Introducci��n de peces ex��ticos en la Rep��blica Argentina

A review and analysis of the exotic fish distribution and introduction is made using bibliographic information. Both lentic and lotic environments were considered. In order to classify the state of the populations, different categories were defined as follow: permanent, probably permanent, reported and unknown. Results show that 15 species were attempted to be introduced from 1904. Only 8 of them arose an successfull aclimatization: raimbow trout, brown trout, lake trout, landlocked salmon, carp, goldfish, and mosquitofish. For the salmonids, ecological features were analized, in order to explain the disappearence or the permanence in some regions. (Document contains 90 pages)

The Annual Economic Survey of Federal Gulf Shrimp Permit Holders: Report on the Design, Implementation, and Descriptive Results for 2006

This technical memorandum documents the design, implementation, data preparation, and descriptive results for the 2006 Annual Economic Survey of Federal Gulf Shrimp Permit Holders. The data collection was designed by the NOAA Fisheries Southeast Fisheries Science Center Social Science Research Group to track the financial and economic status and performance by vessels holding a federal moratorium permit for harvesting shrimp in the Gulf of Mexico. A two page, self-administered mail survey collected total annual costs broken out into seven categories and auxiliary economic data. In May 2007, 580 vessels were randomly selected, stratified by state, from a preliminary population of 1,709 vessels with federal permits to shrimp in offshore waters of the Gulf of Mexico. The survey was implemented during the rest of 2007. After many reminder and verification phone calls, 509 surveys were deemed complete, for an ineligibility-adjusted response rate of 90.7%. The linking of each individual vessel���s cost data to its revenue data from a different data collection was imperfect, and hence the final number of observations used in the analyses is 484. Based on various measures and tests of validity throughout the technical memorandum, the quality of the data is high. The results are presented in a standardized table format, linking vessel characteristics and operations to simple balance sheet, cash flow, and income statements. In the text, results are discussed for the total fleet, the Gulf shrimp fleet, the active Gulf shrimp fleet, and the inactive Gulf shrimp fleet. Additional results for shrimp vessels grouped by state, by vessel characteristics, by landings volume, and by ownership structure are available in the appendices. The general conclusion of this report is that the financial and economic situation is bleak for the average vessels in most of the categories that were evaluated. With few exceptions, cash flow for the average vessel is positive while the net revenue from operations and the ���profit��� are negative. With negative net revenue from operations, the economic return for average shrimp vessels is less than zero. Only with the help of government payments does the average owner just about break even. In the short-term, this will discourage any new investments in the industry. The financial situation in 2006, especially if it endures over multiple years, also is economically unsustainable for the average established business. Vessels in the active and inactive Gulf shrimp fleet are, on average, 69 feet long, weigh 105 gross tons, are powered by 505 hp motor(s), and are 23 years old. Three-quarters of the vessels have steel hulls and 59% use a freezer for refrigeration. The average market value of these vessels was $175,149 in 2006, about a hundred-thousand dollars less than the average original purchase price. The outstanding loans averaged $91,955, leading to an average owner equity of $83,194. Based on the sample, 85% of the federally permitted Gulf shrimp fleet was actively shrimping in 2006. Of these 386 active Gulf shrimp vessels, just under half (46%) were owner-operated. On average, these vessels burned 52,931 gallons of fuel, landed 101,268 pounds of shrimp, and received $2.47 per pound of shrimp. Non-shrimp landings added less than 1% to cash flow, indicating that the federal Gulf shrimp fishery is very specialized. The average total cash outflow was $243,415 of which $108,775 was due to fuel expenses alone. The expenses for hired crew and captains were on average $54,866 which indicates the importance of the industry as a source of wage income. The resulting average net cash flow is $16,225 but has a large standard deviation. For the population of active Gulf shrimp vessels we can state with 95% certainty that the average net cash flow was between $9,500 and $23,000 in 2006. The median net cash flow was $11,843. Based on the income statement for active Gulf shrimp vessels, the average fixed costs accounted for just under a quarter of operating expenses (23.1%), labor costs for just over a quarter (25.3%), and the non-labor variable costs for just over half (51.6%). The fuel costs alone accounted for 42.9% of total operating expenses in 2006. It should be noted that the labor cost category in the income statement includes both the actual cash payments to hired labor and an estimate of the opportunity cost of owner-operators��� time spent as captain. The average labor contribution (as captain) of an owner-operator is estimated at about $19,800. The average net revenue from operations is negative $7,429, and is statistically different and less than zero in spite of a large standard deviation. The economic return to Gulf shrimping is negative 4%. Including non-operating activities, foremost an average government payment of $13,662, leads to an average loss before taxes of $907 for the vessel owners. The confidence interval of this value straddles zero, so we cannot reject, with 95% certainty, that the population average is zero. The average inactive Gulf shrimp vessel is generally of a smaller scale than the average active vessel. Inactive vessels are physically smaller, are valued much lower, and are less dependent on loans. Fixed costs account for nearly three quarters of the total operating expenses of $11,926, and only 6% of these vessels have hull insurance. With an average net cash flow of negative $7,537, the inactive Gulf shrimp fleet has a major liquidity problem. On average, net revenue from operations is negative $11,396, which amounts to a negative 15% economic return, and owners lose $9,381 on their vessels before taxes. To sustain such losses and especially to survive the negative cash flow, many of the owners must be subsidizing their shrimp vessels with the help of other income or wealth sources or are drawing down their equity. Active Gulf shrimp vessels in all states but Texas exhibited negative returns. The Alabama and Mississippi fleets have the highest assets (vessel values), on average, yet they generate zero cash flow and negative $32,224 net revenue from operations. Due to their high (loan) leverage ratio the negative 11% economic return is amplified into a negative 21% return on equity. In contrast, for Texas vessels, which actually have the highest leverage ratio among the states, a 1% economic return is amplified into a 13% return on equity. From a financial perspective, the average Florida and Louisiana vessels conform roughly to the overall average of the active Gulf shrimp fleet. It should be noted that these results are averages and hence hide the variation that clearly exists within all fleets and all categories. Although the financial situation for the average vessel is bleak, some vessels are profitable. (PDF contains 101 pages)

