Available at: https://doi.org/10.1016/0959-8030(91)90019-G
Stress in fish caused by physical disturbances encountered in aquaculture, such as handling and transport, evokes a variety of responses that may be adaptive or maladaptive. The overall effect of stress may be considered as a change in biological condition beyond the normal resting state that challenges homeostasis and, thus, presents a threat to the fish’s health. These stress-induced changes are grouped as primary; secondary, which includes metabolic, hematological, hydromineral, and structural; and tertiary or ‘whole animal’ responses. Many of these responses can be used as quantitative indicators of stress although investigators need to be aware of the various ‘nonstress’ factors that can also influence these conditions. A major focus of current research is on the response of the hypothalamic-pituitary-interrenal axis and the resultant elevation of circulating corticosteroids. Stress, through the action of corticosteroids, may (a) reduce immunocompetence by influencing lymphocyte numbers and antibody-production capacity, and (b) affect reproduction by altering levels and patterns of reproductive hormones that influence maturation. Stress may also alter metabolic scope in fish and affect growth, partly as a result of the catabolic or gluconeogenic effect of corticosteroids. Although certain stressors encountered during normal aquacultural procedures may be unavoidable, a number of practical approaches are suggested that would help to alleviate the detrimental effects of stress in fish.
Available at: http://doi.wiley.com/10.1111/j.1748-7692.2002.tb01076.x
We conducted a double blind experiment in an artisanal gillnet fishery in Argentina to determine the effectiveness of acoustic deterrents (pingers) at reducing bycatch of the Franciscana dolphin (Pontoporia blainvillei). The fishery was conducted by small inflatable and fiberglass vessels operating between 0.5 and 7 km from the coast. Each vessel carried an independent observer who was rotated from vessel to vessel throughout the course of the experiment. Information on the number of dolphins captured, geographic position, depth, configuration of fishing gear, soak time, biomass of fish caught, and sea lion predation in a string/net producing any damage was recorded. Equivalent numbers of active and silent pingers were used during the experiment. A total of 45 dolphins were caught in the silent nets, and seven were caught in the active pinger nets, demonstrating a highly significant reduction in bycatch for this species. However, sea-lions (Otarza javescens) damaged the fish in active pinger nets significantly more than silent nets, and the damage increased over the course of the experiment. Although pingers show promise as a management tool for this species, pinniped depredation suggests that higher pinger frequencies will be needed to avoid a “dinner bell” effect.
Available at: http://asa.scitation.org/doi/10.1121/1.2139067
Dividing the acoustic repertoires of animals into biologically relevant categories presents a widespread problem in the study of animal sound communication, essential to any comparison of repertoires between contexts, individuals, populations, or species. Automated procedures allow rapid, repeatable, and objective categorization, but often perform poorly at detecting biologically meaningful sound classes. Arguably this is because many automated methods fail to address the nonlinearities of animal sound perception. We present a new method of categorization that incorporates dynamic time-warping and an adaptive resonance theory (ART) neural network. This method was tested on 104 randomly chosen whistle contours from four captive bottlenose dolphins (Tursiops truncatus), as well as 50 frequency contours extracted from calls of transient killer whales (Orcinus orca). The dolphin data included known biologically meaningful categories in the form of 42 stereotyped whistles produced when each individual was isolated from its group. The automated procedure correctly grouped all but two stereotyped whistles into separate categories, thus performing as well as human observers. The categorization of killer whale calls largely corresponded to visual and aural categorizations by other researchers. These results suggest that this methodology provides a repeatable and objective means of dividing bioacoustic signals into biologically meaningful categories.
Despite numerous relevant international, European and national legislative and political obligations, meaningful and effective conservation measures for the harbour porpoise (Phocoena phocoena) remain tenuous. Based on existing evidence, additional management options, beyond existing measures, are required for harbour porpoise to alleviate the existing and unprecedented scale of pressures they face. As our seas become busier, the pressures faced by harbour porpoises will intensify. Existing pressures are broad-ranging and vary from acute and often fatal consequences, such as bycatch and collision risk (from maritime traffic or underwater turbines), to chronic and/or cumulative impacts, for example through limiting feeding opportunity and displacement from preferred habitats. Current management measures undoubtedly provide some safeguards to these pressures. However, they fall short of delivering a meaningful, consistent and adaptive long-term conservation plan that covers the range of sensitivities and coherently brings together the threats from cumulative activities. The review of harbour porpoise management options in this report, combined with the assessment to identify geographically discrete Areas of Concern (AoC) provides a useful insight into the current gaps, challenges and spatial scope of issues. The role of the AoC is to identify the range of pressures relevant to the Area to allow for management options to be tailored where pressure is highest, moving towards a best practice approach. A number of recommendations are put forward for each sector and for each of the case study AoCs to illustrate potential areas for further discussion, research and delivery. Recommendations can be generic or cover issues pertinent to a number of sectors and they can be relevant at a national level or specific to a sector or geographic location. This report builds on previous work by WDC to promote harbour porpoise conservation in the UK, focusing on requirements of the EU Habitats Directive, for site designation of Special Areas of Conservation (SACs) and strict protection throughout their range. The overarching aim of this report is to produce Management Options to effectively protect harbour porpoises, including in possible SACs designated to protect harbour porpoises. Towards this aim, we provide an assessment of the effectiveness of the range of management strategies, as well as sectoral and spatial measures that are pertinent to the conservation of harbour porpoise. WDC have overlaid the suspected highly sensitive harbour porpoise hotspots against the spatial distribution and cumulative overlap of human activities. By focusing this assessment within these identified harbour porpoise AoCs, the aim is to target conservation effort and resources for delivery in areas where they can be considered most effective. This document is two-tiered to reflect (i) management protocols that are relevant and apply at a UK wide level (taking into account devolved responsibilities) and (ii) measures that are area specific and reflect regional and local measures and players. In addition, the report provides UK wide and, where appropriate, region-specific recommendations on future direction and priorities. The AoC introduced in this report complement the WDC work on critical habitat for harbour porpoise (Clark et al., 2010; Dolman et al., 2013). The two concepts are complementary in the delivery of international and national harbour porpoise conservation goals, including designating SACs to protect harbour porpoises. AoC represent the components of critical habitat that are assessed to be under the greatest pressure from human activities, and therefore, will require the greatest and more urgent need for action in management measures. Baseline surveys and continuing monitoring surveillance, alongside the development of broad-scale management measures, rather than piecemeal and largely untested mitigation measures, must be seen as an integral and essential part of harbour porpoise conservation.
