Porpoises, by-catch and the ‘pinger’ conundrum

Open Access through the Wiley agreement CKNOWLEDGEMENTS Thanks to Prof. John Baxter and two anonymous reviewers, whose comments greatly improved this article.Peer reviewedPublisher PD

Investigating the role of prey depletion in cetacean distributions and population dynamics

34th European Cetacean Society Conference, O Grove, 16-20 April 2023A key driver in determining the distribution and demography of cetaceans is the dispersion of their prey, in terms of availability, abundance and quality. A Working Group on Resource Depletion has been established within ASCOBANS to review current knowledge and develop recommendations for research and action. It includes members with expertise in veterinary and fishery science, cetacean biology, ecology and conservation. The group has eight terms of reference - reviewing and collating recent information on resource depletion and its impacts, prey distribution and abundance, health and condition indicators, small cetacean diet, spatio-temporal trends in small cetacean species, emerging technologies, integrating information from multiple data sources, and making recommendations for possible mitigation measures to aid conservation. As a first step, the group has summarised information on the diets of all small cetacean species regularly occurring in the ASCOBANS Agreement Area, and explored the parameters required to assess cetacean health and condition at both an individual and population level. The need to better understand prey choice in terms of prey availability and caloric content is highlighted along with the development of indicators of food shortage through necropsies of dead animals and photographic assessments of body condition in live animals. Future research, monitoring and conservation needs include refining the definition of prey depletion, developing prey depletion reference points, and articulating associated conservation objectives. We also need a better understanding of the relationships between cetacean physiology, energetics, body condition, health and diet, and of the population and ecosystem level consequences of prey depletion (e.g. based on the use of ecosystem models). Improved monitoring of prey and cetacean distribution and abundance at relevant spatiotemporal scales would facilitate estimation and mapping of resource depletion riskN

Conservation management of common dolphins: Lessons learned from the North‐East Atlantic

30 pages, 3 tables, 3 figuresThe short‐beaked common dolphin is one of the most numerous cetacean species in the North‐East Atlantic and plays a key functional role within the ecosystem as a top predator. However, in 2013, its conservation status for the European Marine Atlantic, under Article 17 of the Habitats Directive, was assessed as ‘Unfavourable‐Inadequate’. Of key concern for this species is fishery bycatch, with pollution also being an issue. There are, however, major knowledge gaps concerning the extent of the effects of such pressures on the species. Implementation of national observer bycatch programmes and bycatch mitigation measures under EC Regulation 812/2004 has been important. The responsibility for this is currently being transferred to the EU fisheries Data Collection Framework and Technical Measures Framework, the potential advantages and disadvantages of which are discussed. Collection of data and samples through national stranding schemes in some countries has enabled assessments of life‐history parameters, dietary requirements, and the effects of stressors such as pollutants. Nevertheless, in order to improve the conservation status of the North‐East Atlantic population, a number of key actions are still required. These include the implementation of a species action plan, finalization of a management framework procedure for bycatch, and coordination between member states of monitoring programmes. It is important that there is monitoring of the state of the common dolphin population in the North‐East Atlantic management unit through regular surveys spanning the range of the management unit, as well as continued assessment of the independent and interactive effects of multiple stressors. Above all, conservation status would be improved through application and enforcement of existing legislation in European waters. This paper provides a summary of the current state of our knowledge of common dolphins in the North‐East Atlantic along with recommendations for conservation management that may also be relevant to the species in the Mediterranean SeaGJP thanks the University of Aveiro and Caixa Geral de Depositos (Portugal) for financial supportPeer reviewe

Review of analytical approaches for identifying usage and foraging areas at sea for harbour seals

