Overlap Values Research Articles

Feeding habits of three round stingrays (Rajiformes: Urotrygonidae) in the central Mexican Pacific

Stomach contents and dietary overlap of three round stingray species (Urobatis halleri, Urotrygon munda, and Urotrygon rogersi) captured off the central Pacific coast of Mexico were analyzed during the two main hydroclimatic periods (T1 and T2) that characterize the environmental variability in the area. The three round stingray species showed a narrow bathymetric distribution range, and the highest abundances were located at 20 m depth in both seasons. In general, the diets were mainly composed of benthic microcrustaceans (caridean shrimps) and to a lesser extent of fishes, polychaetes, and molluscs. The most abundant prey items in the diets were carideans of the families Processidae and Ogyriididae, and penaeids, followed by brachyuran and stomatopod larvae. All three stingrays exhibited a generalist feeding strategy. The diets showed high overlap values during period T1 in both inter- and intraspecies analyses, but lower values during period T2. There was no evidence of ontogenetic diet changes and sex was not a factor for trophic differences. The slight differences among diets were due to seasonal changes in the soft-bottom macrobenthic invertebrate assemblages in the shallow waters, and relationships like predation and competition were not the main factors influencing the population dynamics of the three stingray species.

CFD Analysis of Flow Physics and Aerodynamic Performance of a Combined Three-Bucket Savonius and Three-Bladed Darrieus Turbine

In this paper, the performance of a combined three-bucket Savonius and three-bladed Darrieus turbine was analyzed computationally by using Fluent 6.2 CFD software. Two-dimensional steady-state CFD simulations were performed for without overlap, and with five overlaps namely 16.2%, 20%, 25%, 30%, and 35%. The flow physics of the combined turbine was analyzed with the help of pressure, velocity and vorticity contours. Further, the aerodynamic coefficients were evaluated with respect to angle of attack for various tip speed ratios. It was concluded that the power augmentation of the combined turbine occurred for low overlap in Savonius turbine due to high aerodynamic lift-to-drag coefficient of the Savonius turbine, caused by the increase of dynamic pressure from bucket-vortex interactions on the concave face of the returning bucket. And it also occurred for high aerodynamic lift-to-drag coefficient (14.5) of the Darrieus turbine from the increase of velocity difference across the Darrieus blade with small overlap (16.2%) in Savonius turbine. For without or with low overlap (16.2%), coanda flow occurred across the overlap between the inner edge of bucket and the central shaft that migrated from the downstream side of the advancing bucket towards the upstream side and then reached the concave face of the returning bucket increasing dynamic pressure on it, and hence augmented power production for the combined turbine. However, high value of overlap (20% onwards) caused vortex separations from the inner edges of bucket destabilizing the coanda flow for which the aerodynamic coefficients were lowered.

Effects of an experimentally clumped food resource on raccoon Procyon lotor home‐range use

AbstractSome species of carnivores fluctuate between a primarily solitary lifestyle and a group‐living lifestyle, depending on resource availability. Understanding the ontogeny of this transition requires analyzing changes in space use. We analyzed radio‐telemetry data from 41 adult raccoons Procyon lotor to assess the influence of an experimentally maintained clumped food source on spatial structure. We compared home‐range size, two‐dimensional overlap and volume of intersection (VI) values between 22 raccoons with access to the clumped food resource and 19 raccoons on an adjacent control site that received similar food quantities, but for which food was distributed in a non‐clumped and spatially‐temporally unpredictable pattern. No between‐sex differences in home‐range size occurred within either food site, nor did differences in home‐range size occur between the two sites. However, the experimental‐site animals had two‐dimensional home‐range overlap values and volume of intersection (VI) scores that were nearly twice those of raccoons inhabiting the control site. These differences appear to be driven by increased overlap among females from the experimental site, as males from the two treatment sites had similar home‐range overlap and VI scores. Collectively, these results indicate that the distribution of resources can significantly change the extent of spatial overlap among individuals, even when the mean home‐range size of the population does not change. This further suggests that while a site's overall resource availability influences population size, the spatial clumping of resources facilitates the formation of local aggregations.

