INTERNATIONAL COUNCIL FOR
THE EXPLORATION OF THE SEA
C.M. 1988/H:23
Pelagic Fish Committeel
Theme Session 0
ANISAKIS LARVAE (NEMATODA: ASCARIDIDA)
IN MACKEREL, (SCOMBER SCOMBRUS L.) IN
ICES SUB-AREAS IV, VI. VII AND VIII
IN 1970-1971 AND 1982-1984
by
A. Eltink
Netherlands Institute for Fishery Investigations
P.O. Box 68, 1970 AB IJmuiden .
The Netherlands
INTERNATIONAL COUNCn.. FOR
THEEXPLORATION OFTIIE SEA
C.M. 1988/11:23
Pelagic Fish Committee
Theme session 0
Anisakis Larvae (Nematoda: Ascaridida). in
- Mackeret, Scomber scombrus L., in leES
Sub-areas IV, VI; VII and VIII in 1970 • 1971
and 1982 • 1984.
by
•
A. Eltink
Netherlands Institute for Fishery Investigations
P.O. Box 68. 1970 AB IJmuiden
The Netherlands.
RESUME
En 1982-1984 des recherehes ont ete menees sur Anisakis en tant que marquc
biologique ehez le maquereau pour determiner l'origine et le trajet migratoire du
maquereau du sud de la Mer du Nord. Les donnees partielles eollectees a eelle fin
ont fait l'objet d'une precedente eommunication. Les. resultats. complets des
recherehes sur l'Anisakis dans les echantillons de maquereau. reeoltes. dans les
sous-zones CIEM IV. VI, VII et VIII ainsi que les resultats de reeherches de la
periode anterieure 1970-1971 sont donnes dans la presente eommunication.
L'infestation est beaucoup moins liee a la longueur' et a l'age du poisson qu'on ne
pourrait le prevoir en faisant l'hypothese d'une infestation par An isa k i s
augmentant annuellement.
L'abondance d'Anisakis ehez le maquereau alleint un niveau maximal des l'age de 3
a 5 ans. Ceci est probablement da a une resistance acerue de l'höte aux noevelles
invasions par les larves d'Anisakis plutöt qu'a une perte de larves. La mortalite des
Mtes moyennement .et fortement infestes ne peut expliquer eetle forte diminution
des infestations annuelles par Anisakis chez les groupes d'ages les plus vieux. Le
taux d'infestation au cours de la (ou des) premiere(s) annee(s) de vie du maquereau
determine probablement le taux d'infestation des poissons liges et determine
egalement le temps necessaire au developpement d'une resistance aux nouvelles
invasions de larves. L'abondance d'Anisakis chez le maquereau de la Mer du Nord a
approximativement double entre le debut des annees 70 et le dehut des annees 80.
.
'
L'abondance d'Anisakis ehez le maquereau du sud de la Mer du Nord a relativement
moins progresse au eours de la meme periode. Dans la population de maquereau de
l'ouest. on note un aeeroissement de l'infestation de sud au nord. entre mai ct
juillet.
En 1982-1984. la prevalenee ct l'abondance les plus grandes apparaissent dans la
population de maquereau de la Mer de Nord tandis que prevalence et abondance les
plus faibles apparaissent chez le maquereau du sud de la Mer du Nord et du Golfe de
Gascogne.
L'abondance de L'Anisakis dans la population de maquereau de l'ouest est
moitie moindre que eelle du maquereau de la Mer du Nord.
a peu
pres
1
-.
INlERNATIONAL COUNCIL FOR
TI-IE EXPLORATION OF THE SEA
C.M. 1988/H:23
Pelagic Fish Committee
Theme session 0
larvae
(Nematoda: Ascaridida)
in
Ariisakis
Scomber scombrus L.,
in leES
MackereI,
1971
Sub-areas IV, VI, VII and VIII in 1970
and 1982
1984.
lI
•
~
I
•
by
A. Eltink
Netherlands Institute for Fishery Investigations
P.O. Box 68, 1970 AB IJmuiden
The Netherlands.
."
ABSTRACT
•
In 1982-1984 investigations were carried out to investigate the ongm and
migration of the southem North Sea mackerel using Anisakis as a biological
tag in mackerel for which purpose only part of the Anisakis data were
presented earlier. All results of these investigations on Anisakis in
mackerel sampIes, collected in leES Subareas IV, VI, VII and VIII together
with results of investigations in an earlier period 1970-1971, are presented
in this paper. The infestation is much less related to the length and age of
the fish than expected assuming an increasing yearly Anisakis infestation.
The abundance of Anisakis in mackerel reaches as early as age 3 to 5 the
highest level. This is probably due to an increased host resistance to newly
invading Anisakis larvae rather than the loss of larvae: Mortality of the medium and high infestated hosts can not explain this sharp decrease in the
yearly Anisakis infestations for the older age groups. The level of Anisakis
infestation during the first year(s) of life of the mackerel determines
probably the level of infestation when they are old fish and also determines
the time needed to develop a resistance to newly invading larvae. The
abundance of Anisakis in North Sea Mackerel doubled approximately from
the early seventies till the early eighties. The abundance of Anisakis in the
mackerel from the southern North Sea Mackerel increased relatively less
during these time periods. Within the Western Mackerel population there is
a gradual increase in the infestation {rom south to north from May to July.
In 1982-1984 the highest prevalence and abundance occurs in North Sea
Mackerel population. The lowest. prevalence and abundance occurs in
mackerel from the southern North Sea and the Bay of Biscay. The
abundance of Anisakis in the Western Mackerel population is about half of
ihe infestation in the North Sea MackereI.
2
.
,
INTRODUCTION
I.
~
-.
Two mackerel ,(Scomber scombrus L.) populations occur in the northeast
Atlantic: the Western Mackerel and the North Sea Mackerel stocks (Anon.•
1988). The ,Western Mackerel spawn in the Celtic Sea and Bay of Biscay.
while the North Sea Mackercl spawn in the central North Sea. After
spawning thc main part ,of both populations migrate to the same feeding
grounds in the northem North Sea, which is a very important feeding area
for the mackerel. Euphausiids, copepodes and fish are the most important
food (Mehl and Westgaard, 1983 and Anon., 1984). The mairi infestation of
mackerel with laivae of Anisakis simplex (Nematoda: Ascai-idida) (Pippy and
van Banlling. 1975) takes place in the northern North Sea (Smith. 1983a).
The life cycle of Anisakis goes from the final, host; which contains the
adults, through an intermediate and a. paratenie host. containing the larval
stages and back to the final host again. Intermediaie hosts are crustaceans,
mainly euphausiids (Smith, 1983a and Smith 1983b). Paratenie hosts of
Anisakis are in most cases Teleostci. like herring. horse mackerel and
mackerei. eating these euphausiids. Final hosts ,of Anisakis are mainly
Cetaceans (van Banning and Becker, 1978), feeding on these fish. In. the
final hosts the adult Anisakis produce eggst which enter sea water alorig
with the faeces 0[- the, marine mammalian final host.
In 1982-1984 irivestigations were, carded out on Anisakis as ci biological tag
in mackcrCl to find out the origiri and migration of the southem North Sea
mackerel in rCIation to the North Sea and Western Mackerel populations for
which purpose only part of the Ariisakis data were presented earlier. Thc
southern North Sea mackercl should be regarded as an overflow of mackercl
of thc Wcstcrn Mackcrcl population to the North Sca Mackcrel population
(Eltink et al.. 1986). This group of mackerel , .which spawns in the North Sea.
is born and has partly spent the juvenile phase in the western, areas and
probably does not feed in the northern North Sea and has thcrefore a
characteristic low infestation of Anisakis. All results of these irivestigations
on Anisakis in mackerCI. sampies. collected in ICES Subareas IV. VI. VII and
VIII togethei' with results of investigations in an, earlier period 1970-1971
(collected by dr P. van Banning) are listed, in this paper. The prevalence.
abundance. mean intensity and degree of infestation of Anisakis ,in
mackerel by area and by length or age of the fish oe only by area in ICES
Sub-areas IV. VI, VII and VIII in the two time periods 1970-1971 and 19821984 are presented. Instead, of by area this information is also given for the
Western and North Sea MackerCI popuhition and, the mackerel from thc
southern North Sea. Furtherniore. the Anisakis distributions by area arid
time within the western and North Sea area are examined. Infesiation by sex
was examined, because there was a suspect that thc male sex would be more
prone to infestation with Anisakis than the female sex~ for males ,mature
earlier and thereforc migrate at a younger age to the fcedirig grounds in
the northern North Sea. The degrec of Anisakis infestation is, investigated
in relation to the loss of coridition of the fish. Hypotheses are given for the •
mechanisms preventing an excessive infcstation and thc determination of
thc irifcstation level.
~
~ , , . .
l\IATERIAL AND METHODS
During thc period 1970-1971 1064 mackerel and during the period 1982-1984
3008 maekerel were examined ror Anisakis larvae in ICES Subareas IV, VI.
VII and VIII.
Table 1 shows the 'number of· mackereI. which were examined for Anisakis
änd which were aged. by year and by ICES Division or Subdivision. These
3
<'
•
sampled areas are shown for both time pei-ioos' in respectively Figur~s 3, and
4 (thc large ICES Divisions IVa, IVb and vhi have been divided in smaller
Subdivisions, which have additions like e.g. 'SW' for southwest ete.).
In 1970 ~md 1971 aselect sampIes were taken from mackerel catches of
commercial arid research vessels in ICES Divisions IVa" VIa and VlIg (Table
1). All fish were examined for Anisakis larvac and of these fish sex,
,
maturity. age, weight and length were estimated.
In 1982-1984 part of the sumples of the markei, sampling programme were
used for counting Anisakis together with sampies ; from research vessels.
These sampIes . were i-epresentative for the length and age composition of
the catches. These fish were, examined, for Anisakis larvae and the sex;
maturity, age, wCight and length were estiinated. Of some additional sampIes
of research and commercial vessels. being representative, for the length
distribution of the caich, only the length was estimated and thc number of
Anisakis coimied.
.
Two methods of counting the number of Anisakis larvae were used:
* The 'Naked-eye' counting method. The visceral mass of each mackerel
separat61y was examined very careftilly for nematodes, which were then
identified and counted. This method, was uscd in 1982 and 1983, because also
thc pleroccrcus of Grillotia angeH (Cestoda: Trypanorhyncha) (MacKenzie.
1981) was coiHited then.
.
