Optimal exploitation of a fishery employing a non-linear harvesting function

A harvesting function is developed to described the rate of removal of fish from a fish population. The function incorporates the effects of both the handling or processing time of the catch and the competition, between boats in the fleet, for the fish.We will assume that the growth rate of the fish population can be modelled with a concave, dome shaped growth curve. With this assumption, it has been shown that if the rate of harvesting the fish is linearly related to both effort (which can be thought of as some measure of the number of boats in the fleet) and the population size, then the population will tend towards a single equilibrium level which is globally stable. This paper shows that the saturation effects due to the handling time may generate two equilibrium levels (one stable, one unstable) rather than a single globally stable equilibrium. The results of competition between boats are economically undesirable because of the decrease in efficiency. However, this competition may be beneficial to the exploited fish population.Using the harvesting model derived earlier, the steady state or long term optimal harvesting policies as well as the transition paths to these states are developed. The only constraint is on the maximum allowable effort which is effectively an upper limitation on the fleet size or number of man-hours of fishing.     

Optimal escapement levels in stochastic and deterministic harvesting models

A constant-escapement feedback policy is shown to be optimal in maximizing expected discounted net revenue from an animal resource whose dynamics are described by a stochastic stock-recruitment model, provided that unit harvesting costs satisfy certain conditions. The optimal escapement in this model is compared with that in the corresponding deterministic model and it is shown how the way in which unit harvesting costs vary with population abundance can be important in determining the relative sizes of the optimal escapements. In most cases, the optimal stochastic escapement is no less than the optimal deterministic escapement.     

Optimal harvesting of ecologically interdependent fish species

The optimal exploitation of a two-species predator-prey system is considered, using Lotka-Volterra-type equations. Due to the density-dependence of ecological efficiency, both species should be harvested simultaneously over a range of relative prices. Beyond the limits of this price range, either the prey species should be utilized indirectly by harvesting the predator, or the predator should be eliminated to maximize the prey yield. Neglecting harvesting costs, the simultaneous harvest of prey and predators requires that a unit of prey biomass increase in value by being “processed” by predators. Certain results from single-species fishery models are shown not to apply to multispecies models. These are as follows: (i) Optimal regulation of a free access fishery may call for subsidizing instead of taxing the harvest of predator species. (ii) Increasing the discount rate may, at “moderate” levels, imply that the optimal standing stock of biomass increases instead of decreasing. (iii) A rising price or a falling cost per unit fishing effort of a species may raise and not lower the optimal standing stock of that species.     

Correlation of cancer incidence with groundwater geochemistry in northern Finland

The correlations of age-adjusted incidences of various forms of cancer with the geochemical composition of well water and other forms of groundwater in northern Finland have been studied using standard statistical methods. Available geochemical maps showing the hardness of the water and its uranium, iron and nitrate content and maps depicting the areal distribution of the incidences of ten forms of cancer, were decoded point by point to numerical concentration or incidence values by placing a transparent sheet carrying a regular rectangular grid over each. The grid covering the north of Finland (north of 65 ° N latitude) comprised 261 observation points distributed at regular intervals of about 25 km on the ground.The calculated Spearman product-moment and rank correlation coefficients between the geochemical and medical variables suggest that a strong, statistically significant (p<0.001) positive correlation prevails between the hardness of the water and several forms of cancer, especially total cancer (all forms of cancer combined) in the female population (r = 0.66). On the other hand, iron and, somewhat surprisingly, nitrates, which are commonly thought to promote cancer, show a low degree of correlation with the forms of cancer studied. Also, contrary to expectation, a negative correlation between most forms of cancer with groundwater uranium is indicated, a result which, because of its unexpectedness, calls for further research work based on larger data sets before a conclusion can be drawn that it can be interpreted as an implication of a trend that an appropriate level of uranium in the groundwater and the resulting gentle dose of natural radioactive irradiation can help to prevent the early development of cancer in human tissues and cells.The positive correlation between water hardness and most forms of cancer studied suggests that hard drinking water may be an initiator and promoter of cancer, although it is admitted that the establishment of a positive correlation between the geochemical and medical variables does not necessarily prove a cause-and-effect relationship between them.     

