The menhadens Brevoortia gunteri and B. patronus are sympatric and morphologically similar. The two species are planktophagous and exhibited significant (P<0·0001) food resource partitioning, with phytoplankton predominating in B. patronus stomachs and zooplankton in B. gunteri. The branchial apparatus of both species is of the typical alosine form. Brevoortia patronus has significantly more branchiospinules per mm (x =19·47) and significantly longer gill rakers (x =13·35 mm) than B. gunteri (x =14·11, x =12·01 mm respectively). B. patronus is characterized by a gill raker system forming a fine-meshed filter capable of retaining smaller food items. The results support the hypothesis that food resource partitioning is related to different morphological features of the branchial apparatus. 1996 The Fisheries Society of the British Isles