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1.
Marine fisheries are in a state of crisis. One of the few successfully managed fisheries is the Maine lobster industry where catches are at an all time high. An important factor in this success is the effectiveness of regulations which were developed during three periods over the course of the past 125 years. In all cases, the regulations are the result of heavy lobbying activity by various factions in the industry. Both strong commercial rivalry and genuine concern for the well-being of the lobster resource played a role in generating these regulations. However, history did not repeat itself. In each period, the players, circumstances, and goals were very different. The result, however, is a set of effective regulations which are largely self-enforcing.  相似文献   

2.
The current crisis in the world's fisheries indicates the need for a different management method than that now used by Western scientists, which regulates the quantity of fish taken. The authors propose a method called parametric management, which takes into account the complex, chaotic nature offish stocks and emphasizes preserving regular biological processes in the life cycle of fish by controlling how people fish. Supporting data come from 28 folk societies, the Maine lobster industry, and the authors' mathematical model of fish stocks.  相似文献   

3.
In this article, we use game theory to understand the emergence of various kinds of territorial arrangements in the Maine lobster fishery during the past century. Using the Nash equilibria of models of the fishery as our theoretical framework, we show that informal territorial arrangements in this fishery went through three sequential stages. These stages are the result of decisions by groups of lobster fishermen to defend fishing areas or invade those of other groups. A large number of factors influence these defensive and offensive strategies: concentrations of lobsters, the adoption of better technology, transportation costs, ecological changes, trap monitoring costs, the ability to organize defensive and offensive groups, and better law enforcement---all of which are captured by crucial parameters of our model. We argue that this technique can be applied to elucidate territorial changes more generally.  相似文献   

4.
One of the basic tenets of the theory of common property resources is that private property rights work to conserve natural resources. There is growing evidence, however, that some large forest owners in Maine are cutting their forests heavily, using poor-quality silviculture techniques. This overexploitation is being done by paper companies, forest contractors, and some private land owners, who are being motivated by very different sets of factors. This article explores the reasons that private owners of forest resources are overexploiting their own lands and the implications of this for the theory of common property resources. Secure private property rights alone will not be enough to conserve resources and do away with externalities when the owners are operating in a system demanding constant short-term profits, where they are producing undifferentiated commodities in a highly competitive market, where the future value of slow-growing resources is very low, and where harvesting has so many ramifying biological and social effects.  相似文献   

5.
A number of theoretical and methodological problems plague studies of sex allocation in hermaphroditic plants. Most models assume that consumable resources limit reproduction, yet one or both sexes may be mate-limited. Most models also assume that resource limitation causes trade-offs between the allocations to male and female functions, but the sexes may be limited by different critical resources, or their resource needs may not overlap in time. Problems arise in deciding which plant parts are reproductive, when to harvest them, how to apportion them to male and female roles, and what are the appropriate measures of their cost. When energy directly limits reproduction, or other needs can be translated into energetic costs, the great variation in composition of reproductive parts makes construction costs or respiration a more potentially accurate measure of investment than energy content or especially biomass. Some simple predictions from theoretical models include a 1:1 allocation ratio to male and female function in outcrossing hermaphrodites, a female-biassed ratio in proportion to the level of selfing, and lower average allocations to male function in animal-pollinated than in windpollinated plants. These predictions have not received much support from existing studies, thus emphasizing the need for better measures of allocation as well as better accounting of the many other possible factors that may determine individual (and population) allocation ratios.  相似文献   

6.

Background

Ecologists, fisheries scientists, and coastal managers have all called for an ecosystem approach to fisheries management, yet many species such as the American lobster (Homarus americanus) are still largely managed individually. One hypothesis that has yet to be tested suggests that human augmentation of lobster diets via the use of Atlantic herring (Clupea harengus) as bait may contribute to recent increases in lobster landings. Currently 70% of Atlantic herring landings in the Gulf of Maine are used as bait to catch lobsters in traps throughout coastal New England.

Methodology/Principal Findings

We examined the effects of this herring bait on the diet composition and growth rate of lobsters at heavily baited vs. seasonally closed (i.e., bait free) sites in coastal Maine. Our results suggest that human use of herring bait may be subsidizing juvenile lobster diets, thereby enhancing lobster growth and the overall economic value and yield of one of the most valuable fisheries in the U.S.