'
'
* The citi-ic acid - pepsin digestion method (Roskam, 1966). Anisakis larvae
,were recovered by citric acid - pepsin digestion of the, whole, visceral mass
"
'
,
•
"
0
"'.
of each mackerel separately dunng 24 hours at 37 Ci . after WhlCh the
digested mass was sieved over a blaek Ix 1 mm metal-:wire sieve. The
nematodes remaining on the sieve were identified and counted. This
method was used in 1970. 1971 and 1984.
,
•
',"0
All fish in Sub-area IV north of latitude 55 N were assumed to belong to the
North Sea Mackerel population, except those caught from July, to Oetober.
•
•
' ' ' .
0
'
,"
All flSh In Sub-area IV south off latItude 55 N were assumed to belong to the
maekerel from the southcm North Sea. All fish in Sub-area VI. VII' arid VIII
were assumed to betong to the Western Mackerel population, except those
caught in VIa NE in November. December. January, February or March. ,
Fish of a certain age and length have been combined iri groups in order to
have enough fish per age or, length group. The, following age groups were
used: 1-3, 4-6, 7-10. l1+(age 11 and older). The following length groups were
used: 20.0-24.9 cm, 25.0-29.9 cm; 30.0-34.9 cm, 35.0-39.9 cm, 40.0-44.9 cm und
45.0-49.9 cm.
,
The foIlowing ecological terms in parasitology, recommended by an ad hoc
committee of the Ameriean Soeiety of Parasitologists (Margolis et al., 1982)
~u~in~s~~
,
.
Number of individuals of a host species infected
PREVALENCE (%) =
with
particular parasiie species * 100 I
Number of hosts examiried
ABUNDANCE =
Total number of individuals of a particular
parasiie species in, a sampIe of hosts I Total
number of individuals of thc host species
(infected + uninfected) in the sampie. (= Mean
number of individuals of a particular parasite
species per host examined)
MEAN INTENSlTY =
Total number of iridividuals of a particular
parasite species in a sampie of, a host species I
number of infected individuals of the hast
spccies in thc samplc. (=, Mciin numbcr of
i~dividuals of a particular, parasite species per
infected hast in a sampie)
.
a
I
4
The infestaied mackerel were divided in three clltegories for indicating the
DEGREEOF~TATION:,
,
LOW degree of infestation ,
1-15
Anisakis larvae per fish
16-45
Anisakis larvae per fish = MEDIUM degree of infestation
> 45
Anisakis larVae. per fish = HIGH degree of infestatiori,
The percentage of fish with a HIGH, MEDIUM and LOW infestation in a
certain area or for a certain population or for a certain age or length
group add up to 100%. The calculation of these three degrees of infestation
(%) is notpresented in the Tables 3 - 8; when there were less than 5
infestated fish.
=
RESULTS
Individual worm burden ranged froin 0 to 378. The frequency distributions
of Anisakis larvae', are skCwed as is shown as an example for age group 5 of
North Sea Mackerel in 1983-1984 in the text table below :
0-4 . 5-9 10-14 15-19 20-24 25-29 30-34 35-39 40·44 45-49 >=50
10
7
5
2'
6
3
3
2
1
5
Frequency 7
A./fish
•
"
Table 2 shows the prevalerice (%). mean intensity and abundance of
Anisakis. in mackerel and the riumber of fish, which were examined, by
year, by ICES Division or by Subdivision, by month and by rectangle.
Information on the assumed (sub)population identity is added in this Table
2. The information of this table is presented resiJectivdy in Figure 1 and 2
for the two time periods 1970-1971 and 1982-1984. These figures show the
ICES statistical rectangles, which have been sampled during both periods.
The abundance. of Anisakis in mackerel increased in the northern North
Sea from 1970-1971 to 1982-1984. Thc. coverage of sampling in the western
area was very limited during 1970-1971. The only sampling was done in
Subdivision Via NE, which is very near to the northern North Sea area, arid
in Division VIlg, .which is more or less a nursery ground. Therefore, no
information is availablc on the changes in the Anisakis infestation in the
western areas.
.
.
.
.' ' .
Table 3 shows the total number of mackerel examined for Anisakis, the
number uninfestated arid infestated fish; the prevalencc, the me an
intensity. abundance and the degree of infestation in the infected, fish. (%)
by Division or by Subdivision for two timcperiods 1970-1971 and 1982-1984.
Figure 3 and 4 show the prevalencc, the abundance of Anisakis in mackerel
and number of fish examined by Division or Subdivision for respectively
the two time periods 1970-1971 and 1982-1984..Thc highest abundance ,of
Anisakis in mackerel occurred in ,1970-1971 ,in Subdivisions IVa SE and NE
and in 1982-1984, not only in IVa NE+SW+SE and IVb E+W, but also in
Divisiori VIIc. ,
,'.
.' "
.'
Table 3 is combining all age and length groups, but Table 4 and 5 show the
same information by length groups respectively by age groups in order. to
detect any reI:ition between infestation ,and the length or age of the fish.
The prevalence (%) .increases with the length and age of the. mackerel. The
abundance. and mean iritensity increases with lerigth arid age of the
mackeret, but seem to decrease orten for the largest and oldest fish.
. Table 6 and 7 show the total nuinber of mackerel examined for Anisakis~ the
riumber uninfestated and infestated fish, the prevalence, the mean
intensitY"aburidance arid the degree of infestation in the infected fish (%)
for the .Western Mackerei. the North Sea Mackerel and the. mackereI, from
the southern North Sea for thc: periods 1970-1971 'and 1982-1984 by length
group (Table 6)and by age group (Table 7). Figurc. 5 shows in 'most cases an
iricreasing abundance of Anisakis in inackerel for each age group of ihe
I
5
•
North Sea _Mackercl popuiation and the macTcerel from the southern North
Sea from 1970-1971 to 1983-1984. The relative high abundance of Anisakis in
1-3 year old southern North Sea mackerel in 1970-1971 seems unrealistically
high.
.
_ _
_
Figure 6 lmd 7 show the abundance of _Anisakis in mackerel in the North Sea
and Western Mackerel population and in the mackerel from _thc southern
North Sea and thc Bay of Biscay, by length group in 1982-1984 arid by age
group in 1983-1984. Thc smallcst arid youngest, fish had, the lowest
infestatiori with
Anisakis. The 4 year and oldcr fish do not show a clear
increasing abimdancc of Anisakis, but thc abundance fluctuates more or
less around a certain level. The abundancc or mean intensity by age group
do not show an increase as oriewould expect with an increasing food uptake
of the inackerel, but a rapid increase for young fish, nearly no further
iricrease for older fish and cven a decrease for the oldest fish (Table 4 and 5
and Figures 5, 6 arid 7). Thc prcvalencc rates incrcased for the Western and
North Sea mackercl populations between 1970-1971 and 1982-1984 (Table 6
and 7). An unexpected high prevalence arid abundance _ were cstimated for
the smallest and youngest mackerel from the southerri North Sea in 19701971.
Table 8 shows the total riumbef of mackerel examined for Anisakis, the
riumber uninfestated rind irifcstated fish, thc prevalcnce, the mcan
intensity. abundance and the dcgree of infestation in the infected fish (%)
for thc Western Mackerei, the North Sca Mackerel rind, the mackerel from
the southern North Sea by sex and sexcs, coinbined in ,19"83·:1984. Therc is no
clear diffefence between male and female mackercl in relation to Anisakis
infestation, although the, prevalencc and aburidancc of. Anisakis in Western
Mackerel and mackerel from thc southern North Sea is just a littlc higher
for males than for females.
'
Figures 8, 9 and 10 demonstrate the differences in abundance of Anisakis in
mackerel depending orithe time and thc area of sampling. Figure 8 shows
the abundance of Anisakis in mackerel in the North Sea area from June to
July in 1983 and 1984. Thc highesi infestation of 1-3 year old rriackerel
occurs in thc northern North Sea. Four year and older fish in thc northern
and central North Sea have a much higher infestation than those from the
southem North Sea. Thc abundance of. Anisakis decrcases also often for the
oldest arid largest mackerel in these figures. _ Figure 9 shows the abundance of Anisakis in the mackerel in the western
area from May to July in 1983 and 1984 in three different areas. From north
to south the abundance of Anisakis in each age group of mackerel
decreases, especially the abundance of Anisakis in the juveniles (age 1-3).
The abundance of Anisakis in mackerel in Divisiori VIIj decreases within
each age group duririg (pre)spawning froin ,March to Mayas is shown in
Figure 10. The most remarkable change is the decrease in infestatiori of 1-3
year olds.
,
Figure 11, 12 and 13 show, the cumulaiive percentage of mackerel having a
low , medium and high Anisakis infestation by age group iri 1983-1984 for
respectively the North Sea, and Western Mackerel and. the mackerel from
the ,southern North Sea. These figures demonstrate that the percentage
distributions of the degrees of Anisakis infestation do not change any more
after age 4 of the mackerel. These percentages do not iriclude uninfectcd
fish.
,
....
"
'.
'
.'
,3
-,
The mean COndltlOn factor ( K = 100 * welght I length ) of the Western
Mackerei, North Sea Mackerel and the mackerel from the southern North
Sea in 1983-1984 in relation to ihe riumber of Anisakis' larVae present is
shown iri Table 9. There is no correlalion between increasing degree of
infestation and loss of condition of the fish. However. a positive correlation
seerris to exist between degree of infestation _and the conditiori of the fish.
6
DISCUSSION
•
-.
The skew frequency distributioris of Anisakis in mackereI. are also commori
in herring (van Banning and Becker. 1978) rind. blue whiting (Smith and
Wootten. 1978). Thc overdispersion of. Anisakis in rriackerel is typical of
almost all parasite frequency distributions studied in natural populations
(Anderson. 1978).
.
Once the Ariisakis larvae have entered thc visceral cavity or imisculature
they quickly become encapsulated and remain immobile while fish is alive.
Larvae do not penetrate the viscera .but are encapsulated superficially.
Thus. although the surface of the liver may be covered with larval
nematodes its internal structure and functioning are probably unimpaired
(Smith and Wootten. 1 9 7 8 ) . .
.
For counting Anisakis larvae the pepsiri digestion method is. preferable to
the naked-eye counting method. because inaccuracy may arise especially
when the fish is not fresh-caught or when thawing after freezing causes
'deliquescerice' in the body cavity (van . Banning and Becker. 1978). As a
consequence of counting only in the body cavity coritents. nematodes in the
musculature are missed. The tendency' of each. Anisakis to bore into the
musculature of herring has shown to be constant in thatapproximately one
in 130 larvae was found in this circumstance regardless of the age or the
length of the host (Davey. 1972). Therefore. the number of Anisakis larvae.
in the musculature of the mackerel missed by this inethod. is probably
irrelevant.
