Dusky kob, Argyrosomus japonicus and spotted grunter, Pomadasys commersonnii occur off South Africa’s southern and eastern seaboard. They are the preferred target species for both shore and estuarine anglers. In order to sustain the billion rand recreational angling industry, healthy fish populations are of the utmost importance. However, A. japonicus is currently overexploited, with the species’ spawner biomass estimated at 1-4.5% of pristine levels. Pomadasys commersonnii spawner biomass is estimated at 40% of pristine levels, thus indicating that the species is not overexploited. For effective management of our marine resources, information about the population size, structure, dynamics and population history of individual species is needed. Genetic data can make a valuable contribution to a holistic stock determination, approach, as powerful tools in unraveling population history. Genetic variation gives a reflection of the evolutionary differences within and between populations and allows for indirect assessment of population connectivity and gene flow levels. The mitochondrial DNA (mtDNA) control region is a useful marker in population studies, due to its high substitution rate. The haploid nature of the mtDNA, maternal inheritance and the absence of recombination, means that the signal obtained from genetic drift is stronger than that for nuclear loci. For this reason the mtDNA control region was analysed for 133 juvenile A. japonicus and 139 P. commersonnii samples from four localities along their South African distribution, to determine the genetic diversity and differentiation among the coastal regions. Juvenile A. japonicus are resident around their natal estuaries until they reach sexual maturity. This residency of juveniles makes them ideal candidates to give a reflection of A japonicus population dynamics, especially to determine if any isolation-by-distance exists along the coast. In the case of P. commersonnii, both juveniles and adults were analysed, since adults are resident around their natal estuaries when not undertaking spawning migrations. High levels of genetic diversity were found in both A. japonicus and P. commersonnii, comparable to that observed in other marine fish species. No significant population differentiation results were obtained, possibly due to the small sample sizes collected or to lack of resolution in the marker. In A. japonicus, where spawning is known to occur off KwaZulu-Natal and off the southern Cape coast, possible isolation-by-distance was detected. This indicates that the adult A. japonicus population probably does not consist of one freely intermixing unit, but rather of geographically separated spawning units. For P. commersonnii, where spawning has only been recorded off the KwaZulu-Natal coast, no population differentiation was observed, indicating that the different regions along the South African coast are highly connected. In conclusion, through future analysis of larger sample sizes, preferably from single cohorts, some of the noise will be reduced and more conclusive answers with respect to female gene flow could be provided. In the case of A. japonicus the use of microsatellite markers which are better at detecting fine-scale differentiation and provide estimates of total gene flow, will be informative. At a broader geographic scale, it will be important to assess differentiation among Dusky kob populations from throughout the Western and Eastern Indian Ocean. As far as P. commersonnii is concerned, it is recommended that a comparison be undertaken to determine the relationship; of the South African population to that found along the Mozambican coast. / Dissertation (MSc (Genetics))--University of Pretoria, 2005. / Genetics / unrestricted

The proximate composition of juvenile spotted grunter, Pomadasys commersonnii and their major prey items were analyzed to test the hypothesis that the dietary protein requirements would approximate the composition of the natural diet. The amino acid profile of juvenile P. commersonnii was analyzed to establish the pattern of limiting amino acids for this species. Juvenile P. commersonnii feed primarily on the mysid, Mesopodopsis slabberi, which has a protein content of 58.27±0.04% and a calorific value of 19.2kJ/g. The first-limiting essential amino acid for this fish was found to be lysine and it was predicted that the optimal dietary protein requirement would be between 50 and 60%. The optimal dietary protein inclusion level was investigated by feeding semi-purified diets containing graded levels of protein, ranging from 37-62%. Maximum growth was found to occur at dietary protein levels ranging from 40-51%. The best food conversion ratio was achieved at 56% dietary protein and the best protein efficiency ratio was obtained at a dietary protein inclusion level of 37-40%. The protein to energy ratio was defined by feeding 3 different protein levels at 3 different P:E levels. These semi-purified diets contained 35, 45 or 55% protein and 6, 8 or 12% dietary lipid, resulting in protein to energy ratios ranging from 21.1 to 42.3mg/kJ. The optimal P:E ratio for this species was found to be 26.7mg/kJ. This diet effected a low food conversion ratio (1.72±0.19), a low hepatosomatic index (4.01±0.23) and a high specific growth rate (5.96±0.36). The essential amino acid requirements of juvenile P. commersonnii were investigated. Semi-purified diets were formulated to contain graded levels of crystalline lysine based on the amino acid profile of the whole body and fed to the fish for a period of 60 days. Fish fed the "ideal protein" diet had significantly higher (p<0.05) specific growth rates (2.95±0.18), protein efficiency ratios (0.41±0.05) and significantly lower (p<0.05) food conversion ratios (3.02±0.29). Lysine levels in the whole body increased with increasing levels of supplemented lysine. The dietary requirement of lysine was found to be 4.30% of dietary protein. The crude protein digestibility of six protein sources was investigated. Diets were prepared with 1% chromic oxide as an internal marker. The tested protein sources included low temperature Danish fishmeal, steam dried Chilean fishmeal, blood meal, carcass meal, defatted soyabean meal and Spirulina meal. These potential fishmeal substitutes were selected due to their favourable amino acid profiles, and in particular their high levels of lysine, and their high protein content. Both the animal and the plant protein sources were highly digestible. Digestibility co-efficients ranged from 66.09% for Spirulina meal to 73.38% for low temperature Danish fishmeal. The results have shown that juvenile spotted grunter require a minimum of 40% crude protein in their diet, a P:E ratio of 26.7mg/kJ and a lysine concentration of 4.30% of the dietary protein. Long term growth trials are needed to confirm these results. The hypothesis that the proximate composition of the natural diet, and the proximate composition of the animal under investigation, provides a reliable indication of the animals' nutritional requirements was shown to be valid. Differences between the predicted, and the empirically determined optimal protein and protein:energy ratios were slight.