Trophic interactions among sympatric zooplanktivorous fish species in volume change conditions in a large, shallow, tropical lake

Significant reductions in the water volume of shallow lakes impose a restriction on species segregation promoting more interactions in the trophic relationships. The diets of three closely related zooplanktivorous silversides belonging to the Atherinopsidae species flock of lake Chapala , Mexico, were analyzed at two sites (Chirostoma jordani, C. labarcae, and C. consocium). Diets were described in critical shallow (August 2000) and volume recovery conditions (August 2005). Diets included mainly cladocerans (Bosmina, Ceriodaphnia, and Daphnia) and copepods (Cyclops). A significant difference in diets was detected when comparing years (MRPP analysis, A = 0.22, p < 0.0001) and sites at different years (MRPP analysis, A = 0.17, p = 0.004). According to niche breadth mean values, species were classified as specialized and intermediate feeders. In shallow conditions, the small range of niche breadth (1.72 to 3.64) and high diet overlap values (D = 0.64, L = 8.62) indicated a high potential for interspecific exploitative interaction. When the lake volume recovered, an increase in the niche breadth range (1.04 to 4.96) and low niche overlap values (D = 0.53, L = 2.32) indicated a reduction of the species interaction. The Mann-Whitney U-test supported this pattern by showing a significant difference between years for niche overlap (p = 0.006). The increased interaction during the low volume suggests alternative segregation in life-history variations and other niche dimensions such as spatial or temporal distribution.

Cryptic biodiversity and phylogenetic relationships revealed by DNA barcoding of Oriental black flies in the subgenusGomphostilbia(Diptera: Simuliidae)

Understanding the medical, economic, and ecological importance of black flies relies on correct identification of species. However, traditional taxonomy of black flies is impeded by a high degree of morphological uniformity, especially the presence of cryptic biodiversity, historically recognized by details of chromosomal banding patterns. We assess the utility of DNA barcoding, based on cytochrome c oxidase subunit 1 (COI) sequences, for identifying 13 species of Oriental black flies in the subgenus Gomphostilbia. Samples of larvae fixed in Carnoy's solution were used to gather molecular and chromosomal data from the same individual. We found that larvae refrigerated in Carnoy's fixative for as long as 11 years can be used for DNA study. Levels of intraspecific genetic divergence, based on the Kimura-2 parameter, range from 0% to 9.28%, with a mean of 2.75%, whereas interspecific genetic divergence ranges from 0.34% to 16.05%. Values of intraspecific and interspecific genetic divergence overlap in seven species owing to incomplete lineage sorting and imperfect taxonomy, implying that DNA barcoding to identify these species will be ambiguous. Despite a low level of success, we found that DNA barcoding is useful in revealing cryptic biodiversity, potentially facilitating traditional taxonomy. Phylogenetic analyses indicate that species groups currently recognized on morphological criteria are not monophyletic, suggesting a need to reevaluate the classification of the subgenus Gomphostilbia.

Patterns of niche breadth and feeding overlap of the fish fauna in the seasonal Brazilian Pantanal, Cuiabá River basin

Spatial and temporal variations in patterns of niche breadth and feeding overlap were investigated for the fish fauna in the Pantanal region, aiming to determine the factors that account for species coexistence. Samples were conducted in the Cuiabá River and Chacororé pond, in the upper Pantanal region, Mato Grosso State, Brazil, during one hydrological cycle (March 2000 to February 2001), (designed spatial-seasonal units). Mean niche breadth values were overall low for the fish assemblage (0.2-0.3). Differences between periods were not statistically significant. Feeding overlap values ranged between 0 and 0.4, whereas the mean was always inferior to 0.05 in all spatial-temporal units, and differences between periods were not statistically significant. The highest and lowest mean values were both observed in the pond; the former during the drought period and the latter during the flood period. All feeding overlap mean values were significantly higher than the values expected at random in the null model, using both "scrambled-zeros" (RA3) and "conserved-zeros" (RA4) algorithms. Thus, the foraging patterns show evidences of food sharing. The variance generated in the null model had a pattern similar to the niche overlap pattern: observed variance was higher than expected by chance in all spatial-temporal units, suggesting that the fish fauna is structured in trophic guilds. The patterns of food resource use and the different trophic guilds identified, suggest that species probably have different roles in this ecosystem. Our results suggest that food sharing allows coexistence of different fish species.

