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Habitat Use Patterns of Coastal Shark Species in Relation to Boat Activity along an Urban Marine Gradient
Abstract
The effects of boat activity on various aspects of fish biology and ecology have been widely studied in the past few decades. However, these studies primarily focused on teleost fish species and not elasmobranchs. The goal of this study was to determine if there was a negative relationship between boat activity and the habitat use of three coastal shark species (bull (Carcharhinus leucas), nurse (Ginglymostoma cirratum), and great hammerhead (Sphyrna mokarran)) in Biscayne Bay, Florida - an area subject to intense boat activity (both commercial and recreational). According to past studies on marine mammals and teleost fish species, we expected sharks to present patterns of avoidance (reduced residency and activity space) during times and in areas of intense boat activity. Using aerial surveys and underwater recording stations, patterns of boat activity were quantified both spatially and temporally, while shark activity space and residency were determined using acoustic telemetry. Our results indicated that boat activity was more intense both on the weekends/holidays and closer to Miami Proper. However, there was no relationship between boat activity patterns and the activity space or residency of each species. These results may be explained by each species' hearing ability and how their detectable frequency range does not overlap with that produced by boat engines. Additionally, it is possible that the shark species in this area have habituated to the human activity and associated sound as demonstrated by a population of bottlenose dolphins (Tursiops truncates) in the same area. This study lays a foundation that future research can use to explore the relationship between boat activity and other vulnerable species as well as expand our current understanding of the relationship between sharks and urbanization.
... However, smalltooth sawfish are among many other species that continue to utilize the highly urbanized areas of Biscayne Bay HFA and surrounding waters, despite being subject to several synergistic stressors, including boat traffic and fishing. In addition to a more concentrated weekday and weekend boat traffic (Rider 2020), the City of Miami hosts a variety of boating shows and fishing events throughout the year. Nevertheless, the ecological shoreline of the Biscayne Bay HFA provides valuable hunting and foraging grounds for marine predators (Hammerschlag et al. 2010), and recent research has documented the use of this area by several shark species despite high levels of boat activity and vessel noise (Rider 2020). ...
... In addition to a more concentrated weekday and weekend boat traffic (Rider 2020), the City of Miami hosts a variety of boating shows and fishing events throughout the year. Nevertheless, the ecological shoreline of the Biscayne Bay HFA provides valuable hunting and foraging grounds for marine predators (Hammerschlag et al. 2010), and recent research has documented the use of this area by several shark species despite high levels of boat activity and vessel noise (Rider 2020). The considerable number of smalltooth sawfish detections recorded at receiver stations in urban areas is intriguing and leads to future questions about urbanization effects on habitat use by this species. ...
As coastal urbanization increases globally, the subsequent effects on marine animals, especially endangered species, inhabiting nearshore waters have become a research priority. The smalltooth sawfish Pristis pectinata , once abundant in US waters, now only persists in a few parts of its former range, including South Florida. Many areas utilized by smalltooth sawfish are estuarine systems or other shallow coastal habitats, making this species particularly vulnerable to threats associated with coastal development. To date, P. pectinata has been understudied in the waters in and around Biscayne Bay, Florida, a coastal waterway subjected to the urbanization of adjacent Miami-Dade County. Here, we summarize data from reported smalltooth sawfish encounters dating as far back as 1895 (N = 90) and detail opportune recordings (incidental catches, acoustic detections, and baited remote underwater videos) of sub-adults and adults (N = 14 individuals) in Biscayne Bay and the adjacent reef tract. These data demonstrate historical and increased contemporary use of the study area by this imperiled species, suggesting potential local and regional recovery. Most documented sawfish occurrences were near the urban center, indicating a need to understand the effects of coastal urbanization on sawfish and on the species' recovery potential. We suggest priorities for future research on P. pectinata in the study area that will assist in addressing regional management goals and contribute to understanding the ecology of smalltooth sawfish under environmental change.
Understanding the movement ecology of marine species is important for conservation management and monitoring their responses to environmental change. In this study, adult and subadult bull sharks (Carcharhinus leucas; n = 16) were acoustically tagged in Biscayne Bay, Florida (USA), where they were tracked locally via an array of 40 passive acoustic receivers, as well as regionally via cooperative acoustic telemetry networks, with individuals tracked up to 4.5 years. Detection data were used to assess philopatry, regional connectivity, and environmental correlates of shark habitat use. Spatial range varied per individual; however, most individuals displayed high residency to Biscayne Bay, exhibiting strong philopa-tric behavior to the tagging area. A generalized linear mixed model revealed a seasonal pattern in habitat use, with mature females displaying high residency in Biscayne Bay during the colder dry season (November to February) and lower residencies during the warmer wet season (June to October). These seasonal patterns were supported by catch data from long-term fishery-independent shark surveys in the study area. During summer months when residencies of C. leucas declined in Biscayne Bay, their residencies increased in other regions (e.g., Florida Gulf Coast), demonstrative of seasonal migrations. Connectivity between areas of high use (Biscayne Bay and Florida Gulf Coast) was demonstrated by some individuals traveling between these areas. Results from generalized additive mixed models suggest that these movement patterns could be partially driven by seasonal changes in environmental variables as well as an individual's life stage, including reproductive status.
Shipping routes in the ocean are analogous to terrestrial roads, in that they are regularly used thoroughfares that concentrate the movement of vessels between multiple locations. We applied a terrestrial road ecology framework to examine the ecological impacts of increased global shipping on “marine giants” (ie great whales, basking sharks [Cetorhinus maximus], and whale sharks [Rhincodon typus]). This framework aided in identifying where such “marine roads” and marine giants are likely to interact and the consequences of those interactions. We also reviewed known impacts of shipping routes on these species, and then applied the road ecology framework to detect unknown and potentially threatening processes. In the marine environment, such a framework can be used to incorporate knowledge of existing shipping impacts into management practices, thereby reducing the detrimental effects of future expansion of shipping routes on marine giants.
