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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

On the development of decision-making systems based on fuzzy models to assess water quality in rivers

Ocampo Duque, William Andrés 17 April 2008 (has links)
There are many situations where a linguistic description of complex phenomena allows better assessments. It is well known that the assessment of water quality continues depending heavily upon subjective judgments and interpretation, despite the huge datasets available nowadays. In that sense, the aim of this study has been to introduce intelligent linguistic operations to analyze databases, and produce self interpretable water quality indicators, which tolerate both imprecision and linguistic uncertainty. Such imprecision typically reflects the ambiguity of human thinking when perceptions need to be expressed. Environmental management concepts such as: "water quality", "level of risk", or "ecological status" are ideally dealt with linguistic variables. In the present Thesis, the flexibility of computing with words offered by fuzzy logic has been considered in these management issues. Firstly, a multipurpose hierarchical water quality index has been designed with fuzzy reasoning. It integrates a wide set of indicators including: organic pollution, nutrients, pathogens, physicochemical macro-variables, and priority micro-contaminants. Likewise, the relative importance of the water quality indicators has been dealt with the analytic hierarchy process, a decision-aiding method. Secondly, a methodology based on a hybrid approach that combines fuzzy inference systems and artificial neural networks has been used to classify ecological status in surface waters according to the Water Framework Directive. This methodology has allowed dealing efficiently with the non-linearity and subjective nature of variables involved in this classification problem. The complexity of inference systems, the appropriate choice of linguistic rules, and the influence of the functions that transform numerical variables into linguistic variables have been studied. Thirdly, a concurrent neuro-fuzzy model based on screening ecological risk assessment has been developed. It has considered the presence of hazardous substances in rivers, and incorporates an innovative ranking and scoring system, based on a self-organizing map, to account for the likely ecological hazards posed by the presence of chemical substances in freshwater ecosystems. Hazard factors are combined with environmental concentrations within fuzzy inference systems to compute ecological risk potentials under linguistic uncertainty. The estimation of ecological risk potentials allows identifying those substances requiring stricter controls and further rigorous risk assessment. Likewise, the aggregation of ecological risk potentials, by means of empirical cumulative distribution functions, has allowed estimating changes in water quality over time. The neuro-fuzzy approach has been validated by comparison with biological monitoring. Finally, a hierarchical fuzzy inference system to deal with sediment based ecological risk assessment has been designed. The study was centered in sediments, since they produce complementary findings to water quality analysis, especially when temporal trends are required. Results from chemical and eco-toxicological analyses have been used as inputs to two parallel inference systems which assess levels of contamination and toxicity, respectively. Results from both inference engines are then treated in a third inference engine which provides a final risk characterization, where the risk is provided in linguistic terms, with their respective degrees of certitude. Inputs to the risk system have been the levels of potentially toxic substances, mainly metals and chlorinated organic compounds, and the toxicity measured with a screening test which uses the photo-luminescent bacteria Vibrio fischeri. The Ebro river basin has been selected as case study, although the methodologies here explained can easily be applied to other rivers. In conclusion, this study has broadly demonstrated that the design of water quality indexes, based on fuzzy logic, emerges as suitable and alternative tool to support decision makers involved in effective sustainable river basin management plans. / Existen diversas situaciones en las cuales la descripción en términos lingüísticos de fenómenos complejos permite mejores resultados. A pesar de los volúmenes de información cuantitativa que se manejan actualmente, es bien sabido que la gestión de la calidad del agua todavía obedece a juicios subjetivos y de interpretación de los expertos. Por tanto, el reto en este trabajo ha sido la introducción de operaciones lógicas que computen con palabras durante el análisis de los datos, para la elaboración de indicadores auto-interpretables de calidad del agua, que toleren la imprecisión e incertidumbre lingüística. Esta imprecisión típicamente refleja la ambigüedad del pensamiento humano para expresar percepciones. De allí que las variables lingüísticas se presenten como muy atractivas para el manejo de conceptos de la gestión medioambiental, como es el caso de la "calidad del agua", el "nivel de riesgo" o el "estado ecológico". Por tanto, en la presente Tesis, la flexibilidad de la lógica difusa para computar con palabras se ha adaptado a diversos tópicos en la gestión de la calidad del agua. Primero, se desarrolló un índice jerárquico multipropósito de calidad del agua que se obtuvo mediante razonamiento difuso. El índice integra un extenso grupo de indicadores que incluyen: contaminación orgánica, nutrientes, patógenos, variables macroscópicas, así como sustancias prioritarias micro-contaminantes. La importancia relativa de los indicadores al interior del sistema de inferencia se estimó con un método de análisis de decisiones, llamado proceso jerárquico analítico. En una segunda fase, se utilizó una metodología híbrida que combina los sistemas de inferencia difusos y las redes neuronales artificiales, conocida como neuro-fuzzy, para el estudio de la clasificación del estado ecológico de los ríos, de acuerdo con los lineamientos de la Directiva Marco de Aguas. Esta metodología permitió un manejo adecuado de la no-linealidad y naturaleza subjetiva de las variables involucradas en este problema clasificatorio. Con ella, se estudió la complejidad de los sistemas de inferencia, la selección apropiada de reglas lingüísticas y la influencia de las funciones que transforman las variables numéricas en lingüísticas. En una tercera fase, se desarrolló un modelo conceptual neuro-fuzzy concurrente basado en la metodología de evaluación de riesgo ecológico preliminar. Este modelo consideró la presencia de sustancias peligrosas en los ríos, e incorporó un mapa auto-organizativo para clasificar las sustancias químicas, en términos de su peligrosidad hacia los ecosistemas acuáticos. Con este modelo se estimaron potenciales de riesgo ecológico por combinación de factores de peligrosidad y de concentraciones de las sustancias químicas en el agua. Debido a la alta imprecisión e incertidumbre lingüística, estos potenciales se obtuvieron mediante sistemas de inferencia difusos, y se integraron por medio de distribuciones empíricas acumuladas, con las cuales se pueden analizar cambios espacio-temporales en la calidad del agua. Finalmente, se diseñó un sistema jerárquico de inferencia difuso para la evaluación del riesgo ecológico en sedimentos de ribera. Este sistema estima los grados de contaminación, toxicidad y riesgo en los sedimentos en términos lingüísticos, con sus respectivos niveles de certeza. El sistema se alimenta con información proveniente de análisis químicos, que detectan la presencia de sustancias micro-contaminantes, y de ensayos eco-toxicológicos tipo "screening" que usan la bacteria Vibrio fischeri. Como caso de estudio se seleccionó la cuenca del río Ebro, aunque las metodologías aquí desarrolladas pueden aplicarse fácilmente a otros ríos. En conclusión, este trabajo demuestra ampliamente que el diseño y aplicación de indicadores de calidad de las aguas, basados en la metodología de la lógica difusa, constituyen una herramienta sencilla y útil para los tomadores de decisiones encargados de la gestión sostenible de las cuencas hidrográficas.
22

