Diouf Khady, Panfili Jacques, Labonne Maylis, Aliaume C., Tomas J., Chi T. D. (2006). Effects of salinity on strontium : calcium ratios in the otoliths of the West African black-chinned tilapia Sarotherodon melanotheron in a hypersaline estuary. Environmental Biology of Fishes, 77 (1), p. 9-20. ISSN 0378-1909.
Titre du document
Effects of salinity on strontium : calcium ratios in the otoliths of the West African black-chinned tilapia Sarotherodon melanotheron in a hypersaline estuary
Diouf Khady, Panfili Jacques, Labonne Maylis, Aliaume C., Tomas J., Chi T. D.
Source
Environmental Biology of Fishes, 2006,
77 (1), p. 9-20 ISSN 0378-1909
The biology and the behaviour of fish populations in hypersaline environments are poorly known. The habitat occupation strategy of the tilapia Sarotherodon melanotheron has been studied along a salinity gradient in the Saloum hypersaline estuary in Senegal ( salinity between 32 and 100). The individual migratory behaviour has been analysed from otolith strontium-to-calcium concentration ratios from fish sampled in five locations during the 2003 wet season and the 2004 dry season. In the upper part of the estuary ( salinities > 50), the Sr: Ca ratio in the otolith showed high variations, from 2.51 to 33.30 x 10(-3). These maximum observed values have never been reported in the literature. The individual mean of Sr: Ca ratios increased according to the salinity gradient in the estuary, with significantly higher values in the upper part ( Sr: Ca mean = 16 x 10(-3)) than in the lower part ( salinity < 50, Sr: Ca mean = 12 x 10(-3)). No significant difference in the Sr: Ca mean was observed between locations with comparable salinities. Sr concentration in the water at the different locations was positively correlated with ambient salinity. The mean of Sr: Ca in the otoliths was then in relationship with the level of Sr in the water. Thus, the Sr: Ca ratios in the otolith of S. melanotheron allowed to discriminate the populations of this species and to hypothesize that they did not undertake large scale movements within the estuary.
