An analysis of life-history invariants in Eurasian perch, Perca fluviatilis

Questions: Can life-history traits be aggregated into dimensionless and invariant indices? Can meaningful inferences be derived from such invariants? Can important life-history traits be predicted from simple measures of growth and mortality rates'? Organism: A medium-sized freshwater fish with a complex life history, Eurasian perch (Perca fluviatilis). Perch often display one of two growth types: slow growing and small-sized (stunted), or rapid growing and large-sized (often piscivorous). Data used: Literature data from 75 populations spanning the natural distribution range of perch in Eurasia. Conclusions: Most life-history traits are related through trade-offs, and covary in a predictable manner among populations. Suggested life-history invariants could be deemed as invariant using standard criteria. However, an observed difference between growth types suggests that evolutionary inference from invariants should be drawn with caution. On the other hand, simple optimality models based on information about growth and mortality schedules do predict age and size at maturity and reproductive investment with reasonably high precision.