16 resultados para modulation area structure
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Executive Summary: Tropical marine ecosystems in the Caribbean region are inextricably linked through the movement of pollutants, nutrients, diseases, and other stressors, which threaten to further degrade coral reef communities. The magnitude of change that is occurring within the region is considerable, and solutions will require investigating pros and cons of networks of marine protected areas (MPAs), cooperation of neighboring countries, improved understanding of how external stressors degrade local marine resources, and ameliorating those stressors. Connectivity can be broadly defined as the exchange of materials (e.g., nutrients and pollutants), organisms, and genes and can be divided into: 1) genetic or evolutionary connectivity that concerns the exchange of organisms and genes, 2) demographic connectivity, which is the exchange of individuals among local groups, and 3) oceanographic connectivity, which includes flow of materials and circulation patterns and variability that underpin much of all these exchanges. Presently, we understand little about connectivity at specific locations beyond model outputs, and yet we must manage MPAs with connectivity in mind. A key to successful MPA management is how to most effectively work with scientists to acquire the information managers need. Oceanography connectivity is poorly understood, and even less is known about the shape of the dispersal curve for most species. Dispersal kernels differ for various systems, species, and life histories and are likely highly variable in space and time. Furthermore, the implications of different dispersal kernels on population dynamics and management of species is unknown. However, small dispersal kernels are the norm - not the exception. Linking patterns of dispersal to management options is difficult given the present state of knowledge. The behavioral component of larval dispersal has a major impact on where larvae settle. Individual larval behavior and life history details are required to produce meaningful simulations of population connectivity. Biological inputs are critical determinants of dispersal outcomes beyond what can be gleaned from models of passive dispersal. There is considerable temporal and spatial variation to connectivity patterns. New models are increasingly being developed, but these must be validated to understand upstream-downstream neighborhoods, dispersal corridors, stepping stones, and source/sink dynamics. At present, models are mainly useful for providing generalities and generating hypotheses. Low-technology approaches such as drifter vials and oceanographic drogues are useful, affordable options for understanding local connectivity. The “silver bullet” approach to MPA design may not be possible for several reasons. Genetic connectivity studies reveal divergent population genetic structures despite similar larval life histories. Historical stochasticity in reproduction and/or recruitment likely has important, longlasting consequences on present day genetic structure. (PDF has 200 pages.)
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ENGLISH: Since its inception in 1950 by agreement between the Republic of Costa Rica and the United States of America, the Inter-American Tropical Tuna Commission has been engaged in studies of the biology, ecology and population dynamics of yellowfin tuna in the eastern Pacific Ocean. Prime consideration has been given to the evaluation of the effects of fishing pressure on the yellowfin tuna in this area in order to estimate the maximum sustainable yield. A portion of the eastern Pacific has been defined by the Inter-American Tropical Tuna Commission (1963) as a regulatory area for yellowfin tuna (Figure 1). SPANISH: Desde su incepción en 1950, por un acuerdo entre la República de Costa Rica y los Estados Unidos de América, la Comisión Interamericana del Atún Tropical ha estado ocupada en los estudios de la biología, ecología y dinámica de las poblaciones del atún aleta amarilla en el Océano Pacífico Oriental. Se consideró primariamente la evaluación de los efectos de la presión de la pesquería sobre el atún aleta amarilla en esta área, para poder estimar el rendimiento máximo sostenible. Una parte del Pacífico Oriental ha sido definida por la Comisión Interamericana del Atún Tropical (1963), como área de reglamentación del atún aleta amarilla (Figura 1). (PDF contains 60 pages.)
