Fróðskaparrit - 01.01.2008, Page 161

SNÍKAR ÍFØROYSKUM KOMBIKKI, GASTEROSTEUS ACULEATUS L.
159
Prevalence of infcction with Gyrodactylus sp. in
sticklcbacks froni all stations
Fig. 7 Prevalence of infection
with Gyrodactylus sp. In
sticklebacks from all stations..
□2002
■ 2003
□ 2004
locality
ling of the abdomen was observed, due to
large specimens of plerocercoids. This ces-
tode was only seen in freshwater samples
(Figs. 5A and 5B). Prevalence of infection was
1.7-62.8 %. In Klubbatjørn only one fish was
infected one year (2004). In the Toftavatn-
2002-sample no fish was infected. There
seems to be a tendency of diminishing val-
ues in the three-year period examined (Fig.
5A). The growth of the plerocercoids in the
fish is shown in Figs. 6A-F. The largest plero-
cercoid was 4.5 cm.
Intensity of infection was 1.8-3.8 and
seems to follow the prevalence of infection
(Fig. 5B). The maximum number of plero-
cercoids in one fish was 82 (Skúvadalur, in
2002) where the different developmental
stages of the small plerocercoids could be
seen. The highest mean value per infected
fish (3.8) was also found in this sample. Fish
with an extended stomach (Fig. 5C) were
usually filled with a weight of 20-30 % ces-
todes, compared to body weight.
2.4. Gyrodactylus sp. (Monogenea). Fig. 7
Sticklebacks from the marine localities have
the far highest prevalence of infection (0-
43.6 %), compared to freshwater localites (0-
12.1 %) (Fig. 7). The intensity of infection is
ranging from 1-31. The highest mean was 2.6,
(Kráargil, 2003) and highest value was 31
specimen of Gyrodactylus sp.)
2.5. Diplostoma sp. and other digeneans
(Digenea)
This parasite of the eye was only observed in
2004 (Kráargil, 2003, prevalence of infection
4.96%). Unidentified digeneans were seen in
two samples (Toftavatn, 2004 and Klub-
batjørn 2004; prevalence of infection 8.5 %
and 3.5 %, respectively). All specimens were
so small that they may have escaped atten-
tion the other years.
3. Disease conditions
Three types of diseased conditions could be
observed: "fin rot”, "white spot disease" and
"cysts", all on the outside of the fish. No at-