Treatment of Endocrine Disrupting Chemicals (EDCs) by Constructed Wetlands

Zen, Yi-peng 15 July 2010 (has links)
Alkylphenol polyethoxylates (APEOs), a class of nonionic surfactants, have been widely used for industrial, agricultural and household applications. The biodegradation metabolites of APEOs, such as nonylphenol and octylphenol, are more persistent and known to disrupt endocrine function in wildlife and human. These compounds are also recognized as endocrine disrupting chemicals (EDCs). The objectives of this study were to investigate the distribution and removal efficiencies of EDCs, including nonylphenol diethoxylates (NP2EO), nonylphenol monoethoxylates (NP1EO), nonylphenol (NP) and octylphenol (OP), of wastewater treated by the constructed wetland systems along the Dahan River and around the Dapeng Bay, respectively. In addition, the method of risk quotient was used to evaluate the potential ecological risk of APEOs to aquatic organisms in current study. The water samples collected from 32 sampling sites in the Dapeng Bay National Scenic Area including Datan, Pengcun and Linbain right bank constructed wetlands. The samples were then concentrated by solid phase extraction, and analyzed for target compounds by HPLC/fluorescence. According to the results, nonylphenol diethoxylates, nonylphenol monoethoxylates, nonylphenol and octylphenol were found approximately equal to 29.9, 47.3, 20.5 and 57.7 %, respectively of the samples from three constructed wetlands with concentrations ranged from <3.3 to 968.7, <3.3 to 226.5, <1.3 to 238.4 and <1.0 to 1458.7 ng/L, respectively. Temporal variation of APEOs showed a decreasing in the order of summer¡Öspring¡Öwinter¡Öautumn. The removal efficiencies of APEOs in these constructed wetlands showed a decreasing order of Datan wetland¡ÖPengcun wetland¡ÖLinbain right bank wetland. In addition, the samples collected from 18 sampling sites from the constructed wetlands along the riparian of Dahan River including Daniaopi, Hsin-Hai Bridge Phases I and II constructed wetlands. According to the results, nonylphenol diethoxylates, nonylphenol monoethoxylates, nonylphenol and octylphenol were found approximately equal to 91.9¡B84.8¡B17.1 and 73.7 %, respectively of samples collected from three constructed wetlands with concentrations ranged from <3.3 to 11191.5, <3.3 to 6069.0, <1.3 to 671.0 and <1.0 to 5581.9 ng/L, respectively. The removal potential of APEOs in these constructed wetlands showed a decreasing order of Hsin-Hai Bridge Phases II¡ÖDaniaopi¡ÖHsin-Hai Bridge Phases I constructed wetland. Regarding the ecological assessment in this research, the calculated risk quotients were up to 30 times higher in the constructed wetland systems of Dahan River than those in the Dapeng Bay National Scenic Area, indicating that the existing concentrations of these EDCs in wetland systems might cause potential ecological risks to aquatic organisms. Furthermore, the decreasing risk quotient from influent to effluent indicating the capabilities of treating alkylphenolic compounds in these constructed wetlands.
23

