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Thesis (Ph. D. (Physiology)) -- University of Limpopo, 1993 / Refer to document

Thesis (Ph.D (Zoology)) --University of Limpopo, 2018 / Freshwater ecosystems are the most threatened systems globally, suffering from channel modification, over extraction of water and, of particular concern, pollution. In South Africa, Olifants River is categorised as the third most polluted river system. Acid mine drainage seeping from derelict and abandoned mines has been described as the primary stressor in the upper Olifants catchment. The increase of metal concentration in the water, sediment and fish tissues has been evident over the past few decades. As a result, there has been an increasing concern regarding the effects of increased metal concentrations on the health of fish and the safety of communities consuming fish from the polluted Olifants River system. This study used enzymatic and histopathologic biomarkers to assess the physiological response of Oreochromis mossambicus and Labeo rosae to environmental contaminants. The study further investigated the metal accumulation trend of across different fish tissues and assessed the edibility of O. mossambicus and L. rosae from Loskop and Flag Boshielo dams. Water, sediment and fish samplings were carried out concurrently during low flow and high flow seasons in 2014. Water and sediment sampling were done at the inflow, middle and dam wall. A minimum of 10 fish specimens for each species were collected from Loskop and Flag Boshielo dams during each sampling. For bioaccumulation analysis, liver, gill and muscle tissues were dissected out, wrapped with aluminium foil and frozen. Frozen samples were sent to SANAS accredited laboratory for metal analysis. For Histopathology, tissues were fixed in 10% neutral buffered formalin prior processing. Tissue processing was done at the Pathology laboratory of the University of Pretoria, Onderstepoort campus. For biomarker analysis, liver and brain tissues were fixed in liquid nitrogen in the field and transferred to the -80°C biofreezer at the University of Limpopo, Biotechnology Unit laboratory. Metal concentrations in the muscle tissue were used to calculate hazard quotient for human health risk assessment which was based on the assumptions that an adult weighting 70 kg consume 150 g portion once per week. Alkaline pH was observed in the water throughout the study. Most water constituents were within the guidelines at both dams. The water at Flag Boshielo Dam was oligotrophic with Loskop Dam showing mesotrophic conditions. Concentrations were below detection level for most metals; however, significant concentrations were recorded in the bottom sediment. Although Loskop Dam is being described as a repository for pollutants from the upper Olifants catchment, no significant differences (p>0.05) were observed for metal concentrations in sediment between the two dams. Coinciding with sediment metal concentrations, liver, gills and muscle have shown notable concentrations for both species at Loskop and Flag Boshielo dams. The common trend of liver accumulating higher metal concentration followed by gill and muscle (liver>gills>muscle) was observed for most metals on O. mossambicus and L. rosae at both dams. In contrast, lead, strontium and manganese showed higher concentrations in the gills. Muscle exhibited lowest concentrations for most metals. Remarkable trends on the activities of biomarkers, lactate dehydrogenase (LDH), glucose-6-phosphate dehydrogenase (G6PDH), glutathione-S-transferase (GST) and acetylcholinesterase (AChE) were detected for both species at Loskop and Flag Boshielo dams. Labeo rosae population have shown a significantly high (p<0.05) LDH activities at Loskop Dam and no significant difference (p>0.05) was observed for Oreochromis mossambicus. Glucose-6-phosphate dehydrogenase activities exhibited no significant difference (p>0.05) for both species between the two dams. Labeo rosae have shown a significantly high (p<0.05) GST activities at Loskop Dam whereas Oreochromis mossambicus exhibited no significant difference (p>0.05) between the two dams. Acetylcholinesterase (AChE) has shown no significant difference (p>0.05) for both species between the Loskop and Flag Boshielo dams. LDH, G6PDH and GST activities have shown relationship with metal concentrations, which makes them good biomarkers of metal exposure.The condition factor indicated that overall conditions of O. mossambicus and L. rosae from Loskop and Flag Boshielo dams were good. Hepatosomatic index results were not conclusive. Most histopathological alterations were recorded on both species at both dams, but with different magnitude of severity. Regressive changes were more prominent in the liver and gills of both species at Loskop and Flag Boshielo dams followed by progressive change. Gills of Oreochromis mossambicus exhibited moderate modifications (score >20) at Loskop Dam and slight modification (score <20) at Flag Boshielo Dam. Labeo rosae populations have shown slight modifications (score <20) in the gills at both dams. Both species have shown significant difference (p<0.05) on the gill index between the two dams. Liver index has also exhibited significant difference (p<0.05) for each species between Loskop and Flag Boshielo dams. Slight modifications (score <20) were observed in the liver for both species at Loskop and Flag Boshielo dams. Both species have shown to accumulate metals within their tissues with liver accumulating higher concentration for most metals, followed by gills and muscle, respectively. Although muscle showed to accumulate lesser metal concentrations, it still raise a serious concern as it is the tissue consumed by human. Lead, chromium, cobalt and antimony concentrations have been the only metals of concern in this river system over the past few years; nevertheless, the present study has shown that other metals viz. arsenic, silver and selenium have exceeded international levels for safe consumption. Given the metal concentration trend reported over the past two decade in fish tissues, there is a need for urgent intervention to address the acid mine drainage problem to ensure sustainable development of the Olifants River and safety of communities depending on it for their livelihood. / NRFand RAD