Sea ice reduction in the Arctic is allowing for increased vessel traffic and activity. Vessel noise is a known anthropogenic disturbance, but its effects on Arctic fish are largely unknown. Using acoustic telemetry — Vemco positioning system — we quantified the home ranges and fine-scale movement types (MT) of shorthorn sculpin (Myoxocephalus scorpius), a common benthic Arctic fish, in response to vessels and environmental drivers during open water over 3 years (2012–2014). Low overlap of core home ranges (50%) for all years and a change of overall MT proportions (significant in 2012 only) were observed when vessels were present compared with absent. However, changes in MTs associated with vessel presence were not consistent between years. Photoperiod was the only environmental driver that influenced (R² = 0.32) MTs of sculpin. This is the first study of vessel impacts on Arctic fish using acoustic telemetry and demonstrates that individuals alter their behavior and home ranges when vessels are present. Given increasing vessel traffic in the Arctic, additional study on the impact of vessels on these ecosystems is warranted.
Human generated noise is changing the natural underwater soundscapes worldwide. The most pervasive sources of underwater anthropogenic noise are motorboats, which have been found to negatively affect several aspects of fish biology. However, few studies have examined the effects of noise on early life stages, especially the embryonic stage, despite embryo health being critical to larval survival and recruitment. Here, we used a novel setup to monitor heart rates of embryos from the staghorn damselfish (Amblyglyphidodon curacao) in shallow reef conditions, allowing us to examine the effects of in situ boat noise in context with real-world exposure. We found that the heart rate of embryos increased in the presence of boat noise, which can be associated with the stress response. Additionally, we found 2-stroke outboard-powered boats had more than twice the effect on embryo heart rates than did 4-stroke powered boats, showing an increase in mean individual heart rate of 1.9% and 4.6%, respectively. To our knowledge this is the first evidence suggesting boat noise elicits a stress response in fish embryo and highlights the need to explore the ecological ramifications of boat noise stress during the embryo stage. Also, knowing the response of marine organisms caused by the sound emissions of particular engine types provides an important tool for reef managers to mitigate noise pollution.
Human noise pollution has increased markedly since the start of industrialization and there is international concern about how this may impact wildlife. Here we determined whether real motorboat noise affected the behavior, space use and escape response of a juvenile damselfish (Pomacentrus wardi) in the wild, and explored whether fish respond effectively to chemical and visual threats in the presence of two common types of motorboat noise. Noise from 30 hp 2-stroke outboard motors reduced boldness and activity of fish on habitat patches compared to ambient reef-sound controls. Fish also no longer responded to alarm odours with an antipredator response, instead increasing activity and space use, and fewer fish responded appropriately to a looming threat. In contrast, while there was a minor influence of noise from a 30 hp 4-stroke outboard on space use, there was no influence on their ability to respond to alarm odours, and no impact on their escape response. Evidence suggests that anthropogenic noise impacts the way juvenile fish assess risk, which will reduce individual fitness and survival, however, not all engine types cause major effects. This finding may give managers options by which they can reduce the impact of motorboat noise on inshore fish communities.
Noise produced by anthropogenic activities is increasing in many marine ecosystems. We investigated the effect of playback of boat noise on fish cognition. We focused on noise from small motorboats, since its occurrence can dominate soundscapes in coastal communities, the number of noise-producing vessels is increasing rapidly and their proximity to marine life has the potential to cause deleterious effects. Cognition-or the ability of individuals to learn and remember information-is crucial, given that most species rely on learning to achieve fitness-promoting tasks, such as finding food, choosing mates and recognizing predators. The caveat with cognition is its latent effect: the individual that fails to learn an important piece of information will live normally until the moment where it needs the information to make a fitness-related decision. Such latent effects can easily be overlooked by traditional risk assessment methods. Here, we conducted three experiments to assess the effect of boat noise playbacks on the ability of fish to learn to recognize predation threats, using a common, conserved learning paradigm. We found that fish that were trained to recognize a novel predator while being exposed to 'reef + boat noise' playbacks failed to subsequently respond to the predator, while their 'reef noise' counterparts responded appropriately. We repeated the training, giving the fish three opportunities to learn three common reef predators, and released the fish in the wild. Those trained in the presence of 'reef + boat noise' playbacks survived 40% less than the 'reef noise' controls over our 72 h monitoring period, a performance equal to that of predator-naive fish. Our last experiment indicated that these results were likely due to failed learning, as opposed to stress effects from the sound exposure. Neither playbacks nor real boat noise affected survival in the absence of predator training. Our results indicate that boat noise has the potential to cause latent effects on learning long after the stressor has gone.
Stellwagen Bank National Marine Sanctuary is located in Massachusetts Bay off the densely populated northeast coast of the United States; subsequently, the marine inhabitants of the area are exposed to elevated levels of anthropogenic underwater sound, particularly due to commercial shipping. The current study investigated the alteration of estimated effective communication spaces at three spawning locations for populations of the commercially and ecologically important fishes, Atlantic cod (Gadus morhua) and haddock (Melanogrammus aeglefinus). Both the ambient sound pressure levels and the estimated effective vocalization radii, estimated through spherical spreading models, fluctuated dramatically during the three-month recording periods. Increases in sound pressure level appeared to be largely driven by large vessel activity, and accordingly exhibited a significant positive correlation with the number of Automatic Identification System tracked vessels at the two of the three sites. The near constant high levels of low frequency sound and consequential reduction in the communication space observed at these recording sites during times of high vocalization activity raises significant concerns that communication between conspecifics may be compromised during critical biological periods. This study takes the first steps in evaluating these animals’ communication spaces and alteration of these spaces due to anthropogenic underwater sound.
The negative impact of anthropogenic noise on marine animals is receiving increasing
attention. In order to study the effect of motorboat noise on foraging behaviour in fish, we
chose 2 species with different hearing abilities. The roach Rutilus rutilus has a better developed
sense of hearing than the Eurasian perch Perca fluviatilis. The study took place in an inlet of the
Bothnian Sea where boat traffic is almost absent. Groups of 6 fish were placed in field enclosures
containing either one of the species or equal numbers of perch and roach. Half of each enclosure
was covered with artificial vegetation. The fish were fed with pieces of saithe twice a day, both
with and without the disturbance of an outboard motor. Sound pressure level and particle acceleration
were measured for the motor, which was run at 2000 rpm. The trials were repeated for 5 d.
