Acoustic Transmitters Research Articles

Blacktip shark Carcharhinus limbatus presence at fishing piers in South Carolina: association and environmental drivers.

We tagged 12 Carcharhinus limbatus with acoustic transmitters and monitored their presence at five piers along the north-east coast of South Carolina, USA in 2016 and four piers in 2017 using acoustic receivers. Data were analysed with pier association indices (PAI), mixed models and fast Fourier transformation analyses to identify potential factors related to residence time and presence at piers and any cyclical patterns in visits to piers. While the majority of monitored C. limbatus were infrequently detected at piers, three (25.0%) were highly associated with piers (PAI ≥ 0.50). Of the C. limbatus that were detected after initial capture, three (25.0%) recorded detection events only at the pier where they were tagged and two individuals (16.7%) recorded at least one detection event at all monitored piers. The best-fit model explaining C. limbatus residence time at piers included terms for pier location and diel cycle (wi = 0.88), whereas the best fit model explaining presence-absence of C. limbatus at piers included terms for tidal height, diel cycle, barometric pressure and angler count (wi = 0.98). Carcharhinus limbatus did not appear to display cyclical patterns in their visits to piers. Along the north-east coast of South Carolina, association of C. limbatus with piers is a phenomenon for a proportion of mature individuals, but continued research is necessary to understand if this behaviour is driven by attraction to and feeding on angler discards or increased foraging opportunities resulting from the attraction of potential prey to the physical structure provided by piers.

Numerical simulation of acoustic field in logging-while-drilling borehole generated by linear phased array acoustic transmitter

Numerical simulation of acoustic field in logging-while-drilling borehole generated by linear phased array acoustic transmitter

Immediate physiological and behavioural response from catch-and-release of wild white sturgeon (Acipenser transmontanus Richardson, 1836)

White sturgeon (Acipenser transmontanus) are anadromous and the largest fish occurring in fresh-water habitats in North America. The largest population is found in the lower Fraser River (LFR), British Columbia, Canada where anglers target the species in a catch-and-release (C&R) recreational fishery. Yet, little is known about the consequences of C&R on these wild fish. Sixty-three angled sturgeon had blood samples taken to assess the physiological stress response relative to fight times. Seven sturgeon were also fitted with acoustic transmitters equipped with accelerometer sensors to assess immediate post-release locomotor behaviour. To understand the relationship between accelerometry and fish behaviour, we calibrated the tags in a lab before deploying them in the field. A physiological stress response was apparent (i.e., increased whole-blood lactate and reduced plasma potassium) and was influenced by fight time. Post-release activity profiles showed a general decrease in activity over time. Post-release displacement was 2–75 m from the release site and all 7 sturgeon were relocated closer to shore. The possible preference we identified for nearshore areas after release should be examined in greater detail in the future as this may lend insight into optimal release locations for white sturgeon. Although C&R mortality rates are low for this species, there is some evidence of transient sub-lethal effects emphasizing the need to refine C&R practices to further improve fish welfare.

Magneto-Acoustic Resonator for Aquatic Animal Tracking

Over the past three decades, passive acoustic telemetry has significantly helped marine scientist to study and understand the spatial ecology, migratory behaviors, and mortality rates of aquatic animals. A popular telemetry system consists of two components: an acoustic transmitter tag attached to an aquatic animal and powered by a small battery, and a stationary station that receives the acoustic signals from the tagged animal and determines its location. The added weight and increased size of the tag introduced by the battery limit the implementation of this system to relatively large animals. Moreover, these tags have a limited operational time determined by the lifetime of the battery in combination with the measurement frequency and data resolution and transfer rate. In this paper, a self-powered magneto-acoustic resonator for animal tracking is proposed. It is achieved by utilizing the low-frequency motions of the animals to excite high-frequency acoustic pulses. The measurement results show that the device is capable of producing an average acoustic sound of 55 dB sound pressure level at 1 m of distance with a resonant frequency of 15 kHz.

