Selected limnologic characteristics were examined at an east-central Indiana borrow pit lake to determine the role of submerged aquatic plants in water chemistry dynamics. During the summer of 1978 the lake was sampled at approximately weekly intervals in the evening and again the following morning in the shallow macrophyte area and the deeper open water control area void of macrophytes. Alkalinity, dissolved oxygen, and pH were evaluated for changes induced by macrophytes and Aufwuchs.Maximum macrophyte dry weight biomass was observed in the middle of July, after which the plants died off quickly. Potamogeton pusillus and P. pectinatus were the dominant species present.Dissolved oxygen levels were found to be higher in the evening and lower in the morning due to photosynthesis and respiration of aquatic plants at the macrophyte siteas compared to the control site. Daily variations in alkalinity at the macrophyte site were more intense than recorded at the control site. During the day, bicarbonate alkalinity was decreased and carbonate alkalinity increased at the macrophyte site. Diurnal fluctuation of hydrogen ion concentration was also greater at the macrophyte site than at the control site. Metabolism by macrophytes and Aufwuchs greatly influenced the water chemistry of Dumpert's Borrow Pit Lake.Laboratory studies have identified fluctuating levels of dissolved oxygen as a stress on fish resulting in reduced growth. A pilot experiment was conducted to determine the effects of macrophyte and Aufwuchs induced diurnal fluctuations of dissolved oxygen on growth, food consumption, and food conversion by adult bluegill fed mealworms ad libitum. Average growth, food consumption, and food conversion were lower for bluegill exposed to macrophyte-induced water quality changes. None of the differences were significant, however, due to variability and the small sample size.Ball State UniversityMuncie, IN 47306

No description available.

M.Sc. (Zoology) / An investigation was made into the ecology of Barbus brevipinnis and Opsaridium zambezense in the Incomati River System in the Eastern Transvaal. Special attention was given to factors which may threaten the existence of both species. New information was collected on aspects concerning their length:mass relationship, condition, fecundity, feeding habits as weIl as parasites. Measurements were made of the standard, fork and total lengths of both species, which in each case was related to the specific mass of the fish. Both species are, according to the information obtained, capable of successive spawning over an extended period during the breeding season. This implies that the evaluation for fecundity according to standard procedures may in both species be conservative in terms of estimates of the total numbers of eggs produced during the breeding season. Indications are, however, that of Zambezense may produce relatively low numbers of eggs and this as weIl as certain environmental factors, may in combination explain the relative scarcity of this fish in the Inkomati River System. Environmental pollution may further complicate this issue. One of the main objectives of this study was to investigate the habitat requirements of both species. In doing so, both species can now be better defined in terms of certain biological requirements as welI as environmental conditions under which they occur. It is hoped that this information may contribute towards a better understanding of the environmental conservation status of both species. The scarcity collection of studies into including GSI. of both species prohibited the large scale specimens normally required to enable intensive factors such as feeding, growth and breeding, It was therefore not possible during this study to obtain an accurate assessment of parameters such as fecundity, which should be investigated in more detail if and when material on both species becomes available. Recommendations are made concerning morphometric and electrophoretic investigations of both species in order to evaluate their species status more accurately. It is suggested that the habitats where B.brevipinnis and O.zambezense occur be closely monitored in future to observe any further deterioration which may be caused by agricultural and mining activities. It is recommended that because of the relative scarcity of Zambezense in the Inkomati River System, and to the apparent sensitivity of this species to environmental disturbance of its habitat, its conservation status be changed from indeterminate scarce to vulnerable.

