Ontogenetic and sex-specific differences in density-dependent habitat selection of a marine fish population

The spatial dynamics of species are the result of complex interactions between density-independent and density-dependent sources of variability. Disentangling these two sources of variability has challenged ecologists working in both terrestrial and aquatic ecosystems. Using a novel spatially explicit statistical model, we tested for the presence of density-independent and density-dependent habitat selection in yellowfin sole (Limanda aspera) in the eastern Bering Sea. We found specificities in the density-dependent processes operating across ontogeny and particularly with gender. Density-dependent habitat expansion occurred primarily in females, and to a lesser degree in males. These patterns were especially evident in adult stages, while juvenile stages of both sexes exhibited a mix of different dynamics. Association of yellowfin sole with substrate type also varied by sex and to a lesser degree with size, with large females distributed over a wider range of substrates than males. Moreover, yellowfin sole expanded northward as cold subsurface waters retracted in summer, suggesting high sensitivity to arctic warming. Our findings illustrate how marginal habitats can play an important role in buffering density-dependent habitat expansion, with direct implications for resource management. Our spatially explicit modeling approach is effective in evaluating density-dependent spatial dynamics, and can easily be used to test similar hypotheses from a variety of aquatic and terrestrial ecosystems.     

A Bayesian assessment of the effect of highway bypasses in Iowa on crashes and crash rate

Introduction

A common contention is that the construction of highway bypasses negatively impacts the economy of local communities by reducing pass-by traffic for businesses. However, as access to specific business' account records is limited, this impact is difficult to quantify. Another common contention is that bypasses contribute to a reduction in overall crashes in the community and in the surrounding areas. Even though a large number of bypasses have been constructed in the State of Iowa over the past several years, their actual impact in terms of traffic safety has not been quantified.

Objectives

This study seeks answers to the following questions: (a) Are bypasses in Iowa associated with a reduction in crash frequencies and crash rates on the bypassed highway? (b) Do bypasses in Iowa introduce a reduction of overall crash frequencies and rates or do they merely shift crashes from the highways through the communities to the bypasses with no significant overall reduction?

Method

We obtained crash information from the Iowa DOT at 19 sites on which a bypass was constructed sometime during the past 23 years. We also obtained the same information at six sites used as comparison sites on which no bypasses were constructed at least until 2005. We them employed a Bayesian approach to estimating the association between the construction of the bypass and crash rates, while also accounting for other factors.

Results

The construction of bypasses in Iowa is associated with a significant increase in traffic safety both on the main road through town and on the combined main road and bypass roadway.     

Worldwide cases of water pollution by emerging contaminants: a review

Environmental Chemistry Letters - Water contamination by emerging contaminants is increasing in the context of rising urbanization, industrialization, and agriculture production. Emerging...     

Spatial anatomy of species survival: effects of predation and climate-driven environmental variability

The majority of survival analyses focus on temporal scales. Consequently, there is a limited understanding of how species survival varies over space and, ultimately, how spatial variability in the environment affects the temporal dynamics of species abundance. Using data from the Barents Sea, we study the spatiotemporal variability of the juvenile Atlantic cod (Gadus morhua) survival. We develop an index of spatial survival based on changes of juvenile cod distribution through their first winter of life (from age-0 to age-1) and study its variability in relation to biotic and abiotic factors. Over the 25 years analyzed (1980-2004), we found that, once the effect of passive drift due to dominant currents is accounted for, the area where age-0 cod survival was lowest coincided with the area of highest abundance of older cod. Within this critical region, the survival of age-0 cod was negatively affected by its own abundance, by that of older cod, and by bottom depth. Furthermore, during cold years, age-0 cod survival increased in the eastern and coldest portion of the examined area, which was typically avoided by older conspecifics. Based on these results we propose that within the examined area top-down mechanisms and predation-driven density dependence can strongly affect the spatial pattern of age-0 cod survival. Climate-related variables can also influence the spatial survival of age-0 cod by affecting their distribution and that of their predators. Results from these and similar studies, focusing on the spatial variability of survival rates, can be used to characterize species habitat quality of marine renewable resources.     