Deriving critical tissue concentrations of trace metals in fishes for ecology risk assessment

Ching, C. Y., Terrance, 程振英 January 2007 (has links)
published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management
24

Deterministic vs probabilistic ecological risk assessment modeling at hazardous waste sites : a comparative case study

Sorenson, Mary T. 05 1900 (has links)
No description available.
25

Mass Balance Tracer Techniques for Integrating in situ Soil Ingestion Rates into Human and Ecological Risk Assessments

Doyle, James 12 January 2012 (has links)
Quantitative soil ingestion studies employing a mass balance tracer approach have been used to determine soil ingestion rate for use in human health risk assessments (HHRAs). Past studies have focused on soil ingestion in populations living in urban/suburban environments and the results have been highly variable. Moreover, there is a paucity of reliable quantitative soil ingestion data to support human health risk assessments of other lifestyles that may be predisposed to ingesting soil, such as indigenous populations following traditional lifestyles. Thus, the primary objective of the research was to determine if populations following lifestyles typical of traditional land use practices in rural or wilderness areas ingest more soil than populations living in urban or suburban environments. Further, the research investigated the use of alternative mass balance tracers, specifically isotopes of the 238U and 232Th decay series, to reduce soil ingestion estimate variability. Mass balance tracer methods were developed and validated in a pilot canine study, and methods using isotope tracers were adapted to permit quantification of sediment ingestion in the benthic fish Moxostoma macrolepidotum (Shorthead Redhorse Sucker). A pilot human soil ingestion study of 7 subjects from an Aboriginal community in British Columbia was conducted over a 3-week period. The mean soil ingestion rate calculated using the daily means of the 4 elemental tracers with the lowest food-to-soil ratios (i.e., Al, Ce, La, Si) was observed to be approximately 74 mg d-1 (standard deviation 91 mg d-1), The median soil ingestion rate was 60 mg d-1, and the 90th percentile was 196 mg d-1. These soil ingestion rate estimates are higher than those currently recommended for HHRAs of adults, and higher than those obtained in most previous studies of adults. However, the estimates are much lower than the earlier qualitative assessments for subsistence lifestyles (i.e., 330-400 mg d-1). The study results also demonstrated that isotopes of the 238U and 232Th decay series radionuclide are not reliable mass balance tracers for estimating soil ingestion in humans; however, they may be useful for quantifying soil and sediment ingestion in wildlife.
26

Chondrichthyans and the Queensland East Coast Trawl Fishery: Bycatch reduction, biology, conservation status and sustainability

