First documented occurrences of the shortnose sturgeon (Acipenser brevirostrum,Lesueur, 1818) in the Saco River,Maine, USA

During sampling efforts to study the more abundant Atlantic sturgeon, Acipenser oxyrinchus oxyrinchus, between May of 2009 and November of 2011, four shortnose sturgeon were captured in gill nets near the mouth of the Saco River, Maine. Two of these individuals were tagged with acoustic transmitters to monitor their movement within the Saco River. Additionally, six shortnose sturgeon that had been tagged with acoustic transmitters in the Merrimack River, Massachusetts were detected on the acoustic array deployed within the Saco River and its estuary over this time period. These incidences represent the first verified documentation of shortnose sturgeon within this estuary.     

Taking the bait: in situ voluntary ingestion of acoustic transmitters by Atlantic cod (Gadus morhua)

Voluntary ingestion of acoustic transmitters by Atlantic cod (Gadus morhua) was investigated under field conditions in the shallow inshore waters off Newfoundland. A surface-controlled tagging frame was used to suspend and monitor baited transmitters (16×45 mm up to 16×108 mm) near the seafloor at depths ranging from 12.5 to 39.0 m. The behaviour of cod toward the transmitters was quantified using an underwater video camera. Cod ranging in size from 11 to 92 cm approached and touched the transmitters. Both biting and ingestion were size-dependent. Eight successful taggings were completed with cod ranging in size from 34 to 92 cm. Transmitters deployed in the morning were consumed faster (mean soak time = 3.3 h) than transmitters deployed in the afternoon (mean soak time = 9.1 h). Tracking revealed that cod were active immediately following tagging, suggesting no effect of the tagging procedure. Individual fish were tracked for periods ranging from 5.6 to 18.8 d, with none of the fish regurgitating transmitters during the period for which they were tracked.     

Aggregating behaviour,social interactions and possible spawning in the deep‐water fish Coryphaenoides rupestris

A dense aggregation of the roundnose grenadier Coryphaenoides rupestris was observed with a towed camera at a depth of 1500 m in the Rockall Trough during September. The density of fish was 100 times greater than other sites. Within the aggregation the fish showed directional alignment, rapid swimming actions, mid‐water swimming and social interactions similar to those associated with spawning in other Gadiformes.     

A wireless communication system for determining site fidelity of juvenile dusky groupers Epinephelus marginatus (Lowe, 1834) using coded acoustic transmitters

The value of marine reserves to protect threatened and vulnerable species, such as the dusky grouper (Epinephelus marginatus), is often uncertain because of a lack of knowledge about their ecology and habitat utilisation. To address this issue, a Wireless Communication System for location-based positioning of fish tagged with coded acoustic transmitters was installed to determine site fidelity of juvenile dusky groupers (mean total length = 30.4 cm, range: 20.5–40.0 cm; mean total weight = 470 g, range: 113–950 g) within a marine reserve (Island of Ustica, Sicily, Italy). The system was based on five wireless hydrophones distributed approximately 200 m apart along the coastline of the reserve, each monitoring acoustic signals from transmitters within a reception cell. The hydrophones retransmitted detected signals as a radio signal to a land-based receiver and data logger. Unique identifiers for each hydrophone permitted the identification of the detection cell containing the tagged fish. The wireless hydrophones had partly overlapping detection ranges, dividing the marine reserve into more than five different detection cells. The average detection range was 232 m, but coverage varied from site to site and with time, depending on many factors, such as ambient noise, wave action and signal strength of the transmitters. Despite some limitations, the Wireless Hydrophone System (WHS) combined with manual tracking provided a valuable tool for investigating site fidelity in the dusky grouper. Preliminary home ranges for the fish were estimated by the kernel method (probability level of 95%), based on a limited set of manual tracking data, to be a median 5312 m² (range 1673–18626 m²).     

