Egg quality and fecundity in rainbow trout: the determining factors and mechanisms of control

This thesis considers the factors involved in the determination of egg quality and fecundity in farmed stocks of rainbow trout ( Salmo gairdneri R) • Measurements of egg quality, ie. percentage survivals of eggs and fry, from the production batches of eggs of seven fish farms, showed mean survivals of 70% to eying but levels of only 35% to 4.5g fry (approx. 130 days post-fertilisation). Under optimum conditions survivals may reach 85% suggesting that husbandry methods exert significant influences on egg quality. Chemical analyses of the protein, fat, vitellogenin, ash, amino acids, free fatty acid and mineral levels of eggs of varying quality and from parents of different strains showed compositional differences even between individuals of the same stock. However, none of these differences were correlated with egg quality. Egg size showed similar variations but, again under hatchery conditions there was no correlation with differences in egg quality. The only factor which has been shown to exert a significant influence on egg quality is the time of stripping after ovulation. At 1 0°C eggs should be removed from gravid females within ten days of ovulation to achieve optimum egg and fry survival. Studies of egg production from approximately 10,000 broodstock revealed that total fecundity and egg size increased and relative fecundity decreased with increasing fish size. In general, most fish appeared to produce a constant volume of eggs. This is consistent with a hypothesis that egg size can only be increased by parallel reductions in fecundity. Feeding broodstock at half-ration (0.35% body weight day- 1 ) did not affect egg quality but reduced total fecundity and egg size and increased relative fecundity when compared with eggs produced by fish on full-ration. Comparisons of regressions of total fecundity against fish weight for three strains using ANOCO revealed that one strain was significantly more fecund than two other strains considered. Trout of the same strain maintained on different farms behaved similarly suggesting there was some reproducibility of strain characteristics.

Bacterial associations with salmonid eggs

Rainbow trout eggs Salmo gairdneri, Richardson, were incubated under a range of different environmental conditions. Recovery of bacteria from egg surfaces revealed that increased water temperature, slow water flow rates and high egg density all significantly increased egg surface bacterial populations. Live eggs were mainly colonized by Cytophaga sp., pseudomonas fluorescens and Aeromonas hydrophila. In contrast, dead eggs supported considerable numbers of fluorescent Pseudomonas sp. Analysis of potential nutrient sources for bacteria colonizing live egg surfaces revealed that small amounts of amino acids, phosphate and potassium may be lost by incubating eggs. Subsequently these nutrients were shown to be capable of supporting limited bacterial growth and reproduction. Dead eggs `leaked' increased amounts of the above nutrients which in turn supported higher bacterial numbers. In addition, biochemical analysis of eggs revealed amino acids and fatty acids that might be utilized by bacteria colonizing dead egg surfaces. Assessment of adhesion properties of bacteria frequently recovered from egg surfaces revealed high cell surface hydrophobicity as an important factor in successful egg colonization. Analysis of egg mortalities from groups of rainbow trout and brown trout (S.trutta L.) eggs maintained under two different incubation systems revealed that potentially a close correlation existed between egg surface bacterial numbers and mortalities in the egg during incubation. Innoculation of newly-fertilized eggs with bacteria demonstrated that groups of eggs supporting high numbers of P.fluorescens suffered significantly higher mortalities during the early part of their incubation. Exposure of incubating eggs to oxolinic acid, chlortetracycline and chloramphenicol demonstrated that numbers of bacteria on egg surfaces could be significantly reduced. However, as no corresponding increase in egg hatching success was revealed, the treatment of incubating eggs with antibiotics or antimicrobial compounds can not be recommended. In commercial hatcheries bacteria are only likely to be responsible for egg deaths during incubation when environmental conditions are unfavourable. High water temperatures, slow water flow rates and high egg density all lead to increased bacterial number of egg surfaces, reduced water circulation and low levels of dissolved oxygen. Under such circumstances sufficient amounts of dissolved oxygen may not be available to support developing embryos.

Mesozoic to recent evolution of the Andean forearc of northern Chile (22-24 s)

The Andean forearc of northern Chile comprises four morphotectonic units, which include from east to west: 1) The Cordillera de la Costa: composed of Jurassic granites and andesites, thought to represent a volcanic arc, the Mejillones terrane, an accreted allochthonous terrane, and the Lower Cretaceous Coloso basin, which formed through forearc extension along the suture between the Mejillones terrane and the Jurassic arc. Palaeomagnetic studies of the above units have identified approximately 29+/-11 degrees of clockwise rotation. Rotation is due to extension (caused by subduction roll back and slab pull), at an angle to the direction of absolute motion of the South American Plate. 2) The Central Depression: a large arid basin containing isolated fault-bounded blocks of pre-Mesozoic metamorphosed igneous rocks, Triassic sediments and volcanics, and Jurassic carbonates, deposited in a. back-arc basin setting. The isolated blocks formed through extension along previous thrust faults, these originated through compression of the back-arc basin due to accretion of the Jurassic volcanic arc. 3) The Precordillera.: composed of Permian-Triassic rift-related sediments and volcanics, Jurassic continental sediments synchronous with back-arc basin sedimentation, and Cretaceous and Oligo-Miocene continental sediments deposited in foreland basins. Palaeomagnetism has identified clockwise rotation in rocks ranging in age from Jurassic-Miocene. Rotation in the Precordillera. affected larger structural blocks than in the Cordillera de la Costa. 4) The Salar Depression: a. series of arid continental basins developed on continental crust. These basins nay have originated in the Triassic, when rifting of the South American craton is thought to have taken place. In conclusion, palaeomagnetic and geological evidence is consistent with the view that the north Chilean forearc was largely under an extensional stress regime. However, the presence of extensive compressional structures in Palaeocene and older rocks in the forearc together with the currently active foreland thrust belt of Argentina. indicate that throughout the evolution of the Andean Orogen, a delicate balance between compressional and extensional tectonic regimes has existed.