Perch made fewer feeding attempts during noise exposure compared to controls in the single-species
enclosures. As the experiment progressed, they gradually increased feeding and time
spent in the open area, both with and without noise, indicating habituation. Habitat utilization was
affected by the interaction of noise exposure and day. Roach responded to noise exposure with
fewer feeding attempts, higher latency to enter the open area, and longer time spent in the vegetation
compared to the controls without noise. Roach behaviour changed with time only when
housed together with perch. This study, using authentic sound in a natural habitat, shows that
noise exposure may affect the feeding behaviour of fish, that the response is species-specific, and
that habituation and the presence of other species may modify the effects.
A thorough understanding of movement patterns of a species is critical for designing effective conservation and management initiatives. However, generating such information for large marine vertebrates is challenging, as they typically move over long distances, live in concealing environments, are logistically difficult to capture and, as upper-trophic predators, are naturally low in abundance. Large-bodied, broadly distributed tropical shark typically restricted to coastal and shelf habitats, the great hammerhead shark Sphyrna mokarran epitomizes such challenges. Highly valued for its fins (in target and incidental fisheries), it suffers high bycatch mortality coupled with fecundity conservative life history, and as a result, is vulnerable to over-exploitation and population depletion. Although there are very little species-specific data available, the absence of recent catch records give cause to suspect substantial declines across its range. Here, we used biotelemetry techniques (acoustic and satellite), conventional tagging, laser-photogrammetry, and photo-identification to investigate the level of site fidelity/residency for great hammerheads to coastal areas in the Bahamas and U.S., and the extent of movements and connectivity of great hammerheads between the U.S. and Bahamas. Results revealed large-scale return migrations (3030 km), seasonal residency to local areas (some for 5 months), site fidelity (annual return to Bimini and Jupiter for many individuals) and numerous international movements. These findings enhance the understanding of movement ecology in great hammerhead sharks and have potential to contribute to improved conservation and management.
Submerged passive acoustic technology allows researchers to investigate spatial and temporal movement patterns of many marine and freshwater species. The technology uses receivers to detect and record acoustic transmissions emitted from tags attached to an individual. Acoustic signal strength naturally attenuates over distance, but numerous environmental variables also affect the probability a tag is detected. Knowledge of receiver range is crucial for designing acoustic arrays and analyzing telemetry data. Here, we present a method for testing a relatively large-scale receiver array in a dynamic Caribbean coastal environment intended for long-term monitoring of multiple species. The U.S. Geological Survey and several academic institutions in collaboration with resource management at Buck Island Reef National Monument (BIRNM), off the coast of St. Croix, recently deployed a 52 passive acoustic receiver array. We targeted 19 array-representative receivers for range-testing by submersing fixed delay interval range-testing tags at various distance intervals in each cardinal direction from a receiver for a minimum of an hour. Using a generalized linear mixed model (GLMM), we estimated the probability of detection across the array and assessed the effect of water depth, habitat, wind, temperature, and time of day on the probability of detection. The predicted probability of detection across the entire array at 100 m distance from a receiver was 58.2% (95% CI: 44.0-73.0%) and dropped to 26.0% (95% CI: 11.4-39.3%) 200 m from a receiver indicating a somewhat constrained effective detection range. Detection probability varied across habitat classes with the greatest effective detection range occurring in homogenous sand substrate and the smallest in high rugosity reef. Predicted probability of detection across BIRNM highlights potential gaps in coverage using the current array as well as limitations of passive acoustic technology within a complex coral reef environment.
Evidence suggests the great hammerhead shark, Sphyrna mokarran,
is vulnerable to a variety of anthropogenic stressors, and is an
understudied species of shark due to its cryptic nature and wideranging
movements. While recognized as both a pelagic-coastal and
a highly mobile predator, minimal anecdotal evidence exist describing
shallow water habitat use by this species. This report describes six
cases in which a great hammerhead shark utilizes an inshore shallow
water flats environment (<1.5 m in depth), five of which involve prey
capture. These observations permitted identification of two novel
behaviors that may allow great hammerheads to inhabit these
shallow habitats: a (1) prey-capture technique termed ‘grasp-turning’
that involves burst swimming at tight turning angles while grasping
prey and (2) a post-predation recovery period whereby the shark
maintains head-first orientation into the current that may facilitate
respiration and prey consumption. These behavioral observations
provide insights into the natural history of this species.
The present study tested different sounds that could disturb eagle rays (Aetobatus ocellatus) during their foraging activities at Moorea, French Polynesia. Results showed that artificial white sound and single-frequency tones (40Hz, 600Hz or 1kHz) did not have an effect on rays (at least 90% of rays continued to forage over sand), while playbacks of boat motor sound significantly disturbed rays during foraging activity (60% exhibited an escape behaviour). Overall, our study highlighted the negative effect of boat noises on the foraging activity of eagle rays. These noises produced by boat traffic could, however, have some positive effects for marine aquaculture if they could be used as a deterrent to repel the eagle rays, main predators of the pearl oysters.
