A concept of quantitative reproductive senility: application to the hard clam, Mercenaria mercenaria (L.)?

Quantitative reproductive senility occurs when older age classes achieve less reproductive effort than expected from the allometric (power) curve relating body size to reproductive effort among younger adults. Quantitative senility can be detected by analyzing whether age explains any of the residual variance around the linear regression of log reproductive effort on log body size among all adults. In each of two collections of m. mercenaria made early in successive (1980 and 1981) breeding seasons, variation in mass of gonads (reproductive effort) was better explained by clam length than by clam age, and age failed to explain a significant amount of residual variance in the regression of log gonad mass on log body length. Among M. mercenaria from North Carolina (USA) up to age 19, there is no evidence of either absolute or quantitative reproductive senility.