A multi-event model to study stage-dependent dispersal in radio-collared hares: when hunting promotes costly transience

Behavioral ecologists have often assumed that dispersal is costly mainly because of unfamiliarity with traversed habitats during dispersal and energy costs of the movement per se; thus, dispersers that have successfully settled should experience survival rates comparable to those of philopatric individuals. In this paper, we tested that hypothesis using 152 radio-collared European hares in a harvested population. We developed a multi-event capture recapture model, combining telemetry data and recoveries and separately modeling the foray probability, the settlement probability, and the permanent dispersal probability. The parameterization introduced here raises the possibility of separately testing effects on survival and dispersal probabilities at each stage of dispersal (departure, transience, and settlement). In accordance with our expectations, we reveal that dispersers incur higher mortality risks during transience and the early settlement period than philopatric individuals or settled dispersers. We also found that dispersers suffer from higher risks of being shot. Those results illustrate that unfamiliarity with the habitat during transience makes dispersal costly and that settled dispersers may enjoy survival rates comparable to those of philopatric individuals. Surprisingly, we also found that individuals have a higher probability of foraying during the hunting season. We suggest that hunting and related disturbances increase dispersal costs both by increasing mortality risk during transience and (perhaps) by increasing movement rates. We emphasize the need to take human pressures into account as factors that may drive the demographics of movements in populations.     

Historical processes constrain patterns in global diatom diversity

There is a long-standing belief that microbial organisms have unlimited dispersal capabilities, are therefore ubiquitous, and show weak or absent latitudinal diversity gradients. In contrast, using a global freshwater diatom data set, we show that latitudinal gradients in local and regional genus richness are present and highly asymmetric between both hemispheres. Patterns in regional richness are explained by the degree of isolation of lake districts, while the number of locally coexisting diatom genera is highly constrained by the size of the regional diatom pool, habitat availability, and the connectivity between habitats within lake districts. At regional to global scales, historical factors explain significantly more of the observed geographic patterns in genus richness than do contemporary environmental conditions. Together, these results stress the importance of dispersal and migration in structuring diatom communities at regional to global scales. Our results are consistent with predictions from the theory of island biogeography and metacommunity concepts and likely underlie the strong provinciality and endemism observed in the relatively isolated diatom floras in the Southern Hemisphere.     

Fishing the line near marine reserves in single and multispecies fisheries.

Throughout the world "fishing the line" is a frequent harvesting tactic in communities where no-take marine reserves are designated. This practice of concentrating fishing effort at the boundary of a marine reserve is predicated upon the principle of spillover, the net export of stock from the marine reserve to the surrounding unprotected waters. We explore the consequences and optimality of fishing the line using a spatially explicit theoretical model. We show that fishing the line: (1) is part of the optimal effort distribution near no-take marine reserves with mobile species regardless of the cooperation level among harvesters; (2) has a significant impact on the spatial patterns of catch per unit effort (CPUE) and fish density both within and outside of the reserve; and (3) can enhance total population size and catch simultaneously under a limited set of conditions for overexploited populations. Additionally, we explore the consequences of basing the spatial distribution of fishing effort for a multispecies fishery upon the optimality of the most mobile species that exhibits the greatest spillover. Our results show that the intensity of effort allocated to fishing the line should instead be based upon more intermediate rates of mobility within the targeted community. We conclude with a comparison between model predictions and empirical findings from a density gradient study of two important game fish in the vicinity of a no-take marine-life refuge on Santa Catalina Island, California (USA). These results reveal the need for empirical studies to account for harvester behavior and suggest that the implications of spatial discontinuities such as fishing the line should be incorporated into marine-reserve design.     

Winter food utilisation by sympatric mysids in the Baltic Sea,studied by combined gut content and stable isotope analyses

We studied the winter dietary characteristics of two sympatric mysid species, Mysis mixta and M. relicta, which exploit both benthic and pelagic habitats during diel vertical migrations. Samples collected before and after the ice-covered period in the northern Baltic Sea were investigated using both stomach content analyses and stable isotope analyses of carbon and nitrogen. Both of the mysid species were omnivorous during winter and utilised both benthic and pelagic food sources. The main food source before the ice period was calanoid copepods (40 and 36% for M. mixta and M. relicta, respectively), and after ice-out calanoid copepods (23%) and zooplankton resting eggs (23%) for M. mixta and diatoms (44%) and calanoids (25%) for M. relicta. Their patterns of food utilisation broadly followed seasonal fluctuations in the abundance of the main prey groups. Although pelagic food availability is low in winter both mysid species utilised pelagic prey widely. We also show that when combining these different diet analysis methods it is important to take into account the time lag in isotopic signatures, otherwise the obtained results do not correspond but instead show the feeding history at different times.     

Amelioration of acute mercury toxicity by a novel,non-toxic lipid soluble chelator N,N′bis-(2-mercaptoethyl)isophthalamide: effect on animal survival,health, mercury excretion,and organ accumulation

The toxic effects of mercury are known to be complex with specific enzyme inhibitions and subsequent oxidative stress adding to the damaging effects. There are likely other factors involved, such as the development of impaired metal ion homeostasis and depletion of thiol- and selenium-based metabolites such as cysteine and selenium. Much of the toxicity of mercury occurs at the intracellular level via binding of Hg²⁺ to thiol groups in specific proteins. Therefore, amelioration of mercury toxicity by the use of chelation would likely be enhanced by the use of a chelator that could cross the cell membrane and the blood brain barrier. It would be most favorable if this compound was of low toxicity, had appropriate pharmacokinetics, bound and rendered mercury cation non-toxic and had antioxidant properties. Herein we report on such a chelator, N,N′-bis(2-mercaptoethyl)isophthalamide (NBMI), and, using an animal model, show that it prevented the toxic effects associated with acute exposure induced by injected mercury chloride.     