Thesis (M.S.)--Rhodes University, 2005. / Title from PDF t.p. (viewed on Apr. 15, 2007). Includes bibliographical references (p. 131-152).

Thesis (M. Sc. (Ichthyology and Fisheries Science))--Rhodes University, 2005.

The spotted grunter, Pomodasys commersonnii, has been identified as a candidate species for mariculture in South Africa due to its high market demand and apparent biological suitability for culture. In common with most other potential mariculture species the spotted grunter has an estuarine juvenile phase. In this respect, the difficulties encountered in determining the optimum environmental requirements of spotted grunter are applicable to the majority of other potential mariculture species. Due the variability of estuarine habitats determination of the optimum environmental requirements of estuarine species under laboratory conditions are a prerequisite to subsequent evaluation of aquaculture potential. Therefore, using the spotted grunter as a representative of a typical potent ial mariculture species, the aim of this study was to contribute to the protocol for evaluating the environmental requirements of potential aquaculture species. The growth of fish is dependent on the relationship between food intake, metabolism and environmental factors. In this relationship, environmental factors do not act on growth per se, but rather act through metabolism on growth. Consequently, the environmental factors affecting the growth of a fish species can be classified into functional categories according to their respective influence on metabolic processes. Five functional categories are recognised, namely: controlling, limiting, masking, directive and lethal factors. In this study, the functional categories were sequenced to develop a theoretical protocol for determining the optimum environmental requirements of potential mariculture species under artificial conditions. It was hypothesised that the correct sequence for experimentally determining the optimum environmental requirements of a species should correspond to theoretical protocol. The hypothesis was tested from the experimental investigation into the individual effects of temperature, salinity, light intensity, photoperiod and food intake on growth performance of juvenile spotted grunter. The investigations quantified the relative effects of controlling, masking, directive and limiting factors on growth performance. The results of the studies were statistically compared to obtain a ranking of the effects of the environmental factors (e.g. temperature, salinity, etc.) on growth performance of juvenile spotted grunter. The statistical ranking facilitated the formulation of a second protocol for sequentially determining the optimum environmental requirements of a species. The second protocol was derived purely from the experimental data. Based on the corroboration between the theoretical protocol and that formulated from the experimental investigations, the hypothesis was accepted. Confirmation of the protocol for examining the effects of controlling, limiting, masking and directive factors provided a basis for the development of a preliminary experimental sequence for determining the optimum environmental requirements of juvenile marine fish. In the development of the experimental sequence, the protocol was interpreted in conjunction with the experimental methods used to determine the effects of environmental factors on the growth of juvenile spotted grunter. The experimental sequence provides a logical frame work within which the optimum environmental requirements of other marine fish species can be determined. In addition, evaluation of growth performance by this method provides a basis for comparison of the mariculture potential between species.

Thesis (M.Sc. (Ichthyology & Fisheries Science)) - Rhodes University, 2008.

Thesis (Ph. D. (Ichthyology and Fisheries Science))--Rhodes University, 2006.