Sources of variability and comparability between salmonid stomach contents and isotopic analyses: study design lessons and recommendations

We compared sources of variability and cost in paired stomach content and stable isotope samples from three salmonid species collected in September 2001–2005 and describe the relative information provided by each method in terms of measuring diet overlap and food web study design. Based on diet analyses, diet overlap among brown trout, rainbow trout, and mountain whitefish was high, and we observed little variation in diets among years. In contrast, for sample sizes n ≥ 25, 95% confidence interval (CI) around mean δ15Ν and δ13C for the three target species did not overlap, and species, year, and fish size effects were significantly different, implying that these species likely consumed similar prey but in different proportions. Stable isotope processing costs were US$12 per sample, while stomach content analysis costs averaged US$25.49 ± $2.91 (95% CI) and ranged from US$1.50 for an empty stomach to US$291.50 for a sample with 2330 items. Precision in both δ15Ν and δ13C and mean diet overlap values based on stomach contents increased considerably up to a sample size of n = 10 and plateaued around n = 25, with little further increase in precision.

Feeding Ecology of Blue Marlins, Dolphinfish, Yellowfin Tuna, and Wahoos from the North Atlantic Ocean and Comparisons with other Oceans

AbstractWe examined diet, dietary niche width, diet overlap, and prey size–predator size relationships of blue marlins Makaira nigricans, dolphinfish Coryphaena hippurus, yellowfin tuna Thunnus albacares, and wahoos Acanthocybium solandri caught in the western North Atlantic Ocean during the Big Rock Blue Marlin Tournament (BRT) in 1998–2000 and 2003–2009 and dolphinfish captured outside the BRT from 2002 to 2004. Scombrids were important prey of blue marlins, yellowfin tuna, and wahoos; other frequently consumed prey included cephalopods (for yellowfin tuna and wahoos) and exocoetids (for yellowfin tuna). Dolphinfish diets included exocoetids, portunids, and conspecifics as important prey. Blue marlins and wahoos consumed relatively few prey species (i.e., low dietary niche width), while dolphinfish had the highest dietary niche width; yellowfin tuna had intermediate niche width values. Maximum prey size increased with dolphinfish size; however, the consumption of small prey associated with algae Sargassum spp. occurred across the full size range of dolphinfish examined. Most interspecific diet overlap values with dolphinfish were not significant; however, blue marlins, yellowfin tuna, and wahoos had significant diet overlap due to their reliance on scombrid prey. Prey types found in blue marlins, dolphinfish, and wahoos were more consistent among BRT years than prey found in yellowfin tuna. The prey of yellowfin tuna and wahoos collected during BRT years correlated with historic (early 1980s) diet data from North Carolina, the Gulf of Mexico, and the Bahamas. Based on principal components analysis, diets from several oceans clustered together for blue marlins, dolphinfish, yellowfin tuna, and wahoos. Although differences were found, the diets of each predator were largely consistent both temporally (e.g., over the past three decades in the Gulf Stream) and spatially (among oceans), despite potential effects of fishing or environmental changes.

Assessment of multiple task activation and reproducibility in patients with benign and low-grade neoplasm.

Twenty-four patients with proven benign and low-grade brain neoplasms each performed two iterations of four fMRI paradigms: language (word generation), primary and association auditory (text listening), upper limb fine motor control (alternating-limb bilateral finger tapping), and primary visual perception (reversing checkerboard). Activation clusters with varying thresholds were generated for each scan and used to calculate reproducibility parameters: Difference in the Center of Mass (COM) location, R(size), and R(overlap). The average difference in the COM, R(size), and R(overlap) values ranged from 1.70 +/- 0.53 mm -10.60 +/- 3.21 mm, 0.6 +/- 0.04-0.90 +/- 0.05 and 0.23 +/- 0.12 -1 +/- 0.16 respectively for all tasks. These values are within the range of, or higher than, previously published reports on fMRI test-retest precision. FMRI is indicated to be a noninvasive tool with acceptable reproducibility measures for assessing the localizations of multiple language and sensorimotor functions in patients scheduled for radiotherapy treatment.

