Management of Evolving Fish Stocks [Revised and updated 16 June 1998]

Mortality caused by harvesting can select for life history changes in the harvested stock. Should this possibility be taken into account in the management of renewable resources? I compare the performance of different harvest strategies when evolutionary change is accounted for with a help of an age-structured population dynamics model. Assuming that age of first reproduction is the only evolving trait, harvesting of only mature individuals selects for delayed maturation and results in increased sustainable yields. Unselective harvesting of both mature and immature fish selects for earlier maturation which causes the sustainable yield to decrease. Constant stock size and constant harvest rate strategies perform equally well in terms of maximum sustainable yield, both before and after evolutionary change. The maximum sustainable yield for fixed quota strategies is lower. All those strategies have similar evolutionary consequences given a similar average harvest rate. Coevolutionary dynamics between fish stock and the stock manager indicate that the evolutionary benefits of selective harvesting are attainable without incurring yield losses in the near future

Quantitative traits

Quantitative traits are phenotypic traits that are determined, jointly with the environment, by many genes of small effect. Most of the directly observable individual characteristics are quantitative traits. Differences in quantitative traits can give valuable signals on existence of separate stock components. Compared to neutral genetic markers, quantitative traits are more sensitive to population structure and may suggest differences where neutral genetic markers fail to show any. However, quantitative traits may also show differences where demographic separation is weak. An important challenge is to understand how the environment influences quantitative traits. Representing quantitative traits as reaction norms makes their dependence on the environment explicit and thereby facilitates their use in stock identification

Influence of Colored Noise on the Extinction Risk in Structured Population Models

We use simple models to compare extinction risk among basic life history types when environmental noise is either uncorrelated ("white") or positively autocorrelated ("red"). The metric of extinction is probability of extinction in 50 years; variability of noise is scaled such that its expected variance is independent of colour at this time scale. We compare annual, semelparous biennial, iteroparous biennial and perennial life histories. Given an identical equilibrium population size and basic reproductive number, annual life histories confer a much higher extinction risk than semelparous biennial life histories. Iteroparous biennial and perennial life histories have even lower extinction risks. Autocorrelated noise influences the life histories differently: the extinction risk of the annuals decreases with reddening noise, whereas the other life histories show an opposite response. We show that in a previously developed stage-structured population model for the Florida scrub jay "Aphelocoma coerulescens" ignoring the possibility of red environmental noise might result in a much too optimistic assessment of population viability. In conclusion, simplifications of population structure and ignoring red environmental noise in population viability analyses can result in serious biases

