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The sand tiger shark Carcharias taurus is a highly migratory coastal species with declining populations worldwide. This species exhibits many behaviors that make coastal sharks difficult to manage, including aggregatory behavior, sexual segregation, and large-scale migrations through shallow coastal waters with many opportunities for human interactions. Sand tigers from the Western North Atlantic subpopulation are known to seasonally inhabit Delaware Bay and surrounding coastal waters. This region has been recommended as a habitat area of particular concern for the Western North Atlantic sand tiger population, and increased understanding of their movements and habitat requirements will facilitate management efforts. We developed models to predict sand tiger occupancy using spatially dynamic environmental predictors. Our models predicted sand tiger (juveniles, adult males, adult females, and all sharks combined) occurrences in 2 study regions, the Delaware Bay and the western Mid-Atlantic coastal ocean. Sea surface temperature, day of year, water depth, and remote sensing reflectance at 555 nm were the most important environmental predictors of occurrence, and correctly predicted 80–89% of sand tiger acoustic telemetry records in the 2 study regions. Our models predicted differences in the timing and location of occurrences among juveniles and adults, as well as areas where these life history stages overlap in the Mid-Atlantic coastal ocean. Our hope is that a daily forecast of sand tiger occurrence from our modeling efforts could be useful for conservation and management efforts in this important region, as well as for studying the spatial and behavioral ecology of this important top predator.

Quantifying habitat selection in marine organisms is challenging because it is difficult to obtain species location information with multiple corresponding habitat measurements. In the ocean, habitat conditions vary on many spatiotemporal scales, which have important consequences for habitat selection. While macroscale biotic and abiotic features influence seasonal movements (spatial scales of 100–1000 km), selectivity of conditions on mesoscales (1–100 km) reflects an animal’s response to the local environment. In this study, we examined habitat selectivity by pairing acoustic telemetry with environmental habitat parameters measured by an autonomous underwater vehicle (AUV), and demonstrate that migrating sand tiger sharks Carcharias taurus along the East Coast of the USA did not randomly use the coastal environment. Of the variables examined, we found evidence to suggest that sand tigers were selecting their habitat based on distance to shore, salinity, and colored dissolved organic matter (CDOM). Notably, temperature was not predictive of habitat use in our study. We posit that during their coastal migration, sand tigers select for specific mesoscale coastal habitats that may inform navigation or feeding behaviors. To our knowledge, this is the first empirical measure of mesoscale habitat selection by a coastal marine organism using an AUV. The applications of this method extend beyond the habitat selectivity of sand tigers, and will prove useful for future studies combining in situ observations of marine habitats and animal observations.

1. Rapid agricultural change in western Europe has occurred in the last three decades, at cost to farmland biodiversity, particularly birds. This study reviewed agricultural change in Denmark from 1983 to 2001, to compare patterns of intensification and farmland bird abundance with the UK. 2. Changes in 26 agricultural variables summarized using principal components analysis (PCA) showed consistent changes throughout the period that were similar to the UK. Pig and sheep production, and the extent of winter cereals, rape and fodder maize, all increased. The area used to grow fodder beet and spring barley, the applications of agrochemicals and the numbers of cattle reared all declined. The greatest change in land area in Denmark was the switch from spring- to autumn-sown cereals in the 1980s, almost a decade later than in the UK. 3. PCA described changes in annual indices of bird abundance based on Danish point count surveys from 1983 to 2001, which were most marked during 1983-90, after which ordination values varied little despite continued agricultural change. Of 27 bird species associated with farmland habitat in Denmark, five declined, 10 showed stable trends and 12 increased, compared with 15, eight and four, respectively, among the same species in the UK. 4. Agricultural yields have been sustained or enhanced during the survey period, while most farmland bird species declining in the UK have remained stable or increased in Denmark. Of the five declining Danish species, only lapwing Vanellus vanellus and yellowhammer Emberiza citrinella are associated with predominantly farmland habitat. The timing of the declines suggests that the switch to autumn sowing in Denmark has had little effect on any species. 5. In contrast to the UK, pesticide and inorganic fertilizer use has declined and organic farming has expanded in Denmark since 1983, coinciding with the period of stability/increase in farmland bird abundance. It is not possible to establish any causality from this analysis. 6. The ability of species showing marked declines in Europe to maintain their number and distribution in the Danish landscape in the face of agricultural intensification gives some optimism for safeguarding farmland birds and biodiversity in the future. However, we need to understand the reasons behind contrasting population trends in Denmark and the UK. 7. Synthesis and applications. Marked differences between national patterns of agriculture and the contrasting nature of historical intensification offer the opportunity to contrast the effects of major changes in land-use practice on European farmland biodiversity. Appropriate comparative and individual studies of the effects of changes in specific agricultural management at greater spatial (i.e. supranational) scales are necessary in order to underpin the successful development of future European agricultural policies that will sustain and enhance agricultural yields whilst maintaining farmland biodiversity.

