M.Sc. / Please refer to full text to view abstract

The coefficient of body temperature change (K) ranged from -0.53 to -0.072 for bass weighing 73-1440 g. The double log regression of K on weight was similar to that reported for other poikilotherms (slope = -0.57; R = 0.93). Fingerling bass were eurythermal, being capable of surviving instantaneous temperature changes over a 20 C range at acclimation temperatures of 15, 25 and 30 C and over a 15 C range at acclimation temperatures of 20 and 35 C. Preferred temperatures for adult bass measured in the laboratory ranged from 27-32 C with no relationship to day or night. The overall mean preferred temperature was 29 C. The laboratory determined preferred temperatures were supported by limited field determined body temperatures taken in a vertical temperature gradient near the discharge of a power plant effluent. Routine metabolic rates of bass from a heated reservoir and a nearby hatchery were similar from 10-30 C in summer and winter. The weight exponent (0.77) and Q^gS (1*6-2.9) were similar to those published for more northern bass populations; however, the Texas bass had lower metabolic rates than those published for the northern populations. Bass exposed to rapid temperature increase (0.2 C/min) from 25-30 C increased their metabolic rate by 53% but showed no detectable increase in opercular rate. Bass warmed from 30-35 C and 30-33 C increased their metabolic rate by 140%, and their opercular rates increased to over 100 beats per minute before death.

Low oxygen tolerances of ten fishes were estimated using an original nitrogen cascade design, and reciprocally transformed to express responses as ventilated volume necessary to satisfy minimal oxygen demand (L·mg O2^-1). Values ranged from 0.52 to 5.64 L·mg^-1 and were partitioned into three statistically distinct groups. Eight stream fishes showed moderately high tolerances reflecting metabolic adaptations associated with stream intermittency. Juvenile longear sunfish and two mollies comprised the second group. High tolerance of hypoxia may allow juvenile sunfish to avoid predation, and mollies to survive harsh environmental oxygen regimens. The sheepshead minnow was the most tolerant species of low oxygen, of those examined, explaining its presence in severely hypoxic environments.

Knowing where species are and understanding why is paramount for developing relevant and sustainable conservation and resource management strategies. The need for this information is becoming urgent as fishing activity, resource extraction and the impacts of coastal developments continue to put marine resources under increasing pressure. As logistical and financial constraints can restrict our ability to collect data in the marine environment, the ability to predict distributions based on known associations with different environmental variables would enhance our capacity to manage these resources. Before attempting to predict the distribution of species and groups of species, the underlying species-environment relationships must be examined to determine whether associations between species and the environment can: (i) be identified, (ii) be used to develop models that can accurately predict distributions, and (iii) are general enough to allow accurate predictions beyond the sampled area. Most studies to date have compared the composition of fish assemblages between sites to determine how different environmental variables influence distribution. While widely applied, these methods do not consider how individual species respond to multiple environmental gradients and they lack the ability to predict distributions across different combinations of variables along those gradients. This lack of prediction also limits our capacity to assess what marine biodiversity is presently threatened by global, regional, and local human pressures on marine ecosystems. '...' Thus, summarising and modelling species data at higher levels would result in models with poorer predictive accuracy and a loss of ecological information. The generality of the species-environment relationships defined by the models were assessed by evaluating the transferability of models between different areas. Models developed from data collected over a wider geographic extent could more accurately predict the distribution of species across a smaller spatial extent than vice versa. This indicated that while general theories of the ecology of temperate demersal fish can be defined, the actual patterns of distribution may vary from site to site, suggesting caution when using predictions beyond the sampled area for management purposes. Overall, species distribution modelling identified how different species and groups of species responded to the combined influence of multiple environmental gradients and was able to accurately predict distributions based on the defined associations. Their application has led to a greater understanding of the species environment relationships and will help to identify those areas that may be important for conservation. Their predictive ability will allow general predictions of distribution of fish species across unsurveyed areas and provides the ability to assess the potential impact from implementing different policy and management strategies.