Peter Kyne Unknown Date (has links)
The chondrichthyan (shark, batoid and holocephalan) bycatch of the Queensland East Coast Trawl Fishery (ECTF) was examined through a series of fishery-independent trawl surveys, together with fishery-dependent (opportunistic) sampling. Project aims were to document the chondrichthyan bycatch composition in order to test the effectiveness of turtle exclusion devices (TEDs) and bycatch reduction devices (BRDs), to examine biological aspects of bycatch species, and to combine data collected through these parts to assess the conservation status and sustainability of bycatch species. A total of 37 chondrichthyan species (one holocephalan, 19 batoids and 17 sharks) from 18 families were recorded in the bycatch of the fishery. The most speciose families recorded were the stingrays (Dasyatidae; 7 species), the requiem sharks (Carcharhinidae; 5 species), the catsharks (Scyliorhinidae; 4 species) and the stingarees (Urolophidae; 3 species). Chondrichthyan bycatch was highly variable between fishery sectors; catch rates were low in the tiger/Endeavour prawn sector (north Queensland; 0.02–0.12 individuals ha-1 trawled) and in the eastern king prawn (deepwater) sector (southern Queensland; 0.08 individuals ha-1 trawled), intermediate in Hervey Bay (southern Queensland; 0.25 individuals ha-1 trawled) and in the scallop sector (central Queensland coast; 0.31 individuals ha-1 trawled) and highest in the eastern king prawn (shallow water) sector (southern Queensland; 0.96 individuals ha-1 trawled). Chondrichthyan bycatch in the eastern king prawn (shallow water) sector was dominated by the three batoids Aptychotrema rostrata, Trygonoptera testacea and Urolophus kapalensis (~92% of the chondrichthyan bycatch by number), in the eastern king prawn (deepwater) sector by the skate Dipturus polyommata and the two catsharks Asymbolus rubiginosus and Figaro boardmani (~83% of the chondrichthyan bycatch by number), in the scallop sector by the three batoids A. rostrata, Neotrygon kuhlii and Neotrygon picta (~91% of the chondrichthyan bycatch by number), and in the tiger/Endeavour prawn sector by the two batoids Himantura astra and Gymnura australis and the two sharks Chiloscyllium punctatum and Hemigaleus australiensis (~67% of the chondrichthyan bycatch by number). The testing of TEDs and BRDs, which are mandatory throughout the fishery, demonstrated only a limited ability to reduce chondrichthyan bycatch in the ECTF, which is comprised mainly of relatively small species. The shorter trawl durations of the surveys compared with normal commercial activities may have under-represented larger species. No significant reductions in chondrichthyan bycatch were found using a TED and a radial escape section BRD in the eastern king prawn (shallow water) sector, using a TED and a square-mesh codend BRD in the eastern king prawn (deepwater) sector, or using a TED and a fisheye BRD in Hervey Bay. There was however, a significant difference in the probability of capturing the group ‘sharks and guitarfishes’ (comprised largely of A. rostrata) between codend types in the scallop sector, with the lowest probability of capture in nets fitted with both a TED and a square-mesh codend BRD (the difference was largely attributed to the effects of the TED). In the tiger/Endeavour prawn sector, in which three different BRDs were trialed (fisheye, square-mesh codend, square-mesh panel), the probability of capturing chondrichthyans was significantly lower in nets fitted with a fisheye BRD than in the standard (control) net, and the probability of capturing batoids was significantly lower in nets fitted with a fisheye BRD or with a square-mesh codend BRD than in the standard (control) net. The small sample size of chondrichthyan catches in some sectors may have reduced to power to detect bycatch reduction. The biology of several bycatch species from the families Rajidae, Rhinobatidae, Urolophidae and Scyliorhinidae was examined. For D. polyommata, size at birth was estimated at ~100–110 mm total length (LT), size at first feeding at ~105–110mm LT, size at 50% maturity (LT50 and 95% CI) at 321 (305–332) mm LT for females and 300 (285–306) mm LT for males. Diet (described by the index of relative importance as a percentage) was predominantly crustacean based, with carid shrimps (53.6%) and penaeoid prawns (23.3%) being the most significant prey groups. For A. rostrata, size at birth was estimated at <170 mm LT, size at 50% maturity (LT50 and 95% CI) at 640 (618–663) mm LT for females and 597 (551–649) mm LT for males, and litter size was 9–20 (n = 9; mean ± S.E. = 15.1 ± 1.2). For T. testacea, size at birth was estimated at 77–100 mm disc width (WD), size at 50% maturity (WD50 and 95% CI) at 163 (156–169) mm WD for females and 146 (140–150) mm WD for males, and litter size was always one (n = 6). For U. kapalensis, size at birth was estimated at 75–100 mm WD, size at 50% maturity (WD50 and 95% CI) at 154 (145–160) mm WD for females and 155 (149–159) mm WD for males, and litter size was always one (n = 16). The catsharks A. analis, A. rubiginosus and F. boardmani were all confirmed as single oviparous species (carrying only one egg case in each uterus at one time). Ovarian fecundity (the number of vitellogenic follicles) averaged 13.6 (range 13–20) in A. analis, 13.5 (range 5–23) in A. rubiginosus and 10.4 (range 9–13) in F. boardmani. While only limited data were available from southern Queensland, several indicators suggest that Asymbolus catsharks are reproductively active year-round. A general lack of small-sized or immature catsharks captured during the study made assessments of size at maturity difficult for these species. The conservation status of ECTF bycatch species was examined through the application of the IUCN Red List of Threatened SpeciesTM Categories and Criteria, which considers extinction risk at the global level. Of the 24 ECTF chondrichthyan bycatch species evaluated against the IUCN Red List Categories and Criteria, four have been assessed globally as Vulnerable (a threatened category indicating that a species is ‘facing a high risk of extinction in the wild’), seven as Near Threatened, 11 as Least Concern and two as Data Deficient. While the four globally threatened species (A. nichofii, Heteroscyllium colcloughi, Rhynchobatus australiae and Urolophus sufflavus) were only minor components of the ECTF bycatch, their global conservation status warrants that fisheries management and industry should act to ensure minimal impacts on these species. An ecological risk assessment method (Susceptibility-Recovery Analysis) was used to assess the relative sustainability or risk of individual species to the fishing activities of the ECTF. Two separate approaches were taken to the technique, which considers sustainability to be dependent on the susceptibility of a species to the fishery and the recovery potential of a species after depletion by fishing activities. The first approach applied the precautionary principal when data were lacking for the calculation of recovery attributes, while the second used biological data from similar species when species-specific data were lacking. The precautionary approach tended to overestimate risk to poorly known oviparous species. The biological approach suggested that A. nichofii, F. boardmani, Rhizoprionodon acutus, Rhizoprionodon taylori and Rhynchobatus palpebratus face the least risk (i.e. were the most sustainable) while several medium-large batoids and the sharks Loxodon macrorhinus and Heteroscyllium colcloughi were the species most at risk (i.e. least sustainable). Demonstrating ecological sustainability of the ECTF will need to be a continued management objective into the future. To further improve the ecological sustainability of the fishery in relation to sharks, batoids and holocephalans, a number of management recommendations are proposed: (1) give warranted conservation consideration to listed threatened species as well as species identified as being at risk; (2) expand required logbook information on chondrichthyan species to include recording of catches of these species; (3) encourage safe release practices for all chondrichthyans to maximise survivorship of discards; (4) initiate research into the survivorship of discards; (5) ensure long-term observer coverage on commercial vessels to monitor bycatch levels; and, (6) test and quantify reduced TED bar spacings (presently 120 mm) in fishery sectors which show the highest chondrichthyan bycatch levels, that is, the eastern king prawn (shallow water) and scallop sectors.
27

