Fischparasiten als Bioindikatoren: Zum Umweltstatus von Küstenökosystemen und einer Zackenbarschmarikultur in Indonesien

Abstract

In the present study a total of 325 groupers belonging to the species Epinephelus coioides (195), E. areolatus (60) and E. fuscoguttatus (70) from Indonesian coastal marine ecosystems in the Segara Anakan Lagoon (Central Java), Balinese waters and the Thousand Islands were investigated for parasites in 2008 and 2009. A total of 33 different parasite species/taxa belonging to the Ciliata (1), Microsporea (1), Digenea (9), Monogenea (2), Cestoda (4), Nematoda (6), Acanthocephala (2), Hirudinea (1) and Crustacea (7) was found. Furthermore, the morphologically predetermined Anisakis sp. were confirmed as Anisakis typica and Anisakis sp. (HC-2005) using molecular biological methods. Scatophagus argus (58) from inside and outside the Segara Anakan Lagoon were studied for additional regional comparisons. In total 13 different parasite species/taxa belonging to the Ciliata (1), Microsporea (1), Digenea (2), Monogenea (1), Cestoda (1), Nematoda (1), Acanthocephala (1) and Crustacea (5) could be listed. Therefore, 41 parasite species/taxa, including 16 ectoparasitic and 25 endoparasitic parasites, could be isolated from all 383 investigated fishes of all sampling sites. These 41 detected fish parasites were taxonomically processed by using different techniques. 20 new host records (E. coioides four, E. areolatus 13, E. fuscoguttatus one and S. argus two new records) und 23 new locality records, mainly from Balinese waters and the coastal zone of the Segara Anakan, Central Java, could be revealed. Because of minor variability within parasite communities of free living and mariculture fishes in stable ecosystems between two years, annual differences can only be indicated over a long-term period. A comparison of the new data with previous investigations (Rückert 2006) of E. fuscoguttatus (2003/04-2008/09) indicates either a broad degradation of the surrounding ecosystem or management changes within the mariculture (Palm et al. submitted). The parameters Evenness of endoparasites, ecto-/endoparasite ratio and endoparasite diversity appear to be especially adequate to reveal differences in the parasite infestation over several years. The parameters endoparasite diversity and Evenness were tested ( Trendtest after Neumann) and confirmed a decreasing trend. This trend represents a higher dominance level and decreasing parasite diversity of particular endoparasite species in this mariculture farm from 2003/04 to 2008/09. This might be due to increasing extraneous causes and/or changes in the facilities management that are directly linked to the occurrence of intermediate hosts and the feed usage, respectively. Accordingly, fish parasites have been shown to be useful as bioindicators and to monitor culture conditions and environmental status in and around a grouper mariculture farm. It was possible to illustrate regional differences and long-term changes in parasite communities of the studied epinephelids by using visual integration of a variety of parasitological parameters within a stargraph. The utilised parameters have been demonstrated to be useful to indicate a general ecosystem change and also long-term variations. The application of a stargraph can be further developed into a fish parasite based evaluation system that can monitor regional environmental health. Cluster-Analyses and MDS Plots likewise can illustrate such differences but fall short in concluding, in explaining these differences. In contrast, the stargraph method enables visualisation of existing differences and also allows statements concerning the respective environmental change by using a variety of ecological parameters. This method can be helpful to monitor environmental impact and change of grouper finfish mariculture in Indonesia.