Ph.D. (Zoology) / Please refer to full text to view abstract

D.Sc. (Zoology) / Please refer to full text to view abstract

Alterations of streams to facilitate highway construction and consumptive water use has become a fisheries management problem. To evaluate the effects of channeling concomitant to construction of Interstate 80 N. near Henefer, Utah, altered and unaltered sections of the Weber River were compared on the basis of fishes censused, population estimates and ordinations. Species compositions in particular areas were influenced by local rheologic conditions. Changes in species composition between samplings at a particular area were caused by fish movements. Data from altered sections, rehabilitated with deflectors and checkdams, were not noticeably different than data from unaltered areas. However, fish movements indicated an unstable environment throughout the study area. This shows that it may be possible to restore channeled streams to productive fisheries.

Ecologists have long questioned why fluctuating populations tend to persist rather than go extinct. Populations that persist indefinitely are regulated by mechanisms that cause demographic density dependence, which works to bound fluctuation above zero. In a series of studies, I have sought to determine the processes and mechanisms that regulate local populations of coral-reef fish. In the Exuma Keys, Bahamas, fairy basslets (Gramma loreto) live in aggregations on the undersides of coral-reef ledges. These aggregations often constitute local populations because movement between aggregations is rare. The largest individuals occupy prime feeding positions near the front of ledges and force smaller individuals remain near the back where they have lower feeding rates. Based on these initial observations, I designed two experimental studies of the demographic consequences of variation in basslet density. In the first study, I manipulated the density of newly-settled fish to explore the effects of high recruitment on population size. Populations with experimentally elevated recruitment converged in density with unmanipulated populations, primarily due to density-dependent mortality. I found no evidence that density dependence was caused by intraspecific competition; rather it appeared to be due to a short-term behavioral response by predators (aggregative and/or type 3 functional response). In a second study, I manipulated the densities of adults among populations with a standard average density of newly-settled fish. Two measures indicated that the intensity of competition increased at higher densities of adults, which likely made small fish more susceptible to predation, thereby causing density-dependent mortality. Long-term observations indicated that basslet populations were regulated at temporal scales exceeding two generations. At Lizard Island on the Great Barrier Reef, I also examined how patterns of recruitment of coral-reef fishes were modified across a range of natural recruit densities in the presence and absence of resident predators. Predators decreased recruitment and increased mortality for all species, but these effects varied considerably among species. The results of each of these studies stress the importance of both competitive and predatory mechanisms in modifying patterns of abundance established at the time of larval settlement, as well as regulating local population size. / Graduation date: 2002