Combining calibrated hydrophone measurements with vessel location data from the Automatic Identification System, we estimate underwater sound pressure levels for 1,582 unique ships that transited the core critical habitat of the endangered Southern Resident killer whales during 28 months between March, 2011, and October, 2013. Median received spectrum levels of noise from 2,809 isolated transits are elevated relative to median background levels not only at low frequencies (20–30 dB re 1 µPa
2
/Hz from 100 to 1,000 Hz), but also at high frequencies (5–13 dB from 10,000 to 96,000 Hz). Thus, noise received from ships at ranges less than 3 km extends to frequencies used by odontocetes. Broadband received levels (11.5–40,000 Hz) near the shoreline in Haro Strait (WA, USA) for the entire ship population were 110 ± 7 dB re 1 µPa on average. Assuming near-spherical spreading based on a transmission loss experiment we compute mean broadband source levels for the ship population of 173 ± 7 dB re 1 µPa 1 m without accounting for frequency-dependent absorption. Mean ship speed was 7.3 ± 2.0 m/s (14.1 ± 3.9 knots). Most ship classes show a linear relationship between source level and speed with a slope near +2 dB per m/s (+1 dB/knot). Spectrum, 1/12-octave, and 1/3-octave source levels for the whole population have median values that are comparable to previous measurements and models at most frequencies, but for select studies may be relatively low below 200 Hz and high above 20,000 Hz. Median source spectrum levels peak near 50 Hz for all 12 ship classes, have a maximum of 159 dB re 1 µPa
2
/Hz @ 1 m for container ships, and vary between classes. Below 200 Hz, the class-specific median spectrum levels bifurcate with large commercial ships grouping as higher power noise sources. Within all ship classes spectrum levels vary more at low frequencies than at high frequencies, and the degree of variability is almost halved for classes that have smaller speed standard deviations. This is the first study to present source spectra for populations of different ship classes operating in coastal habitats, including at higher frequencies used by killer whales for both communication and echolocation.
Background: False-positive data (better known as “false detections”) in VEMCO VR2 acoustic telemetry monitor-ing studies that use pulse position modulation coding can cause biased or erroneous outcomes in data analysis. To understand the occurrence of false detections in acoustic monitoring data sets, the results of a range test experiment using eight acoustic receivers and 12 transmitters were examined.
Results:One hundred and fifty one tag ID codes were recorded, 137 of which were identified as likely from false detections, 12 were from test tags, and two were from tagged sharks. False detections accounted for <0.05% of detections (918) in the experiment. False detection tag ID codes were not randomly distributed amongst the avail-able codes, being more likely to occur at IDs close to tags used in the experiment. Receivers located near the bottom recorded the most false detections and tag ID codes from false detections. Receivers at the same depth did not differ significantly in the mean number of daily false detections. The daily number of false detections recorded by a receiver did not conform to a random pattern, and was not strongly correlated with daily receiver performance.
Conclusions:In an era of increasing data sharing and public storage of scientific data, the occurrence of false detections is of significant concern and the results of this study demonstrate that while rare they do occur and can be identified and accounted for in analyses.
This study examined the effects of boat noise pollution on the stress indices of gilthead sea bream (Sparus aurata, Linnaeus 1758). To assess the stress response in these fish, biometric values and plasma parameters such as ACTH, cortisol, glucose, lactate, haematocrit, Hsp70, total protein, cholesterol, triglycerides and osmolarity were analysed. After acclimatization of the animals, the experiment was carried out in a tank fitted with underwater speakers where the fish were exposed to sound treatments (in duplicate) consisting of: 10 days of no sound (control treatment; the animals were only exposed to the experimental tank's background noise) and 10 days of noise derived from original recordings of motor boats, including recreational boats, hydrofoil, fishing boat and ferry boat (vessel noise treatment). The exposure to noise produced significant variations in almost all the plasma parameters assessed, but no differences were observed in weights and fork lengths. A PERMANOVA analysis highlighted significantly increased values (p < 0.05) of ACTH, cortisol, glucose, lactate, haematocrit, Hsp70, cholesterol, triglycerides and osmolarity in the fish exposed to vessel noise for 10 days. This study clearly highlights that anthropogenic noise negatively affects fish, and they are valuable targets for detailed investigations into the effects of this global pollutant. Finally, these experimental studies could represent part of the science that is able to improve the quality of the policies related to management plans for maritime spaces (Marine Strategy Framework Directive 56/2008 CE) that are aimed at stemming this pollutant phenomenon.
Anthropogenic noise in the ocean has increased substantially in recent decades, and motorized vessels produce what is likely the most common form of underwater noise pollution. Noise has the potential to induce physiological stress in marine fishes, which may have negative ecological consequences. In this study, physiological effects of increased noise (playback of boat noise recorded in the field) on a coastal marine fish (the giant kelpfish, Heterostichus rostratus) were investigated by measuring the stress responses (cortisol concentration) of fish to increased noise of various temporal dynamics and noise levels. Giant kelpfish exhibited acute stress responses when exposed to intermittent noise, but not to continuous noise or control conditions (playback of recorded natural ambient sound). These results suggest that variability in the acoustic environment may be more important than the period of noise exposure for inducing stress in a marine fish, and provide information regarding noise levels at which physiological responses occur.
This chapter, written from the perspective of four authors who have been studying fish bioacoustics for over 120 years (cumulative!), examines the major issues of the field. Each topic is put in some historical perspective, but the chapter emphasizes current thinking about acoustic communication, hearing (including bandwidth, sensitivity, detection of signals in noise, discrimination, and sound source localization), the functions of the ear (both auditory and vestibular, and including the role(s) of the otoliths and sensory hair cells) and their relationships to peripheral structures such as the swim bladder, and the interactions between the ear and the lateral line. Hearing in fishes is not only for acoustic communication and detection of sound-emitting predators and prey but can also play a major role in telling fishes about the acoustic scene at distances well beyond the range of vision. The chapter concludes with the personal views of the authors as to the major challenges and questions for future study. There are still many gaps in our knowledge of fish bioacoustics, including questions on ear function and the significance of interspecific differences in otolith size and shape and hair cell orientation, the role of the lateral line vis-à-vis the ear, the mechanisms of central processing of acoustic (and lateral line) signals, the mechanisms of sound source localization and whether fishes can determine source distance as well as direction, the evolution and functional significance of hearing specializations in taxonomically diverse fish species, and the origins of fish (and vertebrate) hearing and hearing organs.
