This study provides comparative data on the effects of temperature on zygote and alevin survival, rate of development to 50 percent hatching and emergence, and alevin and fry size for five species of Pacific salmon (Oncorhynchus) and for rainbow trout (Salmo gairdneri). Fertilized eggs from each species were incubated in controlled temperature baths at five constant temperatures (2°, 5°, 8°, 11° and 14°C). At 2°C, survival for coho salmon zygotes was high (85 percent), moderate for sockeye salmon zygotes (40 percent) and low for chinook salmon zygotes (4 percent). No pink and chum salmon or rainbow trout zygotes survived at 2°C. However, at 14°C survival for chum salmon and rainbow trout zygotes was high (67 and 85 percent), moderate for chinook and pink salmon zygotes (50 and 55 percent) and low for sockeye salmon zygotes (10 percent). No coho salmon zygotes survived at 14°C. The same general pattern for temperature and survival holds for alevins. These data suggest that coho and sockeye salmon are adapted to lower incubation temperatures than the other species. All six species showed an inverse relationship between temperature and incubation time to 50 percent hatching and emergence. The data were analysed using linear regression but, even after a series of transformations, the relationship between temperature and development time remained curvilinear. The only exceptions were for chum salmon at hatching and pink salmon at emergence. Incubation temperature also influences both alevin and fry size. In general, low incubation temperatures produce larger alevins and fry than high incubation temperatures. In addition to data on constant incubation temperatures, the effects of varying temperature regimes on the survival, rate of development and size of coho salmon and rainbow trout alevins and fry were also documented. Fertilized eggs from coho salmon and rainbow trout were incubated at two varying temperature regimes. The varying temperature regimes either gradually increased from 5° to 14°C (the spring regime) or gradually decreased from 14° to 5°C (the fall regime). The increasing temperature regime produces higher survival in rainbow trout zygotes and alevins than the decreasing temperature regime. However, in coho salmon there was no clear difference in zygote and alevin survival with either regime. The rate of development to hatching for zygotes incubated at either varying temperature regime was similar within a species because of similar mean incubation temperatures between regimes. But, the rate of development to emergence for alevins incubated at either varying temperature regime was different because of different mean temperatures between regimes. The linear regressions to hatching and emergence for coho salmon and rainbow trout were used to predict rates of development for zygotes and alevins incubated with each varying temperature regime. The actual and predicted rates of development to hatching and emergence are similar within a species. Varying temperature regimes also affect both alevin and fry size. The decreasing temperature regime produces larger alevins and fry in coho salmon and rainbow trout than the increasing temperature regime. / Science, Faculty of / Zoology, Department of / Graduate

Life-history traits in fish populations are highly correlated. A subset of these correlations are called allometric scaling, they refer to biological processes which can be described using body size as independent variable. Particularly, allometric scaling related with food consumption (Q) and biomass production (P) has gained the attention of ecologists for several decades. This thesis proposes a quantitative framework for food consumption, which allows both the identification of the mechanisms underlying the allometric scaling for Q and the development of a predictive model for consumption to biomass ratio (Q/B) in fish populations. This thesis is based on the fact that food consumption can be inferred from first principles underlying the von Bertalanffy growth model. In addition, it has been noticed in the literature that biomass production and food consumption show similar allometric scaling dependence, therefore, both can be derived from these first principles. Thus, a similar quantitative framework was used to produce models for P/B in fish populations. Once functional forms for production and food consumption were identified, a third model was developed for the ratio between production and consumption (P/Q). This ratio is usually named ecological efficiency because it determines how efficiently a population can transform ingested food into biomass. Several authors have noticed that P/Q remains invariant (independent of body size) across species. From a theoretical point of view, the results presented here allow the first quantitative explanation for the existence of the allometric scaling for Q/B and the invariance of P/Q across fish species. These results, together with the explanation for allometry in P/B reported in the literature, suggest that the regular across-species pattern for the trio {P/B,Q/B,P/Q} can be explained by basic principles that underpin life-history in fish populations. This quantitative framework for the trio {P/B,Q/B,P/Q} is based on an explicit dependence with body size, which simplifies the estimation of these quantities. Model complexity depends, in part, on which data are available. Models were applied to real data from commercially important species fished in Chile. Statistical properties of the new models were evaluated by an intensive resampling approach. The simplest possible model for the trio {P/B,Q/B,P/Q} rests on the assumption of a stable age distribution. These quantities have a key importance in ecosystem modelling because they determine population energetics in terms of food intake by predation and the transformation of this energy into population biomass of predators. Application of the new models produces results which were comparable to those given by standard methods. This thesis is a result of multidisciplinary research which attempts to make a contribution to the understanding of the mechanisms underlying the allometric scaling of food consumption and production in fish populations. It proposes models for the trio {P/B,Q/B,P/Q} and thus, has the potential to be widely applicable in fisheries science.

