The application of molecular markers to the study and conservation of fish populations, with special reference to Salmo

The main molecular techniques which can be used to generate genetic markers, and the applications of these markers to studies of fish populations are outlined. Published and ongoing studies, in the authors' laboratories, on brown trout and Atlantic salmon are used to compare the resolution and applicability of allozyme, mitochondrial DNA and minisatellite (variable number of tandem repeats) markers for studies on population structuring, genetic variation within populations, and the impact of the accidental and deliberate introduction of non-native salmonids on the genetic make-up of natural populations.     

Proteinases of potential objects of fish nutrition

The review analyzes data on activities and characteristics of proteinases of digestive system and of cathepsins of various tissues in potential preys of fish differing by the character of nutrition. There are presented data on multiple forms and molecular mass of proteinases, species-related differences, dependence of proteinase activities on the life cycle stages, type of nutrition, and biochemical food composition as well as on temperature and pH optima. Role of cathepsin in evolution of enzymatic systems providing degradation of food protein components in fish is discussed.     

Dietary self-selection in fish: a new approach to studying fish nutrition and feeding behavior

The principles of modern aquaculture encourage the development of fish feeds containing low fish meal content and several types of plant ingredients plus nutrients to avoid depleting global fish stocks and to reduce costs. However, food constituents can affect animal nutrition and feeding behavior, so the effect of different diets on fish behavior and growth needs to be understood to optimize the use of nutrients and to improve fish welfare. The development of multiple-choice self-feeding systems led to a new perspective for investigating these issues in aquaculture species. Our purpose with this review is to summarize the information that has been published to date on this topic and to identify gaps in knowledge where research is needed. Key subjects are assessed under the following major headings: How do we study dietary selection in fish? What food signals do fish use to choose the right diet? and How do fish respond to food challenges? The present review will provide a picture of the main results obtained to date in these studies in aquaculture fish species, as well as perspectives for future research in the field.     

Protein nutrition in fish: protein/energy ratio and alternative protein sources to fish meal

Those interested in the design and manufacture of feeds for intensive fish farming face the basic concern of formulating mixtures for the best yield at the lowest costs. Of the macronutrients in the feed, protein has and continues to receive special consideration because fish present high and specific needs for this constituent. Traditionally, protein has been supplied primarily by fish meals. This paper presents a synthesis of the efforts made and the lines explored to achieve an effective reduction of the amount of fish meal in the feeds for fish, following two strategies: reduction of the protein in the feeds and the use of new raw materials to replace fish meal.     

PIT telemetry as a method to study the habitat requirements of fish populations: application to native and stocked trout movements

Passive integrated transponder (PIT) technology was used to study the behaviour of fishes during the summer season in two headwater streams of northeastern Portugal. A total of 71 PIT tags (12 mm long × 2.1 mm diameter) were surgically implanted in 1⁺ stocked (39) and native (32) brown trout of two size classes (<20.0 and ≥20.0 cm). Eight independent antennae, connected to a multi-point decoder (MPD reader) unit, were placed in different microhabitats, selected randomly every 3 days during the observation period (29 August–9 September in Baceiro stream and 19 September–4 October in Sabor stream). The results confirmed this method as a suitable, labour efficient tool to assess the movement and habitat use of sympatric stocked and native trout populations. About 76.9% of stocked and 59.4% of native PIT tagged trouts were detected. Multivariate techniques (CCA, DFA and classification tree) showed a separation in habitat use between the two sympatric populations. Stocked trout mainly used the microhabitats located in the middle of the channel with higher depths and without cover. Furthermore, these fishes displayed a greater mobility and a diel activity pattern different to native trout populations.     

