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The Problem
The Arctic charr (Salvelinus alpinus) in the northern most latitudes migrate to the ocean in the spring to feed and grow. This results in accumulation of polychlorinated biphenyls (PCB) in their visceral fat. During the winter, the charr reside in freshwater lakes and do not feed. They do mobilize lipids from adipose tissue for energy, which results in a re-distribution of PCBs to organs such as brain, spleen and heart. Results of this project will help to describe the effects of PCBs on physiological processes of charr and other salmonids. This project is funded under reimbursable agreement number 0PP-9908890 with the National Science Foundation. Objectives The long term objective of the work is to investigate the impact of persistent organic pollutants (POP) on critical tissue function and performance of anadromous Arctic charr. We will test two hypotheses: (1) the tissue re-distribution of PCB and their sublethal impact is tightly linked to metabolic status of the animal and (2) the tissue redistribution of PCB associated with fasting will decrease the overall performance charracteristics of the animals. Experiments will be performed in Norway, at the Kårvik Research Station, Tromsø and at a hatchery in Talvik, northern Norway. Methodology Hatchery-reared Arctic charr will be contaminated with one of four concentrations (0, 1, 10, 100 mg/kg fish weight) of Aroclor 1254 by force-feeding it in a capsule. After contamination, some fish will be fed and others will be starved to simulate the nutritional status of fish in the wild. After six months, physiological responses of the fish will be tested. Tests will include: disease resistance and innate immune response, stress response, saltwater adaptation, and metabolic responses. These physiological responses will be measured by looking at the whole animal response (e.g., survival), biochemical response (e.g., hormone or cytokine production) and molecular response (i.e., gene transcription).
Highlights and Key Findings In 2000, we conducted experiments with hatchery charr that had been treated with 0, 1, 10 or 100 mg of Aroclor 1254 per kg body weight. All of these groups were fasted, but other fish in the 0 and 100 treatments were fed from the time of exposure until just before our experiments. The exposures were completed in Feb 2000. We conducted the following experiments: (1) disease challenge: 40 marked fish from each group were exposed to other fish that were infected with the fish pathogen Aeromonas salmonicida, the causative agent of furunculosus. We observed a dose-dependent increase in mortality of the fasted fish, with mortalities of 32, 42, 52, and 55% in the fish treated with increasing doses. We are in the process of assaying fish from each treatment that were not exposed to the pathogen for plasma, muscus and nare lysozyme, and plasma lectin, (2) handling stress after which fish were sampled at 1, 3, 6, 12 & 23 hours. We found a dose-dependent decrease in maximum plasma cortisol responses (Jørgensen et al., 2002) (3) Plasma and tissues from treatment and control fish that were not stressed or exposed to pathogen were collected and will be assayed for a number of physiological variables. In 2001, fish were treated with the same doses of Aroclor 1254 and we are assaying these to determine the mechanisms by which the contaminant reduced disease resistance and dampened the stress response. Where Are We Headed In 2003 The National Science Foundation, the funding agency, has granted a no-cost extension for this project to December 31, 2003. During this year, we will complete three pending publications and prepare a proposal to continue this project. In the continuation project, we hope to collect maturing fish from two sites--one in which fish are heavily contaminated with PCBs and another where they are not. The fish will be taken to the Kårvik Research Station where they will be spawned and the progeny reared to determine if contamination of the parents has effects on the offspring. Project Contact Alec G. Maule Email: alec_maule@usgs.gov Publications |