The passive listening technique is a non-invasive, cheap and reliable method for monitoring man-made noise levels as well as fish communicative sounds, in order to characterize the acoustic energies (spectra, level and duration) as potential factors injuring fish populations. We conducted three passive listening surveys in the Venetian littoral using a pre-amplified Reson TC4032 hydrophone connected to a portable micro recorder generating WAV files (signals were calibrated before each recording using a generator of pure waves of known voltage). We calculated the spectral content and the intensity level of underwater noise in all recording sites (total of 12 recording sites). Furthermore, we monitored acoustically the brown meagre (Sciaena umbra L.) populations during the spawning season, analysing the sound patterning and rate across a spatial grid. The passive listening technique proved to be successful in detecting S. umbra drumming sounds in two Venetian inlets, whereas this species was absent in the inner Venice lagoon. Underwater noise was more intense in the inner city due to the heavy boat traffic (public transports, commercial ships and ship cruises). The frequency range of the anthropogenic noise detected in the Venice lagoon matched the hearing frequency range of most fish. Our results indicate that the spectral content and the level of underwater noise pollution in the Venice lagoon could potentially affect fish acoustic communication.
Historically, acoustic telemetry studies tracking movement of aquatic organisms have lacked rigorous, long-term evaluations of detection range. The purpose of the present study was to identify potential sources of variability in long-term acoustic telemetry data, focusing specifically on environmental variability. The study was conducted for 15 mo in Gray's Reef National Marine Sanctuary, Georgia, USA, using 2 submersible Vemco VR2W hydrophone receivers and 2 stationary range test transmitters (controls). Tag detections (+/- 1 SE) decreased from 54.2 +/- 2.5 to 11.4 +/- 0.5 detections d(-1) as transmission distance increased from 100 to 300 m. Detections varied seasonally (likely due to stratification), with the direction of flood and ebb tidal currents (12.4 h cycle), and with tidal current speed (6.2 h cycle). Tides explained up to 92% of the short-term variability in hourly detection data. Detections also increased or decreased during episodic weather events depending on the season and type of event. These results suggest that stationary control tags are useful for characterizing variability in sound transmission in open water marine acoustic telemetry studies.
Subtle ecological and behavioral mechanisms that enhance reproduction such as nest building by animals may provide useful information of population level processes. Variation in behavioral traits may be observed as phenotypic traits that are shaped by sexual and natural selection. Using ecological sampling of benthic substrata and underwater video recordings, we assessed nest-building behavior through habitat modifications, and size of individuals performing parental care behavior and egg/hatching traits of an abundant temperate reef fish, Chromis crusma.
We identified that only male individuals performed nest building and uniparental care. We noted that nests containing filamentous green or red algae had the highest percent cover of eggs. Using video recordings, we provided evidence of parental care. Male individuals spent nearly 80% of their time inside the nest, aerating the eggs with their fins and mouth, removing unwanted materials, and defending the nest against conspecific, heterospecific, and other predators. The field-collected eggs, characterized by an oil globule and adhesive filaments, hatched after 7 days in the laboratory. The nest-building and parental care behavior of C. crusma lasted for 3 months, and several nests can be constructed throughout the season.
The behavior of building and defending the nests, which is a characteristic of the family members, is a key aspect for the success of the C. crusma; this fish is abundant in kelp ecosystems of the southeastern Pacific.
Hydroelectric development is considered a threat to the recovery of Lake Sturgeon Acipenser fulvescens populations, in part because of injury and mortality concerns caused by interaction with hydroelectric facilities. Lake Sturgeon resident in small impoundments may be particularly susceptible to entrainment, depending on movement and habitat usage patterns. Using acoustic telemetry, we monitored coarse-scale movements of 99 juvenile, subadult and adult Lake Sturgeon captured throughout a 10-km-long hydroelectric reservoir. Overall, adults moved over larger ranges than did smaller size-classes. However, all size-classes utilized habitat immediately upstream of hydroelectric facilities, and during the 18-month study period, 27% of subadults tagged in the lowermost section of the reservoir, and 8.7% of adults tagged throughout the reservoir were entrained. Movements of juveniles and subadults were generally restricted to extended sections (2–6 km) of contiguous deepwater habitat (>15 m), and passage through the two shallow river narrows that subdivide the reservoir were rare. Over half of the tagged adults (52%) moved upstream or downstream through one or both river narrows, albeit infrequently. Initial residency influenced entrainment susceptibility for juveniles and subadults but not for adults. Results suggest that Lake Sturgeon resident in small impoundments are susceptible to entrainment. However, the presence of river narrows, which function as natural movement restrictors, may largely preclude susceptibility of juveniles and subadults resident in upstream sections.
Fishes are constantly exposed to various sources of noise in their underwater acoustic environment. Many of these sounds are from anthropogenic sources, especially engines of boats. Noise generated from a small boat with a 55 horsepower outboard motor was played back to fathead minnows, Pimephales promelas, for 2 h at 142 dB (re: 1 Pa), and auditory thresholds were measured using the auditory brainstem response (ABR) technique. The results demonstrate that boat engine noise significantly elevate a fish's auditory threshold at 1 kHz (7.8 dB), 1.5 kHz (13.5 dB), and 2.0 kHz (10.5 dB), the most sensitive hearing range of this species. Such a short duration of noise exposure leads to significant changes in hearing capability, and implies that man-made noise generated from boat engines can have far reaching environmental impacts on fishes.
Acoustic telemetry is an increasingly common tool for studying the movement patterns, behavior and site fidelity of marine organisms, but to accurately interpret acoustic data, the variability, periodicity and range of detectability between acoustic tags and receivers must be understood. The relative and interactive effects of topography with biological and environmental noise have not been quantified on coral reefs. We conduct two long-term range tests (1- and 4-month duration) on two different reef types in the central Red Sea to determine the relative effect of distance, depth, topography, time of day, wind, lunar phase, sea surface temperature and thermocline on detection probability. Detectability, as expected, declines with increasing distance between tags and receivers, and we find average detection ranges of 530 and 120 m, using V16 and V13 tags, respectively, but the topography of the reef can significantly modify this relationship, reducing the range by ~70 %, even when tags and receivers are in line-of-sight. Analyses that assume a relationship between distance and detections must therefore be used with care. Nighttime detection range was consistently reduced in both locations, and detections varied by lunar phase in the 4-month test, suggesting a strong influence of biological noise (reducing detection probability up to 30 %), notably more influential than other environmental noises, including wind-driven noise, which is normally considered important in open-water environments. Analysis of detections should be corrected in consideration of the diel patterns we find, and range tests or sentinel tags should be used for more than 1 month to quantify potential changes due to lunar phase. Some studies assume that the most usual factor limiting detection range is weather-related noise; this cannot be extrapolated to coral reefs.