1. Based on studies of effects of hunting disturbance on local waterbird distribution and abundance, freedom from such disturbance is concluded to be an important part of waterbird management on nature conservation areas. Measures to mitigate the effects of disturbance from hunting are reviewed. These include complete removal of hunting in refuges, as well as spatial and temporal regulation of hunting activity in reserve areas outwith hunting-free refuges. 2. Disturbance-free refuge design should take account of the ecological requirements of all species using a site and the functional units required to meet all daily activities, especially primary feeding and roosting areas used by waterbirds. Refuge size and shape must ensure birds are free from the effects of external disturbance. The most effective are of regular shape, maximum practicable size, and as a minimum should have a diameter of three times the escape flight distance of the most sensitive species present. 3. Zoning in non-refuge areas can increase local bird numbers by restricting disturbance to regular predictable stimuli to which habituation is more likely. Mobile hunting activity close to roosting and/or feeding areas is more disturbing than hunting from fixed points or where birds are shot moving between such areas. Intermittent hunting is not an effective means of minimizing disturbance, but where implemented rest periods between hunting events should be considered in weeks rather than days. 4. Most studies of mitigation techniques to minimize hunting disturbance have been descriptive and retrospective. Manipulative studies testing specific hypotheses are essential to create a sound scientific base for management. 5. Management of hunting activity should take place within a broader management planning framework that identifies ideal and operational objectives in the management of the site, including feedback monitoring to determine the effectiveness of management prescriptions. 6. We recommend that local site management planning should be integrated internationally, especially in the planning of refuge networks along migration corridors. Management actions in one part of a flyway may affect the ability of areas elsewhere to meet obligations to biodiversity conservation and maintenance of range under international law. In populations that are limited by winter resources, creation of a refuge network may offer a mechanism to enhance population size, but more large scale density dependence studies are required to confirm this.

Fish diets play a critical role in our understanding of aquatic trophic dynamics and are an important component in developing ecosystem-based approaches to fisheries management. Although large nektonic fishes exert top-down predator effects on the food web and typically support viable commercial and recreational fisheries, little is known about the diet of this guild. We evaluated the diets (6327 stomachs) of four nektonic predatory fishes (Pomatomus saltatrix [78–395 mm], Cynoscion regalis [91–520 mm], Morone americana [156–361 mm], and Morone saxatilis [82–785 mm]) in Delaware Bay and in the adjacent ocean. To assess ontogenetic, geographic, and interspecific variation in diets, observations from individual fish stomachs were clustered into species-size class groups, and dietary overlap was estimated using multivariate analyses. A shift in diet composition, as well as diversity, occurred along the estuarine gradient and into the adjacent ocean. Some prey were shared by most predators, including some crustaceans (dominated by Callinectes sapidus, mysids, and Palaemonetes spp.), fundulids (dominated by Fundulus heteroclitus), engraulids (dominated by Anchoa mitchilli), and clupeids (dominated by Brevoortia tyrannus). However, inter- and intra-specific variation in diet was observed as well. In particular, M. americana consumed fewer engraulids and clupeids, and many more and diverse types of invertebrates, while P. saltatrix consumed more clupeids and less invertebrates. The lack of overlap in diet between the four predators evaluated, and between size groups for each predator, supports previous evidence that these groups feed in trophic guilds defined by species and by size within a species. The highly variable diets for these predators suggest high resolution spatial data are necessary in order to quantify their most important prey and their role in coastal ecosystems.

