Aquaculture methods are limited for white crappie (Pomoxis annularis), reducing production potential. Therefore, reproduction methods, including induced spawning, sperm cryopreservation and out-of-season spawning, were developed in tank systems. A two week acclimation period (15°C; 3-5 ppt salinity) was necessary to reduce disease-related mortality. Afterwards, four spawning induction hormones and a control were examined to induce spawning. Luteinizing hormone releasing hormone analogue and salmonid gonadotropin releasing hormone analogue performed the best in terms of spawning success and %ertilization. Sperm cryopreservation was effective using Hanks or Ca2+ree Hanks balanced salt solutions with 10%-methanol or 5%-dimethyl-sulfoxide as a cryoprotectant, frozen at 40°C/min. Out-of-season spawning experiments manipulated photoperiod and temperature over 3-wk (9% spawning success; 11% fertilization) and 6-wk (16% spawning success; 55% fertilization) seasonal shifts. Post-experiment maturation data indicate that females were in an intermediate development stage. These experiments demonstrate the potential of advanced spawning techniques to improve annual production of white crappie.

Relying on field research to complete the life history for certain fish species can be inadequate, but laboratory research can be used to fill these gaps. These gaps exist for Bonefish (Albula spp.), a tropical marine fish and popular sportfish. In this study, aquaculture techniques were applied to Bonefish in a captive setting at Harbor Branch Oceanographic Institute (HBOI) and Cape Eleuthera Institute (CEI) to induce spawning and describe early ontogeny. Photothermal manipulations and hormone injections were used to induce gonad maturation and spawning, which was achieved once at CEI and is the first record of hormone-induced spawning for Bonefish. From that spawn, egg and larval development were recorded and described through 26 hours and 56 hours respectively, representing the first record of these early life stages for Bonefish. This work expands upon what is known about Bonefish reproductive biology and will be useful for management and future captive research. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection

Resumo: Estudos têm revelado que a planta Aloe vera possui muitas substâncias com propriedades farmacêuticas tais como ação cicatrizante, imuno-estimulante, fungicida entre outras. O uso de seu extrato pode ser eficiente no tratamento de problemas advindos do manejo na piscicultura, como no transporte, onde ocorrem injúrias e quadro de estresse com imunossupressão. O presente trabalho avaliou os efeitos da Aloe vera adicionada na água no transporte de juvenis de matrinxã (Brycon amazonicus) em indicadores hematológicos, metabólico e imunológico. Após 48 horas de jejum, peixes foram transportados em diferentes concentrações de Aloe vera (0%; 0,002%; 0,02% e 0,2%) e amostrados antes do transporte (nível inicial - n=8), às 2 horas de transporte (n=10), após 4 horas (na chegada - n=8), 24 e 96 horas depois do transporte (período de recuperação - n=8). Após o transporte, os peixes foram distribuídos, conforme o tratamento, em quatro caixas de 1.000 litros, com fluxo contínuo de água. No sangue total foram determinados o hematócrito, número e volume de eritrócitos, concentração de hemoglobina e atividade respiratória de leucócitos, e no plasma a concentração de glicose. Os resultados hematológicos não apresentaram padrão consistente. A glicemia aumentou após duas e quatro horas de transporte nos peixes de todos os tratamentos, sem diferença entre eles, e voltou aos valores iniciais (pré-transporte) 24 e 96 horas pós transporte. Na atividade respiratória dos macrófagos houve um aumento em duas horas de transporte nos peixes expostos à Aloe vera. A Aloe vera também aumentou a atividade respiratória dos macrófagos in vitro, provando assim sua ação imunoestimulante. Os resultados indicam que a adição de Aloe vera na água de transporte não afetou as respostas metabólica e hematológicas, mas potenciou a resposta imunológica não específica / Abstract: Aloe vera has many substances with pharmaceutical properties such as wound healer, immunostimulant, fungicide and others. The use of its extract can be effective in the treatment of problems caused by the handling of fish, such as in the transport, when injuries occur, and the stress can reduce immune responses of fish. This study evaluated the effects of Aloe vera added to the water