Dike-break induced flows: a simplified model

A simplified model for the prediction of the steady-state outflow through a breach in an inland dike is presented. It consists in the application of the mass and momentum conservation principles to a macroscopic control volume. A proper definition of the shape of the control volume enables to take the main characteristics of the flow into account and thus to compensate for the extreme simplification of the spatial representation of the model. At the breach, a relation derived from the shallow-water equations is used to determine the direction of the flow. Developments have been guided by numerical simulations and results have been compared to experimental data. Both the accuracy and the domain of validity of the simplified model are found satisfactory.     

The role of research institutions in seed-related disaster relief: Seeds of Hope experiences in Rwanda

The article describes the efforts of a coalition of agricultural research centres, Seeds of Hope (SOH) in the rebuilding, of Rwanda, after the genocide and war of 1994. Research involvement in emergency relief and rehabilitation was unusual at the time and SOH had to forge its unique complementary role. Focusing on crop and variety development and conservation it: provided technical advice to relief agencies on seed procurement; used its baseline ken to assess the effects of war on seed diversity and seed security; made preparations to restore specific germplasm (which, fortunately, proved unnecessary) and spent substantial effort on rebuilding human resource capacity in research as well as basic scientific facilities. The involvement of SOH highlighted the critical, yet very different, roles for research during emergency versus rehabilitation periods and demonstrated the cost effectiveness of building in a diagnostic component--before massive seed or germplasm distributions are programmed.     

Successful intrauterine shunting of a sacrococcygeal teratoma (SCT) causing fetal bladder obstruction

We report a case of a sacrococcygeal teratoma (SCT) diagnosed at 22 weeks with a substantial intrapelvic cystic extension leading to bladder outlet obstruction and hydronephrosis at 27 weeks. Prenatal percutaneous shunting of the cystic teratoma was performed at 28 weeks to avoid prolonged fetal pelvic compression by the tumour that could have adverse effects by stretching the pelvic plexus and sacral nerves. Urinary dilatation resolved completely after shunting and a 3880 g baby girl was delivered at 39 weeks. The potential benefits of in utero shunting to avoid urological complications of SCTs with intrapelvic extension are discussed. Copyright © 2001 John Wiley & Sons, Ltd.     

Infiltration of acetochlor and two of its metabolites in two contrasting soils

To obtain data concerning the risk of leaching of acetochlor (2-chloro-2'-methyl-6'-ethyl-N-ethoxymethyl-acetanilide) and its major metabolites, ethanesulfonic acid (ESA) and oxanilic acid (OA), to ground water, we studied the fate of these products in two different soil types (luvisol and calcisol) under the same weather conditions. The metabolites were detected in the soils as early as 7 d after application, indicating a rapid onset of acetochlor degradation. Ethanesulfonic acid was predominant over OA in the calcisol, regardless of time or depth, whereas the ESA to OA ratio varied with both time and depth in the luvisol. The maximum depths at which they were detected were 60 to 70 and 10 to 20 cm for ESA and OA, respectively, in the luvisol, and 60 to 70 cm (maximum depth sampled) and 30 to 40 cm for ESA and OA, respectively, in the calcisol. Acetochlor was still detected in the surface layer of the two soils 344 d after its application, although the molecule was partially leached. The maximum depths at which acetochlor was detected (60-70 cm in the luvisol and 50-60 cm [maximum depth sampled] in the calcisol) were recorded during the first sampling 7 d after application. Acetochlor was not detected on later dates below the 30- to 40-cm layer in the calcisol or the 5- to 10-cm layer in the luvisol. The greater preferential flow in the luvisol, which would have favored leaching, might partially explain why the mass balances done 7 d after application were lower in the luvisol (approximately 26%) than in the calcisol (approximately 45%).     

Persistence of the De-Icing Additive Benzotriazole at an Abandoned Airport

The environmental fate of many of the additives in the deicing agents used at airports is poorly understood. One and two years after deicing activities ceased, soil and groundwater samples were taken at an abandoned airport. Benzotriazole (BT), a corrosion and flame inhibitor, was found in low concentrations in soils along runways (mean 0.33 mg/kg), at a snow disposal site (0.66 mg/kg), as well as in sediments of a drainage ditch (13 mg/kg). Locally, high BT concentrations were found in the groundwater below the deicing pad, the regeneration plant and the snow disposal site (1.2 to 1100 g/l). Methyl substituted triazoles or tolytriazoles (MeBT) were found in concentrations less than 10% of the BT concentration. Propylene glycol was not detected in soil samples and in only one of the groundwater samples. Microtox tests of the water samples revealed no acute toxic response, however a reduction in nitrification rate was observed (14–43%). The nitrification response could not be related directly to the BT concentration in the samples, although samples with a high BT concentration showed the largest reduction in nitrification rate. BT showed very little sorption in various soil matrices, only peat and compost with a high organic carbon content showed significant sorption. Sorption could be best described using a Freundlich isotherm. These results indicate a high mobility and possibly long persistence of BT in soil and groundwater, which may be attributed to the absence of microbial degradation of BT.