Individual fish rhythm directs group feeding: a case study with sea bass juveniles (Dicentrarchus labrax) under self-demand feeding conditions

Type Article
Date 2009-07
Language English
Author(s) Millot Sandie1, Begout Marie-LaureORCID1
Affiliation(s) 1 : IFREMER, LRHLR, F-17137 Lhoumeau, France.
Source Aquatic Living Resources (0990-7440) (EDP Sciences), 2009-07 , Vol. 22 , N. 3 , P. 363-370
DOI 10.1051/alr/2009048
WOS© Times Cited 23
Keyword(s) Dicentrarchus labrax, Self feeder, Social interactions, Feed demand leader, Feeding rhythms
Abstract The long term influence of individual biological rhythms on group feed demand behaviour was investigated in European sea bass (Dicentrarchus labrax) held under controlled environmental conditions with an on-demand feeding system. The experiment was realized over 219 days with 190 fish distributed on 4 tanks. Sea bass had a mean body mass comprised between 139 g to 183 g. The number of feed demand acts by each individual was calculated daily, and the population could thus be partitioned into three categories (high-, low-and zero-triggering fish). The duration of the period that an individual held high-triggering status could vary, but was 63 +/- 16 days on average. The transition period between two highest-triggering fish in one tank was on average 4 +/- 4 days. The group feeding rhythm followed the same pattern of feed demand rhythm as the highest-triggering individual fish. When the highest-triggering fish was nocturnal, the totality of feed demand in the group was realized during the night with one peak at 22:00, corresponding to dusk under experimental conditions. When the highest-triggering fish was diurnal, the majority of feed demand in the group was realized during the light period with one peak at 06:00, corresponding to dawn, and/or another at 12:00. This study therefore highlights that sea bass group feeding behaviour is not the sum of individual feed demand behaviours, but is directed by the rhythm and behaviour of a few high-triggering fish. The regular changes of high-triggering fish in the group proved that it was not the identity of these particular fish that was most important for the group, but their role as a feed demand leader.
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