Spawning energetics and otolith microchemistry provide insights into the stock structure of bonga shad Ethmalosa fimbriata

Abstract

The gross energy content of spawning batches and the microchemistry of sagittal otoliths in individual female bonga shad Ethmalosa fimbriata were compared between contrasting sampling sites at the Senegalese southern coast and inside the hypersaline Sine Saloum Estuary. Results show that females spawning in the estuary's middle reaches invested almost three times more energy into reproduction (115 ± 65 J g−1 body mass) than their neritic counterparts (39 ± 34 J g−1 body mass). Also, female otolith levels of Ba:Ca, Sr:Ca and Zn:Ca either differed significantly between study sites or could be linked to heterogeneous environmental variables. A quadratic discriminant function analysis provided evidence of segregated spawning populations of E. fimbriata in southern Senegalese waters.