Density Dependence and the Economic Efficacy of Marine Reserves

Predictions on the efficacy of marine reserves for benefiting fisheries differ in large part due to considerations of models of either intra- or inter-cohort population density regulating fish recruitment. Here, I consider both processes acting on recruitment and show using a bioeconomic model how for many fisheries density dependent recruitment dynamics interact with harvest costs to influence fishery profit with reserves. Reserves consolidate fishing effort, favoring fisheries that can profitably harvest low-density stocks of species where adult density mediates recruitment. Conversely, proportion coastline in reserves that maximizes profit, and relative improvement in profit from reserves over conventional management, decline with increasing harvest costs and the relative importance of intra-cohort density dependence. Reserves never increase profit when harvest cost is high, regardless of density dependent recruitment dynamics. I quantitatively synthesize diverse results in the literature, show disproportionate effects on the economic performance of reserves from considering only inter- or intra-cohort density dependence, and highlight fish population and fishery dynamics predicted to be complementary to reserve management

Hunters ring dinner bell for ravens: Experimental evidence of a unique foraging strategy

We have long known that corvids are adaptively flexible in behavior, but have rarely tested their flexibility and creativity in solving problems outside the laboratory. Through a carefully controlled experiment conducted in the wild, I have found that Common Ravens (Corvus corax) fly toward gunshot sounds, presumably in order to locate animal gut piles left by hunters. This is the first conclusive evidence of any scavenger species pursuing gunshots. Furthermore, ravens exhibited this behavior only when gunshots were fired from within forested habitat, when the shots may be most valuable to them for locating gut piles. Interestingly, raven behaviors suggest that they may have learned the usefulness of gunshots by substituting them for other previously known sounds already used to locate food in the wild

Size frequency variation of an emerging fisheries species across its biogeographical range

Kellet\u27s whelk (Kelletia kelletii), a large subtidal gastropod is the basis for an emerging bycatch fishery in California. This commercial fishery has increased dramatically in the past two decades, but there is little biological information available to inform its management. There are currently no size limits and only seasonal restrictions for commercial and recreational fishing for Kellet’s whelk in California with annual total allowable catch at 100,000 pounds. After surveying 28 subtidal rocky reefs across the Kellet’s whelk range, our results indicate large natural variation in size frequencies, specifically between the mainland and island populations. Designing harvesting strategies that would maintain these size frequency distributions – e.g., a larger size limit at the islands and a smaller size limit at the mainland populations -- may generate more sustainable and productive economic and ecological outcomes

Convergence Properties of the Waveform Relaxation Method as Applied to Electric Power Systems

Several theoretical results are presented and simple examples examined in order to determine the suitability of waveform relaxation for transient power system simulation. This examination leads to two practical suggestions that can easily be satisfied for power systems. The first is to break the simulation interval into sections, the first of which should be narrow and be used to kill off errors in the initial guess that activate the stiff modes. The second is to partition the system into subsystems that are stable, as this not only aids convergence but ensures multirate numerical stability

Do marine protected areas affect emerging fisheries population density?

Kellet’s whelk, Kelletia kelletii, were observed at sample sites throughout their range from Baja California, Mexico, to Monterey, CA to determine patterns of population density. Sample sites in each region were either located within California marine protected areas where take of the Kellet’s whelk in prohibited, or in non-protected areas where the whelks can be fished both commercially and recreationally. Kellet’s whelk population density was compared between all MPA and non-MPA sample sites. These mean densities were also found for sites in Santa Barbara and San Diego near active fishing ports and compared to data from the same sites collected in 2004. Whelk density was significantly greater in MPAs than in non-MPA sample sites. Moreover, the comparison of MPA and non-MPA sites near fishing ports between 2004 and 2015 data showed non-significant changes in density over the 11 years, but there were noticeable trends in decreasing density in the fished areas while the density in the MPAs remained fairly constant. Our results suggest that fishing pressure has caused a decreased density of Kellet’s whelk in fished areas, while these effects have been mitigated in protected areas. Significant decreases in density of the Kellet’s whelk could alter kelp forest population dynamics, and although the overall population is currently stable, consumers must be aware of overfishing

Environmental and Economic Implications of Alternative Cruise Ship Pathways in Bermuda

As the cruise ship industry moves towards ever larger vessels, many tourist destinations are faced with dilemmas about how to accommodate the latest generation of ships, which require deeper and wider shipping pathways. The location of nearshore shipping channels traveled by cruise ships has important environmental and economic implications, as dredging larger lanes damages habitat, ship traffic produces sediment plumes that can smother adjacent sensitive habitats (e.g., coral reefs, seagrass beds), and dredging costs vary spatially. These environmental and economic costs should ideally be evaluated in the context of projected benefits from increased tourism. To inform decision-making on cruise ship pathway design, we evaluated tradeoffs among tourism revenue to the local economy, dredging costs, direct coral damage and sedimentation impacts to coral reefs of alternative cruise ship approach channels for the island of Bermuda. We compiled economic data on cruise tourism and dredging costs and developed a sediment particle tracking model, overlaid on maps of coral cover, to track the spread of sediment particles and resulting coral sedimentation caused by cruise ships. Using our models we compared two viable routes, if dredged, for larger ships to reach Bermuda, along with a scenario of no dredging in which the next generation of larger ships is not accommodated. Our tradeoff analysis shows that the status quo (no dredging; no larger ships) scenario performs relatively well except for the risk of a significant loss in tourism revenue. When selecting between the two channel upgrade scenarios, the south channel upgrade is preferable if dredged material can be reused, thereby recouping dredging costs; otherwise, there is a strong tradeoff between upgrade costs and coral sedimentation. While developed with data layers and inputs specific to Bermuda, this analytical approach could easily be configured to other locations facing similar spatial planning decisions about whether and where to allow pathways for larger cruise ships