Life history allocation of energy to growth and reproduction was determined for female gizzard shad. Absolute caloric energy allocated to eggs increased with age. The relative amount of production energy directed to reproduction increased with age up to 5 years and then decreased. Seasonal variation in lipids was studied. Quantitative changes occurred in ovarian lipids during the reproductive cycle. Carcass lipids varied seasonally. Age of sexual maturity was 3 years. Delayed maturity is attributed to high allocation of energy to growth enabling shad to outgrow intense competition and predation in pre-reproductive ages; there is little competition and predation in reproductive shad. Growth rates and condition factors indicated constant availability of food seasonally.

Diplotaxodon limnothrissa Turner (1995) is a widely distributed species occurring throughout Lake Malawi, extending from the surface to a depth of at least 220m. It is probably the most abundant cichlid in the lake with biomass estimates of around 87 000 tonnes in the pelagic zone alone. The species is exploited commercially in the southern part of the lake but since its inception the fishery has never been assessed. As such this study investigates some aspects of age and growth of the species besides applying a yield-per-recruit analysis to assess the status of the fishery. Analysis of sectioned sagittal otoliths revealed that D. limnothrissa is fast growing and relatively long-lived species, attaining ages in excess of 10 years. Growth in length was rapid in immature fish, with fish attaining almost half of their maximum size within their first year. Le ngth-at-age was described by the von Bertalanffy growth model with combined-sex growth described as Lt = 211.21(1-exp(- 0.24(t+1.36))) mm TL. Total, natural and fishing mortalities were estimated at 0.76 yr⁻¹, 0.31 yr⁻¹ and 0.45 yr⁻¹ respectively. Per-recruit analysis indicated that the D. limnothrissa stock in the southeast arm of the lake is fully exploited as indicated by the current spawner biomass-per-recruit ratios of 31-55% (SB/R)F=0. Modelling indicated that the current age-at-capture (2.67 years) is lower than the age at which yield is optimised (> 5 years) based on the F₀·₁ harvesting strategy. It is, therefore, recommended that the age-at-capture should be increased from 2.67 to 5 years to optimise yield.

Neste trabalho objetivou-se avaliar o desempenho, a composição química do corpo inteiro, a integridade intestinal e a viabilidade econômica de duas linhagens (GIFT e Supreme) de tilápia-do-Nilo (Oreochromis niloticus), alimentadas com duas rações comerciais. O experimento foi conduzido no reservatório da usina de Salto Caxias no Rio Iguaçu, com três repetições em 4 tratamentos. Foram alojados 8500 peixes, em cada gaiola de 18 m³, em novembro de 2014. Os peixes da linhagem Supreme® e GIFT apresentaram peso inicial de 1,27 g e 2,72 g, respectivamente. Aos 50, 101 e 147 dias foram realizadas classificação e biometria dos peixes. Para avaliação do desempenho foram calculados o ganho de peso (GP), a taxa de crescimento específico (TCE) e a conversão alimentar (CA). Ao final do experimento foram coletadas amostras de intestino e posteriormente analisadas sua integridade em microscopia eletrônica de varredura. Durante 147 dias foram anotadas despesas e receitas referentes a produção, para posterior avaliação econômica. Com relação ao GP somente houve diferença significativa entre os peixes que receberam a dieta inicial microextrudada e com prebióticos. A TCE foi maior para os peixes da linhagem SUPREME, nas duas rações. Na curva de crescimento entre as linhagens, foi possível observar que as curvas mantiveram o mesmo padrão sem diferenças acentuadas entre si, porém com maior ganho de peso para os peixes da linhagem GIFT. Na avaliação da composição corporal do peixe inteiro, realizada aos 40, 70 e 116 dias, os peixes não diferiram quanto ao teor de matéria seca, mas houve diferença para a proteína bruta (PB) aos 40 dias, extrato etéreo (EE) e matéria mineral (MM) aos 70 dias entre os peixes que receberam a dieta inicial microextrudada com prebióticos. Entre os peixes que receberam a ração inicial farelada sem prebióticos, houve diferença significativa na PB, no EE e na MM aos 116 dias e o EE também diferiu aos 70 dias.Na análise ultraestrutural do intestino dos peixes que receberam a ração inicial microextrudada com prebióticos foi observada melhor integridade tecidual da mucosa intestinal, entretanto, nos tratamentos com uso da ração inicial farelada sem prebióticos foram observados lesões na mucosa. Na avaliação econômica houve diferença nos custos e receitas. Os peixes da linhagem GIFT alimentados com a dieta microextrudada com prebióticos, apresentaram maior lucratividade, maior valor presente líquido e maior taxa interna de retorno. melhor desempenho econômico, foi possível concluir que a linhagem GIFT, criadas em gaiolas no Rio Iguaçu, foi melhor em relação à linhagem GenoMar Supreme nas duas rações testadas. / This work aimed to evaluate the performance, the chemical composition of the whole body, intestinal integrity and economic viability of two strains (GIFT and Supreme) of Nile tilapia (Oreochromis niloticus) fed two commercial diets. The experiment was conducted in the reservoir of the Salto Caxias plant in the Iguaçu River, with three replicates in 4 treatments. 