Support for Integrated Ecosystem Assessments of NOAA���s National Estuarine Research Reserves System (NERRS), Volume II: Assessment of Ecological Condition and Stressor Impacts in Subtidal Waters of the North Carolina NERRS

A study was conducted to assess the status of ecological condition and potential human-health risks in subtidal estuarine waters throughout the North Carolina National Estuarine Research Reserve System (NERRS) (Currituck Sound, Rachel Carson, Masonboro Island, and Zeke���s Island). Field work was conducted in September 2006 and incorporated multiple indicators of ecosystem condition including measures of water quality (dissolved oxygen, salinity, temperature, pH, nutrients and chlorophyll, suspended solids), sediment quality (granulometry, organic matter content, chemical contaminant concentrations), biological condition (diversity and abundances of benthic fauna, fish contaminant levels and pathologies), and human dimensions (fish-tissue contaminant levels relative to human-health consumption limits, various aesthetic properties). A probabilistic sampling design permitted statistical estimation of the spatial extent of degraded versus non-degraded condition across these estuaries relative to specified threshold levels of the various indicators (where possible). With some exceptions, the status of these reserves appeared to be in relatively good to fair ecological condition overall, with the majority of the area (about 54%) having various water quality, sediment quality, and biological (benthic) condition indicators rated in the healthy to intermediate range of corresponding guideline thresholds. Only three stations, representing 10.5% of the area, had one or more of these indicators rated as poor/degraded in all three categories. While such a conclusion is encouraging from a coastal management perspective, it should be viewed with some caution. For example, although co-occurrences of adverse biological and abiotic environmental conditions were limited, at least one indicator of ecological condition rated in the poor/degraded range was observed over a broader area (35.5%) represented by 11 of the 30 stations sampled. In addition, the fish-tissue contaminant data were not included in these overall spatial estimates; however, the majority of samples (77% of fish that were analyzed, from 79%, of stations where fish were caught) contained inorganic arsenic above the consumption limits for human cancer risks, though most likely derived from natural sources. Similarly, aesthetic indicators are not reflected in these spatial estimates of ecological condition, though there was evidence of noxious odors in sediments at many of the stations. Such symptoms reflect a growing realization that North Carolina estuaries are under multiple pressures from a variety of natural and human influences. These data also suggest that, while the current status of overall ecological condition appears to be good to fair, long-term monitoring is warranted to track potential changes in the future. This study establishes an important baseline of overall ecological condition within NC NERRS that can be used to evaluate any such future changes and to trigger appropriate management actions in this rapidly evolving coastal environment. (PDF contains 76 pages)