Four groups of pressures were chosen for further assessment that are relevant to harbour porpoises
within the UK EEZ:
Barriers to Movement e.g. barriers to species movement (including physical and sound barriers).
-Physical Trauma e.g. damage caused to porpoises from collision or noise, which may either directly result in mortality or significant physical harm leading to mortality.
-Disturbance e.g. from physical and acoustic sources which impact or alter porpoise habitat and or behaviour such as resting, feeding, breeding and socialising.
-Ecosystem Effects e.g. sufficient alteration of habitat that may interrupt or displace necessary ecosystem systems of critical importance such as prey or prey habitat.
The sensitivity information presents our general understanding of relationships between porpoises and the effects associated with certain activities. It does not take full account of the frequency or intensity of all activities which occur within the area of assessment and will form an important part of future discussions with stakeholders.
Available at: http://asa.scitation.org/doi/abs/10.1121/1.415087
The freshwater bivalve mollusk, Dreissena polymorpha – better known as the Zebra Mussel, since its introduction into the Great Lakes in 1985 has been quickly spreading throughout the waterways of both the United States and Canada causing serious economic and environmental consequences. The present study has been directed toward developing acoustic techniques to control Zebra Mussel infestation in various water intake and storage facilities.
The effects of ultrasonic and hydrodynamic cavitation, low‐frequency sound and vibration on various life stage mussels (from eggs and larvae to adults) have been studied. It was found that cavitation can be used as a control measure for Zebra Mussel veligers. The efficiency of the ultrasonic and hydrodynamic cavitation treatments were measured as an output energy rate to achieve 100% mortality. Laboratory experiments demonstrated the effective use of low‐frequency waterborne sound to prevent Zebra Mussels from settling and translocating and to reduce reproduction abilities of mussels. [This work has been supported by Grant No. NA26RG0403‐01 from the NOAA to the Stevens Institute of Technology, New Jersey Sea Grant College Program.]
Available at: https://doi.org/10.1016/j.icesjms.2006.06.015
Acoustic harassment devices (AHDs) were deployed at salmon-trap nets in the Baltic Sea to reduce gear and catch damage by grey seals ( Halichoerus grypus ). The AHDs emitted pulses of 250–500-ms duration, worked at a frequency of 15 kHz, and a source level of 179 dB re 1 μPa rms at 1 m. AHDs were deployed during three consecutive fishing seasons. Catches were significantly higher in traps with AHDs (25.5 kg d −1 ) than in controls (12.0 kg d −1 ), and catch damage was less (3.5 vs. 6.7 kg d −1 ). These results persisted over and between fishing seasons, but late in the season damage to the catches was common also in traps with AHDs. This study shows that the AHD may be a complementary mitigation tool in the seal–fishery conflict in certain types of fisheries, even though it is technically demanding, and for environmental reasons should be used with great care.
Available at: https://jeb.biologists.org/content/213/9/1536
Aversiveness of sounds and its underlying physiological mechanisms in mammals are poorly understood. In this study we tested the influence of psychophysical parameters, motivation and learning processes on the aversiveness of anthropogenic underwater noise in phocid seals (Halichoerus grypus and Phoca vitulina). We compared behavioural responses of seals to playbacks of sounds based on a model of sensory unpleasantness for humans, sounds from acoustic deterrent devices and sounds with assumed neutral properties in different contexts of food motivation. In a captive experiment with food presentation, seals habituated quickly to all sound types presented at normalised received levels of 146dB re. 1mPa (r.m.s., root mean square). However, the fast habituation of avoidance behaviour was also accompanied by a weak sensitisation process affecting dive times and place preference in the pool. Experiments in the wild testing animals without food presentation revealed differential responses of seals to different sound types. We observed avoidance behaviour at received levels of 135–144dB re. 1mPa (sensation levels of 59–79dB). In this experiment, sounds maximised for ‘roughness’ perceived as unpleasant by humans also caused the strongest avoidance responses in seals, suggesting that sensory pleasantness may be the result of auditory processing that is not restricted to humans. Our results highlight the importance of considering the effects of acoustic parameters other than the received level as well as animal motivation and previous experience when assessing the impacts of anthropogenic noise on animals.