Distribution patterns and levels of genetic diversity in extant taxa are a product of complex palaeogeographic processes and climatic oscillations as well as the species’ intrinsic ecological adaptations. The Cape Floristic Region of South Africa presents a unique system for studying the processes that promote species diversification and distribution patterns. This region has a high degree of endemism of both terrestrial and aquatic biota and is clearly isolated from neighbouring areas by the Cape Fold Mountains and the Great Escarpment. The objective of this study was to firstly examine the ecology of freshwater fishes belonging to the genera Galaxias, Pseudobarbus and Sandelia in the south-western CFR. This was followed by an assessment of the genetic diversity of these taxa. Unique lineages were identified and their distribution was mapped. The work aimed to explore the role of the region’s complex palaeogeographic and climatic history as well as the role of the species’ ecological adaptations in driving lineage diversification and shaping contemporary distribution patterns. The four main components of the study can be summarised as follows: 1. Habitat associations of three widely distributed lineages of Galaxias zebratus Pseudobarbus burchelli and Sandelia capensis were evaluated at multiple localities in minimally disturbed mountain tributaries of the Breede, Duiwenhoks and Goukou River systems. The lineages have distinct habitat associations which were related to differences in their morphological traits. The slender-bodied Galaxias ‘nebula’ and the fusiform-shaped Pseudobarbus ‘Breede’ are capable of exploiting upper reaches with faster water velocity. By contrast, the laterally compressed Sandelia ‘eastern’ is restricted to lower reaches, making this lineage more susceptible to a wide array of impacts. 2. A recently discovered lineage of Galaxias zebratus, (Galaxias ‘nebula’), was found to be capable of tolerating emersion for a prolonged period of time. This is the first time that such capabilities have been documented in an African galaxiid. These adaptations have implications for the interpretation of Galaxias ‘nebula’s wide distribution range. 3. The phylogeography of Galaxias ‘nebula’ across its entire distribution range was investigated using two mitochondrial genes (cytochrome c oxidase subunit I (COI) and cytochrome b (cyt b)). This lineage has a complex evolutionary history that was influenced by both intrinsic and extrinsic factors. Rare events such as episodic drainage connections during Pleistocene and Holocene pluvial periods, possibly augmented by river confluences during periods of lower sea-levels and river capture events seem to be the most credible explanation for the extensive contemporary distribution and the relatively shallow genetic divergence between different river systems. 4. Mitochondrial cyt b sequences were used (i) to assess genetic diversity in G. zebratus, P. burchelli and S. capensis from the south-western CFR and (ii) to determine the roles of intrinsic ecological adaptations and extrinsic landscape and climatic changes in promoting genetic diversification and shaping present day distribution patterns of lineages in the three taxa. Marine incursions during periods of major sea-level transgressions are proposed to have isolated populations in upland refugia, thereby driving allopatric divergence in these species. Subsequent connections of rivers during wetter periods and lower sea-levels are proposed to have facilitated post-speciation dispersal of lineages to attain present day distribution patterns. While detailed morphological studies and further genetic analysis are needed to substantiate the taxonomic status of the newly discovered lineages of Galaxias zebratus, Pseudobarbus burchelli and Sandelia capensis, results of the present study indicate that the south-western CFR represents a previously unrecognised centre of freshwater fish diversity and microendemism in the broader Cape Floristic Region. Accurate identification of lineages and comprehensive mapping of their distribution is a fundamental pre-requisite for ecological studies, assessing conservation status and implementation of appropriate conservation measures.

