The parasite–host relationship of glochidia (Mollusca: Margaritiferidae) on the gills of young-of-the-year Atlantic salmon ( Salmo salar)

• Published in: Canadian Journal of Zoology
• Main Authors: Cunjak, R. A., McGladdery, S. E.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1991
• Subjects: Atlantic salmon; Salmo salar
• Online Access: http://dx.doi.org/10.1139/z91-055; http://www.nrcresearchpress.com/doi/pdf/10.1139/z91-055

The relationship between condition of overwintering young-of-the-year salmon (Salmo salar) and levels of infection by glochidia of the freshwater mussel Margaritifera margaritifera was investigated at two sites in South River, Nova Scotia, which contained significantly different concentrations of adult M. margaritifera. Although the salmon at site A (which had 5.1 times fewer freshwater mussels than site B) were significantly larger than the salmon at site B, there was no correlation between size of salmon and abundance of glochidia. Mean condition factor (K) was lower at site B. There was a significant increase in K in spring, which was most likely due to spring growth as there was no significant decrease in glochidia abundance. Significant, negative regressions were found only in January and February, when 24 and 66% of the variation in K, respectively, could be explained by the abundance of glochidia on the gills. Abundance and prevalence of infection did not change significantly between October and March. There was, however, a 45% decrease in infections of over 300 glochidia after December, which may have been due to host mortality. The mean size of glochidia increased between October and November, levelled off between December and March, and increased again in April. In May there was no further increase in growth, which is believed to be due to the loss of larger glochidia from the gills at that time. The data suggest an increasingly detrimental impact to juvenile salmon over winter as a function of the time and degree of infection (i.e., intensity, abundance) with mussel glochidia.