Relevant Quote: We present evidence that repeated elicitation of the acoustic startle reflex leads to rapid and pronounced sensitisation of sustained spatial avoidance behaviour in grey seals (Halichoerus grypus). Animals developed rapid flight responses, left the exposure pool and showed clear signs of fear conditioning. Once sensitised, seals even avoided a known food source that was close to the sound source. In contrast, animals exposed to non-startling (long rise time) stimuli of the same maximum sound pressure habituated and flight responses waned or were absent from the beginning. The startle threshold of grey seals expressed in units of sensation levels was comparable to thresholds reported for other mammals (93 dB).
Conclusions: Our results demonstrate that the acoustic startle reflex plays a crucial role in mediating flight responses and strongly influences the motivational state of an animal beyond a short-term muscular response by mediating long-term avoidance. The reflex is therefore not only a measure of emotional state but also influences emotional processing. The biological function of the startle reflex is most likely associated with mediating rapid flight responses. The data indicate that repeated startling by anthropogenic noise sources might have severe effects on long-term behaviour. Future, studies are needed to investigate whether such effects can be associated with reduced individual fitness or even longevity of individuals.
Available at: http://www.int-res.com/abstracts/meps/v492/p285-302/
Relevant Quote: “Acoustic deterrent devices (ADDs) to prevent pinniped predation on fish farms and fisheries are widely used, but show highly varying success…We review the available literature on the efficiency of commercial ADDs, evaluate the unintended impact on behaviour, communication and hearing of marine life, and suggest solutions based on psycho-physiological predictions.”
Abstract: Acoustic deterrent devices (ADDs) to prevent pinniped predation on fish farms and fisheries are widely used, but show highly varying success. Recently, ADDs have also been highlighted as a conservation concern due to their adverse impact on toothed whales. We review the available literature on the efficiency of commercial ADDs, evaluate the unintended impact on behaviour, communication and hearing of marine life, and suggest solutions based on psycho-physiological predictions. The main problems associated with ADDs are a lack of long-term efficiency, introduction of substantial noise pollution to the marine environment and long-term effects on target and non-target species. Odontocetes have more sensitive hearing than pinnipeds at the frequencies where most ADDs operate, which may explain the reported large-scale habitat exclusion of odontocetes when ADDs are used. Furthermore, long-term exposure to ADDs may damage the hearing of marine mammals. Fish and invertebrates have less sensitive hearing than marine mammals and fewer efforts have been made to quantify the effects of noise on these taxa. Solutions can be found by decreasing sound exposure, exploiting neuronal reflex arcs associated with flight behaviour and making use of differences in species’ hearing abilities to increase target specificity. To minimise adverse effects, environmental impact assessments should be carried out before deploying ADDs and only effective and target-specific devices should be used.
Relevant Quote: “Our data demonstrate that the startle method can be used to selectively deter seals without affecting porpoises.”
Acoustic deterrent devices (ADDs) have often been considered a benign solution to managing pinniped predation. However, ADDs have also been highlighted as a conservation concern since they can inﬂict large-scale habitat exclusion in toothed whales (odontocetes). We tested a new method that selectively inﬂicted startle responses in harbour seals (Phoca vitulina) at close ranges to the loudspeaker but not in a non-target species, the harbour porpoise (Phocoena phocoena), by using a frequency range where porpoise hearing was less sensitive than that of phocid seals. The sound exposure consisted of isolated 200 ms long, 2–3 octave-band noise pulses with a peak frequency of 1 kHz, which were presented at a source level of∼180 dB re 1Pa. Field tests were carried out within a 2-month period on a ﬁsh farm on the west coast of Scotland where marine mammal behaviour was observed within three distance categories. Seal numbers dropped sharply during sound exposure compared with control observation periods within 250 m of the sound source but were unaffected at distances further away from the farm. A Poisson regression model revealed that the number of seal tracks within 250 m of the device decreased by∼91% during sound exposure and was primarily inﬂuenced by sound exposure with no evidence for a change in the effect of treatment such as habituation, throughout the experiment. In contrast to seals, there was no shift in the number of porpoise groups in each distance category as a result of sound exposure and porpoises were regularly seen close to the device. We also sighted six common minke whales during sound exposure while only one was seen during control periods. Our data demonstrate that the startle method can be used to selectively deter seals without affecting porpoises.
Available at: http://doi.wiley.com/10.1111/acv.12248
Carnivore depredation on human livestock is a worldwide problem with few viable solutions. Non-lethal management tools such as acoustic devices show highly varying success and often pose a conservation risk due to noise pollution and habitat degradation. We tested the long-term effectiveness of a deterrence system which harnesses an autonomous reflex (startle) to selectively inflict avoidance responses in a target species (phocidseals) by emitting band-limited noise pulses with sharp onset times. Seal predation was monitored at a marine salmon farm (test site) over a full production cycle (19 month) with a multi-transducer deterrent system deployed for the final year. Predation was also monitored for several months at two control sites and additional short-term tests were carried out at sites which suffered higher predation rates. Generalized linear (mixed) models revealed that sound exposure caused a 91% reduction in lost fish when comparing predation levels within the test site and 97% when comparing the test site against both control sites. Similarly, sound exposure led to a 93% reduction in the number of fish lost due to seal damage at a short-term test site. Visual monitoring of marine mammals around the long-term test site showed that the number of seal surfacings within 100 m from the loudspeakers was only slightly lower during sound exposure. Harbour porpoise and otter distribution around the farm was not affected by sound exposure. By adjusting the frequency composition of startle stimuli, our method has the potential to provide solutions for managing human–wildlife conflicts in terrestrial and marine habitats by selectively deterring target species.
