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Aquaculture is the main source to increase fish supply. Fast development of aquaculture and increasing fish demand lead to intensification of fish culture, magnifying stressors for fish and thus heightening the risk of disease. Until now, chemotherapy has been widely used to prevent and treat disease outbreaks, although use of chemical drugs has multiple negative impacts on environment and human health e.g. resistant bacterial strains and residual accumulation in tissue. Hence, disease management in aquaculture should concentrate on environmentally friendly and lasting methods. Recently, increasing attention is being paid to the use of plant products for disease control in aquaculture as an alternative to chemical treatments. Plant products have been reported to stimulate appetite and promote weight gain, to act as immunostimulant and to have antibacterial and anti-parasitic (virus, protozoans, monogeneans) properties in fish and shellfish aquaculture due to active molecules such as alkaloids, terpenoids, saponins and flavonoids. However, as it is a relatively emerging practice there is still little knowledge on the long-term effects of plant extracts on fish physiology as well as a lack of homogenization in the extract preparation and fish administration of the plant extracts. This article aims to review the studies carried out on the use of plant products on fish aquaculture and their biological effects on fish such as growth promoter, immunostimulant, antibacterial and anti-parasitic. It also intends to evaluate the current state of the art, the methods used and the problems encountered in their application to the aquaculture industry.

The sclerotized attachment organ of monogeneans has been widely used to address fundamental questions in ecology and evolution. However, traditional morphometric techniques appear to be partially inadequate and non-optimal. Traditional linear measurements mainly provide information on the size of sclerites but provide very little information, if any, on their shape. The shape of sclerites is indeed virtually unexplored and its implication for ecological and evolutionary processes remains to be analyzed. This study aims to both introduce and illustrate the use of geometric morphometrics in order to study sclerites of monogeneans in a biogeographic context. To do this, we investigated morphological variation patterns among four populations from the Pacific Ocean and six monogenean species through traditional and geometric morphometric techniques. Unlike the traditional method, the geometric morphometric method yielded a high percentage of individuals correctly classified to the four populations, providing strong evidence for phenotypic variability, divergence and local adaptation among islands without evolutionary constraint. Moreover, the traditional method also resulted in inconsistent interpretations of shape variations. This study highlighted the limitations that may arise when using traditional morphometric techniques and emphasizes that considerable information about the shape of sclerotized haptoral parts is added by using geometric morphometrics. Given the prominent taxonomic, ecological and evolutionary role of the haptor for characterizing monogeneans, we ultimately discuss the potential broad use of geometric morphometrics in a wide variety of ecological and evolutionary contexts. This powerful approach might allow a more robust estimation of the extent to which traditional evolutionary theories based on size of sclerites are congruent with their shape.

Parasite species have been widely used as fish host migration tag or as indicators of local pollution. In this paper our approach is to consider the entire parasite community as a biological indicator of the fish environmental conditions. Seven fish species belonging to the Apogonidae, Apogon bandanensis, A. cookii, A. doderleini, A. norfolkensis, A. trimaculatus, Cheilodipterus quinquelineatus and Fowleria variegata, were sampled on six stations in two bays (Grand-Rade and Sainte-Marie) around Noume´a (New-Caledonia). The two bays are submitted to urban wastewater inputs alone or combined with additional industrial inputs which influences decrease from the inner part to the entrance of each bay. A total of 592 fish were dissected for macro parasite examination. Parasites were grouped according to their taxonomical rank and development stage for the analysis. We found an inconsistent effect of the confinement between the two bays, revealing that the parasite community is not the same in the two bays. Moreover, the encysted metacercariae found in the pericardic cavity were found to be significant indicators of the specific anthropogenically impacted environmental conditions prevailing in the inner parts of the two bays. Other parasite taxa were found to be significant indicators of specific environmental conditions in one or two stations among the six sampled. Results on parasite specificity and biological life cycle of the parasite taxa found in sampled Apogonid were further compared with environmental parameters.

Recruiting coral reef fish larvae from 38 species and 19 families from New Caledonia were examined for parasites. We found 13 parasite species (Platyhelminthes: Monogenea, Cestoda and Trematoda) but no acanthocephalan, crustacean or nematode parasites. Over 23% of individual fish were infected. Didymozoid metacercariae were the most abundant parasites. We conclude that most of the parasites are pelagic species that become 'lost' once the fish larvae have recruited to the reef. Larval coral reef fish probably contribute little to the dispersal of the parasites of the adult fish so that parasite dispersal is more difficult than that of the fish themselves. (C) 2000 Australian Society for Parasitology Inc. Published by Elsevier Science Ltd. All rights reserved.

The comparative approach has been used widely in evolutionary ecology during the last 10 years. In the first part of this study, taking monogeneans of Mediterranean marine fishes as an example, we highlight the pitfalls that may arise in interspecific studies. In the second part, the independent contrast method is used to control for phylogenetic effects in order to evaluate the determinants of monogenean species richness and their specificity. Our results show the importance of controlling data for both host sample size and phylogeny to avoid confounding effects. Thereafter, taking into account both sampling effort and phylogenetic effects, our results show that host size is the main factor affecting monogenean species richness and specificity.