Craig A Radford

University of Auckland · Institute of Marine Science

The relationship between habitat and behaviour provides important information for species management. For large, free roaming, marine animals satellite tags provide high resolution information on movement, but such datasets are restricted due to cost. Extracting additional biologically important information from these data would increase utilisatio...

Behavioural studies have shown that sharks are capable of directional orientation to sound. However, only one previous experiment addressed the physiological mechanisms of directional hearing in sharks. In this study we used a directional shaker table in combination with the auditory evoked potential (AEP) technique to understand the broadscale dir...

Fishes, including elasmobranchs (sharks, rays, and skates), present an astonishing diversity in inner ear morphologies; however, the functional significance of these variations and how they confer auditory capacity is yet to be resolved. The relationship between inner ear structure and hearing performance is unclear, partly because most of the morp...

Considerable diversity has been documented in most sensory systems of elasmobranchs (sharks, rays, and skates); however, relatively little is known about morphological variation in the auditory system of these fishes. Using magnetic resonance imaging (MRI), the inner ear structures of 26 elasmobranchs were assessed in situ. The inner ear end organs...

Auditory sensitivity measurements have been published for only 12 of the more than 1,150 extant species of elasmobranchs (sharks, skates, and rays). As a result, there is the need to further understand sound perception in more species from different ecological niches. In this study the auditory evoked potential (AEP) technique was used to compare h...

Sharks (elasmobranchs) are an ancient, diverse group of fishes, representing a basal stage in the evolution of vertebrate hearing. Yet, our understanding of behavioural measures of hearing abilities in sharks is limited. To address this, an operant conditioning paradigm was designed, and scalloped hammerhead Sphyrna lewini and rig (spotted estuary...

The sensory systems of crustaceans (aquatic decapods and stomatopods) have adapted to a diverse range of aquatic ecosystems. Sound production in aquatic crustaceans is more widespread than previously thought, and has been shown to play a major role in many of their life-history strategies; however, there are still many gaps in our understanding of...

Anthropogenic stressors, such as plastics and fishing, are putting coastal habitats under immense pressure. However, sound pollution from small boats has received little attention given the importance of sound in the various life history strategies of many marine animals. By combining passive acoustic monitoring, propagation modelling, and hearing...

Introduction The inner ear hair cells of fishes can provide insight into the early evolution of vertebrate inner ear structure. Fishes represent some of the first vertebrates to evolve auditory capacity, and the same basic structure, the sensory hair cell, provides the fundament for auditory and vestibular function in jawed vertebrates. Despite hol...

Small recreational boats are an omnipresent source of sound pollution in shallow coastal habitats, which can impact the behavior and physiology of a wide array of taxa. However, effective monitoring of this stressor is currently limited by a lack of tools. The present study coupled passive acoustic monitoring (PAM) with timelapse imagery to provide...

Knowledge of the three-dimensional movement patterns of elasmobranchs is vital to understand their ecological roles and exposure to anthropogenic pressures. To date, comparative studies among species at global scales have mostly focused on horizontal movements. Our study addresses the knowledge gap of vertical movements by compiling the first globa...

Studies on the auditory system of fishes can provide fundamental information about the early evolution of vertebrate hearing. While there are limited data available on the auditory system of bony fishes, comparatively far less is known about auditory structures in elasmobranchs, despite their critical basal position within vertebrate evolution. Spe...

The blue shark Prionace glauca is the most abundant, widely distributed and exploited pelagic shark species. Its population is declining in almost all major oceanic basins. Population management and conservation efforts have traditionally depended on fishery bycatch and observer data. Recent studies correlating animal distribution derived from sate...

Sharks represent the earliest group of jawed vertebrates and as such, they may provide original insight for understanding the evolution of sleep in more derived animals. Unfortunately, beyond a single behavioural investigation, very little is known about sleep in these ancient predators. As such, recordings of physiological indicators of sleep in s...

Aquatic environments encompass the world’s most extensive habitats, rich with sounds produced by a diversity of animals. Passive acoustic monitoring (PAM) is an increasingly accessible remote sensing technology that uses hydrophones to listen to the underwater world and represents an unprecedented, non-invasive method to monitor underwater environm...

Sound from small recreational boats spans a wide range of frequencies and source levels, but the degree to which this impacts the soundscapes of shallow coastal habitats is poorly understood. Here, long-term passive acoustic recordings at five shallow coastal sites, including two MPAs, were used to quantify spatio-temporal variation in small boat s...

Sound perception and detection in decapod crustaceans is surprisingly poorly understood, even though there is mounting evidence for sound playing a critical role in many life history strategies. The suspected primary organ of sound perception are the paired statocysts at the base of the first antennal segment. To better understand the comparative s...

