ICES 1996 PAPER C.H. 1996/J:28 Baltic Fish Committee . \":~~:.i, 1 --_..:.-:.--',n i "."'1 '" MORBID SYMPTOMS OBSERVED IN BALTIC FISH DURING Two RESEARCH CRUISES IN 1995 AND 1996 by M. Kosior, W. Grygiel, J. Kuczynski, K. Radtke and M. \Vyszynski Sea Fisheries Institute, ul. Kon~taja 1,81-332 Gdynia, POLAND ABSTRACf. In June 1995 and April 1996, ~o research cruises took place whose purpose was to conduct observations of the health state of fish caught within the boundaries of the Polish fisheries zone in the Baltic Sea. The symptopms of diseases, such as lymphocystis, ulceration, skeletal deformations and epidermal hyperplasia, in herring, sprat, cod, flounder, eeipout and four-bearded roclding were recorded. In case ofthe remaining species, constituting a by-catch in the control hauIs, no pathological changes were observed. 2 11'liRODUCfIO:" Pathological changes began to be observed in Baltic fish as far back as the 1930s (Jaekel 1931, Lundbeck 1928). However, more frequent studies were undertaken only in the 1970s. Vitinsh et al. (1976) described the occurrence of the symptoms of lymphocystis in Baltic flounder. According to Grawiriski (1987), an increase in pathological changes in cod and flatfish had already occurred since 1975. Those changes were mostly in the form of ulcers, abscesses and tubercles present over the whole body surface. Kosior (1992) reports that the pathological changes of this type in the form of ulceration were already observed at the beginning of the 1970s. Initially, these changes occurred in cod caught in the area ofthe fishing grounds in the Bornholm Deep, and then, in the Gdarisk Deep. As the cod stock size increased, the prevalence ofdiseases began to be observed. lengen and Larsen (1982) describe the symptoms of the ulcer disease in cod from the western Baltic. Möller (1981) described ulcerous changes in cod from the Mecklenburg Bay in 1980. Lisiriska and \Vik'tor (1985) made an evaluation of the health state of fish from the southern Baltic in 1980-1985 and proved that ulceration on the body surface of cod intensified in the spring. These authors reported that, in the examined period, 1983 was characterized by one of the highest frequencies of all the diseases in all the fish species exploited by the Polish cutters. During the cruises on board rv PROFESSOR SIEDLECKI in 1981-1989, the evaluation of the health state of fish was made in the whole Polish fisheries zone. Since 1980, at the Sea Fisheries Institute, systematic research has been carried out aimed at estimating the extensiveness and intensiveness of the pathological changes in fish caught in the southern Baltic. From this research, it emerges that, in 1986, the highest frequency ofdiseases was recorded (Rutkowska 1986, 1987 and 1990). The purpose ofthe cruises (1995 and 1996) was to collect materials for the monitoring of anatomo-pathological changes in cod, herring, sprat, flatfish, eelpout and four-bearded rockling, as weIl as to make the evaluation of the possible changes in the extensiveness of the diseases distinguished. MATERL\LS A.'\Il.METIIODS In lune 1995 and April 1996, ten-day surveys took place on board rv BALTICA aimed at determining the health state offish inhabiting the southern Baltic-within the boundaries ofthe Polish marine fisheries zone. While caI1)ing out the program of the cruise, apart from control hauls of fish, the values of the selected hydrological parameters (water temperature, salinity ----~~------- --- --- -- f,_,1 • .' 3 and oxygen con,tent) were recorded in the places where the hauls were perfonned. Also, sampies were collected in order to determine pollutants in fish tissue. In "the catches, herring bottom trawl, type P20/25: with a fine-mesh' insert of a mesh bar length of 6 mm was used. The hauls lasted 30 minutes. From every haul, all the fish caught were sorted out according to the species. Their total length was measured and they were weighed and visually assessed in order to detennine their health state. Fish in which extemally visible diseases were detected were subjected to a detailed analysis. Catches were perfonned at the selected stations, in three ICES-Subdivisions (~4, 25 and 26), with two to three hauls in every ICES-rectangle. In the first phase of the cruise, hauls were perfonned at a depth between the isobaths of60-70 m, starting with the fishing grounds ofthe Gulf of Gdansk in the westerly direction. On the way back, hauls were conducted at a depth between the isobaths of20-30 m (Fig. 1). During the research, extemal pathological changes were recorded, as weIl as skeletal defonnations, such as dwarfism, vertebral column anomalies, pugheadedness, and others. In order to assure the comparability of the research results, the pathological changes were described basing on the instructions and fish body map used in the previous years. Data were recorded including the examined species, -type of the pathological changes and their characteristics, as weIl as a schematic