Saltmarshes in SE England are eroding rapidly and one potential impact is the loss of habitat for fishes. Saltmarshes have been created by setting back the existing line of flood defence through managed realignment. The use by fishes of natural and managed realignment habitats at Tollesbury, Abbotts Hall and Orplands was examined (2005-07). Three seasonal groups were apparent in the fish assemblages of the managed realignment sites: February-April (Pomatoschistus microps and Sprattus sprattus), May-September (Dicentrarchus labrax and Atherina presbyter) and October-January (Liza aurata and Liza ramada). The sites were used mainly by 0- and 1-group fishes and adult P. microps. The mean abundance (July - August 2007) was 558 0.1 ha' (range 76 - 2699 0.1 ha'). In summer, small (< 30 mm) zooplanktivorous D. labrax fed successfully at all sites. Larger (30-59 mm) D. labrax consumed more macroinvertebrates in the Tollesbury managed realignment and two established marshes than at Abbotts Hall and Orplands. By autumn there were no site-specific differences in gut fullness of D. labrax. Stable isotope ratio analysis and gut contents analysis revealed that small (< 50 mm) D. labrax, S. sprattus and A. presbyter assimilated zooplankton which eat detritus, resuspended microphytobenthos and some phytoplankton. L. aurata assimilated zooplankton and microphytobenthos. P. microps (20-50 mm) and A. presbyter (80-99 mm) assimilated benthic meiofauna. Larger (50-230 mm) D. labrax assimilated macroinvertebrates which eat microphytobenthos, Ulva spp., C3 plants and detritus. Some recommendations for saltmarsh restoration are provided with an estimate of the economic value of bass in saltmarshes,to highlight further areas of research.

Inflows affect water quality, food web dynamics, and even the incidence of harmful algal blooms. It may be that inflows can be manipulated to create refuge habitat for biota trying to escape poor environmental conditions, such as fish populations in lakes during times of toxic Prymnesium parvum blooms. Water availability sometimes can be an issue, especially in arid climates, which limits this approach to management. Utilizing source water from deeper depths to displace surface waters, however, might effectively mimic inflow events. I test this notion by conducting in-lake mesocosm experiments with natural plankton communities where I manipulate hydraulic flushing. Results show that P. parvum cell density is reduced by 69%, and ambient toxicity completely ameliorates during pre-bloom conditions in the lake. During conditions of bloom development, population density is reduced by 53%, toxicity by 57%, and bloom proportions are never reached. There is minimal effect of these inflows on total phytoplankton and zooplankton biomass, and little effect on water quality. Shifts toward more rapidly growing phytoplankton taxa are observed, as are enhanced copepod nauplii. In other words, while inflows using deep waters suppress P. parvum bloom initiation and development, they are benign to other aspects of the lower food web and environment. The results from using deep lake water to suppress harmful algal blooms indicate this may be a promising management approach and further studies are recommended to test whether this mitigating effect can translate to a large-scale in-lake treatment.