SMR-technologies in hydrogen production

Abstract. This thesis goes out to explore the possibility of using small modular nuclear reactors (SMRs) in hydrogen production for industrial needs. Different types of hydrogen production technologies are examined in the thesis alongside small modular nuclear reactors. This work has been done to constitute an understanding of the requirements and limitations of nuclear hydrogen production in industrial settings. Additionally, the environmental impacts of nuclear hydrogen production methods are compared to traditional hydrogen production methods. The thesis has been done as a literature review. As society faces the problems of rising greenhouse gas emissions in the form of global warming, the importance of environmentally friendly energy solutions has increased. In recent years, the interest for the hydrogen economy has grown. Hydrogen has been introduced as an interesting resource for multiple energy applications. For example, hydrogen fuel cells are seen as a prospective option in the decarbonization of the transportation industry. Traditional hydrogen production methods rely on fossil fuels. The future development however is focused on water electrolysis since it produces almost pure hydrogen and is considered the most environmentally friendly hydrogen production technology. Water electrolysis is an energy intensive process. In this thesis, nuclear technologies are presented as a way of supplying the energy for hydrogen production instead of fossil fuels. This thesis presents benefits of using SMRs as the energy source for hydrogen production compared to the current production methods. The benefits include lower greenhouse gas emissions, predictable production conditions and higher total efficiency with cogeneration. The constraints of nuclear hydrogen production are presented in the thesis including the safety point of view, the efficiency issue and lacking infrastructure. SMR powered hydrogen production is lastly applied to industrial settings through a steel industry example. The hydrogen economy is constantly developing, and it is not yet clear how the future looks like in regards of it. The aim of this thesis is to present options for the development direction in the form of combining modern nuclear technologies with modern hydrogen technologies.SMR-teknologiat vedyn tuotannossa. Tiivistelmä. Tämän kandidaatintyön tarkoituksena on selvittää pienten modulaaristen ydinvoimateknologioiden (SMR-teknologiat) hyödyntämismahdollisuutta teollisuuden tarpeisiin. Työssä esitellään sekä vedyn tuotantotapoja että pieniä modulaarisia ydinreaktoreita. Työn tavoitteen on ollut muodostaa käsitys siitä, miten ydinvoimalla voidaan tuottaa vetyä. Ydinvoimalla tuotetun vedyn tuotantoteknologioiden kehityksen edellytykset ja rajoitukset esitetään työssä. Ydinvoimalla tuotetun vedyn ympäristövaikutuksia verrataan vallitseviin vedyn tuotantomenetelmiin. Työ on toteutettu kirjallisuuskatsauksena. Ympäristöystävällisten energiantuotantotapojen kysyntä on noussut, kun kasvihuonekaasujen pitoisuudet lisääntyvät ilmakehässä. Energiasektorilla vetytalous on ollut kasvava puheenaihe. Vety on esitetty ratkaisevana tekijänä monissa energiateknologian sovelluksissa. Esimerkiksi, vetypolttokennojen avulla voitaisiin muuntaa liikenne hiilineutraaliksi. Perinteiset vedyn tuotantomenetelmät hyödyntävät fossiilisia polttoaineita, mutta elektrolyysimenetelmiä pidetään tulevaisuuden merkittävimpänä vedyn tuotantotapana. Elektrolyysillä on mahdollista tuottaa melkein puhdasta vetyä ja sitä pidetään ympäristöystävällisimpänä vedyn tuotantomenetelmänä. Vedyn tuotanto elektrolyysillä vaatii kuitenkin paljon energiaa. Tässä kandidaatintyössä ydinteknologiat esitetään fossiilisten polttoaineiden korvaajina energiaintensiivisissä vedyn tuotantoprosesseissa. Tässä kandidaatintyössä esitellään myös SMR-teknologioiden mahdollisia hyötyjä vedyn tuotannossa verrattuna nykytuotantoon. Hyötyjä ovat muun muassa pienemmät kasvihuonekaasupäästöt, ennustettavissa ja säädettävissä olevat tuotanto-olosuhteet ja korkeampi kokonaistehokkuus yhteistuotannon avulla. Ydinvoimalla tuotetun vedyn rajoitukset, muun muassa turvallisuusnäkökulma ja vaillinainen infrastruktuuri, tuodaan esille. Viimeisenä SMR-teknologiat ja vedyn tuotanto yhdistetään teolliseen ympäristöön terästeollisuuden esimerkin kautta. Vetytalous kehittyy jatkuvasti eikä ole selvää, millaiselta se tarkalleen tulevaisuudessa näyttää. Tämän kandidaatintyön tarkoituksena on esitellä uusia mahdollisuuksia vetytalouden kehittymissuunnalle

Scale Analysis Suggests Frequent Skipping of Second Reproductive Season in Atlantic Herring

A common assumption in fish studies is that iteroparous fish, once mature, normally reproduce in all consecutive seasons. Analysis of scales from Norwegian spring-spawning herring collected between 1935-1973 revealed strong under-representation (47% of expected) of second-time spawners on the spawning grounds. This reduction is not explained satisfactorily by possible errors in scale-reading, suggesting that the second reproductive season is frequently skipped. Skipping a season may relate to trade-offs between growth, current and future reproduction, and survival, which are likely to be particularly strong for young adult herring

Comparing proactive and reactive management: Managing a transboundary fish stock under changing environment