8500 fish were housed in each cage of 18 m³, a total of 12, in November 2014. The fishes of Supreme® and GIFT strains had initial weight of 1.27 g and 2.72 g, respectively. At 50,101 and 147 days were carried out classification and fish biometrics. For performance evaluation were calculated weight gain (WG), specific growth rate (SGR) and feed conversion (FC). At the end of the experiment intestine samples were collected and analyzed their integrity in scanning electron microscopy. Throughout 147 days were recorded expenses and income related to production for further economic evaluation. Regarding the GP there was only significant difference between the fish that received the initial diet microextrudada and prebiotics.. The SGR was higher for fish SUPREME strain in the two diets. The growth curve between the strains, it was observed that the curves maintained the same pattern with no marked differences between them, but with greater weight gain for the fish of the GIFT strain. The assessment of body composition of whole fish, held on 40, 70 and 116 days, the fish did not differ for dry matter content, but there was difference for crude protein at 40 days, ether extract and mineral matter 70 days between the fish that received the initial microextruded diet with prebiotics. Among the fish that received the initial mash diet without prebiotics, there was significant difference in crude protein, ether extract and mineral content at 116 days and the ether extract also differed at 70 days. In ultrastructural analysis of the fish intestine that received the initial microextruded feed with prebiotics was observed better tissue integrity of the intestinal mucosa, however, the treatments with use of initial mash diet without prebiotics lesions were observed in the mucosa and the presence of large number of attached microorganisms to mucosa. In the economic assessment was no difference in costs and revenues.Fish of the GIFT strain fed microextrudada diet additives, showed higher profitability, higher net present value (NPV) and higher internal rate of return (IRR). Excelling in higher growth and better economic performance, it was concluded that the GIFT strain, caged in the Iguaçu River, was better about GenoMar Supreme strain on both diets studied.

The South African mariculture industry is developing the rearing technology of indigenous fish species. Dusky kob (Argyrosomus japonicus) has high-quality flesh and a good market demand. Research is needed to determine the environmental requirements under which growth of dusky kob is optimised. This study assessed the effect of temperature, light intensity, feeding frequency and stocking density, respectively, on growth, feed conversion ratio (FCR) and survival of juvenile dusky kob within a weight range of 10-60 g fish⁻¹) in a series of four growth trials. The effect of temperature on growth and FCR was assessed at 14 temperatures from 17 to 28°C. The temperature for best growth was estimated to be 25.3 °C, while 21.4 °C was the temperature at which the best FCR was achieved. A growth trial testing the effect of light intensity on growth showed that light intensity did not affect growth in the range of 23 – 315 lx. Fish fed a restricted ration of 3.6% body weight per day (chapter 2) or 3.41% body weight per day (chapter 4) had a better FCR than fish fed to satiation. A trial to assess the effect of feeding frequency on growth and FCR showed that fish fed both two or three times daily grew better than those fed once daily. FCR was best in fish that were fed once or twice daily. Preliminary analysis of the results from a stocking density trial showed that stocking density in the range of 10 – 50 kg m⁻³ did not affect growth of juvenile dusky kob. It is recommended to culture dusky kob at a temperature of 25.3 - 21.4 °C at stocking densities up 50 kg m⁻³ to maximise growth. However, a study is needed to determine the environmental conditions needed to maximise profit under commercial conditions. The results allow the South African industry the opportunity to assess the culture potential of this species. In addition, the results will help develop protocols that can be used in other South African candidate aquaculture species such as silver kob, yellowtail, white-stumpnose and sole.

