MEPS 349:309-310 (2007)  -  DOI: https://doi.org/10.3354/meps07282

ABSTRACT: On the basis of prior information on Atlantic cod Gadus morhua in the eastern North Sea region, including larval drift, location of spawning sites, and genetic characterisations, natal homing was thought to be the most parsimonious explanation of the juvenile and adult distributions. We tested this hypothesis in an archival tagging experiment that gave clear evidence of non-random migration runs toward remotely situated spawning grounds during the reproductive season, inferring strong support for natal homing (Svedäng et al. 2007; Mar Ecol Prog Ser 345:1–12). Bradbury & Laurel (2007, this volume) found this inference ambiguous, as the whole life cycle was not embraced in a single study, i.e. due to obvious logistical problems, single individuals had not been tracked from fertilization to spawning. We consider that none of the major hypotheses on population structuring mechanisms should a priori be given precedence, and the likelihood for environmental forcing versus natal homing should be inferred on the basis of the accumulating facts at hand. Admittedly, our understanding could be strengthened through testing whether the behavioural entities comply with their postulated population origin, using natural natal tags. Promisingly, efforts are being made that will eventually shed further light on this important issue.

KEY WORDS: Atlantic cod · Environmental forcing · Inference · Natal homing · Marine fish · Population structuring mechanism