Comparison of health patterns in two geochemically contrasted areas of northern Finland

In order to prepare the ground for a discussion of possible causal relationships between health patterns and the geochemistry of an area, health patterns in the form of age-adjusted cancer incidence values and rates of mortality due to (1) cancer of the stomach, colon or rectum, (2) lung cancer and (3) ischaemic heart diseases are compared between the populations of two geochemically contrasted communes of northern Finland (Kemijärvi and Kuusamo). Statistically significant differences (p < 0.001) are encountered in the mortality rates due to ischaemic heart diseases and marked differences in the incidence values of lung cancer, the former being higher in Kuusamo and the latter in Kemijärvi. The higher incidence of lung cancer observed in Kemijärvi is in accordance with previous results reported from the USA, where higher incidences have been observed in areas of granitic bedrock. Regarding the higher mortality rate due to ischaemic heart diseases In Kuusamo, which is geochemically characterised by higher potassium (p < 0.002) and calcium (p < 0.004) and lower Zn, V, Ti, and Fe (p > 0.002) in the soil (actually, in the fine till fraction), no easily demonstrable cause- and-effect relationship can be established.     

Optimal management of a confined groundwater system

Dynamic programming is applied to a relatively simple economic and hydrologic model of a confined aquifer system in Southwest Montana to determine an optimal interseasonal allocation schedule. The derived decision rule demonstrates the economic advantage of maintaining a confined groundwater system. While localized intraseasonal loss of the artesian pressure may occur, it is important to maintain this pressure from year to year because of its role in reducing extraction costs. The welfare gap, as measured by differences in the net present value of economic returns to the basin under an optimal use policy versus an uncontrolled, “common pool” situation, is not trivial. Sensitivity analysis indicates that assumptions about uniformity of land productivity, vis-à-vis their impact on the shape of the returns function, the discount rate, and the level of electric power rates are particularly critical with respect to the magnitude of the commonality problem.     

Antler asymmetry and immunity in reindeer

Fluctuating asymmetry (FA) measures an individual's ability to undergo identical development in bilaterally symmetrical characters and may indicate sensitivity to environmental stress. FA in ornamental characters is often positively related to parasite intensities, which are important environmental stressors. Parasites affect and are affected by several parts of the immune system, and the ability to resist parasites may be signalled via FA in ornaments. In this study we examined reindeer antlers, which show FA, demonstrated to be caused by parasite infections. We measured antler FA, immune parameters (i.e. densities of different classes of leukocytes, IgG levels and abomasal lymph node numbers) and intensity of abomasal nematodes in free-ranging 1.5-year-old male reindeer slaughtered in the early part of their rutting period. We found a relationship between parasite intensity and immune parameters suggesting that our measures of immune activity reflect density of current parasite infections. More important, these immune parameters were associated with FA in both the main beam length and numbers of antler tines. The immune parameters were, however, only weakly correlated to antler size. This indicates that FA, but not size, of antlers grown during exposure to a multitude of environmental stressors may reveal information about individual immunity that can be important for host-parasite interactions. Antler FA may therefore communicate an individual's quality during the rut in reindeer. Received: 30 March 1998 / Accepted after revision: 15 August 1998     

Optimal defense: snails avoid reproductive parts of the lichen Lobaria scrobiculata due to internal defense allocation

The optimal defense theory (ODT) deals with defensive compounds improving fitness of a particular organism. It predicts that these compounds are allocated in proportion to the risk for a specific plant tissue being attacked and this tissue's value for plant fitness. As the benefit of defense cannot easily be measured in plants, the empirical evidence for ODT is limited. However, lichens are unique in the sense that their carbon-based secondary compounds can nondestructively be removed or reduced in concentration by acetone rinsing. By using such an extraction protocol, which is lethal to plants, we have tested the ODT by studying lichens instead of plants as photosynthetically active organisms. Prior to acetone rinsing, we found five times higher concentration of meta-scrobiculin in the reproductive parts (soralia) of Lobaria scrobiculata compared to somatic parts of this foliose epiphytic lichen species. At this stage, the lichen-feeding snail Cochlodina laminata avoided the soralia. However, after removal of secondary compounds, the snail instead preferred the soralia. In this way, we have successfully shown that grazing pattern inversely reflects the partitioning of the secondary compounds that have a documented deterring effect. Thus our study provides strong and novel evidence for the ODT.     

