Habitat-mediated dive behavior in free-ranging grey seals

Understanding the links between foraging behaviour and habitat use of key species is essential to addressing fundamental questions about trophic interactions and ecosystem functioning. Eight female grey seals (Halichoerus grypus) were equipped with time-depth recorders linked to Fastloc GPS tags following the annual moult in southwest Ireland. Individual dives were coupled with environmental correlates to investigate the habitat use and dive behaviour of free-ranging seals. Dives were characterised as either pelagic, benthic, or shallow (where errors in location and charted water depth made differentiating between pelagic and benthic dives unreliable). Sixty-nine percent of dives occurring in water >50 m were benthic. Pelagic dives were more common at night than during the day. Seals performed more pelagic dives over fine sediments (mud/sand), and more benthic dives when foraging over more three-dimensionally complex rock substrates. We used Markov chain analysis to determine the probability of transiting between dive states. A low probability of repeat pelagic dives suggests that pelagic prey were encountered en route to the seabed. This approach could be applied to make more accurate predictions of habitat use in data-poor areas, and investigate contentious issues such as resource overlap and competition between top predators and fisheries, essential for the effective conservation of these key marine species

Comparison of Inorganic and Organic Matter Sedimentation in a Natural Laboratory: A One-Year Study at Lough Hyne Marine Reserve, Ireland

Measuring sedimentation rates may provide useful information on the habitat preferences of marine organisms. To understand the effect of flow rates and meteorological conditions on sedimentation in the absence of other confounding factors, sedimentation of organic (OM) and inorganic (IOM) matters was measured at 6 sites in Lough Hyne Marine Reserve (a semienclosed marine lake) over the course of 13 months. During winter, both OM and IOM were imported to the Lough, peaking in December at Whirlpool, the site nearest to the Lough entrance, likely as a result of extreme weather conditions causing resuspension of matter outside the Lough. Highest inorganic matter (IOM) sedimentation occurred in December (47.36 gm−2d−1 at Whirlpool Cliff) and was related to November wind speeds (, ). Decreasing current speed also caused a decline in IOM sedimentation. Highest OM sedimentation occurred in December at Whirlpool (5.59 gm−2d−1), but was not related to meteorological conditions. No single environmental factor strongly influenced organic matter (OM) sedimentation. One-way ANOVAs on OM and log-transformed IOM data showed that sedimentation differed significantly amongst the six sites within the Lough. Increased plankton production in the Lough during summer led to increased OM sedimentation in areas of low current speed away from the entrance of the Lough

Characterising the nature of ocean-surface heterogeneity extracted from hypertemporal Earth Observation data

The ongoing temporal data "explosion" in Earth Observation imagery presents the oceanographic community with opportunities to analyse 30+ year archives of ocean surface measurements. While multiple hyper-temporal analysis tools exist for terrestrial applications, unsupervised data-driven methods are needed to extract and identify spatio-temporal ocean surface patterns. In particular, heterogeneity mapping of the ocean surface is needed to underpin time series analysis of satellite-derived ocean parameters, such as sea surface temperature and chlorophyll. Ultimately, derived products must be of benefit to the oceanographic and marine ecology communities, with clear meaningful guidance on their contents and how to interpret them. The Ocean-surface Heterogeneity MApping (OHMA) algorithm was developed to extract annual heterogeneity summaries from hyper-temporal datasets of GHRSST multi-sensor SST data. The OHMA algorithm produces a classification ensemble relying on optimised iterations of ISODATA classification. The ensembles highlight spatio-temporally homogeneous and heterogeneous ocean regions. The approach is entirely data-driven to meet current limitations when working with hyper-temporal ocean data, and to overcome challenges of obtaining ocean surface in-situ data which drive more supervised approaches. The OHMA map is validated for 2011 using measures of in-situ spatio-temporal heterogeneity from transect data. This approach can help optimise in-situ sampling efforts, with significant cost savings. It is critical to provide guidance to oceanographic and ecology users on how to interpret the features an OHMA map presents. Efforts undertaken to clarify interpretation of an OHMA map, through comparing the heterogeneity features highlighted in the OHMA outputs to SST front summaries derived from SST data, clearly demonstrated that heterogeneous regions cannot be explained primarily by the presence and magnitude of SST fronts. The spatio-temporal characteristics of other mesoscale features, such as eddies and surface currents, may also influence the features expressed in an OHMA output which are of interest to end user communities. Measuring the contribution of the various mesoscale features to a region's heterogeneity, therefore requires a multi-feature (and therefore multi-variable) synergistic approach

