Feeding behavior of the Atlantic mackerel Scomber scombrus on the hydromedusa Aglantha digitale

Under laboratory conditions, the Atlantic mackerel Scomber scombrus feed on Aglantha digitale, a small, transparent medusa common in temperate and boreal waters. The same feeding response to A. digitale was observed whether the medusae were offered alone or together with a mixture of copepod prey. A. digitale mortality in the path of the mackerel school is estimated to be near 100%. Median carbon and nitrogen content of A. digitale was equivalent to about ten small copepods (e.g. Pseudocalanus sp.). A. digitale is abundant in temperate-boreal waters and may be an important source of nutrition to mackerel in the northwest Atlantic.     

Day/night differences in determination of growth rate of mackerel Scomber scombrus larvae during a patch-study in the Celtic Sea

The growth rate of mackerel, Scomber scombrus, larvae was calculated by analysing mean cohort length over time. The study took place on the central spawning ground of mackcrel in the Celtic Sea (Great Sole Bank) in April 1986. In order to minimize horizontal catch variability, repeated small-scale sampling with the Mocness plankton net was undertaken close to a satellite-tracked drifting buoy during a period of 78 h. Eighteen samples from nine hauls distributed over the whole sampling period were considered. One hundred larvae per sample were measured using a semi-automatic method. The proportion of larger larvae was significantly higher in night catches than in day catches. Independently calculated growth rates were 0.18 mm d^-1 for day catches and 0.14 mm d^-1 for night catches. This difference was not statistically significant. However, confidence in the calculation of growth rate, computed from night sampling, was much higher than that for day sampling. This may result as an effect of avoidance behaviour by larvae in daylight. Thus, night sampling seems to be a more reliable tool in the study of larval growth and should be used more extensively than daylight sampling.This paper was presented at the Early life history of fish symposium, Bergen, October 3 to 5, 1988     

Method for determination of turgor pressure in macroalgae,with particular reference to the Phaeophyta

A procedure is described for the determination of the internal osmotic pressure and turgor pressure of marine macroalgae, for use in the laboratory and on the shore. A volume-related parameter (either thallus fresh weight, or area) is measured before and after transfer of plant material to a range of hyperosmotic solutions. Plotting the final fresh weight/area as a percentage of the initial value gives a biphasic curve, with an initial component of negative slope due to the change in thallus volume in less extreme hyperosmotic solutions, where the non-rigid thallus contracts in response to decreasing cell turgor pressure. The second component has a shallower slope and represents plasmolysis in more extreme hyperosmotic solutions, i.e., where turgor pressure is reduced to zero and the protoplast shrinks away from the cell wall; the extraprotoplast space created by plasmolysis will be filled with the external solution and thus no further changes in weight occur. These two components intersect at the lowest osmotic pressure at which cell turgor is zero. By correcting for any effects of the cell wall on thallus volume, the relationship can be used to calculate internal osmotic pressure and hence turgor pressure, assuming that the remaining change in thallus volume of the initial component is due entirely to variation in the intraprotoplast volume (approximately equivalent to the intraprotoplast water content, determined by subtraction of the extraprotoplast water and dry weight from the thallus fresh weight). Using this procedure, the turgor pressures of Fucus spiralis L., Ectocarpus siliculosus, (Dillw.) Lyngb. and Laminaria digitata (Huds.) Lamour. (from Fife Ness, Scotland, May–August 1987) in a seawater-based medium were 0.82, 0.58 and 1.34 Osmol kg^–1, respectively. The turgor pressure of F. spiralis on the shore at Fife Ness (June 1987) was 0.74 Osmol kg^–1.     

Biotic passage through the Panama Canal,with particular reference to fishes

The effectiveness of the Gatun Lake fresh-water barrier to fish migration of the Panama Canal was examined, based on literature records and recent collections. Six species have migrated to the Pacific and three to the Atlantic Oceans. New records include: Hypleurochilus aequipinnis, Barbulifer ceuthoecus and Oostethus lineatus of Atlantic origin, and Gnathanodon, speciosus of Pacific origin. The majority of Atlantic migrants are known in the Pacific only from the Miraflores Third Lock, a unique ectogenic meromictic lake attached to the Pacific entrance of the canal. The hydrography and biota (including Atlantic algal and crustacean species previously unknown as canal migrants) of the lake are discussed. It is presumed that certain fish migrants transited the canal by associating with fouling material on the underside of ships. The euryhaline species, H. aequipinnis, Lupinoblennius dispar, Lophogobius cyprinoides and Omobranchus punctatus survived in freshwater (0.0‰S) for periods longer than réquired for ship transit of the canal (ca. 8h). The stenohaline migrant Gobiosoma nudum died after 2 h in freshwater, but survived more than 50 h at 2.5‰S. Plans to increase Panama Canal ship transits through the pumping of seawater into Gatún Lake might remove the biological barrier and allow the migration of euryhaline and stenohaline species. We find those plans unwise, and the potential consequences dangerous.     