diagram ofthe symbols for the parts offish bodies for the records of the information about the external pathological changes. These instructions were based on the guiding principles of the leES Working Group dealing with the Pathology and Diseases in Marine Organisms. The number of the fish examined is given in Table 1, and the places of cotrol hauls are • shown in Fig. 1. RESULTS Materials collected during the surveys provided. sampies which were not burdened with the effects of the selectivity of commercial fishing gear and the discards of fish with visible pathological changes by fishennen. The results complement the monitoring research conducted every year on the fishing grounds ofthe southem Baltic. Pathological changes in herring, sprat, cod, flounder, plaice, eelpout and four-bearded rockJing were recorded. In case ofthe remaining species, constituting a by-catch in the control hauls, no anatomo-pathological changes were observed (Tab. 1). ------.. _- ._. r " Cl . 4 The extemally visible pathologigal changes on fish were determined as folIows: I Iymphocystis, uleeration, skeletal defonnations and epidennal hyperplasia. "Lymphoeystis and ulceration beionged to the diseaSes most frequently reeorded. Lymphoeystis was observed in a large number of flounder, and of the pelagic fishes, only in low prevalence in herring. Uleeration occurred in case of six of the examined bottom and pelagie fish speeies; however, the extensiveness of these changes was different. Uleeration most frequently oecurred in ease of bottom fishes. This is espeeially noticeable in the results obtained during the cruise in 1996 (Tab. 2). Taking into account the number of the fish examined, eod is first in order in relation to disease frequency, then, there are eelpout, flounder and four-bearded rockling. Skeletal defonnations in the fonn of dwarfism were most frequently observed in eod. In a small number of herring and sprat, vertebral column anomalies and the pugheadedness of the individuals were reeorded. Whereas in none ofthe examined fish were papillomatosis or fin rot found. It was observed that, in several eases, a few different diseases oecurred in a single fish. This was most oRen the ease with flounder, and more rarely, with eod, as weIl as with herring. Analyzing the results obtained from both the cruises, it ean be said that the anatomieal­ pathologieal ehanges reeorded in fish eaught in the southem Baltie have a different prevalenee, depending on the investigated area (Tab. 3). And thus, in the fish inhabiting the Borholm Deep area, a higher disease frequeney was determined than in the fish from the Gdansk Deep area. This refers mainly to eod and flounder. By contrast, the situation is not so uriequivocal in ease of eelpout and four-bearded roclcling (also bottom speeies), which may have resulted from a smaller number ofthe fish eaught. Eelpout oecurred in the catches only in the GulfofGdansk. In fish belonging to this species, only the ulcer disease was observed. In the cruise in 1995, eelpout with uleeration constituted around 0.5%, and in 1996, as mueh as 6.1 %. In four-bearded rockling, whieh oceurred in a small number in a few hauls, only ulceration was detected. This disease oceurred in the majority of cases in speeimens from the Gulf of Gdansk. The observations of the extensiveness and intensiveness of the occurrence of helminthofauna in fish indicated that, in around 1 thousand examined herring, in 9%, the Anisakis spp. larvae occurred. In Sub-division 25, this constituted 13.3% ofthe examined fish, and in Sub-division 26, only 4.6% ofthe fish examined. 5 The occurrence of pathologically emaciated herring and sprat" was observed (4.6% and 0.15%, respectively). References Elwertowski. J .• J. Netzel. 1985. Wyniki badan nad zdrowotnosci q ryb polawianych w polskiej strefie rybackiej w latach 1980-1985. Hor. Inst. Ryb., Gdynia (mimeo). Grawinski. E. 1978. Choroby ryb dorszowatych (Gadidae) flqdrowatych (Pleuronectidae) Horza Baltyckiego. Hed. Weter.; 404. Jaekel. S. 1931. Uber Fischsterben in der westl ichen Ostsee. Hitt. Deutsch. Seefisch. Ver., val. 47. no 11/12. Jensen. N. J.. J.L. Larsen 1982. The ulcus-syndrome in Cod (Gadus morhua). IV. Transmission Experiments with t~o Viruses Isolated from Cod and Vibrio anquillarum. Nord. Veto - Veto - Hed., 34. 135-142. Kos i or. H. 1992. Dorsz ba ltyck i (Gadus morhua L. ). In: Po l owy i stan zasob6w dorszy i storni w Baltyku (1980-1990). Stud. i Hater. Horsk. Inst. Ryb .• Gdynia, sero B, nr 59. Lisinska. K., J. Wiktor. 1985. Stan zdrowotny ryb Baltyckich na tle proces6w eutrofizacji zanieczyszczenia Baltyku. Hor. Inst. Ryb., Gdynia. Lundbeck. J. 1928. Beobachtungen über Hissbildungenunc Erkrankungen von Dorschen an der ostpreussichen Küste. Z. Fischerei, 25; 457-472. Höller. H. 1981. Fish diseases in German and Danish coasta~ waters in summer 1980. ICES, C.H. 1981/E: 25. Rutkowska. I. 1985. Stan zdrowotny ryb uzytko~ych polskiej strefy rybol6wstwa baltyckiego.