Characterization of the benthos, marine debris and bottom fish at Gray���s Reef National Marine Sanctuary

Executive Summary: Baseline characterization of resources is an essential part of marine protected area (MPA) management and is critical to inform adaptive management. Gray���s Reef National Marine Sanctuary (GRNMS) currently lacks adequate characterization of several key resources as identified in the 2006 Final Management Plan. The objectives of this characterization were to fulfill this need by characterizing the bottom fish, benthic features, marine debris, and the relationships among them for the different bottom types within the sanctuary: ledges, sparse live bottom, rippled sand, and flat sand. Particular attention was given to characterizing the different ledge types, their fish communities, and the marine debris associated with them given the importance of this bottom type to the sanctuary. The characterization has been divided into four sections. Section 1 provides a brief overview of the project, its relevance to sanctuary needs, methods of site selection, and general field procedures. Section 2 provides the survey methods, results, discussion, and recommendations for monitoring specific to the benthic characterization. Section 3 describes the characterization of marine debris. Section 4 is specific to the characterization of bottom fish. Field surveys were conducted during August 2004, May 2005, and August 2005. A total of 179 surveys were completed over ledge bottom (n=92), sparse live bottom (n=51), flat sand (n=20), and rippled sand (n=16). There were three components to each field survey: fish counting, benthic assessment, and quantification of marine debris. All components occurred within a 25 x 4 m belt transect. Two divers performed the transect at each survey site. One diver was responsible for identification of fish species, size, and abundance using a visual survey. The second diver was responsible for characterization of benthic features using five randomly placed 1 m2 quadrats, measuring ledge height and other benthic structures, and quantifying marine debris within the entire transect. GRNMS is composed of four main bottom types: flat sand, rippled sand, sparsely colonized live bottom, and densely colonized live bottom (ledges). Independent evaluation of the thematic accuracy of the GRNMS benthic map produced by Kendall et al. (2005) revealed high overall accuracy (93%). Most discrepancies between map and diver classification occurred during August 2004 and likely can be attributed to several factors, including actual map or diver errors, and changes in the bottom type due to physical forces. The four bottom types have distinct physical and biological characteristics. Flat and rippled sand bottom types were composed primarily of sand substrate and secondarily shell rubble. Flat sand and rippled sand bottom types were characterized by low percent cover (0-2%) of benthic organisms at all sites. Although the sand bottom types were largely devoid of epifauna, numerous burrows indicate the presence of infaunal organisms. Sparse live bottom and ledges were colonized by macroalgae and numerous invertebrates, including coral, gorgonians, sponges, and ���other��� benthic species (such as tunicates, anemones, and bryozoans). Ledges and sparse live bottom were similar in terms of diversity (H���) given the level of classification used here. However, percent cover of benthic species, with the exception of gorgonians, was significantly greater on ledge than on sparse live bottom. Percent biotic cover at sparse live bottom ranged from 0.7-26.3%, but was greater than 10% at only 7 out of 51 sites. Colonization on sparse live bottom is likely inhibited by shifting sands, as most sites were covered in a layer of sediment up to several centimeters thick. On ledge bottom type, percent cover ranged from 0.42-100%, with the highest percent cover at ledges in the central and south-central region of GRNMS. Biotic cover on ledges is influenced by local ledge characteristics. Cluster analysis of ledge dimensions (total height, undercut height, undercut width) resulted in three main categories of ledges, which were classified as short, medium, and tall. Median total percent cover was 97.6%, 75.1%, and 17.7% on tall, medium, and short ledges, respectively. Total percent cover and cover of macroalgae, sponges, and other organisms was significantly lower on short ledges compared to medium and tall ledges, but did not vary significantly between medium and tall ledges. Like sparse live bottom, short ledges may be susceptible to burial by sand, however the results indicate that ledge height may only be important to a certain threshold. There are likely other factors not considered here that also influence spatial distribution and community structure (e.g., small scale complexity, ocean currents, differential settlement patterns, and biological interactions). GRNMS is a popular site for recreational fishing and boating, and there has been increased concern about the accumulation of debris in the sanctuary and potential effects on sanctuary resources. Understanding the types, abundance, and distribution of debris is essential to improving debris removal and education efforts. Approximately two-thirds of all observed debris items found during the field surveys were fishing gear, and about half of the fishing related debris was monofilament fishing line. Other fishing related debris included leaders and spear gun