Fróðskaparrit

						ARSTIÐARBROYTINGAR I RUNDORMA-INFEKTION I SEIÐI

63

7							

6							

t! i4 a J 1-1 2					-L	--	

1 0		__    __	.---	• - *			

							

	J	F	M	M	A	O        D	

Fig. 5. a. Intensitiy ofinfection of 1-year old saithe

with Anisakis simplex; mean±S.D.

(time scale is discontinous).

Tættleiki av infektión av hvalormi, Anisakis simplex, í

1-ára gomlum seiði. Tølini eru meðaltøl ± standard-

frávik; allir mánaðir í ári eru ikki umboðaðir.

Fig. 5. b. Intensitiy of infection of2-year old saithe

with Anisakis simplex; mean+S.D.

(time scale is discontinous).

Tættleiki av infektión av hvalormi, Anisakis simplex, í

2-ára gomlum seiði. Tølini eru meðaltøl ± standard-

frávik; allir mánaðir í ári eru ikki umboðaðir.

ing the two studies. At the end of 1996 the

1-year old saithe had significantly higher

levels of prevalence of infection (70 %)

than the 2-year old saithe had at the start of

the year (from 18 to 40% in January to

March) (Figs. 4 a, b). These results suggest

that the levels of infection vary between

different age classes from different years.

But they also indicate a relative change (in-

crease) in the years 1995 and 1996. This

observation is apparently following the

changes in abundance of mesozooplankton,

which was inversely related to the primary

production around the Faroe Islands in the

same period: a steady increase from 1990

to 1995, but much lower in 1996. (Gaard,

1996a; Gaard et ai, 1997). How can this

correlation between primary production,

mesozooplankton and parasitic infection be

explained?

The intermediate hosts for Anisakis sim-

plex are the euphausiaceans Thysanoessa

inermis, T. longicaudata and Meganycti-

phanes norvegica (see eg. Polyanski, 1966;

Smith, 1971, 1983; Højgaard, 1995b). Ac-

cording to Mauchline (1980) T. longicau-

data and M. norvegica are omnivores and

Beyer (1992) found M. norvegica to be an

important predator on Calanus finmarchi-

cus, which is the most abundant zooplank-

ton species on the Faroe Shelf (Gaard,

1996b).

Køie (1993) suggested calanoid cope-

pods as transport hosts for A. simplex, to

euphausiaceans and successfully infected

Acartia tonsa with A. simplex larvae. In the

experimental work of Højgaard (1995b)

Calanus finmarchicus was not found to be

a transport host for A. simplex, however.

Einarsson (1945) reported juvenile stages

only of T. longicaudata and M. norvegica

from Faroese coastal waters. Otherwise no

data seem to occur on the distribution of eu-

phausiaceans at the Faroes. The prevalence

of infection with Anisakis in euphausi-

aceans usally is low (Smith, 1983). It is

thus difficult to judge the exact importance

of the euphausiacean intermedatiate hosts