Viral and bacterial septicaemic infections modulate the expression of PACAP splicing variants and VIP/PACAP receptors in brown trout immune organs

Copyright © 2015. Published by Elsevier Ltd. Acknowledgments The authors thank Richard Paley, Georgina Rimmer and Tom Hill for their contribution during the brown trout infection challenges carried out in CEFAS-Weymouth biosecurity facilities. Bartolomeo Gorgoglione and Nick G. H. Taylor were supported by a DEFRA contract C3490

Análise dos hábitos alimentares e de consumo de pescado das populações de Leiria e Peniche

Presentemente, o consumidor encontra à sua disposição uma diversidade de produtos alimentares que tornam a seleção dos alimentos uma tarefa muito mais complexa quando comparada com o passado. Diferenças culturais, sociais, pessoais e psicológicas influenciam o comportamento e as perceções dos consumidores. Sendo Peniche uma península com forte tradição piscatória procurou-se junto da população, perceber se as influências da região são refletidas nos seus hábitos de consumo e se diferem muito de uma região que não tenha as mesmas influências. Com base nas considerações acima referidas, o objetivo deste estudo foi avaliar os hábitos de consumo de pescado das populações de Leiria e Peniche através de um inquérito por questionário com apoio presencial, visando delinear o hábito de consumo, bem como a frequência, as preferências e restrições associadas ao consumo de pescado. Além disso, são relatadas as perceções dos consumidores em relação ao pescado selvagem e de aquacultura. Portugal é atualmente o país da União Europeia com o maior consumo anual de pescado por pessoa, e o terceiro do mundo, só ultrapassado pela Islândia e pelo Japão. O estudo foi realizado em 383 indivíduos residentes em Leiria e em 374 residentes em Peniche, maioritariamente do sexo feminino, com idades compreendidas entre os 30 e os 45 anos e detentores de grau de ensino superior. Os resultados mostram que os inquiridos consomem peixe, preferencialmente, cozido e grelhado, entre uma a três vezes por semana sendo que o bacalhau, o carapau, o salmão e a pescada estão entre as espécies mais consumidas. Devido à conveniência, pronta disponibilidade e preços acessíveis, os supermercados são os locais preferidos dos consumidores para comprarem peixe fresco e congelado. Além disso, a população de Peniche mantém o hábito de adquirir peixe fresco na peixaria e diretamente ao pescador. Apesar das duas populações exibirem uma maior propensão para consumir pescado selvagem, em Leiria o consumo de espécies de aquacultura aumenta com o grau de ensino. Por conseguinte, o pescado selvagem é considerado mais saudável, mais nutritivo, saboroso e mais seguro, sobretudo pela população que vive na zona costeira e que segue hábitos alimentares tradicionais. O pescado é percebido como um alimento saudável que possui alto teor em proteínas e ácidos gordos Omega-3, e baixo teor de gordura. No entanto, o preço elevado, a falta de disponibilidade para a sua confeção e as preocupações com os contaminantes presentes no pescado e consequentes riscos para a saúde são barreiras ao consumo de pescado. Os consumidores com mais idade mostram-se pouco recetivos à oferta de produtos inovadores à base de pescado por considerarem estes produtos de fraca qualidade. Com o avançar dos tempos, os habitantes de Peniche foram adquirindo novos hábitos de consumo e hoje em dia o consumo de pescado não difere muito da população de Leiria.

Unexpectedly high catch-and-release rates in European marine recreational fisheries: implications for science and management

While catch-and-release (C&R) is a well-known practice in several European freshwater recreational fisheries, studies on the magnitude and impact of this practice in Europeanmarine recreational fisheries are limited. To provide an overview of the practice andmagnitude of C&R among marine recreational anglers in Europe, the existing knowledge of C&R and its potential associated release mortality was collected andsummarized. The present study revealed that in several European countries over half of the total recreational catch is released by marine anglers. High release proportions of > 60% were found for Atlantic cod (Gadus morhua), European sea bass (Dicentrarchus labrax), pollack (Pollachius pollachius), and sea trout (Salmo trutta) in at least one of the studied European countries. In the case of the German recreational Baltic Sea cod fishery, release proportions varied considerably between years, presumably tracking a strong year class ofundersized fish. Reasons for release varied between countries and species, and included legal restrictions (e.g. minimumlanding sizes and daily bag limits) and voluntary C&R. Considering the magnitude of C&R practice among European marine recreational anglers, post-release mortalities of released fish may need to be accounted for in estimated fishingmortalities.However, as the survival rates of Europeanmarine species aremostly unknown, there is a need to conduct post-release survival studies and to identify factors affecting post-release survival. Such studies could also assist in developing species-specific, best-practice guidelines to minimize the impacts of C&R on released marine fish in Europe.