Accounting for Individuals, Uncertainty, and Multiscale Clustering in Core Area Estimation

Core areas are important descriptors of animal space-use patterns, but current estimation methods rely on arbitrary rules and potentially lead to imprecise or erroneous area estimates. We proposed a Bayesian statistical model that incorporates an individual-based method for estimating core area boundaries. The model accounts for boundary uncertainty and multiple scales of clustering by partitioning a home range into ≥2 completely spatially random point patterns defined by a kernel density isopleth. We used data from coyotes (Canis latrans), bobcats (Lynx rufus), and red-shouldered hawks (Buteo lineatus) to estimate core areas for individual animals. We also estimated core areas from simulated point patterns with known boundaries, varying numbers of points, and relative densities of points inside core areas, and compared estimates to those obtained using the 50% isopleth. Optimal isopleths for the empirical data ranged between 18.7% and 71.5%. We found no species-specific range of core area isopleths. Across all simulated scenarios, our method outperformed the 50% isopleth-based estimate, which consistently overestimated core areas. Minta overlap values were 20–40% higher across all scenarios for our method compared to the 50% isopleth. Minta overlap values were >75% in 90% of scenarios using our method. Objectively estimating core areas using our individual-based method may lead to improved inference about which behavioral and ecological processes underlie observed space-use patterns because of greater estimate precision.

Accounting for Individuals, Uncertainty, and Multiscale Clustering in Core Area Estimation

Abstract: Core areas are important descriptors of animal space‐use patterns, but current estimation methods rely on arbitrary rules and potentially lead to imprecise or erroneous area estimates. We proposed a Bayesian statistical model that incorporates an individual‐based method for estimating core area boundaries. The model accounts for boundary uncertainty and multiple scales of clustering by partitioning a home range into ≥2 completely spatially random point patterns defined by a kernel density isopleth. We used data from coyotes (Canis latrans), bobcats (Lynx rufus), and red‐shouldered hawks (Buteo lineatus) to estimate core areas for individual animals. We also estimated core areas from simulated point patterns with known boundaries, varying numbers of points, and relative densities of points inside core areas, and compared estimates to those obtained using the 50% isopleth. Optimal isopleths for the empirical data ranged between 18.7% and 71.5%. We found no species‐specific range of core area isopleths. Across all simulated scenarios, our method outperformed the 50% isopleth‐based estimate, which consistently overestimated core areas. Minta overlap values were 20–40% higher across all scenarios for our method compared to the 50% isopleth. Minta overlap values were >75% in 90% of scenarios using our method. Objectively estimating core areas using our individual‐based method may lead to improved inference about which behavioral and ecological processes underlie observed space‐use patterns because of greater estimate precision.

A Method for the Comparison of Item Selection Rules in Computerized Adaptive Testing

In a typical study comparing the relative efficiency of two item selection rules in computerized adaptive testing, the common result is that they simultaneously differ in accuracy and security, making it difficult to reach a conclusion on which is the more appropriate rule. This study proposes a strategy to conduct a global comparison of two or more selection rules. A plot showing the performance of each selection rule for several maximum exposure rates is obtained and the whole plot is compared with other rule plots. The strategy was applied in a simulation study with fixed-length CATs for the comparison of six item selection rules: the point Fisher information, Fisher information weighted by likelihood, Kullback-Leibler weighted by likelihood, maximum information stratification with blocking, progressive and proportional methods. Our results show that there is no optimal rule for any overlap value or root mean square error (RMSE). The fact that a rule, for a given level of overlap, has lower RMSE than another does not imply that this pattern holds for another overlap rate. A fair comparison of the rules requires extensive manipulation of the maximum exposure rates. The best methods were the Kullback-Leibler weighted by likelihood, the proportional method, and the maximum information stratification method with blocking.

Assessing biogeographical relationships of ecologically related species using favourability functions: a case study on British deer