Chondrichthyans and the Queensland East Coast Trawl Fishery: Bycatch reduction, biology, conservation status and sustainability

Peter Kyne Unknown Date (has links)
The chondrichthyan (shark, batoid and holocephalan) bycatch of the Queensland East Coast Trawl Fishery (ECTF) was examined through a series of fishery-independent trawl surveys, together with fishery-dependent (opportunistic) sampling. Project aims were to document the chondrichthyan bycatch composition in order to test the effectiveness of turtle exclusion devices (TEDs) and bycatch reduction devices (BRDs), to examine biological aspects of bycatch species, and to combine data collected through these parts to assess the conservation status and sustainability of bycatch species. A total of 37 chondrichthyan species (one holocephalan, 19 batoids and 17 sharks) from 18 families were recorded in the bycatch of the fishery. The most speciose families recorded were the stingrays (Dasyatidae; 7 species), the requiem sharks (Carcharhinidae; 5 species), the catsharks (Scyliorhinidae; 4 species) and the stingarees (Urolophidae; 3 species). Chondrichthyan bycatch was highly variable between fishery sectors; catch rates were low in the tiger/Endeavour prawn sector (north Queensland; 0.02–0.12 individuals ha-1 trawled) and in the eastern king prawn (deepwater) sector (southern Queensland; 0.08 individuals ha-1 trawled), intermediate in Hervey Bay (southern Queensland; 0.25 individuals ha-1 trawled) and in the scallop sector (central Queensland coast; 0.31 individuals ha-1 trawled) and highest in the eastern king prawn (shallow water) sector (southern Queensland; 0.96 individuals ha-1 trawled). Chondrichthyan bycatch in the eastern king prawn (shallow water) sector was dominated by the three batoids Aptychotrema rostrata, Trygonoptera testacea and Urolophus kapalensis (~92% of the chondrichthyan bycatch by number), in the eastern king prawn (deepwater) sector by the skate Dipturus polyommata and the two catsharks Asymbolus rubiginosus and Figaro boardmani (~83% of the chondrichthyan bycatch by number), in the scallop sector by the three batoids A. rostrata, Neotrygon kuhlii and Neotrygon picta (~91% of the chondrichthyan bycatch by number), and in the tiger/Endeavour prawn sector by the two batoids Himantura astra and Gymnura australis and the two sharks Chiloscyllium punctatum and Hemigaleus australiensis (~67% of the chondrichthyan bycatch by number). The testing of TEDs and BRDs, which are mandatory throughout the fishery, demonstrated only a limited ability to reduce chondrichthyan bycatch in the ECTF, which is comprised mainly of relatively small species. The shorter trawl durations of the surveys compared with normal commercial activities may have under-represented larger species. No significant reductions in chondrichthyan bycatch were found using a TED and a radial escape section BRD in the eastern king prawn (shallow water) sector, using a TED and a square-mesh codend BRD in the eastern king prawn (deepwater) sector, or using a TED and a fisheye BRD in Hervey Bay. There was however, a significant difference in the probability of capturing the group ‘sharks and guitarfishes’ (comprised largely of A. rostrata) between codend types in the scallop sector, with the lowest probability of capture in nets fitted with both a TED and a square-mesh codend BRD (the difference was largely attributed to the effects of the TED). In the tiger/Endeavour prawn sector, in which three different BRDs were trialed (fisheye, square-mesh codend, square-mesh panel), the probability of capturing chondrichthyans was significantly lower in nets fitted with a fisheye BRD than in the standard (control) net, and the probability of capturing batoids was significantly lower in nets fitted with a fisheye BRD or with a square-mesh codend BRD than in the standard (control) net. The small sample size of chondrichthyan catches in some sectors may have reduced to power to detect bycatch reduction. The biology of several bycatch species from the families Rajidae, Rhinobatidae, Urolophidae and Scyliorhinidae was examined. For D. polyommata, size at birth was estimated at ~100–110 mm total length (LT), size at first feeding at ~105–110mm LT, size at 50% maturity (LT50 and 95% CI) at 321 (305–332) mm LT for females and 300 (285–306) mm LT for males. Diet (described by the index of