Explore the vast range of titles available.

Management boundaries that define populations or stocks of fish form the basis of fisheries planning. In the Arctic, decreasing sea ice extent is driving increasing fisheries development, highlighting the need for ecological data to inform management. In Cumberland Sound, southwest Baffin Island, an indigenous community fishery was established in 1987 targeting Greenland halibut (Reinhardtius hippoglossoides) through the ice. Following its development, the Cumberland Sound Management Boundary (CSMB) was designated and a total allowable catch (TAC) assigned to the fishery. The CSMB was based on a sink population of Greenland halibut resident in the northern section of the Sound. Recent fishing activities south of the CSMB, however, raised concerns over fish residency, the effectiveness of the CSMB and the sustainability of the community-based winter fishery. Through acoustic telemetry monitoring at depths between 400 and 1200 m, and environmental and fisheries data, this study examined the movement patterns of Greenland halibut relative to the CSMB, the biotic and abiotic factors driving fish movement and the dynamics of the winter fishery. Greenland halibut undertook clear seasonal movements between the southern and northern regions of the Sound driven by temperature, dissolved oxygen, and sea ice cover with most fish crossing the CSMB on an annual basis. Over the lifespan of the fishery, landfast ice cover initially declined and then became variable, limiting accessibility to favored fisher locations. Concomitantly, catch per unit effort declined, reflecting the effect of changing ice conditions on the location and effort of the fishery. Ultimately, these telemetry data revealed that fishers now target less productive sites outside of their favored areas and, with continued decreases in ice, the winter fishery might cease to exist. In addition, these novel telemetry data revealed that the CSMB is ineffective and led to its relocation to the entrance of the Sound in 2014. The community fishery can now develop an open-water fishery in addition to the winter fishery to exploit the TAC, which will ensure the longevity of the fishery under projected climate-change scenarios. Telemetry shows great promise as a tool for understanding deep-water species and for directly informing fisheries management of these ecosystems that are inherently complex to study.

Acoustic telemetry has emerged as a leading approach to infer diel, tidal and lunar rhythmicity in the movements of aquatic organisms in a range of taxa. Typically, studies examine the relative frequency of detections from individuals tagged with acoustic transmitters, and then infer patterns in the species’ behaviour, but studies to date have not controlled for factors that may influence tag detection patterns in the absence of animal behaviour. We compared patterns in acoustic detections from tagged cuttlefishSepia apamaand several fixed-location control tags, and used these data to highlight the danger of misinterpreting patterns in the absence of adequate controls. Cuttlefish and control tags displayed similar detection patterns, and correcting cuttlefish-detection data for the influence of environmental factors resulted in the opposite pattern of cuttlefish activity displayed prior to correction. This study highlights the danger of using acoustic data to infer animal behaviour in the absence of adequate controls.

Background Acoustic telemetry is increasingly being used as a tool to measure survival, migration timing and behaviour of fish. Tagged fish may fall prey to other animals with the tag continuing to be detected whilst it remains in the gastrointestinal tract of the predator. Failure to identify post-predation detections introduces “predation bias” into the data. We employed a new predator tag technology in the first known field trial to understand the extent these tags could reduce predation bias in Atlantic salmon ( Salmo salar L.) smolt migration through a 65-km zone beginning in freshwater and extending through an estuary. These tags signal predation by detecting a pH change in the predators’ gut during digestion of a tagged prey. We quantified survival and timing bias by comparing measurements from non- and post-predated detections of tagged individuals’ to only those detections where predation was not signalled. Results Of the 50 fish tagged, 41 were detected with 24 of these signalling as predated. Predation bias was greatest in the upper estuary and decreased towards the bay. Survival bias peaked at 11.6% at river km 54. Minimum and maximum migration time were both biased long and were 16% and 4% greater than bias corrected timing at river km 66 and 54, respectively. After correcting for bias, the apparent survival from release through freshwater and estuary was 19% and minimum and maximum migration timing was 6.6 and 7.0 days, respectively. Conclusions Using this tag, we identified a high proportion of predation events that may have otherwise gone unnoticed using conventional acoustic tags. Estimated survival presented the greatest predation bias in the upper estuary which gradually declined to nearly no apparent bias in the lower estuary as predated tags failed through time to be detected. This is most likely due to tag expulsion from the predator between or upstream of receiver arrays. Whilst we have demonstrated that predation can bias telemetry results, it appears to be rather short-lived given the apparent retention times of these tags within the predators introducing the bias.

