Diel differences in catches of Western Baltic Spring Spawning Herring Larvae (Clupea harengus)

Rehberg, Sabine and Stepputtis, Daniel and Hammer, Cornelius and Zimmermann, Christopher (2009) Diel differences in catches of Western Baltic Spring Spawning Herring Larvae (Clupea harengus). Informationen aus der Fischereiforschung = Information on Fishery Research, 56(1), pp. 23-34. 10.3220/Infn56_23-34_2009

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Abstract

Comparative night and day catches of herring larvae were taken during the Rügen-Herring-Larval-Survey (RHLS) in 2007 and 2008 in the Greifswalder Bodden which is the main spawning area of the Western Baltic Spring Spawning Herring. The quantities and the size composition of larvae caught during night and day were examined. During night more larvae were caught compared to the samples taken at daytime, especially with larvae larger than 25 mm. This indicates avoidance reactions, which increase with the developmental stage of the larvae. The differences of the night and day catches are relatively constant until a length of about 25 mm, thus the night/day effect does not influence estimations concerning larvae smaller than 25 mm (e.g. N20 index). There might be an impact on estimations for larger larvae due to the night/day effect. For further research other aspects like cloud coverage at night, phase of the moon, underwater visibility and turbidity should be taken into account. These aspects might influence the avoidance reactions.

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