parts, and non-gear debris included cans, bottles, and rope. The spatial distribution of debris was concentrated in the center of the sanctuary and was most frequently associated with ledges rather than at other bottom types. Several factors may contribute to this observation. Ledges are often targeted by fishermen due to the association of recreationally important fish species with this bottom type. In addition, ledges are structurally complex and are often densely colonized by biota, providing numerous places for debris to become stuck or entangled. Analysis of observed boat locations indicated that higher boat activity, which is an indication of fishing, occurs in the center of the sanctuary. On ledges, the presence and abundance of debris was significantly related to observed boat density and physiographic features including ledge height, ledge area, and percent cover. While it is likely that most fishing related debris originates from boats inside the sanctuary, preliminary investigation of ocean current data indicate that currents may influence the distribution and local retention of more mobile items. Fish communities at GRNMS are closely linked to benthic habitats. A list of species encountered, probability of occurrence, abundance, and biomass by habitat is provided. Species richness, diversity, composition, abundance, and biomass of fish all showed striking differences depending on bottom type with ledges showing the highest values of nearly all metrics. Species membership was distinctly separated by bottom type as well, although very short, sparsely colonized ledges often had a similar community composition to that of sparse live bottom. Analysis of fish communities at ledges alone indicated that species richness and total abundance of fish were positively related to total percent cover of sessile invertebrates and ledge height. Either ledge attribute was sufficient to result in high abundance or species richness of fish. Fish diversity (H`) was negatively correlated with undercut height due to schools of fish species that utilize ledge undercuts such as Pareques species. Concurrent analysis of ledge types and fish communities indicated that there are five distinct combinations of ledge type and species assemblage. These include, 1) short ledges with little or no undercut that lacked many of the undercut associated species except Urophycis earlii ; 2) tall, heavily colonized, deeply undercut ledges typically with Archosargus probatocephalus, Mycteroperca sp., and Pareques sp.; 3) tall, heavily colonized but less undercut with high occurrence of Lagodon rhomboides and Balistes capriscus; 4) short, heavily colonized ledges typically with Centropristis ocyurus, Halichoeres caudalis, and Stenotomus sp.; and 5) tall, heavily colonized, less undercut typically with Archosargus probatocephalus, Caranx crysos and Seriola sp.. Higher levels of boating activity and presumably fishing pressure did not appear to influence species composition or abundance at the community level although individual species appeared affected. These results indicate that merely knowing the basic characteristics of a ledge such as total height, undercut width, and percent cover of sessile invertebrates would allow good prediction of not only species richness and abundance of fish but also which particular fish species assemblages are likely to occur there. Comparisons with prior studies indicate some major changes in the fish community at GRNMS over the last two decades although the causes of the changes are unknown. Species of interest to recreational fishermen including Centropristis striata, Mycteroperca microlepis, and Mycteroperca phenax were examined in relation to bottom features, areas of assumed high versus low fishing pressure, and spatial dispersion. Both Mycteroperca species were found more frequently when undercut height of ledges was taller. They often were found together in small mixed species groups at ledges in the north central and southwest central regions of the sanctuary. Both had lower mode size and proportion of fish above the fishery size limit in heavily fished areas of the sanctuary (i.e. high boat density) despite the presence of better habitat in that region. Black sea bass, C. striata, occurred at 98% of the ledges surveyed and appeared to be evenly distributed throughout the sanctuary. Abundance was best explained by a positive relationship with percent cover of sessile biota but was also negatively related to presence of either Mycteroperca species. This may be due to predation by the Mycteroperca species or avoidance of sites where they are present by C. striata. Suggestions for monitoring bottom features, marine debris, and bottom fish at GRNMS are provided at the end of each chapter. The present assessment has established quantitative baseline characteristics of many of the key resources and use issues at GRNMS. The methods can be used as a model for future assessments to track the trajectory of GRNMS resources. Belt transects are ideally suited to providing efficient and quantitative assessment of bottom features, debris, and fish at GRNMS. The limited visibility, sensitivity of sessile biota, and linear nature of ledge habitats greatly diminish the utility of other sampling techniques. Ledges should receive the bulk of future characterization effort due to their importance to the sanctuary and high variability in physical structure, benthic composition, and fish assemblages. (PDF contains 107 pages.)