Integrating intraseasonal grassland dynamics in cross-scale distribution modeling to support waterbird recovery plans

Despite much discussion about the utility of remote sensing for effective conservation, the inclusion of these technologies in species recovery plans remains largely anecdotal. We developed a modeling approach for the integration of local, spatially measured ecosystem functional dynamics into a species distribution modeling (SDM) framework in which other ecologically relevant factors are modeled separately at broad scales. To illustrate the approach, we incorporated intraseasonal water-vegetation dynamics into a cross-scale SDM for the Common Snipe (Gallinago gallinago), which is highly dependent on water and vegetation dynamics. The Common Snipe is an Iberian grassland waterbird characteristic of European agricultural meadows and a member of one of the most threatened bird guilds. The intraseasonal dynamics of water content of vegetation were measured using the standard deviation of the normalized difference water index time series computed from bimonthly images of the Sentinel-2 satellite. The recovery plan for the Common Snipe in Galicia (northwestern Iberian Peninsula) provided an opportunity to apply our modeling framework. Model accuracy in predicting the species’ distribution at a regional scale (resulting from integration of downscaled climate projections with regional habitat–topographic suitability models) was very high (area under the curve [AUC] of 0.981 and Boyce's index of 0.971). Local water-vegetation dynamic models, based exclusively on Sentinel-2 imagery, were good predictors (AUC of 0.849 and Boyce's index of 0.976). The predictive power improved (AUC of 0.92 and Boyce's index of 0.98) when local model predictions were restricted to areas identified by the continental and regional models as priorities for conservation. Our models also performed well (AUC of 0.90 and Boyce's index of 0.93) when projected to updated water-vegetation conditions. Our modeling framework enabled incorporation of key ecosystem processes closely related to water and carbon cycles while accounting for other factors ecologically relevant to endangered grassland waterbirds across different scales, allowed identification of priority areas for conservation, and provided an opportunity for cost-effective recovery planning by monitoring management effectiveness from space.     

Geophysical and hydrological data assimilation to monitor water content dynamics in the rocky unsaturated zone

In recent years, geophysics is increasingly used to study the flow and transport processes in the vadose zone. Particularly, when the vadose zone is made up of rocks, it is difficult to install sensors in the subsurface to measure hydrological state variables directly. In these cases, the electrical resistivity tomography (ERT) represents a useful tool to monitor the hydrodynamics of the infiltration and to estimate hydraulic parameters and state variables, such as hydraulic conductivity and water content. We propose an integrated approach aimed at predicting water content dynamics in calcarenite, a sedimentary carbonatic porous rock. The uncoupled hydrogeophysical approach proposed consists in 4D ERT monitoring conducted during an infiltrometer test under falling head conditions. Capacitance probes were installed to measure water content at different depths to validate the estimations derived from ERT. A numerical procedure, based on a data assimilation technique, was accomplished by combining the model (i.e., Richards’ equation) with the observations in order to provide reliable water content estimations. We have used a new data assimilation method that is easy to implement, based on the ensemble Kalman filter coupled with Brownian bridges. This approach is particularly suitable for strongly non-linear models, such as Richards’ equation, in order to take into account both the model uncertainty and the observation errors. The proposed data assimilation approach was tested for the first time on field data. A reasonable agreement was found between observations and predictions confirming the ability of the integrated approach to predict water content dynamics in the rocky subsoil.     

Armaments and ornaments in the rock sparrow: a possible dual utility of a carotenoid-based feather signal

Females often base their mating preferences on male sexual secondary traits that are used to settle contests among males. Such traits are likely to be honest indicators of male quality if they are constantly used during costly male–male agonistic interactions. Carotenoid signals have been shown to work as a handicap because they are costly to produce. However, the role of carotenoids as “honest” signals during male contests is less clear, and it is not known whether a carotenoid-based trait can serve in both male–male competition and female choice. In this study, we studied the dual function of a carotenoid feather ornament in the rock sparrow (Petronia petronia), a bird species in which both sexes have a yellow throat patch whose size positively correlates with phenotypic measures. First, we investigated, in a field study, whether the size of a male’s yellow patch correlates with his ability to acquire a territory. Second, we tested the signal function of the yellow patch in two male–male interaction in captivity experiments. Finally, we measured female preference for males differing in throat patch size in a mate choice experiment. Our experiments revealed that the size of a male’s throat patch positively correlated with the number of nest boxes he was able to defend. Moreover, in controlled conditions, males with relatively large yellow patches had earlier access to food than those with small patches. Also, in an experiment in which a dummy rock sparrow with an experimentally manipulated yellow patch was positioned near a feeder, latency to feed by focal birds positively correlated with dummy patch size. Lastly, in a dichotomous mate choice experiment, females showed a proximity preference for males whose patch was experimentally enlarged. Taken together, these results suggest that the same carotenoid feather signal may be used in both male–male competition and female choice in this passerine bird.     

