Spawning migration of Labeobarbus species to some tributary rivers of Lake Tana, Ethiopia

Abstract

ABSTRACT Spawning migration of Labeobarbus species was studied from August to December 2013 in some tributary rivers (Qimon, Guanta, Shini, and Chibirna) of Lake Tana. Fish specimens and physico-chemical parameters were measured bimonthly in August and September but monthly from October to December. Adult fish specimens were caught using 6 and 8 cm stretched mesh size monofilament gillnets and 6, 8, 10 and 12 cm mesh size multifilament gillnets. A total of 933 adult Labeobarbus specimens were collected during the study period. Labeobarbus intermedius was the most abundant species followed by L. brevicephalus. The peak spawning season of L. intermedius was from fourth week of August to end of September and for L. brevicephalus it was from fourth week of August to beginning of October. Both species were found to spawn in all sampling rivers. However L. truttiformis spawned only at Guanta and Qimon Rivers during August while L. nedgia in Shini and Chibirna Rivers at the end of September. This implies the presence of micro-spatial segregation among species. Pair-wise comparison of Labeobarbus species showed temporal segregation in all sampling months, except L. brevicephalus and L. nedgia. The present findings showed that small tributary rivers and streams are the main spawning grounds for Labeobarbus species of Lake Tana. Therefore, main spawning grounds or routes should be protected from the deleterious effects of anthropogenic activities like illegal fishing, irrigation and sand mining for wise use of the fish resources.