1. Estimating the metabolic rate of animals in nature is central to understanding the physiological, behavioural and evolutionary ecology of animals. Doubly labelled water and heart-rate methods are the most commonly used approaches, but both have limitations that preclude their application to some systems. 2. Accelerometry has emerged as a powerful tool for estimating energy expenditure in a range of animals, but is yet to be used to estimate field metabolic rate in aquatic taxa. We combined two-dimensional accelerometry and swim-tunnel respirometry to estimate patterns of energy expenditure in giant Australian cuttlefish Sepia apama during breeding. 3. Both oxygen consumption rate () and swimming speed showed strong positive associations with body acceleration, with coefficients of determination comparable to those using similar accelerometers on terrestrial vertebrates. Despite increased activity during the day, field metabolic rate rarely approached , and night-time was similar to that at rest. 4. These results are consistent with the life-history strategy of this species, which has a poor capacity to exercise anaerobically, and a mating strategy that is visually based. With the logistical difficulties associated with observation in aquatic environments, accelerometry is likely to prove a valuable tool for estimating energy expenditure in aquatic animals.

Understanding the nature of inter-specific and conspecific interactions in the ocean is challenging because direct observation is usually impossible. The development of dual transmitter/receivers, Vemco Mobile Transceivers (VMT), and satellite-linked (e.g. GPS) tags provides a unique opportunity to better understand between and within species interactions in space and time. Quantifying the uncertainty associated with detecting a tagged animal, particularly under varying field conditions, is vital for making accurate biological inferences when using VMTs. We evaluated the detection efficiency of VMTs deployed on grey seals, Halichoerus grypus, off Sable Island (NS, Canada) in relation to environmental characteristics and seal behaviour using generalized linear models (GLM) to explore both post-processed detection data and summarized raw VMT data. When considering only post-processed detection data, only about half of expected detections were recorded at best even when two VMT-tagged seals were estimated to be within 50-200 m of one another. At a separation of 400 m, only about 15% of expected detections were recorded. In contrast, when incomplete transmissions from the summarized raw data were also considered, the ratio of complete transmission to complete and incomplete transmissions was about 70% for distances ranging from 50-1000 m, with a minimum of around 40% at 600 m and a maximum of about 85% at 50 m. Distance between seals, wind stress, and depth were the most important predictors of detection efficiency. Access to the raw VMT data allowed us to focus on the physical and environmental factors that limit a transceiver's ability to resolve a transmitter's identity.

Background The successful use of acoustic telemetry to detect fish hinges on understanding the factors that control the acoustic range. The speed-of-sound in water is primarily a function of density, and in freshwater lakes density is primarily driven by temperature. The strong seasonal thermal stratification in the Great Lakes represent some of the steepest sound speed gradients in any aquatic system. Such speed-of-sound gradients can refract sound waves leading to greater divergence of acoustic signal, and hence more rapid attenuation. The changes in sound attenuation change the detection range of a telemetry array and hence influence the ability to monitor fish. We use 3 months of data from a sentinel array of V9 and V16 Vemco acoustic fish tags, and a record of temperature profiles to determine how changes in stratification influence acoustic range in eastern Lake Ontario. Result We interpret data from an acoustic telemetry array in Lake Ontario to show that changes in acoustic detection efficiency and range correlate strongly with changes in sound speed gradients due to thermal stratification. The steepest sound speed gradients of 10.38 m s −1 /m crossing the thermocline occurred in late summer, which caused the sound speed difference between the top and bottom of the water column to be greater than 60 m/s. V9 tags transmitting across the thermocline could have their acoustic range reduced from > 650 m to 350 m, while the more powerful V16 tags had their range reduced from > 650 m to 450 m. In contrast we found that when the acoustic source and receiver were both transmitting below thermocline there was no change in range, even as the strength of sound speed gradient varied. Conclusion Changes in thermal stratification occur routinely in the Great Lakes, on timescales between months and days. The acoustic range can be reduced by as much as 50% compared to unstratified conditions when fish move across the thermocline. We recommend that researchers consider the influences of thermal stratification to acoustic telemetry when configuring receiver position.

The Sargassum spp. inundations across the Atlantic and Caribbean that began in 2011 have continued unabated, and new uses for the biomass are being continuously explored. Mangroves protect shorelines, store carbon, enhance water quality, and promote biodiversity. Their restoration can be hindered by poor soils associated with urbanized coastlines. Sargassum spp. application in the form of mulch, compost, and plant tonics has yielded positive results in a range of plants. As part of transforming the inundations to benefit communities, Sargassum spp. compost (SC) was assessed in mangrove seedling production for restoration. Pure SC was mixed with soil/sand medium, as different treatments, for the production of Rhizophora mangle seedlings in “wet” and “dry” nurseries. Plants in the “wet” nursery performed poorly, with 90–100% of plants in 50 and 100% SC, respectively, dying after 6 weeks. Seedlings in all SC treatments in the “dry” nursery survived with obvious and statistically significant treatment differences. Height and number of leaves indicated the best growth in the 75% SC treatment, while the control (0% SC) had the poorest growth. Seedling health, greatest in the control, was poorest in 50 and 100% SC. Elemental analysis of SC, seedlings, and soil/sand medium indicated that several elements (Na, K, Ca, As, and Se) found in high concentrations in the SC were low in the plants. Overall, low sequestration of elements by mangrove seedlings and the reported ability of mangrove soils to reduce element mobilization through chelation indicate the potential use of Sargassum spp. in soil amelioration for mangrove restoration without proportional contamination of the ecosystem. We see the potential use of nuisance Sargassum spp. blooms to support mangrove restoration, leading to increased benefits to coastal communities being affected by the inundations.

