Analysis of multivariate stochastic signals sampled by on-line particle analyzers: Application to the quantitative assessment of occupational exposure to NOAA in multisource industrial scenarios (MSIS)

In multisource industrial scenarios (MSIS) coexist NOAA generating activities with other productive sources of airborne particles, such as parallel processes of manufacturing or electrical and diesel machinery. A distinctive characteristic of MSIS is the spatially complex distribution of aerosol sources, as well as their potential differences in dynamics, due to the feasibility of multi-task configuration at a given time. Thus, the background signal is expected to challenge the aerosol analyzers at a probably wide range of concentrations and size distributions, depending of the multisource configuration at a given time. Monitoring and prediction by using statistical analysis of time series captured by on-line particle analyzers in industrial scenarios, have been proven to be feasible in predicting PNC evolution provided a given quality of net signals (difference between signal at source and background). However the analysis and modelling of non-consistent time series, influenced by low levels of SNR (Signal-Noise Ratio) could build a misleading basis for decision making. In this context, this work explores the use of stochastic models based on ARIMA methodology to monitor and predict exposure values (PNC). The study was carried out in a MSIS where an case study focused on the manufacture of perforated tablets of nano-TiO2 by cold pressing was performed

A post-tsunami assessment of coastal living resources of Langkawi Archipelago, Peninsular Malaysia

Rapid and detailed post-tsunami surveys carried out in the Langkawi archipelago in January 2005 showed that the coral reefs dOld_ID not suffer any significant structural damage. Nevertheless, there were signs of recent sediment resuspension at the sites studied. The diversity and abundance of coral reef fishes and invertebrates were low. However, this was not attributed to the tsunami effect but rather to the present environmental conditions. The extent of damage at the villages of Kubang Badak and Kuala Teriang may indicate that intact coastal ecosystems such as mangroves have the potential to protect lives and property during natural disasters.

Assessment of the fishing effort level in the shrimp fisheries of the central and southern Gulf of California

In view of the concern caused by the declining trend in the annual shrimp yield in the Central Gulf of California, an attempt was made to analyze the fishing effort level exerted upon the shrimp stocks of the blue (Farfantepenaeus stylirostris) and the brown shrimp (F. californiensis) from 1980 to 1991. For this purpose, both Schaefer and Fox production models were applied. The results from these analyses revealed an economic overexploitation condition, and suggested an imperative need to implement as a regulatory measure, the reduction of the catch per unit of effort level (CPUE) to keep the fishery within acceptable bioeconomic margins of a maximum sustainable yield (Ys). This can only be achieved through the adjustment of the fleet size from 481 vessels down to 250 or 275.

An approach to the assessment of the finfish fisheries of the Caribbean Community

This paper briefly outlines the implications of making a decision on the most appropriate alternative for carrying out stock assessments and the reasons for previous failures to conserve finfish stocks for sustainable use. The Mathews (1987) approach utilizing Age-Length Catch-Effort Keys (ALCEK) is briefly reviewed, and a suggested overall approach for the assessment of the finfish resources of the Caribbean community is outlined. With recent initiatives towards use of the precautionary approach and reference points, Carribean community countries are advised to revisit the question of the models to be utilized for the assessment of their fish stocks, paying due attention to the quantity, quality and applicability of data now being collected.

Assessment of Lutjanus vivanus and Lutjanus buccanella in the north Caribbean coast of Costa Rica

This paper presents results of stock assessment on two snapper species, Lutjanus vivanus and L. buccanella, in the north Caribbean coast of Costa Rica. Growth parameters, mortality rates, length-weight relationships, recruitment patterns and exploitation rates for the two species are given. Results indicate that the two species are subject to relatively low exploitation levels with E = 0.25 for L. vivanus and E = 0.39 for L. buccanella.

An assessment of scup (Stenotomus chrysops) and black sea bass (Centropristas striata) discards in the directed otter trawl fisheries in the Mid-Atlantic Bight

This study was undertaken to re-assess the level of scup (Stenotomus chrysops) discards by weight and to evaluate the effect of various codend mesh sizes on the level of scup discards in the winter-trawl scup fishery. Scup discards were high in directed scup tows regardless of codend mesh — typically one to five times the weight of landings. The weight of scup discards in the present study did not differ significantly from that recorded in scup-targeted tows in the NMFS observer database. Most discards were required as such by the 22.86 cm TL (total length) fish-size limit for catches. Mesh sizes ≤12.7 cm, including the current legal mesh size (11.43 cm) did not adequately filter out scup smaller than 22.86 cm. The median length of scup discards was about 19.83 cm TL. Lowering the legal size for scup from 22.86 to 19.83 cm TL would greatly reduce discard mortality. Scup discards were a small fraction (0.4%) of black sea bass (Centropristis striata) landings in blacksea-bass−targeted tows. The black sea bass fishery is currently regulated under the small-mesh fishery gearrestricted area plan in which fishing is prohibited in some areas to reduce scup mortality. Our study found no evidence to support the efficacy of this management approach. The expectations that discarding would increase disproportionately as the trip limit (limit [in kilograms] on catch for a species) was reached towards the end of the trip and that discards would increase when the trip limit was reduced from 4536 kg to 454 kg at the end of the directed fishing season were not supported. Trip limits did not significantly affect discard mortality.