Smith (l983b) stated that euphausiids in the North-East Atlantic. and
northerri North Sea. and perhaps universaly. are major hosts of Anisakis
simplex. The Anisakis larvae are found in the followirig euphausiids species
in the northern North Sea: Thysanoessa inermis. T. longicaudata. T. raschii
and
Nyctiphanes
couchii. (Sinith;. 1983a)
and
probably
also
Meganyctiphanus norvegica (Sniith. 1971). which' is the most important
species of the euphausiids in the mackerel diet (Mehl and Westgaard. 1983).
Smith (1983a) had the impression that the. infected euphausiids were most
common in the offshore region at depth between 100. arid 200m in the
northern North Sea as shown in Figure 14. No individual euphausiid
harboured more than one parasite. In the northern North Sea the
distribution was extremely patchy; the prevalence rate for iridividual
euphausiid species in individual sampIes was in T. inermis from 0 to 4.0%. in
T. longicaudata from 0 to 1.0% and in T. raschii from 0 to 1.3%. but an
exceptionally high rate of 78% was recorded. Larval Anisakis occurred in
0.42% of the examiried euphausiids (109 individuals out of 26058 euphausiids
of five species). .
.
The abundance of Anisakis in mackerel doubled approximately in the North
Sea Mackerel population from 1970-1971 to 1982-1984 (Figure 5 and Table 6
and 7). This increase was less in the mackerel from the southern North Sea.
The infestation of Anisakis in. 1-3 year old southern North Sea mackerel was
relatively high in 1970-1971. because the last strong year cIass 1969 of the
North Sea MackerCI population, had an expanded distribution to the south.
The sampling of mackerel during 1970-1971 was not adeqmite enough to
describe any change in thc abundance of Anisakis in mackerel . in the
western area or in' the Western Mackerel population betweeri both. periods.
It appears that in June and July the southern part of the northern North
Sea area the highest abundance of'"Anisakis in mackereI. occurs. although
the number of. fish examined is rather low (Figure 8). Thc mackerel from
the . southern North Sea has a mueh lower abundance. of Anisakis.. The
southern. North Sea mackerel should be rcgardcd. as an overflow of mackerel
of the Western Maekerel population to the North Sea Maekerel population
(Eltink ci a1.. 1986). This group of mackerei. whieh spawns in the North §eä.
7
. ..
"
•
is born and bas partly spent tbe juvenile pbäse in tbc western areas, does'
not fced in tbe nohbern North Sea and bas tberefore a cbaracteristic low
infestaiion of Anisakis.
The juveniles of tbe Western MackerCl population, growing up, in. tbe
western area, bave a relatixely high infestation compared witb juveniles
from the English Channel, the Day of Biscay and southein Nortb Sea. Along
tbe edge of the continental sbelf there is an increase in the infestation of
juvenile fish froin south to north from May to July (Figure 9). Probably the
infestation of juvenile mackerel increases from south to north. In the
eighties there has bcen ci partial shift of western juvenile mackerel from
the Western English Cbannel to tbe west. of Scotland (Anon., 1988). The
infestation of these juvenile Western Mackerel will probably increase~
wben more juveniles are growing up to west of Scotland, because the
infestation in tbe western Englisb Cbannel would be mucb lower.
.
During the (pre)spawning season (March-May) the abundance of Anisakis
in Westerrl Mackerel decreases (Figure 10) as a result, of the age-size
succession in spawning of the mackerel. The older and targer fish spawn
earlier andwithin an age group the relatively large fish spawn earlier.
After spawning. they migrate to the northern North Sea for feeding. The
largest fish within an age group mature earlier and therefore spawn
earlier and mi grate earlier to the. feeding area in the northern North Sen,
where they get a higher infestatiori compared with the relatively sm aller
fish . of the same age group, remaining in the western areas or migrating
riorthward later (Eltink, 1987). The relatively sharp decrease. in infestation
of the yourigest fish from March to May is caused by an immigration of low
infestated
first time spawners in. the spawning area.
Iri the Western Mackere1 population seems to exist a positive correlation
between tbc degree of Anisakis infestation and the condition factor of the
fish as a result of the age-size succession in spawning and migration. of
inackerel
(Eltink, 1987); the largest fish within an· age group are probably
those fish ,having the highest condition faetor.
. .
Males of the 2 year old mackerel mature at a. smaller length than females,
which causes a relatively higher abundance of Anisakis in these 2 year old
males in the spawning area (Eltink, 1987). Therefore, one would expect a
higher infestation in male Western Mackerel arid male mackerel from. the
southerri North Sea than for females, because these males start their
feeding migration to the North Sea earlier compared to females. Dut there
was only a slight higher infestation in these males.
.
Figure 5, 6 and 7 show that only the juvenile maekerel (age 1-3 and length
dass 20-24 and 25-29) of the North Sea MaekerCI population have a very
high abundance; which is nearly as high. as the older. and larger fish,
because these juveniles grow up. in the North Sea, which is the main
infestation area. Tbe juvenile North Sea Maekerel; growing up in an area
witb a risk of many infestations in a relatively short pedod, probably gets
a high number of infestations before they even have been able to develop a
presumptive resistance to newly invadirig larvae. The juvenile .Western
MackereI, growing up in an area with a risk of much less infestations
in
the same period, probably gets a low number of infestations
before they
develop a presurriptive resistance to newly invading larvae. It takes a langer
period for the Western Mackerel to develop this presumptive resistance
compared to the North Sea Mackerel. This implies that the .abundance of
Anisakis in aduIt mackerel is dependent on the Anisakis infestation
pressure dudng the juvenile period.. It is even possible then that within the
population .. the abimdarice
of
Anisakis in mackerel decreases with thc age of
the, fish. It implies .that the older fish' in the population have been spending
tbeir first years of live in ari area, wbere tbey got a low infestation.
According to. Smith and ,Wootten (1978) there was an iridication .iri same·
sampIes of blue whiting that the level of infestaiion decreased in older fish.
8
Also Gieds (1981) found that the infestation in the very large arid old blue
whiting was decreasingwith the length of the fish. This decrease in the
level of infestation for older fish can also be observed in mackerel (Tables 4
- 8 and Figures 5 - 10). Thc levcl of Anisakis infcstation in mackerel in thc
carly scvcnties was indecd a)Jout. half of the .recent level, which means that
the hypothesis above is in agreement with the observations in blue whiting
and mackereI.
Thercforc, thc abundance of Anisakis in Western Mackerel
incrcascd from thc carly scventies tiII thc early eighties, because the oldest
(age 11+) fish have a lower infestation than the younger fish (age 4-10).
In the text table below is shown the growth in length and weight by year of
thc mackerel in the middle of the Year. Mackerel eat abatit 2.5 times their
own body weight each year (Anon., 1984) and about 1/3 of their diet in the
northern North Sea consists of euphausiids (Mehl and Westgaard, 1983).
Assuming only 70% of. their food consumption is eaten in the northern
North, thc annual food intake of euphausiids in the northern North Sea can
be estimated and is about 60% of their own body weight. The mean weight of
an individual M. riorvegica eaten by mackerel estimated during the stomach
sampling programme (Anon., 1984) was 0.08 g and the mean weight of both
T. inermis and T. raschii 0.02 g (pers. comm. Sigbjprn Mehl). The mean
weight of an individual. euphausiid was assumed to be 0.06 g, because the
most important cuphausiid in the diet of the mackcrel was M. norvegica.
This mean weight can bc used for estimating roughly the numbcr of
euphausiids eaten each year by one individual mackerel in a certain age
group from .the weight of euphausiids eaten by each mackerel in
certain
agc group. The percentage of infected euphausiids eaten is assumed to bc at
least 0.5% of thc total number of euphausiids eaten in the northern North
Sea, becausc thc prevalence rate was al ready 0.42% in all sampIes taken in
thc total area as shown in Figure 14 and becausc thc biomass of Thysanoessa
species is much lower to the west of Scotland than in the northern North
Sea (Lindley, 1977). The theoretical cumulative infestation of Anisakis in
mackercl ean be estimated, assuming each infeeted euphausiid eaten
aceounts for one eneapsulated Anisakis in the body eavity of the mackerel
and assuming that Anisaki.s larvae live as lang as their paratenie host (see
text table below).
a
•
Age of
Length
mackerel of fish
Weight
of fish
0
1
2
3
4
5
6
7
8
9
10
39
125
225
318
394
453
497
528
550
566
576
15.5
22.8
27.7
31.1
33.4
35.0
36.1
36.8
37.3
37.7
37.9
Weight of
Euphausiids
eaten (g)
24
75
135
191
237
272
298
317
330
339
'346
Number of
Euphausiids
eaten (N)
Infestations Theoretical
concerning cumulative
year
infestations
390
1250
2250
3180
3940
4530
4970
5280
5500
5660
5760
2
6
11
16
20
23
25
26
28
28
29
2
8
19
35
55
78
103
129
157
185
214
The. number of theoretieal eumulative infestatioris are eompared' to the
observed values of the North Sea and Western Mackerel populations as is
shown in· Figure 15. The number· of infestations each year is linear related
to the food consumption of the maekerel,. but the observed abundanee of
9
Anisakis in both populations remain [ar beldW the expected values of the
theoretieal eumulative infestations and show evidenee of nearly no more
infestations after the age of 3 or 5. This much lower observcd abundancc
ean be explained by a possible inercased host resistance to ncwly invading
larvae as suggested earlier as the most likely possibility. This host resistance
to newly invading larvac can "be developcd either by .the fish itself or by the
encapsulated Anisakis larvac themsclves. Any change in the feeding habits
of about 4 year and older mackerel should be excluded as possibility on
aceount of the results of thc stomach sampling project (Anon., 1984).