Some observations on the relative abundance of biological sound scatters in the North-eastern Atlantic Ocean,with particular reference to apparent fish shoals

In various months of the years between 1960 and 1972, the R.R.S. “Discovery II” and R.R.S. “Discovery” carried out a number of echo-surveys in the North-eastern Atlantic Ocean between Latitudes 12° and 62°N, and from the European and African coasts to a longitude of approximately 29°W. The prime objective was to acquire data on sea-floor topography. In addition, numerous echo-traces of biological scattering present in midwater between depths of approximately 35 and 460 m were obtained. The traces were of variable quality, but were considered suitable for a preliminary evaluation of the scattering mainly as a basis for further investigation. The scattering recorded in daytime was broadly divisible into three types:

1. Diffuse layers, which were probably due to dispersed single fish. These were not analysed further.
2. Very small discrete echoes, mostly derived from single fish and very small shoals. These were mapped to show geographical regions of greater abundance.
3. Larger discrete echoes, most of which were almost certainly given by fish shoals. These were analysed in detail and information obtained on depth distribution, shoal density, geographical distribution and relative abundance. Small and moderate-sized shoals were found to be very numerous in spring and summer in oceanic water to the West and North-west of the British Isles. Large numbers of shoals of various sizes were also observed at various time of the year in the Bay of Biscay and near certain parts of the European and African Continental Shelf, near certain seamounts, and near islands such as the Azores, Madeira, and the Cape Verde Islands. In general, shoals appeared to be relatively sparse in the more southerly temperate and subtropical regions of the open ocean. The depth distribution of shoals in open water varied greatly but, on average, the maximum daytime depth of those in the more southerly area of the survey was slightly greater than that of those in the more northerly area. Shoal size also varied, shoals to the north of Latitude 50°N were on average slightly smaller than those detected in southerly regins. Possible identification of the fish is discussed.

     

Observations on the embryonic development of some deep-living decapod crustaceans,with particular reference to species of Acanthephyra

Eggs of meso- and bathypelagic decapod crustaceans were removed from gravid females and allowed to develop in vitro. The time course of embryonic development, as indicated by the appearance of certain morphological and physiological features, was determined for most species at a constant temperature of 12°C. The embryonic period, and the time between the appearance of certain key features such as naupliar and compound eyes and heartbeats, showed little variation in any one species. Significant differences were observed in the development times of different species. In general, species with large eggs have a longer embryonic period than those with small eggs, but there also variations between species with eggs of similar size. During the development of Acanthephyra eggs there is an approximate doubling of the egg volume, correlated with a decrease in egg density and an increase in the water content. The increase in the water content and egg volume is similar to that of other decapod eggs. It is concluded that those species with small eggs could have several broods in 1 year, whereas those species with large eggs are likely to be restricted to one, or in some cases possibly two, broods.     

Environmental problems of coal production in the United Kingdom with particular reference to the Yorkshire coalfield

This paper reviews the environmental problems associated with the coal-mining industry on the Yorkshire coalfield. The main environmental problems are identified as being caused by:

1. The need to dispose of large quantities of colliery waste or ‘spoil’, in an environmentally acceptable manner.
2. Derelict and despoiled land, including the problems caused by the re-working of old tips for their coal content.
3. Opencast coal mining.
4. Subsidence.
5. Transportation of coal and coal waste.

These problems are reviewed in the context of the role of coal in meeting the United Kingdom's energy needs and the framework of environmental control within which the coal-mining industry has to operate. Particular stress is laid on the fact that the Yorkshire coalfield, as with the majority of coalfields, is an old one with a legacy of inherited dereliction. Whilst modernisation of the mining industry is proceeding there have not been parallel developments put in hand to cope with the changing nature of the environmental problems resulting from the modernisation of the industry. Particular stress is placed on the need to dispose of the greatly increased quantities of spoil now being produced.     

