Mormyridae

Moritz, Timo, Dayem, Zuheir Nour El, Abdallah, Mohammed Abakar & Neumann, Dirk, 2019, New and rare records of fishes from the White Nile in the Republic of the Sudan, Cybium 43 (2), pp. 137-151 : 142-143

Mormyridae

Among mormyrids, three rarely recorded species are confirmed for this area: Mormyrus hasselquistii Valenciennes, 1847 ( Fig. 2B ), a widely distributed and common species in West Africa and the Lake Chad basin, has rarely been collected form the Nile. Bailey (1994) already mentioned that the abundance of this species possibly increases towards the Bahr El Ghazal while it is less common elsewhere in the Nile. We have encountered this species twice so far in the catches of non-stationary fishermen deploying large gill nets above Al Jabalayn. After harvesting the fixed nets over several days, fishes are landed and stored on ice at Al Jabalayn and sold to Khartoum or Kosti. Historically, the range of M. hasselquistii in the Main Nile Basin was assumedly larger: Boulenger (1907) refers to four specimens collected by Geoffroy St. Hilaire in the “ Lower Nile ”, which are deposited in Paris. Even though he does not give exact localities, Geoffroy St. Hilaire never ascended the Nile further south than Luxor, suggesting that the Paris specimens likely originate from the Egyptian Nile below Luxor or from the Nile Delta, where it seems to be extirpated today ( Garcia et al., 2010). The exact range of this species inside the Republic of the Sudan remains unclear: it is present in the White Nile and Bahr El Gebel and may exceed into the Nile River below the confluence of the White and Blue Nile in Khartoum, but recent records of M. hasselquistii from this area are unknown.

Similarly, rare are two other endemic Nile mormyrids, Petrocephalus keatingii Boulenger, 1901 ( Fig. 2C ) and

Cyphomyrus petherici (Boulenger, 1898) ( Fig. 2D ). Petrocephalus keatingii is known from the three historic type specimens: two specimens from Fashoda collected in 1901 and one specimen from 1904, collected somewhere in the White Nile below its junction with the Sobat River ( Bailey, 1994). The species might be more frequent towards the Sobat and Baro rivers and Golubtsov and Mina (2003) confirm this species to be “found in Ethiopia ” (p. 301), but without giving any further details.

The species Cyphomyrus petherici , until recently placed in the genus Pollimyrus ( Levin & Golubtsov, 2017) , was known only from historic specimens originating from Khartoum (4 ex.), the White Nile at Fashoda (2 ex.) and the Blue Nile at Wad Medani (5 ex.) ( Boulenger, 1907). Bailey (1994) apparently refers to Boulenger’s specimens, when he mentions that this species occurs in the White Nile, Blue Nile and Nile at Khartoum, as he does not account on this exceptional species when publishing the results of the ecological studies in the Sudd and Bahr El Gebel area ( Hickley and Bailey, 1986, 1987a, b).

In the Ethiopian lowland, the species seems to be more frequent. Levin and Golubtsov (2017) reported on a total of 23 specimens, 19 of them from the Sobat sub-basin in southwestern Ethiopia, two from the Omo River and an additional two from the slopes of the Blue Nile ascending the Ethiopian highland near the border of the Republic of the Sudan. Records of C. petherici from the Malagarasi system ( De Vos et al., 2001) should be carefully evaluated to confirm the presence of this species outside the Nile basin. Worth mentioning is also one specimen of Brevimyrus niger (Günther 1866) ( Fig. 2A ), with 137 mm SL (160 mm TL) presumably one of the largest known specimens of this species so far, which was included in the catches of Al Jabalayn fishermen.

Figures

Figure 2. – Selected fishes recorded from the White Nile. A-F and I-J from Al Jabalayn. A: Brevimyrus niger, male, 137 mm SL; B: Mormyrus hasselquistii, 282 mm SL; C: Petrocephalus keatingii, male, 145 mm SL; D: Pollimyrus petherici, 200 mm SL; E: Neolebias unifasciatus, female, 22mm SL; F: N. unifasciatus, male, 20 mm SL; G: N. unifasciatus, 18.2 mm SL, BMNH 1948.1.14.6-8; H: N. trewavasae, 19.7 mm SL, BMNH 1948.1.14.11; I. Paradistichodus dimidiatus, 42 mm SL; J: Enteromius macrops, 39 mm SL. (Photos G & H by The Trustees of the Natural History Museum, London).