Fróðskaparrit

						ARSTIDARBROYTINGAR I RUNDORMA-INFEKTION I SEIÐI

65

of A. simplex, but the general biology and

the population dynamics of the intermedi-

ate hosts are of obvious importance. If the

population of the euphausiacean intermed-

itae host are at low level the possibility also

will be low for the Anisakis larvae to reach

the saithe through infected euphausiacean.

If the euphausiacean population are at a

high level it will become more likely for the

saithe to be infected by the Anisakis larvae.

The preconditions for this assumption is a

steady supply of Anisakis-eggs from the fí-

nal host, the whales, and subsequent hatch-

ing of larvae and infection of the euphausi-

aceans. Due to the high turbulence in the

water on the Faroese Shelf, Anisakis-eggs

and larvae must be assumed to follow the

same patterns of total mixing as do the nu-

trients (Hansen, 1992).

As the long fínned pilot whale, Globi-

cephala melas, is the most common whale

in Faroese waters (Bloch, 1996) it may be

considered as the major source of Anisakis-

eggs, delivered with the whale faeces and

originating from sexully mature females

within the stomach of the pilot whales

(Raga and Balbuena, 1993). A measure of

the number of visiting pilot whales is the

number of whale killed in the traditional

Faroese whale hunt called »grindadráp«,

taking only the schools coming close to the

coast. According to unpublished data from

Bloch (1997) the number of pilot whales

landed in the years from the 1990 to 1996

were close to the long-term total mean of

844 per year (Bloch, 1996) except the year

1995:

Year	No.	ofpilot

	whales	landed

1990		917

1991		722

1992		1572

1993		804

1994		1201

1995		228

1996		1524

Judging from this data series it is unlikely

that the supply of Anisakis-eggs from pilot

whales has been declining in the period of

the observed decline (and rise) in the

Anisakis-infection of saithe.

Aspholm et al. (1995) suggested that

only a small population of seals was re-

quired to maintain a high level of infection

with Pseudoterranova decipiens in cod,

Gadus morhua. Apparently this is also the

case for the Anisakis-p'úot whale system.

Whether or not many or few whales are vis-

iting presumably they are able to shed

enough number of eggs to enter the food

web through the euphausiaceans to saithe.

Encapsulated nematodes in físhes gener-

ally are considered to live for months or

years. In this study of 1-2 year old saithe

calcifíed nematode larvae, presumably

killed by the immune response of the host,

were rarely observed. The encapsulated ne-

matodes found of A. simplex, P. decipiens

and Contracaecum sp.) are thus following a

stable, secure route towards reaching their

fmal hosts through the infection of saithe,

while the non-encapsulated larvae and

adults of Hysterothylacium aduncum, (a

low percentage of larvae were found encap-

sulated), Cucculanus sp. and Echinorhyn-