An opinion on the distribution and behavior of chemicals in response to climate change,with particular reference to the Asia-Pacific region

There is a general lack of knowledge as regards the effects of climate change on pollutant behavior. This is particularly true of the Asia-Pacific Region (APR). This region has major significance in terms of global pollutant emission and also displays a wide variety of environments. This review presents the authors’ opinions on possible implications of climate change for pollutant behavior in the APR. Although differing responses can be expected across the region, there are clear implications as regards the short- and long-term behavior of pollutants. Effects can be predicted through modeling, but further data are required for model calibration. Nevertheless, it can be predicted that climate change will affect processes including global distillation of persistent organic pollutants, airborne transport of heavy metals, half-life of readily degradable pollutants, and eutrophication in water bodies. Particulates are expected to play a central role in mediating the effects of climate change, and successful predictive models will need to be based on particulate-mediated transport and behavior. Climate change also has the potential to cause an increase in the intensity and frequency of harmful algal blooms in aquatic environments throughout the region, with significant implications for supply of both food and drinking water.     

Trace element distribution and mobilization in Scottish soils with particular reference to cobalt,copper and molybdenum

Total and extractable trace element contents have been determined in about 1000 soil profiles representing the main soil series occurring throughout Scotland. The frequency distributions of a number of trace elements in these soils are described and some relationships between total and extractable contents discussed. The geological nature of the soil parent material, soil texture, organic matter content and environmental contamination are the principal factors controlling soil total contents. Soil drainage class, because of its effect on mineral weathering and soil oxidation-reduction conditions, has a major influence on soil extractable contents, availability to plants and crop uptake. Particular attention is paid to cobalt, copper and molybdenum because of their importance for animal health in Scotland.     

Environmental problems of coal production in the federal republic of of germany with particular reference to to the Ruhr

In 1979 it was noted that the production of deep-mined coal in the Federal Republic of Germany, including the Ruhr area, has risen once again. Since the beginning of the sixties the convenient source of both energy and raw material, oil, has been responsible for the falling levels of coal production in the Ruhr, to almost one half of peak production in 1956. Not much would have been needed to give up the entire troublesome and expensive process of deep coal mining in the Federal Republic in favour of the then cheap and bountiful oil. Only lignite managed to maintain a more or less steady annual production rate due to the direct conversion into electricity of a major part of its production at the site of extraction. Since the limitations and uncertainties governing the supply of crude oil have now been clearly exposed, the illusions about oil have begun to fade, and as a result confidence in our indigenous supplies of energy and raw material resources has been restored. What, however, are the implications of this revival of home-produced energy and raw material, which are not without problems both when produced and when consumed for the region in which they are extracted and brought to the surface, and where, to a large extent, the processing takes place? The region benefits from employment and investment, and in turn offers its resources (labour, land, water, air) inasmuch as past development has left them available for future development. But is the region to be covered with even more ‘honourable’ scars? In 1980, 87 million tonnes of deep mined coal were produced in the Federal Republic of Germany which resulted in roughly the same amount of minestone (spoil). Approximately 600 km² of densely populated area in the Ruhr district was already acquiring artificial drainage due to subsidence. Coking plants and old coal-based stations fired with deep mined coal pollute air and water. Lignite production in 1980 in the Federal Republic of Germany — which was almost entirely obtained by opencast mining — amounted to 130 million tonnes. To achieve this an additional 445×10⁶m³ of overburden had to be shifted. Already in 1977 in the Rhineland between Cologne, Dusseldorf and Aachen (Aix-la-Chapelle), 522 km² of mainly good agricultural land was acquired under compulsory purchase order for lignite mining. Villages, roads, rail and waterways were and continue to be re-routed and re-sited. The direct conversion of lignite into electricity produces emission and spreads pollution. Now, it is not only the people of the Ruhr area, the largest industrial conurbation in Europe, that have become sensitive to the impact of mining upon their environment. In all industrial countries it has been learned that those things which cannot be replaced, i.e. environment, are not always being valued by the free market at a price which represents the value they may have for the individual and possibly should have for all of us. Today the need for mining is hardly being questioned any more but people are voicing their opinion as to what is a just price to be paid. The citizen of the Ruhr, for instance, no longer accepts that the specific environmental impacts caused by deep coal mining, which produces a commodity wanted by the entire nation, should be borne solely at the place where it is produced and by the people who happen to live there. He demands that such burdens are borne by everybody who enjoys the benefits. Clear political ideas must be developed and made know as to how much we value home-produced energy sources, what proportion of the resulting burdens the country is willing to bear and how they are to be distributed fairly. There are many methods and technical means by which the burdens of the mining and industrial regions can be minimised, by which damage can be repaired and derelict areas reclaimed. The application of such means must be safeguarded by early planning and sufficient finanacing so that the exploitation of one resource will not result in other resources being lost.     

