Variation in habitat preference and distribution of harbour porpoises west of Scotland

The waters off the west coast of Scotland have one of the highest densities of harbour porpoise (Phocoena phocoena) in Europe. Harbour porpoise are listed under Annex II of the EU Habitats Directive, requiring the designation of Special Areas of Conservation (SACs) for the species’ protection and conservation. The main aim of this thesis is to identify habitat preferences for harbour porpoise, and key regions that embody these preferences, which could therefore be suitable as SACs; and to determine how harbour porpoise use these regions over time and space. Designed visual and acoustic line-transect surveys were conducted between 2003 and 2008. Generalised Estimating Equations (GEEs) were used to determine relationships between the relative density of harbour porpoise and temporally and spatially variable oceanographic covariates. Predictive models showed that depth, slope, distance to land and spring tidal range were all important in explaining porpoise distribution. There were also significant temporal variations in habitat use. However, whilst some variation was observed among years and months, consistent preferences for water depths between 50 and 150 m and highly sloped regions were observed across the temporal models. Predicted surfaces revealed a consistent inshore distribution for the species throughout the west coast of Scotland. Regional models revealed similar habitat preferences to the full-extent models, and indicated that the Small Isles and Sound of Jura were the most consistently important regions for harbour porpoise, and that these regions could be suitable as SACs. The impacts of seal scarers on distribution and habitat use were also investigated, and there were indications that these devices have the potential to displace harbour porpoise. These results should be considered in the assessment of sites for SAC designation, and in implementing appropriate conservation measures for harbour porpoise

An expert elicitation of the effects of low salinity water exposure on bottlenose dolphins

This research was funded by National Marine Fisheries Service for support via awards: NFFKPR00-19-01552 and NA20NMF0080281.There is increasing concern over anthropogenically driven changes in our oceans and seas, from a variety of stressors. Such stressors include the increased risk of storms and precipitation, offshore industries and increased coastal development which can affect the marine environment. For some coastal cetacean species, there is an increased exposure to low salinity waters which have been linked with a range of adverse health effects in bottlenose dolphins. Knowledge gaps persist regarding how different time–salinity exposures affect the health and survival of animals. In such data-poor instances, expert elicitation can be used to convert an expert’s qualitative knowledge into subjective probability distributions. The management implications of this stressor and the subjective nature of expert elicitation requires transparency; we have addressed this here, utilizing the Sheffield Elicitation Framework. The results are a series of time response scenarios to estimate time to death in bottlenose dolphins, for use when data are insufficient to estimate probabilistic summaries. This study improves our understanding of how low salinity exposure effects dolphins, guiding priorities for future research, while its outputs can be used to support coastal management on a global scale.Publisher PDFPeer reviewe

Methods for monitoring for the population consequences of disturbance in marine mammals : a review

This work was sponsored by the Office of Naval Research: Marine Mammal Biology Program, under award N000141612858.Assessing the non-lethal effects of disturbance and their population-level consequences is a significant ecological and conservation challenge, because it requires extensive baseline knowledge of behavioral patterns, life-history and demography. However, for many marine mammal populations, this knowledge is currently lacking and it may take decades to fill the gaps. During this time, undetected population declines may occur. In this study we identify methods that can be used to monitor populations subject to disturbance and provide insights into the processes through which disturbance may affect them. To identify and address the knowledge gaps highlighted above, we reviewed the literature to identify suitable response variables and methods for monitoring these variables. We also used existing models of the population consequences of disturbance (PCoD) to identify demographic characteristics (e.g., the proportion of immature animals in the population, or the ratio of calves/pups to mature females) that may be strongly correlated with population status and therefore provide early warnings of future changes in abundance. These demographic characteristics can be monitored using established methods such as visual surveys combined with photogrammetry, and capture-recapture analysis. Individual health and physiological variables can also inform PCoD assessment and can be monitored using photogrammetry, remote tissue sampling, hands-on assessment and individual tracking. We then conducted a workshop to establish the relative utility and feasibility of all these approaches for different groups of marine mammal species. We describe how future marine mammal monitoring programs can be designed to inform population-level analysis.Publisher PDFPeer reviewe

Estimating reproductive costs in marine mammal bioenergetic models : a review of current knowledge and data availability