Furthcrmore thc mortality of the medium and high infected paratenie hosts
should be eonsidered as a possible cause of this mueh lower observed than
expected abundance, but the number of Anisakis infestations did not have
an apparent effeet on the eondition of the mackerel not even at very heavy
infestation levels. Also Smith and Wootten (1978) did not find any
correlation between the degree of infestation and the loss of condition of
the blue whiting. Even, when a high degree of infestation would not affect
the eondition of the fish, one would expeet that fish with a higher degree of
infestation would suffer a higher mortality than those fish having a lower
degrce of infcstation. This would imply that the cumulative pereentage
distribution (Figures 11, 12 and 13) would change to relatively more medium
and lcss low infestatcd fish. However, these. percentage distributions do
praetically not change for the 4 year and older fish, which supports the
hypothesis of the host resistanee. Furthermore the loss of previously
established worms could also cause this much lower observed than expectcd
abundance of Anisakis in mackcreI. This would imply that the established
larvae should live only 3 to 5 year in order to get a very slowly inereasing
abundance by age or length and that in older fish about 30 nematodes
should degenerate each year (see text table above). Fish, examined with the
naked-eye counting method, did not show evidence of degenerating
Anisakis larvae in high numbers. Therefore, the host resistance is still the
most plausible explanation for the observed characteristics of the Anisakis
infestations in mackereI.
I gratefully acknowledge the help of Miss Martine Warmerdam and Arjan
Heinen for eounting the nematodes. The author wishes to thank Eskild
Kirkegaard (Danish Fishery Institute, Copenhagen) and Martin Walsh
(Marine Laboratory, Aberdeen) for eollecting maekerel sampIes during thc
Maekerel Egg Survey in the North Sea in 1984. The author wishes to' thank
also Paul van Banning, who made the historic Anisakis data of 1970-1971
available and who was a great help during these Anisakis investigations.
10
REFERENCES
Anderson, R.M., 1978.
The regulation of host population growth
parasitic species. Parasitology 76, 119-157.
by
Anon., 1984.
Report of the meeting of the coordinators
Stornach sampling project 1981.
ICES C.M. 1984/G:37 53pp. (mirneo.).
of
Anon., 1988.
Report of the Mackere1 Working Group.
ICES C.M.1988/Assess: 12, 82pp. (mirneo.).
van Banning, P. and
RB. Becker, 1978.
Long-term
survey
data
(1965-1972)
on the
occurrence
of Anisakis
larvae
(Nematoda:
Ascaridida) in herring, Clupea harengus L., from
the North Sea. J. Fish Biol. 12, 25-33.
Davey, J.T., 1972.
The incidence of Anisakis larvae (Nematoda:
Ascaridata) in the commercially exploitcd stocks
of.. herring (Clupea harengus L., 1758) (Pisces:
Clupeidae) in British and adjacent waters. J. Fish
Biol. 4, 535-554.
Eltink, A.,
M. Warmerdam and
A. Heinen, 1986.
Origin, migration and spawning of southern
North Sea Mackerel with respect to the overspill
of Western Mackerel to the North Sea stock.
ICES C.M. 1986/H:49 15pp. (mirneo.).
Eltink, A.T.G.W., 1987.
Changes in age-size distribution and sex ratio
during spawning and migration of Western
Mackere1 (Scomber scombrus L.).
J. Cons. int Explor. Mer, 44: 10-22.
Giedz M., 1981..
The
Blue
and
ICES
Lindley J.A., 1977.
Continuous plankton records: the distribution of
the Euphausiacea (Crustacea: Malacostraca) in the
North Atlantic and thc North Sea, 1966-1967.
Journal of Biogeography, 4, 121-133.
MacKenzie, K, 1981.
The plcrocercus of Grillotia angeH (Cestoda:
Trypanorhyncha)
as
a
biological
tag
for
Mackerel. ICES C.M. 1981/H:57 9 pp. (mirneo.).
q
;
•
'~
parasitic infestation of the muscle tissue of
Whiting by Anisakis larvae, in spawning
feeding grounds.
C.M. 1981/H:70 12pp. (mirneo.).
Margolis, L., G.W. Esch,
J.C. Holmes, A.M. Kurie
G.A. Schad, 1982.
The use of ecological terms in parasitology
(report of an ad hoc committee of the American
Society of.... Parasitologists).
J. Parasitol. 68(1) pp 131-133.
Mehl, S. and
T. Westgaard, 1983.
The diet and consumption of mackerel in the
Sea.
ICES C.M. 1983/H:34 30 pp. (mirneo)..
I
11
...
Pippy, l.H.C. and
P. van Banning, 1975.
Identification of Anisakis larva (I) as Anisakis
simplex (Rudolphi, 1809, det. Krabbe 1878)
(Nematoda: Ascaridata).
l. Fish. Res. Bd. Can. 32, 29-32.
Roskam, R. Th., 1966.
Anisakis larvae in North Sea herring.
ICES C.M. 1966/H:13 3pp. (mimeo).
Smith, I.W. 1971.
Thysanoessa inermis and T. longicaudata
(Euphausiidae) as First Intermediate Hosts of
Anisakis sp. (Nematoda: Ascaridata) in the
Northern North Sea, to the North of Scotland and
at Faroe.
Nature 1971 Val. 234 page 478.
Smith, I.W. and
R. Wootten, 1978
Further studies on the occurence of larval
Anisakis in Blue Whiting.
ICES C.M. 1978/H:53 9pp. (mimeo).
Smith, I.W., 1983a
Larval Anisakis simplex ( Rudolphi, 1809, det.
Krabbe, 1878) and larval Hysterothylacium sp.
(Nematoda: Ascaridoidea) in euphausiids
(Crustacea: Malacostraca) in the North-East
Atlantic and northern North Sea.
Journal of Helminthology 57, 167-177.
Smith, J.W., 1983b.
Anisakis simplex (Rudolphi, 1809, det. Krabbe,
1878) (Nematoda: Ascaridoidea): Morphology and
morphometry of larvae from euphausiids and
fish, and a review of the lifehistory and ecology.
Journal of Helminthology 57, 205-224.
-.
06 07 08 09 EO E1 E2 E3 E4 E5 E6 E7
E8 E9 FO Fl F2 F3 F4
i~.3
50
tj6.s
2..
1.8
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Ba
16.0
58 . 5'~+~:---+--+--t--+-~507~"0-tV-y....L-J!.._-+--+_+--l-~_--t5&..0--!.~
A
I(
/
I-+--l--t---l---I--l--<:...j...\..l()'1-L~~
iß...r.---t--t\f---+--+-~-+--+~---l
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1-+--t--+--+------:I--+---+-J})~A=;7,?1J(
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r
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•
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43
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l-fl~~r7 1\-~-t-~--1-+-_--1-:--_-:--_-:f-_-~I---1--l~~
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t
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,---jf--j.-+---+----+--+----,-4--+-/7
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17
53 .5'1---+--+---4--tl....
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46
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1_-+--t_-+----+I?i.,:-::::J,4-/_~~O-3~~05___1~-+~--P-.
33
3
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51. 01---+--+-_+--+----If---I--+-._-ll-'15!!!....0-4--/
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I--+---+---I---r\~
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(0
V /1--+--1---+--+--+----+--1f--4---..,.J
~~~J----J,f-4--+--i---I---l-.l
V"'-l
30
29
jV
r-
28
27
1\\I-+-~
1\
48 .5,1---+---1:---+--+---+--+--t----I---l-r
_l-I
26
25
24
23
\
~
1\
r----...
"
22
(
21
ANI84KI5. in NACKEREL
1--t--t---t-+---f--+--f--4---I--+-+--+--l - preva 1ence
70-71
1--+--t----1r--t--t--t--t--t--+-+--+--+--l - abundance
- fish examined
46 .01-+--+--+--+---1--1---+--+--+---1--4------'1--1
.-/r-.-..~-..-,
-::::::==!=:::::====~~_ __l1
43. 51L.-.-L.-.L-.--Jl..--...L---b=::!-.
-14.0
-9.0
-
-4.0
2
20
19
18
_.._J
1.0
Figure 1. The prevalence (%) and äbundance of Anisakis in mackerel and the
number of mackerel, which were examined, by rectanglein 1970-1971.
17
16
-.
06 07 08 09 EO E1 E2 E3 E4 E5 E6 E7 E8 E9 FO Fl F2 F3 F4
~~~
<-:
~5
'.
V
(JO
16.0
5C
58. 5
49
100
AO.O
1
\'
IJ
.
Ir ~r ~
{jJo~
Q
IS
5.9
110
10
G.3
,5
rW
90
12.6
7.5
•
10
11.4
!GI
15
~~.o
53. 5
.?O
IJ'-~
'la
~/~
'14
206
17
51. 0
~46
19
69
191
v
.:5
/JO
~.8
90
12.7
1.5
\
~
17.1
,~
/
~r
!9
00
11.4
30
44
2.2
/:
25
~
.-r
,46
~'36
tOq
100
11
:.7
-A
I'"
~
~
)
(.-
ji"V"'JO
!'öd'
2.0
16
~iB
1.8
13
5.3
101
\I
100
12.1
\
33
A4
GO
25
~I 9
)
~
6.9
61
AO
!!l.9
137
25
10
)
'jJ
~49
~gOg
90
\:;7
tlJ
94
11.7
16
J~
1.1
V
1(v0
100
14,9
25
r,6.5
93
16 8
16
~'t
o/~
~
Jri~.2
l
7
I
~o~
5
9il
28'S
54
9B
31.4
152
~
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\
~
23
94
&8
I
( ~.
~r7
I-=-
r)
Bö
43.0
I
\
~'"
>10
y-
<;
17
91
17.7
48.5
(?
LV'I~
100
306
19
95
25.2
il4
15.1
.l2
J~
/
iJ.f 7;//1..
56. 0
17
19.1
27
(
19.
ilO
165
'10
24:1
124
~
ri?6
100
16 ~
12
l...---'
I(
72
6.4
16
~
.(
30
29
28
1
_1../
27
26
\
25
24
23
-
22
I
46.0
AI
'i.1
16
43
5.1
16
I1
. 4.6
14
58
4.0
ANISAKIS in MACKEREL
- {Jrevalence 82-84
- abundance
- fish examined
12
J'I.--....
43.5
-14.0
-9.0
)
'--
-4.0
33
32
31
./
r\
r----....
48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
I
1.0
Figure 2. The prevalenee (%) and abundanee of Anisakls in mackerel and the
number of maekerel, which were examined, by reet angle in 1982~1984.
21
20
19
18
17
16
YJ.Jz.
.
··· :..
Yla
,..........
,:'
···
·
.)
........
:
:
###
Yla
..
·
·
•
Y..l.li
.
.:'
i..
''":....
•• #
...... -
Anisakis in Mackerel
1970
1971
YJ..1.1
._ ...
~
- prevalence %
- abundance
- fish examined
.
• •.••.•..!
