Fróðskaparrit

						58

SEASONAL CHANGES IN THEINFECTION OF YOUNG SAITHE

Introduction

Among the Faroese public as well as in oth-

er fish-consuming countries it is a general

view that the infection of fishes with nema-

todes exhibits seasonal changes (pers. ob-

servations). It is well documented that

prevalence of infection (percentage infect-

ed) and intensity of infection (mean num-

ber of parasites per infected fish) with

Anisakis simplex third stage larvae is in-

creasing with age for several fish species

(Wootten, 1978; McClelland et aZ.,1990).

Thorough work dealing with parasites of

saithe like that of Scott (1985) or Polyans-

ki (1966) did not examine the effect of sea-

sonality in detail, however.

The investigations of fishes for nema-

todes usually are made in age-classes enter-

ing commercial fishery, leaving the

younger age-classes relatively unexam-

ined. Juvenile and young saithe is staying

close to the coast, while the maturing age-

classes do emigrate to deeper waters (Joen-

sen and Táning, 1970). This makes it diffi-

cult to catch juvenile or young físh with the

common research vessels or commercial

fishing vessels.

Infection of adult saithe from Faroese

Waters with A. simplex in fillets was exam-

ined by Højgaard (1995a; b) and the pre-

sent study is a continuation of this work.

The aim was to search young saithe for par-

asites and to relate the infection with time

of the year.

Materials and methods

Sampling

Young saithe was caught close to Leirvík,

Faroe Islands from Jan to Dec, 1996 (Table

1). The sampling area is presumed to repre-

sent common Faroese bays and sounds,

which are characterized by severe tidal cur-

rents, giving ideal conditions for young

saithe to gather in schools and browse on

the incoming zooplankton. The fish was

caught at dawn with nylon longlines, opera-

ting from a traditional Faroese fishing boat.

The distance to the coast was 50-300 m,

bottom depth 10-60 m and físhing depth

were approximately 1-7 m. Immediately

after the sampling, the físh was weighed,

the length was measured and the otoliths

were removed. The whole fish were deep

frozen in separate plastic bags at -18 °C.

Table I. The samples of saithe froin the Leirvfk area, January-

December 1996, positions close to 62°15' N, 06°40'W.

Talva 1. Tikin sýni av seiði úr Leirvíksfirði frá januar

til desember 1996

Date	Number of saithe

05.01.96	28

26.01.96	47

17.02.96	45

23.03.96	75

25.05.96	47

24.08.96	77

26.10.96	78

14.12.96	33

27.12.96	28

Total	458

Digestion

After a thawing period of 6-12 h, butterfly

fíllets were cut from the saithe and the

stomachs were refrozen. Digestion of the

fillets without skin and the viscera in

pepsin-hydrochloric acid were made in 2 L

or 1/2 L beakers, respectively, at 37 °C for

3-6 h, pH 1-2 (Smith and Wootten, 1975).

The fillets were digested with continuous