relative importance as a percentage) was predominantly crustacean based, with carid shrimps (53.6%) and penaeoid prawns (23.3%) being the most significant prey groups. For A. rostrata, size at birth was estimated at <170 mm LT, size at 50% maturity (LT50 and 95% CI) at 640 (618–663) mm LT for females and 597 (551–649) mm LT for males, and litter size was 9–20 (n = 9; mean ± S.E. = 15.1 ± 1.2). For T. testacea, size at birth was estimated at 77–100 mm disc width (WD), size at 50% maturity (WD50 and 95% CI) at 163 (156–169) mm WD for females and 146 (140–150) mm WD for males, and litter size was always one (n = 6). For U. kapalensis, size at birth was estimated at 75–100 mm WD, size at 50% maturity (WD50 and 95% CI) at 154 (145–160) mm WD for females and 155 (149–159) mm WD for males, and litter size was always one (n = 16). The catsharks A. analis, A. rubiginosus and F. boardmani were all confirmed as single oviparous species (carrying only one egg case in each uterus at one time). Ovarian fecundity (the number of vitellogenic follicles) averaged 13.6 (range 13–20) in A. analis, 13.5 (range 5–23) in A. rubiginosus and 10.4 (range 9–13) in F. boardmani. While only limited data were available from southern Queensland, several indicators suggest that Asymbolus catsharks are reproductively active year-round. A general lack of small-sized or immature catsharks captured during the study made assessments of size at maturity difficult for these species. The conservation status of ECTF bycatch species was examined through the application of the IUCN Red List of Threatened SpeciesTM Categories and Criteria, which considers extinction risk at the global level. Of the 24 ECTF chondrichthyan bycatch species evaluated against the IUCN Red List Categories and Criteria, four have been assessed globally as Vulnerable (a threatened category indicating that a species is ‘facing a high risk of extinction in the wild’), seven as Near Threatened, 11 as Least Concern and two as Data Deficient. While the four globally threatened species (A. nichofii, Heteroscyllium colcloughi, Rhynchobatus australiae and Urolophus sufflavus) were only minor components of the ECTF bycatch, their global conservation status warrants that fisheries management and industry should act to ensure minimal impacts on these species. An ecological risk assessment method (Susceptibility-Recovery Analysis) was used to assess the relative sustainability or risk of individual species to the fishing activities of the ECTF. Two separate approaches were taken to the technique, which considers sustainability to be dependent on the susceptibility of a species to the fishery and the recovery potential of a species after depletion by fishing activities. The first approach applied the precautionary principal when data were lacking for the calculation of recovery attributes, while the second used biological data from similar species when species-specific data were lacking. The precautionary approach tended to overestimate risk to poorly known oviparous species. The biological approach suggested that A. nichofii, F. boardmani, Rhizoprionodon acutus, Rhizoprionodon taylori and Rhynchobatus palpebratus face the least risk (i.e. were the most sustainable) while several medium-large batoids and the sharks Loxodon macrorhinus and Heteroscyllium colcloughi were the species most at risk (i.e. least sustainable). Demonstrating ecological sustainability of the ECTF will need to be a continued management objective into the future. To further improve the ecological sustainability of the fishery in relation to sharks, batoids and holocephalans, a number of management recommendations are proposed: (1) give warranted conservation consideration to listed threatened species as well as species identified as being at risk; (2) expand required logbook information on chondrichthyan species to include recording of catches of these species; (3) encourage safe release practices for all chondrichthyans to maximise survivorship of discards; (4) initiate research into the survivorship of discards; (5) ensure long-term observer coverage on commercial vessels to monitor bycatch levels; and, (6) test and quantify reduced TED bar spacings (presently 120 mm) in fishery sectors which show the highest chondrichthyan bycatch levels, that is, the eastern king prawn (shallow water) and scallop sectors.
28