in the transport of juvenile matrinxã (Brycon amazonicus) in hematological, metabolic and immune indicators. After 48 hours of fasting, fish were transported in different concentrations of Aloe vera (0%, 0.002%, 0.02% and 0.2%) and sampled before transport (initial - n = 8) at 2 hours of transport (n = 10), and 4 hours (arrival - n = 8), 24 and 96 hours after the procedure (recovery - n = 8). At arrival, fish were distributed, according to the treatment, in four tanks of 1.000 l, with a continuous water flow. Fish blood was drawn and hematocrit, number and volume of erythrocytes, hemoglobin, respiratory activity of leukocytes, and glucose concentration were determined. The results did not show any consistent pattern in hematological indicators. Plasma glucose concentration increased after 2 and 4 hours of transport in fish of all treatments, without difference among them, and returned to basal amount in 24 and 96 hours after transport. The respiratory activity of macrophages increased within 2 hours of transport in fish exposed to Aloe vera. Aloe vera also increased the respiratory activity of macrophages in vitro, reinforcing its stimulanting effect. The results indicate that the addition of Aloe vera in water transport did not affect the metabolic and hematological indicators, but enhanced the nonspecific immune response tested / Orientador: Elisabeth Criscuolo Urbinati / Coorientador: Sérgio Fonseca Zaiden / Banca: José Augusto Senhorini / Banca: Paulo Sérgio Ceccarelli / Mestre

Made available in DSpace on 2014-06-11T19:22:23Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-01-18Bitstream added on 2014-06-13T18:49:01Z : No. of bitstreams: 1 zanuzzo_fs_me_jabo.pdf: 2445483 bytes, checksum: f930eca53aee743247786a998c37fbfd (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Universidade Estadual Paulista (UNESP) / Estudos têm revelado que a planta Aloe vera possui muitas substâncias com propriedades farmacêuticas tais como ação cicatrizante, imuno-estimulante, fungicida entre outras. O uso de seu extrato pode ser eficiente no tratamento de problemas advindos do manejo na piscicultura, como no transporte, onde ocorrem injúrias e quadro de estresse com imunossupressão. O presente trabalho avaliou os efeitos da Aloe vera adicionada na água no transporte de juvenis de matrinxã (Brycon amazonicus) em indicadores hematológicos, metabólico e imunológico. Após 48 horas de jejum, peixes foram transportados em diferentes concentrações de Aloe vera (0%; 0,002%; 0,02% e 0,2%) e amostrados antes do transporte (nível inicial – n=8), às 2 horas de transporte (n=10), após 4 horas (na chegada – n=8), 24 e 96 horas depois do transporte (período de recuperação – n=8). Após o transporte, os peixes foram distribuídos, conforme o tratamento, em quatro caixas de 1.000 litros, com fluxo contínuo de água. No sangue total foram determinados o hematócrito, número e volume de eritrócitos, concentração de hemoglobina e atividade respiratória de leucócitos, e no plasma a concentração de glicose. Os resultados hematológicos não apresentaram padrão consistente. A glicemia aumentou após duas e quatro horas de transporte nos peixes de todos os tratamentos, sem diferença entre eles, e voltou aos valores iniciais (pré-transporte) 24 e 96 horas pós transporte. Na atividade respiratória dos macrófagos houve um aumento em duas horas de transporte nos peixes expostos à Aloe vera. A Aloe vera também aumentou a atividade respiratória dos macrófagos in vitro, provando assim sua ação imunoestimulante. Os resultados indicam que a adição de Aloe vera na água de transporte não afetou as respostas metabólica e hematológicas, mas potenciou a resposta imunológica não específica / Aloe vera has many substances with pharmaceutical properties such as wound healer, immunostimulant, fungicide and others. The use of its extract can be effective in the treatment of problems caused by the handling of fish, such as in the transport, when injuries occur, and the stress can reduce immune responses of fish. This study evaluated the effects of Aloe vera added to the water in the transport of juvenile matrinxã (Brycon amazonicus) in hematological, metabolic and immune indicators. After 48 hours of fasting, fish were transported in different concentrations of Aloe vera (0%, 0.002%, 0.02% and 0.2%) and sampled before transport (initial - n = 8) at 2 hours of transport (n = 10), and 4 hours (arrival - n = 8), 24 and 96 hours after the procedure (recovery - n = 8). At arrival, fish