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The effects of some socio-economic variables on the performance of artisanal fishermen were investigated. The variables include the age-structure of the fishermen, level of investment, educational background, membership of co-operative societies and marketing arrangements. All these variables were found to be crucial to productivity in the artisanal fishing sector
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Upland stream systems have been extensively investigated in Europe, North America and Australasia and many of the central ideas concerning their function are based on these systems. One central paradigm, the river continuum concept is ultimately derived from those North American streams whose catchments remain forested with native vegetation. Streams of the tropics may or may not fit the model. They have been little studied. The Amani Nature Reserve in the East Usambara Mountains of north-eastern Tanzania offers an opportunity to bring these naturally forested systems to the attention of the ecological community. This article describes a comparison made between two lengths of the River Dodwe in this area. The work was carried out by a group of postgraduate students from eighteen European and African countries with advice from five staff members, as part of a course organised by the Tropical Biology Association. Rigorous efforts were made to standardise techniques, in a situation where equipment and laboratory facilities were very basic, through a management structure and deliberate allocation of work to specialists in each area.The article offers a summary of invertebrate communities found in the stream and its biomass. Crabs seem to be the key organism in both sections of the streams.
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A portion of the Oculina Bank located off eastern Florida is a marine protected area (MPA) preserved for its dense populations of the ivory tree coral (Oculina varicosa), which provides important habitat for fish. Surveys of fish assemblages and benthic habitat were conducted inside and outside the MPA in 2003 and 2005 by using remotely operated vehicle video transects and digital still imagery. Fish species composition, biodiversity, and grouper densities were used to determine whether O. varicosa forms an essential habitat compared to other structure-forming habitats and to examine the effectiveness of the MPA. Multivariate analyses indicated no differences in fish assemblages or biodiversity among hardbottom habitat types and grouper densities were highest among the most complex habitats; however the higher densities were not exclusive to coral habitat. Therefore, we conclude that O. varicosa was functionally equivalent to other hardbottom habitats. Even though fish assemblages were not different among management areas, biodiversity and grouper densities were higher inside the MPA compared to outside. The percentage of intact coral was also higher inside the MPA. These results provide initial evidence demonstrating effectiveness of the MPA for restoring reef fish and their habitat. This is the first study to compare reef fish populations on O. varicosa with other structure-forming reef habitats and also the first to examine the effectiveness of the MPA for restoring fish populations and live reef cover.
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The Pacific Rim population structure of chum salmon (Oncorhynchus keta) was examined with a survey of microsatellite variation to describe the distribution of genetic variation and to evaluate whether chum salmon may have originated from two or more glacial refuges following dispersal to newly available habitat after glacial retreat. Variation at 14 microsatellite loci was surveyed for over 53,000 chum salmon sampled from over 380 localities ranging from Korea through Washington State. An index of genetic differentiation, FST, over all populations and loci was 0.033, with individual locus values ranging from 0.009 to 0.104. The most genetically diverse chum salmon were observed from Asia, particularly Japan, whereas chum salmon from the Skeena River and Queen Charlotte Islands in northern British Columbia and those from Washington State displayed the fewest number of alleles compared with chum salmon in other regions. Differentiation in chum salmon allele frequencies among regions and populations within regions was approximately 18 times greater than that of annual variation within populations. A regional structuring of populations was the general pattern observed, with chum salmon spawning in different tributaries within a major river drainage or spawning in smaller rivers in a geographic area generally more similar to each other than to populations in different major river drainages or geographic areas. Population structure of chum salmon on a Pacific Rim basis supports the concept of a minimum of two refuges, northern and southern, during the last glaciation, but four possible refuges fit better the observed distribution of genetic variation. The distribution of microsatellite variation of chum salmon on a Pacific Rim basis likely reflects the origins of salmon radiating from refuges after the last glaciation period.
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We investigated the use of otolith morphology to indicate the stock structure of an exploited serranid coral reef fish, Plectropomus leopardus, on the Great Barrier Reef (GBR), Australia. Otoliths were measured by traditional one-and two-dimensional measures (otolith length, width, area, perimeter, circularity, and rectangularity), as well as by Fourier analysis to capture the finer details of otolith shape. Variables were compared among four regions of the GBR separated by hundreds of kilometers, as well as among three reefs within each region, hundreds of meters to tens of kilometers apart. The temporal stability in otolith structure was examined by comparing two cohorts of fully recruited four-year-old P. leopardus collected two years before and two years after a signif icant disturbance in the southern parts of the GBR caused by a large tropical cyclone in March 1997. Results indicated the presence of at least two stocks of P. leopardus, although the structure of each stock varied depending on the cohort considered. The results highlight the importance of incorporating data from several years in studies using otolith morphology to discriminate temporary and possibly misleading signals from those that indicate persistent spatial structure in stocks. We conclude that otolith morphology can be used as an initial step to direct further research on groups of P. leopardus that have lived at least a part of their life in different environments.