Policy relevance of three integrated assessment tools—A comparison with specific reference to agricultural policies

The Common Agricultural Policy (CAP), a system of market support instruments, direct income transfers, and rural development measures, has been put through an ongoing reform process in recent decades. This paper introduces three policy impact assessment tools (SIAT, SEAMLESS-IF, MEA-Scope tool) and analyses how these tools have responded to a number of challenges for integrated assessment modelling as reported in the international literature. Significant progress has been made with regard to modelling linkages whereas other challenges, particularly those related to issues of scale and uncertainty management, require further efforts. It is also analysed which CAP instruments are represented and what kinds of effects can be analysed at different scales. Market instruments and direct payments are comparatively well represented, while the ability to model rural development measures is mostly beyond the scope of these tools. Because each tool has found a different solution for coping with the common challenges of integrated assessment modelling, the choice of one of the tools for a particular application depends strongly on the policy questions being asked. The SIAT provides the big picture via its ability to represent broad changes in policy instruments with EU-wide cross-sector impacts. The most comprehensive analysis of agricultural policy instruments can be obtained with SEAMLESS-IF. The MEA-Scope tool complements the other two approaches with detailed regional profiles.     

The importance of coastal sand dunes for terrestrial invertebrates in Wales and the UK,with particular reference to aculeate Hymenoptera (bees,wasps &; ants)

Although most UK sand dune systems are now fossilized, with little mobility and reducing amounts of bare sand, they support important populations and assemblages of terrestrial invertebrates. Offering open conditions, warm substrates and a range of habitats and habitat structures, they have become increasingly significant as other coastal habitats have been lost. In Wales, 680 Red Data Book and Nationally Scarce species have been recorded from dunes. 109 species in the UK are restricted to dunes, and in Wales there are an additional 145 species confined to dunes and 208 species strongly associated with dunes. Of these, 172 species are dependent upon bare and sparsely-vegetated sand, in grey dunes and early-successional dune grassland, at some stage of their life cycle, rising to 292 species if those associated with the strandline, foredunes, yellow dunes and pioneer dune slacks are included, equating to 63% of the 462 dune species. Bees and wasps are particularly well represented, with 278 species (68% of the Welsh fauna) recorded on Welsh dunes, including 17 obligates and 44 species with a strong dependence, 52 of which are associated with bare and sparsely-vegetated sand. Key to maintaining invertebrate populations on UK dunes is the provision of bare sand but in Wales, bare sand accounts for only 1.7% of the total sand dune resource. As a more appropriate bare sand threshold is likely to range between 10 and 30%, radical action is required to re-mobilize at least the key sand dune systems.     

Preparing and presenting environmental impact statements in support of mining operations with particular reference to uranium mining

Throughout the world, the preparation of Environmental Impact Statements is rapidly becoming an integral part of any mining development. It would also appear to be a growing trend to have such Impact Statements submitted to a public forum before a decision on the proposed development is made. The proper preparation and presentation of a mining proponent's Environmental Impact Statement can make the difference between a lengthy and costly approval process and a more expeditious one.As a result of public concern over questions related to radioactivity, uranium mine projects have received special emphasis in the field of Environmental Impact Statements. This paper reviews briefly the background of various environmental hearings which have dealt with uranium mines in Canada and Australia and stemming from this analysis and the authors' experiences in respect of such hearings, makes suggestions on how Environmental Impact Statements can be prepared and presented from a technical and legal point of view so as to minimize the length of time and expense involved in the approval process and to maximize the chances of obtaining approval for the project.     

Hatching with the enemy: Daphnia diapausing eggs hatch in the presence of fish kairomones

Summary. Infochemicals are known to play a key role in mediating predator-prey interactions, both in aquatic and terrestrial communities. However, state-dependent variation may exist in how effectively individuals can use this information, depending on genotype, life stage and experience. For our study, we used the predator-prey model system fish-waterflea Daphnia magna Straus (Cladocera, Daphniidae). Adult Daphnia use fish-derived infochemicals, so-called kairomones, as indicators of predation risk, and exhibit a spectrum of morphological, behavioural and life-history responses to the presence of fish kairomones. Here, we investigate whether diapausing eggs, an embryonic resting stage in the life cycle of D. magna, also use fish kairomones and tune their hatching to the risk of fish predation, as reported for diapausing stages of dinoflagellates. In two laboratory experiments, we studied hatching proportion and time until hatching of D. magna diapausing eggs in the absence and presence of fish kairomones. D. magna families differed significantly in their response to the presence of fish kairomones; some families reduced hatching proportion, whereas others increased it. Our results imply genotype-dependent differences in the hatching reactions to fish kairomones as observed for other traits in adult Daphnia.     