This review was funded by the Office of Naval Research (N000142012392), with support from the Marine Mammal Commission (MMC 19-173).Reproductive costs represent a significant proportion of a mammalian female's energy budget. Estimates of reproductive costs are needed for understanding how alterations to energy budgets, such as those from environmental variation or human activities, impact maternal body condition, vital rates and population dynamics. Such questions are increasingly important for marine mammals, as many populations are faced with rapidly changing and increasingly disturbed environments. Here we review the different energetic costs that marine mammals incur during gestation and lactation and how those costs are typically estimated in bioenergetic models. We compiled data availability on key model parameters for each species across all six marine mammal taxonomic groups (mysticetes, odontocetes, pinnipeds, sirenians, mustelids and ursids). Pinnipeds were the best-represented group regarding data availability, including estimates of milk intake, milk composition, lactation duration, birth mass, body composition at birth and growth. There were still considerable data gaps, particularly for polar species, and good data were only available across all parameters in 45\poor, with some species having little or no data for any parameters, particularly beaked whales. Even for species with moderate data coverage, many parameter estimates were tentative or based on indirect approaches, necessitating reevaluation of these estimates. We discuss mechanisms and factors that affect maternal energy investment or prey requirements during reproduction, such as prey supplementation by offspring, metabolic compensation, environmental conditions and maternal characteristics. Filling the existing data gaps highlighted in this review, particularly for parameters that are influential on bioenergetic model outputs, will help refine reproductive costs estimated from bioenergetic models and better address how and when energy imbalances are likely to affect marine mammal populations.Publisher PDFPeer reviewe

Combining bioenergetics and movement models to improve understanding of the population consequences of disturbance

Funding: Naval Facilities Engineering Systems Command EXWC - N3943019C2175.We developed dynamic bioenergetics models to investigate how behavioural responses to anthropogenic disturbance events might affect the population dynamics of three marine mammal species (harbour porpoise, grey seal and harbour seal) with contrasting life-history traits (capital versus income breeders) and movement behaviour (resident versus nomadic). We used these models to analyse how individual vital rates were affected by differences in the probability of disturbance and the duration of any behavioural response, while taking account of uncertainty in the model parameters and heterogeneity in behaviour. The outputs of individual movement models and telemetry data were then used to determine how the probability of exposure might vary among species, individuals, and geographical locations. We then demonstrate how these estimated probabilities of exposure can be translated into probabilities of disturbance. For illustrative purposes, we modelled the potential effects of a temporary decrease in energy assimilation associated with a series of disturbance events that might realistically occur during the construction of an offshore windfarm. Offspring starvation mortality was the vital rate that was most affected by these disturbance events. Monitoring of rate should be considered as standard practice so that populations responses can be detected as early as possible. Predicted effects on individual vital rates depended on the species' movement behaviour and the likely density of animals where the modelled construction activity was assumed to take place. The magnitude of these effects also depended critically on the assumed duration of the reduction in energy assimilation. No direct estimates of this variable are currently available, but we suggest some ways in which it could be estimated. The described approach could be extended to other species and activities, given sufficient information to parameterise the component models. However, we emphasise the need to account for among-individual heterogeneities and uncertainties in the values of the many model parameters.Publisher PDFPeer reviewe

Model predicts catastrophic decline of common bottlenose dolphin (Tursiops truncatus) population under proposed land restoration project in Barataria Bay, Louisiana, USA

Funding: Fundação para a Ciência e a Tecnologia (Grant Number(s): UIDB/00006/2020).Publisher PDFPeer reviewe

Fluorine negative ion density measurement in a dual frequency capacitive plasma etch reactor by cavity ring-down spectroscopy

F⁻ negative ions were detected by direct observation of the weak photodetachmentabsorption continuum below 364.5nm by cavity ring-down spectroscopy. The negative ions were generated in a modified industrial dielectricplasmaetch reactor, with 2+27MHz dual frequency capacitive excitation in Ar∕CF₄∕O₂ and Ar∕C₄F₈∕O₂ gas mixtures. The F⁻ signal was superimposed on an unidentified absorption continuum, which was diminished by O₂ addition. The F⁻ densities were in the range of (0.5–3)×10¹¹cm⁻³, and were not significantly different for single (27MHz) or dual (2+27MHz) frequency excitation, not confirming recent modeling predictions.The authors wish to thank Lam Research Corporation for donation of equipment and financial support