The ecological basis of fishery yield of the Puerto Rico-Virgin Islands Insular Shelf: 1987 Assessment

A literature review was conducted to locate information on the flow of energy from primary producers to the fishery stocks of the Puerto Rican-Virgin Islands insular shelf. This report uses site-specific information to describe the major ecological subsystems, or habitats, of the region, to identify the more common species and the subsystems in which they occur, to quantify productivity and biomass, and to outline trophic relationships. Discussions on each topic and subsystem vary in substance and detail, being limited by the availability and accessibility of information. (PDF contains 189 pages) Seven distinct subsystems are described: mangrove estuary, seagrass bed, coral reef, algal plain, sand/mud bottom, shelf break, and overlying pelagic. Over 50 tables provide lists of species found in each habitat on various surveys dating back to 1956. Estimates of density, relative abundance, and productivity are provided when possible. We evaluated whether sufficient information exists to support an analysis of the energy basis of fishery production in the area, beginning with the design and development of an ecosystem model. Data needs in three categories - species lists, biomass, and trophic relations - were examined for each subsystem and for each of three species groups - primary producers, invertebrates, and fish. We concluded that adequate data, sufficient for modeling purposes, are available in 16 (25%) of 64 categories; limited data, those requiring greater extrapolation, are available in 35 (55%) categories; and no data are available in 13 (20%) categories. The best-studied subsystems are seagrass beds and coral reefs, with at least limited data in all categories. Invertebrates, the intermediate link in the food web between primary producers and fishes, are the least quantified group in the region. Primary production and fishes, however, are relatively well-studied, providing sufficient data to support an ecosystem-level analysis and to initiate a modeling effort.

The State of Coral Reef Ecosystems of the United States and Pacific Freely Associated States: 2005