We analysed barnacle Branta leucopsis and pink-footed goose Anser brachyrhynchus summer diets (May–July 2003) based on the proportions of different plant constituents in the faecal material of adult breeding birds in Sassendalen, Svalbard to assess potential inter-specific competition. Diets were highly restricted and overlapped little during pre-nesting and post hatch. During incubation both species showed greatest variety in their diet, reflecting site-specific differences in local food abundance. However, locally the diets of pink-footed and barnacle geese resembled each other most at this time (although still differing significantly). The conflicting needs of nest defence and maintenance of body condition constrains the extent of the feeding resource utilised by nesting pairs and explains slightly greater dietary overlap at this time. Hence, there is little evidence of inter-specific competition (interference or depletion) at present, but this is most likely to be manifest during the incubation period in the future if goose numbers continue to increase. More detailed investigations of the degree of spatial overlap of the two species and their effects on plant structure, quality and community composition are necessary to predict likely outcomes of expected increases in numbers of both goose species.

Partial migration, by which contingents within populations undertake divergent migrations, is common in marine fishes but remains poorly documented. Intrapopulation groups of fish with similar seasonal migration behaviors were noted early in the fisheries literature and have attracted increased interest for their role in population resilience to environmental change and fishing. Here, we used acoustic telemetry to test historical hypotheses on contingent structure for striped bass Morone saxatilis in the Hudson River, New York (USA), which harbors one of the largest populations of this species. Season and region of release were used as design elements to evaluate 3 principal contingents. In total, 51 implanted striped bass were detected in New York Harbor (NYH), Hudson River, and other estuarine and coastal receiver arrays from June 2010 through December 2011. Multivariate analyses of >500 000 recoveries confirmed predictions of 3 broad contingent behaviors, viz. those that principally utilized (1) the Upper Hudson River Estuary, (2) the NYH and Lower Hudson River Estuary, and (3) coastal waters, but commingled in upper Hudson River spawning habitats during late spring. All contingents occupied NYH, but their transit routes into and out of the harbor varied significantly. Further behavioral diversity was observed within contingents, including size-specific differential migration, multiple natal origins (natal divergence), and non-annual (skipped) spawning. Contingent structure within Hudson River striped bass likely distributes the influences of regional fisheries, pollution, and other environmental forces, promoting stability and persistence in the overall population.