AbstractAim Using six free‐living deer species in Great Britain as a case study, we studied biogeographical relationships of ecologically related species composed of both native and introduced species.Location Great Britain.Methods We modelled the environmental favourability for the deer species using variables related with spatial location, climate, topography, human disturbances and habitat structure. Favourability values of each pair of native (naturalized)‐introduced species were used to estimate the fuzzy overlap index (FOvI) as a measure of overall similarity between the environmental requirements for the species in Great Britain. The absolute local overlap values (FOvI‐L) were also used to measure the degree to which a given location was favourable simultaneously for each pair of species. We assessed the trends of species favourability across a range defined by the absolute local overlap values and studied the shape of the obtained curves since they informs us about the favourability balance between the studied species.Results Muntjac and Chinese water deer attained higher favourability values than native species in localities with intermediate values of FOvI‐L (a reduced number in the study area), suggesting that if competitive relationships were established in these localities the introduced deer species may have some advantages over natives. Sika deer only achieved higher values than fallow deer in those localities clearly unfavourable for the naturalized species. Our analyses predicted that fallow deer will be less affected by the introduced deer species than native species.Main conclusions We developed an approach based on the favourability function to describe biogeographical relationships between species, natives and introduced and to assess from a biogeographical perspective if introduced species could pose a competitive risk to natives. Although the results of present analyses do not conclusively demonstrate competitive exclusion, they provide directional hypotheses that can be tested in experimental field and laboratory studies.

Lithium isotopes in Guatemalan and Franciscan HP–LT rocks: Insights into the role of sediment-derived fluids during subduction

High-pressure, low-temperature (HP–LT) rocks from a Cretaceous age subduction complex occur as tectonic blocks in serpentinite mélange along the Motagua Fault (MF) in central Guatemala. Eclogite and jadeitite among these are characterized by trace element patterns with enrichments in fluid mobile elements, similar to arc lavas. Eclogite is recrystallized from MORB-like altered oceanic crust, presumably at the boundary between the down-going plate and overlying mantle wedge. Eclogite geochemistry, mineralogy and petrography suggest a two step petrogenesis of (1) dehydration during prograde metamorphism at low temperatures (<500 °C) followed by (2) partial rehydration/fertilization at even lower T during exhumation. In contrast, Guatemalan jadeitites are crystallized directly from low- T aqueous fluid as veins in serpentinizing mantle during both subduction and exhumation. The overall chemistry and mineralogy of Guatemalan eclogites are similar to those from the Franciscan Complex, California, implying similar P– T– x paths. Li concentrations (⩽90 ppm) in mineral separates and whole rocks (WR) from Guatemalan and Franciscan HP–LT rocks are significantly higher than MORB (4–6 ppm), but similar to HP–LT rocks globally. Li isotopic compositions range from −5‰ to +5‰ for Guatemalan HP–LT rocks, and −4‰ to +1‰ for Franciscan eclogites, overlapping previous findings for other HP–LT suites. The combination of Li concentrations greater than MORB, and Li isotopic values lighter than MORB are inconsistent with a simple dehydration model. We prefer a model in which Li systematics in Guatemalan and Franciscan eclogites reflect reequilibration with subduction fluids during exhumation. Roughly 5–10% of the Li in these fluids is derived from sediments. Model results predict that the dehydrated bulk ocean crust is isotopically lighter (δ 7Li ⩽ +1 ± 3‰) than the depleted mantle (∼+3.5 ± 0.5‰), while the mantle wedge beneath the arc is the isotopic complement of the bulk crust. A subduction fluid with an AOC–GLOSS composition over the full range of model temperatures (50–600 °C) gives an average fluid δ 7Li (∼+7 ± 5‰ 1 σ) that is isotopically heavier than the depleted mantle. If the lowest temperature steps are excluded (50–260 °C) as too cold to participate in circulation of the mantle wedge, then the average subduction fluid (δ 7Li = +4 ± 2.3‰ 1 σ, is indistinguishable from depleted mantle. Because of the relatively compatible nature of Li in metamorphic minerals, the most altered part of the crust (uppermost extrusives), may retain a Li isotopic signature (∼+5 ± 3‰) heavier than the bulk crust. The range of Li isotopic values for OIB, IAB and MORB overlap, making it is difficult to resolve which of these components may contribute to the recycled component in the mantle using δ 7Li alone.

Packing spherical discrete elements for large scale simulations

We introduce a new geometric method to generate sphere packings with restricted overlap values. Sample generation is an important, but time-consuming, step that precedes a calculation performed with the discrete element method (DEM). At present, there does not exist any software dedicated to DEM which would be similar to the mesh software that exists for finite element methods (FEM). A practical objective of the method is to build very large sphere packings (several hundreds of thousands) in a few minutes instead of several days as the current dynamic methods do. The developed algorithm uses a new geometric procedure to position very efficiently the polydisperse spheres in a tetrahedral mesh. The algorithm, implemented into YADE-OPEN DEM (open-source software), consists in filling tetrahedral meshes with spheres. In addition to the features of the tetrahedral mesh, the input parameters are the minimum and maximum radii (or their size ratio), and the magnitude of authorized overlaps. The filling procedure is stopped when a target solid fraction or number of spheres is reached. Based on this method, an efficient tool can be designed for DEMs used by researchers and engineers. The generated packings can be isotropic and the number of contacts per sphere is very high due to its geometric procedure. In this paper, different properties of the generated packings are characterized and examples from real industrial problems are presented to show how this method can be used. The current C++ version of this packing algorithm is part of YADE-OPEN DEM [20] available on the web ( https://yade-dem.org).

