Horizontal and vertical movements of starry smooth-hound Mustelus asterias in the northeast Atlantic.

Commercial landings of starry smooth-hound Mustelus asterias in northern European seas are increasing, whilst our knowledge of their ecology, behaviour and population structure remains limited. M. asterias is a widely distributed demersal shark, occupying the waters of the southern North Sea and Irish Sea in the north, to at least the southern Bay of Biscay in the south, and is seasonally abundant in UK waters. There are no species-specific management measures for the northeast Atlantic stock, and the complexity of its population structure is not yet fully understood. To address this issue, we deployed both mark-recapture and electronic tags on M. asterias to gain novel insights into its horizontal and vertical movements. Our data suggest that the habitat use of M. asterias changes on a seasonal basis, with associated changes in geographical distribution, depth utilisation and experienced temperature. We report the first direct evidence of philopatry for this species, and also provide initial evidence of sex-biased dispersal and potential metapopulation-like stock structuring either side of the UK continental shelf. Investigations of finer-scale vertical movements revealed clear diel variation in vertical activity. The illustrated patterns of seasonal space-use and behaviour will provide important information to support the stock assessment process and will help inform any future management options.

Scaling marine fish movement behavior from individuals to populations.

Understanding how, where, and when animals move is a central problem in marine ecology and conservation. Key to improving our knowledge about what drives animal movement is the rising deployment of telemetry devices on a range of free-roaming species. An increasingly popular way of gaining meaningful inference from an animal's recorded movements is the application of hidden Markov models (HMMs), which allow for the identification of latent behavioral states in the movement paths of individuals. However, the use of HMMs to explore the population-level consequences of movement is often limited by model complexity and insufficient sample sizes. Here, we introduce an alternative approach to current practices and provide evidence of how the inclusion of prior information in model structure can simplify the application of HMMs to multiple animal movement paths with two clear benefits: (a) consistent state allocation and (b) increases in effective sample size. To demonstrate the utility of our approach, we apply HMMs and adapted HMMs to over 100 multivariate movement paths consisting of conditionally dependent daily horizontal and vertical movements in two species of demersal fish: Atlantic cod (Gadus morhua; n = 46) and European plaice (Pleuronectes platessa; n = 61). We identify latent states corresponding to two main underlying behaviors: resident and migrating. As our analysis considers a relatively large sample size and states are allocated consistently, we use collective model output to investigate state-dependent spatiotemporal trends at the individual and population levels. In particular, we show how both species shift their movement behaviors on a seasonal basis and demonstrate population space use patterns that are consistent with previous individual-level studies. Tagging studies are increasingly being used to inform stock assessment models, spatial management strategies, and monitoring of marine fish populations. Our approach provides a promising way of adding value to tagging studies because inferences about movement behavior can be gained from a larger proportion of datasets, making tagging studies more relevant to management and more cost-effective.

Spatial and temporal analysis of biliary 1-hydroxypyrene, hepatic ethoxyresorufin-O-deethylase and muscle acetylcholinesterase activity in UK flatfish.

Chemical pollution of the marine environment from anthropogenic sources is a global concern due to the potential for long term effects on the ecosystem. Chemical monitoring schemes can detect harmful substances in water, sediment or biota. However, the presence of specific determinants gives no information on how individual species or the ecosystem are impacted. Biological effects techniques are therefore used in environmental monitoring schemes to provide a clearer picture of whether the chemicals present are causing deleterious effects on the species sampled, or whether organisms have been exposed to certain classes of organic contaminants that they may be able to metabolise. Using these techniques, we can provide an assessment of the health of our marine environment (Thain et al., 2008).

Spatial and temporal analysis of the risks posed by polychlorinated biphenyl and metal contaminants in dab (Limanda limanda) collected from waters around England and Wales.

The metals cadmium, mercury and lead, and the ICES7 CB levels were analysed in the common dab Limanda limanda to investigate whether concentrations of these determinants are at levels above established OSPAR assessment criteria around England and Wales. The results indicate that CB118 is above the OSPAR derived EAC at 22 out of 29 sampled stations, with 15 showing significant reductions. Cadmium is increasing significantly at six stations with two sites in the North Sea breaching corresponding OSPAR EAC. Mean results for all other PCBs and metals stayed below the EAC thresholds, with Hg concentrations even falling below BAC levels at South Eddystone located in the western English Channel. This study shows that PCBs banned over 20years ago are still found at concentrations in fish liver tissues which may pose a health risk to both the individual fish and their predators.

Spatial and temporal analysis of the risks posed by polycyclic aromatic hydrocarbon, polychlorinated biphenyl and metal contaminants in sediments in UK estuaries and coastal waters.

The environmental risks of 22 contaminants, comprising 6 metals, 10 PAHs and 6 PCB congeners occurring in UK estuaries and coastal waters were assessed as single substances. Sediment samples were taken within 12 nautical miles of the English and Welsh coastlines between 1999 and 2011. The measured environmental concentrations were compared to quality standards including ERL, ERM and EAC, all of which have been established internationally. Out of a total of 38,031 individual samples analysed, 42.6% and 7.7% exceeded the ERL/EAC and ERM values, respectively. The highest Risk Characterisation Ratios (RCRs) for metals, PAHs and PCBs were observed for copper, fluorene and CB118 (2,3',4,4',5-pentachlorobiphenyl). In general, the highest concentrations of PAHs and PCBs were observed in 2011 in the Lower Medway indicating a potential risk to the aquatic environment. This study suggests that re-suspension of contaminants banned over 20years ago is still an ongoing issue.