Tracking of marine animals has increased exponentially in the past decade, and the resulting data could lead to an in-depth understanding of the causes and consequences of movement in the ocean. However, most common marine tracking systems are associated with large measurement errors. Accounting for these errors requires the use of hierarchical models, which are often difficult to fit to data. Using 3 case studies, we demonstrate that Template Model Builder (TMB), a new R package, is an accurate, efficient and flexible framework for modelling movement data. First, to demonstrate that TMB is as accurate but 30 times faster than bsam, a popular R package used to apply state-space models to Argos data, we modelled polar bear Ursus maritimus Argos data and compared the locations estimated by the models to GPS locations of these same bears. Second, to demonstrate how TMB's gain in efficiency and frequentist framework facilitate model comparison, we developed models with different error structures and compared them to find the most effective model for light-based geolocations of rhinoceros auklets Cerorhinca monocerata. Finally, to maximize efficiency through TMB's use of the Laplace approximation of the marginal likelihood, we modelled behavioural changes with continuous rather than discrete states. This new model directly accounts for the irregular sampling intervals characteristic of Fastloc-GPS data of grey seals Halichoerus grypus. Using real and simulated data, we show that TMB is a fast and powerful tool for modelling marine movement data. We discuss how TMB's potential reaches beyond marine movement studies.

Satellite telemetry data have substantially increased our understanding of habitat use and foraging behaviour of upper-trophic marine predators, but fall short of providing an understanding of their social behaviour. We sought to determine whether novel acoustic and archival GPS data could be used to examine at-sea associations among grey seals (Halichoerus grypus) during the fall foraging period. Fifteen grey seals from Sable Island, Canada were deployed with Vemco Mobile Transceivers and Satellite-GPS transmitters in October 2009, 13 of which were recaptured and units retrieved 79±2.3 days later during the following breeding season, December 2009–January 2010. An association between two individuals was defined as a cluster of acoustic detections where the time between detections was <30 min. Bathymetry, travel rate, and behavioural state (slow and fast movement) were determined for each GPS archival point (3.7±0.1 locations recorded per hour). Behavioural state was estimated using a hidden Markov model. All seals had been involved in associations with other instrumented seals while at sea, with a total of 1,872 acoustic detections recorded in 201 associations. The median number of detections per association was 3 (range: 1–151) and the median duration of an association was 0.17 h (range: <0.1–11.3 h). Linear mixed-effects models showed that associations occurred when seals were exhibiting slow movement (0.24±0.01 ms−1) on shallow (53.4±3.7 m) offshore banks where dominant prey is known to occur. These results suggest the occurrence of short-term associations among multiple individuals at foraging grounds and provide new insights into the foraging ecology of this upper-trophic marine predator.

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Culling is widely practised as a means to reduce predation effects of terrestrial carnivores, birds and marine mammals in many parts of the world. Of marine mammals, coastal pinniped species have usually been the target of culling programs, but dolphins and a large odontocete have also been culled. We reviewed the published literature on marine mammal culling programs to evaluate the extent of their efficacy as a fisheries management measure. Changes in species' distributions and abundance demonstrate that culling programs can be very effective at reducing predator density. Several conclusions from experimental studies of terrestrial mammals and birds may also apply to marine mammal control. Firstly, predator removal generally increases productivity and population size of target prey populations, but not always. Secondly, culling programs typically involve a large proportional reduction (>50%) in predator populations. Thirdly, the effects of culling are typically dependent on continued control, and in the absence of control the population rapidly returns to pre‐culling density. This underscores the need for predator removal to be a long‐term management strategy. Fourthly, culling predators often has non‐intuitive and unintended consequences for target species and for other predator and prey species. Marine mammal culling programs rarely have measurable objectives with respect to prey populations, and their success has not been evaluated. Culling marine mammals is controversial because of the following: (i) they are high‐profile charismatic megafauna; (ii) many populations are recovering from a period of over‐exploitation while others remain threatened or endangered; and (iii) the scientific evidence needed to justify a cull is usually highly uncertain. Marine mammal culling programs should be based on scientific analysis with stated and measurable objectives to be evaluated during planned follow‐up monitoring.

Pinnipeds are abundant upper trophic level predators in many marine ecosystems. Top-down effects of their consumption can play important roles in ecosystem structure and functioning. However, interactions between pinnipeds and their prey remain poorly understood due to their inaccessibility while foraging at sea. This uncertainty has fueled debate on the impact of seal predation on fish stocks of commercial or conservation interest. Here, we show that a novel combination of acoustic (Vemco Mobile Transceiver, VMT) and GPS technology can be used to determine the spatial and temporal pattern of interactions between grey seals Halichoerus grypus and fish species in 2 large marine ecosystems, the Eastern Scotian Shelf and the southern Gulf of St. Lawrence, Canada. During 4 yr of study, the VMT on 9 of 64 adult grey seals recorded detections from 3 species of fish, namely 17 adult Atlantic cod Gadus morhua, 7 Atlantic salmon Salmo salar and 1 American eel Anguilla rostrata implanted with coded acoustic tags. An examination of the temporal and spatial pattern of these seal−fish interactions suggested that 1 salmon and 2 cod might have been predated on. However, to have confidence in the occurrence of a predation event, more conclusive evidence is required, which may be gathered through validation experiments. These preliminary results provide proof-of-concept that large upper trophic level marine predators fitted with VMT and GPS tags can provide information on species locations in areas where fixed receiver arrays are not present and allow new insights into the nature of interspecies interactions in otherwise inaccessible environments.