Diurnal patterns in the spatial relationships between saithe, Pollachius virens, schooling in the wild

Six saithe, length 35 to 43 cm, were tagged with acoustic transmitters and individuals tracked for between 9 and 508 h during May 1989. The tagged fish were members of a schooling group and during the study, pairs of tagged fish were tracked simultaneously for periods ranging from 9 to 139 h. These data have been used to investigate the spatial relationships between individuals schooling in the wild. Distances between individuals showed a distinct diel pattern. Tagged fish were generally closer together during the day, than either at night or the periods of dawn and dusk. Those circumstances under which pairs of tagged fish could be shown to school together were investigated by analysing the differences in their swimming directions. Schooling was generally evident during the hours of daylight, although the degree to which fish schooled varied between pairs. The degree to which the fish schooled was also dependent upon distance between the tagged individuals. Schooling could be demonstrated for saithe within 20 m of each other during the day and within 10 m in two out of three pairs at night.     

Novel Acoustic Technology for Studying Free-Ranging Shark Social Behaviour by Recording Individuals' Interactions

Group behaviours are widespread among fish but comparatively little is known about the interactions between free-ranging individuals and how these might change across different spatio-temporal scales. This is largely due to the difficulty of observing wild fish groups directly underwater over long enough time periods to quantify group structure and individual associations. Here we describe the use of a novel technology, an animal-borne acoustic proximity receiver that records close-spatial associations between free-ranging fish by detection of acoustic signals emitted from transmitters on other individuals. Validation trials, held within enclosures in the natural environment, on juvenile lemon sharks Negaprion brevirostris fitted with external receivers and transmitters, showed receivers logged interactions between individuals regularly when sharks were within 4 m (∼4 body lengths) of each other, but rarely when at 10 m distance. A field trial lasting 17 days with 5 juvenile lemon sharks implanted with proximity receivers showed one receiver successfully recorded association data, demonstrating this shark associated with 9 other juvenile lemon sharks on 128 occasions. This study describes the use of acoustic underwater proximity receivers to quantify interactions among wild sharks, setting the scene for new advances in understanding the social behaviours of marine animals.     

Randomization Analyses: Mimicry, Geographic Variation and Cultural Evolution of Song in Brood-Parasitic Straw-Tailed Whydahs, Vidua fischeri

Although bird song has been an important model for investigating questions of behavior development, cultural evolution and population differentiation, the quantitative methods of analysis have been problematic. Here we develop and apply quantitative randomization methods to test hypotheses about these processes in a natural population of birds. Songs of the African brood-parasitic straw-tailed whydahs ( Vidua fischeri ) and songs of their host species, the purple grenadier ( Granatina ianthinogaster ), were compared in audiospectrograms for similarity to test the following hypotheses: Whydahs mimic the songs of their host species, they have local song dialects, neighboring males match their song themes, local males match the songs of local hosts, remote populations have different songs according to their geographic distance, and songs undergo cultural evolution over time across generations. Randomization analyses were completed using (1) Mantel matrix statistics and (2) tree-based measures employing Sankoff optimization of Manhattan matrices and approximate randomizations. Our results provide evidence for song mimicry, local song dialects, matching song themes between neighboring males, song matching of local whydah mimics and grenadier song models, correspondence of song differences and geographic distance, and cultural continuity with change in song traditions within a local population. These randomization methods may be useful in other studies of animal communication, and they are sufficiently general for use both with distance matrices derived either from naturalistic impressions of song similarity as in our example or from acoustic measurements.     