Background Many ecologically and commercially important species occur in the epipelagic marine environment and have been observed to spend a considerable amount of time associating with surface structure. The bottom depth of this habitat often exceeds transmission (~ 500-1000 m) and receiver (500–750 m) range specifications for commonly used acoustic telemetry methods that rely on an array of receivers deployed on the seafloor with overlapping fields of detection to provide positioning of acoustically tagged individuals. This poses logistical challenges for tracking the fine-scale movements, behaviors, and associations to moored and free-floating structure of these species. Acoustic telemetry can provide high resolution positioning data for tagged animals within an array of receivers with overlapping fields of detection; however, this technique has not been applied in deep open-ocean environments off the benthos. Results Herein, we detail the development of a novel vertical acoustic telemetry array that can be mounted on, or suspended from, various moored and free-floating structures in the open ocean, thus facilitating high resolution tracking of structure-associated epipelagic animals. This new ‘vertical acoustic array’ (VAR) allows for the calculation of a transmitter’s distance from the array and depth with average error around these metrics ranging from 16.2 to 54.8 m (distance error) and 8.6 to 61.5 m (depth error) within the tested range (~ 500 m radius around the array, ~ 300 m deep). We also validated the ability of the VAR to inform the association of an epipelagic species to surface structure by calculating fine-scale positioning for a great barracuda around a fish aggregating device (FAD), which on average was 27.9 ± 2.9 m away at a depth of 9.3 ± 0.4 m over a 9-day tracking period, demonstrating high association with the structure. Conclusions This new array is able to provide two-dimensional (distance away and depth) animal behavior data around natural and anthropogenic moored and free-floating structures in open-ocean environments where bottom depths often exceed transmission (~ 1000 m) and receiver (~ 500 m) range specifications of traditional bottom moored positioning arrays. This array can also be used to quantitatively assess associations of epipelagic species beyond presence/absence using a single receiver, advancing the potential to improve understanding of the interactions between pelagic fauna and anthropogenic structures such as wind turbines, oil rigs, and fish aggregation devices.

Sharks were among the first marine animals to carry telemetry systems because of their size and the need to understand their interactions with humans. Modern telemetry systems can gather many kinds of data (limited only by imagination, funding and sensor types), indicating which animals are near telemetry receivers and what they are dong. Receivers now range from simple autonomous detector units for deployment in mid-water in large-scale grids, to sophisticated automated benthic recorders, to triangulating radio-linked buoy systems (RAP), to shipborne transponders. In addition, archival tags can now gather and store data even while the shark is away, to be downloaded later. Older types had to be recovered, but pop up tags release from sharks automatically, surface and transfer data to satellites, while CHAT tags download whenever queried by a nearby transponding acoustic receiver. Sophisticated animal-borne tags dramatically increase the information gathered about sharks and their environment. The examples provided show the parallel progression of shark biology and acoustic biotelemetry illustrating that telemetry systems are tools for gathering data, which can often be honed to facilitate biological experiments. Future visions include sensors that directly measure shark swimming power and cardiac output, compressing the data so that it can be delivered to RAP systems tracking multiple animals with meter resolution in near real time. CHAT tags as small as 22 mm diameter should be able to return similar data from trips of hundreds of kilometers. Continued communication between biologists and engineers is essential to develop these technologies.

The distributions of a variety of variables were used to characterise the physicochemical structure of inner bay waters in a reefal bay with a central channel. The aim was to describe emanations of the bay waters and the effectiveness of particular variables in depicting these emanations. In Wreck Bay—a semienclosed reefal bay located along the Hellshire south-east coast of Jamaica—distribution in temperature, salinity, dissolved oxygen, pH, and specific conductivity were used as potential indicators of the inner bay waters and their emanations. Variable profiles and contours showed that salinity and specific conductivity were found to be unreliable in characterising the bay waters because of the interruptions from numerous submarine seeps found inside and outside of the bay. However, temperature, pH, and dissolved oxygen were more robust in characterising bay waters with continuity from the inner bay, past the reef, and out to sea, even with the presence of the seeps. Surface emanations of bay waters beyond the reef were pronounced with the land-breeze regime but retarded by the entrainment of the sea breeze. Using these variables, it was evident that the reef was not effective in cutting off bay water and that inner bay waters and their characteristics persisted beyond the reef.