Figure 3. The prevalence (%) and abundance of Anisakis in mackerel and the
number of mackerel. which were examined. by leES Division or by
Subd1v1s1on 1n 1970-1971.
:...
.'
\.
....... -,' ~
•
IVa NE
86%
26.0.
50
IVa
....
84%
•
25.2
119
.•~..,-,.,....-f'lI'lr-1
·.
..· ..
.-"'..
:
'
:.. ..:
VIa NlV
.
SEE
:
••••
76%
5.4
172
: .......
IVb
IVb E
lY
97%
39.3
86%
37
447
21.5
YJ..li.
.'92%
( :25.2
',,: 60
•
..
···,
Y.l.l1
86%
11.4
774
l.-......•
....
t ..
.
'. -'..
-'-...,
"
Anisakis in Mackerel
.
.....
1982
1984
- prevalence %
- abundance
- fish examined
"'VIII
65%
5.2,
76
;
........................e ••••• )
-'
-_········200 m
Figure 4. The prevalence (%) and abundance of Anisakis in mackerei-and the
number of mackerel, which were examined, by leES Division or by
Subdivision in 1982-1984.
Abundanco
50
45
...
40
•
35
30
llllI
l'EI
lZ1
25
20
15
age 1-3
aga 4·6
age 7·10
age 11+
10
5
o
1970-1971
1983·1984
NOl"th Sea Mackerel population
1970·1971
.
1983·1984
southern North Sea mackerel
Figure S. Abundance of Anisakis in mackerel in the North Sea Mackerel population
and in the mackerel fram the southern North Sea by age graup in
1970-1971 and 1983-1984 •
•
Abundanco
40
35
30
25
•
length 25-29
llllII
length 30-34
Eil
length 35-39
[i] length 40-44
North Sea
Mackerel
population
•
southern North Sea Western Mackerel
mackerel
population
Bay of Biscay
mackerel
Figure 6; Abundance of Anisakis in.mackerel in the North Sea and Western
M3ckerel population and in the mackerel from the southern North
Sea and the Bay of Biscay by length group in '1982-1984.
Abundanca
40
35
30
11
aga 1·3
25
lliD
lE1
lEl
aga 4-6
20
15
aga 7·10
aga 1'+
10
5
o
North Sea Mackerel southern North Sea . Western Mackersl
population
mackerel
. ,population
Bay of Biscay.
mackerel
Figure 7. Abundance of Anisakis in mackerel in the North Sea and Western
Mackerel population and
the mackerel from"the.southern'North
Sea and the Bay öf Biscay by age graup in 198?-1984.
in
Abundanca
50
45
26
40
35
•
aga 1·3
lllII
aga 4·6
20
ED
age 7·10
15
GJ
age 11+
30
25
10
5
o
IVaNW+NE
July
IVaSW+SE
June+July
IVbW+E
June +July
IVc
June+July
Figure 8. Abundance of Anisakis in mackerel in the North Sea by area and
by age gioup in June and July in 1983-1984. The numbers indicate
the number of mackerel examined~
•
Abundanco
40
35
30
25
20
•
aga 1·3
III
aga 4·6
I]] aga 7·10
15
GJ
aga 11+
10
5
o
VIa + Vllb
Juno+July
•
Vllj
May
VIII
Juna
Figure 9. Abundance of Anisakis in mackerel in the western areas by area and
by age group from MaY,to July in 1983-1984. The numbers indicate
the number of mackerel examined.
Abundanca
50
45
2
40
•
35
30
l!l!I
lEl
lEl
25
20
15
aga 1·3
aga 4·6
aga 7·10
aga 11+
10
5
0
March
May
Figure 10. Abundance of Anisakis in mackerel in the mackerel spawning area
Division Vllj by month and by age group from March to May in,
1983-1984~ The numbers lndlcate the number of mackerel examined.
...
100
%
90
80
,
70
[El High
60
l!l!I
50
•
40
30
Medium
Lew
>45 A.lfish
16·45 A.lfish
, -15 A.lfish
20
10
o
aga 1-3
age 4·6
age 7-10
age 11-15+
Figure 11. Cumulative percentage of mackerel having a low, mediu~ and high
Anisakis infestation in the North Sea Mackerel population by age
group in 1983-1984~
•
100
0/0
90
80
70
lEl
,.'.'
llllI
60
50
•
40
30
High
Medium
Low
>45 A.lfish
16·45 A.lfish
1·15 A.lfish
20
10
o
•
age 4·6
age 7·10
age11-15+
Figure 12~ Cumulative percentage of mackerel having a low, medium and high
Anisakis infestation in the Western Mackerel population by age
group in 1983-1984.
100
0/0
90
80
70
..
EJ
llllI
:-.'.
60
50
•
40
30
High
Medium
Low
>45 A.lfish
16-45 A.lfish
1·15 A.lfish
20
10
o
aga 1·3
age 4·6
age7-10'
age 11·15+
Figure 13. Cumulative percentage of mackerel having a low, medium and high
Anisakis infestation
the mackerel fron the southern North Sea
by age group in 1983-1984.
in
....
x
.x•
•
..
...
56'
x
infech!<l sa~
•
uninfected sampie
I
~ mud sand bottom deposits
•
sS'
Figure 14. The distribution of euphausiid samples infected and uninfected with
larval Anisakis simplex (After Smith, 1983a) •
Abundance
250
200
/e
150
100
50
~e~
o
e~
e
/e
/e
0
•
/e
·e- theoretical cumulative
Anisakis infection
/e
·0- observed abundance
North Sea Mackerel
.•- observed abundance
Western Mackerel
~
1__
~O~~O~~i~v~o--O-n
-
o I!I===~1
2
ii-·--·I
I
I
I
I
.-.-.
3
4
5
6
7
8
I
I
9
I
10
Aga
Figure 15. The theoretical cumulative Anisakis °infection by age in mackerel in
comparison to the abundance of Anisakis observed in the North Sea
and Western Mackerel by age.
TAßLE 1. The number of mackerei, which were examined
for Anisakis, by year and by leES Division or
by Subdivision. Between brackets the number
of macKerel of which the age was estimated.
Year
(Sub)Division
Number of mackerel
aged
examined
---------------------------------------
•
•
1970
1970
1970 .
1970
IVa NE
IVa SE
VIa NE
VIIg
100
125
150
250
(100)
(124)
(150)
(250)
1970
Total
625
(624)
1971
1971
1971
IVa NE
IVa SE
IV c
193
50
196
(193)
(50)
(196)
1971
Total
439
(439)
1982
1982
39
137
(0)
(0)
1982
IVb E
IVc
-----Total
176
(0 )
1983
1983
1983
1983
1983
1983
1983
1983
IVb W
IVc
VIa NE
VIa SW
VIIc
VIIe
VIIj
VIII
16
60
50'
39
60
136
152
76
(16)
(32)
(50)
(16)
(14)
(81)
(114)
(70)
1983
Total
589
(393)
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
IVa NE
IVa NW
IVa SE
IVa SW
IVb E
IVb W
IVc
VIa NW
VIa SW
VlIb
VIIh
Vllj"
50
25
119
124
408
21
352
172
241
84
25
622
(50)
(25)
(119)
(50)
(392)
(21)
(300)
(25)
(100)
(25)
(25)
(450)
1984
Total
2243
(1582)
------
------
------
------
=====Q===================================
(3038)
4072
TOTAL
1970-1984
-
._---------------------------
·.oe .
....... ....
• ...
•
.. -
44
TABLE 2. The prevalence (%), mean intensity and abundance of Anisakis in mackerel and the number of mackerel, which were
examined, by year, by leES Division or by Subdivision , by month and by rectangle. Between brackets the number
of mackerel of which the age was estimated.
Nullber of ..ekerel
1970
1970
1970
1970
1970
1970
1970
1970
1970
1970
1970
1971
1971
1971
1971
1971
1971
1971
1971
1971
(Sub)ll1vloion
IVa 111:.
IV. SE
IV. SE
IVa SI1
VIa 111:
VI. 111:
VIa 111:
VUg
VUg
vUg
VIig
IV.
IV.
IV.
IV.
IV..
IV..
IV..
IV..
IV..
111:
111:
111:
S1
Honth
"'lIber of JUckerel
4
5
5
8
8
8
8·
10
11
11
11
Reetangl.
exaained
agod
Prlvalenee
lntenelty
Abund.ne.
5111
100
25
(100)
81
100
98
96
50
58
42
51
38
54
62
11.7
16.6
16.3
8.8
4.8
3.2
4.4
4.9
3.2
6.1
2.4
9.4
16.6
16.0
8.5
2.4
1.8
1.9
2.5
1.2
3.3
1.5
North Se.
North Se.
North Sea
12.4
10.5
8.6
11.3
3.8
3.4
• 2.7
4.0
5.5
We.tem
North Se.
North Se.
North So.
North Ses
North Sea
North Se.
North Se.
North Se.
4S1'5
46U
48E8
46E3
46&4
48E5
31&4
31&4
32E2
32E3
34lZ
35F3
35F4
34F3
41
SO
39
90
47
(0)
(0)
(0)
16
29
(16)
(9)
(13)
(10)
(50)
(8)
(8)
(0)
(14)
(6)
(16)
(46)
(13)
(10)
50lZ
47F4
53F2
IVb 11
IV..
IV..
10
10
10
1983
1983
1983
1983
1983
1983
1983
1983
1983
1983
1983
1983
1983,
1983
1983
1983
1983
1983
1983
1983
1983
1983
1983
1983
1983
1983
1983
IVb 1/
IV..
IV..
IV..
6
4
5
6
1
3
3
3
3
1
1
1
4
3
4
4
4
4
5
5
5
5
6
6
6
6
6
39Fl
34F4
34F4
34F4
47E3
38E0
VI 11
Vlll
SO
100
50
SO
50
(49)
(50)
(50)
(50)
(SO)
(100)
(SO)
(SO)
(SO)
(100)
(SO)
(43)
(SO)
(50)
(48)
(7)
(41)
(50)
49F3
SOU
1981
1981
1982
VI. SI/
VI. SII
Vll..
V11..