The primary aim of this study was to investigate the population dynamics of the fishes associated with a small (17.5 hectares) temporarily open/closed estuary on the south east coast of South Africa. The results are based on the findings of an intensive sampling programme conducted over a period of four years in the East Kleinemonde estuary (33° 32' S : 27° 03' E). By adopting a quantitative approach, this study addresses the need for information on estuarine-associated fish population sizes, standing stock (biomass) estimates and productivity. The ichthyoplankton assemblage in the surf zone adjacent to the mouth of the estuary was dominated by postflexion larvae representing at least 21 taxa in 14 families. Rhabdosargus holubi of sizes ranging between 9 mm and 21 mm BL was the most abundant species with a mean density of 7.3 individuals per 100 m'. This species, which accounted for 77.6% of the catch composition, was recorded throughout the year but revealed a distinct peak in abundance in spring (August - September). The ichthyofaunal community within the East Kleinemonde estuary was dominated by juvenile marine-spawning species and typical of a warm temperate southern African estuary. A total of 30 species in 17 families was recorded, including the endangered estuarine pipefish Syngnathus watermeyeri. Multivariate analyses (classification and ordination) of the catch assemblages revealed a high degree of similarity (> 70%) throughout the estuary, with two distinct groups being identified on the basis of substratum type. The sampling stations near the mouth with a sandy substratum were distinguished from all other sampling sites in the estuary. The dominant estuarine-spawning species were represented by all life-history stages, suggesting that they bred successfully in the estuary. This group was numerically and gravimetrically dominated by the two zooplanktivorous shoaling species Gilchristella aestuaria and Atherina breviceps with density extrapolated population size estimates of 420 973 and 198 275 individuals, and biomass estimates of 1.6 and 0.6 g m⁻² respectively. The total population size of all estuarine-spawning species with a mean biomass 00.4 g m⁻² was estimated at 754 217 individuals. Population size estimates of the marine-spawning species were calculated using data obtained from three independent mark-recapture experiments. The assumptions for the mark-recapture analyses were adequately met and it was concluded that the techniques provided reliable estimates of population size. However, estimates obtained from density extrapolation revealed enormous variability and were considered to be unreliable. The total population size was estimated at 63 342, 18 592 and 13 5 192 during the three mark-recapture experiments respectively. The numerically dominant species during all three experiments was Rhabdosargus holubi. Biomass production of the marine-spawning species was evaluated over a 123 day census period when population sizes and estimates of growth rates were known. Productivity for all fishes with a standing stock of 26.2 g m⁻² was calculated at 4.5 g m⁻² month01 Rhabdosargus holubi accounted for more than 75% of the total marine fish productivity. This study draws attention to the success of Rhabdosargus holubi in the East Kleinemonde estuary, which is ascribed to aspects of its biology. These include an extended breeding season, the ability to recruit into the estuary under adverse open mouth conditions and its omnivorous food habits. The dominance of this migratory species suggests that it plays an important role in the transfer of energy to the coastal marine environment when the mouth of the East Kleinemonde estuary opens. Predation by birds and a dominant piscivorous fish (Lichia amia) was quantitatively assessed over a period of two years. Monthly food consumption by all piscivorous birds revealed large temporal variability, ranging from 32 to 466 kg month-I An unusual invasion of Cape cormorants during the winter of 1994 accounted for large scale mortality (2246 kg of fish) over a relatively short period. The predatory impact of this episodic event was reflected in the findings of the fish mark-recapture experiments, which revealed a 70% reduction in the total population of marine-spawning fishes (above a certain minimum size) in the estuary subsequent to this invasion. Monthly food consumption by the Lichia amia population in the estuary was calculated at 68 and 58 kg month-I for two distinct time periods when the population size was known. These findings suggest that this species is the top piscivorous predator in the East Kleinemonde estuary. Finally, the findings of this study highlight the temporal variability of fish populations within a single estuary. It is suggested that predation and estuary mouth conditions are the main factors influencing the abundance (and its variability) of individual species in the East Kleinemonde estuary.