Relevant Quote: “We compared behavioural responses of seals to playbacks of sounds based on a model of sensory unpleasantness for humans, sounds from acoustic deterrent devices and sounds with assumed neutral properties in different contexts of food motivation. In a captive experiment with food presentation, seals habituated quickly to all sound types…
Our results highlight the importance of considering the effects of acoustic parameters other than the received level as well as animal motivation and previous experience when assessing the impacts of anthropogenic noise on animals.”
Abstract: Understanding what psycho-physiological and behavioural factors influence aversiveness of sound in marine mammals is important for conservation and practical applications. The aim of this study was to determine predictors for impact of anthropogenic noise and to develop a target-specific predator deterrence system for use on fish farms.
Three classes of stimuli were tested:
1) grey seal underwater communication calls expected to be used in territorial defence,
2) high duty-cycle moderately loud artificial sounds (some of which were based on models of unpleasantness for humans),
3) brief, intense pulses designed to elicit the acoustic startle reflex.
Communication calls had no deterrence effect but instead caused attraction responses. Tests with high duty-cycle artificial sounds showed that food-motivated animals habituate quickly, although sound exposure caused subtle changes in diving patterns over a longer time. Field trials using the same stimuli were used to determine avoidance…
Relevant Quote: “…we carried out behavioral response tests with grey seals to two sonar systems (200 and 375 kHz systems). Results showed that both systems had significant effects on the seals behavior; when the 200 kHz sonar was active, seals spent significantly more time hauled out and, although seals remained swimming during operation of the 375 kHz sonar, they were distributed further from the sonar. The results show that although peak sonar frequencies may be above marine mammal hearing ranges, high levels of sound can be produced within their hearing ranges that elicit behavioral responses; this has clear implications for the widespread use of sonar in the marine environment.”
The use of high frequency sonar is now commonplace in the marine environment. Most marine mammals rely on sound to navigate, and for detecting prey, and there is the potential that the acoustic signals of sonar could cause behavioral responses. To investigate this, we carried out behavioral response tests with grey seals to two sonar systems (200 and 375 kHz systems). Results showed that both systems had significant effects on the seals’ behavior; when the 200 kHz sonar was active, seals spent significantly more time hauled out and, although seals remained swimming during operation of the 375 kHz sonar, they were distributed further from the sonar. The results show that although peak sonar frequencies may be above marine mammal hearing ranges, high levels of sound can be produced within their hearing ranges that elicit behavioral responses; this has clear implications for the widespread use of sonar in the marine environment.
Available at: http://ebooks.cambridge.org/ref/id/CBO9780511610363A030
Relevant Quote: Communication in networks has received considerable research attention over the last few years (Naguib & Todt, 1997; Otter et al., 1999; Peake et al., 2001; Mennill et al., 2002; Ch. 1). This is true for two types of network interaction, one in which several receivers react to the signal of just one individual and a more complex one in which receivers eavesdrop on the signal exchange of two or more individuals and use the information they gained in their own decision making (McGregor & Dabelsteen, 1996; Ch. 2). If we think about communication, the fact that there often is more than just one individual receiving any given signal is not surprising. One reason that many studies on more transient signals concentrated on only one signaller and one receiver was a methodological problem. It is notoriously difficult to sample behaviour from more than one or two individuals at a time, especially if interactions are rapid and involve movements of individuals. Recently, the simultaneous tracking of several individuals in a large group has become feasible. This has led to an increase in studies investigating the effects of signals on several receivers in rapid communication interactions. Many such studies have concentrated on the acoustic domain, a modality that is inherently transient. Signals rarely last more than a few seconds and usually provide a variety of different messages within a single signal.
While there is ample evidence from terrestrial environments that more than one individual can receive and use information from a call or a calling interaction, data on acoustic communication networks in marine environments are sparse.
Available at: http://www.int-res.com/articles/dao/14/d014p195.pdf
Relevant Quote:The effects of hydrocortisol implants on the susceptibility of naive coho salmon Oncorhynchus kisutch to infection with the economically important marine ectoparasitlc copepod Lepeophtheirus salmonis was investigated under laboratory conditions. Cortisol-implanted coho salmon were more susceptible to infection than the control coho salmon. Copepods were lost from the gills of the control coho salmon by 10 d post-infection, and only a few remained on the body and fins at 20 d post-infection. Copepods were retained on the gills, fins and body of the cortisol-implanted coho salmon over the 20 d studied. Histological sections of control coho gills and fins revealed well developed epithelial hyperplasias and inflammatory responses to the presence of L. salmonis. The magnitude of the inflammatory response and the development of epithelial hyperplasia was suppressed in the cortisol-implanted coho. These data support the hypothesis that non-specific host defence mechanisms are important in resistance of coho salmon to infection with L. salmonis.