In the present study, the ease of rearing, short generation time and molecular research tools available for the zebrafish model (Danio rerio, Hamilton) were exploited to investigate transcriptional regulation in relation to feeding, photoperiod and experimental selection. Chapter 2 describes transcriptional regulation in fast skeletal muscle following fasting and a single satiating meal of bloodworms. Changes in transcript abundance were investigated in relation to the food content in the gut. Using qPCR, the transcription patterns of 16 genes comprising the insulin-like growth factor (IGF) system were characterized, and differential regulation between some of the paralogues was recorded. For example, feeding was associated with upregulation of igf1a and igf2b at 3 and 6h after the single-meal was offered, respectively, whereas igf1b was not detected in skeletal muscle. On the other hand, fasting triggered the upregulation of the igf1 receptors and igfbp1a/b, the only binding proteins whose transcription was responsive to a single-satiating meal. In addition to the investigation of the IGF-axis, an agnostic approach was used to discover other genes involved in transcriptional response to nutritional status, by employing a whole-genome microarray containing 44K probes. This resulted in the discovery of 147 genes in skeletal muscle that were differentially expressed between fasting and satiation. Ubiquitin-ligases involved in proteasome-mediated protein degradation, and antiproliferative and pro-apoptotic genes were among the genes upregulated during fasting, whereas satiation resulted in an upregulation of genes involved in protein synthesis and folding, and a gene highly correlated with growth in mice and fish, the enzyme ornithine decarboxylase 1. Zebrafish exhibit circadian rhythms of breeding, locomotor activity and feeding that are controlled by molecular clock mechanisms in central and peripheral organs. In chapter 3 the transcription of 17 known clock genes was investigated in skeletal muscle in relation to the photoperiod and food content in the gut. The hypothesis that myogenic regulatory factors and components of the IGF-pathway were clock-controlled was also tested. Positive (clock1 and bmal1 paralogues) and negative oscillators (cry1a and per genes) showed a strong circadian pattern in skeletal muscle in anti-phase with each other. MyoD was not clock-controlled in zebrafish in contrast to findings in mice, whereas myf6 showed a circadian pattern of expression in phase with clock and bmal. Similarly, the expression of two IGF binding proteins (igfbp3 and 5b) was circadian and in phase with the positive oscillators clock and bmal. It was also found that some paralogues responded differently to photoperiod. For example, clock1a was 3-fold more responsive than clock1b. Cry1b did not show a circadian pattern of expression. These patterns of expression provide evidence that the molecular clock mechanisms in skeletal muscle are synchronized with the molecular clock in central pacemaker organs such as eyes and the pineal gland. Using the short generation time of zebrafish the effects of selective breeding for body size at age were investigated and are described in chapter 4. Three rounds of artificial selection for small (S-lineage) and large body size (L-lineage) resulted in zebrafish populations whose average standard length were, respectively, 2% lower and 10% higher than an unselected control lineage (U-lineage). Fish from the L-lineage showed an increased egg production and bigger egg size with more yolk, possibly contributing to the larger body size observed in the early larval stage (6dpf) of fish from this lineage. Fish from S- and L-lineage exposed to fasting and refeeding showed very similar feed intake, providing evidence that experimental selection did not cause significant changes in appetite control. Investigation of the expression of the IGF-axis and nutritionally-response in skeletal muscle after fasting and refeeding revealed that the pattern of expression was not different between the selected lineages, but that a differential responsiveness was observed in a limited number of genes, providing evidence that experimental selection might have changed the way fish allocate the energy acquired through feeding. For example, a constitutive higher expression of igf1a was recorded in skeletal muscle of fish from the L-lineage whereas igfbp1a/b transcripts were higher in muscle of fish from the S-lineage. These findings demonstrate the rapid changes in growth and transcriptional response in skeletal muscle of zebrafish after only three rounds of selection. Furthermore, it provides evidences that differences in growth during embryonic and larval stages might be related to higher levels of energy deposited during oogenesis, whereas differences in adult fish were better explained by changes in energy allocation instead of energy acquisition. In chapter 5 the main findings made during this study and their impact on the literature are discussed.

