Obligate feeding of cichlid eggs byCaecomastacembelus zebratusin Lake Tanganyika

Abstract

This study examined food habits of four common species of spiny eels (Mastacembelidae) in Lake Tanganyika to find if they eat cichlid eggs and larvae. Diets ofCaecomastacembelus zebratusconsisted nearly exclusively of eggs of substratum‐brooding cichlids, whereas two other species fed on eggs only facultatively and one species never did. More than half individuals ofC. zebratushad empty guts, although the mean weight of their gut contents was highest. This spiny eel ate many eggs in the first and second quarters of the lunar cycle when the spawning of substratum‐brooding cichlids was active, while it nearly ceased eating in the latter half of the cycle. It is suggested that this fish is an obligate egg‐eater and one of the predators that cause the high mortality of early cichlid broods.