Relation of fish larvae and zooplankton biomass in the Gulf of Aden

This study is based on zooplankton samples collected in the upper 50 m by the F.R.V. Manihine in the Gulf of Aden during October–November, 1966 and February–March, 1967. Generally, the displacement volume of zooplankton varied between 20 and 67 ml/m². Some higher values, up to 100 ml/m², were also observed. The number of larval fish in positive hauls ranged from 2 to 282 larvae/m². An inverse relationship between the number of larval fish and the accompanying volume of zooplankton was noted. This relationship is discussed. It is hypothesized that larval mortality due to predation in the Gulf of Aden during the northeast monsoon (November, February and March) was very high.     

The link between 'green' and economic success: environmental management as the crucial trigger between environmental and economic performance

The link between environmental and economic performance has been widely debated in the literature for the last ten to fifteen years. One view is that improved environmental performance mainly causes extra costs for the firm and thus reduces profitability. However, also the opposite has been argued for: improved environmental performance would induce cost savings and increase sales and thus improve economic performance. Theoretical and empirical research have provided arguments for both positions and have not been conclusive so far. This article discusses reasons for the different views and the differences in empirical research and presents a theoretical framework to explain the coexistence of the conflicting views. It is argued that not merely the level of environmental performance, but mainly the kind of environmental management with which a certain level is achieved, influences the economic outcome. The model presented provides implications for both empirical research and company management in practice. Research and business practice should focus less on general correlations and more on causal relationships of eco-efficiency, i.e. the effect of different environmental management approaches on economic performance.     

A new type of insect infrared organ of low thermal mass

The Australian beetle Acanthocnemus nigricans is attracted by forest fires and has a pair of complex infrared (IR) receptor organs on the first thoracic segment. Each organ consists of a tiny sensory disc (diameter 120-130 µm) which serves as an absorbing structure for IR radiation. The disc is arranged above an air-filled cavity which is located just anteriorly to the coxae of the prothoracic legs. Inside the disc, about 30 multipolar thermoreceptors (warmth receptors) are tightly attached to the cuticle which is directed to the outside. The many dendrites of each multipolar neuron are tightly wrapped around the soma and contain a large number of mitochondria. Absorption of IR radiation by the disc causes an increase in temperature which is measured by the warmth receptors. Therefore, the IR receptors of A. nigricans can be classified as microbolometers with reduced thermal mass and in principle can be compared to the IR organs of pit vipers.     

Nahrung aus dem Meer

Background and Scope

There is a multitude of uses in the seas worldwide: fishing, shipping, tourism, exploitation of oil and gas, sea-bed mining, waste disposal, etc. They all compete for space and resources. Each of them has its specific impact on marine ecosystems. Furthermore, they interact with each other and with the marine environment. Fisheries are the most deleterious interactions of man with marine ecosystems by withdrawing a major part of the annual production of large fish, molluscs and crustacea. Many marine habitats are destroyed by fishing, particularly by heavy bottom trawling.

Basics of Fisheries

The production of a fish stock can be increased by removing the old fish. Fishing is sustainable as long as it is restricted to the removal of the surplus production. Subventions and market forces are opposed the rational way of effort reduction aiming at the recovery of overexploited stocks. Fishing has collateral effects on target species. Heavy selective fishing of large, slow-growing predatory fish will favour small, fast-growing species of a lower level in the trophic pyramid. Fishing in marine ecosystems is a complex process in which biological and economic factors interact. At different scales of space and time they are superimposed by changes in the oceanic environment. Climatic variations and global warming of the Ocean differ in their effects from region to region, and they affect distribution, composition and fishing yield of the various exploited fish stocks. Politics has a major impact on the development of fisheries; historical examples are the collapse of the Eastern Bloc with its big distant water fishing fleets, or the introduction of the 200 nm Economic Zones, putting most fish stocks under national jurisdiction.

Discussion

Fishery science is still striving to understand the variability of year-class strength in fish stocks. In the foreground of modern research, however, are the interactions in multi-species communities in relation to changes in the abiotic and biotic environment and to different kinds of management. We have no possibility to study the complex interactions in marine fish communities by controlled experiments. The only information we have are records on landings and fishing efforts. They provide the basis for sophisticated mathematical models. Ecosystem modelling is a relatively young field in marine ecology. In Europe and North America fishery science is more than hundred years old. It is not possible, however, to apply the methods and models of, e.g., North Sea research to low latitude ecosystems and fisheries.

Conclusions

The sustainable use and protection of the marine living resources and biodiversity are global challenges. Each Large Marine Ecosystem calls for specific solutions in terms of research and management. Problems have to be tackled not only by computer models and remote sensing, but also by field research in all parts of the world. The further development of marine and fisheries research in developing countries is a matter of north-south-partnerships with high win-win spin-offs. Over the past decades some excellent groups of marine scientists from several tropical countries have been established who are very open for partnership projects in the true sense. They offer great opportunities to jointly study the richness of marine fauna, flora, and ecosystems in tropical and subtropical shelf seas and up-welling regions.     

Moosmonitoring als Spiegel der Landnutzung?