The ichthyofaunal community structure, population dynamics and movement patterns in the small temporarily open/closed (TOCE) Grant’s Valley estuary, situated along the Eastern Cape coastline, were investigated over the period May 2004 to April 2005. Community structure in the littoral zone was assessed, while growth of selected ichthyofaunal species was investigated using the MULTIFAN model. Population size was assessed using mark recapture models and movement within the estuary using the Hilborn (1990) model. Total ichthyofaunal densities and biomass within the littoral zone ranged between 0.31 to 21.45 fish m⁻² and 0.20 to 4.67 g wwt m⁻², with the highest values typically recorded during the summer. Results of the study indicated that the ichthyofaunal community structure within the estuary was closely linked to the mouth phase and the establishment of a link to the marine environment via overtopping events. In the absence of any link to the sea, the ichthyofaunal community was numerically dominated by estuarine resident species, mainly Gilchristella aestuaria and to a lesser extent, by the river goby, Glossogobius callidus which collectively comprised ca. 88% of all fish sampled. The establishment of the link to the marine environment contributed to an increased contribution of marine breeding species (e.g. Rhabdosargus holubi, Myxus capensis and Atherina breviceps) to the total ichthyofaunal abundances. In contrast, total ichthyofaunal biomass was almost always dominated by marine breeding species by virtue of their larger sizes. Results of hierarchical cluster analyses did not identify any spatial patterns in the ichthyofaunal community within the littoral zone. Results of MULTIFAN analysis indicated estuarine resident fish species bred over an extended period with peaks occurring in the summer months. Conversely, marine breeding fish were shown to recruit into the estuary following overtopping and breaching events. Results of the mark-recapture experiment indicated a population of ca. 12 000 (11 219 – 13 311) individuals greater than 50mm SL. Marine-breeding species (R. holubi, Monodactylus falciformis, and two mullet species) numerically dominated the ichthyofauna, possibly as a result of their effective use of overtopping events. The two mullet species, M. capensis and Liza richardsonii, and the Cape stumpnose, R. holubi moved extensively throughout the estuary, while the remaining species exhibited restricted movement patterns possibly due to the preference for refuge and foraging areas associated with reed beds. The observed movement patterns of individual fish species appeared to be associated with both foraging behaviour and habitat selection.

Patagonian toothfish (Dissostichus eleginoides) or "Chilean sea bass" support a valuable and controversial fishery, but the life history is little known and longevity estimates range from ~20 to more than 40 or 50 yr. In this study, lead-radium dating provided validated age estimates from juveniles to older adults, supporting the use of otoliths as accurate indicators of age. The oldest age groups were near 30 yr, which provided support for age estimates exceeding 40 or 50 yr from grow zone counts in otolith sections. Hence, scale reading, which rarely exceeds 20 years, has the potential for age underestimation. Lead-radium dating revealed what may be minor differences in age interpretation between two facilities and findings may provide an age-validated opportunity for the CCAMLR Otolith Network to reassess otolith interpretations. Orange roughy (Hoplostethus atlanticus) support a major deep-sea fishery and stock assessments often depend on age analyses, but lifespan estimates range from ~20 to over 100 yr and validation of growth zone counts remained unresolved. An early application of lead-radium dating supported centenarian ages, but the findings were met with disbelief and some studies have attempted to discredit the technique and the long lifespan. In this study, an improved lead-radium dating technique used smaller samples than previously possible and circumvented assumptions that were previously necessary. Lead-radium dating of otolith cores, the first few years of growth, provided ratios that correlated well with the ingrowth curve. This provided robust support for age estimates from otolith thin sections. Use of radiometric ages as independent age estimates indicated the fish in the oldest group were at least 93 yr. Lead-radium dating has validated a centenarian lifespan for orange roughy. To date, radium-226 has been measured in otoliths of 39 fish species ranging from the northern Pacific and Atlantic Oceans to the Southern Ocean. In total, 367 reliable radium-226 measurements were made in 36 studies since the first lead-radium dating study on fish in 1982. The activity of radium-226 measurements ranged over 3 orders of magnitude (<0.001 to >1.0 dpm.g⁻¹). An analysis revealed ontogenetic differences in radium-226 uptake that may be attributed to changes in habitat or diet. Radiometric age from otolith core studies was used to describe a radium-226 uptake time-series for some species, which revealed interesting patterns over long periods. This synopsis provides information on the uptake of radium-226 to otoliths from an environmental perspective, which can be used as a basis for future studies.