Passive acoustic telemetry provides an important tool to study the spatial ecology and behaviour of organisms in marine and freshwater systems, but understanding the detection range of acoustic receivers is critical for interpreting acoustic data and establishing receiver spacing to maximize study efficiency. This study presents a comprehensive review of how acoustic detection range has been considered and assessed to date, summarizes important variables to monitor when determining the detection range of a receiver array, and provides recommendations to account for detection range during experimental design, analysis and data interpretation. A total of 378 passive acoustic telemetry studies (1986–2012) were scored against a set of pre-defined criteria to provide a standardized assessment of how well detection range was accounted for, from a maximum possible score of 45. Scores ranged from 0 to 39 (11.1 ± 0.4; mean ± 1 SE). Over the past decade mean scores have been consistently between 6.7 and 12.9 which indicates that detection range has not been adequately considered in most contemporary acoustic telemetry studies. Given the highly variable nature of detection range over space and time, it is necessary to create a culture of detection range testing among the scientific community. For robust telemetry studies it is recommended that consideration of detection range should be given a greater focus within study design, execution and data analysis. To aid array design in new systems, short-term detection range tests should be conducted in the most representative area of the study system prior to deployment. As well, fixed distance sentinel tags should ideally be deployed at a representative receiver site within the array to provide a continuous assessment of detection range and influential environmental parameters should be monitored to facilitate modeling of detection range variability over time. When warranted, data analysis should incorporate modeled variation in detection ranges.
• Recreational boating activity has the potential to generate noise pollution that may influence wild fish. Such noise may be particularly relevant to fish engaged in parental care (PC), where alterations in behaviour could influence individual fitness and productivity of fish populations.
• Here, the PC behaviour of the freshwater largemouth bass (Micropterus salmoides) was examined to determine whether disturbance from boat noise altered paternal behaviour. Changes in nest‐tending and brood‐guarding behaviour were measured following exposure to noise treatments of 1‐min duration using underwater playbacks of recorded boat noises.
• One experiment compared the behaviour of bass tending eggs before, during, and after exposure to high‐speed or idling combustion motors, or an electronic bow‐mounted trolling motor. No significant differences in the time on nest, number of pectoral fin beats, and number of turns between the pre‐treatment, treatment, and post‐treatment periods for all three motor types were observed.
• A second experiment assessed the impacts of noise (high‐speed combustion motor only) on the behaviour of nesting bass across the development stages of offspring (i.e. egg, egg‐sac fry, and swim‐up fry). During the egg‐sac fry stage, nest‐guarding males turned significantly less on the nest during the noise treatment compared with the long‐term post‐treatment period, indicating a stage‐specific impact of boat noise on parental behaviour. The effect was transient, however, and limited to the period that the noise was present.
• Given that PC and recreational boating activity tend to co‐occur in nearshore areas, prolonged or frequent repeated exposure of nesting fish to boat noise during the egg‐sac fry stage could have adverse consequences for fitness and reproductive output. Efforts to restrict recreational boating activity in the vicinity of fish engaged in PC (e.g. through the use of set‐backs) would be a risk‐averse approach to mitigating the effects of noise pollution on fish.
Anthropogenic noise across the world’s oceans threatens the ability of vocalizing marine species to communicate. Some species vocalize at key life stages or whilst foraging, and disruption to the acoustic habitat at these times could lead to adverse consequences at the population level. To explore the risk of such impacts, we investigated the effect of vessel noise on the communication space of the Bryde’s whale Balaenoptera edeni, an endangered species which vocalizes at low frequencies and bigeye Pempheris adspersa, a nocturnal fish species which uses contact calls to maintain group cohesion while foraging. By combining long-term acoustic monitoring data with AIS vessel-tracking data and acoustic propagation modelling, a quantitative method for determining the impact of vessel noise on their communication space was established. Routine vessel passages cut down communication space by up to 61.5% for bigeyes and 87.4% for Bryde’s whales. The influence of vessel noise on communication space also exceeded natural variability between 3.9 and 18.9% of the monitoring period. To combat potential effects of vessel sound, we propose the application or extension of ship speed restrictions in ecologically significant areas, since our results indicate a reduction in sound source levels for vessels transiting at lower speeds.
Artificial light at night (ALAN) is spreading worldwide and thereby is increasingly interfering with natural dark-light cycles. Meanwhile, effects of very low intensities of light pollution on animals have rarely been investigated. We explored the effects of low intensity ALAN over seven months in eight experimental bank vole (Myodes glareolus) populations in large grassland enclosures over winter and early breeding season, using LED garden lamps. Initial populations consisted of eight individuals (32 animals per hectare) in enclosures with or without ALAN. We found that bank voles under ALAN
experienced changes in daily activity patterns and space use behavior, measured by automated radiotelemetry. There were no differences in survival and body mass, measured with live trapping, and none in levels of fecal glucocorticoid metabolites. Voles in the ALAN treatment showed higher activity at night during half moon, and had larger day ranges during new moon. Thus, even low levels of light pollution as experienced in remote areas or by sky glow can lead to changes in animal behavior and could have
consequences for species interactions.
The aquatic environment is increasingly bombarded by a wide variety of noise pollutants, whose range and intensity are increasing with each passing decade. Yet little is known about how aquatic noise affects marine communities. To determine the implications that changes to the soundscape may have on fishes, a meta-analysis was conducted focusing on the ramifications of noise on fish behavior and physiology. Our meta-analysis identified 42 studies that produced 2,354 data points, which in turn indicated that anthropogenic noise negatively affects fish behavior and physiology. The most predominate responses occurred within foraging ability, predation risk, and reproductive success. Additionally, anthropogenic noise was shown to increase the hearing thresholds and cortisol levels of numerous species while tones, biological, and environmental noise were most likely to affect complex movements and swimming abilities. These findings suggest that the majority of fish species are sensitive to changes in the aquatic soundscape, and depending on the noise source, species responses may have extreme and negative fitness consequences. As such this global synthesis should serve as a warning of the potentially dire consequences facing marine ecosystems if alterations to aquatic soundscapes continue on their current trajectory. This article is protected by copyright. All rights reserved.