The Role of Carrion Supply in the Abundance of Deep-Water Fish off California

Few time series of deep-sea systems exist from which the factors affecting abyssal fish populations can be evaluated. Previous analysis showed an increase in grenadier abundance, in the eastern North Pacific, which lagged epibenthic megafaunal abundance, mostly echinoderms, by 9–20 months. Subsequent diet studies suggested that carrion is the grenadier''s most important food. Our goal was to evaluate if changes in carrion supply might drive the temporal changes in grenadier abundance. We analyzed a unique 17 year time series of abyssal grenadier abundance and size, collected at Station M (4100 m, 220 km offshore of Pt. Conception, California), and reaffirmed the increase in abundance and also showed an increase in mean size resulting in a ∼6 fold change in grenadier biomass. We compared this data with abundance estimates for surface living nekton (pacific hake and jack mackerel) eaten by the grenadiers as carrion. A significant positive correlation between Pacific hake (but not jack mackerel) and grenadiers was found. Hake seasonally migrate to the waters offshore of California to spawn. They are the most abundant nekton species in the region and the target of the largest commercial fishery off the west coast. The correlation to grenadier abundance was strongest when using hake abundance metrics from the area within 100 nmi of Station M. No significant correlation between grenadier abundance and hake biomass for the entire California current region was found. Given the results and grenadier longevity, migration is likely responsible for the results and the location of hake spawning probably is more important than the size of the spawning stock in understanding the dynamics of abyssal grenadier populations. Our results suggest that some abyssal fishes'' population dynamics are controlled by the flux of large particles of carrion. Climate and fishing pressures affecting epipelagic fish stocks could readily modulate deep-sea fish dynamics.     

Population structure, growth and reproduction of roughhead grenadier on the Flemish Cap and Flemish Pass

Roughhead grenadier Macrourus berglax were collected during the Flemish Cap bottom survey (1991–2001, NAFO division 3M, depth of 200–720 m) and on commercial vessels (1998–2000, NAFO divisions 3L, M and N, depth of 700–1700 m). The abundance of roughhead grenadier, as well as their average size, increased with depth. Age and length composition of the catches showed clear differences between the sexes. The proportion of males in the catch declined in the larger length classes and there were no males in the largest length classes (25 cm). There were differences in the growth trajectories of the two sexes; both sexes grew similarly up to 9 years, but the male growth was slower thereafter. The pre-anal fin length at first maturity ( L _PA50) for roughhead grenadier females was 28·5 cm, whilst the age at 50% maturity was 15–16 years. Individual total fecundity varied between 8522 and 61 844 oocytes. Macrourus berglax had a prolonged life cycle and multi-aged population structure, with differences in growth and mortality between males and females, slow maturation and low fecundity.     

Walking speed and area utilization of red king crab (<Emphasis Type="Italic">Paralithodes camtschaticus</Emphasis>) introduced to the Barents Sea coastal ecosystem

The red king crab (Paralithodes camtschaticus) was introduced in the Barents Sea in the 1960s and soon established a viable population. Proper management and exploitation of the Barents Sea king crab stock require better understanding of the spatial dynamics at different scales. This study examines the small-scale movement patterns of seven adult male crabs tracked for a period of up to one month from mid July to mid August at 150 m depth in a semi-enclosed fjord on the Russo-Norwegian border. The crabs were tagged with acoustic transmitters and their movements monitored with an acoustic positioning system. Low walking speeds (<0.01 m s⁻¹) were most frequent but the crabs could move at a maximum speed of 0.15 m s⁻¹ and walk an actual distance of up to 270 m over a period of one hour. However, the crabs usually moved within a relatively restricted area with mean hourly longest rectilinear distance varying from 26 to 64 m. The crabs alternated between periods of low and high activity, which could reflect feeding in and movements between food patches. The lack of a diel activity rhythm may be due to high light levels during the polar summer night, or a chemically mediated food search strategy.     

The secret life of the giant Australian cuttlefish Sepia apama (Cephalopoda): Behaviour and energetics in nature revealed through radio acoustic positioning and telemetry (RAPT)

Sepia apama were tagged with acoustic transmitters and monitored on their native House Reef, Boston Bay, South Australia, with a radio acoustic positioning telemetry (RAPT) system. Cuttlefish were tagged with position-only and intra-mantle jet pressure transmitters. New data analyses were developed to handle problem data that arise with an uneven reef environment. Maximum range for the cuttlefish varied from 90 m to 550 m. Cuttlefish home range was between 5300 m² and 23,700 m². S. apama were found to be diurnal as average distance travelled was higher in the day than at night, and cuttlefish were active for 32 days, but only 18 nights. After the cuttlefish settled into reef crevices, activity spectrum and positioning analysis showed foraging behaviour at only 3.7% per day and 2.1% per night. Cuttlefish were found to spend more than 95% of the day resting, which suggests that their bioenergetics are more akin to those of octopus than of squid. The cuttlefish combination of predator avoidance, efficient foraging and quiescent lifestyle allows energy to be channelled into growth and fulfillment of the live-fast-die-young cephalopod philosophy.     