Modification and reductions in flows are reducing inundation times in some Yangtze River wetlands, potentially affecting the growth of submerged macrophytes. The effects of shortening the inundation period from April to October (control) to April to September (treatment) were tested on the production of surface and below-ground tubers and fruits in individual Vallisneria spinulosa ramets in microcosm experiments. Mean numbers of below-ground tubers produced did not differ significantly between treatments, but individual tuber dry mass was significantly greater when harvested in October compared with plants harvested in September. Significantly more surface tubers were initiated by the ramets in the later harvest, but these did not differ in dry mass. Fewer ramets had initiated sexual reproduction by the September harvest compared with the October harvest. Almost all October fruits were mature, while the ratio of mature to unripe fruits was significantly greater than in September. There was no support for the hypothesis that more tubers were initiated deeper in the substrate with a longer inundation period to avoid predation by fish or birds. Based on these results, shortening of the inundation periods experienced by Vallisneria spinulosa plants in Yangtze River ephemeral wetlands may reduce the dry biomass of below-ground tubers and the production of surface tubers in this keystone macrophyte. La modification et la réduction des débits réduisent les temps d’inondation dans certaines zones humides du fleuve Yangtsé, affectant potentiellement la croissance des macrophytes submergés. Les effets de la réduction de la durée de l’inondation d’avril à octobre (contrôle) à avril à septembre (traitement) ont été testés sur la production de tubercules de surface et souterrains et les fruits dans les différents ramets de Vallisneria spinulosa par des expériences en microcosmes. Le nombre moyen de tubercules souterrains produits ne diffère pas significativement entre les traitements, mais la masse sèche de tubercule était significativement plus élevée lors de la récolte en octobre par rapport aux plantes récoltées en septembre. Significativement plus de tubercules de surface étaient formés par les ramets lors de la récolte tardive, mais ceux-ci ne diffèrent pas en masse sèche. Peu de ramets avaient entamé une reproduction sexuée lors de la récolte de septembre par rapport à celle d’octobre. Presque tous les fruits en octobre étaient matures et la proportion des fruits mûrs était significativement plus élevée qu’en septembre. Rien ne confirme l’hypothèse que plus de tubercules ont été formés plus profondément dans le substrat avec une longue période d’inondation pour éviter la prédation par les poissons ou les oiseaux. Sur la base de ces résultats, le raccourcissement des périodes d’inondation rencontrées par les plantes Vallisneria spinulosa dans les zones humides temporaires de la rivière Yangtsé peut réduire la biomasse sèche des tubercules souterrains et la production de tubercules de surface chez ce macrophyte clé.

Trace element and 87Sr/86Sr isotope analyses of fish pectoral fin rays offer non-destructive methods for determining habitat use. In this study, water and fin ray samples were analyzed for Gulf Sturgeon Acipenser oxyrinchus desotoi from the Choctawhatchee River Basin (FL and AL, USA) and compared with reference samples from Atlantic Sturgeon A. o. oxyrinchus held at controlled salinities (0, 10, 33 ppt). Samples were analyzed using inductively coupled plasma mass spectrometry, with a multi-collector for 87Sr/86Sr. In water, Sr, Ba, Mn and Zn differed between freshwater and saline habitats, with increases in Sr and decreases in Ba, Mn and Zn. 87Sr/86Sr decreased upstream to downstream with lowest values in saline habitats. In the reference study, water trace element concentrations and 87Sr/86Sr corresponded to those in pectoral fin rays. 87Sr/86Sr was higher in pectoral fin ray than water, due to influence of diet, which differed with salinity. In wild fish, trace elements in pectoral fin rays indicated freshwater emigration to saline habitats primarily occurred in the second to third growth zone with some heterogeneity in the population (4% <0.3 years, 39% 0.5–1.3 years, 39% 1.5–2.3 years, 17% 2.5–3.3 years). Analyses of 87Sr/86Sr indicated initial locations of Gulf Sturgeon were in the middle river, with few fish in the upper or lower river. Most (74%) juvenile Gulf Sturgeon utilized more than one river region prior to freshwater emigration and 48% moved upstream temporarily based on increased 87Sr/86Sr. After initial freshwater emigration, fish utilized lower-river to saline habitats. Collectively, these studies demonstrate the usefulness of trace element and 87Sr/86Sr analyses in sturgeon pectoral fin rays.

1. This study examined the nitrogen balance of free-living flightless moulting Greylag Geese, Anser anser, in relation to food quality, nitrogen absorption, food retention time and nitrogen excretion rates. 2. Food intake rates during moult were the same as those before and after the flightless period, but total daily time spent foraging fell by 58% from 9.45 h to 3.96 h. Dropping production during moult was 43%, and mean dropping mass 42% of that before and after moult, suggesting a considerable increase in food passage time through the gut during moult. Nitrogen absorption increased from 25% prior to moult to 47% during moult. 3. At the same time, excreted dry mass uric acid in faecal material fell by 68%, such that the proportion of nitrogen absorbed and retained in the body as a proportion of the nitrogen ingested in food rose from 16% prior to moult to 42% during moult. 4. Based on these significant increases in nitrogen absorption and decreases in nitrogen excretion, geese were able to compensate for reduced food intake and derive sufficient nitrogen from their diet to re-grow flight feathers.