were distributed, according to the treatment, in four tanks of 1.000 l, with a continuous water flow. Fish blood was drawn and hematocrit, number and volume of erythrocytes, hemoglobin, respiratory activity of leukocytes, and glucose concentration were determined. The results did not show any consistent pattern in hematological indicators. Plasma glucose concentration increased after 2 and 4 hours of transport in fish of all treatments, without difference among them, and returned to basal amount in 24 and 96 hours after transport. The respiratory activity of macrophages increased within 2 hours of transport in fish exposed to Aloe vera. Aloe vera also increased the respiratory activity of macrophages in vitro, reinforcing its stimulanting effect. The results indicate that the addition of Aloe vera in water transport did not affect the metabolic and hematological indicators, but enhanced the nonspecific immune response tested

Cardinal tetras, Paracheirodon axelrodi (Pisces: Characidae), are among the most popular tropical ornamental fish in the world. Millions of cardinal tetras are removed from their natural habitat, the upper tributaries of the Rio Negro in Brazil, each year and exported to North America and Europe where they are abundantly available at low cost. This, combined with the fact that they do not spawn freely in captivity has excluded any incentive to culture this fish on a commercial scale in these areas. However, the demand for cardinal tetras in South Africa is high, but their availability is limited to sporadic imports of wild caught fish which has resulted in an increase in their relative value. Thus, there is an appreciable incentive to investigate methods for inducing this species to reproduce in captivity. Information on methods for inducing spawning would form an integral part of a potential production plan for the culture of this species in South Africa. This study consisted of a number of experiments designed to investigate factors related to the spawning of cardinal tetras in captivity. The first series of experiments investigated the effect of variables such as the water chemistry of the experimental system, the sex ratio of the fish, the effect of conditioning and the effect of different spawning media on spawning success. The second series of experiments tested the effects of various environmental stimuli or hormonal treatments on spawning in cardinal tetras. Environmental stimuli tested included a rise in temperature, a rise in water level and a fresh rain water flush. Hormonal treatments included feeding GnRHa enriched brine shrimps to the fish or the application of hormone injections (hypophysation). Neither environmental stimuli nor brine shrimp enrichment induced cardinals to spawn in a repeatable manner. The same was true for hypophysation, but in this case a low incedence of ovulation of injected females was observed. Oocytes from ovulated and non-ovulated females were examined under a microscope and from this it was determined that cardinal tetras are group synchronous spawners, containing two distinct cohorts of oocytes in the ovary. The effect of a number of environmental stimuli on ovulation rate in cardinal tetras were then tested but did not induce ovulation in any females. A series of three experiments was performed investigating the effect of conditioning the sexes together on ovulation rate and spawning success. Conditioning the sexes together had no effect on spawning success, but a significantly higher ovulation rate was observed in females that vvere conditioned together with males. Male cardinals did not follow this trend and lost condition when conditioned together with females. The next experiment tested if pheromones from red serpae tetras, Hyphessobrycon serpae, could be used to induce ovulation and spawning in cardinal tetras. This was found not to be the case. The final series of experiments tested the effect of Aquaspawn® enriched Artemia on ovulation rates in female cardinal tetras. Aquaspawn® is a water soluble preparation of GnRHa and dopamine. Aquaspawn® enriched Artemia were found to be effective for inducing female cardinal tetras to ovulate. However, the results from this method of enrichment were not entirely reliable and further research is warranted. Finally, a protocol for evaluating spawning in topical, freshwater egg-laying fish was proposed, based on the results from this study. The advantages and disadvantages of such a protocol were discussed.

