OF THE

Complete parasitological analysis of the grey gurnard Trigla gurnardus (L.) had been carried out on Shetland Islands fishing grounds. Material was collected at random from commercial catches in March 1976. Generally, the presence of 14 species of parasites was ascertained (Protozoa - 1; Cestoda - l; Trematoda - 7, Nematoda - 3, Crustacea-Copepoda - 1, and Fungi - 1 species). Frequency of their prevalence, as well as intensity and incidence were determined. Ten species were found first time as occuring on the grey gurnard.


INTRODUCTION
Grey gurnard Trigla gu,rnardus (L.) is one of the most common fishes out of the family Triglidae. It is widely distributed along coasts of Europe, from Murmansk to the Black Sea. The species belonging to family Triglidae are little known from the parasitological standpoint. Most papers concern the parasitic fauna of the red gurnard Trigla lucerna (L. ), and grey gurnard. But these works have rather accidental character not giving complete picture. Most frequently the authors describe single parasites belonging to the different taxonomical groups. For instance, Margaritov (1965) describes Contracoecum fabri (Rudolphi, 1819) on the red gurnard from Black Sea. Similarly, Pogoreltseva (1952) desceibes two species of nematods from Trigla hirnndo (L.) coming from the Black Sea too. Agraval (1964) described trematod Helicometrica indica n.sp. from intestine of the grey gurnard. Most attention had been paid to the parasitic Copepoda. One of more extensive works concerning several species of Lernaeopodidae occuring on gurnards from European waters is Nunes-Ruivo's (1957) paper. Parker (1965) worked out crustaceans from the genus Caligus for the same area.
The aim of this work was to get possibly fully acquainted with parasitic fauna of Trigla gumardus from the particular fishing area. Such surveys may gain real meaning for the practical purposes in the future, in view of continuous increasing of exploitation of species that were slightly utilized for human consumption up to date.

MATERIAL Al"\J"D METHOD
There were examined l 00 specimens of grey gurnard -Trig la gumardus which have been caught in North Sea near Shetland Islands. Material was collected during fishing operations when 5-10 fishes have been taken from particular haul. Dimensions of examined fishes were in the limits -length (longitudo corporis) -22(2 7-41 )48 cm, and weight 160-1100 grams. Material has been freezed, and later, in the laboratory its examination was carried out.
Skin, fins, oral cavity, gill cavity, muscles, body cavity, and alimentary canal were examined. The parasites were preserved in 75% alcohol, and physiological saline with 4% of formaldehyde. Tapeworms and trematods have been partially flattened. The stable preparations were mounted after staining in Canada balsam; nematods were mounted in glycerine.

Miscrosporidia
Three yellowish cysts (1 and 2) were found in two fishes. They were clearly visible, their dimensions were 10 X 4 mm. They were located in the musfles of belly lobes. Distinctive changes were noted in the tissue surrounding the cysts. Muscle tissue around them was liquefied and had spongy consistence.

Platyhelminthes
Cestoda Grillotia erinaceus (van Beneden, 1858) - Fig. 1 Only one tapeworm in the form of encysted larva -plerocercoidus was found in the examined samples. It was located in the body cavity in stomach vicinity. It could not be excluded that it was accidental infestation. The species rare in the examined material, it was ascertained in 4% of cases with intensity of 1-3 parasites per fish. Trematods were occuring in the intestines, and in only one case in stomach. All juvenile individuals.
Rhipidocotyle galeata (Rudolphi, 1818) - Fig. 3 It was occuring in the intestine much more frequently the Bucephalopsis. Incidence reached 16%; there were encountered up to 7 parasites in one· fish. Mean number of parasites per fish was over 4 times higher than in the case of preceding species.

Lepidapedon sp.
Only one time 3 specimens were found in one fish. Parasites were highly macerated as a result of freezing. During preparations they have undergone almost complete disintegration, and were difficult to recognize in details.
Hemiurns levinseni Odhner, 1905 -Fig. 5 It belongs to the most frequently occuring. parasites of the grey gurnard. It was found in 31 % cases with intensity of 1-5 trematods per fish. Occurs mainly in stomach ( 68 fishes), while in the intestine of 4 fishes only.
Hemiurns luehei Odhner, 1905 -Fig. 6 Occurs more rarely than preceding species (incidence only 9% with intensity of 1-4 trematods) mostly in the intestine, but met in the stomach also. It is also common parasite of grey gurnard. It has been encountered in 19 fishes, in number of 1-5 specimens per one fish. It is occuring in the stomach exclusively.