Studies that use CO2 vents as natural laboratories to investigate the impacts of ocean acidification (OA) typically employ control-impact designs or local-scale gradients in pH or pCO2, where impacted sites are compared to reference sites. While these strategies can accurately represent well-defined and stable vent systems in relatively homogenous...

Many crustaceans produce sounds that might be used in communication. However, little is known about sound detection in crustaceans, hindering our understanding of crustacean acoustic communication. Sound detection has been determined only for a few species, and for many species, it is unclear how sound is perceived: as particle motion or sound pres...

The settlement phase of crustaceans is critical and can ultimately affect their population structure. Underwater sound has been proposed as one of the most important sensory cues used by these animals during this phase because it can provide direction and habitat quality information. Here, we evaluated the effect of different acoustic signals (biol...

From midnight of 26 March 2020, New Zealand became one of the first countries to enter a strict lockdown to combat the spread of COVID‐19. The lockdown banned all non‐essential services and travel both on land and sea. Overnight, the country’s busiest coastal waterway, the Hauraki Gulf Marine Park, became devoid of almost all recreational and non‐e...

The global lockdown to mitigate COVID-19 pandemic health risks has altered human interactions with nature. Here, we report immediate impacts of changes in human activities on wildlife and environmental threats during the early lockdown months of 2020, based on 877 qualitative reports and 332 quantitative assessments from 89 different studies. Hundr...

Behavioural patterns and distributions of crustaceans, fish and mammals can be inferred from acoustic recordings of the extremely noisy marine acoustic environment. In this study, we determined the soundscape of protected and non-protected marine areas between January and April 2016. Sonobuoy (a device for sound monitoring) recordings began at suns...

Baleen whales reliably produce stereotyped vocalizations, enabling their spatio-temporal distributions to be inferred from acoustic detections. Soundscape analysis provides an integrated approach whereby vocal species, such as baleen whales, are sampled holistically with other acoustic contributors to their environment. Acoustic elements that occur...

Humans are rapidly changing the marine environment through a multitude of effects, including increased greenhouse gas emissions resulting in warmer and acidified oceans. Elevated CO2 conditions can cause sensory deficits and altered behaviours in marine organisms, either directly by affecting end organ sensitivity or due to likely alterations in br...

An anthropogenic cacophony Sound travels faster and farther in water than in air. Over evolutionary time, many marine organisms have come to rely on sound production, transmission, and reception for key aspects of their lives. These important behaviors are threatened by an increasing cacophony in the marine environment as human-produced sounds have...

Effective management of wild animal populations relies on an understanding of their spatio-temporal distributions. Passive acoustic monitoring (PAM) is a non-invasive method to investigate the distribution of free-ranging species that reliably produce sound. Critically endangered Antarctic blue whales (Balaenoptera musculus intermedia) (ABWs) co-oc...

Ecosystems and the communities they support are changing at alarmingly rapid rates. Tracking species diversity is vital to managing these stressed habitats. Yet, quantifying and monitoring biodiversity is often challenging, especially in ocean habitats. Given that many animals make sounds, these cues travel efficiently under water, and emerging tec...

Sleep is known to occur in most, if not all, animals studied thus far. Recent studies demonstrate the presence of sleep in flatworms and jellyfish, suggesting that this behaviour evolved early in the evolution of animals. Sharks are the earliest known extant, jawed vertebrates and may play an important role in understanding the evolutionary history...

Sharks are an interesting group of vertebrates, as many species swim continuously to “ram” oxygen-rich seawater over their gills (ram ventilators), whereas other species “pump” seawater over their gills by manipulating buccal cavity volume while remaining motionless (buccal pumpers). This difference in respiratory physiology raises the question: Wh...

Research into the effects of soundscapes on aquaculture species in key production systems is sparse, despite potential impacts of sound on animal welfare and commercial yields. In the following study, 2 high-value global aquaculture species, whiteleg shrimp Litopenaeus vannamei and Atlantic salmon Salmo salar, were exposed to aquaculture production...

Both the lateral line and the inner ear contribute to near-field dipole source detection in fish. The precise roles these two sensory modalities provide in extracting information about the flow field remain of interest. In this study, evoked potentials (EP, 30–200 Hz) for blind Mexican cavefish were measured in response to a dipole source. Greatest...

Despite growing evidence that crustaceans produce and detect sounds, the behavioural and biological function of these sounds is still poorly understood. Here, we describe sounds produced by the New Zealand paddle crab, Ovalipes catharus, and provide evidence of intraspecific communication using underwater sound. Acoustic and video analyses of tank-...

Offshore activities elevate ambient sound levels at sea, which may affect marine fauna. We reviewed the literature about impact of airgun acoustic exposure on fish in terms of damage, disturbance and detection and explored the nature of impact assessment at population level. We provided a conceptual framework for how to address this interdisciplina...