Executive Summary: For over three decades, scientists have been documenting the decline of coral reef ecosystems, amid increasing recognition of their value in supporting high biological diversity and their many benefits to human society. Coral reef ecosystems are recognized for their benefits on many levels, such as supporting economies by nurturing fisheries and providing for recreational and tourism opportunities, providing substances useful for medical purposes, performing essential ecosystem services that protect against coastal erosion, and provid-ing a diversity of other, more intangible contributions to many cultures. In the past decade, the increased awareness regarding coral reefs has prompted action by governmental and non-governmental organizations, including increased funding from the U.S. Congress for conservation of these important ecosystems and creation of the U.S. Coral Reef Task Force (USCRTF) to coordinate activities and implement conservation measures [Presidential Executive Order 13089]. Numerous partnerships forged among Federal agencies and state, local, non-governmental, academic and private partners support activities that range from basic science to systematic monitoring of ecosystem com-ponents and are conducted by government agencies, non-governmental organizations, universities, and the private sector. This report shares the results of many of these efforts in the framework of a broad assessment of the condition of coral reef ecosystems across 14 U.S. jurisdictions and Pacific Freely Associated States. This report relies heavily on quantitative, spatially-explicit data that has been collected in the recent past and comparisons with historical data, where possible. The success of this effort can be attributed to the dedication of over 160 report contributors who comprised the expert writing teams for each jurisdiction. The content of the report chapters are the result of their considerable collaborative efforts. The writing teams, which were organized by jurisdiction and comprised of experts from numerous research and management institutions, were provided a basic chapter outline and a length limit, but the content of each chapter was left entirely to their discretion. Each jurisdictional chapter in the report is structured to: 1) describe how each of the primary threats identified in the National Coral Reef Action Strategy (NCRAS) has manifested in the jurisdiction; 2) introduce ongoing monitoring and assessment activities relative to three major categories of inquiry ��� water quality, benthic habitats, and associated biological communities ��� and provide summary results in a data-rich format; and 3) highlight recent management activities that promote conservation of coral reef ecosystems.

Description of economic data collected with a random sample of commercial reef fish boats in the Florida Keys

This study summarizes the results of a survey designed to provide economic information about the financial status of commercial reef fish boats with homeports in the Florida Keys. A survey questionnaire was administered in the summer and fall of 1994 by interviewers in face-to-face meetings with owners or operators of randomly selected boats. Fishermen were asked for background information about themselves and their boats, their capital investments in boats and equipment, and about their average catches, revenues, and costs per trip for their two most important kinds of fishing trips during 1993 for species in the reef fish fishery. Respondents were characterized with regard to their dependence on the reef fish fishery as a source of household income. Boats were described in terms of their physical and financial characteristics. Different kinds of fishing trips were identified by the species that generated the greatest revenue. Trips were grouped into the following categories: yellowtail snapper (Ocyurus chrysurus); mutton snapper (Lutjanus analis), black grouper (Mycteroperca bonaci), or red grouper (Epinephelus morio); gray snapper (Lutjanus griseus); deeper water groupers and tilefishes; greater amberjack (Seriola dumerili); spiny lobster (Panulirus argus); king mackerel (Scomberomorus cavalla); and dolphin (Coryphaena hippurus). Average catches, revenues, routine trip costs, and net operating revenues per boat per trip and per boat per year were estimated for each category of fishing trips. In addition to its descriptive value, data collected during this study will aid in future examinations of the economic effects of various regulations on commercial reef fish fishermen.(PDF file contains 48 pages.)

Stock Composition of Some Sockeye Salmon, Oncorhynchus nerka, Catches in Southeast Alaska, Based on Incidence of Allozyme Variants, Freshwater Ages, and a Brain-Tissue Parasite

The incidence of four discrete characters of individual sockeye salmon -two genetically inherited proteins (PGM-1*and PGM-2*), freshwater age at migration, and the presence of the brain-tissue parasite Myxobolus arcticus-in weekly samples from two Alaskan fisheries (Noyes Island in 1986 and Sumner Strait in 1987) were used to infer stock composition of the catches based on corresponding character samples from 73 Alaskan and Canadian stocks. Estimated contributions of 13 stock groups, formed on the basis of character similarity of their members, were roughly consistent with expectations from tagging experiments, knowledge of stock magnitudes, and similar assessments from scales. Imprecision of the estimated contributions by the 13 stock groups limited their practical value; but variability was much reduced for combined estimated contributions by two inclusive categories, namely stock groups whose members had either high or low brainparasite prevalence. Noyes Island catches consisted predominantly of unparasitized fish, most of which were probably of Canadian origin. The majority of Sumner Strait catches consisted of parasitized fish, whose freshwater origins may have been in Alaska or Canada. (PDF file contains 27 pages.)