Nonlinear effects of climate and density in the dynamics of a fluctuating population of reindeer

Nonlinear and irregular population dynamics may arise as a result of phase dependence and coexistence of multiple attractors. Here we explore effects of climate and density in the dynamics of a highly fluctuating population of wild reindeer (Rangifer tarandus platyrhynchus) on Svalbard observed over a period of 29 years. Time series analyses revealed that density dependence and the effects of local climate (measured as the degree of ablation [melting] of snow during winter) on numbers were both highly nonlinear: direct negative density dependence was found when the population was growing (Rt > 0) and during phases of the North Atlantic Oscillation (NAO) characterized by winters with generally high (1979-1995) and low (1996-2007) indices, respectively. A growth-phase-dependent model explained the dynamics of the population best and revealed the influence of density-independent processes on numbers that a linear autoregressive model missed altogether. In particular, the abundance of reindeer was enhanced by ablation during phases of growth (Rt > 0), an observation that contrasts with the view that periods of mild weather in winter are normally deleterious for reindeer owing to icing of the snowpack. Analyses of vital rates corroborated the nonlinearity described in the population time series and showed that both starvation mortality in winter and fecundity were nonlinearly related to fluctuations in density and the level of ablation. The erratic pattern of growth of the population of reindeer in Adventdalen seems, therefore, to result from a combination of the effects of nonlinear density dependence, strong density-dependent mortality, and variable density independence related to ablation in winter.     

Quantifying dispersal and establishment limitation in a population of an epiphytic lichen

Dispersal is a process critical for the dynamics and persistence of metapopulations, but it is difficult to quantify. It has been suggested that the old-forest lichen Lobaria pulmonaria is limited by insufficient dispersal ability. We analyzed 240 DNA extracts derived from snow samples by a L. pulmonaria-specific real-time PCR (polymerase chain reaction) assay of the ITS (internal transcribed spacer) region allowing for the discrimination among propagules originating from a single, isolated source tree or propagules originating from other locations. Samples that were detected as positives by real-time PCR were additionally genotyped for five L. pulmonaria microsatellite loci. Both molecular approaches demonstrated substantial dispersal from other than local sources. In a landscape approach, we additionally analyzed 240 snow samples with real-time PCR of ITS and detected propagules not only in forests where L. pulmonaria was present, but also in large unforested pasture areas and in forest patches where L. pulmonaria was not found. Monitoring of soredia of L. pulmonaria transplanted to maple bark after two vegetation periods showed high variance in growth among forest stands, but no significant differences among different transplantation treatments. Hence, it is probably not dispersal limitation that hinders colonization in the old-forest lichen L. pulmonaria, but ecological constraints at the stand level that can result in establishment limitation. Our study exemplifies that care has to be taken to adequately separate the effects of dispersal limitation from a limitation of establishment.     

A bioeconomic model of harvesting a multispecies fishery

The paper deals with the problem of combined harvesting of two competing fish species, each of which obeys the law of logistic growth. It is shown that the open-access fishery may possess a bionomic equilibrium which drives one species to extinction. An analysis of the dynamic behaviour of the system reveals that its non-trivial critical point is either an asymptotically stable node or an unstable saddle point depending on the values of the biological parameters. Further, the nature of the trivial critical point (origin) is found to depend on the biotechnical productivity (btp) of each species. It is also proven that the dynamic system does not possess any limit cycles. Mathematical formulation of the optimal harvest policy is given and its solution is derived in the equilibrium case by using Pontryagin's maximal principle. Biological and economic interpretations of the results associated with the optimal equilibrium solution are explained. The significance of the results derived in the paper are then discussed.     