Relevant Quote: Cavitation generated by DYNAJET® cavitating jets can greatly enhance various chemical reactions, oxidize aqueous compounds, and disrupt microorganisms. Controlled laboratory experiments have established the ability of these jets to destroy microorganisms and oxidize a broad range of compounds including pesticides, Volatile Organic Compounds, arsenic, and reduce TOC (Total Organic Carbon).
Experiments were conducted using a variety of cavitating jet configurations and operating conditions. Histories of the contaminant concentration reductions and destruction of selected bacteria strains were obtained from periodic sampling. Multiple order of magnitude reduction in e. coli concentration has been demonstrated. Comparisons with ultrasonic experiments show that jet-induced cavitation can achieve oxidation with up to two orders of magnitude greater energy efficiency.
Available at: http://www.doi.org/10.1073/pnas.1304459110
Relevant Quote: “Labeling with learned signals is a foundation of human language but is notably rare in nonhuman communication systems…. Bottlenose dolphins develop their own unique identity signal, the signature whistle. This whistle encodes individual identity independently of voice features. The copying of signature whistles may therefore allow animals to label or address one another. Here, we show that wild bottlenose dolphins respond to hearing a copy of their own signature whistle by calling back. Animals did not respond to whistles that were not their own signature. This study provides compelling evidence that a dolphin’s learned identity signal is used as a [name]”.
In animal communication research, vocal labeling refers to incidents in which an animal consistently uses a specific acoustic signal when presented with a specific object or class of objects. Labeling with learned signals is a foundation of human language but is notably rare in nonhuman communication systems. In natural animal systems, labeling often occurs with signals that are not influenced by learning, such as in alarm and food calling. There is a suggestion, however, that some species use learned signals to label conspecific individuals in their own communication system when mimicking individually distinctive calls. Bottlenose dolphins (Tursiops truncatus) are a promising animal for exploration in this area because they are capable of vocal production learning and can learn to use arbitrary signals to report the presence or absence of objects. Bottlenose dolphins develop their own unique identity signal, the signature whistle. This whistle encodes individual identity independently of voice features. The copying of signature whistles may therefore allow animals to label or address one another. Here, we show that wild bottlenose dolphins respond to hearing a copy of their own signature whistle by calling back. Animals did not respond to whistles that were not their own signature. This study provides compelling evidence that a dolphin’s learned identity signal is used as a label when addressing conspecifics. Bottlenose dolphins therefore appear to be unique as nonhuman mammals to use learned signals as individually specific labels for different social companions in their own natural communication system.
The effectiveness of ultrasound action on the disinfection processes of natural water and sewage, as well as the kinetic regularities of these processes have been shown. Disinfection processes of the investigated waters under ultrasonic cavitation and gas bubbling correspond to the kinetic regularities that are described by the reaction equations of the first order regardless of the different origins of polluted waters, different initial number of microorganisms and their different types. In the given work the natural water disinfection is the combination of the processes containing deaggregation and cells destruction. The highest efficiency of the sewage disinfection has been determined under the simultaneous action of argon and ultrasound.
Available at: http://jeb.biologists.org/cgi/doi/10.1242/jeb.120535
Combinations of stressors occur regularly throughout an animal’s life, especially in agriculture and aquaculture settings. If an animal fails to acclimate to these stressors, stress becomes chronic, and a condition of allostatic overload arises with negative results for animal welfare. In the current study, we describe effects of exposing Atlantic salmon parr to an unpredictable chronic stressor (UCS) paradigm for 3 weeks. The paradigm involves exposure of fish to seven unpredictable stressors three times a day. At the end of the trial, experimental and control fish were challenged with yet another novel stressor and sampled before and 1 h after that challenge. Plasma cortisol decreased steadily over time in stressed fish, indicative of exhaustion of the endocrine stress axis. This was confirmed by a lower cortisol response to the novel stressor at the end of the stress period in chronically stressed fish compared with the control group. In the preoptic area (POA) and pituitary gland, chronic stress resulted in decreased gene expression of 11βhsd2, gr1 and gr2 in the POA and increased expression of those genes in the pituitary gland. POA crf expression and pituitary expression of pomcs and mr increased, whereas interrenal gene expression was unaffected. Exposure to the novel stressor had no effect on POA and interrenal gene expression. In the pituitary, crfr1, pomcs, 11βhsd2, grs and mr were down-regulated. In summary, our results provide a novel overview of the dynamic changes that occur at every level of the hypothalamic-pituitary gland–interrenal gland (HPI) axis as a result of chronic stress in Atlantic salmon.
Atlantic salmon (Salmo salar) parr were subjected to acute handling stresses and growth-monitored for at least 30 days. In fish stressed twice daily, growth rate in weight was 61% lower than controls after 11 days (1.00 vs. 2.57% day-1) and over a 30 day period it was 50% lower than controls (1.53 vs. 3.07% day-1). In fish stressed once daily, growth rate was 18% lower than controls after 10 days (2.17 vs. 2.63% day-1) and over a 30-day period it was 34% lower than controls (1.71 vs. 2.59% day-1). In fish stressed once daily, food consumption was reduced by 62% and 37% after 17 and 37 days, respectively. At the end of 40 days of acute stress once daily, control and stressed fish were sampled 1 h prior to, 3 and 7 h after a stress event. Plasma growth hormone levels were significantly higher in the stressed group than in the controls prior to and 7 h after stress. Plasma insulin-like growth factor I (IGF-I) levels were higher in the stressed group only 3 and 7 h after stress. Plasma cortisol levels were lower in the stressed group prior to and 3 h after stress. The results indicate that acute stressors decrease growth of Atlantic salmon parr, with increasing frequency of stress having a more rapid and greater effect.