Population consequences of the Deepwater Horizon oil spill on pelagic cetaceans

This research was made possible by a grant from the Gulf of Mexico Research Initiative to the Consortium for Advanced Research on Marine Mammal Health Assessment (CARMMHA). T.A.M. acknowledges partial support by CEAUL (funded by FCT−Fundação para a Ciência e a Tecnologia, Portugal, through project UIDB/00006/2020).The Deepwater Horizon disaster resulted in the release of 490000 m3 of oil into the northern Gulf of Mexico. We quantified population consequences for pelagic cetaceans, including sperm whales, beaked whales and 11 species of delphinids. We used existing spatial density models to establish pre-spill population size and distribution, and overlaid an oil footprint to estimate the proportion exposed to oil. This proportion ranged from 0.058 (Atlantic spotted dolphin, 95% CI = 0.041-0.078) to 0.377 (spinner dolphin, 95% CI = 0.217-0.555). We adapted a population dynamics model, developed for an estuarine population of bottlenose dolphins, to each pelagic species by scaling demographic parameters using literature-derived estimates of gestation duration. We used expert elicitation to translate knowledge from dedicated studies of oil effects on bottlenose dolphins to pelagic species and address how density dependence may affect reproduction. We quantified impact by comparing population trajectories under baseline and oil-impacted scenarios. The number of lost cetacean years (difference between trajectories, summed over years) ranged from 964 (short-finned pilot whale, 95% CI = 385-2291) to 32584 (oceanic bottlenose dolphin, 95% = CI 13377-71967). Maximum proportional population decrease ranged from 1.3% (Atlantic spotted dolphin 95% CI = 0.5-2.3) to 8.4% (spinner dolphin 95% CI = 3.2-17.7). Estimated time to recover to 95% of baseline was >10 yr for spinner dolphin (12 yr, 95% CI = 0-21) and sperm whale (11 yr, 95% CI = 0-21), while 7 taxonomic units remained within 95% of the baseline population size (time to recover, therefore, as per its definition, was 0). We investigated the sensitivity of results to alternative plausible inputs. Our methods are widely applicable for estimating population effects of stressors in the absence of direct measurements.Publisher PDFPeer reviewe

A decision framework to identify populations that are most vulnerable to the population level effects of disturbance

This study was supported by Office of Naval Research grant N00014-16-1-2858: “PCoD+: Developing widely-applicable models of the population consequences of disturbance.”We present a decision framework to identify when detailed population-level assessments are required to understand the potential impacts of a disturbance-inducing activity on a marine mammal population and discuss how the framework can be applied to other taxa. Species at high risk of population-level effects can be identified using information on the number of individuals that are likely to be disturbed by the activity, total population size, the probability of repeated disturbance, the species’ reproductive strategy, and the life stages (e.g., feeding, pregnant, lactating) of the individuals most likely to be exposed. This hierarchical approach provides those responsible for conducting impact assessments with a time-efficient, cost-effective and reproducible workflow that allows them to prioritise their efforts and assign funds to those species with the most pressing conservation needs. A fully worked case study using marine mammals in the vicinity of a naval training activity is supplied.Publisher PDFPeer reviewe

Estimating energetic intake for marine mammal bioenergetic models

This work was primarily funded under an award from Office of Naval Research: N000142012392, and with support from the Marine Mammal Commission project: “A priority setting exercise to identify key unanswered questions in marine mammal bioenergetics”. Funding from the Joint Nature Conservation Committee supported fish energy analyses - award C180241-1285.Bioenergetics is the study of how animals achieve energetic balance. Energetic balance results from the energetic expenditure of an individual and the energy they extract from their environment. Ingested energy depends on several extrinsic (e.g prey species, nutritional value and composition, prey density and availability) and intrinsic factors (e.g. foraging effort, success at catching prey, digestive processes and associated energy losses, and digestive capacity). While the focus in bioenergetic modelling is often on the energetic costs an animal incurs, the robust estimation of an individual’s energy intake is equally critical for producing meaningful predictions. Here, we review the components and processes that affect energy intake from ingested gross energy to biologically useful net energy (NE). The current state of knowledge of each parameter is reviewed, shedding light on research gaps to advance this field. The review highlighted that the foraging behaviour of many marine mammals is relatively well studied via biologging tags, with estimates of success rate typically assumed for most species. However, actual prey capture success rates are often only assumed, although we note studies that provide approaches for its estimation using current techniques. A comprehensive collation of the nutritional content of marine mammal prey species revealed a robust foundation from which prey quality (comprising prey species, size and energy density) can be assessed, though data remain unavailable for many prey species. Empirical information on various energy losses following ingestion of prey was unbalanced among marine mammal species, with considerably more literature available for pinnipeds. An increased understanding and accurate estimate of each of the components that comprise a species NE intake are an integral part of bioenergetics. Such models provide a key tool to investigate the effects of disturbance on marine mammals at an individual and population level and to support effective conservation and management.Publisher PDFPeer reviewe