Vlle
Vlle
Vlle
Vlle
Vllj,
Vllj
Vllj
Vllj
Vllj
Vllj
Vllj
V11j
Vllj
Vlll
V111
Vlll
so
so
so
50
(25)
100
SO
43
50
SO
48
4
4
5
5
4
5
5
5
10
39F4
33F4
34F4
VI. 111:
Heckerel
(Sub)populatlon
Hean
(X)
te81'
39E0
3407
3S07
28E6
29E6
28E6
28E5
3208
26EO
2709
2909
3308
2708
2709
27E0
2809
17E8
18E8
19!8
20!6
22ES
1
21
10
50
20
19
37
23
24
16
83
13
10
1
12
16
67
8
17
8
6
12
14
16
16
(I)
(12)
(16)
(29)
(8)
(17)
(8)
(6)
(12)
(14)
(10)
(16)
(18)
-18
Weltern
WeItem
Weatem
Western
WeItem
W.lten
Weltern
9
96
97
96
82
68
71
73
92
12.6
10.9
8.8
11.7
4.7
4.9
3.8
5.4
5.9
61
45,
38
11.3
4.4
6.2
6.9
2.0 lauthern North Se.
2.4 lauthern North Se.
93
17.9
7.1
14.6
8.9
17.3
26.5
30.6
31.5
19.3
21.9
4.0
5.9
3.4
24.8
21.0
6.9
28.4
11.5
8.8
10.7
8.0
10.8
6.9
6.5
11.7
6.2
8.9
16.8 •
3.9 lauthern North Se.
9.0 southern North Sea
6.2 louthern North Sea
16.6
Weltern
15.1
Weltern
30.6
Western
19.8
Western
17.7
Western
11.9
Weltern
2.0
Weltern
3.3
Western
1.8
Weltern
14.8
Western
11.0
Weltern
6.3
Weltern
26.6
Western
21.2
Weltern
6.6
Weltern
8.8
Weltel'ß
8.0
WeItem
10.8
Weltern
4.0
'leItern
4.6
Western
S.1
W•• tern
S.1
Western
6.4
55
61
70
96
95
100
94
91
54
50
56
53
100
100
91
93
98
H
82
100
100
58
71
43
81
72
louthern
southern
lauthern
southen
Bauthern
-----
(X)
Year' (Sub)Il1,,1slon
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
IV. 111:
IV. 111:
IVa NIl
IV. SE
IV. SE
IV. SE
IV. SE
IV. SE
IV. SE
IV. SE
IV. SI/
IV. SI/
IVb 1
IVb E
IVb E
IVb E
IVb 1
IVb 1
IVb E
IVb 1/
IV..
IV..
IV..
IVc
IV..
IV..
IVc
IV..
IVc
VIa NIl
VI. NIl
VI. NIl
VI. NIl
VI. SI/
VIa SI/
VI. SI/
VIa SI/
Via SI/
V11b
V11b
V11h
Vllj
VUj
VUj
V11J
V11J
V11j
V11J
V11J
V11j
Vllj
V11j
V11j
Honth
Rectaeglo
exasalned
agod
Prevalenee
7
7
7
7
7
50FO
51FO
49E7
44Fl
44F4
46Fl
4612
48F0
48Fl
4812
47E8
47E8
41F3
36F4
36F5
41F3
42F3
43F2
43F3
43Fl
'34F4
33F4
3412
34F4
34Fl
34F4
35F4
34F4
34F2
43EO
43El
43&1
43&1
38D9
38D9
40EI
42E1
42El
3609
3709
26E1
26EO
2709
27EO
2809
2909
25
25
25
7
5
27
32
1
12
35
74
SO
148
(25)
(25)
(25)
84
88
(7)
85
100
1
1
1
7
7
5
6
5
6
6
6
6
6
7
7
4
5
5
5
6
6
6
1
8
5
5
7
8
5
6
6
6
8
5
6
4
4
4
4
4
4
4
4
4
5
5
5
5
29E0
3009
3OEO
2609
2708
2709
2909
30
SO
4
54
96
26
21
25
25
25
100
50
50
25
27
25
62
25
35
SO
133
28
25
30
25
47
37
15
7S
33
25
50
15
25
25
15
25
189
7S
25
(S)
(27)
(32)
(I)
(12)
(3S)
(0)
(50)
(139)
(25)
(50)
(4)
(54)
(94)
(26)
(21)
(2S)
(0)
(2S)
(100)
(SO)
(50)
(2S)
(2S)
(0)
(0)
(0)
(2S)
(0)
(0)
(2S)
(2S)
(25)
(2S)
(0)
(25)
(25)
OS)
(25)
(25)
(50)
' (25)
(25)
(25)
(25)
(25)
(2S)
(7S)
(2S)
72
77
84
100
100
80
97
96
98
60
38
100
98
100
96
100
36
36
84
48
76
60
44
37
40
79
80
71
76
67
82
96
76
64
76
72
84
94
72
100
86
88
96
84
100
84
79
81
80
He an
letonaH)'
Abundance
37.8
23.0
13.2
50.2
6.8
24.5
17.9
80.0
78.5
23.1
25.9
24.9
30.5
18.9
13.2
79.8
29.1
20.9
17.8
56.S
2.3
1.6
12.6
5.9
7.3
7.2
4.9
2.4
11.1
5.8
6:6
11.0
6.S
16.0
17.4
13.1
9.4
8.0
23.8
11.9
7.1
12.1
16.0
13.4
10.3
8.5
13.2
10.3
14.9
8.1
11.1
12.1
11.7
31.7
20.3
9.5
43.0
6.8
19.1
15.1
80.0
78.5
18.5
25.2
23.9
30.0
11.4
5.0
79.8
28.5
20.9
17.1
56.5
0.8
0.6
10.6
2.8
5.5
4.3
2.2
0.9
4.8
4.6
S.3
7.9
4.9
10.8
14.3
12.6
7.2
S.1
18.3
8.7
6.0
11.6
11.6
13.4
8.9
7.5
12.7
8.6
14.9
6.9
9.0
9.9
9.3
Heckerel
(Sub)population
North
North
North
aouthern North
southern North
.authern
lauthern
southern
BDuthern
80uthern
southcrll
_outhern
southern
80uthertl
Se.
So.
Se.
Se.
Se.
North Se.
Nortb se.
North Se.
North Sea
Horth See
North Sea
North Sea
North Sea
North Sea
Western
Weltern
Weltern
WeItem
Weltern
Weltern
Weltern
Western
Weltern
Weltern
Weltern
Weiter"
Western
Weltern
Weltern
Weltern
Weltern
Weltern
Weltern
Weltern
Weltern
Weltern
Weltern
Weltern
...
~-----------------_._--------- --------~----
TAßLE ·3. The total number of mackerel examined for Anisakis, the number uninfested and infested fish, the prevalence,
the mean intensity, abundance and the degree of infestation in the infected fish (%) by area for two time
periods 1970-1971 and 1982-1984.
Deg~ee of infestation (%)
Total
-------------------------------number
Number
Number
%
Mean
1-15 A 16-45 A >46 Anisakis
Area
examined
uninfested
infested
LOW
Period
Prevalence intensity Abundance
MEDIUM
HIGH
---------
------ --------- ---------- ---------- ---------- --------- --------- ------- ------- ------
1970-1971
IVa NE
IVa SE
1970-1971
1970-1971
IVc
1970-1971
VIa NE
1970-1971
VIIg
------------1982-1984
IVa NE
1982-1984 \ IVa NW
IVa SE
1982-1984
1982-1984
IVa SW
1982-1984
IVb E
1982-1984
IVb W
1982-1984
IVc
1982-1984
VIa NE
VIa NW
1982-1984
1982-1984 VIa SW
1982-1984
VIIb
1982-1984 VIIc
1982-1984
VIIe
1982-1984 VIIh
1982-1984 VIIj
1982-1984 VIII
293
175
196
150
250
23
5
41
75
122
270
170
155
75
128
92
97
79
50
51
50
25
119
124
447
37
549
50
172
280
84
60
136
25
774
76
7
7
19
4
62
1
268
2
40
66
21
4
61
4
104
26
43
18
100
120
385
36
281
48
132
214
63
56
75
21
670
50 .
86
13.0
5.2
4.1
4.3
10.5
12.6
4.1
2.0
2.2
30.2
13.2
30.0
25.5
25.0
40.4
6.9
17.3
7.1
16.8
18.7
27.0
8.2
7.1
13.1
7.8
26.0
9.5
25.2
24.7
21.5
39.3
3.5
16.6
5.4
12.8
14.0
25.2
4.5
6.0
11.4
5.2
11.4
--------- ---------- ---------- ---------- --------- --------72
84
97
86
97
51
96
77
76
75
93
55
84
87
66
--------- ------ --------- ---------- ---------- ---------- --------- ---------
74
71
96
96
95
24
28
4
:4
5
2
2
1
0
0
61
26
22
26
44
37
56
10
21
14
6
26
13
14
22'
2
6
1
10
10
18
3
0
5
0
------- ------- -----72
48
43
49
22
87
73
89
72
70
50
88
91
75
82
11
18
21
32
9
10
21
18
------- ------- ------
TABLE 4. The total number of mackerel examlned for Anisakis, the number unlnfested end lnfested flsh, the prevalence.
the mean Intenaity, abundanee and the degree of Infeatatlon In the infeeted floh (%) by area and by length
ela.. for two time perioda 1970-1971 and 1982-1984. The montha in whlth the mackerel samplea were co11eeted
are li.lIted belo" the name of the Division or Subdlvls1on.