Available at: https://doi.org/10.1098/rsos.170286
Acoustic harassment devices (AHD) or ‘seal scarers’ are used extensively, not only to deter seals from fisheries, but also as mitigation tools to deter marine mammals from potentially harmful sound sources, such as offshore pile driving. To test the effectiveness of AHDs, we conducted two studies with similar experimental set-ups on two key species: harbour porpoises and harbour seals. We exposed animals to 500 ms tone bursts at 12 kHz simulating that of an AHD (Lofitech), but with reduced output levels (source peak-to-peak level of 165 dB re 1 µPa). Animals were localized with a theodolite before, during and after sound exposures. In total, 12 sound exposures were conducted to porpoises and 13 exposures to seals. Porpoises were found to exhibit avoidance reactions out to ranges of 525m from the sound source. Contrary to this, seal observations increased during sound exposure within 100m of the loudspeaker. We thereby demonstrate that porpoises and seals respond very differently to AHD sounds. This has important implications for application of AHDs in multi-species habitats, as sound levels required to deter less sensitive species (seals) can lead to excessive and unwanted large deterrence ranges on more sensitive species (porpoises).
Summary: In accordance with the Marine Mammal Protection Act (MMPA), the Gulf of Maine Aquaculture-Pinniped Interaction Task Force (Task Force) was established to advise NMFS of issues and problems regarding pinnipeds interacting in a dangerous or damaging manner with aquaculture resources in the Gulf of Maine….
The salmon aquaculture industry in the northeastern United States has grown substantially in the last decade, as have regional populations of harbor seals (Phoca vitulina) and gray seals (Halichoerus grypus). The industry claims that losses caused by seals attacking the salmon pens are substantial and that the frequency of attacks has increased in recent years. Seals are protected under the MMPA, and the actions that salmon growers can take to protect their pens from seals are limited to non-lethal deterrence measures by the MMPA….
The Task Force recommended against lethal deterrence measures. In general, NMFS expects to concur with that recommendation…
Section 101(a)(4) of the MMPA authorizes the deterrence of marine mammals to prevent damage to private and public property, including fishing gear and catch, so long as deterrence measures do not result in the death or serious injury of marine mammals. Minor injury that may result from deterrence measures would not require rehabilitation.
…NMFS acknowledges the need for creative approaches to mitigate pinniped damage at fish farms.
Available at: https://doi.org/10.1006/jmsc.2001.1136
Whale displacement by acoustic “pollution” has been diﬃcult to document, even in cases where it is strongly suspected, because noise eﬀects can rarely be separated from other stimuli. Two independent studies on the natural history of killer whales (Orcinus orca) monitored frequency of whale occurrence from January 1985 through December 2000 in two adjacent areas: Johnstone Strait and the Broughton Archipelago. Four high-amplitude, acoustic harassment devices (AHDs) were installed throughout 1993 on already existing salmon farms in the Broughton Archipelago, in attempts to deter predation on ﬁsh pens by harbour seals (Phoca vitulina Linnaeus). While whale occurrence was relatively stable in both areas until 1993, it then increased slightly in the Johnstone Strait area and declined signiﬁcantly in the Broughton Archipelago while AHDs were in use. Both mammal-eating and ﬁsh-eating killer whales were similarly impacted. Acoustic harassment ended in the Broughton Archipelago in May 1999 and whale occurrence re-established to baseline levels. This study concludes that whale displacement resulted from the deliberate introduction of noise into their environment.
Available at: https://doi.org/10.1016/S0044-8486(99)00300-2
This paper reviews current aquatic farm production in the USA and estimates an annual financial exposure of US$350 million in the marine and coastal environments made up of sales, standing crop value and capital investment. In addition, nationwide aquatic farming creates almost 200,000 jobs and, with secondary and downstream activities combined, contributes about US$5600 million to the GNP. The paper then reviews the increasing risk that elements of the coastal aquaculture industry in the Pacific Northwest face from interactions with populations of marine mammals. These are particularly California sea lions and seals, which have greatly increased in the last 20 years from California to British Columbia.
(i) shellfish from traditional beds have been contaminated by fecal coliforms from seals and made unfit for human consumption, and have been experiencing increasing losses to river otters and sea otters;
(ii) culture-based salmon fisheries, including endangered salmon stocks, have been exposed to heavy predation by sea lions and seals, resulting in both direct losses and reduced market value of wounded survivors;
(iii) net-pen farms have been exposed to the same heavy losses from predatory sea lions and seals attacking fish in the pens, together with added financial burdens for anti-predator nets, increased maintenance and labor; and
(iv) workers in aquaculture and fisheries, and other waterborne industries, have been observing less fear of humans by sea lions and seals, and more direct damage to servicing facilities.
The four issues are discussed both technically and economically, and a number of solutions proposed for managing and controlling these increasing risks.
