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The phthalate esters are a group of industrial chemicals considered to have endocrine-disrupting properties. The most common tonnage product among these, di-2-ethylhexyl phthalate (DEHP), is widely spread in the environment. The objectives with the present work were to study uptake and metabolism of orally administered DEHP and its major metabolite mono-2-ethyl hexyl phthalate (MEHP) and to evaluate the impact of early life exposure on sex differentiation in Atlantic salmon. The feeding with contaminated diet started immediately after yolk sac resorption and continued for 4 weeks. Nominal concentrations of DEHP in the diet were 400 (measured 359), 800 (measured 827), and 1500 (measured 1648) mg DEHP/kg and a control group was fed food mixed with solvent. After the exposure period, fish were fed non-contaminated diet until final sampling 4 months post-exposure. There were no effects on growth or survival of the fish and no late effects on hepatosomatic index or sex ratio. However, the histological examination of gonads from fish exposed to 1500 mg DEHP/kg revealed a small but significant incidence (3%) of intersex fish (ovo-testis). Chemical residues of DEHP and MEHP were analyzed weekly during the first 3 months of the post-exposure period. Both DEHP and MEHP were rapidly eliminated to near background levels within one week post exposure. The study indicates that exposure of Atlantic salmon to relatively high concentrations of DEHP during a sensitive part of the life cycle may interfere with gonad differentiation.

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Sea-run Baltic salmon (Salmo salar) populations have been affected by the M74 syndrome since 1974 causing high yolk-sac fry losses in Swedish compensatory rearing plants. M74 has been shown to be a maternally transmitted thiamine (vitamin B(1)) deficiency. The aim of this study was to investigate possible relationships between thiamine and hepatic activities of the thiamine-dependent enzymes transketolase (TK) and alpha-ketoglutarate dehydrogenase (alpha-KGDH) in addition to glucose-6-phosphate dehydrogenase (G6PDH) and cytochrome P4501A (CYP1A), measured as 7-ethoxyresorufin O-deethylase (EROD), in Baltic salmon yolk-sac fry after treatment with thiamine. Thiamine concentrations and activities of TK, alpha-KGDH and EROD were significantly lower (P<0.05) in M74 groups compared to controls (not developing M74) and family groups of thiamine injected females. In M74-developing groups the thiamine immersions reduced the mortality from 86 to 13% and restored thiamine concentrations and activities of TK, alpha-KGDH and EROD to levels slightly lower than the immersed controls. An interesting fact was that the controls showed significantly elevated (P<0.05) TK and alpha-KGDH-activities after immersions in thiamine, indicating that they also may have a stressed thiamine metabolism. The TK and alpha-KGDH-activities of unimmersed groups correlated significantly (P<0.05) with the thiamine content. We suggest that the low activities of TK and alpha-KGDH in M74 groups may be an integrative part in the pathogenesis of M74 development.

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Baltic salmon brood fish were investigated for the presence of Flavobacterium psychrophilum in the kidney, spleen, brain and sexual products (ovarian fluid, unfertilised eggs and milt). Samples for bacteriology were taken at capture, when the fish were ascending their native river to spawn, and after a period of captivity in indoor pools, at stripping. During captivity, abnormal wiggling behaviour was recorded in some of the fish. Bacterial samples were taken to determine if F. psychrophilum had any role in the aetiology of the condition. Furthermore, the presence of F. psychrophilum on egg surfaces during incubation was investigated. F. psychrophilum was isolated from internal organs and/or sexual products in 7 out of 50 (14.0%) fish sampled at capture and 63 out of 272 (23.2%) fish sampled at stripping. The bacteria was isolated from either spleen or gonads in 2 out of 19 (10.5%) fish with abnormal wiggling behaviour but no bacteria was isolated from the brain. No F. psychrophilum was isolated from eggs at the eyed stage. Just before hatching, the bacterium was isolated from 5 out of 15 (33.3%) family groups. The present study shows that Baltic salmon brood fish are carriers of F. psychrophilum during their spawning migration. The presence of the bacteria in sexual products from both females and males indicates that transmission from the brood fish to the offspring should be considered an important route of infection.

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The redox substrates--lactate, malate, alpha-glycerophosphate, dihydroxy acetonephosphate and pyruvate--have been determined in liver and muscle tissue from young salmon. The redox quotients have also been calculated. The freeze clamping technique was used and reliable samples of fish muscle for the determination of lactate were obtained with the aid of a pair of pliers with a gear mechanism. It was established that the lactate content in the body muscle is in close agreement with that in the blood from rested salmon parr. The concentrations of redox substrates are in good agreement with those found in mammalian tissue. The determination of the content of glycogen in fish muscle is discussed in the light of the results obtained in this study.

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