Studies on the behavioural function of sounds are very rare within heterospecific interactions. John Dory (Zeus faber) is a solitary, predatory fish that produces sound when captured, but has not been documented to vocalize under natural conditions (i.e. in the wild). The present study provides the first in-situ recordings of John Dory vocalisation...

Male oyster toadfish (Opsanus tau) acoustically attract females to nesting sites using a boatwhistle call. The rapid speed of sound underwater combined with the close proximity of the otolithic organs makes inner ear interaural time differences an unlikely mechanism to localize sound. To determine the role that the mechanosensory lateral line may p...

All fish can detect the three vector components of particle motion, enabling them to determine source bearing, but particle motion alone cannot resolve which direction is towards the source and which direction is away (i.e., there is a 180° ambiguity). However, fish with swim bladders can also detect acoustic pressure which enables such fish to res...

Biodiversity across the animal kingdom is reflected in acoustic diversity, and the evolution of these signals is driven by the ability to produce and hear sounds within the complex nature of soundscapes. Signals from the sender are attenuated and their structure is changed during propagation to receivers, and other sounds contributing to the sounds...

Human‐generated sound affects hearing, movement, and communication in both aquatic and terrestrial animals, but direct natural underwater behavioral observations are lacking. Baited underwater video (BUV) were deployed in near shore waters adjacent to Goat Island in the Cape Rodney–Okakari Point Marine Reserve (protected) or outside the reserve app...

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 effec...

Sound in aquaculture production systems remains poorly understood in terms of both biological effects and engineering possibilities. Open systems such as net pens and traditional ponds are increasingly being complemented by recirculating aquaculture systems (RAS). Each of these systems create soundscapes, which may have a significant effect on the...

The Hauraki Gulf, a shallow embayment in north-eastern New Zealand, provides an interesting environment for ecological soundscape research. It is situated on a tectonic plate boundary, contains one of the busiest ports in the southern hemisphere and is home to a diverse range of soniferous animals. The underwater soundscape was monitored for spatia...

Anthropogenic noise across the world's oceans threatens the ability of vocalising marine species to communicate. Some species vocalise 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 investigate the risk of these impacts, we investigated the...

Approximately half of the world’s cetacean species are known to occur in New Zealand waters, yet little is known about their seasonal distribution and abundance. Passive acoustic monitoring provides a non-invasive method of monitoring vocal marine mammal species over larger spatial and temporal scales than visual surveys. In June 2016, New Zealand’...

Increasing sound in the ocean from human activity potentially threatens marine animals that use sound to communicate, detect prey, avoid predators and function within their ecosystem. The detection and classification of sound produced by marine animals, such as whales and fish, is an important component in noise mitigation strategies, while also pr...

The marine environment is the planet’s largest, yet in many respects the least accessible. Our human sensory repertoire, with its emphasis on vision and air-adapted hearing, does not serve us well underwater. Underwater vision is often limited and as divers we find hearing of little, or no, use. Yet we know from the physics that underwater sound ha...

Diversity measurement techniques can present logistical and financial obstacles to conservation efforts. Ecoacoustics has recently emerged as a promising solution to these issues, providing a mechanism for measuring diversity using acoustic indices, which have proven to be beneficial in terrestrial habitats. During summer in temperate north eastern...

Human generated noise affects hearing, movement and communication in both aquatic and terrestrial animals, but direct natural underwater behavioral observations are lacking. Baited underwater video (BUV) equipped with hydrophones were deployed inside and outside a marine reserve to observe fish behavior during motorboat transits. BUVs were effectiv...

A feeding ‘work-up’ is a multi-species aggregation involving dolphins, diving gannets and whales feeding on schooling bait fish. The hypothesis is that sounds produced during a ‘work-up’, which can potentially be heard a significant distance away, provide key cues of food availability. Using drifting hydrophones feeding ‘work-ups’ were recorded thr...

For over 50 years, the mechanism and even existence of crustacean hearing has been debated. The lack of convincing evidence how crustaceans hear is underwhelming given the tremendous advancements made in our understanding of crustacean behavior that clearly shows crustaceans produce sounds and can respond to acoustic cues. We hypothesize that the c...

A critical concern with respect to marine animal acoustics is the issue of hearing “sensitivity,” as it is widely used as a criterion for the onset of noise-induced effects. Important aspects of research on sensitivity to sound by marine animals include: uncertainties regarding how well these species detect and respond to different sounds; the mask...

With underwater sound levels rising due to increasing vessel activity, there is a pressing need to better understand the potential distances for which masking impacts on acoustically sensitive marine life may occur, especially in embayments with shipping activity. Given the known detrimental noise impacts on the marine environment, managing underwa...

Fish vocalisation is often a major component of underwater soundscapes. Therefore, interpretation of these soundscapes requires an understanding of the vocalisation characteristics of common soniferous fish species. This study of captive female bluefin gurnard, Chelidonichthys kumu, aims to formally characterise their vocalisation sounds and daily...