In the Maritimes, only two striped bass spawning populations remain: the Miramichi River in New Brunswick and the Shubenacadie – Stewiacke system in Nova Scotia. The Shubenacadie – Stewiacke system is subjected to a well pronounced twice daily tidal bore which induces dramatic changes in water parameters and challenges pelagic life. This system will be subject to potential change through brine discharge, a by-product of the Alton Natural Gas Storage Project. . Examining the temporal distribution of mysids, striped bass eggs and larvae at a fixed location around the Alton Project site will provide baseline information on population structure and insights into how egg and larvae distributions change with respect to tidal cycles, temperature and salinity. Surface plankton net tows from the top 0.75m of the water column were used to collect mysids, striped bass eggs and larvae over 14 months over two years. Daily mean egg abundance surpassed 1000 eggs/m3 once in 2008. A decrease of 1.9 °C in water temperature at the Alton Project site coincided with a cessation of eggs, and presumably, spawning. Spawning resumed when temperatures surpassed 15 °C. In contrast, the largest spawning event of the 2009 season occurred as water temperatures decreased (14 to 12.7 °C). The 2009 spawning season was longer (49 days) than 2008 (31 days) by 18 days, and in both years spawning peaked within the last week of May and first week of June. Two large spawning events, over 4000 daily mean eggs/m3 apiece, were detected May 24 and June 2, 2009. Mysids were present in high numbers throughout May to November, with some tows greater than 14,000 individuals/m3 in June 2008 and August 2009. Over the length of the ebb tide, as salinity decreases, mysid abundance also decreased. Whereas, striped bass egg abundance was consistently lowest at high tide and increased progressively over about 300 minutes through the ebb tide. Both striped bass larvae and mysids displayed patchiness in their temporal distribution suggesting passive transport in the this system. In both 2008 and 2009, larvae were detected at the Alton Project site for 38 days. The colder temperatures and larger tidal range of 2009, coupled with large increase in rainfall during the larval season contributed to the over 30-fold lower abundance over that found in 2008. When abundance was related in concert with temperature and salinity, mysids were ever present at high abundances except on three occasions. Mysid abundance decreased when salinity dropped beneath 5 ‰ during both years, and in 2008 when temperatures were lower than 15 °C. Salinity was impacted according to a seven-day lag after rainfall in both years, although the minimum volume of rainfall and associated impact on salinity have yet to be described.

This thesis describes the design of fish ladder on the river Mohelka near the village Chocnějovice. The first section describes the general characteristics of the river-basin and the selected section. It is written introduction to the design, construction and service of the fish ladder. For the task were developed two alternatives. These alternatives were described and compared each other. Included are the input and output data of the given structure modeling using HEC-RAS. The last part is then researched drawings to objects.

Streams and rivers are examples of vital ecosystems that frequently undergo various environmental and anthropogenic stresses. A core question in population ecology is whether a given population will persist under changing ecological conditions. This thesis consists of three papers and is devoted to the mathematical analysis of responses of river-dwelling species to population persistence threats. The first paper presents a stochastic approach to the 'drift paradox' problem, where the classical reaction-advection-diffusion model is replaced by a birth-death-emigration process. We explore the effects of temporally varying flow on the persistence probability and highlight the importance of the benthic stage for the persistence of stream organisms. The second paper addresses the problem of river network fragmentation through disconnecting structures such as dams. We construct a population matrix model that incorporates the spatial structure of the studied river network and compare structural connectivity to an indicator of population persistence. The third paper adapts the same basic matrix model to examine fish response to disturbances travelling downstream from upstream sites. The study of these three aspects of persistence challenges for river populations contributes to the cumulative effects assessment on river networks.

This study was designed to determine if impingement and entrainment by cooling water intake at the Comanche Peak Steam Electric Station have an adverse impact upon the Squaw Creek Reservoir fish population. The yearly impingement of fish was estimated to be 262,994 of 14 species. The threadfin shad (Dorosoma petenense) accounted for 96% of this total. Entrainment of eggs and larvae for a five month period was estimated to be 15,989,987 and 42,448,794 respectively. Two fish population studies were performed on Squaw Creek Reservoir to help assess impact. It was determined that the losses due to impingement and entrainment have no adverse impact upon the fish population of Squaw Creek Reservoir.