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The population structure and abundance of the American lobster (Homarus americanus) stock in the Gulf of Maine are defined by data derived from a fishery-independent trawl survey program conducted by the National Marine Fisheries Service (NMFS). Few sampling stations in the survey area are located inshore, in particular along coastal Maine. According to statistics, however, more than two thirds of the lobster landings come from inshore waters within three miles off the coast of Maine. In order to include an inshore survey program, complementary to the NMFS survey, the Maine Department of Marine Resources (DMR) initialized an inshore survey program in 2000. The survey was modeled on the NMFS survey program, making these two survey programs comparable. Using data from both survey programs, we evaluated the population structure of the American lobster in the Gulf of Maine. Our findings indicate that lobsters in the Gulf of Maine tend to have a size-dependent inshore-off-shore distribution; smaller lobsters are more likely to stay inshore and larger lobsters are more likely to stay offshore. The DMR inshore and NMFS survey programs focused on different areas in the Gulf of Maine and likely targeted different segments of the stock. We suggest that data from both survey programs be used to assess the lobster stock and to describe the dynamics of the stock in the Gulf of Maine.
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Summer flounder, Paralichthys dentatus, are managed as a single stock along the Atlantic coast from the U.S.– Canada border to the southern border of North Carolina. Justification of the single-stock approach is based on lack of genetic evidence for multiple stocks and the difficulty presented by managing the species from Cape Hatteras to the U.S.–Canada border. In this review, we present an interpretation of various morphometric, meristic, biochemical, and tagging studies, published and unpublished, that indicate the presence of two, or possibly three, distinct stocks in the management area. In addition, we have included new data from a tagging study that was conducted on juveniles from Virginia that aids in defining the stock(s) north of Cape Hatteras. Summer flounder, overfished for the past two decades, is recovering, and reconsideration of proposed stock structure could have direct implications for management policy decisions.
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Stands of Scalesia pedunculata in the Galapagos Islands often develop as single-aged cohorts following episodes of mass death and regeneration. We updated earlier studies on a stand that had regenerated soon after the 1982–3 El Niño event. We quantified stem size distribution and dispersion pattern in a 0.56 ha plot near Los Gemelos on Santa Cruz Island. The plot was dominated (95% of basal area) by S. pedunculata. The stem size distribution showed the increased mean and variance for diameter (since 1987 and 1991) expected of an aging stand. Stems averaged smaller than in 1981, just before the last mass mortality episode. Large S. pedunculata stems were regularly dispersed while smaller stems were clumped and negatively associated with larger stems, implying that intraspecific competition may be important in structuring the stand. CDF Contribution Number 1008.
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This is the report on Habitats Directive, the Review of Consents Stage 1 and 2 by the Environment Agency of the South Pennine Moors cSAC/SPA. The Habitats Directive has the main aim to promote the maintenance of biodiversity by defining a common framework for the conservation of wild plants and animals and habitats of community interest. The Directive establishes a European ecological network known as "Natura 2000". The network comprises Special Areas of Conservation (SAC) and Special Protection Areas (SPA). In the section on Stage 1 or Screening Process of the Habitat Directive, it is identified the likely impacts upon the Rixton Clay Pits cSAC of a project, plan or activities, either alone or in combination with other projects, plans or activities, and considers whether these impacts are likely to be significant. In the section on Stage 2 or Appropiate Assessment of the Habitat Directive, it is considered the impact on the integrity of the Rixton Clay Pits cSAC of the projects, plans or activities, either alone or in combination with other projects, plans or activities, with respect to the site’s structure and function and its conservation objectives. Additionally, where these are adverse impacts, an assessment of the potential mitigation of those impacts. The criteria used in this report to identify relevant projects, plans or activities and their impacts are water quality discharge consents, waste management licences, abstraction licences, Integration Pollution Control (IPC) and Integrated Pollution Prevention Control (IPPC) permits. Proformas, hydrogeological and GIS maps are included in the review.