Conclusions/Significance

Our study illustrates that shifting to an ecosystem approach to fisheries management should require consideration of cross-fishery interactions.  相似文献   

7.
The primary explanation for the latitudinal gradient in species diversity must lie in why species fail to expand ranges across different climatic regimes. Theories of species gradients based in niche conservatism assume that whole clades are confined to particular climatic regimes because the traits they share limit adaptation to alternative regimes. We assess these theories in an analysis of the twofold decline in bird species richness along the Himalayas from the southeast to the northwest. The presence of fewer species in the northwest is entirely due to a steep decline in the number of forest species; species occupying more open habitats show a reversed gradient. Forest species numbers are exceptionally high at midelevations (1,000-2,000 m) in the southeast, which experience a warm, wet climate not present in the northwest, and a high proportion of these species fail to expand their range to the northwest. Despite this, many species do have populations or close relatives that straddle different climatic regimes along altitudinal gradients and/or the regional gradient, implying that climate-based niche conservatism per se does not strongly constrain range limits. We argue that climate- and competition-mediated resource distributions are important in setting northerly range limits and show that one measure of forest resources (foliage density) is lower in the northwest.  相似文献   

8.
Species from many different habitats are responding to recent climate change. Mountainous areas are of particular interest as they provide pronounced gradients and have experienced above-average temperature increases. Data from the beginning of the 20th century of both the upper and lower range limits of plants of the European Alps were updated a century later and analyzed in order to identify common trends and deviating patterns of shifts at opposing ends of species’ ranges. At the upper limit, there was a strong trend towards an increase in species richness per summit, including 33 species that were recorded for the first time on any of the investigated summit areas. The species experienced a consistent upward shift exceeding 100 elevational meters, and 49 out of the 125 investigated species shifted upwards to a present altitude which is higher than any reported occurrence in the region one century ago. The response at the lower range limit was more heterogeneous and suggests species-specific differences in responsiveness and response patterns. With this approach of the combined analysis of upper and lower range limits along elevational gradients, it is possible to identify candidate species that might not keep pace with climate change, and thus, might face an increased risk of extinction with continued global warming.  相似文献   

9.
A sensitive method has been developed for the trace analysis of alkyl alkylphosphonic acids, metabolites of nerve agents, in urine using a benchtop ion trap mass spectrometer. The acids were isolated from urine by simple solid phase extraction and converted to their pentafluorobenzyl esters. An ion trap mass spectrometer in selected reaction monitoring mode provided limits of detection of 0.1 ng/ml for isopropyl, isobutyl, pinacolyl and cyclohexyl methylphosphonic acids and for ethyl ethylphosphonic acid. The detection limit for ethyl methylphosphonic acid was higher (0.5 ng/ml) due to a lower recovery.  相似文献   

10.
Measured foraging strategies often cluster around values thatmaximize the ratio of energy gained over energy spent whileforaging (efficiency), rather than values that would maximizethe long-term net rate of energy gain (rate). The reasons forthis are not understood. This paper focuses on time and energyconstraints while foraging to illustrate the relationship betweenefficiency and rate-maximizing strategies and develops modelsthat provide a simple framework to analyze foraging strategiesin two distinct foraging contexts. We assume that while capturingand ingesting food for their own use (which we term feeding),foragers behave so as to maximize the total net daily energeticgain. When gathering food for others or for storage (which weterm provisioning), we assume that foragers behave so as tomaximize the total daily delivery, subject to meeting theirown energetic requirements. In feeding contexts, the behaviormaximizing total net daily gain also maximizes efficiency whendaily intake is limited by the assimilation capacity. In contrast,when time available to forage sets the limit to gross intake,the behavior maximizing total net daily gain also maximizesrate. In provisioning contexts, when daily delivery is constrainedby the energy needed to power self-feeding, maximizing efficiencyensures the highest total daily delivery. When time needed torecoup energetic expenditure limits total delivery, a low self-feedingrate relative to the rate of energy expenditure favors efficientstrategies. However, as the rate of self-feeding increases,foraging behavior deviates from efficiency maximization in thedirection predicted by rate maximization. Experimental manipulationsof the rate of self-feeding in provisioning contexts could bea powerful tool to explore the relationship between rate andefficiency-maximizing behavior.  相似文献   