[Truncated abstract] The aim of this research was to define key species-environment relationships to better understand the spatial ecology of demersal fish. To help understand these relationships a combination of multivariate analyses, landscape analysis and species distribution models were employed. Of particular interest was to establish the scale at which these species respond to their environment. With recent high resolution surveying and mapping of the benthos in five of Victoria's Marine National Parks (MNPs), full coverage bathymetry, terrain data and accurate predicted benthic habitat maps were available for each of these parks. This information proved invaluable to this research, providing detailed (1:25,000) benthic environmental data, which facilitated the development and implementation of a very targeted and robust sampling strategy for the demersal fish at Cape Howe MNP. The sampling strategy was designed to provide good spatial coverage of the park and to represent the park's dominant substrate types and benthic communities, whilst also satisfying the assumptions of the statistical and spatial analyses applied. The fish assemblage data was collected using baited remote underwater stereo-video systems (stereo- BRUVS), with a total of 237 one-hour drops collected. Analysis of the video footage identified 77 species belonging to 40 families with a total of 14,449 individual fish recorded. ... This research revealed that the statistical modelling techniques employed provided an accurate means for predicting species distributions. These predicted distributions will allow for more effective management of these species by providing a robust and spatially explicit map of their current distribution enabling the identification and prediction of future changes in these species distributions. This research demonstrated the importance of the benthic environment on the spatial distribution of demersal fish. The results revealed that different species responded to different scales of investigation and that all scales must be ix considered to establish the factors fish are responding to and the strength and nature of this response. Having individual, continuous and spatially explicit environmental measures provided a significant advantage over traditional measures that group environmental and biological factors into 'habitat type'. It enabled better identification of individual factors, or correlates, driving the distribution of demersal fish. The environmental and biological measures were found to be of ecological relevance to the species and the scale of investigation and offered a more informative description of the distributions of the species examined. The use of species distribution modelling provided a robust means for the characterisation of the nature and strength of these relationships. In addition, it enabled species distributions to be predicted accurately across unsampled locations. Outcomes of the project include a greater understanding of how the benthic environment influences the distribution of demersal fish and demonstrates a suite of robust and useful marine species distribution tools that may be used by researcher and managers to understand, monitor, manage and predict marine species distributions.

Orientadores: Antonia Cecília Zacagnini Amaral, Gonzalo Velasco Canziani / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-21T03:44:21Z (GMT). No. of bitstreams: 1 Nascimento_MarcelaConceicaodo_D.pdf: 3923496 bytes, checksum: 6912623d364ceffac91fd80c0119c157 (MD5) Previous issue date: 2012 / Resumo: O ambiente marinho apresenta ecossistemas altamente ricos e diversos, entretanto o conhecimento sobre esses ecossistemas e os organismos que neles vivem ainda é muito esparso. Sabe-se que a perda de diversidade nesses sistemas vem crescendo sem ser apropriadamente avaliada. No Brasil, o desnvolvimento de novas fronteiras para a pesca e sua utilização, muitas vezes com pouca regulamentação e/ou fiscalização, tem levado muitos recursos à sobreexplotação. Esta forma de exploração evidencia o uso dos recursos marinhos sem um planejamento adequado. Para que haja tal planejamento, é necessário que se conheçam as vias energéticas e as relações entre os organismos que compõem esse ecossistema. De forma a contribuir para este conhecimento, no presente trabalho foram estudadas a dieta e as relações tróficas de seis espécies de peixes demersais abundantes nas regiões Sudeste e Sul do Brasil: Antigonia capros; Ariomma bondi, Genypterus brasiliensis, Synagrops bellus, Synagrops spinosus e Ventrifossa macropogon. O material provém das coletas do Programa REVIZEE Score-Sul, realizadas entre Cabo Frio (RJ) e Cabo de Santa Marta Grande (SC). Os peixes tiveram a sua dieta analisada por meio do conteúdo estomacal. Além da composição da dieta, foi avaliada a influência da profundidade, do tamanho dos indivíduos, da sazonalidade e do período do dia na obtenção de alimento. Adicionalmente, construiu-se um modelo trófico de balanço de biomassa para avaliar a comunidade demersal da área. Neste estudo foi observado que há um intenso consumo de invertebrados bentônicos, especialmente crustáceos, por todas as espécies, apesar de cada uma apresentar particularidades no comportamento alimentar, como foi constatado nas análises de dieta. Observou-se ainda que as espécies apresentam variações no consumo de alimentos relacionadas à profundidadade, tamanho dos indivíduos e área geográfica onde foram coletadas, e que os fatores que mais causam essas alterações são as variações sazonais. O consumo de invertebrados bentônicos verificado nas análises de dieta e no modelo é maior em espécies de níveis tróficos mais baixos, mas também é significativo em espécies de níveis superiores. Nesta última categoria estão inclusos grandes predadores, como tubarões e atuns, que puderam ser avaliados por meio de dados secundários na construção do modelo. Estes resultados ressaltam a importância da inclusão dos organismos bentônicos nas políticas pesqueiras e planos de manejo, uma vez que se trata de um dos principais pontos de sustentação de todo o ecossistema marinho, sobretudo o demersal / Abstract: The knowledge about marine environments and their rich and diverse ecosystems is improving across the world, but still has gaps, mainly in tropical areas. It is known that the diversity loss is globally increasing without being properly measured. Studies have shown that fisheries are looking for new areas and species aiming to attempt the global fisheries demand. This kind of resource exploitation brings evidence of inadequate fisheries planning. It is necessary the knowledge about the energy pathways and ecosystem relationships to develop appropriate fisheries management for different areas and objectives. Aiming to improve this knowledge and contribute to the appropriate fisheries management, we studied the diet and the trophic relationship of six abundant demersal fishes from Brazilian Southeast and South: Antigonia capros, Ariomma bondi, Genypterus brasiliensis, Synagrops bellus, Synagrops spinosus and Ventrifossa macropogon. The samples were collected during REVIZEE Score-Sul program, between Cabo Frio (RJ) and Cabo de Santa Marta Grande (SC). The fishes were studied based on their gut contents. It was evaluated the diet composition and the influence of depth, season, day time and specimens' size, on food choice. Additionally, we built a trophic model to evaluate the demersal community. We observed intense benthos consumption (especially crustaceans) by all species, despite their specificity. We also observed changes on food consumption according to depth, area and specimen's size, but the main responsible for changes on food consumption are the seasonal variations on the oceanographic dynamics. Benthos consumption is higher in low trophic levels than in high ones, but it is significant in high trophic levels species too, including top predators as sharks and tunas, assessed by secondary data during the model construction. These results show the necessity to include benthos impacts on fisheries management, once they are the main support of the entire marine ecosystem, especially demersal ecosystems / Doutorado / Ecologia / Doutor em Ecologia