Performance of remote acoustic receivers within a coral reef habitat: implications for array design

Remote monitoring technologies are increasingly being implemented in the marine environment to better understand the movement patterns of taxa. Coral reefs are no exception. However, there is a paucity of information relating to the performance of acoustic receivers on coral reefs. Our results suggest that the detection performance of acoustic receivers may be significantly impacted by the unique nature of the reef environment. This study assessed the performance of passive acoustic receivers on a typical inner-shelf fringing reef, Orpheus Island, on the Great Barrier Reef, Australia. The detection range and diel performance variability of acoustic receivers was assessed using two parallel lines of 5 VR2W receivers spanning 125?m, deployed on the reef base and reef crest. Two 9-mm acoustic transmitters were moored at opposite ends of each receiver line. The working detection range for receivers was found to be approximately 90?m for the transmitter moored on the reef base and just 60?m for the transmitter moored on the reef crest. However, the detection range on the reef crest increased to 90?m when just the reef crest receivers were considered, highlighting importance of optimal receiver deployment. No diel patterns in receiver performance or detection capacities were detected, suggesting that no corrections are required when interpreting nocturnal versus diurnal activity patterns. We suggest that studies aiming for complete coverage of a site within a reef environment will require receivers in close (<100?m) proximity, and that the placement depth of receivers must be a major consideration, with shallow receivers exhibiting a greater detection range than those on the reef slope. Our results highlight the challenges imposed by coral reefs for acoustic telemetry and the importance of receiver placement for studies conducted within these habitats.     

Estimation of abundance of abyssal demersal fishes; a comparison of data from trawls and baited cameras

The abundance of the macrourid Coryphaenoides (Nematonurus) armatus was investigated using a single warp trawl and baited camera at soundings from 2500 to 5000 m in the north-east Atlantic Ocean. There was no significant relationship between abundance ( n km⁻²) as determined from swept area of the trawl and numbers of fish photographed at standard baits. However, timing of the first arrival ( t _arr s) of the first fish at bait correlated well with the trawl data through the relationship: It is concluded that by measurement of arrival times, the baited camera provides a cost-effective complement to trawl sampling for estimating abundance of deep-water fish including Synaphobranchus kaupi, Anlimora rostratu and C. (N). armatus. However, some abundant species such as the roundnose grenadier Coryphaenoides rupestris were not attracted to baited long-lines or baited cameras and therefore could be sampled only by trawl.     

A preliminary study of the movements of yellow and silver eels, Anguilla japonica, in the estuary of the Fukui River, Japan, as revealed by acoustic tracking

The behavior and movements of yellow and silver phase Japanese eels were observed using acoustic telemetry in the Fukui River estuary and the adjacent waters of Tachibana Bay, Tokushima Prefecture, Japan. The eels were tagged with ultrasonic transmitters and released in the bay, about 300 m from the river mouth in August and November, 1999. All four yellow eels released at the river mouth in August returned to the river. All eels swam further upstream and each stopped at similar locations as the others, which were possibly used as refuges. Each refuge appeared to be a relatively small area (less than 10 m) adjacent to a series of concrete blocks along the shore (100–300 m). These areas were repeatedly utilized by all the yellow eels tracked during the study. The yellow eels spent most of their time in these refuges during daytime and moved predominantly at night. In contrast, a silver eel released in November demonstrated rapid movement towards the sea without stopping after release.     