11.
To forecast marine disease outbreaks as oceans warm requires new environmental surveillance tools. We describe an iterative process for developing these tools that combines research, development and deployment for suitable systems. The first step is to identify candidate host–pathogen systems. The 24 candidate systems we identified include sponges, corals, oysters, crustaceans, sea stars, fishes and sea grasses (among others). To illustrate the other steps, we present a case study of epizootic shell disease (ESD) in the American lobster. Increasing prevalence of ESD is a contributing factor to lobster fishery collapse in southern New England (SNE), raising concerns that disease prevalence will increase in the northern Gulf of Maine under climate change. The lowest maximum bottom temperature associated with ESD prevalence in SNE is 12°C. Our seasonal outlook for 2015 and long-term projections show bottom temperatures greater than or equal to 12°C may occur in this and coming years in the coastal bays of Maine. The tools presented will allow managers to target efforts to monitor the effects of ESD on fishery sustainability and will be iteratively refined. The approach and case example highlight that temperature-based surveillance tools can inform research, monitoring and management of emerging and continuing marine disease threats.  相似文献   

12.
Market analysis of biosensors for food safety   总被引:4,自引:0,他引:4  
This paper is presented as an overview of the pathogen detection industry. The review includes pathogen detection markets and their prospects for the future. Potential markets include the medical, military, food, and environmental industries. Those industries combined have a market size of $563 million for pathogen detecting biosensors and are expected to grow at a compounded annual growth rate of 4.5%. The food market is further segmented into different food product industries. The overall food-pathogen testing market is expected to grow to $192 million and 34 million tests by 2005. The trend in pathogen testing emphasizes the need to commercialize biosensors for the food safety industry as legislation creates new standards for microbial monitoring. With quicker detection time and reusable features, biosensors will be important to those interested in real time diagnostics of disease causing pathogens. As the world becomes more concerned with safe food and water supply, the demand for rapid detecting biosensors will only increase.  相似文献   

13.
Despite the dominant role service industries play in modern society, those industries have by and large not been involved in the strong efforts underway to create environmentally responsible operations. Part of the reason is that the role of these industries as driving factors in resource flows has not been recognized. Perhaps more important, no common framework for assessing the environmental responsibility of service industries has been established. This article provides such a framework and applies it to a generic service industry: automotive repair. Among the results are that evaluation must take different forms for different types of services, and that the approaches of service industries to the use of buildings and equipment will require innovative solutions quite unlike those advocated for the "greening" of manufacturing operations.  相似文献   

14.
15.
Tumors are rare in crustaceans, and whereas a few have been reported from the lobster Homarus americanus none have been adequately described. A lobster with an unusual, large, blue-colored tumor-like growth projecting laterally outward from the first abdominal somite was caught off Stonington, Maine, USA. The growth was rugose and covered by a relatively normal appearing cuticle with dispersed focal melanization. The underlying stroma consisted of an internal area of rescaffolded fibrous connective tissue, restructured muscle fibers, few arterioles, and an epidermal area comprised of columnar, highly vacuolated epithelial cells. No infectious pathogens or unusual inclusions were observed with microscopy and no eukaryotic pathogens were detected via molecular sequencing. Given the nature of the histology and the appearance of the growth, we identify the mass as a benign papilliform hamartoma that likely originated as a result of abnormal wound repair possibly initiated around ecdysis. This represents the first tumor-like hamartoma reported from a lobster, and the second hamartoma reported from a crustacean.  相似文献   

16.
Pheromone trap types and within-field trap locations were compared for their effectiveness in monitoring the flight activity of European corn borer, Ostrinia nubilalis (Hübner), and its relationship to egg mass density and crop damage in sweet corn in central Maine from 1995 to 1996. The use of both 3:97 Z:E-11-tetradecenyl acetate and 97:3 Z:E-11 tetradecenyl acetate pheromone blends confirmed that European corn borer in central Maine is attracted to both pheromone lure types. European corn borer moths were captured predominantly with the E-lure type than with the Z-lure type in both years. The Scentry Heliothis trap was more effective than the Multi-Pher trap, but similar to the pheromone-baited water pan trap for monitoring European corn borer flights. With the Scentry Heliothis trap, the grassy border and 1st corn rows were the best locations for moth capture during the early flight period, but during the peak flight period, traps located in the middle of the field caught the most moths. Corn damage was recorded before moth captures in some sites and before egg mass counts in others, indicating poor efficacy of traps for early flights. Significant and positive correlations were found between moth captures in the midfield location and egg mass counts, and corn leaf damage, and between egg mass counts and corn leaf damage. However, low coefficients of variation suggest that pheromone trap captures were not good predictors of European corn borer leaf damage in sweet corn.  相似文献   

