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Notes: The monthly variation in reproductive cycle, condition factor (fatness), gonad index (GI), ovarian egg diameter and biochemical composition [RNA, DNA content and their ratio RNA/DNA (R/D)] were compared to determine the spawning season of the purplish Washington clam, Saxidomus purpuratus, collected from the west sea of Taean, Korea. All these factors were correlated to the spawning season from May to October. Monthly variation and concentration of the R/D ratio especially represented indicative information about the processes of gonad development and spawning patterns. The increases in R/D ratio in the ovaries corresponded with increases in ovarian egg diameters and the GI during the spawning season. The peak of R/D and RNA content in females was a good indicator of sexual maturation and the DNA content in males. During winter between November and January, the value of fatness, GI, egg size, RNA and DNA content were lower than in other seasons, indicating depletion of energy reserves and lower metabolic demands because of colder temperatures.

Notes: Offshore production offers a new perspective for mussel aquaculture in the German Bight (North Sea) as no expansion is possible in the intertidal and subtidal zone of the Wadden Sea because of restrictions on the number of licenses. The development of offshore wind farms offers a unique opportunity because of the associated infrastructure. Service platforms, as well as the pylons themselves, offer perfect structures for mooring longlines and other culture units. One of the advantages of offshore culture may be a lower parasite load in offshore mussels compared with mussels produced under traditional inshore bottom culture. By sampling mussel spat from offshore suspended buoys or collectors, we simulated an offshore culture situation and compared parasite infestation rates with those in mussel spat obtained from suspended inshore buoys or collectors, in mussels from inshore benthic subtidal beds and from inshore benthic intertidal mussel beds. Mussels from offshore sites were free of trematodes and shell-boring polychaetes. Parasitic copepods only occurred at a single offshore site, on a 20-year-old research platform, but not on buoys or collectors exposed for shorter time periods. All three monitored parasite taxa were present at all other sites. The highest prevalence was found for trematodes in inshore benthic intertidal mussels (78.7 ± 6.4%) and locally reached 100%. Through a variety of detrimental effects, trematodes, parasitic copepods and shell-boring polychaetes are known to affect growth performance and product quality. We therefore propose that offshore mussel production could be a promising culture procedure because it seems to result in lower parasite burden than at traditional culture sites. Whether offshore production also results in better survival and growth, compared with inshore mussel culture on a commercial scale, needs to be investigated further.

Notes: The seasonal growth trajectories of wild Atlantic salmon Salmo salar juveniles by age group within the Margaree River, Canada, are described. Circuli counts from scales were used to infer growth rates at different ages and these were used to predict the proportions of age 2- and 3-year old smolts from different portions of the watershed. In the wild Atlantic salmon juveniles from the Margaree River, there was no bimodality in fork length frequencies and no 1 year old smolts were produced. Water temperature differences during the growing season were insufficient to explain the differences in growth rates and size at age among the sites sampled. There was a positive association between the growth rate in the first year and the subsequent age at smoltification. In the Margaree River, differences in tributary specific growth rates and size at age were expected to produce important differences in the relative ages at smoltification.

Notes: Aquaculture in Germany is a small industry, practiced only in a few specifically suited areas. Marine finfish farming is almost nonexistent but mussel farming is a steady activity with a notable level of production. However, this industry is presently very restricted with no hope for expansion as regulations are stringent and new licences in both fresh and marine waters are extremely difficult to obtain. In addition to State-specific conditions within the Federation, the complexity of the regulatory framework is exemplified by focusing on some key aspects for finfish farming and by specific aspects of mussel farming activities in the Schleswig-Holstein Wadden Sea where environmental protection measures dictate the level of control, mainly as a result of the recent establishment of the National Wadden Sea Park.

Notes: This paper provides a short overview on the status of sturgeon farming in Europe, covering most of the EU and former East Block countries. Production trends are presented along with a listing of species cultured in various countries. Principle culture systems are described and an opinion is presented on possible constraints and perspectives of sturgeon farming, including market opportunities.