The Distribution of Kemp's Ridley Sea Turtles (Lepidochelys kempi) Along the Texas Coast: An Atlas

Eight hundred sixty-five records of Kemp's ridley sea turtles (Lepidochelys kempi) reported from Texas between the late 1940's to April 1990 were compiled from six data bases and the literature, then plotted on a series of Texas maps. Four categories of Kemp's ridleys are identified throughout the atlas: head-started (turtles that are raised in captivity their first year of life), wild, historical (pre-1980), and nesters. Geographic, seasonal, and size distributions of the turtle categories are plotted by regions. Most Kemp's ridleys were reported from the northeast and central Texas coast. They were reported from both inshore (landward of barrier islands) and offshore (seaward of barrier islands). Scattered nestings occurred in the central to southern regions. Kemp's ridleys were found more often during the spring and summer. A total of 546 turtle records contained measurements; most were 20-59.9 cm curved carapace length and considered sub-adults. Comparison of distributions of head-started and wild Kemp's ridleys suggests head-started Kemp's ridleys inhabit the same areas as wild Kemp's ridleys. (PDF file contains 56 pages.)

A Revised bibliography of papers dealing with the Oyster Toadfish, Opanus tau

The 261 papers of this bibliography fall into six major categories. These are alphabetized by author, within each subject, and are presented in the format usually encountered in the physiological and anatomical literature. We solicit your comments regarding omissions, errors or deletions. (PDF contains 19 pages)

Einfluss der Umsetzung der ICES-Fangempfehlungen auf den Zustand der Fischbest

The implementation of the precautionary approach in the mid-1990s required commercial fish stocks to be classified into different categories. These are based on the degree to which stocks have been exploited or are threatened by fishing activities. According to current ICES terminology, stocks are classified as being either ���within��� or ���outside safe biological limits���, or as being ���harvested outside safe biological limits���. Between 1996 and 2002, the relative share of stocks in these three categories remained relatively stable (at about 20 %, 30 % and 15 %, respectively). Over the same time span, the number of stocks were insufficient data is available to quantify and thus to appropriately classify the state of the spawning stock biomass (���status unknown���) has increased. Neglecting potential impacts of fishing pressure, the combined average proportion of all stocks with sufficiently high spawning stock biomass is at about one third, while only one fifth of the stocks assessed have been managed sustainably. For some important fish stocks in the ICES environment ��� specifically demersal ones ���, science recently had to call for rebuilding plans or even a closure of the fishery to allow recovery, in spite of the management���s agreement to manage the resources according to the precautionary approach. This obvious difference between approach and implementation has a number of potential causes: erroneous or imprecise input data (landings, discard and sampling information), insufficient assessment models, problems in the understanding of the scientific advice, and implementation errors. The latter could be either a difference between advised and implemented total allowable catches (TACs), or an excess of legal TACs. During the fifteen years covered by this analysis (1987 to 2002), the average deviation between the implemented TACs for a specific stock and that recommended by ICES for the same stock was more than 30 %. The overall average deviation (summed over all stocks) for the entire period was 34 %, excluding, however, four extreme outliers in the data, representing cases in which scientific recommendations were exceeded by as much as 1000 to 2500 %. If these were included, the overall average would be as high as 45 %. The annual deviation has substantially increased in recent years (from roughly 20 % in earlier years of the surveyed period). This recently observed high deviation also matches ICES���s estimate that the fishing mortality in the ICES convention area in the 1990s was well above recommended sustainable levels in the pelagic and demersal fishery. A direct comparison of scientifically proposed and politically implemented TACs is problematic in many case

A summary of the inventory survey of Nigeria inland waters and preliminary estimates of their fish yield potentials