Degree of Infeatatton (I)
Total
-----------------Area &
Length
number
Number
~mbat
%
Meso
1-15 A 16-45 A
>46 Anloakls
ftlonth
exam.lned "~nlnfe8ted infastad Prevalence Intanalty Abundante
Period
elaases
LOII
MEDIUM
HIGH
---1970-1971
1970-1971
IVa SE
5+8
1970-1971
IV"
4+5+10
1970-1971
1970-1971
•
IVa NE
4+5
---1982-1984
1982-1984
1982-1984
1982-1984
Via NE
8
VIIg
10+11
IVa NE
7
IVa NIl
7
IVa SE
7
IVa SIl
6
1982-1984
IVb E
5+6+7
1982-1984
IVb 11
6+7
1982-1984
IV"
4+5+6+7
1982-1984
Via NE
2
1982-1984
VIa NIl
7
1982-1984
1982-1984
1982-1984
VIa SIl
3+6+8
VIIb
6
VII"
3
1982-1984
VIle
1+2+4
1982-1984
VIIh
4
25-29
30-34
35-39
40-44
25-29
30-34
35-39
40-44
20-24
25-29
30-34
35-39
40-44
25-29
30-34
35-39
40-44
25-29
30-)4
35-39
40-44
30-34
35-39
40-44
25-29
30-34
35-39
30-34
35-39
40-44
45-49
20-24
25-29
30-34
35-39
40-44
45-49
20-24
25-29
30-34
35-39
40-44
45-49
30-34
35-39
40-44
45-49
25-29
30-34
35-39
40-44
45-49
25-29
30-34
35-39
40-44
25-29
30-34
35-39
40-44
25-29
30-34
35-39
40-44
30-34
35-39
40-44
45-49
25-29
30-34
35-39
40-44
45-49
25-29
30-34
35-39
25-29
30-34
3S-39
1982-1984
VIIj
3+4+5
1982-1984
VIII
6
--- --
40-44
25-29
30-34
35-39
40-44
45-4'
20-24
25-29
30-34
35-39
40-44
45-49
---- ---50
93
125
25
11
52
82
30
2
106
25
47
16
1
138
10
1
30
150
62
8
37
11
2
1
16
8
64
34
19
2
2
2
34
39
39
8
13
18
111
130
153
22
1
27
8
1
24
213
187
103
22
10
25
10
5
1
131
29
11
4
203
59
14
46
20
17
1
3
25
21
10
1
75
55
6
1
16
7
2
14
7
0
0
3
2
0
0
13
9
14
5
0
75
0
0
19
87
15
1
48
79
118
25
11
49
80
30
2
93
16
33
11
1
63
10
1
11
63
47
7
7
0
0
0
7
0
18
0
1
0
0
0
0
2
1
1
0
4
29
23
5
1
0
1
0
0
17
124
91
26
10
0
1
1
0
0
38
1
1
1
62
1
2
19
1
0
1
1
1
1
1
0
38
21
2
0
2
1
30
11
2
1
9
8
46
34
18
2
2
2
34
37
38
7
13
14
82
107
148
21
1
26
8
1
7
89
96
77
12
10
24
9
5
1
93
28
10
3
141
58
12
27
19
17
0
2
24
20
9
1
37
34
4
1
14
6
0
11
314
236
107
2
4
1
8
21
16
0
------
1
1
17
393
244
118
2
10
2
6
79
8
11
0
19
25
19
1
6
1
11
4
3
1
'"
----96
85
94
100
100
94
98
100
100
88
64
70
69
100
46
100
100
37
42
76
88
---81
100
100
100
56
100
72
100
95
100
100
100
100
95
97
88
100
78
74
82
97
96
100
96
100
100
29
42
51
75
55
100
96
90
100
100
71
97
91
75
70
98
86
59
95
100
0
67
96
95
90
100
49
62
67
100
88
86
----- ----11.1
9.7
12.6
12.1
9.4
9.3
15.4
13."7
4.0
5.5
2.2
6.1
5.0
25.0
3.2
6.9
9.0
4.5
3.2
S.6
S.1
----15.1
70.4
36.0
5.0
7.6
20.6
13.3
51.2
32.9
28.0
6.5
20.0
24.4
28.6
26.2
17.0
33.6
20.9
13.4
26.0
29.5
31.0"
3.0
49.9
16.3
25.0
2.4
5.4
6.0
8.7
15.4
7.7
12.4
19.4
56.0
4.0
5.3
14.4
4.0
3.0
9.7
31.2
33.3
11.0
33.9
14.1
10.6
8.2
11.9
12.1
9.4
8.8
15.0
13.7
4.0
4.8
1.4
4.3
3.4
25.0
1.5
6.9
9.0
1.7
1.3
4.3
4.5
-----
12.3
70.4
36.0
5.0
4.3
20.6
9.6
51.2
31.2
28.0
6.5
20.0
24.4
27.1
25.6
14.9
33.6
16.3
9.9
21.4
28.5
29.6
3.0
48.0
16.3
25.0
.7
2.3
3.1
6.5
8.4
7.7
11.9
17.5
56.0
4.0
3.7
1).9
3.6
2. )
6.7
30.7
28.5
6.5
32.2
14.1
7.5
15.4
44.1
27.1
1.0
10.0
6.9
3.3
2.0
5.1
12.5
5.0
14.8
42.0
24.4
1.0
4.9
4.3
2.2
2.0
4.5
10.7
3.5
11.8
16.8
10.1
9.0
7.8
1.0
5.6
10.6
5.8
2.2
9.4
16.2
9.1
9.0
3.1
.5
2.4
8.9
4.9
75
80
70
76
82
78
65
70
23
19
27
24
18
22
33
27
2
1
3
0
0
0
3
3
97
100
91
91
2
0
9
9
1
0
0
0
97
100
3
0
0
0
91
98
94
86
9
2
6
14
0
0
0
0
73
27
23
36
3
36
89
50
76
15
39
11
38
13
35
39
0
12
11
50
22
41
38
42
57
8
43
71
51
43
29
44
51
40
4)
69
50
26
34
39
62
15
11
18
0
23
7
4
15
19
10
12
50
58
50
31
0
100
9)
88
83
90
79
44
60
0
5
10
16
17
10
17
56
0
0
2
2
1
8
0
4
0
40
95
64
100
5
32
0
0
4
0
84
48
50
74
58
77
14
26
33
26
21
12
3
26
17
0
21
'12
54
35
56
46
25
22
0
40
22
89
85
8
12
3
3
100
67
0
33
0
0
100
77
66
84
0
19
26
14
0
3
8
2
88
76
88
13
24
13
0
75
0
65
80
97
91
100
40
50
42
84
84
0
-----
----
0
0
TABLE 5. The total number of mackerel examlned for Anlsakls, the number unlnfested and infeated fish, the prevalence. the
mean Intenslty, abundance and the degree of infestation in the infected fish (%) by area and by age groups for two
time periods 1910-1911 and 1983-1984. The months in which the mackerel samp1es were collected are 1isted be10w the
name of the Division or Subdivision.
Degree of Infestatlon (%)
Total
Area &
number
Number
1-15 A 16-45 A >46 Anisakis
%
Mean
Number
Period
month
Age
examlned unlnfested infested Prevalence intens1ty Abundance
Low
MEDIUM
HIGH
1970-1911
•
IVa NE
4+5
1970-1971
IVa SE
5+8
1970-1971
IVc
4+5+10
1970-1971
VIa NE
8
1970-1971
VIIg
10+11
1983-1984 IVa NE
7
1983-1984 IVa NW
7
1983-1984 IVa SE
7
1983-1984 IVa SW
6
1983-1984 IVb E
5+6+7
1983-1984 IVb W
6+7
1983-1984 IVc
4+5+6+7
1983-1984 VIa NE
2
1983-1984 VIa NW
7
1983-1984 VIa SW
3+6+8
1983-1984 VIIb
6
1983-1984 VIIc
3
1983-1984 VIIe
1+2+4
1983-1984 VlIh
4
1983-1984 Vllj
3+4+5
1983-1984
VIII
6
---- -
1-3
4-6
7-10
11+
1-3
4-6
7-10
11+
1-3
4-6
7-10
11+
1-3
4-6
7-10
1-3
4-6
7-10
11+
1-3
4-6
7-10
11+
1-3
4-6
7-10
11+
1-3
4-6
7-10
11+
1-3
4-6
7-10
11+
1-3
4-6
7-10
11+
1-3
4-6
7-10
11+
1-3
4-6
7-10
11+
1-3
4-6
7-10
11+
1-3
4-6
7-10
11+
1-3
4-6
7-10
11+
1-3
4-6
7-10
11+
1-3
4-6
7-10
11+
1-3
4-6
7-10
1-3
4-6
7-10
1-3
4-L
7-10
11+
1-3
4-6
7-10
11+
-------12
141
115
14
11
48
10
34
22
116
35
23
22
99
43
8
118
89
41
2
9
1
1
3
1
1
0
15
13
8
5
54
21
0
74
37
11
0
20
3
3
11
11
2
1
40
43
16
20
12
13
10
15
101
101
72
118
1
8
12
16
84
93
1
0
0
5
2
0
0
15
3
0
1
1
0
1
0
25
9
8
. 4
0
0
1
0
59
41
24
21
1
1
0
0
5
3
0
0
14
7
0
0
8
2
0
0
1
0
0
0
34
8
0
1
2
1
39
22
2
5
12
4
5
1
---135
106
13
16
45
69
33
22
101
22
15
17
45
22
8
44
52
30
2
----24 -----6 ---18
79
76
24
16
6
4
9
11
4
1
54
52
8
2
17
5
2
1
4
6
3
1
63
15
3
11
12
2
170
257
73
64
20
18
18
14
----
19
3
3
6
9
2
1
25
40
16
19
11
13
9
15
76
92
64
114
1
8
11
16
25
52
55
55
23
15
6
4
4
8
4
1
40
45
8
2
9
3
2
1
3
6
3
1
29
7"'
3
10
10
1
131
235
71
59
8
14
13
13
---- ------10.9
10.0
92
92
93
94
94
99
97
100
87
63
65
77
46
51
100
37
58
73
100
75
95
100
100
55
82
100
100
63
93
100
95
92
100
90
100
75
91
89
97
100
100
92
100
30
56
70
72
96
94
100
100
44
73
100
100
74
87
100
100
53
60
100
100
75
100
100
100
46
47
100
91
83
50
77
91
97
9240
78
72
93
---- ---
11.5
12.6
13.9
10.2
14.3
12.6
13.3
5.3
4.2
6.6
4.9
3.1
4.8
7.6
3.7
4.5
5.0
1.5
10.6
11.1
13.1
9.6
14.1
12.2
13.3
4.6
2.7
4.3
3.8
1.4
2.5
7.6
1.4
2.6
3.6
1.5
25.9
171.3
15.3
4.0
10.7
53.0
12.0
9.7
27.8
57.3
38.4
15.5
33.8
21.2
26.1
14.1
24.7
30.0
30.8
29.0
35.1
40.9
43.4
2.5
8.4
7.9
7.2
8.2
18.5
49.2
17.0
8.8
7.5
12.5
8.0
9.5
13.8
15.1
61.5
7.0
22.3
13.5
1.0
6.7
16.7
36.3
32.0
3.3
1.6
7.3
5.8
9.0
1.0
7.7
14.4
18.6
24.6
171.3
15.3
2.2
8.7
53.0
12.0
6.1
25.9
57.3
36.5
14.2
33.8
19.1
26.1
10.6
22.5
26.7
29.8
29.0
35.1
37.5
43.4
.7
4.7
5.5
5.2
7.9
17.4
49.2
17.0
3.9
5.5
12.5
8.0
7.1
11.9
15.1
61.5
3.7
13.4
13.5
1.0
5.0
16.7
36.3
32.0
1.5
.7
7.3
5.3
7.5
.5
------13.8
10.3
12.6
5.3
9.1
7.9
7.8
6.0
13.2
18.1
11.6
2.1
7.1
5.7
7.2
----
75
69
63
18
68
67
13
97
96
87
94
98
96
88
96
98
90
23
24
31
31
22
30
30
27
2
5
13
6
2
5
13
5
2
10
2
2
0
6
2
1
3
0
1
0
0
0
0
0
0
0
0
0
83
47
11
42
6
11
100
67
0
33
0
0
80
50
0
42
46
23
22
53
67
45
44
38
12
28
38
32
55
54
78
21
26
44
36
46
8
23
63
26
0
23
0
20
7
12
20
17
25
9
31
100
85
87
84
87
60
50
50
73
44
0
10
11
16
13
33
33
25
18
25
0
6
2
0
0
7
17
88
13
0
88
78
63
8
18
25
5
4
13
89
11
0'
50
50
0
97
100
3
0
0
0
90
90
10
10
0
0
81
19
24
25
22
13
29
8
15
0
76
72
66
75
88
71
92
85
4
9
3
0
0
0
0
TAßLE 6. The total number of mackerel examlned for Anisakls. the number unlnfested and in fes ted fish. the prevalence.