This thesis was partitioned into three studies. In the first study, striped bass, Morone saxatilis, (n = 16) were monitored over a 13 month period to examine the efficacy of ultrasound to determine sex and to monitor sexual maturation. Four observers reviewed all ultrasound images (n = 208) of striped bass and were able to sex male and female striped bass with 99 and 95% accuracy, respectively throughout an annual reproductive cycle. Egg diameter was highly correlated with average (r = 0.89) and maximum (r=0.92) ovarian diameter as measured by ultrasound. Spenniating males exhibited larger maximum testicular diameters (23.5 mm) than non-spermiating males (13.1 mm). Fully mature female and male striped bass exhibited maximum ovarian diameters > 30 mm and testicular diameters > 20 mm as measured by ultrasound. The results of this study indicate that ultrasound is an effective and non-invasive method that aquaculturists can use to quickly scan, sex, and assess the sexual maturation of adult male and female striped bass year-round. In the second study, photothennal manipulation was used to induce spawning out-of season and to increase the frequency of spawning in striped bass, Morone saxatilis. Forty adult striped bass, held in five environmental chambers, were exposed to compressed 6- and 9- month cycles and a 12-month reference cycle. Maximum egg diameters increased with cycle length, averaging 845 urn, 946 urn, and 1,073 um for females held on the 6-, 9-, and 12-month cycles,respectively. Females held on the 6-month cycle had smaller ovarian diameters (19.6 mm) than those held on the 9-month (27.4 mm) and 12-month (24.5 mm) cycles. Ovary diameter was highly correlated with egg diameter (r = 0.91). Spawning success (percent of females spawning) increased with cycle length, averaging 38%, 86%, and 100% in the 6-, 9-, and 12-month cycles, respectively. However, no differences in latent times, fecundity, or fertility were detected between cycles or between tank-spawned and strip-spawned females. Males held on the 6-month cycle had smaller testicular diameters (16.2 mm) than those held on 9-month (23.6 mm) and 12-month (19.2 mm) cycles. Testicular diameter of spenniating males (15.7 mm) was significantly larger than that of non-spenniating males (6.9 rnrn) in all cycles. Mortality increased with cycle length, averaging 28%, 38%, and 88% for fish held on the 6-, 9-, and 12-month cycles, respectively. Maturation and spawning were advanced by five and three months for fish held in the 6- and 9-month cycles, respectively when compared to a natural 12-month reference cycle. Fish held on the 6-month cycle matured twice within a year. However, the relatively low number of spawning females and diminished egg, ovarian, and testicular diameter of fish held on the 6-month cycle suggest that an abbreviated cycle length « 9 months) may inhibit maturation and constrain spawning success. / Master of Science

Advances in aquaculture technologies are being investigated to support the replenishment of local fisheries, develop marine food fish farming opportunities and to increase seafood production globally. In order to promote the expansion and development of aquaculture technologies required to raise new finfish species, a number of key bottlenecks restricting commercial-scale culture need to be addressed, including the ability to control fish reproduction in captivity and to produce high quality seeds. One candidate species for large-scale production, and the focus of this work, is common snook. Prized as a food fish in Mexico, Central and South America and as a popular game fish along the Gulf coast of the United States; common snook are economically important having both a high market value and recreational demand. Despite recent advances in captive spawning, a number of reproductive bottlenecks still need to be addressed such as lack of spontaneous spawning in captivity, poor fertilization rates and inconsistent production of high quality eggs and larvae. Therefore, the overall aim of this thesis was to better understand the reproductive biology of common snook in order to develop protocols to improve the reliability of captive spawning in closed recirculating aquaculture systems and the quality of eggs produced as a basis for commercial scale cultivation. First, this PhD project described oocyte development in common snook and validated a non-invasive method for assessing reproductive condition in wild and captive stocks (Chapter 2). This was done by using a tiered and adaptable staging scheme to compare the wet mount technique with histological preparations of ovarian biopsies. When compared with histology, the wet mount provided an immediate and precise method for determining whether female broodstock were candidates for hormonal induction. In fishery biology, an understanding of fish reproductive success and population reproductive potential is critical for designing and implementing effective fisheries management strategies. The wet mount technique provides a tool for non-lethal, low-cost determination of reproductive status in wild fish stocks. The next research chapter focused on spawning induction of captive snook populations. The first trial compared the effects of slow and regular release GnRHa implants whereas the second trial investigated the effects of GnRHa, alone or in combination with the dopamine antagonist, pimozide (PIM), on milt characteristics