Chondrichthyans and the Queensland East Coast Trawl Fishery: Bycatch reduction, biology, conservation status and sustainability

Peter Kyne Unknown Date (has links)
The chondrichthyan (shark, batoid and holocephalan) bycatch of the Queensland East Coast Trawl Fishery (ECTF) was examined through a series of fishery-independent trawl surveys, together with fishery-dependent (opportunistic) sampling. Project aims were to document the chondrichthyan bycatch composition in order to test the effectiveness of turtle exclusion devices (TEDs) and bycatch reduction devices (BRDs), to examine biological aspects of bycatch species, and to combine data collected through these parts to assess the conservation status and sustainability of bycatch species. A total of 37 chondrichthyan species (one holocephalan, 19 batoids and 17 sharks) from 18 families were recorded in the bycatch of the fishery. The most speciose families recorded were the stingrays (Dasyatidae; 7 species), the requiem sharks (Carcharhinidae; 5 species), the catsharks (Scyliorhinidae; 4 species) and the stingarees (Urolophidae; 3 species). Chondrichthyan bycatch was highly variable between fishery sectors; catch rates were low in the tiger/Endeavour prawn sector (north Queensland; 0.02–0.12 individuals ha-1 trawled) and in the eastern king prawn (deepwater) sector (southern Queensland; 0.08 individuals ha-1 trawled), intermediate in Hervey Bay (southern Queensland; 0.25 individuals ha-1 trawled) and in the scallop sector (central Queensland coast; 0.31 individuals ha-1 trawled) and highest in the eastern king prawn (shallow water) sector (southern Queensland; 0.96 individuals ha-1 trawled). Chondrichthyan bycatch in the eastern king prawn (shallow water) sector was dominated by the three batoids Aptychotrema rostrata, Trygonoptera testacea and Urolophus kapalensis (~92% of the chondrichthyan bycatch by number), in the eastern king prawn (deepwater) sector by the skate Dipturus polyommata and the two catsharks Asymbolus rubiginosus and Figaro boardmani (~83% of the chondrichthyan bycatch by number), in the scallop sector by the three batoids A. rostrata, Neotrygon kuhlii and Neotrygon picta (~91% of the chondrichthyan bycatch by number), and in the tiger/Endeavour prawn sector by the two batoids Himantura astra and Gymnura australis and the two sharks Chiloscyllium punctatum and Hemigaleus australiensis (~67% of the chondrichthyan bycatch by number). The testing of TEDs and BRDs, which are mandatory throughout the fishery, demonstrated only a limited ability to reduce chondrichthyan bycatch in the ECTF, which is comprised mainly of relatively small species. The shorter trawl durations of the surveys compared with normal commercial activities may have under-represented larger species. No significant reductions in chondrichthyan bycatch were found using a TED and a radial escape section BRD in the eastern king prawn (shallow water) sector, using a TED and a square-mesh codend BRD in the eastern king prawn (deepwater) sector, or using a TED and a fisheye BRD in Hervey Bay. There was however, a significant difference in the probability of capturing the group ‘sharks and guitarfishes’ (comprised largely of A. rostrata) between codend types in the scallop sector, with the lowest probability of capture in nets fitted with both a TED and a square-mesh codend BRD (the difference was largely attributed to the effects of the TED). In the tiger/Endeavour prawn sector, in which three different BRDs were trialed (fisheye, square-mesh codend, square-mesh panel), the probability of capturing chondrichthyans was significantly lower in nets fitted with a fisheye BRD than in the standard (control) net, and the probability of capturing batoids was significantly lower in nets fitted with a fisheye BRD or with a square-mesh codend BRD than in the standard (control) net. The small sample size of chondrichthyan catches in some sectors may have reduced to power to detect bycatch reduction. The biology of several bycatch species from the families Rajidae, Rhinobatidae, Urolophidae and Scyliorhinidae was examined. For D. polyommata, size at birth was estimated at ~100–110 mm total length (LT), size at first feeding at ~105–110mm LT, size at 50% maturity (LT50 and 95% CI) at 321 (305–332) mm LT for females and 300 (285–306) mm LT for males. Diet (described by the index of relative importance as a percentage) was predominantly crustacean based, with carid shrimps (53.6%) and penaeoid prawns (23.3%) being the most significant prey groups. For A. rostrata, size at birth was estimated at <170 mm LT, size at 50% maturity (LT50 and 95% CI) at 640 (618–663) mm LT for