Available at: https://doi.org/10.1006/jmsc.2001.1136
Relevant Quote: The system we described has many advantages for the application of behavioral studies using focal follows. It consists of affordable hydrophone elements and is easy to install in any small boat. The localization program allows visual selection of the best sections of the whistle, easy to use ﬁlters, and the scanning depth function, which helps to increase the accuracy of the localization and provides more conﬁdence in determining the direction of the sound source. Additionally, four hydrophones, giving six times of arrival differences, result in a more reliable estimation of caller position…. Thus, arrays such as ours can be used to describe individual vocal behavior if a dolphin is relatively isolated and improve the investigation of vocal behavior of small groups. However, in dense interacting groups, localization to individuals is usually not possible with these methods. Further developments in recording techniques are necessary to investigate vocal behavior in close social interactions.
Executive Summary: A workshop was held in Seattle, Washington, 20-22 March 1996, to consider problems and uncertainties related to the use of acoustic deterrents in the conservation and management of marine mammals. Acoustic deterrent devices have been used to help solve two distinct types of fishery-marine mammal conflict:
1) bycatch of marine mammals in fishing gear, and
2) depredation by marine mammals on fish caught in fishing gear, confined in aquaculture enclosure is, or aggregated or constrained at “choke points” in river systems.
Acoustic alarms (mainly small, low-intensity sound-generators called “pingers”) have been developed for “alerting” marine mammals to the presence of fishing gear, with the goal of reducing bycatch rates. High-intensity acoustic “harassment”‘ devices (AHDs) have been used widely to reduce depredation on fish, especially by pinnipeds.
The workshop’s main objectives were to:
a) evaluate experimental and other evidence concerning the efficacy of acoustic deterrents in preventing or reducing interactions between marine mammals and fisheries, including aquaculture operation;
b) identify critical uncertainties about the effectiveness of acoustic deterrent devices and their effects on marine mammals and other biota;
c) identify and establish priorities for relevant research; and
d) develop guidelines for when, how, and under what conditions acoustic deterrents should be incorporated into management.
Workshop participants included representatives of the fishing industry, environmental groups, and manufacturers of acoustic deterrent devices, staff members from government agencies in the United States, Canada, and Australia, and scientists from seven countries and 21 institutions. Participants broke into working groups with specific terms of reference, and the reports of the working groups are included as part of the overall workshop report.
Expansion of the aquaculture industry off Scotland has lead to conflicts with marine predators such as seals, which predate species bred in aquaculture facilities and cause damage to equipment. To mitigate this, non-lethal management tools have been developed, the most popular of which are Acoustic Deterrent Devices (ADDs) or ‘seal scarers’. ADDs broadcast loud, aversive sounds within the hearing range of the target species (i.e. seals). However their success in addressing the issue has been variable. In addition their unregulated use in Scotland could pose unintended ecological impacts to non-target species such as the harbour porpoise (Phocoena phocoena). This study aimed to address the gap in knowledge on the extent of ADD use in the Scottish aquaculture industry, and to quantify the scale of their acoustic presence in Scottish waters. Acoustic data collected during cetacean line-transect surveys carried out by the Hebridean Whale and Dolphin Trust (HWDT) were used to map the acoustic presence of ADDs across the west coast between 2006 and 2015. Results found a significant spatial and temporal increase in ADD presence across the west coast study regions (detections per unit effort; 2006 = 0.5%; 2015 = 15.3%). This study highlights the large-scale extent of noise from ADDs use at fish farms across Scotland and illustrates its gradual increase over the study period. The increasing ensonification of the Scottish coastline which includes multiple protected areas for marine mammals, due to these devices may pose a risk to both target and non-target species (e.g. odontocete cetaceans) that use these areas either seasonally or year round. This study is one of the first to highlight the large-scale extent of ADD noise pollution and its overlap with marine mammal habitat. This information is crucial in order to effectively address European legislation related to underwater noise and marine species protection.
Available at: http://www.int-res.com/abstracts/dao/v41/n1/p43-51/
Abstract Relevant Quote: “The present study demonstrates biochemical changes resulting from sea lice infection of Atlantic salmon occurring at the site of host-pathogen interaction, the mucus layer.”
Summary Relevant Quote: “As observed previously by Grimnes & Jakobsen (1996), …high level of sea lice infection… resulted in mass mortality of infected salmon within a 24hr. period following the molt of the sea lice to the pre-adult stage. Heavy infestation of sea trout… also resulted in mortalities as the lice reached the pre-adult stage.”
Abstract: The changes in the activities of mucus hydrolytic enzymes and plasma cortisol levels were examined following infection of Atlantic salmon Salmo salar with the salmon louse Lepeophtheirus salmonis and these changes were compared with those resulting from elevated plasma cortisol. Salmon were infected at high (Trial 1; 178 ± 67) and low (Trial 2; 20 ± 13) numbers of lice per fish and the activities of proteases, alkaline phosphatase, esterase and lysozyme in the mucus, as well as plasma cortisol levels were determined. At both levels of infection, there were significant increases of protease activity over time (1-way K-WANOVA; Trial 1, p = 0.004; Trial 2, p < 0.001). On several sampling days, generally on later days in the infections, the mucus protease activities of infected fish were significantly higher than control fish (Student’s t-tests; p < 0.05). In addition, zymography experiments demonstrated bands of proteases at 17 to 22 kDa in the mucus of infected salmon that were absent in the mucus from non-infected fish and absent in the plasma of salmon. The intensity of these protease bands increased in the mucus over the course of both infections. However, plasma cortisol levels were elevated only in the heavily infected fish from the first trial. At high infection levels (Trial 1), alkaline phosphatase activity was higher in the mucus of infected fish at all days (t-test, p < 0.05). However, at the lower infection level (Trial 2), the mucus alkaline phosphatase activity did not differ significantly between infected and non-infected fish. Esterase and lysozyme activities were very low and did not change with time nor between non-infected and infected salmon in either challenge. Mucus enzyme activities of cortisol-implanted salmon did not change over time, nor were there any differences in activities between cortisol-implanted and control salmon. The present study demonstrates biochemical changes resulting from sea lice infection of Atlantic salmon occurring at the site of host-pathogen interaction, the mucus layer. However, the origin of these enzymes, whether host or pathogen, remains to be determined.