Movement and predation: a catch-and-release study on the acoustic tracking of bonefish in the Indian Ocean

Tourism generated through bonefish (Albula spp.) fishing contributes to the economies of many isolated tropical islands and atolls. However, little research has been conducted on bonefish in the Indian Ocean. This study aimed to contribute to the understanding of bonefish ecology in the Indian Ocean by quantifying the spatial and temporal movements of Albula glossodonta at a near-pristine and predator-rich atoll in the Seychelles; however, to achieve this, an analysis to identify the occurrence of possible post-release predation bias was first necessary. An acoustic telemetry study was initiated at the remote St. Joseph Atoll, within an array of 88 automated data-logging acoustic receivers. Thirty bonefish were surgically implanted with Vemco V13 acoustic transmitters and tracked for one year. Only 10% of the tagged bonefish were detected for longer than two weeks. A comparison of the final 100 h of movement data from fish detected for less than two weeks to the movement data of the fish detected for longer periods revealed distinct differences in area use and significant differences in the average daily distance moved, speed of movement and frequency of detections. This suggested that mortality in the form of post-release predation was at least 43% of tagged fish. The three surviving bonefish were tracked for 210 to 367 days. These individuals remained in the atoll and showed high use of the marginal habitats between the shallow sand flats and the lagoon. A generalised linear mixed model identified that water temperature, diel cycle and tide were significant predictors of bonefish presence in the lagoon. The high post-release mortality highlights that catch-and-release is likely not as benign as previously believed and management and policy should be adjusted accordingly.

Effects of water temperature on white-spotted conger Conger myriaster activity levels determined by accelerometer transmitters

The effect of water temperature on white-spotted conger activity was examined using acoustic accelerometer transmitters to understand thermal effects on the behavior of a target fishery species. We recorded swimming activities of 21 congers using video cameras and compared the body undulation frequency with acceleration values measured using accelerometer transmitters in the body cavity. We found a significant, positive, linear relationship between the acceleration values and activity (body undulation frequency) of congers. We conducted a calibration trial to evaluate the relationships between conger activities and acceleration values measured using accelerometer transmitters, which confirmed the body undulation frequency of congers was associated with its swimming activity. We also examined the effect of water temperature on conger activity levels. The activity levels of eight congers at water temperatures from 10 to 28 °C were tested using accelerometer transmitters. We found a positive relationship between the conger activity levels and water temperatures between 10 and 26 °C, whereas the activity declined between 26 and 28 °C. These results demonstrate that accelerometer transmitters can quantitatively measure changes in the activity of white-spotted conger with water temperature in nature.

Naturalised Atlantic salmon smolts are more likely to reach the sea than wild smolts in a lowland fjord

AbstractThe survival rates of three groups of seaward‐migrating Salmo salar smolts were investigated in 2005, 2016, and 2017 in the River Skjern and River Omme, as well as in the Ringkøbing Fjord using acoustic telemetry. Ringkøbing Fjord extends for approximately 300 km2, and has a narrow, regulated outlet to the sea. Smolts of three different origins: (a) wild smolts, (b) hatchery‐reared smolts previously released at half‐year‐old, and (c) hatchery‐reared smolts previously released at 1‐year‐old were captured in rotary screw traps and surgically implanted with acoustic transmitters. The progress during seaward migration was monitored with a network of automatic listening stations deployed in the river estuary, fjord mouth and sea opening.The smolts' probability of survival in the river was related to their length, with larger smolts being more likely to reach the fjord. Once in the fjord, the probability of reaching the sea was related with the smolt's group, with smolts previously released at half‐year‐old being more likely to succeed than wild smolts. However, none of the biometric or behavioural variables explained the difference between the studied smolt groups, masking the potential reasons behind this difference in survival probability.Overall, approximately 47% of the tagged smolts were registered at the last array of automatic listening stations (i.e., entered the sea), demonstrating the early migration as a critical bottleneck for the local Atlantic salmon population. Ultimately, this limits the number of Atlantic salmon that survive to adulthood and return to River Skjern and River Omme for spawning.

Movement patterns of an endemic South African sparid, the black musselcracker Cymatoceps nasutus, determined using mark-recapture methods

This study made use of data from three long-term fish tagging projects along the South African coastline to investigate the movement behaviour of the endemic black musselcracker Cymatoceps nasutus (Sparidae). From 1984 to 2016, a total of 3 430 C. nasutus (178–980 mm fork length) were tagged (with small plastic dart tags) throughout the species’ distributional range, with an overall reported recapture rate of 7.2%. Recaptured individuals displayed high levels of residency, moving an average of 14.8 km, with time-at-liberty ranging from 0 to 6 809 days. The majority of recaptures (84.6%) were made within 1 km of the tagging sites; however, some large-scale movements, of up to 528 km, were recorded. Although C. nasutus individuals moving greater distances were characterised by greater mean sizes (mm fork length) at time of recapture, the distances moved by juveniles were not significantly different from those of adults (p > 0.05). Low levels of connectivity among coastal regions were therefore expected due to the high degree of residency displayed by this species. Combining traditional management approaches together with a well-designed network of no-take marine protected areas is likely to be the most effective way to protect this vulnerable species. A lack of data on the movements of adults remains a challenge, but this could be overcome by tracking large individuals tagged with long-life acoustic transmitters.