Soundscapes provide a new tool for the study of fish communities. Bigeyes (Pempheris adspersa) are nocturnal planktivorous reef fish, feed in loose shoals and are soniferous. These vocalisations have been suggested to be contact calls to maintain group cohesion, however direct evidence for this is absent, despite the fact that contact calls are wel...

Examination of fish responses to sound stimuli has a rich and varied history but it is not always clear when responses are true measures of hearing or the lateral-line. The central innervation of auditory and lateral-line sensory afferents lie in close proximity in the brainstem and both sets of receptors are, at heart, hair cell-based particle mot...

Diversity measurement techniques can present logistical and financial obstacles to conservation efforts. Ecoacoustics has recently emerged as a promising solution to these issues, providing a mechanism for measuring diversity using acoustic indices, which have proven to be beneficial in terrestrial habitats. This study investigates the application...

The development of marine tidal turbines has advanced at a rapid rate over the last decade but with little detailed understanding of the potential noise impacts on invertebrates. Previous research has shown that underwater reef noise plays an important role in mediating metamorphosis in many larval crabs and fishes. New research suggests that under...

The top predators in coastal marine ecosystems, such as whales, dolphins, seabirds, and large predatory fishes (including sharks), may compete with each other to exploit food aggregations. Finding these patchy food sources and being first to a food patch could provide a significant competitive advantage. Our hypothesis is that food patches have spe...

With considerable commercial interest in renewable energy production in estuarine environments, there is a critical need to better understand ambient sound from these habitats. This study investigated the ambient sound from two sites of differing habitats within the Kaipara Harbour, a site previously allocated for tidal turbine development. Analyse...

Acoustic landscapes, or soundscapes, can vary due to biological (‘biophony’), geophysical (‘geophony’) and anthropogenic (‘anthrophony’) components, and in some environments, such as many coral reefs, biophony dominates the soundscape. We compared 126 sound recordings from 3 different times of day (day, dusk and night) at 42 locations with concurre...

Fish sounds are an important biological component of the underwater soundscape. Understanding species-specific sounds and their associated behaviour is critical to determine how animals use the biological component of the soundscape. Using both field and laboratory experiments we describe the sound production of a nocturnal planktivore, Pempheris a...

ABSTRACT: The underwater sound generated by the organisms on a reef has been shown to provide an important orientation cue for a wide range of larval, juvenile and adult marine organisms. There is some preliminary evidence that some organisms can discriminate among different benthic habitats using sound cues over relatively short spatial ranges (i....

Snapper (Chrysophrys auratus) is an important coastal fish species in New Zealand for a variety of reasons, but the large amount of research conducted on snapper has not been reviewed. Here, we review life history information and potential threats for snapper in New Zealand. We present information on snapper life history, defining stages (eggs and...

Snapper (Chrysophrys auratus) is an important coastal fish species in New Zealand for a variety of reasons, but the large amount of research conducted on snapper has not been reviewed. Here, we review life history information and potential threats for snapper in New Zealand. We present information on snapper life history, defining stages (eggs and...

In the underwater environment, sound propagates both as a pressure wave and particle motion, with particle motions dominating close to the source. At the receptor level, the fish ear and the neuromast hair cells act as displacement detectors, and both are potentially stimulated by the particle motion component of sound. The encoding of the anterior...

In the face of accelerated climate change, monitoring biodiversity has become acritical task for ecologists. Habitat loss is occurring at an alarming rate both in terrestrial and marine ecosystems, resulting in endangerment and extinction of species up to 1,000 times faster than natural rates. However, traditional biodiversity measurements are logi...

Underwater anthropogenic sound levels in the ocean are increasing, and the evidence for impacts of sound on marine life is overwhelming. Currently, regulatory bodies require emitted sound from marine renewable energy projects to be assessed in order to infer potential impacts on marine life. Geometric spreading models are sometimes used to assess l...

The purpose of this paper is to highlight the contributions of the Leigh Marine Laboratory to sensory neuroethology. A brief summary of the work done at Leigh, or by Leigh staff, is given across each of the main sensory modalities: chemosense, vision and octavolateralis sensory systems (electrosense, flow sensing and hearing). Within this broad ove...

The New Zealand bigeye, Pempheris adspersa, is a nocturnal planktivore and has recently been found to be an active sound producer. The rostral end of the swim bladder lies adjacent to Baudelot's ligament which spans between the bulla and the cleithrum bone of the pectoral girdle. The aim of this study was to use the auditory evoked potential techni...

Swim bladder extensions and hearing ability were examined in the temperate reef fish Polyprion oxygeneios (hapuka). Using the auditory evoked potential (AEP) technique, hearing thresholds were determined in four age-classes of hapuka, from larvae to juveniles. The youngest age-class had poor hearing abilities, with lowest thresholds of 132 dB re 1...