Information exchange networks for chronic illness care in primary care practices: an observational study

BackgroundInformation exchange networks for chronic illness care may influence the uptake of innovations in patient care. Valid and feasible methods are needed to document and analyse information exchange networks in healthcare settings. This observational study aimed to examine the usefulness of methods to study information exchange networks in primary care practices, related to chronic heart failure, diabetes and chronic obstructive pulmonary disease.MethodsThe study was linked to a quality improvement project in the Netherlands. All health professionals in the practices were asked to complete a short questionnaire that documented their information exchange relations. Feasibility was determined in terms of response rates and reliability in terms of reciprocity of reports of receiving and providing information. For each practice, a number of network characteristics were derived for each of the chronic conditions.ResultsTen of the 21 practices in the quality improvement project agreed to participate in this network study. The response rates were high in all but one of the participating practices. For the analysis, we used data from 67 health professionals from eight practices. The agreement between receiving and providing information was, on average, 65.6%. The values for density, centralization, hierarchy, and overlap of the information exchange networks showed substantial variation between the practices as well as between the chronic conditions. The most central individual in the information exchange network could be a nurse or a physician.ConclusionsFurther research is needed to refine the measure of information networks and to test the impact of network characteristics on the uptake of innovations.

Binding of Small-Molecule Inhibitors To MAP Kinase ERK2, Studied with Resonance Energy Transfer (RET)

The extracellular-signal-regulated kinase (ERK) proteins belong to the mitogen-activated protein kinase family. They participate in several important cell-signaling pathways. Unregulated, ERK2 is thought to mediate cell proliferation in many types of cancer. But because ERK also functions in many normal cell activities, inhibition selectivity is necessary for its use in cancer therapy: one needs to block only phosphorylation of those substrates that are involved in cell proliferation, while leaving phosphorylation of other substrates unaffected. Novel small-molecule compounds, which inhibit phosphorylation of selected substrates but do not compete with ATP for its binding site, have been previously identified by computer-aided drug design (CADD) and molecular-dynamics docking algorithms. Herein, we spectroscopically characterized selected compounds, and show that they can serve as resonance energy transfer (RET) acceptors for tryptophan: we determined the values of spectral overlap J between the compounds' absorption and ERK fluorescence, and of the Forster distance R0 for the compound/tryptophan pairs. We then used RET to determine average distances between the bound compounds and the group of three tryptophans in ERK2, thus validating the CADD predictions of the compounds' binding sites. The problem of multiple but closely located donors (tryptophans) that pass the energy to the single acceptor (the bound compound) is discussed, as is the possibility of utilizing RET for mapping the inhibitor-binding sites on other kinases. The novel RET acceptors for tryptophan can conceivably be employed in studies of other protein/ligand systems with suitable spectroscopic properties.

Effects of Striped Bass Stocking on Largemouth Bass and Spotted Bass in Lewis Smith Lake, Alabama