Climate, icing, and wild arctic reindeer: past relationships and future prospects

Across the Arctic, heavy rain-on-snow (ROS) is an "extreme" climatic event that is expected to become increasingly frequent with global warming. This has potentially large ecosystem implications through changes in snowpack properties and ground-icing, which can block the access to herbivores' winter food and thereby suppress their population growth rates. However, the supporting empirical evidence for this is still limited. We monitored late winter snowpack properties to examine the causes and consequences of ground-icing in a Svalbard reindeer (Rangifer tarandus platyrhynchus) metapopulation. In this high-arctic area, heavy ROS occurred annually, and ground-ice covered from 25% to 96% of low-altitude habitat in the sampling period (2000-2010). The extent of ground-icing increased with the annual number of days with heavy ROS (> or = 10 mm) and had a strong negative effect on reindeer population growth rates. Our results have important implications as a downscaled climate projection (2021-2050) suggests a substantial future increase in ROS and icing. The present study is the first to demonstrate empirically that warmer and wetter winter climate influences large herbivore population dynamics by generating ice-locked pastures. This may serve as an early warning of the importance of changes in winter climate and extreme weather events in arctic ecosystems.     

The sensitivity of carbon sequestration to harvesting and climate conditions in a temperate cypress forest: Observations and modeling

The role of disturbance and climate factors in determining the forest carbon balance was investigated at a Japanese cypress forest in central Japan with eddy flux measurements, tree-ring analyses, and a terrestrial biosphere model. The forest was established as a plantation after intermittent harvesting and replanting between 1959 and 1977, and acted as a strong carbon sink of approximately 500 g C m⁻² year⁻¹ for the measurement years between 2001 and 2007. A terrestrial biosphere model, BIOME-BGC, was validated using the eddy flux data at daily to interannual timescales, and the tree-ring width data at interannual to decadal timescales. According to the model simulation, during the observation period 270 ± 55 g C m⁻² year⁻¹ was additionally sequestered due to the indirect effects of the harvesting and planting, whereas the increase of CO₂ concentration and the change in climate increased the sink of 110 ± 40 and 30 ± 80 g C m⁻² year⁻¹, respectively. The model simulation shows that the forest is now recovering from harvesting, and that harvesting is a more important determinant of the current carbon sink than either interannual climate anomalies or increased atmospheric CO₂ concentration. We found that harvesting with long rotation length could be effective management activity in order to increase carbon sequestration, if the harvested timber is converted into products with long lifecycles.     

Water hardness and cardiovascular mortality in Finland

In Finland, where mortality rates of cardiovascular diseases are as a rule among the highest in the world, significant areal differences in these figures are encountered especially between the eastern and western parts of the country. To test the hypothesis that these differences,( the reason of which has long been a subject for a lively debate in Finland), may result from geochemical factors such as variations in the hardness or calcium or magnesium content of well water a correlation analysis was carried out in which the geochemical properties in each of the country's individual administrative districts, or communes (444 in all, excluding Åland) were compared with the percentage of heart diseases among the causes of death from diseases in 1991. The results show a poor or extremely low correlation nation-wide (r ranging from –0.039 to +0.045), indicating a virtual absence of any causal relationship. On the other hand, taken pairwise, the extreme western and eastern provinces, Vaasa andNorthern Karelia, show marked differences both in their geochemical and mortality data, the percentage of deaths caused by cardiovascular diseases being markedly lower in the province of Vaasa, where the hardness and the magnesium content of well water (but not the calcium content) are significantly higher (p < 0.001 and 0.002 respectively). This inverse relationship is in line with the supposition that in addition to other factors, geochemical differences may have an effect on mortality.     

Flexible incubation rhythm in northern fulmars: a comparison between oceanographic zones

Variation in the timing and abundance of marine food resources is known to affect the breeding behaviour of many seabirds, constraining our understanding of the extent to which these behaviours vary in different parts of a species’ range. We studied incubation shifts of northern fulmars (Fulmarus glacialis) breeding at two colonies in Arctic Canada (High Arctic oceanographic zone) and one colony in the UK (Boreal oceanographic zone) between 2001 and 2005. Fulmars in Arctic Canada had longer incubation shifts than previously reported at more southern colonies, presumably because marine productivity is lower early in the breeding season in the Arctic. Shift durations were particularly long at one colony in years with abnormally late, extensive sea-ice cover, although at the other Arctic colony, where sea-ice cover is predictably late every year, the duration of shifts was shorter than expected. At the Boreal colony, incubation shifts were much longer than expected, similar to Arctic colonies, and likely attributable to poor marine food supplies in the North Sea in recent years. Collectively, our data suggest that fulmars can adjust their incubation rhythm to compensate for poor marine feeding conditions, although this may incur a cost to body condition or reproductive success.     