The objectives of this project were to measure changes in frequency of occurrence of submerged macrophytes over the first two growing seasons following stocking with triploid grass carp at two fish per acre and to measure differences in macrophyte biomass between areas excluded from herbivory and adjacent control sites after 16 months following establishment of exclosures. The project also seeks to measure concentrations of fluridone following the herbicide treatment, and to compare two methods of aquatic vegetation sampling.

Twenty-nine (Group One, June 8,1995) grass carp (Ctenopharyngodon idella) and five (Group Two, April 18, 1996) grass carp were radio-tagged to monitor movement patterns and habitat preferences on North Lake, a 335 hectare multi-use reservoir located in Irving, Texas. Overall fish mean Average Daily Movement (ADM) rates were 49.2 meters/day (during Half One, 6/8/95-11/30/95) and 5.3 meters/day (during Half Two, 12/14/95-6/6/96). Aquatic macrophtye distribution data were obtained. Radio-tagged grass carp were located in Hydrilla verticillata infested areas increasingly throughout the study, however, percent frequency of Hydrilla along 15 transects did not decrease. Radio-transmitters were equipped with temperature-sensors (10-35 Celsius range). Results indicated that radio-tagged grass carp showed no avoidance of areas of North Lake with elevated water temperatures. Radio-tagged grass carp dispersed quickly from stocking point, then moved into littoral areas infested with Hydrilla. After an initial movement period, most fish remained in a localized area.

Population abundances of English sole within the San Francisco Bay from 1973 to 1981 showed a significant positive correlation with Delta outflows, and a significant negative correlation with salinity. Temperature in the bay and ocean upwelling showed no correlation with English sole abundance in the Bay. Because of the positive correlation between the abundance of English sole in the South San Francisco Bay and Delta outflow, this study suggests that any factor resulting in a reduction in outflow may reduce the abundance of English sole in the sample area.