females and 597 (551–649) mm LT for males, and litter size was 9–20 (n = 9; mean ± S.E. = 15.1 ± 1.2). For T. testacea, size at birth was estimated at 77–100 mm disc width (WD), size at 50% maturity (WD50 and 95% CI) at 163 (156–169) mm WD for females and 146 (140–150) mm WD for males, and litter size was always one (n = 6). For U. kapalensis, size at birth was estimated at 75–100 mm WD, size at 50% maturity (WD50 and 95% CI) at 154 (145–160) mm WD for females and 155 (149–159) mm WD for males, and litter size was always one (n = 16). The catsharks A. analis, A. rubiginosus and F. boardmani were all confirmed as single oviparous species (carrying only one egg case in each uterus at one time). Ovarian fecundity (the number of vitellogenic follicles) averaged 13.6 (range 13–20) in A. analis, 13.5 (range 5–23) in A. rubiginosus and 10.4 (range 9–13) in F. boardmani. While only limited data were available from southern Queensland, several indicators suggest that Asymbolus catsharks are reproductively active year-round. A general lack of small-sized or immature catsharks captured during the study made assessments of size at maturity difficult for these species. The conservation status of ECTF bycatch species was examined through the application of the IUCN Red List of Threatened SpeciesTM Categories and Criteria, which considers extinction risk at the global level. Of the 24 ECTF chondrichthyan bycatch species evaluated against the IUCN Red List Categories and Criteria, four have been assessed globally as Vulnerable (a threatened category indicating that a species is ‘facing a high risk of extinction in the wild’), seven as Near Threatened, 11 as Least Concern and two as Data Deficient. While the four globally threatened species (A. nichofii, Heteroscyllium colcloughi, Rhynchobatus australiae and Urolophus sufflavus) were only minor components of the ECTF bycatch, their global conservation status warrants that fisheries management and industry should act to ensure minimal impacts on these species. An ecological risk assessment method (Susceptibility-Recovery Analysis) was used to assess the relative sustainability or risk of individual species to the fishing activities of the ECTF. Two separate approaches were taken to the technique, which considers sustainability to be dependent on the susceptibility of a species to the fishery and the recovery potential of a species after depletion by fishing activities. The first approach applied the precautionary principal when data were lacking for the calculation of recovery attributes, while the second used biological data from similar species when species-specific data were lacking. The precautionary approach tended to overestimate risk to poorly known oviparous species. The biological approach suggested that A. nichofii, F. boardmani, Rhizoprionodon acutus, Rhizoprionodon taylori and Rhynchobatus palpebratus face the least risk (i.e. were the most sustainable) while several medium-large batoids and the sharks Loxodon macrorhinus and Heteroscyllium colcloughi were the species most at risk (i.e. least sustainable). Demonstrating ecological sustainability of the ECTF will need to be a continued management objective into the future. To further improve the ecological sustainability of the fishery in relation to sharks, batoids and holocephalans, a number of management recommendations are proposed: (1) give warranted conservation consideration to listed threatened species as well as species identified as being at risk; (2) expand required logbook information on chondrichthyan species to include recording of catches of these species; (3) encourage safe release practices for all chondrichthyans to maximise survivorship of discards; (4) initiate research into the survivorship of discards; (5) ensure long-term observer coverage on commercial vessels to monitor bycatch levels; and, (6) test and quantify reduced TED bar spacings (presently 120 mm) in fishery sectors which show the highest chondrichthyan bycatch levels, that is, the eastern king prawn (shallow water) and scallop sectors.
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An integrated approach to evaluating the environmental impact following a radiological dispersal event

Smith, David A., January 2006 (has links)
Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 169-183).
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The development and application of ecological risk assessment in South African water resource management /

Claassen, Marius. January 2003 (has links)
Thesis (Ph. D. (Zoology and Entomology))--Rhodes University, 2006.

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