ACUSQUAT Project: Acoustic behavioural monitoring of the Angelshark (Squatina squatina) in critical conservation areas

Event Abstract Back to Event ACUSQUAT Project: Acoustic behavioural monitoring of the Angelshark (Squatina squatina) in critical conservation areas Diego G. Campos1*, David Jiménez-Alvarado2, José Juan Castro-Hernández2, Airam Guerra-Marrero2, Jorge Cabrera-Gámez2 and Antonio C. Domínguez-Brito2 1 Other, Spain 2 University of Las Palmas de Gran Canaria, Spain The Angelshark (Squatina squatina) is a critically endangered species with a geographic distribution currently reduced to the Canary Islands and with punctual sightings along the Mediterranean and Wales (UK) coasts, primarily due to overfishing. This benthic shark uses sheltered beaches of the islands as reproduction and nursery areas, thus tourism development represents another major threat to its survival. During this study, 11 females and 4 males of Angelshark have been tagged using acoustic transmitters, in order to track their circadian routines and to study their movements around these critical areas, that are also vital for the tourism industry of the Archipelago, particularly during mating season for adults and along the first year of life, when these beaches are used as nursery areas for juveniles. Results, combined with data obtained from visual census and citizen sighting reports, are being used to promote Use and Management Plans in beaches considered as critical conservation areas for the species, and make them compatible with tourism. The tracking methodology has been based on the use of Vemco VR2W, VR2C-Mini and VMT receivers, as well as Vemco V9 coded transmitters. An initial acoustic telemetry network was implemented from October 2018 with 3 fixed receivers (VR2W and VMT) installed on both ends and in the middle part of the study area, and a third receiver (VR2C-Mini) used from a boat to “comb” the area on punctual occasions. The first results show that this kind of tags are very appropriate for tracking benthic elasmobranchs like the Angelshark in restricted coastal areas, with an average detection range of 300-700m depending on the morphology and bathymetry of the area. In the Canary Islands, adults and juveniles are found very close to the shore in beaches and ports that support intense human activity, thus negative interactions are frequent and need to be addressed, particularly with this threatened species. Acknowledgements Fundación Biodiversidad Keywords: Angelshark, acoustic telemetry, critical conservation areas, Tourism development, Canary Islands Conference: XX Iberian Symposium on Marine Biology Studies (SIEBM XX) , Braga, Portugal, 9 Sep - 12 Sep, 2019. Presentation Type: Poster Presentation Topic: Ecology, Biodiversity and Vulnerable Ecosystems Citation: Campos DG, Jiménez-Alvarado D, Castro-Hernández J, Guerra-Marrero A, Cabrera-Gámez J and Domínguez-Brito AC (2019). ACUSQUAT Project: Acoustic behavioural monitoring of the Angelshark (Squatina squatina) in critical conservation areas. Front. Mar. Sci. Conference Abstract: XX Iberian Symposium on Marine Biology Studies (SIEBM XX) . doi: 10.3389/conf.fmars.2019.08.00115 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 27 Jun 2019; Published Online: 27 Sep 2019. * Correspondence: Mx. Diego G Campos, Other, Las Palmas de Gran Canaria, Spain, diego.gamo@fpct.ulpgc.es Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Diego G Campos David Jiménez-Alvarado José Juan Castro-Hernández Airam Guerra-Marrero Jorge Cabrera-Gámez Antonio C Domínguez-Brito Google Diego G Campos David Jiménez-Alvarado José Juan Castro-Hernández Airam Guerra-Marrero Jorge Cabrera-Gámez Antonio C Domínguez-Brito Google Scholar Diego G Campos David Jiménez-Alvarado José Juan Castro-Hernández Airam Guerra-Marrero Jorge Cabrera-Gámez Antonio C Domínguez-Brito PubMed Diego G Campos David Jiménez-Alvarado José Juan Castro-Hernández Airam Guerra-Marrero Jorge Cabrera-Gámez Antonio C Domínguez-Brito Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Flow-related migration, juvenile dispersal and gonad development in two co-occurring mullet species, Mugil cephalus and Trachystoma petardi, in a regulated river system