Available at: http://doi.org/10.1111/are.13567
Motivated by the need for additional tools to disinfect discharge water from well boats, and to prevent distribution of salmon lice, the effect of ultrasonic cavitation on the planktonic stages of the salmon louse, nauplii and copepodids, as well as marine heterotrophic bacteria, and the marine green microalgae Tetraselmis suecica, has been investigated. Survival and morphology were registered after different exposure times. Efficacy of the ultrasonic cavitation treatments varied with exposure time. A reduction in survival was registered even for the shortest exposure time (5 seconds) for both naupliar and copepodid stages of the salmon louse (36.7 ± 11.5 and 67.20 ± 7.2% survival respectively). Survival reached zero after exposure times of 20 and 60 seconds for the nauplii and copepodid stages, respectively. A reduction in 70% was observed for bacteria at all exposure times (5 to 300 s), while a reduction of 95% was observed after 300 s for algal cells. The logged energy transfer to the samples was on average 17.5 J/s. In conclusion, cavitation treatment is destructive for the planktonic stages of salmon lice, and may contribute to reduce discharge of pathogens and parasites from well boats when adapted for this purpose and combined with existing water disinfection methods.
Sample: In recent years, the number of aquaculture facilities using acoustic harassment devices (AHDs) in attempts to deter seals from approaching fish pens has increased, yet our understanding of the effects of these devices on both target and non-target species, in the short and long term, is still largely incomplete. This paper presents estimates of areas in which harbour porpoises (Phocoena phocoena) are likely to perceive and be affected by AHD sounds based on calculations using the source levels and attenuation characteristics….
Available at: http://link.springer.com/10.1007/978-3-642-41494-7_9
Relevant Quote: “Most marine mammals have sensitive enough hearing that they are limited by noise rather than the sensitivity of their auditory systems. …[I]n the 20−200 Hz band, the dominant source of sound in the sea stems from a human source: the propulsion of ships….As noise varies, the effective range for communication and echolocation would vary significantly if marine mammals did not have mechanisms to compensate for increased noise. Marine mammals have been shown to be able to compensate for noise by increasing the level of their own calls, by shifting their signal frequencies out of a noise band, by making their signals longer or more redundant, or by waiting to signal until noise is reduced. The mechanisms that involve modifying vocal output based upon auditory input have similarities with vocal production learning, and compensation for noise may have led to adaptations that close the neural loop between auditory input and vocal production. All of these mechanisms improve detection of signals in noise, but each is likely to incur costs, and it is not known whether they fully compensate for the effects of noise. At some levels of anthropogenic noise, animals leave an area near the source, reducing the amount of habitat available. As anthropogenic sound continues to increase in the ocean, the requirement for suitable conditions for communication means that effects of noise are one of the factors that must be monitored and regulated to maintain suitable environments for marine mammals.”
Abstract: Marine mammals rely on sound for communication, orientation, and locating prey. Baleen whales use low-frequency sound, to frequencies below 10 Hz, to communicate over ranges of tens to hundreds of km. Toothed whales use clicks at center frequencies of 10−160 kHz to echolocate on targets at ranges of tens to a few hundreds of meters. Most marine mammals have sensitive enough hearing that they are limited by noise rather than the sensitivity of their auditory systems. Ocean noise is dominated by sounds of geological activity below about 20 Hz, by wind and waves above 200 Hz, but in the 20−200 Hz band, the dominant source of sound in the sea stems from a human source: the propulsion of ships. Other industrial and military activities also introduce very powerful, transient sounds into the oceans. As noise varies, the effective range for communication and echolocation would vary significantly if marine mammals did not have mechanisms to compensate for increased noise. Marine mammals have been shown to be able to compensate for noise by increasing the level of their own calls, by shifting their signal frequencies out of a noise band, by making their signals longer or more redundant, or by waiting to signal until noise is reduced. The mechanisms that involve modifying vocal output based upon auditory input have similarities with vocal production learning, and compensation for noise may have led to adaptations that close the neural loop between auditory input and vocal production. All of these mechanisms improve detection of signals in noise, but each is likely to incur costs, and it is not known whether they fully compensate for the effects of noise. At some levels of anthropogenic noise, animals leave an area near the source, reducing the amount of habitat available. As anthropogenic sound continues to increase in the ocean, the requirement for suitable conditions for communication means that effects of noise are one of the factors that must be monitored and regulated to maintain suitable environments for marine mammals.