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Management agencies often use geopolitical boundaries as proxies for biological boundaries. In Hawaiian waters a single stock is recognized of common bottlenose dolphins, Tursiops truncatus, a species that is found both in open water and near-shore among the main Hawaiian Islands. To assess population structure, we photo-identified 336 distinctive individuals from the main Hawaiian Islands, from 2000 to 2006. Their generally shallow-water distribution, and numerous within-year and between-year resightings within island areas suggest that individuals are resident to the islands, rather than part of an offshore population moving through the area. Comparisons of identifications obtained from Kaua‘i/Ni‘ihau, O‘ahu, the “4-island area,” and the island of Hawai‘i showed no evidence of movements among these island groups, although movements from Kaua‘i to Ni‘ihau and among the “4-islands” were documented. A Bayesian analysis examining the probability of missing movements among island groups, given our sample sizes for different areas, indicates that interisland movement rates are less than 1% per year with 95% probability. Our results suggest the existence of multiple demographically independent populations of island-associated common bottlenose dolphins around the main Hawaiian islands.
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This poster presents information on the status and trends of coral reef ecosystems in St. Croix, US Virgin Islands (USVI). Data were collected by NOAA’s Center for Coastal Monitoring and Assessment Biogeography Branch (CCMA-BB) from 2001-2006 at 1,275 random locations in and around Buck Island Reef National Monument (BIRNM). The main objective was to quantify changes in fish species and assemblage diversity, abundance, biomass and size structure; to provide spatially explicit information on the distribution of key species or groups of species; and to compare community structure inside versus outside of BIRNM.
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Distribution of zooplankton along two transects at Karwar and Ratnagiri, west coast of India, was studied. The standing stock of zooplankton was relatively high in the neritic zone with the highest value [358 ml/100 m super(3)] in the area off Ratnagiri due to the aggregation of fish larvae and hydromedusae. Maximum zooplankton production in these areas was noticed with the low temperature and low dissolved oxygen during postmonsoon season. At Karwar the highest biomass [188 ml/100 m super(3)] was observed from the nearshore station due to swarms of the cladoceran Penilia avirostris and the pteropod Cresis acicula when the salinity was low. The fluctuations in numerical abundance and percentage composition of all the major planktonic groups are discussed. The fishery of these areas is compared with the zooplankton standing stock.
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Green tiger prawn, Penaeus sentisulcatus is one of the commercial species of Persian Gulf, which is distributed from north to Strait of I Iormoze. Concerning its role in fisheries economic, various research projects on stock assessment, biology and aquaculture has been conducted. This research is targeted the identification of various populations of green tiger prawn in northern waters of Persian Gulf. The area has been divided to five regions from north to south named; Bahrakan, Boushehr, Tangestan, Motaaf and Strait of Hormoz. In each region, numbers of sampling stations trawled, and live shrimp species carried in containers equipped with air pump, to coastal laboratories in Boushehr and Bandar Abbass Fisheries Research Centers. Biometeric, morphometeric and merestic measures for 45 factars done, and peices of muscles, eye and ovary tissues dissected, and stored in liquid nitrogen. Protein extraction, and polyacrylamid gel electrophoresis by SDS-PAGE technique for tissues samples conducted. Data of 45 morphometeric and merestic characteristics analyzed by principal component analysis (PCA), and clustering analysis methods. The results of analysis showed that, the populations of Bahrakan and Mota.af regions are differentiated, while population of Boushehr and Tangestan regions were mixed, and named as a single population. The analysis of electrophoretic data also confirmed this result, and showed a distinct population in Strait of Hormoz. Therefore, this research illustrated four distinct populations for P. semisulcatus in northern area of Persian Gulf, named Bahrakan (north of Boushehr), Boushehr and Tangesta.n (adjacent), Motaaf and it's south, and Strait of Hormoz. Study of morphometeric characteristics of carapace factors, genital organs, antenna and life cycle of samples of different regions resulting identification of a subspecies, which is named Penaeus seinisuleatus persicus.