Conventional tagging and acoustic telemetry of a small surgeonfish, <Emphasis Type="Italic">Zebrasoma flavescens</Emphasis>, in a structurally complex coral reef environment

Passive acoustic telemetry and conventional tag/re-sight techniques were used to study daily movement patterns of adult yellow tang, Zebrasoma flavescens, over a period of months. Range testing and visual observations revealed the limitations of using small acoustic transmitters to monitor movements of small coral reef fish in a topographically complex and noisy coral reef environment. Visual observations of conventionally tagged and albino fish suggest individuals return each day to forage over the same few hundred m² of shallow, turf algae dominated boulder and reef flat habitat for periods of at least weeks to months. Acoustic telemetry data suggest lower frequency of repeated use of daytime foraging, nighttime refuge and sunset spawning sites. However, integration of observation and acoustic telemetry data revealed that many fish were not detected while they were within the empirically tested range of the receivers. These observations indicate that data from passive acoustic telemetry can underestimate the frequency and duration of repeated use of specific areas. Yellow tang adults made daily crepuscular migrations of up to 600 m between foraging and spawning or sheltering sites at consistent times relative to sunset and sunrise. While there was high individual variability in migration distance, almost all individuals moved in the same direction (from south to north) at sunset. This study provided valuable information for evaluating ongoing fishery management efforts using marine protected areas in Hawaii.     

Can acoustic methods be used to monitor grenadier (Macrouridae) abundance in the Ross Sea region?

Grenadiers Macrourus spp. are the main bycatch species in the exploratory longline fishery for toothfish Dissostichus spp. in the Ross Sea, Antarctica. Ongoing monitoring tools are needed to assess stock status of grenadiers in the Ross Sea and to ensure ecological relationships are maintained. There may be potential to use fisheries acoustic methods to obtain estimates of grenadier abundance. Acoustic data collected during New Zealand??s International Polar Year Census of Marine Life survey in February?CMarch 2008 provide evidence that single targets close to the bottom over the Ross Sea slope are grenadiers. The acoustic target strength distribution of single targets was very similar to that predicted based on the measured size range of grenadiers. There are also positive correlations between acoustic backscatter and trawl and longline catches of grenadiers. Key uncertainties of the acoustic method are mark identification away from the bottom, and technical issues with low signal-to-noise ratio at depths greater than 1000 m and the acoustic dead-zone close to the bottom.     

Predicting the factors influencing the inter- and intraspecific survival rates of riverine fishes implanted with acoustic transmitters

Biotelemetry is a central tool for fisheries management, with the implantation of transmitters into animals requiring refined surgical techniques that maximize retention rates and fish welfare. Even following successful surgery, long-term post-release survival rates can vary considerably, although knowledge is limited for many species. The aim here was to investigate the post-tagging survival rates in the wild of two lowland river fish species, common bream Abramis brama and northern pike Esox lucius, following their intra-peritoneal double-tagging with acoustic transmitters and passive integrated transponder (PIT) tags. Survival over a 2-year period was assessed using acoustic transmitter data in Cox proportional hazards models. Post-tagging survival rates were lowest in the reproductive periods of both species, but in bream, fish tagged just prior to spawning actually had the highest subsequent survival rates. Pike survival was influenced by sex, with males generally surviving longer than females. PIT tag detections at fixed stations identified bream that remained active, despite loss of an acoustic transmitter signal. In these instances, loss of the acoustic signal occurred up to 215 days post-tagging and only during late spring or summer, indicating a role of elevated temperature, while PIT detections occurred between 18 and 359 days after the final acoustic detections. Biotelemetry studies must thus always consider the date of tagging as a fundamental component of study designs to avoid tagged fish having premature end points within telemetry studies.     

