[Relationships between basic life history parameters and population size]

Area of Science:

• Population Ecology
• Theoretical Biology
• Ichthyology

Background:

• Stable age composition in populations is crucial for ecological modeling.
• Understanding life history parameters like maturity and reproduction is key to population dynamics.
• The Bertalanffy function is a standard model for individual growth.

Purpose of the Study:

• To develop a model for population dynamics incorporating age structure and individual traits.
• To establish relationships between population size, fecundity, and survival.
• To propose a method for calculating the age of maturity and reproduction period.

Main Methods:

• Utilized the Lotka equation for population dynamics with stable age composition.
• Assumed constant population size, age-independent mortality, and linear fecundity-weight relationship.
• Employed the Bertalanffy function to describe individual growth and identified inflection points for maturity.

Main Results:

• Derived a formula relating initial generation numbers to mature population size, mean weight, sex ratio, specific fecundity, and larval survival.
• Established distinct relationships for fish populations below and above 100g, and an overall relationship.
• Calculated age of maturity and reproduction period using growth rate curve inflection points.

Conclusions:

• The study provides a quantitative framework for understanding fish population dynamics based on life history traits.
• The proposed method for determining maturity and reproduction periods offers a novel approach.
• Empirical data from Russian freshwater fish populations support the derived relationships.