Orientadores: Ivan Sazima, Carlos Eduardo Leite Ferreira / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-18T21:56:33Z (GMT). No. of bitstreams: 1 LuizJunior_OsmarJose_M.pdf: 5451042 bytes, checksum: 29619a9d7010f69a9bd352d2cbc12792 (MD5) Previous issue date: 2009 / Resumo: O Parque Estadual Marinho da Laje de Santos localiza-se na costa sudeste do Brasil a 36 km da cidade de Santos, Estado de São Paulo. O Parque consiste uma pequena ilha (Laje de Santos) com vários parcéis rochosos submersos. O substrato é composto por rochas graníticas cobertas por algas e várias espécies de invertebrados. Desde 1993, foi declarada como área de proteção marinha e desde então o local é de particular interesse, pois é a única área totalmente fechada para a pesca na região mais povoada e desenvolvida do país. Uma lista com 196 espécies de peixes recifais registradas é apresentada para o Parque Estadual Marinho da Laje de Santos. A maioria das espécies tem ocorrência comum a todo o Atlântico Ocidental tropical ou ocorre nos dois lados do Oceano Atlântico. Uma parte menor das espécies tem distribuição em comum com os recifes rochosos temperados da Patagônia ou é endêmica ao Sudeste do Brasil. Moringua edwardsi, Antennarius multiocellatus, Scorpaena dispar, Aulostomus strigosus, Lutjanus buccanella, Mulloidichthys martinicus and Halichoeres penrosei tem aqui seu limite merional de distribuição estendido ao Estado de São Paulo. Há uma clara diferença na contribuição dos fatores abióticos para a estruturação da comunidade de peixes recifais. A profundidade foi o fator que mais influenciou a riqueza de espécies e abundância de indivíduos, apresentação uma clara distinção ambiental entre raso e fundo, com um decréscimo da riqueza e abundância conforme o aumento da profundidade. A complexidade do habitat também foi um fator de influência na comunidade, sendo a riqueza e abundância correlacionada com maior complexidade. Entretanto, esta relação só foi significativa na menor profundidade avaliada. A exposição às ondas não se correlacionou com nenhum dos descritores da comunidade utilizados neste estudo. Aparentemente os efeitos do hidrodinamismo em recifes rochosos se manifesta em escalas espaciais maiores entre a costa e ilhas com diferentes distâncias da costa. Espécies de diferentes categorias tróficas não respondem da mesma maneira a estes fatores. Herbívoros vagueadores são afetados pela profundidade, herbívoros territoriais pela complexidade e pela exposição a ondas, enquanto que planctívoros são afetados pela complexidade do habitat e em menor extensão pela profundidade. Análises de espécies filogeneticamente relacionadas sugerem que ocorre partição de nicho, aparentemente mediada pela capacidade de natação em resposta ao grande dinamismo que ocorre nas zonas rasas. A água fria oriunda de eventos de reesurgência foi um fator de redução da abundância e número de espécies capazes de extender sua distribuição batimétrica para as zonas mais fundas, desencadeando respostas comportamentais específicas em algumas espécies como a formação de densos cardumes na camada superficial durante os eventos de ressurgência. Herbívoros vagueadores e onívoros foram os grupos tróficos que foram particularmente afetados pela intrusão de água fria. Em geral, espécies com alta capacidade de mobilidade evitam a camada de água fria abaixo da termoclina durante o verão e espécies de pequena capacidade de mobilidade ou extremamente territoriais não alteram sua abundância em resposta estes eventos / Abstract: The Laje de Santos State Marine Park is located on the southeastern coast of Brazil, 36 km off the city of Santos, São Paulo State. It consists of an uninhabited islet and several sparse rocky reefs with extensive sand bottoms in between. The subtidal substrate is composed of granitic boulders of varying sizes and shapes. The rocky substrate is mainly covered with patches of algae and several species of sessile invertebrates. Since 1993 the Laje de Santos Island was declared a protected area. The area is of particular interest as this is the only Marine Protected Area totally closed to fishing in the most populated and developed region of Brazil. A check-list containing 196 species of reef fishes recorded at the Laje de Santos Marine State Park is presented. Most of them occur along the tropical western Atlantic or occur on both sides of the Atlantic Ocean. A minor part ranges to the temperate rocky reefs of Patagonia or are endemics to southeastern Brazil. Moringua edwardsi, Antennarius multiocellatus, Scorpaena dispar, Aulostomus strigosus, Lutjanus buccanella, Mulloidichthys martinicus and Halichoeres penrosei have here their ranges extended southward to the São Paulo coast. There is a clear difference among the contributions of each abiotic factors analyzed in the reef fish community structure. Depth was the most influent factor on species richness and abundance, presenting a clear distinction between shallow and deep zones with a decrease of both factors with depth increase. Habitat complexity also had an influence in the community, being species richness and abundance correlated with higher complexity. However, this relationship was significant on the shallower evaluated depth only. Exposition to wave surge does not correlate with any of the community descriptors used in this study. Apparently, hydrodynamics effects on rocky reefs manifest only at larger spatial scales like between the shore and islands. Species on different trophic categories do not respond the same way to these factors. Vagrant herbivores are affected by depth; territorial herbivores by habitat complexity and marginally by exposition, and planktivorous are affected mostly by habitat complexity and in less extension by depth. Analyses of phylogenetically related species suggest that niche partitioning occur, apparently mediated by swimming capacity in response to higher hydrodynamic forces occurring in shallow water. Cold water derived from upwelling events was a further factor reducing species richness and abundance, triggering specific behavioral responses in some species such as the formation of tight packed schools in the surface layer during upwelling. Vagrant herbivores and omnivores were the trophic groups most affected by upwelling. In general, species with high mobility capacity avoid the cold-water layer below the thermocline during summer and species with limited mobility capacity do not change their abundance is response to these events / Mestrado / Ecologia / Mestre em Ecologia