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Notes: A comparative study of larval growth in the different species of the genus Clarias in different regions revealed that in spite of strong differences in egg and larval size, the growth potential was quite similar. Differences in growth between species and regions were strongly correlated with the applied feeding strategy, the applied growth parameter and period of measuring. To evaluate feeding strategies, standardized procedures for measuring growth are needed. Recalculating the results of the mentioned study according to these standardized procedures revealed that both in India and Indonesia, the growth rate of C. batrachus larvae was too low. This is probably due to low feeding levels in India and premature weaning in Indonesia.The basic biology and nutritional physiology of the larvae of C. gariepinus have been studied extensively. At the start of exogenous feeding, the larvae have an advanced digestive system with a functional pancreas, liver and nutrient absorption capabilities, but lack a functional stomach. The advanced digestive system is further exemplified by the development of the enzymatic complex. Probably because of the rapid development of the digestive system, feeding live food organisms is mostly practiced for a few days only and is soon replaced by wet and/or dry diets. It is hypothesized that the requirement of live food or specific larval diets during the first days of exogenous feeding is related to the absence of pepsin digestion during this period. Further optimization of the feeding strategies should focus on this conclusion.

Notes: Epidermal mucous cells of fish are affected by acidified water. This study provides baseline data of brown trout, Salmo trutta, to distinguish environment-related alterations of mucous cells from changes caused by biological (tissue heterogeneity, ontogeny) or methodological (fixation and histochemical procedures) factors. Knowledge of such factors is unconditionally required before acid-related mucous cell alterations can be discerned.〈section xml:id="abs1-2"〉〈title type="main"〉ZusammenfassungAuf dem Weg zu einer Verwendung epidermaler Schleimzellen in Freilanduntenuchungen zum Säurestreß bei FischenDie Schleimzellen in der Haut von Fischen verändern sich unter dem Einfluß von saurem Wasser. Die vorliegende Studie liefert für die Bachforelle, Salmo trutta, Grundlagendaten, um umweltbezogene Schleimzellenveränderungen unterscheiden zu können von Veränderungen, die biologischen (Gewebe-heterogenität, Ontogenie) oder methodischen (Fixierungs-und Färbeprozesse) Faktoren zuzuschreiben sind. Kenntnis derartiger Faktoren ist unersetzlich, sollen pH-induzierte Veränderungen der Schleimzellen sicher angesprochen werden.〈section xml:id="abs1-3"〉〈title type="main"〉RésuméL'utilisation de cellules muqueuses de la peau en vue du discernement du stress cause par l'eau acide chez les poissonsLes cellules muqueuses de la peau des poissons altèrent sous l'influence de l'eau acide. l'étude présente fournit des dates de base de la truite (Salmo trutta) afin de distinguer entre les altérations des cellules muqueuses, provoquées par des facteurs biologiques (hétérogénéité du tissue, ontogénie) et celles causées par des facteurs méthodiques (procès de fixation et histochimique). La connaissance des ces facteurs est indispensable avant de pouvoir discerner les altérations se référant à l'acidité.

Notes: Six different diets, commonly used in the Philippines for rearing milkfish, Chanos chanos, try, were tested by means of growth, survival and histology. These diets included:a) live food (Anemia nauplii); b) two different dry feeds; c) natural feed supplements (rice bran, egg yolk); d) a mixture of live and dry feeds. The mixed diet was found to give the best results, closely followed by live food. The dietary value of one of both artificial feeds improved with increasing age of the fish, whereas the other was clearly inadequate. The same was true for the natural compounds. Results obtained from statistical and histological analyses were congruent; the latter provided additional insights not obtained with statistic data alone.〈section xml:id="abs1-2"〉〈title type="main"〉ZusammenfassungHistologische Beobachtungen zur Aufzucht von Milchfisch, Chanos chanos, Larven, unter Benutzung verschiedener DiätenSechs verschiedene Futtersorten, die alle auf den Philippinen benutzt werden zur Aufzucht von Larven des Milchfisches, Chanos chanos, wurden mittels Wachstum, Überlebensrate und histologischer Parameter getestet. Die Diäten umfassten:a) Lebendfutter (Artemia Nauplien); b) zwei verschiedene Trockenfutter; c) natürliche Futtermittel (Reis-Kleie, Eidotter); d) eine Mischung von Lebend-und Trockennahrung. Die besten Resultate erbrachte die gemischte Diät, dicht gefolgt vom Lebendfutter. Der Nährwert eines der beiden Trockenfutter verbesserte sich mit zunehmendem Alter der Fische, während das zweite Trockenfutter eindeutig nicht geeignet war. Letzteres traf auch für die narürlichen Futtermittel zu. Statistische und histologische Befunde waren übereinstimmend, doch gewährten letztere zusätzliche Erkenntnisse, die mit den statistischen Daten allein nicht zu erhalten waren.〈section xml:id="abs1-3"〉〈title type="main"〉RésuméObservations histologiques pour l'élevage de larves de Chanos chanos avec de différentes diètesSix divers types de nourritures, utilisées sur les Philippines pour l'élevage de Chanos chanos, ont été testé selon la croissance, le coefficient de survie et de paramètres histologiques. Les diètes comprenaient: a) nourriture vivante (Anemia nauplii); b) deux types de nourritures synthétiques; c) nourriture naturelle (son du riz, du jaune d'oeuf), d) un melange de nourriture vivante et synthétique. Le meilleur résultat a apporté la diète mélangée, succédée de très près de la nourriture vivante. La valeur nutritive d'une des deux nourritures synthétiques s'améliorait avec la croissance des poissons, tandis que la deuxième des nourritures synthétiques ainsi que la nourriture naturelle étaient nettement inadéquat. Les constatations statistiques et histologiques étaient concordantes. Les constatations histologiques cependant apportaient des connaissances additionnelles qu'on aurait pas recu avec les données statistiques seules.

Notes: This study presents an overview of the distribution of proliferative kidney disease (PKD) in wild and farmed fish in Switzerland based on two sources: (1) the results of routine diagnostic work at the National Fish Disease Laboratory, and (2) the results of a country-wide survey for PKD. The first case of PKD in Switzerland was diagnosed in 1979 and since 1981, a few cases have been found every year. Affected species were rainbow trout, brown trout and grayling from rivers and fish farms. Most of the diseased fish were found in the lower altitude regions of the country (Swiss midlands). A seasonal distribution of the cases was evident: PKD-positive fish occurred only from June to November withprominent peaks in August and September. Among infected fish all length classes were present, but the highest numbers of affected fish were found in the length classes 〈10 cm and 16–20 cm. The evaluation of the samples from a survey of the occurrence of PKD in 2000/2001 revealed a much broader geographical distribution of the infection than expected from routine diagnostic observations. Fish from 56 of 139 rivers analysed by histological examination were positive for parasites. Fish from 131 of these sites were examined macroscopically. Of these, trout from 45 sites showed gross alterations indicative for PKD. Most of the positive fish were found in the Swiss midlands north of the Alps. Fish from six of 65 fish farms investigated were found to be PKD-positive by histopathological analysis, and in four of these cases fish could be identified as infected on the basis of gross examination.