Catadromous fish species often use elevated flows to migrate from freshwater to downstream spawning grounds. However, in regulated river systems, artificial barriers and flow alteration can disrupt movement cues, affecting fish migration. Using a combination of acoustic telemetry, passive integrated transponder (PIT) tags and gonad maturity data, we assessed the migratory timing and flow requirements for downstream spawning migrations and upstream dispersal in two co-occurring mullet species in the Logan River, eastern Australia. Over 4 years, 141 adult sea mullet (Mugil cephalus) and 28 adult pinkeye mullet (Trachystoma petardi) were implanted with acoustic transmitters and broad-scale movements tracked using an array of 49 acoustic receivers. Juvenile upstream dispersal was monitored using implanted PIT tags and readers deployed in weir fishways. Sea mullet and pinkeye mullet undertook large-scale downstream migrations from February to March. Movements past weirs only occurred once sufficient flow had occurred and, in the case of pinkeye mullet, when gonads were mature. In contrast, juvenile dispersal into upstream habitats occurred primarily between November and April on low flows. This study advances our understanding of bidirectional movement ecology and flow requirements of two co-occurring mullet species to inform environmental flow management (e.g. to facilitate fish passage) in a regulated river system.

Examining movement patterns of yellowtail snapper, Ocyurus chrysurus, in the Dry Tortugas, Florida

Yellowtail snapper, Ocyurus chrysurus (Bloch, 1970), is an important fisheries species in the Florida Keys. In 2008–2009, yellowtail snapper were tagged with acoustic transmitters and tracked through an array of 86 stationary receivers in the Dry Tortugas' network of marine reserves in Florida to determine site fidelity, home range, and temporal patterns of habitat use. Fifteen yellowtail snapper were tracked for 1–427 d [x = 188 (SE 39)]. A multistep method for data validation ensured that only the fish with high-quality detection data were selected for data analyses. Brownian bridge models were used to estimate home range rather than more traditional methods because they incorporate not only detection location, but also time between detections, the path between successive detections, and location error. For a species typically described as transient, six of the tagged yellowtail snapper had high site fidelity [x = 58.4% (SE 8.4%)], and Brownian bridge models estimated relatively small minimum home ranges [x = 5.45 km2 (SE 1.79)]. Movements were highly variable, but analyses showed that fish displayed diel and seasonal trends, and in general, were more likely to be absent during summer months or during dusk and at night. Tagged yellowtail snapper showed a preference for reef edge habitat, swimming in and out of the marine reserve where the boundary intersected this type of habitat. The knowledge that yellowtail snapper is less transient than previously believed and understanding the habitat preference and temporal movements of this species can help with its future management.

Effects of sound exposure from a seismic airgun on heart rate, acceleration and depth use in free-swimming Atlantic cod and saithe.

Airguns used for offshore seismic exploration by the oil and gas industry contribute to globally increasing anthropogenic noise levels in the marine environment. There is concern that the omnidirectional, high intensity sound pulses created by airguns may alter fish physiology and behaviour. A controlled short-term field experiment was performed to investigate the effects of sound exposure from a seismic airgun on the physiology and behaviour of two socioeconomically and ecologically important marine fishes: the Atlantic cod (Gadus morhua) and saithe (Pollachius virens). Biologgers recording heart rate and body temperature and acoustic transmitters recording locomotory activity (i.e. acceleration) and depth were used to monitor free-swimming individuals during experimental sound exposures (18-60dB above ambient). Fish were held in a large sea cage (50m diameter; 25m depth) and exposed to sound exposure trials over a 3-day period. Concurrently, the behaviour of untagged cod and saithe was monitored using video recording. The cod exhibited reduced heart rate (bradycardia) in response to the particle motion component of the sound from the airgun, indicative of an initial flight response. No behavioural startle response to the airgun was observed; both cod and saithe changed both swimming depth and horizontal position more frequently during sound production. The saithe became more dispersed in response to the elevated sound levels. The fish seemed to habituate both physiologically and behaviourally with repeated exposure. In conclusion, the sound exposures induced over the time frames used in this study appear unlikely to be associated with long-term alterations in physiology or behaviour. However, additional research is needed to fully understand the ecological consequences of airgun use in marine ecosystems.