and plasma steroid levels in captive male common snook broodstock (Chapter 3). In an effort to better enable reliable control of reproduction under captive conditions, the annual plasma sex steroid profile of captive male and female broodstock maintained under natural photo-thermal conditions was also examined. When possible, milt samples were collected pre and post implantation; sperm density, sperm motility and spermatocrit were documented among individual males. The assigned treatments appeared to have no or little effects on milt production in male broodstock although plasma steroid levels were found to be significantly elevated in individuals treated with GnRHa in combination with the dopamine antagonist, pimozide. At the time this work was performed, no data on spawning dynamics, including individual spawning performance, had been reported for common snook in captivity. Mass spawning tanks are complex systems where fish are left to spawn naturally and fertilized eggs are collected with little or no control over the mating of the animals. Therefore, the third part of this thesis explored the potential of DNA profiling for monitoring mating outcomes in captive broodstock by employing eight microsatellite markers to detect and quantify individual parental contributions for 2,154 larvae obtained from the three broodstock tanks (Chapter 4). The panel of loci was generally robust and allowed unambiguous assignment of 89% of larvae to a single family. Overall, spawn contribution data 1) provided a confirmation of GnRHa treatment efficacy in female snook with a minimum stage of oogenesis (late secondary growth-SGl) required for successful spawning, 2) identified a potential impact of handling on maturation and spawning of captive broodstock and 3) confirmed that, through photothermal conditioning, captive broodstock can spawn over consecutive days and several times per year including outside of their natural spawning season. The exogenous cues that tropical species use to synchronize key life events like reproduction remain largely unstudied, therefore, my PhD project also investigated the influence of tidal cycle on reproductive activity in common snook (Chapter 5). Real-time quantitative RT-PCR assays were developed and validated to measure the temporal expression patterns of gonadotropin genes (fshβ and lhβ) during the reproductive cycle in males and females. These were evaluated in relation to sex steroid production, LH blood plasma levels, gonadal development and tidal cycle. The phylogenetic analysis of the deduced amino acid sequence of common snook for fshβ and lhβ revealed strong identity with other teleosts (75-90%). Additionally, the mRNA profiles of fshβ and lhβ in the pituitary of females displayed a clear pattern of expression concomitant with histological changes in oocyte development. Histological observations of gonads suggested a circa-tidal rhythm of follicular development. The findings, as a whole, provided new information supporting the role of tidal cycle on the entrainment of gametogenesis allowing for a better understanding of the environmental control of reproduction in common snook. Although the primary research emphasis in this PhD was on broodstock spawning and gamete quality, the final chapter focuses on larval ontogeny. The goal of this research was to gain improve understanding of the early life history characteristics of common snook in order to improve larval culture technologies. To do so, a combination of digital photography and histological techniques were used to document the embryonic and early larval development (0 to 14 days post hatch-DPH) of hatchery-reared individuals (Chapter 6). Larvae hatched 15 h after fertilization at 28°C, lacked pigmentation, had a rudimentary digestive tract and undeveloped visual system. Development was rapid and by 3 DPH larvae had almost doubled in length, the yolk sac was nearly exhausted, the mouth was open and eyes were pigmented with a well-structured retinal layer. The alimentary canal was differentiated into three distinct sections including the foregut, midgut and hindgut. Food was observed in the gut (rotifers) and structural epithelium organelles, such as the nucleus, mitochondria, and dark vesicles, were all present in high numbers. The swim bladder was formed and inflated. In summary, understanding early ontogenetic development in common snook can help provide information needed to address key bottlenecks seen in captive cultivation, such as the high incidence of larval mortality observed during the transition from endogenous to exogenous feeding. Overall, this doctoral work 1) validated molecular and endocrine analytical tools for future studies of common snook reproductive physiology, 2) provided a better understanding of both broodfish requirements in tank systems as well as the endocrine control of reproduction and spawning at the level of the brain-pituitary-gonadal axis, 3) increased our knowledge in genetic management of captive broodstock, in terms of parentage assignment and 4) offered new insight into wild population reproductive strategy as well as how reproduction is entrained through environmental cues and the pathways leading to oocyte recruitment and maturation. The new information presented here can be used to conserve wild snook stocks through production of farm raised individuals as a sustainable source of seafood and for fisheries enhancement.