We assess the impact of recreational boat traffic on sensitive habitats in the Western Mediterranean using passive acoustics. We compared underwater sounds in three regulated mooring locations vs a pristine location; and temporal differences in the pristine location vs the nearest mooring between high and low touristic seasons. We measured the number of pulses/minute, fish pulse patterns, and percentage of boat noise occurrence and its relative average power level. At the pristine location, the call rates and their complexity were significantly higher and the motorboat noise was significantly lower. The temporal trend of biophonic sounds decreased significantly in the pristine location. In contrast, in the mooring sites, the motorboat noise decreased significantly and the fish calls remained at low levels in both seasons. In conclusion, motorboat noise negatively affects the complexity of the fish assemblages but could be conditioned to their historic uses.
In both commercial and recreational fisheries, sharks are captured and released alive to comply with regulations or due to low economic value or voluntary conservation ethic. As a result, understanding the physiological and behavioural responses of sharks to capture stress is important for determining subsequent effects of fisheries interactions on a species-specific basis, as well as for identifying factors that influence mortality. Here, we employed a suite of conventional blood physiology endpoints (glucose, lactate, and haematocrit) integrated with assessments of reflex impairment on blacktip (Carcharhinus limbatus), great hammerhead (Sphyrna mokarran), nurse (Ginglymostoma cirratum) and sand-bar sharks (Carcharhinus plumbeus) captured via experimental drumline gear. We documented a wide range of species-specific differences in all parameters assessed, with nurse sharks consistently having the lowest relative levels of physiological disturbance and reflex impairment; and with great hammerheads exhibiting the highest level of physiological disturbance and reflex impairment, suggesting higher vulnerability to fishing. In general, increases in lactate were positively associated with hook time and correlated with reflex impairment assessment. Moreover, reflex indices showed significant impairment with hook time, with the "jaw" reflex emerging as the most potential predictor of disturbance. Our study results connect previously reported species-specific at-vessel and post-release mortality rates to their physiological disturbance and reflex impairment.
The impact of marine ecotourism on reef predators is poorly understood and there is growing concern that overcrowding in Marine Protected Areas (MPAs) may disturb the species that these areas were established to protect. To improve our understanding of this issue, we used acoustic telemetry to examine the relationship between human activity at the Molokini Marine Life Conservation District (MLCD) and the habitat use of five reef-associated predators (Caranx melampygus, Caranx ignobilis, Triaenodon obesus, Carcharhinus amblyrhynchos, and Aprion virscens). During peak hours of human use, there was a negative relationship (R² = 0.77, P < 0.001) between the presence of bluefin trevally (Caranx melampygus) and vessels in subzone A. No other species showed strong evidence of this relationship. However, our results suggest that during this time, the natural ecosystem function that the reserve was established to protect may be compromised and overcrowding should be considered when managing MPAs.
In the last few decades, technological developments and the widespread rise of anthropic activities have increased the exposure of organisms to noise pollution, thus evoking great interest in its biological effects, particularly on the immune system. The aim of the present work was to investigate some of the biochemical parameters in the blood of Chromis chromis (Linnaeus, 1758) following in vivo exposure to noise levels of 200 and 300 Hz. Our results revealed that, compared to the control specimens, the fish exposed to noise had significantly increased levels of stress biomarkers such as glucose, lactate and total proteins in plasma, as well as a rise in the expression of heat shock protein 70 (HSP70).
Urban land and seascapes are increasingly exposed to artificial lighting at night (ALAN), which is a significant source of light pollution. A broad range of ecological effects are associated with ALAN, but the changes to ecological processes remain largely unstudied. Predation is a key ecological process that structures assemblages and responds to natural cycles of light and dark. We investigated the effect of ALAN on fish predatory behaviour, and sessile invertebrate prey assemblages. Over 21 days fish and sessile assemblages were exposed to 3 light treatments (Day, Night and ALAN). An array of LED spotlights was installed under a wharf to create the ALAN treatments. We used GoPro cameras to film during the day and ALAN treatments, and a Dual frequency IDentification SONar (DIDSON) to film during the night treatments. Fish were most abundant during unlit nights, but were also relatively sedentary. Predatory behaviour was greatest during the day and under ALAN than at night, suggesting that fish are using structures for non-feeding purposes (e.g. shelter) at night, but artificial light dramatically increases their predatory behaviour. Altered predator behaviour corresponded with structural changes to sessile prey assemblages among the experimental lighting treatments. We demonstrate the direct effects of artificial lighting on fish behaviour and the concomitant indirect effects on sessile assemblage structure. Current and future projected use of artificial lights has the potential to significantly affect predator-prey interactions in marine systems by altering habitat use for both predators and prey. However, developments in lighting technology are a promising avenue for mitigation. This is among the first empirical evidence from the marine system on how ALAN can directly alter predation, a fundamental ecosystem process, and have indirect trophic consequences.
Free-ranging individual fish were observed using a baited remote underwater video (BRUV) system during
sound playback experiments. This paper reports on test trials exploring BRUV design parameters, image analysis and practical experimental designs. Threemarine specieswere exposed to playback noise, provided as examples of behavioural responses to impulsive sound at 163–171 dB re 1 μPa (peak-to-peak SPL) and continuous sound of 142.7 dB re 1 μPa (RMS, SPL), exhibiting directional changes and accelerations. The methods described here indicate the efficacy of BRUV to examine behaviour of free-ranging species to noise playback, rather than using confinement. Given the increasing concern about the effects of water-borne noise, for example its inclusion within the EU Marine Strategy Framework Directive, and the lack of empirical evidence in setting thresholds, this paper discusses the use of BRUV, and short term behavioural changes, in supporting population level marine noise management.
