Biotic resistance to green crab, <Emphasis Type="Italic">Carcinus maenas</Emphasis>, in California bays

The distribution of the introduced European green crab, Carcinus maenas, was investigated in the central California embayments of Bodega Bay Harbor (BBH), Tomales Bay, and Bolinas Lagoon using baited traps and snorkel surveys. Adult green crabs were very spatially limited in all three embayments and occurred primarily in warm, shallow areas that lacked large native Cancer spp. crabs. The green crabs that were found in closest proximity to populations of Cancer spp. exhibited high levels of limb damage and loss; damage was strongly correlated with low ratios of intertidal area: edge, indicative of narrow areas of intertidal that are more easily accessed by large Cancer spp. moving up to forage during periods of tidal inundation. Up to 70% of the green crabs tethered in areas of BBH that are utilized by Cancer spp. experienced limb loss, while those tethered in the marsh, where there are no Cancer spp., were undamaged. The results suggest that the potential distribution of green crabs in the northeastern Pacific will be far less than has been predicted, and that their impacts may be largely attenuated through predation by and competition with native crab species.     

Testing for thresholds of ecosystem collapse in seagrass meadows

Although the public desire for healthy environments is clear‐cut, the science and management of ecosystem health has not been as simple. Ecological systems can be dynamic and can shift abruptly from one ecosystem state to another. Such unpredictable shifts result when ecological thresholds are crossed; that is, small cumulative increases in an environmental stressor drive a much greater change than could be predicted from linear effects, suggesting an unforeseen tipping point is crossed. In coastal waters, broad‐scale seagrass loss often occurs as a sudden event associated with human‐driven nutrient enrichment (eutrophication). We tested whether the response of seagrass ecosystems to coastal nutrient enrichment is subject to a threshold effect. We exposed seagrass plots to different levels of nutrient enrichment (dissolved inorganic nitrogen) for 10 months and measured net production. Seagrass response exhibited a threshold pattern when nutrient enrichment exceeded moderate levels: there was an abrupt and large shift from positive to negative net leaf production (from approximately 0.04 leaf production to 0.02 leaf loss per day). Epiphyte load also increased as nutrient enrichment increased, which may have driven the shift in leaf production. Inadvertently crossing such thresholds, as can occur through ineffective management of land‐derived inputs such as wastewater and stormwater runoff along urbanized coasts, may account for the widely observed sudden loss of seagrass meadows. Identification of tipping points may improve not only adaptive‐management monitoring that seeks to avoid threshold effects, but also restoration approaches in systems that have crossed them.     

The Tucson Mineral Show and the market for collector minerals: The potential for artisanal and small scale miners

Minerals that are sold to collectors are often produced by artisanal and small scale miners in many developing countries. The market for collector minerals is not well understood by most government agencies or NGOs but has a large impact on the artisanal and small miners that have the opportunity to produce these minerals because of the high prices that can be realized. This paper describes the collector mineral market that is held annually in Tucson, Arizona, that analyzes the competitive forces that affect the profitability of the mineral dealers at the show and describes potential methods for artisanal and small scale miners to participate successfully in the show. Most collector minerals produced by artisanal and small-scale miners are valued for their aesthetic qualities instead of mineral content. The 43 shows that operate during the first two weeks in February make up the largest gem and mineral show in the world, the Tucson Show. The Tucson Mineral Show is a subgroup of six shows that specialize primarily in collector minerals.There are several competitive forces at the Tucson Mineral Show that can affect the profit potential of dealers that participate in the show. These forces include potential entrants, suppliers, buyers, substitutes, and rivalry among existing competitors. New entrants face several barriers to entering the market place including the supply side economies of scale, demand side benefits of scale, and capital requirements. Because of these barriers, the cost of doing business and the way that promoters organize and manage the shows, it is difficult for artisanal and small scale miners to enter the show and compete with established dealers. However, with support from entities such as local governments, non-profit organizations, and international organizations the artisanal and small scale miners have the potential to have their minerals sold at the Tucson Shows for prices that would be greater than what can be achieved in the local market. Methods to help the artisanal and small scale miners compete include direct sales or consignments to retail dealers, tailgating, development of sales co-operatives, and the creation of an artisanal/small scale mineral show.     