Foraging impact on zooplankton by age-0 walleye pollock (<Emphasis Type="Italic">Theragra chalcogramma</Emphasis>) around a front in the southeast Bering Sea

The waters around the Pribilof Islands in the southeast Bering Sea are a center of abundance for age-0 walleye pollock (Theragra chalcogramma). Each spring and summer a tidal front is formed around the islands separating a well-mixed inshore habitat from a stratified offshore habitat. The objective of this study was to assess the foraging impact on zooplankton by age-0 pollock in the vicinity of this frontal structure. A bioenergetic model was used to estimate age-0 pollock food consumption from field estimates of water temperature, age-0 pollock density, diet and growth. Sampling of field variables took place over three hydrographic habitats along an inshore–offshore transect located north of the islands. The bioenergetics analysis was applied for a 2-week period during the late summer of four consecutive years, 1994–1997. Model results of age-0 pollock food consumption indicated variable levels of food depletion, changing with prey type, year and habitat. The foraging impact of age-0 pollock on copepods and euphausiids (most common prey) ranged from about 3% to 77% of the biomass available at the start of the simulation. Copepod depletion was typically greater than euphausiid depletion. Consequently, juvenile pollock <60 mm in standard length were more likely to experience food limitation due to the greater proportion of copepods in their diet. We present evidence of severe foraging impact during 1996, when one of the primary prey items of juvenile pollock (i.e. large copepods) was scarcely represented both in their diet and in the water column. In all years, most instances of prey depletion were found at the inshore and front habitats; age-0 pollock densities were too low relative to their prey to severely impact the offshore zooplankton populations. We discuss these results with respect to modeling assumptions and in the context of previously acquired knowledge of fish behavior around frontal regions.Communicated by T. Ikeda, Hakodate     

Goal striving,idiosyncratic deals,and job behavior

Two important gaps remain to be filled in the idiosyncratic deals (i‐deals) literature. First, it is unclear which employees are predisposed to seek and receive i‐deals. Second, it is unclear how employees' perceptions of whether their coworkers are receiving i‐deals affect their own i‐deal experiences. This study proposed a theoretical model suggesting that (a) three key motivational goals identified in human development research, that is, achievement, status, and communion striving, predispose employees to seek and receive i‐deals; (b) employees' perceptions of whether their coworkers are receiving i‐deals moderate these relationships; and (c) employees' i‐deals are related to their job behavior. Data collected from more than 400 working adults in Italy showed that employees' motivational goals (particularly achievement and status striving) were positively related to the levels of i‐deals they received, and that these i‐deals were in turn positively related to supervisors' assessments of their in‐role job performance, voice behavior, and interpersonal citizenship behavior. High perceptions of the extent to which coworkers received i‐deals further strengthened the relationship between status striving and employees' perceptions of their own i‐deals, highlighting a trait‐situation interactionist perspective on employees' i‐deal experiences. Copyright © 2015 John Wiley & Sons, Ltd.     

Bioaccumulation of metals in common carp (<Emphasis Type="Italic">Cyprinus carpio</Emphasis> L.) from water bodies of Anatolia (Turkey): a review with implications for fisheries and human food consumption

Although fish is widely consumed by humans for its nutritional properties, accumulation of heavy metals can pose serious health hazards. Widespread common carp Cyprinus carpio is cultured worldwide and represents an economically important species for fisheries in several countries. These include Turkey, where C. carpio often makes for a large part of the sales of the locally marketed fish and also for a traditional dish. This study provides a review of bioaccumulation of metals in tissues of C. carpio from water bodies of Anatolia and also includes reference to worldwide studies. From 42 water bodies across the region, 27 metals in total were studied, of which Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn were the most widely analysed, mainly in the muscle, liver and gill tissues. Amongst the potentially toxic metals, Cd, Cr and Pb occurred in several water bodies at concentrations not only above maximum allowed limits but also higher relative to other water bodies worldwide, even though As, Hg and Ni were also sometimes present at potentially hazardous concentrations. The essential metals Cu, Fe, Mn, Se and Zn were detected at various concentrations, with the latter two occasionally above limit. All water bodies flagged as having especially critical (i.e. above limit) concentrations of toxic metals supported C. carpio fisheries from highly populated regions, raising concern about food safety and calling for preventative measures. Given the significantly lower bioaccumulation levels in the muscle relative to the liver and gill tissues, it is suggested that consumption of C. carpio as fillets may be safer than after processing into e.g. meat balls and sausages. The limits of 1.0 μg/g for Cr and 1.15 μg/g for Se, currently lacking from the Turkish food safety legislation, are proposed, and it is suggested that a similar meta-analytical approach as adopted in this study may benefit other countries where C. carpio represents an important fisheries resource.