17.
Although the ostrich fern, Matteuccia struthiopteris,is distributed throughout much of the Northern Hemisphere, its consumption as a spring vegetable has been largely restricted to the tables of the Maritime Provinces in Canada and neighboring Maine in the United States. However, in little more than a decade the demand has expanded beyond these traditional boundaries, due to the present availability of the frozen product. The heart of the industry is undoubtedly New Brunswick. The harvest of 200 t/yr is approximately 4 times that of Maine, and from an historical vantage the traditional use as a spring vegetable is with the New Brunswickers as well. In light of the present high demand for the product and the reports of localized overpicking, a review of the economic history, resource management and attempts at cultivation is presented.  相似文献   

18.
Social networks with positive and negative links often split into two antagonistic factions. Examples of such a split abound: revolutionaries versus an old regime, Republicans versus Democrats, Axis versus Allies during the second world war, or the Western versus the Eastern bloc during the Cold War. Although this structure, known as social balance, is well understood, it is not clear how such factions emerge. An earlier model could explain the formation of such factions if reputations were assumed to be symmetric. We show this is not the case for non-symmetric reputations, and propose an alternative model which (almost) always leads to social balance, thereby explaining the tendency of social networks to split into two factions. In addition, the alternative model may lead to cooperation when faced with defectors, contrary to the earlier model. The difference between the two models may be understood in terms of the underlying gossiping mechanism: whereas the earlier model assumed that an individual adjusts his opinion about somebody by gossiping about that person with everybody in the network, we assume instead that the individual gossips with that person about everybody. It turns out that the alternative model is able to lead to cooperative behaviour, unlike the previous model.  相似文献   

19.
The American lobster is a poikilotherm that inhabits a marine environment where temperature varies over a 25°C range and depends on the winds, the tides and the seasons. To determine how cardiac performance depends on the water temperature to which the lobsters are acclimated we measured lobster heart rates in vivo. The upper limit for cardiac function in lobsters acclimated to 20°C is approximately 29°C, 5°C warmer than that measured in lobsters acclimated to 4°C. Warm acclimation also slows the lobster heart rate within the temperature range from 4 to 12°C. Both effects are apparent after relatively short periods of warm acclimation (3–14 days). However, warm acclimation impairs cardiac function at cold temperatures: following several hours exposure to frigid (<5°C) temperatures heart rates become slow and arrhythmic in warm acclimated, but not cold acclimated, lobsters. Thus, acclimation temperature determines the thermal limits for cardiac function at both extremes of the 25°C temperature range lobsters inhabit in the wild. These observations suggest that regulation of cardiac thermal tolerance by the prevailing environmental temperature protects against the possibility of cardiac failure due to thermal stress.  相似文献   

20.
The mechanisms by which Venus's Flytrap (Dionaea muscipula Ellis) close are not clearly understood, and several conflicting models have been proposed. We have measured the dynamics of five trap tissues from three trap regions during full closure of young, fully developed, previously unclosed traps. Closure was divided into three distinct stages: 1) Capture–occurred immediately after stimulation of the trigger hairs and involved the rapid inward flexure of the trap margin and tynes. This motion interlocked the tynes, effectively capturing the prey. This was the only rapid movement of the trap; 2) Appression–completed by 30 min poststimulation, was characterized by contact of the margins; and 3) Sealing–completed by 1 hr poststimulation, was characterized by a sealed “digestive” sac formed around the potential prey, also by tight appression and recurved bending of the trap–margins. Major tissue dynamics that facilitated changes in trap morphology (hence, closure) occurred in different regions of the trap during different periods of time. The first regions where activity occurred were the A and C regions (Fig. 1), after approximately 15 min poststimulation; tissues in the C regions were most active followed by those in the B region of the trap (30 min to 1 hr poststimulation). Thus, shape changes during each stage of closure were the result of temporally separated changes in trap tissue volume. The complete sequence of events was elicited by a single 5–sec period of trigger hair stimulation. Our study showed that changes in the curvature of the trap during closure involved the expansion of opposing tissue groups (i.e., on opposite sides of trap medullary tissues). The pressure from contact of opposing trap lobes during the Appression stage may play an important role in regulating further trap closure and morphology.  相似文献   

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