Spawning time of Atlantic herring (Clupea harengus) populations within a restricted area reflects their otolith growth at the larval stage

Florian Berg,Åse Husebø,Jane Aanestad Godiksen,Aril Slotte,Arild Folkvord

doi:10.1016/j.fishres.2017.05.009

Florian Berg, Åse Husebø + Show 3 more

Open Access

https://doi.org/10.1016/j.fishres.2017.05.009

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Abstract

Larval growth from three putative populations was estimated by microstructure analysis of otoliths of four year classes of adult herring sampled over a wide spawning season (February-June) in and around an inland brackish water lake (Landvikvannet) in southern Norway during the years 2012–2015. Mean width of daily increments at distances between 20 and 170μm from the otolith core were significantly higher in Landvik herring (peak spawning in May) compared with the two other populations, Coastal Skagerrak spring spawners (peak spawning in March-April) and Norwegian spring spawning herring (peak spawning in February-March). These population differences were observed for all studied year classes and years and highly consistent with expected temperature dependent larval growth based on timing of successive spawning events. The observed patterns imply that timing of spawning was population specific with a tendency of adult herring to spawn at the same time and under the same conditions as they hatched themselves. This was also supported by vertebral counts, which are negatively correlated with temperatures during the embryonic stage. Firstly, Landvik herring which experienced higher ambient temperature during the embryonic stage were characterised by significantly lower counts than herring from the two other populations. Secondly, daily otolith growth also tended to decrease with increasing vertebral counts within the populations. The present study signifies the importance of otolith growth history for population discrimination in herring, even within the same spawning season, and further supports the use of vertebral counts in the continuous discussion on herring population structure, assessment and management.

Highlights

1.1 Theoretical background and definition of a populationThe biological species concept of Mayr (1942) is a centerpiece and fundamental when studying biology, especially ecology
The present thesis contributes to the understanding of the population dynamics and structure of herring in the northeast Atlantic and their implications on the management of the herring stocks assessed in this region
This thesis is the first (1) demonstrating individual habitat transitions of Atlantic herring by the use of acoustic telemetry, (2) showing consistent differences in daily otolith growth in continuous year classes and over several years between herring populations overlapping in spawning season, and (3) rearing hybrids of two herring populations under common garden conditions until maturity

Summary

Introduction

1.1 Theoretical background and definition of a populationThe biological species concept of Mayr (1942) is a centerpiece and fundamental when studying biology, especially ecology. Fish species may be split into populations based on their degree of reproductive isolation from each other in space and/or time, which could be reflected in genetic or phenotypic differences driven by diverging environmental conditions [1–3]. Under such circumstances exploitation on one population should have little effect on the population dynamics of a neighboring population, and it is common to assess and manage such populations separately [4,5]. Differences in adult spawning patterns might be exhibited in the otolith microstructure of their larvae (Fitzhugh et al, 1997)

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