Inaction levels for the red imported fire ant, Solenopsis invicta (hym.: formicidae): A predator of the boll weevil, Anthonomus grandis (col.: curculionidae)

The density of red imported fire ants, Solenopsis invicta Buren (Hymenoptera: Formicidae), necessary to limit boll weevil abundance, Anthonomus grandis Boheman (Coleoptera: Curculionidae), below the action level was determined. An inaction level of 0.4 fire ants per shake bucket sample (i.e., four ants per 10 plant terminals) will provide boll weevil control approximately 90% of the time. A dynamic inaction level is also provided. Total mortality of boll weevil developmental stages including eggs through teneral adults averaged 97.9%. Of 100 boll weevil eggs deposited in cotton squares (flower buds), an average of two adults survive of which about half are female. Thus, the net replacement rate per generation (R_o is 1.0 which, in this case, indicates a stable boll weevil population.     

Fish in larger shoals find food faster

Summary Experiments on shoaling cyprinids hunting for food on patches in tanks demonstrate and advantage of foraging in a group. Individual goldfish (Carassius auratus) and minnows (Phoxinus phoxinus) in a shoal of conspecifics located food more rapidly as shoal size increased from 2 to 20. although shoaling minnows form polarised schools more readily than goldfish, which rarely do so, both species benefited from the trend of speedier food location with increasing group size.     

Stage-specific biomass overcompensation by juveniles in response to increased adult mortality in a wild fish population

Recently developed theoretical models of stage-structured consumer-resource systems have shown that stage-specific biomass overcompensation can arise in response to increased mortality rates. We parameterized a stage-structured population model to simulate the effects of increased adult mortality caused by a pathogen outbreak in the perch (Perca fluviatilis) population of Windermere (UK) in 1976. The model predicts biomass overcompensation by juveniles in response to increased adult mortality due to a shift in food-dependent growth and reproduction rates. Considering cannibalism between life stages in the model reinforces this compensatory response due to the release from predation on juveniles at high mortality rates. These model predictions are matched by our analysis of a 60-year time series of scientific monitoring of Windermere perch, which shows that the pathogen outbreak induced a strong decrease in adult biomass and a corresponding increase in juvenile biomass. Age-specific adult fecundity and size at age were higher after than before the disease outbreak, suggesting that the pathogen-induced mortality released adult perch from competition, thereby increasing somatic and reproductive growth. Higher juvenile survival after the pathogen outbreak due to a release from cannibalism likely contributed to the observed biomass overcompensation. Our findings have general implications for predicting population- and community-level responses to increased size-selective mortality caused by exploitation or disease outbreaks.     

The importance of local tree resources around Gombe National Park, Western Tanzania: implications for humans and chimpanzees

Miombo woodlands and associated habitats provide a vital resource for both humans and chimpanzees in western Tanzania. A baseline survey was conducted to determine the perceived relative value of different woody species to local people in the six villages adjacent to Gombe National Park. This area also provides direct comparison of tree utilization by humans and chimpanzees since it has been the site of a long-term behavioral study on chimpanzees. Four hundred and fifty-two people, all over 30 years old, were interviewed and asked to select the 10 trees that they considered to be the most important in their everyday lives: 77% of the 4520 responses (represented by 260 species) were native and 23% (represented by 35 species) were exotic trees. In this study, particular focus was paid to the 25 tree species most frequently listed. Of these trees, 19 (representing 50% of all responses) were native, and 6 were exotic. There was a marked difference in the choices, especially with respect to native trees, by men and women. Many of the trees highly prized by humans are also of great importance in the diet of chimpanzees. It is recommended that a major effort be made to maintain the usage and availability of native trees outside the park boundary, which, in conjunction with the balanced planting of exotics for meeting local needs, should contribute to protecting the biodiversity of Gombe and the local ethnobotanical heritage.     

How shell cleaned up a 400,000-gallon oil spill

On April 23, 1988, approximately 9,500 barrels (400,000 gallons) of San Joaquin Valley crude oil leaked from an aboveground storage tank at Shell Oil Company's Martinez Manufacturing Complex in Martinez, California and entered Suisun Bay, an important recreation area. This article describes the remediation techniques Shell used to protect and clean up the Bay's oiled marshes, sloughs, rocky shores, marinas, and sandy beaches, and discusses the main methods of oil spill response, site-specific factors that must be considered in choosing remediation techniques, the interaction between Shell and government agencies, and the costs associated with the spill. The cleanup's total cost was approximately $8.3 million, which did not include private claims and claims handling costs; Shell also signed a separate consent decree for $19.75 million with the state of California and the federal government. This spill and its aftermath emphasize the need for preparation that facilitates response actions, improves the chances for cooperation between responsible parties and government agencies, minimizes the time needed for remediation, lowers cleanup costs, and limits natural resource damage claims and penalties.     

Habitat related growth and reproductive investment in estuarine waters,illustrated for the tellinid bivalve <Emphasis Type="Italic">Macoma balthica</Emphasis> (L.) in the western Dutch Wadden Sea

In estuarine areas, bivalve species can be found in a variety of environments, where they experience large differences in environmental conditions. In the present paper, the importance of different habitats (intertidal, subtidal and adjacent coastal waters) for the persistence of the population was evaluated for the bivalve Macoma balthica (L.) in the western Dutch Wadden Sea estuary. Intra-specific variation in growth and reproductive output were followed during the year and related to local abiotic conditions. Significant differences in growth and reproductive investment were found between locations. Young individuals were mostly found in the intertidal area, where growth in terms of somatic mass was good. These areas were not favourable for adult individuals, since growth in shell length was low and many individuals did not reproduce. In the subtidal, where the highest densities were found, somatic and gonadal mass indices were low. Coastal areas had the lowest densities and showed high growth in terms of shell length and body mass. The habitat with the highest reproductive effort per individual was not the most important habitat in terms of reproductive output due to differences in density and in size of the habitat type. For M. balthica, the subtidal habitat contributed the most to the reproductive output of the western Dutch Wadden Sea population although the highest reproductive output per individual was in the coastal area.     

Gaseous Pollutants in St. Louis and Other Cities

During the fall of 1972, a study was undertaken to characterize gaseous air pollutants in the St. Louis metropolitan area. Information obtained in this study will be used in planning air pollution modeling studies to be carried out over the next 4 or 5 years under the Regional Air Pollution Study (RAPS) of the Environmental Protection Agency. From analyses of roadway samples, it was found that certain compounds in automotive emissions such as acetylene, carbon monoxide, o-xylene, ethylene, and 2-methylpentane occur in consistent proportions to other compounds. The concentrations of these indicator compounds in atmospheric samples were used to estimate the amounts of other hydrocarbons present that are attributable to automotive related emissions. Methane, ethane, and propane were found to originate principally from nonautomotive sources, both at St. Louis University and the St. Louis CAMP station. Similar concentrations were found in urban and non-urban areas. A comparison of ethylene-CO and propyl-ene-CO ratios in urban and non-urban areas indicates that CO can serve as an indicator of transport of urban pollutants. Sunlight irradiations of captured air samples showed increasing ozone production with increasing initial concentrations of hydrocarbons and nitrogen oxides. Substantial ozone and peroxyacetyl nitrate were formed from a total non-methane hydrocarbon concentration of only ¹/₄ ppm C.