Genetic structuring of <Emphasis Type="Italic">Latris lineata</Emphasis> at localized and transoceanic scales

Striped trumpeter (Latris lineata) is a demersal teleost distributed around the temperate clines of all the major oceans in the southern hemisphere. Within Tasmanian waters the species is managed as a single stock, although no studies have been performed to confirm genetic panmixia. A protracted pelagic larval phase and a recent transoceanic tag recapture of an adult fish suggest significant potential for genetic mixing between widely separated populations. Phylogenetic analysis of mitochondrial DNA control region sequences suggested no genetic mixing between Tasmania, New Zealand and St Paul/Amsterdam Islands, evidence for the first time that there is population structure at a transoceanic scale for this species. In addition, an analysis of molecular variance coupled with phylogenetic analyses suggested no significant structuring of striped trumpeter from three locations around Tasmania. The information provided in this study is useful for the design of modern fisheries management techniques such as spatially implemented marine reserves. In addition, species-by-species knowledge about population structures of marine species facilitates ecologically useful generalizations concerning their population dynamics and key issues on the broader ecology of the oceans.     

Ready or not: How do we accelerate the developmental readiness of leaders?

A theory of leader developmental readiness is examined comprised of leaders' motivation and ability to develop. Early theory-building and testing suggests leaders' motivation to develop is promoted through interest and goals, learning goal orientation, and developmental efficacy; while leaders' ability to develop is promoted through self-awareness, self-complexity, and meta-cognitive ability. Copyright © 2010 John Wiley & Sons, Ltd.     

A multi-criteria assessment of fishing gear impacts in demersal fisheries

Fishing gears have multiple impacts on the marine environment, and policies to reduce these impacts through modifying fishing gears are becoming common place. Different modifications result in different changes in the set of environmental impacts, and imply different sets of costs and benefits for different stakeholder groups. In this study, the analytic hierarchy process (AHP) is used to quantify the relative importance of the environmental impacts of fishing to different stakeholder groups. Forty eight individuals representing six different stakeholder groups (ecologists, biologists, economists, gear technologists, fishers and fisheries managers) were surveyed. As expected, fishers and gear technologists placed substantially greater importance on reducing discarding of commercial fish species than on habitat damage. Priorities of other stakeholder groups varied, but all placed greater priority on habitats than the commercial sector. The results suggest that management aimed at reducing environmental impacts of fishing broader than just discarding is appropriate, but such moves are likely to be opposed by the fishing industry. The derived weights also have a direct application to fisheries management, as they allow otherwise non-commensurate impacts to be aggregated into an overall impact to compare environmental benefits from alternative modifications of fishing gear.     

Emissions of volatile fatty acids from feed at dairy facilities

Recent studies suggest that dairy operations may be a major source of non-methane volatile organic compounds in dairy-intensive regions such as Central California, with short chain carboxylic acids (volatile fatty acids or VFAs) as the major components. Emissions of four VFAs (acetic acid, propanoic acid, butanoic acid and hexanoic acid) were measured from two feed sources (silage and total mixed rations (TMR)) at six Central California Dairies over a fifteen-month period. Measurements were made using a combination of flux chambers, solid phase micro-extraction fibers coupled to gas chromatography mass spectrometry (SPME/GC–MS) and infra-red photoaccoustic detection (IR-PAD for acetic acid only). The relationship between acetic acid emissions, source surface temperature and four sample composition factors (acetic acid content, ammonia-nitrogen content, water content and pH) was also investigated. As observed previously, acetic acid dominates the VFA emissions. Fluxes measured by IR-PAD were systematically lower than SPME/GC–MS measurements by a factor of two. High signals in field blanks prevented emissions from animal waste sources (flush lane, bedding, open lot) from being quantified. Acetic acid emissions from feed sources are positively correlated with surface temperature and acetic acid content. The measurements were used to derive a relationship between surface temperature, acetic acid content and the acetic acid flux. The equation derived from SPME/GC–MS measurements predicts estimated annual average acetic acid emissions of (0.7 + 1/?0.4) g m^?2 h^?1 from silage and (0.2 + 0.3/?0.1) g m^?2 h^?1 from TMR using annually averaged acetic acid content and meteorological data. However, during the summer months, fluxes may be several times higher than these values.