When it comes to hearing and vocal communication in fishes, the plainfin midshipman (Porichthys notatus) is perhaps best understood. However, distinctly lacking are studies investigating communication of P. notatus in its natural ecosystems and the effects of noise on wild fish populations. Here, an exploratory look into both is discussed. By monitoring a population of wild P. notatus off British Columbia, Canada, call patterns were distinguished, the function of communicative sounds was identified, and midshipman vocalizations in agonistic encounters with natural predators were evaluated. A preliminary investigation into the effects of boat noise on wild midshipman is also described.
We are living in a century of rapid urbanisation. The United Nations forecasts that by the year 2025, 60% of the world???s population will be living in urban areas, compared to 29% in 1950. The 50% mark will be reached between the years 2000 and 2010. In 2025, more than a dozen cities will have over 20 million inhabitants, and some will have over 30 million. 23 of the 25 biggest urban conglomerations on the planet will be in Africa, Asia and Latin America, rather than in Europe or North America.
De Robertis, A., and Wilson, C. D. 2011. Silent ships do not always encounter more fish (revisited): comparison of acoustic backscatter from walleye pollock recorded by a noise-reduced and a conventional research vessel in the eastern Bering Sea. – ICES Journal of Marine Science, 68: 2229–2239.
Vessel-induced avoidance behaviour is potentially a major source of error in surveys of fish populations. Noise-reduced research vessels have been constructed in an effort to minimize fish reactions to auditory stimuli produced by survey vessels. Here, measurements of acoustic backscatter from walleye pollock (Theragra chalcogramma) made on the eastern Bering Sea Shelf from the conventional NOAA ship “Miller Freeman” (MF) are compared with similar measurements made on the noise-reduced NOAA ship “Oscar Dyson” (OD). As in a previous study, acoustic abundance measurements from these vessels were equivalent during daylight, when large-scale acoustic surveying is conducted. However, significant differences were observed at night: on average, 44% more pollock backscatter was observed from OD than MF. Observations with a free-drifting echosounder buoy suggest that the night-time discrepancy is attributable to a stronger behavioural response to the passage of the louder MF, and a resulting decrease in pollock target strength. Pollock did not exhibit a strong reaction to the passage of OD. These observations are consistent with previous comparisons of these vessels, which show that with vessel differences, the noise-reduced OD detects more pollock.
After a pelagic larval phase, settlement-stage coral reef fish must locate a suitable reef habitat for juvenile life. Reef noise, produced by resident fish and invertebrates, provides an important cue for orientation and habitat selection during this process, which must often occur in environments impacted by anthropogenic noise. We adapted an established field-based protocol to test whether recorded boat noise influenced the settlement behavior of reef fish. Fewer fish settled to patch reefs broadcasting boat + reef noise compared with reef noise alone. This study suggests that boat noise, now a common feature of many reefs, can compromise critical settlement behavior of reef fishes.
The diving reaction of Sardinella aurita under a survey vessel seems rather limited in comparison to herring schools. It is only perceptible in the first 20 m and its mean amplitude is about 5 m. This amplitude is inversely proportional to the initial school depth. Such a limited amplitude allows one to estimate that the fish tilt angle is less than 10" when the school is overpassed. Therefore, the underestimation of density due to vertical avoidance is probably low. This estimation of tilt angle was made under the assumption that the lateral avoidance just under the boat was negligible: the propeller noise in front of a vessel is attenuated by the hull and the resulting funnel-shaped acoustic shadow should be responsible for the limited lateral avoidance reaction observed when the fish previously located on the vessel route are overpassed.
The effects of disturbances from recreational activities on the swimming speed and habitat use of roach Rutilus rutilus, perch Perca fluviatilis and pike Esox lucius were explored. Disturbances were applied for 4 h as (1) boating in short intervals with a small outboard internal combustion engine or (2) boating in short intervals combined with angling with artificial lures between engine runs. The response of the fish species was evaluated by high-resolution tracking using an automatic acoustic telemetry system and transmitters with sub-minute burst rates. Rutilus rutilus swimming speed was significantly higher during disturbances [both (1) and (2)] with an immediate reaction shortly after the engine started. Perca fluviatilis displayed increased swimming activity during the first hour of disturbance but not during the following hours. Swimming activity of E. lucius was not significantly different between disturbance periods and the same periods on days without disturbance (control). Rutilus rutilus increased their use of the central part of the lake during disturbances, whereas no habitat change was observed in P. fluviatilis and E. lucius. No difference in fish response was detected between the two types of disturbances (boating with and without angling), indicating that boating was the primary source of disturbance. This study highlights species-specific responses to recreational boating and may have implications for management of human recreational activities in lakes.
In many fisheries, some component of the catch is usually released. Quantifying the
effects of capture and release on fish survival is critical for determining which practices are sustainable,
particularly for threatened species. Using a standardized fishing technique, we studied
sublethal (blood physiology and reflex impairment assessment) and lethal (post-release mortality
with satellite tags) outcomes of fishing stress on 5 species of coastal sharks (great hammerhead,
bull, blacktip, lemon, and tiger). Species-specific differences were detected in whole blood
lactate, partial pressure of carbon dioxide, and pH values, with lactate emerging as the sole
parameter to be significantly affected by increasing hooking duration and shark size. Species-specific
differences in reflex impairment were also found; however, we did not detect any significant
relationships between reflex impairment and hooking duration. Taken together, we ranked each
species according to degree of stress response, from most to least disturbed, as follows: hammerhead
shark > blacktip shark > bull shark > lemon shark > tiger shark. Satellite tagging data
revealed that nearly 100% of all tracked tiger sharks reported for at least 4 wk after release, which
was significantly higher than bull (74.1%) and great hammerhead (53.6%) sharks. We discuss
which mechanisms may lead to species-specific differences in sensitivity to fishing and suggest
that observed variation in responses may be influenced by ecological and evolutionary phenomena.
Moreover, our results show that certain species (i.e. hammerhead sharks in this study) are
inherently vulnerable to capture stress and mortality resulting from fisheries interactions and
should receive additional attention in future conservation strategies.