UW Aquatic & Fishery Sciences Quantitative Seminar
NOAA Northwest Fisheries Science Center
Maternal Effects and Rockfish Population Dynamics
The discovery of age-dependent maternal effects in rockfish (genus Sebastes) has attracted attention to the truncated age-structure in harvested rockfish populations. Several researchers have suggested that, for some rockfish, population productivity is intertwined with population age-structure. This has raised the concern that fishing reduces population productivity even more than expected because of the elimination of older age cohorts. However, little is known about the ecology of maternal effects. I will present the data for maternal effects in rockfish and discuss these observations in the context of the early life history ecology of rockfishes. I then use models to calculate the population impact of maternal effects. I measure population impact with two metrics: recruitment and time to recovery from an overfished state. To calculate recruitment, I employ a multivariate Beverton-Holt stock-recruitment model coupled with a maternal effects model. I then use this stock-recruitment model, nested within a population simulation, to calculate time to recovery. Both metrics are reported as a function of the the magnitude of the maternal effect and the survival and mortality rates of the pre-recruitment period. I demonstrate that maternal effects can have a significant population impact under a broad range of circumstances. However, the magnitude of the impact depends on the ecological context. I report a rough estimate of the magnitude of error that can be expected due to ignoring maternal effects in recruitment estimates.