Submitted by Alberto Vieira (martins_vieira@ibest.com.br) on 2018-01-12T17:10:42Z No. of bitstreams: 1 566964.pdf: 7932354 bytes, checksum: 40e069b413090587a6fd2cca87f41692 (MD5) / Made available in DSpace on 2018-01-12T17:10:43Z (GMT). No. of bitstreams: 1 566964.pdf: 7932354 bytes, checksum: 40e069b413090587a6fd2cca87f41692 (MD5) Previous issue date: 2002-06-10 / A taxonomia das espécies do gênero Pomadasys Lacépède que ocorrem no Brasil é revista. Das 12 espécies do gênero, ou de seus sinônimos, citadas para o Brasil, apenas as ocorrências de Pomadasys corvinaeformis (Steindachner, 1868) e P. ramosum (Poey, 1860) foram confirmadas com base em material examinado. Uma terceira espécie, identificada tradicionalmente como P. crocro (Cuvier, 1830), revelou-se distinta desta espécie do Mar do Caribe e é aqui reconhecida como nova. A análise do material-tipo de P. crocro da Ilha da Martinica, de exemplares de uma forma similar do Panamá e do material da espécie nova brasileira, sugere tratar-se o grupo crocro de um complexo de espécies alopátricas muito próximas morfologicamente. Problemas relativos a possíveis grupos de espécies em Pomadasys são comentados. Para cada uma das espécies reconhecidas do Brasil são dadas: uma diagnose, descrição, distribuição geográfica com base em material examinado, e dados bio-ecológicos disponíveis. Uma chave de identificação para as espécies brasileiras de Pomadasys é incluída. / The taxonomy of the species of Pomadasys Lacépède from the coast of Brazil is reviewed. Of the 12 species of the genus, or of its synonyms recorded from Brazil, only Pomadasys corvinaeformis (Steindachner, 1868) and P. ramosum (Poey, 1860) were confirmed based on examined material. A third species, traditionally misidentified as P. crocro (Cuvier, 1830), revealed itself distinct from this species of the Caribbean Sea and is herein recognized as new. The study of the type material of P. crocro from Martinica, of specimens from a closely similar form from Panama, and the material of the Brazilian new species suggests that crocro may represent a species-group of allopatric and closely similar species. Problems related to, the existence of species-groups within Pomadasys are discussed. A diagnosis, a brief description, the geographic distribution based on examined specimens, and available information on species bioecology are given for each of the species recognized from Brazil. A key for the identification of the Brazilian species of Pomadasys is given.