The importance of newly-opened tidal inlets as spawning corridors for adult Red Drum (Sciaenops ocellatus)

The ability to emigrate from estuarine nursery areas to spawning grounds is essential for the persistence of estuarine dependent species such as Red Drum, (Sciaenops ocellatus). Typically in this region, tidal inlets are the only mechanism for this transfer. Cedar Bayou, a natural tidal inlet, was deliberately closed in 1979 but was recently dredged and reopened. The inlet allows for direct water exchange between the Gulf of Mexico and Mesquite Bay, Texas, USA, and represents a unique opportunity to study estuarine dependent species’ migration processes. Adult Red Drum were implanted with acoustic transmitters that allowed us to track their movement patterns before and after the reopening of Cedar Bayou. The goals of this study were to: 1) determine if Red Drum choose migration routes opportunistically in Texas waters; and 2) elucidate general movement patterns and residency estimates for Red Drum in Texas bays. Red Drum showed relatively little movement during the pre-opening period and summer, even after the inlet was restored. Once open, fish actively traversed through Cedar Bayou during the months commonly associated with spawning migrations and coincident with a drop in water temperature. These results demonstrate that Red Drum choose migration corridors opportunistically, thus opening tidal inlets such as Cedar Bayou can provide maturing Red Drum with greater connectivity between estuaries and spawning grounds in the open Gulf of Mexico.

No apparent negative tagging effects after 13 years at liberty for lemon shark, Negaprion brevirostris implanted with acoustic transmitter.

An intact and uncompromised internal acoustic transmitter was non-lethally recovered from a lemon shark Negaprion brevirostris, after 13 years at liberty. The shark, first tagged at an estimated age of 2 years old near South Bimini, Bahamas in 2004, was recaptured in 2017 with a total length of 264 cm. The tagged shark displayed typical growth rate, pregnancy, natal homing and pupping behaviour of other individuals in this population. This observation provides important evidence regarding the effects from long-term retention of implanted acoustic transmitters in a carcharhinid shark.

Getting cosy in freshwater: Assumed to be brackish pike are not so brackish after all

AbstractPike (Esox lucius) occupy coastal streams and rivers of the Baltic Sea, where they attain large sizes (>5 kg). These large sizes are perhaps due to the fact that they can tolerate relatively high salinities and can thus forage in the nearby more productive brackish environments. In an attempt to quantify the extent to which pike utilise brackish environments, and to provide some insight into the underlying causes for brackish water migrations, we tagged 30 pike from a western Baltic river with acoustic transmitters and were able to track 21 individuals for 1 year. Based on experienced from local anglers, this population was assumed to be brackish in nature, where individuals underwent freshwater migrations to spawn. Our findings however suggest that the smallest and most active individuals make short exits into brackish waters and do so on rare occasions. Our results further indicate that neither sex nor size is related to activity level. We suggest that these patterns reflect two distinct behaviours—active and passive—and that large pike can be supported by the food availability in the river, without the need to venture into coastal zones, thus defying the conventional view that Baltic pike are all brackish in nature.

Seasonal aggregation and diel activity by the sicklefin devil ray Mobula tarapacana off a small, equatorial outcrop of the Mid-Atlantic Ridge.

The present study aimed to analyse occurrence patterns, relative abundance and habitat use by the sicklefin devil ray Mobula tarapacana in the Saint Peter and Saint Paul Archipelago (SPSPA), Brazil, located in the Mid-Atlantic Ridge. Sampling was conducted between December 2008 and December 2012 by surface surveys and tagging with conventional tags and acoustic transmitters. Mobula tarapacana were sighted in the SPSPA year round but the highest frequency of occurrence was observed from January to June, probably due to greater food availability during this season. However, M. tarapacana might also use the area for reproductive purposes based on evidence of mating behaviour. The residency period of tagged rays measured by three autonomous acoustic receivers deployed around SPSPA spanned from 1 to 74 days with most of the detections occurring during daytime. These results suggest that the SPSPA could be an ecologically-important aggregation area for M. tarapacana, possibly providing the species with a feeding or resting habitat while transiting in the equatorial Atlantic Ocean.

Non-dimensional analysis of depth, orientation, and alignment in acoustic power transfer systems

Acoustic power transfer systems are typically comprised of an electrical source, acoustic transmitter (TX), medium through which the acoustic waves propagate, acoustic receiver (RX) and an electrical load. The voltage generated across and power delivered to the load from the TX is a function of RX position (depth, orientation, and alignment relative to the TX), frequency, TX and RX diameter, and source and load impedance. In applications where the RX position is not fixed, such as in implantable medical devices, slight disturbances in RX position can result in a severe reduction in load voltage and power. Therefore, the sensitivity of voltage and power as a function of RX position is crucial to system design. This paper presents an analysis of the load voltage and power as a function of RX depth, orientation, alignment, frequency, RX and TX diameter, and load impedance. Design graphs are developed and presented as a means of visualizing the sensitivity of voltage and power to system parameters. Non-dimensional design graphs are then generated to broaden the applicability of simulation results.

