Patterns of RNA/DNA ratios in larval fish and their relationship to survival in the field

Patterns in the amount of RNA and DNA in six species of larval fish in Conc eption Bay, Newfoundland are studied. As the amount of DNA increases, the d istribution of the ratio of RNA to DNA contracts towards its highest values . This is interpreted to mean that RNA/DNA is an indication of survival pro bability, and that survival probability is a quantity that tends to persist through a larva's hfe. Comparisons among species indicate that the greates t degree of contraction (the strongest selection pressure) is associated wi th the highest mortality rates. There is evidence that variability in RNA/D NA is introduced around the time of yolk-sac absorption. (C) 1999 Internati onal Council for the Exploration of the Sea.