Reef-Fidelity and Migration of Tiger Sharks,Galeocerdo cuvier,across the Coral Sea

Knowledge of the habitat use and migration patterns of large sharks is important for assessing the effectiveness of large predator Marine Protected Areas (MPAs), vulnerability to fisheries and environmental influences, and management of shark–human interactions. Here we compare movement, reef-fidelity, and ocean migration for tiger sharks, Galeocerdo cuvier, across the Coral Sea, with an emphasis on New Caledonia. Thirty-three tiger sharks (1.54 to 3.9 m total length) were tagged with passive acoustic transmitters and their localised movements monitored on receiver arrays in New Caledonia, the Chesterfield and Lord Howe Islands in the Coral Sea, and the east coast of Queensland, Australia. Satellite tags were also used to determine habitat use and movements among habitats across the Coral Sea. Sub-adults and one male adult tiger shark displayed year-round residency in the Chesterfields with two females tagged in the Chesterfields and detected on the Great Barrier Reef, Australia, after 591 and 842 days respectively. In coastal barrier reefs, tiger sharks were transient at acoustic arrays and each individual demonstrated a unique pattern of occurrence. From 2009 to 2013, fourteen sharks with satellite and acoustic tags undertook wide-ranging movements up to 1114 km across the Coral Sea with eight detected back on acoustic arrays up to 405 days after being tagged. Tiger sharks dove 1136 m and utilised three-dimensional activity spaces averaged at 2360 km³. The Chesterfield Islands appear to be important habitat for sub-adults and adult male tiger sharks. Management strategies need to consider the wide-ranging movements of large (sub-adult and adult) male and female tiger sharks at the individual level, whereas fidelity to specific coastal reefs may be consistent across groups of individuals. Coastal barrier reef MPAs, however, only afford brief protection for large tiger sharks, therefore determining the importance of other oceanic Coral Sea reefs should be a priority for future research.     

The fate of cetacean carcasses in the deep sea: observations on consumption rates and succession of scavenging species in the abyssal north-east Atlantic Ocean

The fate of cetacean carcasses in the deep sea was investigated using autonomous deep-sea lander vehicles incorporating time-lapse camera systems, fish and amphipod traps. Three lander deployments placed cetacean carcasses at depths of 4000 to 4800 m in the north-east Atlantic for periods of 36 h, 152 h and 276 h before being recovered. The photographic sequences revealed that carcasses were rapidly consumed by fish and invertebrate scavengers with removal rates ranging from 0.05 to 0.4 kg h^-1. In the longest experiment the carcass was skeletonized within five days. In each deployment, approximately an hour after emplacement, the grenadier Coryphaenoides (Nematonurus) armatus and large numbers of lysianassid amphipods had arrived at the food-fall. The initially high numbers of grenadiers declined once the majority of the bait had been consumed and a variety of other fish and invertebrates were then observed, some taking up residence at the site. None of the fish species appeared to consume the carcass directly, but preyed upon amphipods instead. Funnel traps recovered with the carcass indicated a succession in the species composition of amphipods, with the specialist necrophages such as Paralicella spp. being replaced by more generalist feeders of the Orchomene species complex.     

Neuroactive substances in the dorsal vagal complex of the medulla oblongata: nucleus of the tractus solitarius,area postrema,and dorsal motor nucleus of the vagus

The distributions of classical and putative neurotransmitters within somata and fibres of the dorsal vagal complex are reviewed. The occurrence within the dorsal medulla oblongata of receptors specific for some of these substances is examined, and possible functional correlations of the specific neurochemicals with respect to their distribution within the dorsal vagal complex are discussed.Many of the known transmitters and putative transmitters are represented in the dorsal vagal complex, particularly within various subnuclei of the nucleus of the solitary tract, the main vagal afferent nucleus. In a few cases, some of these have been examined in detail, particularly with respect to their possible mediation of cardiovascular or gastrointestinal functions. For example, the catecholamines, substance P and angiotensin II in the nucleus of the solitary tract have all been strongly implicated as playing a role in the central control of cardiovascular function. Other neurotransmitters or putative transmitters may be involved as well, but probably to a lesser extent. Similarly, the roles in the dorsal vagal complex of dopamine, the endorphins and cholecystokinin in control of the gut have been studied in some detail.Future investigations of the distributions of and electrophysiological parameters of neurotransmitters at the cellular level should provide much needed clues to advance our knowledge of the correlations between anatomical distributions of specific neurochemicals and physiological functions mediated by them.