The migration of stocked, trapped and transported, and wild female American silver eels through the Gulf of St. Lawrence

The stocking of juvenile eels and trap and transport programs of large yellow (American) eels (Anguilla rostrata) were initiated in Ontario to mitigate mortalities observed at hydroelectric dams and to increase escapement from the upper St. Lawrence River and Lake Ontario (Canada). A total of 380 migrating female silver eels (stocked, trapped and transported, and wild) were tagged with acoustic transmitters between 2011 and 2014. Their migration and escapement at the exit of the Gulf of St. Lawrence, the Cabot Strait, were recorded using acoustic receivers. Escapement rates varied between 8.9% and 20.0% annually (mean = 11.4%). A high proportion of stocked eels were detected (N = 27 of 43 detected at Cabot Strait), demonstrating their ability to escape the Gulf. No differences in migration speed or crossing locations at Cabot Strait were found among the three categories. Eels crossing Cabot Strait did not display diel and tidal patterns, but their estimated swimming depth indicated diel vertical migrations. The low escapement rates observed may be related to predation events and (or) the low and variable detection efficiency of the acoustic receivers’ line.

Long-term implantation of acoustic transmitters induces chronic inflammatory cytokine expression in adult rainbow trout (Oncorhynchus mykiss)

Telemetry transmitters are frequently used in studies of wild fish migration and behavior. Although the effects of surgically implanted transmitters on survival, tag retention, healing and growth have been studied, there has been little research regarding the potential immune response induced by these transmitters. In the current study, mature rainbow trout received either surgical implantation of an acoustic transmitter or a sham surgical procedure. These fish were then sampled over a 10-week period so that pro-inflammatory cytokine expression in the spleen, peritoneal cavity lymphocytes and muscle at the surgical site could be analyzed. There were no significant differences in transcript expression for the spleen and muscle tissue between fish that had a transmitter and those that received the surgical procedure alone. However, transmitter presence significantly increased the expression of IL-6, IL-1β and TNFα in the peritoneal cells at 10 weeks indicating that tagged fish may be coping with chronic inflammation. Furthermore, tagged male fish had a higher inflammatory response in 10-week peritoneal lavage samples when compared to their tagged mature female counterparts, providing some evidence that mature female rainbow trout may have suppressed immune function when sexually mature. Externally, fish appeared to heal at similar rates regardless of the presence or absence of the transmitter, but the tag itself was prone to encapsulation and adhesion to the body wall and/or surgical site. This suggests that fish tagged with large intraperitoneal implants may not behave similarly to their wild counterparts. This research could aid in the development of improved telemetry tags that are more biocompatible, economical and better able to track fish behavior/movement.

Acoustic‐telemetry payload control of an autonomous underwater vehicle for mapping tagged fish

AbstractAutonomous underwater vehicles (AUVs) have demonstrated superior performance for tracking marine animals tagged with individually coded acoustic transmitters. However, AUVs engaged in mapping the distribution of multiple tagged fish have not previously been able to alter search paths to achieve precise position estimates. This problem is solved by the development of payload control software (Synthetic Aperture Override, SAOVR) that allows the AUV to maneuver with trajectories favorable for solving the tag's location from a synthetic aperture. Upon tag detection during a default mission search path, SAOVR (running on an embedded guest computer) seeks permission to take over navigation from the vehicle's native system after checking constraints of geography, timing, tag identification, signal strength, and current navigation state. Permitted maneuvers are then chosen from a template library and executed before returning the AUV to the point of first deviation for continued searching of other tags. Field evaluation on moored reference tags showed a high level of predictability in the AUV's behavior at SAOVR initiation and through maneuvers. Trials suggest that this logic system is highly beneficial to AUV use for fish telemetry in challenging environments such as narrow, deep fjords, or among reefs. Any mission programmed with the AUV's native software can be run with the SAOVR package to allow scientists to easily implement and manipulate synthetic aperture geometries without altering any of the software. Further modeling can help improve template design specific to expected movements of different fish species and relative to the designation of signal strength‐defined execution thresholds.