Spatial overlap of grey seals and fisheries in Irish waters, some new insights using telemetry technology and VMS

Seals and humans often target the same food resource, leading to competition. This is of mounting concern with fish stocks in global decline. Grey seals were tracked from southeast Ireland, an area of mixed demersal and pelagic fisheries, and overlap with fisheries on the Celtic Shelf and Irish Sea was assessed. Overall, there was low overlap between the tagged seals and fisheries. However, when we separate active (e.g. trawls) and passive gear (e.g. nets, lines) fisheries, a different picture emerged. Overlap with active fisheries was no different from that expected under a random distribution, but overlap with passive fisheries was significantly higher. This suggests that grey seals may be targeting the same areas as passive fisheries and/or specifically targeting passive gear. There was variation in foraging areas between individual seals suggesting habitat partitioning to reduce intra-specific competition or potential individual specialisation in foraging behaviour. Our findings support other recent assertions that seal/fisheries interactions in Irish waters are an issue in inshore passive fisheries, most likely at the operational and individual level. This suggests that seal population management measures would be unjustifiable, and mitigation is best focused on minimizing interactions at nets

Marine protected areas show low overlap with projected distributions of seabird populations in Britain and Ireland

EJC was funded by the Irish Petroleum Infrastructure Programme (PIP) IS013/08. WJG was funded by INSITE http://www.insitenorthsea.org/. AK was funded by the Irish Research CouncilGOIPD/2015/81. MJ was funded by the SFI Centre for Marine and Renewable Energy (12/RC/2302).Marine Protected Areas (MPAs) are an important tool for the conservation of seabirds. However, mapping seabird distributions using at-sea surveys or tracking data to inform the designation of MPAs is costly and time-consuming, particularly for far-ranging pelagic species. Here we explore the potential for using predictive distribution models to examine the effectiveness of current MPAs for the conservation of seabirds, using Britain and Ireland as a case study. A distance-weighted foraging radius approach was used to project distributions at sea for an entire seabird community during the breeding season, identifying hotspots of highest density and species richness. The percentage overlap between distributions at sea and MPAs was calculated at the level of individual species, family group, foraging range group (coastal or pelagic foragers), and conservation status. On average, 32.5% of coastal populations and 13.2% of pelagic populations overlapped with MPAs indicating that pelagic species, many of which are threatened, are likely to have significantly less coverage from protected areas. We suggest that a foraging radius approach provides a pragmatic and rapid method of assessing overlap with MPA networks for central place foragers. It can also act as an initial tool to identify important areas for potential designation. This would be particularly useful for regions throughout the world with limited data on seabird distributions at sea and limited resources to collect this data. Future assessment for marine conservation management should account for the disparity between coastal and pelagic foraging species to ensure that wider-ranging seabirds are afforded adequate levels of protection.PostprintPeer reviewe

Gannets are not attracted to fishing vessels in Iceland-potential influence of a discard ban and food availability

BLC was supported by a NERC GW4+ Doctoral Training Partnership studentship from the Natural Environment Research Council [NE/L002434/1]. We thank Ólafur Torfason, Niall Tierney, and Rachel Stroud for fieldwork assistance in Skrúður, and Mamma-Rósa for food and housing in Vestmannaeyjar. We thank the Hellisey hunting club for the use of cabin and assistance with boat trips to Hellisey. We thank Filipa Samarra, Miguel Neves, Gary Haskins, and team members in the Icelandic Orca Project for boat trips to Hellisey. We thank Lucy Hawkes, David Pascall, Alice Williams, Richard Phillips, Brendan Godley and all reviewers for constructive comments on the manuscript. The GPS tracking data are available through the BirdLife International Seabird Tracking Database (http://www.seabirdtracking.org).Peer reviewedPublisher PD

