Scale strength as a cost of rapid growth in sunfish

Comparisons among populations have revealed adaptive variation in growth rate within several species. However, theoretical models suggest that a cost to rapid growth must exist in order to explain why some populations grow slowly. Based on previous work with development of the cranial skeleton in pumpkinseed sunfish, we proposed that rapid growth may compromise the strength of all skeletal elements in vertebrates. Using pumpkinseed from six populations known to differ in their intrinsic growth rates, we correlated strength of scales, in terms of resistance to penetration, with individual growth rate. We found a negative correlation that was consistent both within and among populations. This trade‐off between growth rate and scale strength may have fitness consequences in terms of likelihood of surviving predation attempts or swimming efficiency.