Two-year cyclicity in recruitment of a fish population is driven by an inter-stage effect

• Published in: Population ecology 2014-07, Vol.56 (3), p.513-526
• Main Authors: Marjomäki, Timo J, Urpanen, Olli, Karjalainen, Juha
• Format: Article
• Language: English
• Subjects: Age groups; Animal populations; Animal reproduction; Behavioral Sciences; Bias; biomass; Biomedical and Life Sciences; Cohort effect; Compensation; Competition; Coregonus; Coregonus albula; Correlation analysis; Delayed density dependence; Ecology; Evolutionary Biology; Fish; Fish populations; Forestry; Generation cycle; larvae; Life Sciences; Maternal effect; Mathematical models; Mortality; Original Article; Parental effect; periodicity; Plant Sciences; Population; Population density; Population growth; Population regulation; recruitment; skeleton; Spawning; Time series; time series analysis; Wind; Zoology
• ISSN: 1438-3896; 1438-390X
• DOI: 10.1007/s10144-014-0439-0

A 25-year time series for a vendace (Coregonus albula (L.)) population was analysed with mathematical models to reveal the factors that regulate its recruitment. The fitted recruitment model was an age-structured model incorporating the compensatory effects of the spawning population and the abundance of the previous year class. Wind forcing index was also added as an example of an external source of recruitment variability. The auto-correlation analysis revealed a tendency for 2-year generation cyclicity in recruitment. The compensatory effects of both spawning biomass and previous year class abundance on recruitment had to be incorporated into the model to remove cyclicity from residuals. Wind forcing during the larval and early juvenile periods negatively affected recruitment. Re-estimating the parameters of the Cushing recruitment function and the effect of previous year-class from simulated data revealed that the time series structure and measurement errors induce strong biases in parameters exaggerating the density independent population growth rate parameter and the amount of compensation. The negative effect of previous year class was also exaggerated but less severely. Simulations with the artificially perturbed deterministic model skeleton revealed a tendency for cyclicity in recruitment. The model typically generated dampening oscillations, but the dynamics appeared as limit cycles when assuming high mortality, a low level of compensation by spawning biomass and a considerable negative effect of the previous year-class. No single ultimate mechanism for inter-stage effects causing cyclicity can be presently designated despite the rather extensive studies on vendace population dynamics. Several of the suggested mechanisms may be operating in concert.