Workpackages

To use parasites infecting the visceral organs of herring as “biological tags” for stock identification and to follow recruitment and seasonal migrations. The following objectives will be pursued to achieve this:
1. To record the species composition of the parasite fauna of herring in the study area.
2. To select the most promising tag species from this fauna.
3. To develop molecular markers for these species and to identify populations of these species.
4. To use these parasites for stock identification and to follow migrations of herring in the study area.

Visceral organs of herring will be examined, initially for all parasites, then for selected species. Organs will be examined for helminth macroparasites, and smears for microparasites (myxozoans, protozoans, fungi). Permanent preparations and photographs will be made of all parasite species found. Parasites will be selected for further study based on established criteria including different levels of infection in different parts of the study area, life spans in herring, pathogenicity and ease of identification. Helminth parasites and larvae will be counted and samples preserved for development of molecular markers. Data on prevalence, intensity, abundance and frequency distributions of tag parasites will be analysed using tests of statistical significance.
Conserved primers will be used to amplify mtDNA NDI and COI genes and rDNA spacers from parasites of several species and differing geographical locations. If suitable primers are not available, conserved regions of the genome of related species will be analysed and new primers designed. DNA will be amplified by PCR and analysed by restriction enzyme digestion and nucleotide sequencing. Sequences will be compared within and between species, and with sequences from databases to analyse inter- and intra-specific variation and correlate with origin of each sample. Parasite DNA libraries enriched for microsatellite repeats will be constructed and primers for microsatellite PCR designed. Suitable primer sets will be selected for microsatellite analysis of larger numbers of specimens from different locations, different year classes and different stock components. All data will be interpreted in terms of herring stock identification and migrations.

(C) EU-project WESTHER 2003 | WESTHER home | mail