Made available in DSpace on 2015-03-26T13:46:34Z (GMT). No. of bitstreams: 1 texto completo.pdf: 2071717 bytes, checksum: 2b2b2db684156dc843d94182ee1a1075 (MD5) Previous issue date: 2008-02-21 / Fundação de Amparo a Pesquisa do Estado de Minas Gerais / Astyanax bimaculatus, oviparous fish, presents reproductive activity the year round and multiple spawning. It is important to know the reproductive biology to facilitate the reproductive management, minimize the expenses with the reproduction and develop new techniques that can to improve the reproduction with commercial and preservation interests. Studies demonstrate the importance of the growth hormone in the gametogenesis and gonadal ripening, as being an important factor of female reproduction. In this way, the present study histologically evaluates the Astyanax bimaculatus ovaries submitted to the induced spawning technique with a crude carp pituitary extract and the effect of the growth hormone in the ovarian recrudescence process after spawning. Respecting the different periods after induced spawning, the ovaries of fishes of the control group and the growth hormone treated group were analyzed using a light microscope, aiming to characterize the post-spawning ovarian morphology. From the biometric data obtained, the gonadossomatic index (GSI) and hepatossomatic index (HSI) values were calculated, and also the condition factor (K2), in the different collection schedules for the two groups under study. Around 60% of the females reacted satisfactorily to the crude carp pituitary extract injection. The extrusion of the oocytes occurred between 225 and 234 h-degrees after hypophysation. The oogenesis of A. bimaculatus seems to be similar to the majority of the fresh water teleosts. The analysis of the fragments of ovaries showed the constant presence of oocytes in the gonads during all pphases of development, post-ovulatory follicles, besides follicular atresia. Oocyte in primary growth were present in great number in the group-control, while oocytes in secondary growth were more numerous in the treated group. Post- ovulatory follicles were more numerous in the control group than in the treated group, and between 96th and 120th hours after spawning in both control group and treated group its detection became more difficult. The follicular atresia was observed in greater intensity in the treated group than in the control group. Significant differences (P<0.05) between the experimental were recorded at six and at 48th hours after spawning. Significant differences were not observed (P>0.05) for the eosinophyle counting inside the experimental groups. A greater quantity of eosinophyles was observed in the treated group, coinciding with the largest quantities of atretic follicles in this group. A significant difference (P<0.05) was noticed when the follicular atresia and eosinophyle values were associated and compared between the experimental groups. Due to a multiple spawning and not presenting abrupt variations in the size of the gonads, significant differences were not found (P>0.05) for the GSI in the different collecting periods and not even between the experimental groups. Statistical differences (P<0.05) for the HSI values were found between the experimental groups at the nine and 96 th hours postspawning. Higher values of HSI were registered in the group that received the hormone growth coinciding with the largest quantity of vitelogenesis oocyte observed in this group. Statistical differences were not found (P>0.05) for the condition factor (K2). / Astyanax bimaculatus, peixe ovíparo, apresenta atividade reprodutiva o ano todo e desova parcelada, características promissoras para seu cultivo. É importante conhecer a biologia reprodutiva para facilitar o manejo, minimizar os gastos com a reprodução e desenvolver novas técnicas para aprimorar a reprodução com interesse comercial e de preservação. Estudos demonstram a importância do hormônio de crescimento nos processos de gametogênese e maturação gonadal, sendo um importante modulador da reprodução da fêmea. O presente trabalho avalia histologicamente os ovários de lambaris submetidos à técnica de desova induzida com extrato bruto de hipófise de carpa, e o efeito do hormônio de crescimento no processo de recuperação ovariana após a desova. Após a desova induzida, ovários de peixes do grupo- controle e do grupo tratado com hormônio de crescimento foram analisados em microscopia de luz, visando caracterizar a morfologia ovariana pós-desova. A partir de dados biométricos obtidos, foram calculados os valores dos índices gonadossomático (IGS) e hepatossomático (IHS), e do fator de condição K2 nos diferentes horários de coleta para os grupos em estudo. Cerca de 60% das fêmeas hipofisadas responderam satisfatoriamente à injeção do extrato bruto de hipófise. A extrusão dos ovócitos ocorreu entre 225 a 234 horas-grau após hipofisação. A ovogenêse de A. bimaculatus parece ser similar à maioria dos teleósteos de água doce. A análise dos fragmentos de ovários demonstrou a presença constante de ovócitos em todas as etapas de