Environmental change in general, and climate change in particular, can lead to changes in distribution of fish stocks. When such changes involve transboundary fish stocks, the countries sharing the stock need to reconsider their harvesting policies. We investigate the effects of changing stock distribution on the optimal fishing policies in a two players' non-cooperative game. We compare reactive management, under which the manager ignores future distributional shifts (knowingly or unknowingly), with proactive management where the manager considers such shifts in his decisions. A dynamic programming model is developed to identify closed-loop Nash strategies. We show that the role of two players is symmetric under reactive management but asymmetric under proactive management where managers anticipate future changes in stock ownership. The player loosing the stock tends to harvest more aggressively compared to the player gaining the stock who acts more conservatively. Strategic interactions show tendency for complementary actions that can change abruptly during the ownership transition. The differences between management regimes vary from quantitative to qualitative; differences are minimal for stocks with little or no schooling, whereas highly-schooling stocks may avoid collapse only under proactive management

Fisheries-induced Life History Changes in Herring (Clupea harengus)

Fishing changes not only the population abundance of the target species, but also its population dynamics and life-history traits. A number of studies have shown that life history traits related to the timing of maturation can respond quickly to fishing mortality. Because changes in such life-history traits feed back into population dynamics and, consequently, may also affect the yield and thus profitability of a fishery, we need better understand the factors that hasten or hinder such changes. In this study we analyze how fisheries have affected the maturation process of an economically important herring ("Clupea harengus") stock, the North Sea (NSH) herring. The harvest of North Sea herring targets both mature and immature individuals. Life-history theory predicts that under this kind of mortality regime fisheries can be expected to induce an adaptive decrease in the age at maturation. This kind of studies are a critical for testing theoretical predictions, and will facilitate our understanding under which conditions large life history changes can and cannot be expected. Such understanding is needed for evolutionarily enlightened management of marine biodiversity. The results will provide guidance for evolutionarily enlightened management strategies, particularly with respect to fisheries targeting mature and immature individuals differently

An overview of marine fisheries management in China

China is the world's largest country in terms of fish production, yet its fisheries management is comparatively unknown outside the country. This article gives an overview of the current management system and highlights some of its challenges. In the past thirty years, the Department of Fishery Administration has formulated and organized a series of conservation and management regimes and measures. The most important tools are minimum mesh size regulation and a range of input control measures, including seasonal closures and attempts to control fishing capacity through licensing and limiting total engine power. However, fisheries output is only controlled through a nation-wide total catch limit. Certain progress has been achieved, but there are still problems as the resource situation is poor. While the existing measures could, in principle, improve sustainability, their enforcement is insuffiient, and they do not limit fishing effort in a way that would allow recovery

Metapopulation-Level Adaptation of Insect Host plant Preference and Extinction-Colonization Dynamics in Heterogenous Landscapes

Species living in highly fragmented landscapes typically occur as metapopulations with frequent turnover of local populations. The turnover rate depends on population sizes and connectivities, but it may also depend on the phenotypic and genotypic composition of populations. The Glanville fritillary butterfly ("Melitaea cinxia") in Finland uses two host plant species, which show variation in their relative abundances at two spatial scales: locally among individual habitat patches and regionally among networks of patches. Female butterflies in turn exhibit spatial variation in genetically-determined host plant preference within and among patch networks. Emigration, immigration and establishment of new populations have all been shown to be strongly influenced by the match between the host plant composition of otherwise suitable habitat patches and the host plant preference of migrating butterflies. The evolutionary consequences of such biased migration and colonization with respect to butterfly phenotypes might differ depending on spatial configuration and plant species composition of the patches in heterogenous patch networks. Using a spatially realistic individual-based model we show that the model-predicted evolution of host plant preference due to biased migration explains a significant amount of the observed variation in host plant use among metapopulations living in dissimilar networks. This example illustrates how the ecological extinction-colonization dynamics may be linked with the evolutionary dynamics of life history traits in metapopulations