Biological Characteristics and Fishery Assessment of Alaska Plaice, Pleuronectes quadrituberculatus, in the Eastern Bering Sea

Alaska plaice, Pleuronectes quadrituberculatus, is one of the major flatfishes in the eastern Bering Sea ecosystem and is most highly concentrated in the shallow continental shelf of the eastern Bering Sea. Annual commercial catches have ranged from less than 1,000 metric tons (t) in 1963 to 62,000 t in 1988. Alaska plaice is a relatively large flatfish averaging about 32 cm in length and 390 g in weight in commercial catches. They are distributed from nearshore waters to a depth of about 100 m in the eastern Bering Sea during summer, but move to deeper continental shelf waters in winter to escape sea ice and cold water temperatures. Being a long-lived species (>30 years), they have a relatively low natural mortality rate estimated at 0.20. Maturing at about age 7, Alaska plaice spawn from April through June on hard sandy substrates of the shelf region, primarily around the 100 m isobath. Prey items primarily include polychaetes and other marine worms. In comparison with other flatfish, Alaska plaice and rock sole, Pleuronectes bilineatus, have similar diets but different habitat preferences with separate areas of peak population density which may minimize interspecific competition. Yellowfin sole, Pleuronectes asper, while sharing similar habitat, differs from these two species because of the variety of prey items in its diet. Competition for food resources among the three species appears to be low. The resource has experienced light exploitation since 1963 and is currently in good condition. Based on the results of demersal trawl surveys and age-structured analyses, the exploitable biomass increased from 1971 through the mid-1980’s before decreasing to the 1997 level of 500,000 t. The recommended 1998 harvest level, Allowable Biological Catch, was calculated from the Baranov catch equation based on the FMSY harvest level and the projected 1997 biomass, resulting in a commercial harvest of 69,000 t, or about 16% of the estimated exploitable biomass.

An Assessment of Fishery Yields from the East China Sea Ecosystem

A first assessment ofimportant East China Sea fisheries was carried out using data from 1956 to 1993. Two different data sets were available: 1) catch and effort data taken from landings and boat registrations and 2) catch and effort data from skipper's logs taken at sea. The two sets provided similar trends in CPUE over the study period. Stocks of high value, low volume species have been fished heavily and now produce very low landings or have been depleted (e.g. small and large yellow croaker). Some high volume and low value species have also been heavily fished (e.g. green filefish) while others (e.g. hairtail) are still producing high landings. Surplus production models were fitted to seven stocks. All showed considerable fluctuations in landings around MSY. The green filefish stock had an estimated MSY of around 160,000 tlyr at an effort of 2,500,000 kw and was depleted by a combination of excessive effort (around 4,000,000 kw in 1993) and marked fluctuations in landings (up to 70,000 tlyr above or below MSY). A sustainable policyfor managing ECS fisheries should address the effects ofboth effort and environmental variation.

Assessment of the Distribution and Abundance of Coastal Sharks in the U.S. Gulf of Mexico and Eastern Seaboard, 1995 and 1996

During 1995 and 1996, the National Marine Fisheries Service (NMFS), conducted pilot studies to develop survey methodology and a sampling strategy for assessment of coastal shark populations in the Gulf of Mexico and western North Atlantic. Longline gear similar to that used in the commercial shark fishery was deployed at randomly selected stations within three depth strata per 60 nautical mile gridf rom Brownsville, Tex. to Cape Ann, Mass. The survey methodology and gear design used in these surveys proved effective for capturing many of the small and large coastal sharks regulated under the auspices of the 1993 Fisheries Management Plan (FMP) for Sharks oft he Atlantic Ocean. Shark catch rates, species composition, and relative abundance documented in these pilot surveys were similar to those reported from observer programs monitoring commercial activities. During 78 survey days, 269 bottom longline sets were completed with 879 sharks captured.

Survey Assessment of Semi-pelagic Gadoids: The Example of Walleye Pollock, Theragra chalcogramma, in the Eastern Bering Sea

Assessment of walleye pollock, Theragra chalcogramma, in the eastern Bering Sea is complicated because the species is semi-pelagic in habit. Annual bottom trawl surveys provide estimates of demersal abundance on the eastern Bering Sea shelf. Every third year (starting in 1979), an extended area of the shelf and slope is surveyed and an echo integration-midwater trawl survey provides estimates of pollock abundance in midwater. Overall age-specific population and biomass estimates are obtained by summing the demersal and midwater results, assuming that the bottom trawl samples only pollock inhabiting the lower 3 m of the water column. Total population estimates have ranged from 134 x 109 fish in 1979 to 27 x 109 fish in 1988. The very high abundance observed in 1979 reflects the appearance of the unusually large 1978 year class. Changes in age-specific abundance estimates have documented the passage of strong (1978, 1982, and 1984) and weak year classes through the fishery. In general, older fish are more demersally oriented and younger fish are more abundant in midwater, but this trend was not always evident in the patterns of abundance of 1- and 2-year-old fish. As the average age of the population has increased, so has the relative proportion of pollock estimated by the demersal surveys. Consequently, it is unlikely that either technique can be used independently to monitor changes in abundance and age composition. Midwater assessment depends on pelagic trawl samples for size and age composition estimates, so both surveys are subject to biases resulting from gear performance and interactions between fish and gear. In this review, we discuss survey methodology and evaluate assumptions regarding catchability and availability as they relate to demersal, midwater, and overall assessment.