Article published in Marine Ecology Progress Series

In a new article published in Marine Ecology Progress Series, ConEvolHer members Fabian Zimmermann and Mikko Heino present together with Daniel Ricard from Fisheries and Oceans Canada an analysis on how intra-specific interactions influence recruitment in Atlantic fish stocks. Intra-specific interactions include cannibalism of older on younger cohorts or competition between cohorts and are considered to be important drivers of recruitment dynamics in many marine fish stocks.

The study attempted to quantify the relevance of these interactions by analysing the autocorrelations of residuals from Ricker stock-recruitment models that were fitted to time series data of 112 fish stocks from the Atlantic.

Significantly negative autocorrelations were found for time lags of three to five years, indicating that the recruitment in the current year is substantially influenced by the cohort size of three to five years ago. This result was also found for, among others, Norwegian spring-spawning herring at a lag of three years. Furthermore, a large amount of stocks with significantly positive autocorrelations was detected, in particular for time lags of one or two years. This reflects that recruitment dynamics are subject to density-independent drivers such as environmental factors that may cause several subsequent year classes that are unexpectedly strong or weak. Additionally, it underlines potential problems with output data from stock assessments models, specifically the spill-over effect through ageing errors. Overall, the story provides methodological groundwork and useful insights for ongoing research in ConEvolHer on recruitment variability.

Ricard D, Zimmermann F, Heino M (2016) Are negative intra-specific interactions important for recruitment dynamics? A case study of Atlantic fish stocks Mar Ecol Prog Ser 547:211-217