Potential Environmental Effects of Deepwater Floating Offshore Wind Energy Facilities

Over the last few decades, the offshore wind energy industry has expanded its scope from turbines mounted on foundations driven into the seafloor and standing in less than 60 m of water, to floating turbines moored in 120 m of water, to prospecting the development of floating turbines moored in ~1,000 m of water. Since there are few prototype turbines and mooring systems of these deepwater, floating offshore wind energy facilities (OWFs) currently deployed, their effects on the marine environment are speculative. Using the available scientific literature concerning appropriate analogs, including fixed-bottom OWFs, land-based wind energy facilities, wave and tidal energy devices, and oil and gas platforms, we conducted a qualitative systematic review to estimate the potential environmental effects of deepwater, floating OWFs during operation, as well as potential mitigation measures to address some of the effects. We evaluated six categories of potential effects: changes to atmospheric and oceanic dynamics due to energy removal and modifications, electromagnetic field effects on marine species from power cables, habitat alterations to benthic and pelagic fish and invertebrate communities, underwater noise effects on marine species, structural impediments to wildlife, and changes to water quality. Our synthesis of 89 articles selected for the review suggests that many of these potential effects could be mitigated to pose a low risk to the marine environment if developers adopt appropriate mitigation strategies and best-practice protocols. This review takes the necessary first steps in summarizing the available information on the potential environmental effects of deepwater, floating OWFs and can serve as a reference document for marine scientists and engineers, the energy industry, permitting agencies and regulators of the energy industry, project developers, and concerned stakeholders such as coastal residents, conservationists, and fisheries

COLLECTIVE POLITICS OF FOODGRAINS MARKETS IN SOUTH ASIA

Summary With the help of case material from Tamil Nadu, West Bengal and Bangladesh, the politics of market organization is examined. Political parties do not have consistent positions on private trade and are responded to opportunistically by foodgrains traders. Traders are politically active in a variety of local religious and social service institutions within which they build networks. The commodity association is the principal arena of mercantile politics. Formed defensively in response to threats by the state or by unionized labour, they have developed systematic lobbying capability. They have also developed self?regulatory functions, extending to physical security, law and order and enforcement of the terms of participation of smaller traders. The article concludes by discussing the implications of such politics for state intervention. Resumé La politique collective des marchés de graine alimentaire en Asie du sud L'article examine l'aspect politique de l'organisation des marchés sous forme d'études de cas au Tamil Nadu, au Bengal de l'Ouest, et au Bangladesh. La position des partis politiques sur le commerce privé est ni uniforme ni constante, ainsi la réponse des négociants en graine alimentaires y est opportuniste. L'activité politique des négociants se constate dans une variété d'institutions locales (religion; services sociaux) au sein desquelles elles fondent des réseaux. L'association commoditaire est le plus important foyer de la politique mercantile. Formées en tant que réponse défensive à la menace de l'état ou de la syndicalisation de la main?d'oeuvre, ces associations ont développé des capacités de sollicitation systématique. Elles ont également développé des fonctions autorégulatrices qui pénètrent jusque dans la sécurité physique, l'ordre public, et la mise en vigueur des termes de participation qui contrôlent les moins importants négociants. L'article aboutit à une discussion des implications des politiques de ce genre sur l'intervention de l'état. Resumen La política colectiva de los mercados de granos en Asia del sur Se examinan en este artículo las políticas de organización de mercado con la ayuda de información proveniente de experiencias en Tamil Nadu, Bengala Occidental y Bangladesh. Los partidos políticos no mantienen posiciones consistentes con respecto al comercio privado y reciben reacciones oportunistas por parte de los comerciantes en granos. Estos últimos son políticamente muy activos en una variedad de instituciones de servicio sociales y religiosas dentro de las cuales construyen redes de comunicación. La asociación de productores es el principal escenario de la política mercantil. Formada como defensa a las amenazas del estado o de los sindicatos, ha desarrollado una sistemática capacidad para cabildeos. También has desarrollado funciones auto?regulatorias, que se extienden hasta la seguridad física, el orden público y la aplicación efectiva de los términos de participación de los pequeños comerciantes. El artículo concluye examinando las implicaciones que estas pautas pueden tener para la intervención estatal

Assessment of surface wind datasets for estimating offshore wind energy along the Central California Coast

In the United States, Central California has gained significant interest in offshore wind energy due to its strong winds and proximity to existing grid connections. This study provides a comprehensive evaluation of near-surface wind datasets in this region, including satellite-based observations (QuikSCAT, ASCAT, and CCMP V2.0), reanalysis (NARR and MERRA), and regional atmospheric models (WRF and WIND Toolkit). This work highlights spatiotemporal variations in the performance of the respective datasets in relation to in-situ buoy measurements using error metrics over both seasonal and diurnal time scales. The two scatterometers(QuikSCAT and ASCAT) showed the best overall performance, albeit with significantly less spatial and temporal resolution relative to other datasets. These datasets only slightly outperformed the next best dataset (WIND Toolkit), which has significantly greater temporal and spatial resolution as well as estimates of winds aloft. Considering tradeoffs between spatiotemporal resolution of the underlying datasets, error metrics relative to in-situ measurements, and the availability of data aloft, the WIND Toolkit appears to be the best dataset for this region. The framework and tradeoff analysis this research developed and demonstrated to assess offshore wind datasets can be applied in other regions where offshore wind energy is being considered