Extensive larval dispersal and restricted movement of juveniles on the nursery grounds of sole in the Southern North Sea

Abstract

Connectivity between spawning and nursery grounds influences the colonization, replenishment and resilience of populations of marine organisms. Connectivity rate, measured as the exchange of individuals between spawning and nursery grounds, is therefore a crucial determinant of stock size. However, connectivity of early-life stages is hard to explore due to sampling limitations and insufficient knowledge on potential larval sources. Here we present new insights into pre- and post-settlement dispersal of the common sole (Solea solea L.) at a spatial scale of 5–500 km in the Southern North Sea. Patterns at a scale of <100 km were considered local, whereas patterns further than 100 km were considered regional. Multi-elemental signatures of the otolith edge of 213 juvenile sole were used to discriminate at 79% of overall accuracy three main nursery grounds in the Southern North Sea, namely UK coast, Belgian coast and Dutch Wadden Sea. Interregional differences in otolith composition (especially for Mg, Mn and Ba) suggest that sole migration following settlement is limited in the Southern North Sea. Elemental signatures of the same fish indicated mixing during larval dispersal. Each nursery ground recruited an important mix of juveniles from three of the four chemically distinct natal sources identified from the larval otolith signatures. However the percentage of correct regional re-assignment varied from 67 to 80% with a maximum in the Wadden Sea. The results contributed to the validation of biophysical models of larval drift. Our findings support decision making for both fisheries management and marine spatial planning at the national and European level.