Effect of gastrointestinal microflora on the growth rate of Atlantic Cod (Gadus Morhua) larvae

The gastrointestinal tract of fish larvae is inhabited by complex and diverse groups of microbes. Both internal and external factors affect the composition of the microbiota. Until now little information is available on the correlation between gut microbiota and the growth of fish larvae. This study was carried out to test whether the growth rate of cod larvae is partially explained by the composition of their intestinal microbial communities. In this experiment, the gut microbiota of small and large cod larvae sampled at 7, 10, 14, 17, 21, 24, 28, 31, 39 and 42 days post hatching were investigated using a PCR/DGGE (Denaturing Gradient Gel Electrophoresis) strategy. The results showed significant differences in the intestinal microbiota between small and large larvae on 40% of the ages stages studied. Therefore, the composition of gut microbiota does not generally seem to contribute to the growth rate of the larvae. We further found that the variation in gut microbiota of cod larvae was less impacted by their size than by age for larvae up to 28 dph, but for the older larvae size and age influenced the microbiota equally. Negative correlations between Bray-Curtis similarity in comparisons of two-and-two larvae versus the difference in age and size between the larvae were found in this study