The purpose of this report is to build upon the outputs of work undertaken by the Sea Mammal Research Unit (SMRU, University of St Andrews) funded by the Department of Energy and Climatic Change (DECC) and the Scottish Government, in order to draw these strands of work together with the aim of identifying whether discrete and persistent foraging areas for harbour seals (Phoca vitulina) can be identified in the UK marine area.A usage map of harbour seal at-sea distribution is presented in order to identify important at-sea areas for the species. Usage is the estimate of the instantaneous density of seals at sea. This is based upon movement data derived from 277 telemetry tags deployed between 2003 and 2013, combined with terrestrial haul-out count data from 1996 to 2013. These data were collected by two tag types: Satellite Relay Data Loggers (SRDL) that use the Argos satellite system for location estimation and data transmission, and GPS phone tags that use the GSM mobile phone network for data transmission. The usage map extends to the limit of UK harbour seal movements and has a spatial resolution of 5km x 5km. Seal usage within the 5km x 5km cells is estimated (using current and historical data where appropriate) for the year 2013. The data do not support breaking down this usage map by year, season, or by the intrinsic properties of seal age or sex. Uncertainty is incorporated into the usage map estimation so that 95% confidence intervals of individual cell usage are available.Regional significance is demonstrated by dividing the usage map into five Harbour Seal Areas (HSAs). Within each HSA, grid cells are ranked in descending order based on the estimated usage in each cell. Grid cells are selected, beginning with the most intensively used cells, until 10% of the total usage of each HSA is included. This is repeated in 10% increments (up to 90%) of individual HSA usage and the resulting maps are presented.Usage maps could be made more accurate with strategically-located future deployments of tags. This would also help indicate whether high usage areas are persistent in the long term. The usage maps are weighted by the terrestrial distribution of harbour seals surveyed during the moult (August) period. However, there may be redistribution over the rest of the year so synoptic haul-out counts outside the moult period are needed to test whether this is a significant issue. Usage maps present a ‘snapshot’ of seal usage: they show the estimated number of seals per grid square at any instant in time, in this case the year is 2013.Estimating activity-unclassified usage is informative for management, since it integrates all activities (all of which are considered to be essential for harbour seals) into one simple index. There may be added value in classifying activity because it would allow activity-specific management. For instance, changes in prey abundance and distribution may be important in areas where foraging dominates, but less important in areas used primarily for travelling. By contrast, in some cases disturbance may have more serious implications in travelling areas; if only one travelling route connects a haul-out and offshore foraging area then disturbance on such routes, for example during wind farm construction, may cause barriers to movement.A State Space Modelling (SSM) framework was developed that uses track speed and tortuosity, and diving behaviour to disaggregate foraging, travelling and resting activities. Using this framework, it was demonstrated that data collected using SRDL tags are not suitable for estimation of activity states in harbour seals (e.g. foraging); only data from GPS phone tags are of the high temporal resolution required to define activities. There are no usage maps of these activities currently available. However, activity-specific locations of tagged individuals from a DECC-funded study at The Wash were overlaid onto local population usage. This simple comparison indicates that offshore high usage areas, in this region at least, are typically associated with a relatively high density of foraging locations. Such a comparison would not be appropriate elsewhere because other regions for whichGPS data are available are dominated by complex coastlines encompassing multiple haul-out sites. In such regions usage in a given at-sea grid cell results from tracks emanating from multiple haul-out site cells; the usage resulting from each haul-out site cell is then weighted by the population size of that haul-out site cell. Therefore a comparison of the locations of tagged individuals with population level usage would not be appropriate. Such a comparison is possible for The Wash because it comprises a small group of isolated haul-out site cells meaning that both population level usage and foraging locations emanate from the same sites.Extensive work would be required to use the activity data to quantify key foraging areas. Even though the activity-unclassified usage maps included data from SRDL tags, a lack of telemetry data associated with haul-out site cells meant that 48% of the total harbour seal usage had to be predicted based on the relationship between usage and distance to haul-out sites for those haul-out site cells for which telemetry data were available. This percentage would increase with the exclusion of SRDL data, and predictions based on distance to haul-out sites would be inappropriate for predicting foraging areas. Thus, habitat preference analyses, for which environmental covariates are linked to foraging, is likely to be the most suitable way to in predict key foraging areas

A note on the unprecedented strandings of 56 deep-diving whales along the UK and Irish coast

In the first seven months of 2008, eighteen Cuvier’s beaked whales (Ziphius cavirostris), four Sowerby’s beaked whales (Mesoplodon bidens), five unidentified beaked whales and twenty-nine long-finned pilot whales (Globicephala melas) were reported stranded in the UK and Ireland. Decomposition of those animals investigated puts the predicted time of death at mid-January. Concerns that an unusual mortality event had taken place prompted further investigations. Most carcasses were too decomposed for necropsy. A summary of findings is presented here. Although the initial stranding of five Cuvier’s beaked whales in Scotland shared some similarities with atypical mass stranding events linked in time and space to mid-frequency naval sonars, there were two important differences with the remaining strandings during this period. First, the geographical range of the event was very wide and second, the strandings occurred over a prolonged period of several months. Both of these factors could be related to the fact that the mortalities occurred offshore and the carcasses drifted ashore. The cause(s) of this high number of strandings of mixed offshore cetacean species during this period remain undetermined