Notes: In light of the 1982 fish health reulations, the structure of freshwater aquaculture is reviewed in the northwestern Federal Reublic of Germany, mainly in Lower Saxony and neighbouring areas. Main fish producers include fuly-time and part-time operators, hobby farmers, and sport fishing associations. Addressed especially in relation to the control ofish epidemics, are the problems generated by “hobbyists”, who represent almost 77% of the producers. The heterogenous structure of freshwater fish-producing sites, the economically marginal status of freshwater fish production in Germany in comparison to other animal husbandries as well as their lack of an influential lobby, are discussed as the main reasons for limited development prospects. Bio-technical and economical problems in high-tech warm-water aquaculture units for eel and sheatfish production are briefly addressed. Statistics on imports as well as domestic production are presented, indicating that Germany will remain an importer of both fishery and auacultural products, Therapeutical measures are outlined, along with their limitations in freshwater fisleries and aquaculture in Germany. The difficulties in obtaining official approvd of drugs and the application thereof are presented; reasons for these problems and the dangers of the existing limitations are outlined. The mode of application is described for those very few drugs licensed for fish culture in Germany. The present status of drug application in Lower Sxony is presented in detail. The sensitivity of, e.g., Yersinia ruckeri against 12 antibiotics and chemotherapeutics routinely tested in the antibiogramme is shown between 1986 and 1989. Examples are presented from field work of the Fish Health Service of Lower Saxony.〈section xml:id="abs1-2"〉〈title type="main"〉Zusammenfassung Süwasser-Fischerzeugung und Fischkrankheiten in Niedersachsen(Bundesrepublik Deutschkznd): Erfahrungen des FischgesundheitsdienstesEs wird ein überbiick über die Struktur der Nutzfischroduktion im SüßSwasser in Niedersachsen und angrenzenden Gebieten aus norddeutscher Sicht gegegen. Dies ist insbesondere im Hinblick auf die Fischkrankheiten und die entsprechenden Regelungen seit 1982 ausgerichtet. Innerhalb der wichtigsten Produktionszweige (Hauptberufliche, Nebenerwerb, Hobbyteichwirt, Angelvereine) wird die Proble-matik der Hobbyisten angesprochen. Die heterogene und wenig wirtschaftliche Struktur der Süßwasser-Fischproduktion der norddeutschen Teichwirtschaft sowie die im Vergleich zu anderen Wirt-schaftszweigen marginale Stellung dieser Tierproduktion und der damit verbundene Mangel an politi-schem Einfluß wird diskutiert. Hinzu kommen bio-technologische Probleme der modernen Auakultur insbesondere bei Aal und Wels. Die begrenzten Möglichkeiten der Therapie von Fischkrantheiten wird beschrieben mit Hinweisen auf die Schwierigkeit der verwaltunsrechtlichen Zulassung von Wirk-stoffen zwecks therapeutischem Einsatz. Die Gründe hierfür sowie die Gefahren fiir die Praxis werden an Hand der Daten aus der Feldarbeit des Niedersachsischen Fischgesundheitsdienstes aufgezeigt. Die praktische Anwendung und Effizienz einiger Wirkstoffe sowie ihr Resistenzstatus wird für der. Zeit-raum 1986 bis 1989 dargestellt. Hierbei wird auf fischpathogene und fakultativ-pathogene Bakterien eingegangen, deren Empfindlichkeit gegen zugelassene und (noch) nicht zugelassene Wirkstoffe er-arbeitet wurde.〈section xml:id="abs1-3"〉〈title type="main"〉RésuméProduction de poissons en eau douce et maladies des poissons en Basse-Saxe (République Fédérale d'AIIemagne): Expériences du Service de Santé des PoissonsUne vue d'ensemble de la structure de l'aquaculure en eau douce du nord-ouest de la République Fédérale d'Allemagne, c'est sà dire la Base-Saxe et régions voisines, est présentée. En particulier, l'accent est mis sur les maladies de soissons et les régulations mises en place depuis 1982. Les principeaux producteurs incluent des progssionnels sà temps plein ou temps partiel, les pisciculteurs de loisir et les clubs de péches. Les hobbyistes, qui représentent 77% des producteurs, posent des poblémes spéciale-ment pour le contrôle des maladies endémiques. La structure hétérogne et peu rentabe de l'aquaculture en eau douce, ainsi que son apport marginal au point de vue économique comparé avec les autres productions animales et donc son manque d'iduence politique sont proposés comme raisons princi-pales de son diveloppement limité. En plus, les poblémes biotechniques et économiques de l'aquacul-ture moderne, en particulier pour l'anguille et le silure, sont briévement discutés. Les statistiques de l' importation et de la production domestique sont prisentis, montrant que l'Allemagne restera un importateur de produits de pêche et d'aquaculture. Les possibilités thérapeutiques sont discutés, ainsi que les diificultés posés par les reglements d'agrémentation des produits sà but thérapeutique et leurs applications. Les raisons de ces problémes et le danger des limitations actuelles sont soulignis par l'analyse des données recoltés sur le tas en Basse-Saxe. L'utilisation pratique et I'éfficacité des quelques médicaments autorisis en Allemagne, ainsi que le développement de la résistance contre ces midicaments, sont présentés pour la periode 86–89. Enfin, les pathogénes et les bactéries, pathogénes facultative, dont la résistance aux médicaments autorisés ou en cours d'agrémentation a été testée, sont décrits.