Thesis (MSc)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: In this study, the Fish Assemblage Integrity Index (FAll) was applied on three rivers within the southwestern Cape. This index uses fish as indicators of biological aquatic integrity and is based on indigenous species expected to be present in biological fish habitats. Fish integrity classes were calculated for each of the sites in the three rivers studied. Sites 2 and 4 within the Lourens River were rated as Class C, whereas sites 1 and 3 were rated as Class F and Class D respectively. Sites 1, 2 and 4 within the Palmiet River were rated Class F, whereas sites 3 and 5 were rated as Class E and Class D respectively. Site 1 within the Hout Bay River was rated as a Class F site, in addition to sites 2 and 3 been rated as Class A. It is however, suggested that the FAll needs to be adjusted to accommodate the general low species richness experienced in the southwestern Cape. In addition to the FAll been applied, the effects of long-term exposure to subtle water quality changes associated with human activities, specifically potential estrogenic compounds in fish from the Lourens River were also investigated. The production of the yolk precursor lipoprotein complex, vitellogenin (Vtg) produced in the liver under estrogen control was employed as biomarker for environmental estrogen exposure. Male fish from the Lourens River were studied using SDS-PAGE gel electrophoresis. Results indicated that 60% of male fish showed the presence of Vtg in their plasma. Abnormal gonad morphology in male and female fish were also assessed using standard histological procedures. Results from this study indicated no observed abnormalities in either male or female gonads. The immediate presence of endocrine disrupters with estrogen activity was investigated by screening water samples from the Lourens, Palmiet and Hout Bay Rivers for estrogen activity. Results indicated that none of the samples appeared to be cytotoxic. In addition, estrogen activity of water samples was also investigated by in vitro culturing of water samples with frog, Xenopus laevis, liver slices. Results indicated that none of the water samples from the three rivers studied indicated estrogenic activity. Although cytotoxicity and estrogen activity results were negative, the production of Vtg in male fish suggests further research regarding the presence of estrogenic substances in these rivers. / AFRIKAANSE OPSOMMING: In die huidige studie is die 'Fish Assemblage Integrity Index' (FAIl) toegepas op drie rivere in die suidwes Kaap. Hierdie indeks gebruik visse as bioindikatore van biologies akwatiese integriteit en is gebasseer op die inheemse visspesies wat verwag word in biologiese vishabitatte. Integriteitsklasse is bepaal vir elke studieterrein in die drie rivere wat ondersoek is. 'n Klas C is bepaal vir studieterreine 2 en 4 in die Lourensrivier. Klas F en Klas D is bepaal vir studieterreine 1 en 3 in die rivier onderskeidelik. 'n Klas F is bepaal vir studieterreine 1, 2 en 4 en Klas E en Klas D bepaal vir studieterreine 3 en 5 in die Palmietrivier onderskeidelik. 'n Klas F is bepaal vir studieterrein 1 in die Houtbaairivier waar 'n Klas A bepaal is vir studieterreine 2 en 3. Dit word egter voorgestel dat die FAII aangepas moet word om die algemene lae spesierykheid wat ervaar word in die suidwes Kaap te akkomodeer. Die reaksie van visse, afkomstig van die Lourensrivier, op die langtermyn blootstelling aan estrogeniese stowwe is ook bestudeer. Spesifieke reaksies van endokriene versteuring, soos vitellogeen (Vtg) produksie in manlike visse is ondersoek deur middel van SDS-PAGE gel elektroforese. Resultate toon dat in 60% van die manlike visse Vtg in die plasma teenwoordig was. 'n Ondersoek na abnormale gonade morfologie in manlike en vroulike visse van die Lourensrivier is deur standard histologiese prosedures gedoen. Resultate hiervan dui op geen sigbare abnormaliteite in die gonades nie. Die onmiddelike teenwoordigheid van endokriene versteurders is bestudeer deur die sitotoksisiteit van watermonsters afkomstig van die Lourens, Palmiet en Houtbaai riviere te bepaal. Resultate dui aan dat geen monsters sitotoksies was nie. Die estrogeenaktiwiteit van die watermonsters is ook ondersoek deur van in vitro kulture van watermonsters saam met padda, Xenopus leavis, lewersnitte gebruik te maak. Geen estrogeniese aktiwiteit is in die watermonsters gevind nie. Al is die sitotoksisiteit en estrogeenaktiwiteit resultate negatief, dui die produksie van Vtg in manlike visse op die noodsaaklikheid van verdere navorsing ten opsigte van die teenwoordigheid van estrogeniese stowwe in drie riviere.