The occurrence of Oratosquilla investigatoris (Crustacea: Stomatopoda) in the pelagic zone of the Gulf of Aden and the equatorial western Indian Ocean

Surface swarms of the stomatopod Oratosquilla investigatoris (Lloyd, 1907) were observed in the Gulf of Aden and the equatorial western Indian Ocean during 1967. Collections from inshore and offshore swarms were made in both areas, and from demersal trawl catches in the equatorial area. O. investigatoris was also collected from the stomachs of several species of oceanic pelagic and inshore fish from 1965 to 1967, and was also reported in the stomach contents of the lesser frigate bird. Further collections were made from strandings on two oceanic islands in the equatorial area. Indirect observations on the occurrence of the species resulted from increased predation on pelagic longline baits during seasos of apparent abundance of O. investigatoris in the equatorial region. At the surface, predation by the species was observed on fast-swiming fish, and the swimming behaviour was noted. A size range of 6 to 37 mm carapace length (CL) was recorded for the 4000 specimens collected, and there was no size difference between the sexes. Length-frequency analysis of the samples indicated a major mode at 19 to 21 mm CL and an increase in length of 3 mm over 3 months. The sex ratio was weighted in favour of females in the majority of collections. It was concluded that the pelagic swarming of O. investigatoris is an important ecological phenomenon, but not regular in the area, and the factors affecting it could not be deduced from the available data.     

Patterns and selectivity in the feeding of certain mesopelagic fishes

Stomach contents were analysed from the 7 most numerous species of mesopelagic fish caught in a series of 11 hauls over a 24 h period at 230 to 266 m depth in the eastern North Atlantic Ocean. The numerical abundance of organisms per filled stomach and the frequency of occurrence of empty stomachs were used to indicate feeding periodicity. The ecological significance of the feeding periodicity was considered by examining it in connection with an investigation of the day-night vertical distribution of zooplankton and micronekton to 2000 m at the same station. Additional dietary evidence on the 7 species considered was also obtained from the vertical series. Feeding selectivity was examined by comparing the composition of the zooplankton population, sampled separately but simultaneously with the micronekton, with that from the overall stomach contents of the species examined. Feeding periodicity was demonstrated for 6 species, of which 3 were found to be feeding selectively: Valenciennellus tripunctulatus on calanoid copepods, Argyropelecus aculeatus on ostracods, and Lampanyctus cuprarius on amphipods and possibly euphausiids. The limited data available on the other 3 species suggested that they were either random feeders (A. hemigymnus and Lobianchia dofleini) or perhaps selecting against a particular group (Notolychnus valdiviae). No indication of feeding periodicity or selectivity was found for Chauliodus danae. The overall pattern of results confirmed the supposed close correlation between vertical migration and feeding in mesopelagic fish.     

Restoring acidified streams in upland Wales: a modelling comparison of the chemical and biological effects of liming and reduced sulphate deposition

Increasing emphasis is being placed on the restoration of surface waters which have been affected by acidification. Amongst the possible strategies are management of the causes, by reducing acidic deposition, and management of the symptoms, by treating affected areas with basic material such as limestone. In few cases have there been comparisons of the likely effect of these two strategies on surface water chemistry and ecology, although there is widespread belief that the two are similar in outcome. At present, only a modelling approach permits such a comparison. This paper describes chemical and biological responses of three Welsh streams whose catchments were limed experimentally in 1987-1988 as part of the Llyn Brianne project. Actual changes are compared with simulated changes which occur following reduced acid deposition according to the hydrochemical model, MAGIC (Model of Acidification of Groundwaters in Catchments). The results indicate that liming and 90% reduction in sulphate deposition reduce concentrations of toxic aluminium to similar levels. However, calcium concentrations and pH were increased by liming to values which were high by comparison with conditions simulated at low acid deposition, either in the past or future. Trout density increased in two of the streams following liming to levels similar to those simulated under low acid deposition. By contrast, the aquatic invertebrate fauna changed after liming so that streams acquired species typical of higher calcium concentrations than those simulated under low acid deposition. Species characteristic of 'soft water' communities were apparently lost, although more data are required to separate treatment effects from random change in the longer term. The 'soft water' community also declined in the model as a result of acidification, indicating that both liming and acid deposition resulted in a different faunal community from that prior to acidification. The results support those who conclude that liming is suitable for the restoration or protection of a fishery, but indicate that there may be other ramifications, for example to conservation, which must be considered when liming is implemented. However, the simulation of biological conditions under low acid deposition involves extrapolation from the initial data base. Further data are now required to assess empirically the likely biological character of British streams which have low base cation concentrations unaffected by acid deposition.     

A Strategy for the Evaluation of Sensory and Pulmonary Irritation Due to Chemical Emissions from Indoor Sources

Abstract

Sensory and pulmonary irritation are physiological responses to chemical exposure which result in characteristic, measurable changes in respiratory activity in mice. A standard method has been applied to the estimation of sensory irritation associated with a specific chemical exposure. This method has been correlated with human responses to these chemicals. Symptoms associated with chemical irritants are consistent with complaints due to problems with indoor air quality, which may include eye and upper respiratory tract irritation, headaches, and nausea. A stepwise strategy for assessing the contribution of indoor products to sensory and pulmonary irritation is discussed in the current paper. The strategy includes product emissions testing using dynamic environmental chambers, the selection of suspected irritants for respiratory irritation testing, respiratory irritation testing of individual compounds and representative mixtures using synthesized atmospheres, and the evaluation of test data to determine those compounds which may contribute to sensory and pulmonary irritation in humans. The current strategy is being applied to evaluate carpet system materials and their constituent chemicals.