Using population viability analysis to examine the potential long-term impact of fisheries bycatch on protected species

Fisheries bycatch is recognised as the dominant anthropogenic threat facing many protected species globally. Estimates of total bycatch are often associated with wide confidence intervals as a result of limited coverage by on-board observers. This makes it difficult for managers to assess risk and design effective management plans. Here, we present a case study of grey seal (Halichoerus grypus) bycatch in static net fisheries across Irish waters, where potentially unsustainable bycatch levels have been reported with typically wide confidence intervals. We used Population Viability Analysis (PVA) to explore potential bycatch scenarios at a national level in order to inform future monitoring and management efforts; including (i) a baseline scenario where the probability of seals becoming bycaught was independent of age and sex; (ii) probability was biased towards juvenile, male, or female seals; (iii) there was net immigration of seals from outside of the national population; and (iv) colony-specific bycatch rates were applied to assess the relative vulnerability of the major grey seal breeding colonies to bycatch mortality. Results demonstrated that (i) higher levels of bycatch reduced population growth, with bycatch of 800 seals per year reducing the national population by 99% over 100 years; (ii) population viability was most sensitive to bycatch mortality of female seals, and more robust to juvenile or male mortality; (iii) recruitment of 500 seals per year prevented population decline despite a worst-case bycatch scenario of 800 seals bycaught per year; (iv) colonies in the south and southwest were the first to show signs of decline under increasing bycatch pressure. PVA provides a clear justification for improved monitoring of seal bycatch to obtain more precise bycatch estimates, and highlights the need for future studies to identify appropriate grey seal management units

Seabird movement reveals the ecological footprint of fishing vessels.

Exploitation of the seas is currently unsustainable, with increasing demand for marine resources placing intense pressure on the Earth's largest ecosystem [1]. The scale of anthropogenic effects varies from local to entire ocean basins [1-3]. For example, discards of commercial capture fisheries can have both positive and negative impacts on scavengers at the population and community-level [2-6], although this is driven by individual foraging behaviour [3,7]. Currently, we have little understanding of the scale at which individual animals initiate such behaviours. We use the known interaction between fisheries and a wide-ranging seabird, the Northern gannet Morus bassanus[3], to investigate how fishing vessels affect individual birds' behaviours in near real-time. We document the footprint of fishing vessels' (≥15 m length) influence on foraging decisions (≤11 km), and a potential underlying behavioural mechanism, by revealing how birds respond differently to vessels depending on gear type and activity. Such influences have important implications for fisheries, including the proposed discard ban [8]), and wider marine management

Central place foraging drives niche partitioning in seabirds

When species coexist, it is expected that they will reduce competition through niche partitioning or spatial segregation. We investigated the importance of niche partitioning versus spatial segregation across a seabird community where food and foraging constraints vary seasonally. Spatial clustering of seabird density in the western Irish Sea occurred in both seasons, with hotspots of seabird occurrence significantly higher in summer (Moran's I: 0.29) than winter (Moran's I: 0.19). A positive correlation between seabird density and feeding guild richness suggested a role for niche partitioning in reducing competition. This correlation was significantly stronger in summer than winter (Z-test, p < 0.05), suggesting that when foraging range is constrained during the breeding season, interspecific competition is reduced through increased niche partitioning. Reduced spatial clustering and weaker correlations between density and feeding guild richness in winter suggests that spatial segregation plays a greater role in reducing interspecific competition outside the breeding season. This study demonstrates the relative importance of niche partitioning and spatial segregation, highlighting niche partitioning as a response to constraints on foraging range during the breeding season