Evaluation of carrying capacity with particular reference to firewood and fodder resources in Central Himalaya: a case study of Baliya catchment

SUMMARY

The dwindling forests of the Central Himalaya are suffering from serious losses, threatening the subsistence population of the region. This study analyses the rate of consumption of fodder and firewood in a Central Himalayan catchment and estimates the carrying capacity of the catchment for these resources. Estimates indicate that the carrying capacity of the natural ecosystems and agroecosystems, in terms of availability of fodder and fuelwood resources, has already been exceeded.     

Effects of salinity and temperature on Corophium volutator and C. arenarium (Crustacea: Amphipoda), with particular reference to distribution

The responses of the post-embryonic stages of Corophium volutator (Pallas) and C. arenarium Crawford to the combined effects of salinity and temperature show that gravid females have a wider tolerance than nongravid adult females which in turn are more tolerant than adult males. C. volutator is more tolerant of low salinity (2 to 10) than C. arenarium, but the latter is more tolerant of salinities above 45. The embryos of C. volutator develop normally and hatch at lower salinities and temperatures than those of C. arenarium, in which successful development was recorded at higher temperatures. Females undergoing a pre-copulatory moult failed to lay eggs below salinities of 3 (C. volutator) and 10 (C. arenarium), but in both species the lowest salinity at which all females moulted and laid eggs was 20. The results are discussed in relation to the distribution of both species.     

A molecular method for the identification of resting eggs of acartiid copepods in the Thau lagoon, France

Acartia and Paracartia species, often known to co-occur, can exhibit complex life cycles, including the production of resting eggs. Studying and understanding their population dynamics is hindered by the inability to identify eggs and early developmental stages using morphological techniques. We have developed a simple molecular technique to distinguish between the three species of the Acartiidae family (Acartia clausi, A. discaudata and Paracartia grani) that co-occur in the Thau lagoon (43°25′N; 03°40′E) in southern France. Direct amplification of a partial region of the mitochondrial cytochrome oxidase I gene by polymerase chain reaction and subsequent restriction fragment length polymorphism results in a unique restriction profile for each species. The technique is capable of determining the identity of individual eggs, including resting eggs retrieved from sediment samples, illustrating its application in facilitating population dynamic studies of this ubiquitous and important member of the zooplankton community.     

A morphological approach for relating decapod crustacean cephalothorax shape with distribution in the water column

Cephalothorax profiles for individuals of 18 decapod crustacean species were obtained from pictures of specimens captured using various experimental bottom trawls in the Mediterranean basin, at depths ranging from 200 to 4000 m in 2000 and 2002. Profiles were compared using the shape (outline) of the entire cephalothorax (including and excluding the rostrum). Principal component analysis (PCA) of the profiles, rostrum included, yielded two large species groupings related to rostrum size, species having a long rostrum being clustered on the positive portion of the first axis and species having a short rostrum being clustered on the negative portion of this same axis (the F1 axis explained 72.17% of the total variance). The PCA separated pelagic and endobenthic animals (with short rostrums) from nektobenthic animals (with long rostrums). Only the two deepest-dwelling species (dwelling at depths below 2000 m) were distanced from their respective groups. The pelagic shrimp Acanthephyra pelagica was clearly grouped with the nektobenthic species despite being reported to have a pelagic habitat. The nektobenthic deep-sea species Nematocarcinus exilis has a relatively medium-size rostrum and was placed among the pelagic–endobenthic species. The endobenthic and pelagic groups remained stable even when rostral morphometrics were excluded from the PCA analysis. The hypothesis that predation and diet are the fundamental determining factors for all habitats throughout most of the lifetimes of individuals and hence that species will evolve specialised phenotypes to adapt to local environmental conditions is considered in the discussion.Communicated by O. Kinne, Oldendorf/Luhe     

Breeding of Euterpina acutifrons,a harpacticid copepod,with special reference to dimorphic males

The breeding of Euterpina acutifrons, a marine harpacticid copepod, was studied both in the laboratory and in the natural population round Anglesey, England, with special reference to dimorphic males. As a result of successful rearing of the species under laboratory conditions, rates of development at different temperatures, and survival and maturation of all types of adults were studied. The dimorphic males developed faster than the females, and the small males had a shorter development time than the larger individuals. Laboratory observations clearly indicated that the males differ markedly in sexual behaviour, the small male being more potent, readily copulating with females, and always very active in breeding. In natural populations, temperature was found to have a limiting influence on the breeding period. Breeding began when the temperature reached 15° to 16°C, and ceased when it fell to 8°C. The most significant feature was the production of small males in nature; they increased in number with the onset of breeding, and always formed a high proportion of the actively breeding population. Both laboratory and field investigations have shown that the small male is a breeding form, and is apparently an adaptation of the species for carrying out successful breeding in the colder areas of its distribution.