Male age structure influences females’ mass change during rut in a polygynous ungulate: the reindeer (Rangifer tarandus)

The manipulation of the sex ratio and age structure in many managed ungulate populations calls for a better understanding of their potential consequences on females’ condition and behavior during rut. During 1996–2002, we manipulated the male age structure and male percentage (nine treatments during 7 years) within an experimental herd of semidomestic reindeer (Rangifer tarandus) and investigated their influence on both the body mass change and the behavior of females during rut. On average, the females lost body mass (−0.95±SE 0.18 kg) during rut, which we contend to reflect somatic costs. The females’ losses increased as the percentage of male decreased, but this was certainly ascribed to one treatment with high male percentage (27.7%) as compared to the others (ranging from 3.9 to 12.2%). Female losses were highest for treatments including both young and adult males as compared to only adult or only young males, and higher for treatments including only young compared to only adult males. This is supported by (1) the higher female harassment frequency when females are exposed to only young or a mixture of young and adult males as compared to only adults, (2) the higher female harassment frequency by young males as compared to adults in the mixed treatments, and (3) the reduced females’ feeding activity in treatments including both young and adult males. We conclude that the male age structure during rut will influence the females’ behavior and mass change and may have implications for females’ life history and for population dynamics.     

Industrial ecology flows of agriculture and food industry in Finland: utilizing by-products and wastes

Although half of the administrative units in China are said to have implemented their local Agenda 21, the promotion of sustainable communities is not pervasive. In this paper, we adopted a relatively untried mode of analysis and a socio-economic context to illustrate the potentials and failures of China's grassroots local government bodies in achieving sustainable waste management. Our study shows that, among the three main functions of sustainable waste management (ensuring environmental hygiene, provision of recycling logistics and changing the consumption pattern of the local community) for local governments, grassroots local government bodies in mainland China are only able to do the minimum, i.e. ensuring environmental hygiene and handling complaints. One of the reasons for the failure is that, despite the emphasis on capacity building in China's Agenda 21, the reality is that no action is taken to empower grassroots local government. Despite the high profile accorded by the Chinese central government to motivating local governments to formulate their own Agenda 21, local sustainability and waste management performance have little relevance to the appraisal systems of these government agents.     

Economic and environmental performance of electricity production in Finland: A multicriteria assessment framework

Meeting environmental, economic, and societal targets in energy policy is complex and requires a multicriteria assessment framework capable of exploring trade-offs among alternative energy options. In this study, we integrated economic analysis and biophysical accounting methods to investigate the performance of electricity production in Finland at plant and national level. Economic and environmental costs of electricity generation technologies were assessed by evaluating economic features (direct monetary production cost), direct and indirect use of fossil fuels (GER cost), environmental impact (CO₂ emissions), and global environmental support (emergy cost). Three scenarios for Finland's energy future in 2025 and 2050 were also drawn and compared with the reference year 2008. Accounting for an emission permit of 25 €/t CO₂, the production costs calculated for CHP, gas, coal, and peat power plants resulted in 42, 67, 68, and 74 €/MWh, respectively. For wind and nuclear power a production cost of 63 and 35 €/MWh were calculated. The sensitivity analysis confirmed wind power's competitiveness when the price of emission permits overcomes 20 €/t CO₂. Hydro, wind, and nuclear power were characterized by a minor dependence on fossil fuels, showing a GER cost of 0.04, 0.13, and 0.26 J/J_e, and a value of direct and indirect CO₂ emissions of 0.01, 0.04, and 0.07 t CO₂/MWh. Instead, peat, coal, gas, and CHP plants showed a GER cost of 4.18, 4.00, 2.78, and 2.33 J/J_e. At national level, a major economic and environmental load was given by CHP and nuclear power while hydro power showed a minor load in spite of its large production. The scenario analysis raised technological and environmental concerns due to the massive increase of nuclear power and wood biomass exploitation. In conclusion, we addressed the need to further develop an energy policy for Finland's energy future based on a diversified energy mix oriented to the sustainable exploitation of local, renewable, and environmentally friendly energy sources.