Spatial analysis of stable isotope data to determine primary sources of nutrition for fish

Carbon and nitrogen stable isotopes were used to determine the ultimate autotrophic sources supporting production of three commercially important fish species over unvegetated mudflats in a subtropical estuary. Mean isotope values over the whole estuary for fish and autotroph sources were modeled to indicate feasible combinations of sources. Variability in isotope values among nine locations (separated by 3-10 km) was then used as a further test of the likelihood that sources were involved in fish nutrition. A positive spatial correlation between isotope values of a fish species and an autotroph indicates a substantial contribution from the autotroph. Spatial correlations were tested with a newly developed randomization procedure using differences between fish and autotroph values at each location, based on carbon and nitrogen isotopes combined in two-dimensional space. Both whole estuary modeling and spatial analysis showed that seagrass, epiphytic algae and particulate organic matter in the water column, including phytoplankton, are likely contributors to bream (Acanthopagrus australis) nutrition. However, spatial analysis also showed that mangroves were involved (up to 33% contribution), despite a very low contribution from whole estuary modeling. Spatial analysis on sand whiting (Sillago ciliata) demonstrated the importance of two sources, mangroves (up to 25%) and microalgae on the mudflats, considered unimportant based on whole estuary modeling. No spatial correlations were found between winter whiting (Sillago maculata) and autotrophs, either because fish moved among locations or relied on different autotrophs at different locations. Spatial correlations between consumer and source isotope values provide a useful analytical tool for identifying the role of autotrophs in foodwebs, and demonstrated here that both in situ production of microalgae and organic matter from adjacent habitats were important to fish over mudflats.     

Planktonic and symbiotic organisms in nutrition of coralobiont fish

Nutrition of coral reef fish closely associated with the colonies of scleractinian corals Acropora spp. (South China Sea, Gulf of Nha Trang) was investigated. Parabionts Dascyllus reticulatus and Chromis caeruleus (Pomacentridae) feed mainly on zooplankton in the water column above the hosts’ colony, and inbionts Gobiodon quinquestrgatus (Gobiidae) rarely leave a host colony and feed generally on coral reef invertebrates. A high part of secondary nutrition objects (on average 19–29%) that indicates deficiency in main food were noted in both categories of fish. Food of all three fish species contains parasites (from 19% in C. caeruleus and up to 25% in G. quinquestrigatus) whose significant part is represented by parasites of coral (approximately 7% in D. reticulatus and C. caeruleus and 15% in G. quinquestrigatus). In addition, larvae of parasites of Isopoda and Facetotecta that are fed by fish in the water column were found. Mucus from the surface of host coral which was recognized on the basis of a high number of nematocysts in fish stomachs was found in food of G. quinquestrigatus for the first time. Positive and negative effects of symbiosis of fish and host-coral were discussed. A commensal character of symbiosis was supposed.     

The application of flow microcalorimetry to the study of enzyme kinetics

The use of flow microcalorimetry to measure velocities for enzyme-catalyzed reactions is described. Studies are presented involving the enzymes chymotrypsin, trypsin, and ribonuclease A. In determining the Michaelis-Menten parameters, V_m and K_m, for these systems complications arise due to substrate depletion and product inhibition. By employing an integrated Michaelis-Menten equation, V_m and K_m can be determined.     

Some experimental approaches to the study of nutrition and parasitic infection

Two experimental models to examine the relationship between host nutrition and parasitic infection are considered. Moniliformis dubius, an acanthocephalan parasite of the laboratory rat, is dependent on the type and amount of host dietary carbohydrate for growth and reproduction. Starch, glucose, fructose, and mannose in host diets support parasite growth and development, but much lower dietary amounts of starch, fructose, and mannose are needed compared to free glucose. The pig-Ascaris suum relationship is considered as a model for human ascariasis. Experimental Ascaris infections in pigs resulted in reduced growth, reduced food intake, lowered biological value of dietary protein, and reduced intestinal lactase activity and lactose tolerance. These results are similar in some respects to reported effects of Ascaris infection in humans.     