Quantitication of stress requires the use of a stress indicator that is easy to measure, and which can be readily interpreted in terms of the potential long-term effects to an organism. This study evaluates the suitability of metabolic rate as an indicator of the stress response in fish. By comparing the metabolic with the cortisol stress response, the most commonly used indicator of stress in fish, it was possible to assess the suitability of metabolic rate as a stress indicator. Changes in metabolic rate were used to predict the long-term effects of transport-related stressors. This study also detennined the baseline metabolic rates of the tish. The standard and the active metabolic rates of juvenile P. cummersonnii were 0.16 ± 0.02 (mean ± S.D, n = 6) mg O₂g⁻¹h⁻¹, and 0.56 ± 0.04 mg O₂g⁻¹h⁻¹, respectively, whereas the routine metabolic rate for the fish was 0.25 ± 0.03 mg O₂g⁻¹h¹. The relationship between metabolic rate and body weight was described by the equation ϺO₂ = 0.64 W⁻°·³⁸. 24-h oxygen consumption measurements showed that juvenile P. commersonnii exhibited diel rhythmicity in oxygen consumption rate, the higher rates occurring at night and the lower rates during the daytime. The higher nocturnal metabolic activity may have been due to increased activity induced by an endogenous rhythm related to feeding. Diel rhythmicity has direct implications for the measurement of baseline metabolic rates since it could result in overestimation or underestimation of these rates. 24-h continuous oxygen consumption measurements enabled the detection of the rhythmicity in oxygen consumption rate, and thereby ensured a greater degree of accuracy in the estimation of these parameters. The metabolic stress response in juvenile P. commersonnii was best described by the equation, y = -0.0013 x² + 0.0364 x ÷ 0.3052, where x = time after application of stressor, and y = oxygen consumption rate. Using the derivative of this equation, the metabolic stress response was estimated to peak approximately 14 min after application of a simulated capture and handling stressor. Oxygen consumption increased by about 300 % as a result of the stress. Approximately 15 min after application of a similar stressor, plasma cortisol levels in stressed fish was 200 % higher than baseline levels. However, cortisol levels in fish sampled 30 min after the disturbance was similar to the baseline cortisol levels, indicating that full recovery had occurred. Although the patterns in the metabolic and cortisol stress responses were similar, metabolic rate could be measured continuously, thereby ensuring accurate interpretation of the data. Furthermore, increases in metabolic rate during the stress response are a culmination of physiological events from the primary to the tertiary levels of biological organization and are, therefore, easier to interpret in terms of long-term effects on the fish. Different transportation procedures elicited variable degrees of stress in juvenile P. commersonnii. The cost of metabolism attributed to the effects of capture and handling was twice as much as that attributed to acute temperature elevation. Acute temperature decrease resulted in a signiticant reduction in the oxygen consumption rate (ANOVA, P < 0.05). Oxygen consumption by the fish was not affected by fish density (ANOVA: F = 2.002, P = 0.5), or by oxygen depletion at dissolved oxygen concentrations above the critical level. Below this level, however, oxygen consumption decreased linearly with further decrease in dissolved oxygen concentration. These results showed that the highest energetic cost to juvenile P. commersonnii was incurred as a result of capture and handling. The results also showed that by subjecting fish to different stressors, it was possible to categorize them according to their relative metabolic costs to the fish. At 25º C, the effective concentration of 2-phenoxyethanol to fully anaesthetize (Stage IV, McFarland 1960) juvenile P. commersonnii was 0.4 ml l⁻¹ and the most appropriate concentration for deep sedation (Stage II, McFarland 1960) of the fish for at least 24 h was 0.2 ml l⁻¹. A maximum of 3 minutes was required by the fish to recover from the effects of the anaesthetic. There was no correlation between fish weight and the rate of induction of anaesthesia (r² = 0.001, p = 0.3). At the peak of the metabolic stress response, oxygen consumption was twice as high in the un-anaesthetized fish compared to the fish anaesthetized after the application of the simulated capture and handling stressor, suggesting that anaesthetization with 2-phenoxyethanol may have reduced the effect of the disturbance on the fish. Similar oxygen consumption rates for the fish anaesthetized prior to capture and the non-stressed fish suggested that the increases in metabolic rate could be linked to the struggling associated with attempts by fish to escape from the perceived stressor. Anaesthetization of juvenile P. commersonnii with 0.3 ml l⁻¹ 2-phenoxyethanol resulted in a more than 200 % increase in plasma cortisol concentration. The elevated levels of plasma cortisol in the anaesthetized fish suggested a manifestation of 2-phenoxyethanol as a stressor. At the time of capture, cortisol levels in fish that were anaesthetized prior to capture were the same as those measured in the disturbed fish at the peak of the stress response (ANOVA, p = 0.95), suggesting that the anaesthetized fish were already experiencing considerable stress at the time they were captured. Undisturbed juvenile P. commersonnii that were anaesthetized for 1 h also had cortisol levels that were five times higher than those measured in undisturbed-unanaesthetized fish, indicating that the duration of exposure to the anaesthetic had a significant effect on plasma cortisol levels. The results presented in this study demonstrate the usefulness of metabolic rate as an indicator of acute stress in fish. This was achieved by comparing the metabolic and the cortisol stress responses. The ease and accuracy with which oxygen consumption of fish could be measured made it possible to measure the stress response more accurately than by plasma cortisol concentration. It was also possible to monitor metabolic rate continuously over a long duration using polarographic oxygen sensors, thus enabling a better evaluation of the stress response. These results, thus, suggest that metabolic rate measurements could be a more practical way to quantify the effects of acute stressors on juvenile fishes. By detailing the profile of the metabolic stress response in P. commersonnii, this study makes a contribution towards understanding the physiological effects of stress in fishes. The study also contributes towards the quantification of baseline metabolic rates of this species under captivity. This study also contributes towards understanding the effects of 2-phenoxyethanol on the stress physiology of fish. By anaesthetizing fish under different conditions of stress, it was possible to evaluate the effect of 2-phenoxyethanol on the metabolic stress response. The ability of 2-phenoxyethanol to reduce physical activity of the fish, and thereby reduce the impact of acute stress on the metabolic stress response, makes it a good agent for the mitigation of stress during the capture and handling of fish. However, the increase in plasma cortisol concentration during prolonged anaesthetization using this drug suggests that the anaesthetic might be a stressor to fish and may, therefore, not be suitable for long-term sedation.