desenvolvimento, folículos pós-ovulatórios, além de atresia folicular. Ovócitos em crescimento primário estiveram presentes em maior número no grupo-controle, enquanto ovócitos em crescimento secundário foram mais numerosos no grupo tratado. Folículos pós-ovulatórios foram mais numerosos no grupo-controle que no grupo tratado, e sua detecção tornou-se mais difícil entre 96 e 120 horas após a desova. A atresia foi observada em maior intensidade no grupo tratado que no grupo-controle. Diferenças significativas (P<0,05) na contagem de folículos atrésicos entre os grupos experimentais foram registradas as seis e às 48 horas pós-desova. Não foram constatadas diferenças significativas (P>0,05) para a contagem de eosinófilos dentro dos grupos experimentais. Observou-se maior quantidade de eosinófilos no grupo tratado, coincidindo com as maiores quantidades de folículos atrésicos nesse grupo. Diferença significativa (P<0,05) foi observada quando foram associados os valores de atresia e eosinófilos e comparados os mesmos entre os grupos experimentais. Por ser espécie de desova parcelada e não apresentar variação brusca no tamanho das gônadas, não foram encontradas diferenças significativas (P>0,05) para IGS nos diferentes horários de coleta e nem entre os grupos experimentais. Diferenças estatísticas (P<0,05) para os valores de IHS foram encontradas entre os grupos experimentais as nove e às 96 horas pós-desova. Valores mais altos de IHS registrados no grupo que recebeu a dose de hormônio de crescimento coincidem com a maior quantidade de ovócitos em vitelogênese observada nesse grupo. Não foram encontradas diferenças estatísticas (P>0,05) para o fator de condição K2.

The Nile perch, Lates niloticus (Linnaeus, 1758), is a predacious freshwater fish widely distributed throughout the Afro-tropic eco-zone. The species was introduced to Lake Victoria in the early 1950s and by 1980 it had dominated the fisheries of Lake Victoria. This was followed by a dramatic decrease in the Nile perch fisheries production due to uncontrolled exploitation. The purpose of this thesis is to provide fundamental knowledge that can be applied in aquaculture and fisheries management through the study of the reproductive biology of L. niloticus. The research was aimed at the studying of the diverse aspects of the reproductive biology of L. niloticus in the Lake Victoria, Ugandan populations. This included reproductive patterns in relation to proximate environmental conditions, size at sexual maturity, gonad and gamete structure, gametogenesis and induced ovulation. The size at 50% sexual maturity for female Nile perch was 59.4 cm, which is lower than the earlier reported size of greater than 90 cm total length. Male L. niloticus matured at 57.8 cm total length in Lake Victoria. Microscopy revealed that L. niloticus from Lake Victoria had one spawning period that started in November and ended in March. Type I atresia occurred at high frequency from March to June, and type III atresia was present from July to September and between November and December. Spermatogenesis in L. niloticus is cystic and sperm development is the result of asynchronous activation of the germ cells. Type II spermatozoa are simple, uni-flagellate aquasperm with no acrosome. Oogenesis in L. niloticus differed from that of other fishes in that no cortical alveoli were present in any stage of oogenesis. Numerous oil globules were present in the primary yolk vesicle stage. This formed one centrally positioned, large oil globule in the tertiary yolk vesicle oocytes during final oocyte maturation. Clove oil was an effective sedative and an anaesthetic for the handling of L. niloticus. Induction time was more rapid at clove oil concentrations of 50 - 100 μl L⁻¹ than in fish exposed to clove oil concentrations less than 50 μl L⁻¹. Fish exposed to high concentrations exhibited significantly short induction times of less than 240 seconds. On average, fish recovered within 673 ± 58 seconds for all the concentrations used. Prolonged exposure of L. niloticus to low clove oil concentrations of 2.5 - 10 μl L⁻¹ did not change the blood plasma cortisol, glucose, and the lactate and chloride ion concentration, relative to the control treatment. Captive breeding was attempted by conducting induced spawning experiments. Only final oocyte maturation was achieved using a decapeptide Gonadotropin Releasing Hormone (Dargin, sGnRH-MET), combined with a water-soluble dopamine receptor antagonist metoclopramide. This thesis suggests a research approach that provides a basis for aquaculture of the new species by first studying reproductive biology patterns and then linking the information to gonad and gamete structure so that spawning times can be estimated. It further provides insights into aspects of the reproductive biology of the species and the effects of hormonal intervention on oocytes by showing at which stage of oocyte development hormones should be applied in L. niloticus. Clove oil can be used to sedate and anaesthetise L. niloticus broodfish to reduce the stress related to the handling of large specimens.