Comparative analysis of reproductive traits in 65 freshwater fish species: application to the domestication of new fish species

Based on an extensive literature search (1,000 references), the objectives of the present study were to establish a numerical clustering of temperate freshwater fish based on their reproductive traits and to evaluate whether it was possible to extrapolate zootechnical knowledge among species belonging to the same cluster. About 65 species were classified into ten homogeneous clusters from the analysis of 29 reproductive traits, among which the most important were temperature during spawning, egg incubation and larval rearing, degree-days for incubation, larval size upon hatching, spawning season, and parental care. From this typology, a rather regular continuum of reproductive clusters emerges with two obvious endpoints. Between these two extremes, species could be ordered chiefly according to temperature requirement, spawning season and parental care. In conclusion, this new typology, differing significantly from all others proposed earlier, may now serve as a possible framework to help enhancing the domestication of new species by comparison to species belonging to the same cluster.     

The application of confocal microscopy to study Mixozoa nuclei

The analysis of plasmodium and spore nuclei, f-actin, tialpha- and gamma-tubulin of three Mixosporidia species--Zschokkela nova (Klokacewa, 1914), Myxidium gasterostei (Noble, 1943) and Myxobolus pseudodispar (Gorbunova, 1936)--was performed using confocal microscopy. We have found out the features of nucleus structure and its changes during division and formation of myxospores.     

Observations on malachite green in relation to its application to fish diseases

Summary Experiments were carried out to evaluate several properties determining the mutual influence of the system: fish-bath-malachite green-pathogen.The toxicity of malachite green solutions in concentrations varying between 1 : 80,000 and 1 : 2,560,000 was tested on immature sand whiting. As regards the toxicity of 1 : 80,000 solutions, for practical purposes no distinction between fish of different size, between equal concentrations of chloride and oxalate salts of the dye, or between fresh and decolourized solutions appears necessary.The survival time increased appreciably with decreasing temperature for the range 13.5–28.0°C.The dye solutions always showed significant decolourization when the pH was higher than 5.Several body tissues of the fish, notably the central nervous system and the lateral red muscles, were stained by fresh as well as decolourized malachite green solutions.The dye proved bacteriostatic but not bactericidal, to pseudomonad and coccus cultures when 1 : 80,000 solutions were used. Once decolourized, the dye became a less effective bacteriostatic.The addition of the dye, or formaldehyde, to the bath induced hyperventilation in the fish.A triple dye mixture, consisting of malachite green, brilliant green and crystal violet, was found to be a valuable therapeutic agent.

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Zusammenfassung Einige Versuche werden durchgeführt zur Erklärung verschiedener Eigenschaften, die die gegenseitige Einwirkung in dem System: Fisch - Bad - Malachitgrün - Pathogen bestimmen.Die Toxizität von Malachitgrün-Lösungen in Konzentrationen welche variierten zwischen 1 : 80,000 and 1 : 2,560,000 wurde geprüft an jungen Sand Whiting. Was die Toxizität der 1 : 80,000 Lösungen betrifft, scheint, für praktischen Zwecke, kein Unterschied zu sein zwischen Fischen verschiedener Länge, zwischen gleichen Konzentrationen von Chlorid und Oxalat-Salzen des Farbstoffes, oder zwischen frischen und entfärbten Lösungen. Die Überlebungszeit nahm merklich zu, wenn die Temperatur erniedrigt war, im Gebiet von 13.5°–28.0°C. Die Farbstoff-Lösungen zeigten erhebliche Entfärbung, wenn der pH - Wert grösser war als 5. Verschiedene Körpergewebe des Fisches, insbesondere das Zentralnervensystem und die lateralen roten Muskeln, werden von frischen sowie entfärbten Lösungen grün gefärbt. Der Farbstoff zeigte in 1 : 80,000 Lösungen bakteriostatische, aber keine bakterizide Wirkung, wenn geprüft an Pseudomonas und Kokkus Kulturen. Zusatz des Farbstoffes, oder Formaldehyde, zum Bade veranlasste in dem Fisch Hyperventilation. Ein Tripelfarbstoff-Gemisch, das bestand aus Malachitgrün, Brilliantgrün und Kristallviolett, zeigte sich ein wertvolles Therapeutikum.

     

RAPD技术在我国鱼类研究中的应用

论述了RAPD技术的原理,RAPD技术在我国鱼类遗传进化、遗传多样性、分类、种群亲缘关系、种质鉴定、育种和杂种优势利用等研究方面的应用及其取得的效果。