This thesis investigates the movement behaviour of South African two coastal fish species and evaluates the effectiveness of marine protected areas (MPAs) in their protection and management. Its primary focus is on resolving the movement patterns of roman Chrysoblephus laticeps (Sparidae) in and around the Goukamma and Castle Rock MPAs in the Western Cape province of South Africa. A pilot study of the methodology investigated the movement behaviour of spotted grunter Pomadasys commersonnii (Haemulidae) in the sheltered East Kleinmonde Estuary in the Eastern Cape province. The application of different tagging methods was tested in a controlled tank experiment. Tagged roman were monitored over a 198-day period. Barbed dart, t-bar anchor and Visible Implanted Fluorescent Elastomer (VIFE) tags were compared. Application techniques and underwater visibility of VIFE tags were tested on roman and on fransmadam Boobsoidia inornata in a pilot study. Needles of gauge 25 were found to be optimal for VIFE tag application. Whereas VIFE tagging caused fin rot in fransmadam, it had no negative effect on roman. VIFE tagged fish could be identified by divers from a distance of three metres under ambient light in an observation tank in five metres water depth. There was no significant difference in growth rate between groups of roman with different tags and controls after 198 days. High tag loss rates were experienced for barbed dart and t-bar anchor tags, although barbed dart tags performed better than t-bar anchor tags. Although some of the VIFE marks had deteriorated, all VIFE tagged fish were individually recognised at the end of the study. Conventional dart and VIFE tags are feasible methods to tag roman. However, the high tag loss rate of conventional tags must be taken into account in the design of a tagging study. Previous mark and recapture studies on roman are beset with a number of problems. Poor experimental design and low precision of capture positions resulted in equivocal results of limited value. A tagging experiment was designed to eliminate ambiguity in data interpretation and to produce a dataset that could be used to model roman residency and dispersal. A combination of conventional barbed dart tags and Visible Implanted Fluorescent Elastomer tags was used to tag roman in the Goukamma Marine Protected Area (GMPA) on the temperate South African south coast. Sixty one percent of roman were recaptured within 50 m of the tagging position. A small proportion moved considerable distances of up to four kilometres. The extent of these movements was not dependent on fish size or sex. Data from this experiment and from a previous tagging study in the Tsitsikamma National Park (TNP) were used to model the resident behaviour of roman. The model suggests a probability of 91% (GMPA) and 94% (TNP) of residency within a 10000 m² cell. This result suggests that individual roman will benefit from protection in small MPAs. A different experimental approach was required to investigate the exact home range of this species. Firstly the feasibility of using acoustic telemetry to study the movement of coastal fish in South Africa was investigated. The telemetry equipment comprised two VEMCO V8 transmitters and a VEMCO VR60 receiver linked to a directional hydrophone. A tank experiment was conducted to examine the effects of the transmitter implantation. A tracking experiment was conducted on spotted grunter Pomadasys commersonnii in the East Kleinmonde Estuary. Operated fish recovered quickly and, with respect to swimming behaviour and growth rates, no differences were found between fish with implants and controls. The maximum detection range in the estuary was 400 m. Interference between different transmitter frequencies was negligible. Transmitter location recordings were found to be accurate within five metres. Two fish were tracked over a seven-day period. The fish preferred the lower reaches of the estuary where they made repeated and prolonged use of specific areas. The success of the initial experiments allowed this method to be used to investigate the spatial utilisation and activity patterns of roman Chrysoblephus laticeps. Surgically implanted VEMCO V8, V13 and V16 transmitters were used to track 13 roman inside the Castle Rock MPA in False Bay. Transmitters implanted into C. laticeps in tanks had no apparent effects on growth and physiology. Manual boatand diver-based tracking experiments covered a 17-month period. A VEMCO VRAP radio acoustic positioning system was used over two one-month periods during and after the spawning season of roman. Analysis of data using a 95% fixed kernel algorithm suggests that roman are resident throughout their adult life, occupying home ranges between 1000 and 3000 m². Activity was lower at night. During periods of cold-water upwelling, fish retreated into caves. During the spawning season, females extended their home ranges, possibly to mate with different males. These results confirm that this species is well suited for protection and management with small MPAs. The effect of two MPAs on the South African south coast on the population of C. laticeps was simulated with a spatially explicit individual based model (IBM). Life history parameters determined in recent studies and the effect of fishing on the size of sex change was taken into account. Fish densities and size frequencies were based on recent underwater visual census. The distribution of suitable habitat in the study areas was also incorporated. The results show a rapid recovery of the fish size frequency spectrum and sex ratio to pre-exploitation levels inside both MPAs. Little 'spillover' of fish into the fished areas occurred resulting in negligible improvement of catches. The results suggest that for resident species like roman, even small MPAs offer sufficient protection.