Nematoda
Thynnascaris adunca (Rudolphi, 1802) - Fig. 8 (syn. Contracoecum aduncum (Rud., 1802) The nematod belonging to common parasites of many species of fishes. In examined grey gurnards it was occuring at 70%. Those were larvae representing III and IV stage, almost exclusively found in the intestine, only few in the stomach. One adult specimen (female) was rather incidently met in the gill cavity. Number of parasites per one fish amounted up to 107 individuals. Stage III outnumbered 2.5 times stage IV. The species most frequently noted in the examined material. All surveyed fishes were infested by this parasite, and all parasites were in the larval stage III. They have occured in the stomach walls, and in the body cavity, less frequently on the liver, on stomach, and gonads. Three specimens were met under peritoneum of body cavity. Intensity of infestation was 9-163 of nematods per fish. Mean intensity of population was 64.18. Totally, 6418 parasites were collected.

Capillaria sp.
In 7 fishes there were found fragments of 5-16 cm length being in a bad shape. It made closer identification impossible.

Copepoda parasitica
Brachiella obes (Krc,yer, 1837) - Fig. 10 They were found on 10 fishes, maximally up to 6 individuals per one fish, attached to the gill arch appendages. They were sporadically met in the oral cavity. Females exclusively. Ichthyophonus hoferi (Plehn et Muslov, 1911) Found at 88 fishes on the outside walls of intestines in the form of 2-3 mm cysts.
The least invasion rate show Microsporidia, Grillotia erinaceus, and Lepidapedon sp., and they could be treated as incidental parasites. But on the other hand, Ruszkowski (1934)  were the rare parasites in the surveyed material. Their mean intensity of infestation of fish population, as well as incidence were relatively low.
Out of encountered species of trematods, the. Sterigophorus furciger and Bu cephalopsis gracitescens were relatively frequently reported from Atlantic Ocean. They have been found in Barents Sea (Polianskij, 1955), in Japan Sea, and Okhotsk Sea (Zukov, 1960). Along the coasts of Great Britain, Sweden, and Shetlands, St. furciger occurs mainly on fishes from families Pleuronectidae and Cottidae, as well as on eels, and members of Liparldae family (Koval, 19 57), while Bucephalopsis gracitescens most frequently noted on fishes from Gadidae, Lophidae, and Belonidae family (Skrjabin and Gusanskaya, 1962). Hemiurus luehei is much more seldom reported in the literature. It occurs in Northeast Atlantic, North Sea and Baltic Sea, mainly in clupeoid fishes. Closer description of this species occurence on Salmonidae is given by Slusarski (1958).
Similarly, so frequently cited in a literature are Derogenes van· cus, and Rhipidocotyle galeata. Dolffus (1953) reports occurence of first species on the grey gurnard from English coasts, while second is noted by Skrjabin and Gusenskaja (1962).
The larvae of nematods Thynnascaris adunca and Anisakis simplex may be regarded as very common parasites of the grey gurnard. Because of the pathogenicity of Anisakis for humans {J. Grabda, 1976a) necessary precautionary measures should be undertaken in the use of grey gurnard for consumption.

CONCLUSIONS
1. Parasitic fauna of the grey gurnard is differentiated qualitatively and quantitatively. 2. With regard to number of species the most numerous group is Trematoda -7 species.
On the other hand the strongest infestation was caused by Nematoda ( on the average -84 nematods per fish). Such parasites as Microsporidia, Grillotia erinaceus, Lepidapedon sp. should be regarded as rather incidental. 4. The only parasite pathogenic for man is frequently occuring Anisakis simplex. With respect to ubiquitous occurence of its larvae (in gonads, liver, and muscles especially), in the case of use of the gray for human consumption, all necessary prophylactic measures proposed in a literature should be applied. 5. Parasites: Microsporidia, Bucephalops_ is gracitescens, Lepidopedon sp., Steringophorus furciger, Hemiurus levinseni, Hem luehei, Thynnascaris adunca, Anisakis sunplex, Capillaria sp., and IchthyophoYllls hoferi were not reported as occuring on grey gurnard up to date.