic energy was about 40 dB larger than ambient noise level at 5 kHz.  相似文献   

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