ICES Journal of Marine Science: Journal du Conseil

Lang, T.; Mellergaard, S.; Wosniok, W.; Kadakas, V.; Neumann, K.

doi: 10.1006/jmsc.1999.0465pmid: N/A

Information on prevalences of grossly visible diseases and parasites of flounder (Platichthys flesus) from the Baltic Sea is presented for 11 sampling areas on a transect from the Mecklenburg Bight to the Gulf of Finland. Among the 3008 flounder examined, highest overall prevalences were observed for lymphocystis (14.4%) and acute/healing stages of the skin ulcer disease (5.9%). The prevalences of liver neoplasms >2 mm in diameter (0.4%), skeletal deformities (0.6%), and fin rot/erosion (0.5%) were low. The only externally visible parasite recorded was Cryptocotyle concavum (28.2%). The results of a multivariate statistical analysis reveal that the diseases are influenced by a variety of host-specific (length, age, sex) and area-specific (salinity, temperature) factors as well as their interactions. By calculating the expected prevalence for a standardized fish population for each area and disease, the extent of area-specific effects not attributable to host-specific factors was estimated.

Bogovski, S.; Lang, T.; Mellergaard, S.

doi: 10.1006/jmsc.1999.0461pmid: N/A

Grossly visible hepatic nodular lesions in 34 flounder collected during the BMB/ICES Sea-going Workshop “Fish Diseases and Parasites in the Baltic Sea”, 25 November to 8 December, 1994, are described histopathologically. Foci of cellular alteration were recorded only in three fish from the southwestern Baltic Sea, whereas foci of cellular alteration and liver neoplasm’s occurred in nine and six fish, respectively, from the northeastern sampling area. The overall prevalence of confirmed preneoplastic and neoplastic lesions was estimated at 0.6 and 0.9%, respectively.

Bogovski, S.; Sergeyev, B.; Muzyka, V.; Karlova, S.

doi: 10.1006/jmsc.1999.0462pmid: N/A

Concentrations of cytochrome P450 (CYP), activities of aryl hydrocarbon hydroxylase (AHH), haem synthetase (HEM-S), and 5-aminolevulinic acid synthetase (ALA-S) in liver as well as fluorescent aromatic compounds (FACs) in bile of flounder (Platichthys flesus) were studied in samples collected during a synoptic survey along a transect in the Baltic in autumn 1994. Cytochrome P450 concentrations and activities of the haem synthesis enzymes HEM-S and ALA-S were highest in the northwestern areas and among these parameters significant (p<0.01) positive correlations were found. Highest activities of microsomal AHH were measured in flounder from areas near major ports in the centre of the transect. Concentrations of FACs in bile correlated significantly with AHH activities. The results indicate that CYP concentrations and ALA-S and HEM-S activities, which are generally considered the principal biomarkers of carcinogenic pollution, may give a different perspective on carcinogenesis in fish.

Køie, M.

doi: 10.1006/jmsc.1999.0463pmid: N/A

In connection with the BMB/ICES Sea-going Workshop “Fish Diseases and Parasites in the Baltic Sea”, 200 specimens of flounder Platichthys flesus from eight stations (25 from each) distributed from the southwestern (Mecklenburg Bight) to the northeastern Baltic Sea (Gulf of Finland) were examined for metazoan parasites. A few species (e.g. Hysterothylacium aduncum, Cucullanus heterochrous, Cucullanellus minutus, and Pomphorhynchus laevis) were found at virtually all stations. Typical “marine” species (Podocotyle atomon, Brachyphallus crenatus, Anisakis simplex, Holobomolochus confusus, and Lernaeocera branchialis) were found at the western stations only, whereas the metacercariae of Diplostomum spathaceum, and Cotylurus sp., immature Corynosoma sp., the larvae of Raphidascaris acus and Contracaecum osculatum were most common towards the east and north. Echinorhynchus gadi only occurred at the western and southern stations. The small encapsulated larvae of the bird nematodes Contracaecum sp., Paracuaria sp., and Cosmocephalus sp. were found at most stations. The effects of salinity on the patterns observed in relation to the distribution of intermediate and final hosts are discussed.

Mellergaard, S.; Lang, T.

doi: 10.1006/jmsc.1999.0466pmid: N/A

During the 1994 BMB/ICES Sea-going Workshop “Fish Diseases and Parasites in the Baltic Sea”, the prevalences of skin ulcers, pseudobranchial swellings (X-cell disease), skeletal deformities, and the parasites Cryptocotyle lingua and Lernaeocera branchialis were recorded in cod in 11 areas from the Mecklenburg Bight in the southwest to the Estonian coast in the northeast of the Baltic Sea. Prevalences were highest in the western part, except for skeletal deformities, which were highest in the central part. The spatial distribution of pseudobranchial swellings, C. lingua and L. branchialis appeared to be restricted to areas with salinity above 8. Skin ulcers were mainly observed in German waters, while skeletal deformities were most abundant in the Polish, Russian, and Lithuanian coastal zones.

Grygiel, W.

doi: 10.1006/jmsc.1999.0467pmid: N/A

During the BMB/ICES Workshop on “Fish Diseases and Parasites in the Baltic Sea”, 25 November to 8 December 1994, samples of herring Clupea harengus and sprat Sprattus sprattus taken along a transect from the southwestern to the northeastern Baltic Sea were examined externally for the presence of symptoms of diseases and emaciation, and internally for infestation with Anisakis simplex. The results indicate significant geographical differences in the prevalence of all three symptoms in herring, but the interpretation is complicated by the apparent size dependence. This was not the case for sprat, but the much lower prevalence of diseases and emaciation may have prohibited the detection of a significant effect.

Wiklund, T.; Tabolina, I.; Bezgachina, T. V.

doi: 10.1006/jmsc.1999.0464pmid: N/A

Ulcerated fish of six different species were collected during the BMB/ICES Sea-going Workshop “Fish Diseases and Parasites in the Baltic Sea”, 25 November to 8 December 1994, and examined for bacteriological infections. Atypical Aeromonas salmonicida strains were isolated from the majority of the ulcers of dab Limanda limanda, flounder Platichthys flesus, and turbot Scophthalmus maximus. A fast-growing strain was isolated in pure cultures from both ulcers and visceral organs of viviparous blenny Zoarces viviparus. Available data suggest that atypical A. salmonicida is generally involved in the development of ulceration’s in Baltic flounder and probably also in other fish species. The strains isolated from ulcerated flounders were indistinguishable from those previously reported from this species from the Baltic Sea and the North Sea, and the ulcer disease is considered to be associated with one, well-defined biotype of A. salmonicida.

O’Brien, C. M.

doi: 10.1006/jmsc.1999.0447pmid: N/A

The fishing mortality which results in stock collapse is difficult to ascertain. As a proxy, an estimate of the fishing mortality where the equilibrium spawning stock is zero has been defined previously as the replacement line which corresponds to the lowest observed spawning stock. A number of problems of estimation are raised in the calculation of the uncertainty associated with the slope of this line and these are discussed in this note.