AbstractIntroductions of striped bass Morone saxatilis into U.S. reservoirs have caused concern among anglers that target other species owing to the perception that this predator reduces the number of other sport fish and can limit available prey supplies. Recently, this controversy arose in Lewis Smith Lake (8,583 ha), Alabama, prompting this study to examine the effects of stocking striped bass on the resident population of black bass Micropterus spp. From October 2006 to August 2007, the diets of striped bass, largemouth bass M. salmoides, and spotted bass M. punctulatus were examined in this reservoir. The density and biomass of striped bass and black bass were computed from estimates of age‐0 black bass abundance, striped bass stocking rates, growth, and survival. Bioenergetics models were used to estimate striped bass and black bass consumptive food demands. Striped bass diets (by weight) were dominated by shad Dorosoma spp. (64%), followed by crayfish Oronectes spp. (12%), while black bass and sunfish Lepomis and crappies Pomoxis spp. comprised 5% and 6% of the diet, respectively. Numerically, sunfish–crappies and black bass only comprised 0.28% and 0.16% of the diets of striped bass. The diets of largemouth bass and spotted bass (by weight) were dominated by crayfish (72% and 75%, respectively) and sunfish–crappies (21% and 9%, respectively), while shad comprised 6% and 14% of the diets, respectively. Diet overlap values between striped bass and black bass were generally low but varied seasonally among species. The highest overlap between the diets of striped bass and black bass was observed in April and June. However, the relative weights of black bass did not decline or the frequency of empty stomachs among these species did not increase during or after this time. Overall, consumptive prey demand was similar between striped bass and black bass. Bioenergetics modeling estimated striped bass consumption of shad, bass–sunfish–crappies, and crayfish averaging 14, 3, and 5 kg/ha, respectively, compared with 3, 6, and 16 kg/ha, respectively, for black bass. Shad consumption by striped bass and black bass (relative to the total annual supply) was within acceptable levels. Striped bass consumption of black bass was low, striped bass and black bass partitioned prey resources, and the temporal differences in maximum consumptive demand varied between black bass and striped bass. Thus, we found that the impact of striped bass stocking on the black bass population was minimal.

Composición y superposición de dietas en cuatro especies de Diplectrum (Perciformes: Serranidae) en el Pacífico central mexicano

Analysis of diet composition and overlap in four species of the genus Diplectrum (Perciformes: Serranidae) in the Mexican Central Pacific. The information of trophic interactions among species is essential to understand ecosystem function. To assess this in four Diplectrum species, we analyzed the stomach contents of 397 individuals caught using shrimp trawling nets off the coasts of Jalisco and Colima, Mexico. Main food component of D. eumelum were fish of the Order Pleuronectiformes, followed by shrimps (Metapenaeopsis spp). D. euryplectrum feeds mainly on crustaceans, with stomatopods (Squilla mantoidea) as main food items followed by shrimps and brachyurans. Fish and polychaetes had a low representation in the diet of this species. D. labarum feeds mainly on crustaceans, mollusks and fish. The stomatopod Eurysquilla veleronis contributed to with a high diet percentage by weight, followed by shrimps (mostly Solenoceraflorae) and brachyurans, as well as the squid Lolliguncula diomedae. Fishes (Ophidion spp.) were also an important component of the diet of this species. The most common preys of D. rostrum were crustaceans, mollusks, polychaetes and fish. The squid Lolliguncula diomedae and fishes of genus Ophidion were also well represented in the diet. Diet breadth index yielded significant differences between species. The number of diet items varied from 16 in D. euryplectrum to 6 in D. eumelum. The average value of overlap (0.247) was not significantly different (p = 0.118) from the expected one for a null model (0.174). The observed variance of the overlap index (0.071) was significantly higher (V = 0.025, p = 0.0004) than the value expected for a null model.

AAM Segmentation of the Mandible and Brainstem

The 2009 MICCAI Head and Neck Auto-Segmentation Challenge was aimed at assessing algorithms for automated segmentation of the brain stem and mandible from CT images for use in radiotherapy planning. The organisers provided 10 datasets with associated manual segmentations by experts, and 8 test datasets on which the algorithms had to be run. In two of the test datasets (subjects 13 and 15) the field of view was truncated. The results were independently analysed by the organisers.To address the problem posed by the challenge we describe a method based on active appearance models (AAMs) which involves four stages: Initialisation with a parts-and-geometry model, search with a global AAM followed by search with local AAMs, then post-processing using linear regressors.Application of the method to the test images resulted in a mean (excluding subject 13) Dice overlap value of 76.1 +/- 5.1% for the mandible, and 72.9 +/- 24.6% for the brainstem. The method failed to segment both the mandible and brainstem in subject 13, and the whilst giving a successful segmentation of the mandible in subject 15, gave poor results on the brainstem. It takes about 10 minutes to run on a 64 bit Linux workstation with 2GB RAM, and a 2GHz pentium processor. We were encouraged by its performance on this dataset, and believe that its accuracy can be improved with some modifications to the segmentation pipeline.