Abstract
The present study aims to investigate the age and growth parameters as well as food and feeding habits of Bagrus bayad (Forskal, 1775) and Bagrus docmac (Forskal, 1775), belonging to the family Bagridae in the Muess Channel of Sharkia Province, Egypt. The relationship between total fish length and vertebra radius is described by straight line equations: L=6.714 + 13.88V and L=8.841 + 10.7 V for both studied species, respectively. The equations of the length-weight relationship for both studied species are expressed as: W=0.0057 X L3.1 for Bagrus bayad W=0.0068 X L3.05 for Bagrus docmac The vertebrae were used to estimate the growth parameters of von Bertalanffy,s equation. It is found that the L∞=87 cm, K=0.159 1/y and to=-1.25 years for B. bayad and L∞=89 cm, K=0.169 1/y and to=-1.275 years for B. docmac. Food and feeding habits of the two cat fish species were also studied through analysis of their stomach contents. B. docmac feeds mainly on invertebrates represented in shrimps, amphipoda, bivalvia and cephallopoda, while the most important food items of B.bayad are fish especially from Telapins and Clarias spp., together with parts of unidentified fishes.
Highlights
In Nile and its tributaries, the genus Bagrus of family Bagridae has two species, Bagrus bayad, and Bagrus docmac forming arealistic proportion of the commercial catches in Egyptian fresh waters [1]
A total of 497 specimens of Bagrus bayad and 332 specimens of Bagrus docmac in the present study were collected from October 2011 to September 2012 by fisher mens along Muess Channel, one of the Nile tributaries, of Sharkia Province, Egypt
It was found that, the relationship between the total fish lengths and the vertebral radii of both fish species which are illustrated in Figures 1 and 2 are represented by the strait line equations: For B. bayad is: L=6.714 +13.88 V r=0.9908 and For B. docmac is: L=8.841 + 10.7 V r=0.9321 The time of the annulus formation Means the time at which a complete annulus is formed at the margin of the vertebrae, this time is determined by using the marginal increment analysis or marginal growth which means the ratio between the distance from the last annulus to the margin and the total radius of the vertebrae
Summary
In Nile and its tributaries, the genus Bagrus of family Bagridae has two species, Bagrus bayad, and Bagrus docmac forming arealistic proportion of the commercial catches in Egyptian fresh waters [1]. The Bagrid fishes are commonly known as naked catfishes. They have four pair’s of barbells enriched with well-developed taste bud [2]. Bagrus docmac is probably associated with rocky bottoms; coarse substrates [4] in both shallow and deep water [5]. Bailey [7] Alhassan and Ansu-Darko [8] declared that Bagrus bayad is a benthic omnivorous feeder (bottom feeder) as they proved the presence of detritus (bottom deposit) in addition to the other food items inside the alimentary tract
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