the mean intensIty, abundance and the degree of infestation In the in fee ted fish (%) for the Western Mackerei,
the North Sea Maekerel and the mackerel from the southern North Sea and by length elass for two time periods
1970-1971 and 1982-1984.
Degree of infestation (%)
----------------Total
1-15 A 16-45 A >46 Anisakis
Population
Length
number
Ibmber
Number
%
He an
LOW
MEDIUM
HIGH
and Period
elass examined uninfested infested Prevalenee intensity Abundanee
-......-....
North Sea
Maekerel
1970-1971
25-29
30-34
35-39
40-44
61
111
195
51
-----North Sea
25-44
418
20-24
25-29
30-34
35-39
40-44
45-49
15
15
63
61
102
16
20-49
272
25-29
30-34
35-39
40-44
31
288
72
9
Maekerel
1982-1984
•
--------_.
Western
Maekerel
1970-1971
25-44
2
15
9
0
59
96
186
51
- ---392
26
-----0
11.6
72
26
2
93
100
97
99
88
23.1
20.0
32.0
31.4
29.0
21.5
20.0
31.0
31.1
25.4
20
36
48
31
33
43
60
57
44
53
45
50
20
7
8
17
23
7
-._--_.-39
_.-.--_.-
36
48
16
17
162
15
1
12
126
57
8
-------.19
6.3
3.2
5.8
5.6
1.4
4.6
5.0
83
98
95
88
2
5
13
0
0
0
0
203
51
4.2
2.1
96
4
0
40
54
74
95
90
60
7.8
7.8
10.0
20.4
12.2
6.3
3.1
4.3
7.4
19.5
1l.0
3.8
93
81
62
81
5
17
26
15
2
2
12
5
- --76
--._---4.0
19
6
97
100
91
91
2
0
9
9
1
0
0
0
96
4
100
91
85
83
75
0
6
11
16
17
0
3
5
1
8
86
11
3
-------
1281
25-29
30-34
35-39
40-44
2
106
25
47
16
20-44
196
Southem North 25-29
Sea Maekerel
30-34
1982-1984
35-39
40-44
45-49
28
250
213
116
22
-6
--------.0
13
9
14
5
2
93
16
33
II
-----80
..------..
100
88
64
70
69
---------79
---41
155
-----29
20
8
148
103
30
10
311
-------.
---- ----
44
7989
326
...------
12.4
94
------------100
30.0
30.0
---27.6
1607
--629
2
1
3
2
28.2
20-49
25-49
22
21
30
26
----98
4
56
655
392
171
3
Sea Maekerel
1970-1971
76
78
67
73
266
47
233
19
19
2
_._--.--...Southero North 20-24
8.6
13.3
13.4
6
10
103
888
411
190
5
20-24
25-29
30-34
35-39
40-44
45-49
10.0
13.9
13.4
87
95
100
15
14
63
59
101
14
197
Maekerel
1982-1984
-._------- ---._---- --------97
10.8
10.4
1
0
2
1
2
400
Western
•
-------
----_....-
102
110
86
12
41
52
74
55
318
51
----
-------_.
13.4
---._--.-
4.0
5.5
2.2
6.1
5.0
--_.--2.4
10.7
4.8
1.4
4.3
3.4
5.2
---4.1
2.3
6.2
8.5
8.8
15.4
.6
2.5
4.4
6.5
8.4
._-.-_.
7.9
----4.0
--------
-.
TABLE 7. The total number of mackere1 exam1ned f;r An1sak1s. the number un1nfested and 1nfested flsh. the preva1ence.
the mesn lntens1ty. abundance snd the degree of lnfeststlon 1n the 1nfected f1sh (%) for the Western Hackerei.
the North Ses Mackere1 snd the mackere1 from the southern North Ses snd by sge groups for two tlme per10ds
1970-1971 snd 1983-1984.
Degree of 1nfestat1on (%)
Total
%
Me an
1-15 A 16-45 A >46 An1saki s
Popu1atlon
number
Number
Number
MEDIUM
HIGH
and Perlod
Age exsm1ned un1nfested 1nfested Preva1ence lntens1ty Abundance
LW
---------------
----._----North Sea
Mackere1
1970-1971
1-3
4-6
7-10
11+
1-11+
•
North Sea
Hackerel
1983-1984
----.-.---Western
Hackerel
1970-1971
1-3
4-6
7-10
11+
1-11+
1-3
4-6
7-10
11+
1-11+
Western
Hackerel
1983-1984
-------Southern Nortb
Sea Hackerel
1970-1971
1-3
4-6
7-10
11+
176
173
31
37
-----_...13
10
2
1
------26
417
163
163
29
36
1
1
1
217
132
49
2
128
58
11
0
1-11+
920
1-3
4-6
7-10
11+
116
35
23
22
48
8
6
---176
-----15
13
8
5
23
28
31
31
1
2
3
3
----20.8
72
26
2
44
30
67
98
98
97
99
21.3
26.5
24.8
35.7
25.9
24.0
35.2
41
27
33
31
50
59
53
45
9
14
13
24
27.7
33
51
16
97
97
90
3
3
11
0
0
0
89
74
38
2
328
105
77
98.
-------41
28.3
----_.
3.4
-----1.4
56
78
100
4.6
5.5
1.5
2.6
4.3
1.5
51
---7.3
67
87
93
93
744
81
._--------._-101
87
4.2
2.1
96
4
0
86
13.6
16.7
13.1
4.9
11.9
15.5
12.1
14
23
24
22
1
4
9
4
12.0
9.7
76
20
4
1
0
0
0
--.---- ------4.6
73
68
74
22
15
17
63
65
77
5.3
4.2
6.6
4.9
2.7
4.3
3.8
97
96
87
94
2
5
13
6
----33
79
5.2
4.1
96
4
28
56
66
4.1
9.5
9.3
7.5
1.2
5.3
6.2
5.4
97
82
84
83
0
12
18
3
7
3
0
85
12
3
---196
41
---155
Soutbern Nortb 1-3
Sea Hac:kerel
4-6
1983-1984
7-10
11+
116
109
95
87
83
48
32
24
61
63
63
1-11+
407
-------_.-
76
71
66
67
----11.5
1-11+
-------220
187
------
10.1
12.2
13.3
13.6
12.3
---400
197
203
----------348
114
234
376
113
83
10.9
13.0
14.2
14.0
----94
----4 ------185
189
------.
93
94
94
97
391
--------1 ---45
44
45
"31
68
.-..-.---- ------.- -.------
72
--_..--54
8.0
---4.3
------ --------
13
• • • • • • • • • • • • • • • • • • • • • • • •~~.::!..=.:.:-::::::":"'::::=::JI
_
. - ---.;":~;...;,~~~.~.:~..~-:-"-..:,;~_:~~!""""-:- - ....._.,....~..
•
TABLE 8. The total number of mackerel examined for Anisakis, the number uninfested and infested fish, the prevalence,
the mean intensity, abundance and the degree of infestation in the infected fish (%) for the Western Mackerel,
the North Sea Mackerel and the mackerel from the southern North Sea by sex and sexes combined in 1982-1984.
Degree of infestation (%)
Population
and Period
Sex
---------...-. ••••••=-Females
Total
number
examined
Number
uninfested
Number
infested
147
Males
Both
118
4
2
•............. ........
269
6
263
Western
Mackerel
1983-1984
Females
Males
Both
743
654
1397
156
132
288
587
. ........
Southern North
Sea Mackere1
1983-1984
Females
Males
Both
.............. .
\
Mean
intensity
=======
28.0
27.5
27.7
37
34
35
:::1::::1=======
=:::1===:::1=:::1:=1
==::1===::1
11.8
9.3
9.9
9.6
79
.:::1..••..
79
80
79
522
1109
1-15 A
LOW
======:::1=•
97
98
98
116
Abundance
28.7
27.9
28.4
========-:::s.
151
North Sea
Mackere1
1983-1984
..----
%
Prevalence
12.4
12.1
D=-===llll==:::1
109
93
202
228
204
432
. ........
52
54
53
119
111
230
7.5
8.9
8.2
16-45 A
MEDIUM
46
51
48
>46 Anisakis
HIGH
======
17
16
16
======= ======
5
78
16
19
18
===:::1==::1
===:11===
=~===::s
10
3
4
77
3.9
4.9
4.4
87
83
85
14
·12
=====::s=
4
4
4
======
.'
TABLE 9. The average condition factor of the Western Mackerel, North Sea Mackerel and the southern
North Sea Mackerel in relation to the degree of Anisakis infestation in 1983 - 1984.
Western Mackerel
Degree of Anisakis
infestation per mackerel
-----------------------o Anisakis
LOW
MEDIUM
HIGH
1
15 Anisakis
16 - 45 Anisakis
> 45 Anisakis
North Sea Mackerel
--------------------
--------------------
--------------------
--------------------
Condition
factor
695
715
721
726
Number
of fish
176
569
149
27
Southern NS Mackerel
--------------------
Condition
factor
Number
of Hsh
Condition
factor
Number
of Hsh
828
627
617
752
4
62
713
755
800
739
187
187
26
7
99
33
--------------------
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dA- J~" ..