In situ experimental evaluation of tag burden and gill biopsy reveals survival impacts on migrating juvenile sockeye salmon

Although telemetry is commonly used to study fishes, researchers rarely design experiments that facilitate in situ quantification of tagging-related impacts to survival. We experimentally applied high (mean burden = 9.6%) and low (2.6%) acoustic tag burdens and gill clip biopsies to migrating juvenile sockeye salmon (Oncorhynchus nerka). Mortality from release to the last marine receiver array was 1.51 times greater for the high tag burden group (25% surviving) compared with the low burden group (40% surviving). A biopsy effect was limited to the first migration segment (14 km), where mortality was 1.86 times greater for biopsied fish. These results demonstrate the importance of quantifying biopsy and tagging effects when survival estimates are prioritized.

Feasibility of using surgical implantation methods for acoustically tagging alewife (Alosa pseudoharengus) with V5 acoustic transmitters

Anadromous alewives (Alosa pseudoharengus) are abundant in the Canadian Maritimes, where they support lucrative commercial fisheries. Little is known about their coastal movement, and their potential to interact with anthropogenic structures. Acoustic telemetry can provide detailed information on the spatiotemporal distribution and survival of fishes in coastal areas, using information transmitted from tagged fishes and recorded by moored receivers. However, few acoustic telemetry studies have been performed on clupeids as they are extremely sensitive to handling, and are often compromised by surgical tag implantation. This research assesses the feasibility of a surgical tagging protocol using novel High Residency acoustic tags in alewives, and establishes a baseline of short-term tagging effects. Alewives from the Gaspereau River population were tagged between 2018 (n = 29) and 2019 (n = 96) with non-transmitting models of Vemco/Innovasea V5 HR tags. Tagging effects were evaluated based on recovery rate, reflex impairment, and necropsy-based health assessments. Alewives responded well to tagging, with low mortality (3%) and no observed instances of tag shedding 72 hours post-surgery. The use of sutures to close the incision site had no effect on recovery times. Water temperature and spawning condition had the greatest effect on the behavioural response of fish to tagging. Our findings suggest that, with proper handling and smaller acoustic tags, telemetry studies on alewives are feasible.

Improving the Bond Strength of Radiographically Tagged Caries Lesions In Vitro

After selective carious tissue removal, residual carious lesions remain radiographically detectable. Radiopaque tagging resolves the resulting diagnostic uncertainty but impedes bond strengths of adhesives to tagged dentin. We developed a protocol mitigating these detrimental effects. A 30%/50%/70% SnCl2 solution was dissolved in distilled water or a 30%/50%/90% ethanol solution (E30/60/90) and applied to artificially induced dentin lesions. Tagging effects were radiographically evaluated using transversal wavelength-independent microradiography (n = 6/group). Groups with sufficient tagging effects at the lowest SnCl2 concentrations were used to evaluate how tagging affected the microtensile bond strength of a universal adhesive (Scotchbond Universal) to sound and carious dentin (n = 10/group). Two different protocols for removing tagging material were tested: 15 s phosphoric acid etching and 5 s rotating brush application. Scanning/backscattered electron microscopy (SEM/BSE) and energy-dispersive X-ray spectroscopy (EDS) were used to assess surfaces after tagging and removal. The most promising removal protocol was revalidated microradiographically. Tagging significantly increased the radiopacity, with consistent effects for 30% SnCl2 dissolved in water or E30. Microscopically, tagged surfaces showed a thick carpet of SnCl2, and tagging reduced bond strengths significantly on carious dentin but not on sound dentin (p < 0.01). On carious dentin, removal of tagging material using acid etching and rotating brush was microscopically confirmed. Acid etching also mitigated any bond strength reduction (median: 21.3 MPa; interquartile range: 10.8 MPa) compared with nontagged dentin (median: 17.4 MPa; interquartile range: 20.6 MPa). This was not the case for brushing (median: 13.2 MPa; interquartile range: 13.9 MPa). Acid etching minimally reduced the radiographic tagging effect (p = 0.055). Phosphoric acid etching reduces the detrimental bond-strength effects of tagging without significantly decreasing radiographic tagging effects when using a universal adhesive.

Short-term responses of sperm whales Physeter macrocephalus to the attachment of suction cup tags

Animal-mounted data logging devices are used to study the behaviour, physiology, and ecology of free-ranging marine mammals, as well as their reactions to controlled exposures. It is important to consider whether collected data are representative of natural behaviour or biased by responses to tagging. In species with stereotypical diving behaviour, tagging responses can be quantified by identifying anomalous dives. Data from 36 suction cup tag deployments on sperm whales Physeter macrocephalus from 4 locations were analysed to consider whether tagging effects were evident within 5 dive parameters: maximum dive depth, dive duration, descent speed, depth difference between start of clicking and first prey capture attempt, and buzz rate. Linear mixed models were generated for each response parameter and covariates for dive index were added to assess whether model fit improved when the order of dives was taken into account. Time-decaying tagging effects were noted in maximum dive depth (first dives were 25% shallower than average) and buzz rate (first dives contained 34% fewer buzzes per minute than average). In the Azores, the first 3 dives subsequent to tag attachment featured faster descent speeds than average. The whales were likely responding to the cumulative ‘dose’ of research activity at the surface: multiple boat approaches, tag placement, and general disturbance. Disturbance should be minimised during tagging, and the extent and duration of responses should be quantified. Modelling of quantified tagging responses could enable correction of these responses in tag data.

Tags below three percent of body mass increase nest abandonment by rhinoceros auklets, but handling impacts decline as breeding progresses

Biologging has revealed many of the mysteries surrounding seabird behavior far from land. However, tagging seabirds with biologgers may influence the very traits they are designed to observe. Such ‘tag effects’ are often argued to be minimal below a threshold of 3% of body mass. Nonetheless, few studies carefully separate handling from tagging effects, so the effect of tag size is often confounded with the effect of handling. Puffins, including rhinoceros auklets Cerorhinca monocerata, are notoriously difficult to work with due to high nest abandonment rates. To examine tagging and handling effects in rhinoceros auklets, we compared abandonment rates of individuals equipped with a GPS weighing ~2.3% of body mass with abandonment rates of birds handled but not equipped, and of birds not handled at all (controls). We used the egg flotation technique to estimate egg development and predict hatching date, thus allowing treatments to be applied at the appropriate time. Handling more than doubled abandonment rates compared to control birds, and tagging more than doubled abandonment rates compared to birds that were handled but not tagged. Abandonment rates decreased as incubation progressed and were lowest during chick-rearing. We conclude that both handling and tagging of auklets increase abandonment, and that effects are lowest during chick-rearing.

Tagging effects on the mid-infrared spectrum of microsolvated protonated methane

Although bare protonated methane is by now essentially understood at the level of intramolecular large-amplitude motion, scrambling dynamics and broadband vibrational spectra, the microsolvated species still offer plenty of challenges.