Goal, Scope and Background

The study was conducted to test the hypothesis that the regional variability of nitrogen (N) and metal accumulations in terrestrial ecosystems are due to historical and recent ways of land use. To this end, in two regions of Central Europe the metal and N accumulations in both regions should be examined by comparative moss analysis. The regions should be of quantitatively specified representativity for selected ecological characteristics of Europe. Within both regions these characteristics should be covered by the sites where the moss samples were collected. The number of samples should allow for geostatistical estimation of the measured nitrogen and metal loads.

Methods

The two regions of investigation were selected according to an ecological land classification of Europe which was computed by classification trees. Within each of both research areas the sampling points were localized according to the areas occupied by the ecologically defined land classes. The sampling and chemical analysis of mosses was conducted in accordance with an appropriate UNECE guideline by means of ICP-MS (metals) and combustion analysis (N). The quality of measurements was assured using certified reference materials. The differences of deposition loads were tested for statistical significance with regard to time and space. Variogram analysis was used to examine and model the spatial autocorrelation function of the measurements. Ordinary kriging was then applied for surface estimations.

Results

By use of the ecological regionalisation of Europe the Weser-Ems Region (WER) and the Euro Region Nissa (ERN) were selected for investigation. The sampling sites represent quite well the natural landscapes and the land use categories of both regions. The measurement values corroborate the decline of metal accumulation observed since the beginning of the European Mosses Monitoring Survey in 1990. The metal loads of the mosses in the ERN exceed those in the WER significantly. The opposite holds true for the N concentrations: those in the WER are significantly higher than those in the ERN.

Discussion

The decrease of heavy metal emissions is correlated with lowered deposition and accumulation rates in terrestrial ecosystems. The accumulation of nitrogen in the biosphere is not following this trend.

Conclusions

The technique of moss analysis is adequate for spatially valid biomonitoring of spatial and temporal trends of metals and nitrogen in terrestrial ecosystems. By this, it enables to prove the efficiency of environmental policies.

Recommendations and Perspectives

The accumulation of N in ecosystems is still a serious environmental problem. Related ecological impacts are the eutrophication of aquatic ecosystems like ground waters, lakes, rivers and oceans as well as the biocoenotic changes in terrestrial ecosystems. Thus, a statistically valid exposure analysis must encompass both, accumulation of metals and N bioaccumulation. Further, the bioaccumulation of persistent organic pollutants should be monitored. Finally, environmental biomonitoring should be conducted in much closer contact with human health aspects.     

Influence of fish on habitat choice of water birds: a whole system experiment

It is notoriously difficult to study population interactions among highly mobile animals that cannot be meaningfully confined to experimental plots of limited size. For example, migratory water birds are believed to suffer from competition with resident fish populations for shared food resources. While observational evidence in support of this hypothesis is accumulating, replicated experiments addressing this issue at the proper spatial scale are lacking. Here, we report from a replicated whole-system experiment in which we stocked large (0.07 km2), shallow (< or =2.5 m deep), highly eutrophic ponds in the bird protection area "Ismaninger Speichersee mit Fischteichen" with different densities of carp and assessed the responses of water birds and their food resources during summer over several years. In all years, the biomasses of benthic macroinvertebrates, macroalgae, and macrophytes as well as the densities of herbivorous, carnivorous, and omnivorous water birds were reduced in carp ponds compared to fishless ponds. The negative effects of carp on food resources and on the numbers of water birds feeding in carp ponds increased over the season (May-September) and were stronger at high than at low stocking densities of carp. Consequently, differences in resource densities between ponds with and without carp increased, and the ranking of ponds with respect to resource densities became more predictable over the season. These factors may have contributed to a seasonal improvement of the birds' abilities to track resource densities across ponds, as suggested by tight correlations of bird numbers on ponds with resource densities late, but not early, in the season.     

Accounting for enforcement costs in the spatial allocation of marine zones

Marine fish stocks are in many cases extracted above sustainable levels, but they may be protected through restricted‐use zoning systems. The effectiveness of these systems typically depends on support from coastal fishing communities. High management costs including those of enforcement may, however, deter fishers from supporting marine management. We incorporated enforcement costs into a spatial optimization model that identified how conservation targets can be met while maximizing fishers’ revenue. Our model identified the optimal allocation of the study area among different zones: no‐take, territorial user rights for fisheries (TURFs), or open access. The analysis demonstrated that enforcing no‐take and TURF zones incurs a cost, but results in higher species abundance by preventing poaching and overfishing. We analyzed how different enforcement scenarios affected fishers’ revenue. Fisher revenue was approximately 50% higher when territorial user rights were enforced than when they were not. The model preferentially allocated area to the enforced‐TURF zone over other zones, demonstrating that the financial benefits of enforcement (derived from higher species abundance) exceeded the costs. These findings were robust to increases in enforcement costs but sensitive to changes in species’ market price. We also found that revenue under the existing zoning regime in the study area was 13–30% lower than under an optimal solution. Our results highlight the importance of accounting for both the benefits and costs of enforcement in marine conservation, particularly when incurred by fishers. Justificación de los Costos de Aplicación en la Asignación Espacial de Zonas Marinas