A summary of the inventory survey of Nigeria inland waters is presented. The survey reveals that Kano State tops the list in reservoir development with an existing water surface area of about 42,773 ha, while Anambra State has the least with about 38 hectares. No reservoir was recorded for Lagos and Rivers States. However, in aspects of existing fish ponds, a total of about 471 ha was recorded for Plateau State and about 5 ha for Niger State. Preliminary estimates of Nigeria's fish yield potentials based on established production records of comparable water bodies in the tropics, at different levels of management, show that the available water mass in the country, estimated at about 12.5 million hectares, could yield a minimum of about 334,214 metric tonnes (m.t.) of fish per annum with little or no management and a maximum of about 511,703 metric tonnes per annum with adequate management. Comparison of the potential yields from inland sources with the projected fish production in Nigeria (1981-1985) based on supply and demand statistics shows that potential yield from inland sources even at a low level of management is relatively higher than the projected inland production and more than double the observed production. The variation between the potential and the observed fish yields in the country has been attributed to the absolute lack of management strategies for our various inland waters. The paper elaborates on possible management strategies for various categories of inland waters as a prelude towards increased fish production in the country

An evaluation of the artisanal fisheries resources of the Cross River State of Nigeria

The Cross River State (Nigeria) marine and freshwater artisanal capture fisheries are divided into 4 categories according to the type of resources being exploited. Schaefer's production model is applied to each of the fisheries to estimate the maximum sustainable yields (Ymax). The total potential yield for all the fisheries in natural waters is 178,650 tonnes/year. This potential is unlikely to be achieved as more fishermen are abandoning the occupation due to the scarcity of boats, outboard engines and nets. Even if the full potentials were realized the production would still be short of what the State should produce by about 30.5%. Investment opportunities which, if effected can help to narrow the gap between the available and the desired level of production are enumerated

Feeding ecology and population characteristics of Oreochromis niloticus (L.) and trophic interactions in the fish community of Nyanza Gulf, Lake Victoria, Kenya

Oreochromis niloticus (L.) were caught by beach seining, hook and line and trawling from Nyanza Gulf, lake Victoria (Kenya) in order to study their feeding ecology and population characteristics. Collected fish were weighed and TL measured immediately after capture. Fish were dissected and sexed. Stomach contents were removed and preserved in 4% buffered formalin for laboratory analysis. In the laboratory items were sorted into categories such as three quarters, half and quarter and awarded 20, 15 and 5 points respectively. Main food items for O. niloticus from November 1998 to March 1999 were insects, algae, fish and plant material. Increase in insects in the diet of O. niloticus might be attributed to the lake infestation by water hyacinth which harbours different species of insects

Eliciting and using stakeholder input to guide Puget Sound nearshore restoration decisionmaking

The goal of the Puget Sound Nearshore Ecosystem Restoration Project (PSNERP) is to improve system-wide functionality of nearshorei ecosystem processes. To achieve that goal, PSNERP plans to strategically restore nearshore sites throughout Puget Sound. PSNERP scientists are assessing changes to the nearshore, and will recommend an environmentally strategic restoration portfolio. Yet, PSNERP also needs stakeholder input to design a socially strategic portfolio. This research investigates the values and preferences of stakeholders in the Whidbey Sub-Basin of Puget Sound to help PSNERP be both socially and environmentally strategic. This investigation may be repeated in the six other Puget Sound Sub-Basins. The results will guide restoration portfolio design and future stakeholder involvement activities. This study examines four areas of stakeholder values and preferences: 1) beliefs about the causes, solutions, and severity of nearshore problems; 2) priorities for nearshore features, shoreforms, developments, and restoration objectives; 3) thoughts about ecosystem servicesiii and trade-offs among them; and 4) visions of a future, restored Puget Sound nearshore and the role of science in attaining this vision. The study is framed by two hypotheses from the Advocacy Coalition Framework (ACF), which suggests that groups of policy advocates form around shared ���policy core beliefs��� which can transcend traditional categories of stakeholders.(PDF contains 3 pages)