Aspects Of Shrimp Fisheries On Sudanese Red Sea Coast

Abstract

The thesis has two main general objectives : to highlight the overall marine shrimp fishery characteristics in the coastal lagoons and coastal deep water trawling grounds, and to focus on the fishery of the Green Tiger Prawn, Penaeous semisulcatuus in the Red Sea of Sudan. Two main shrimp fishing methods were employed in this research program. These comprised the use of cast nets and the Otter traw ling nets. The fishery statistical data and shrimp biological data were collected during the period 1999 - 2002. Penaeous monodon and P. indicus constitute the coastal lagoon shrimp fishery. Their catch composition is 67% and 33% respectively. Penaeous monodon predominated in Entabib while P. indicus was highly distributed in Ashat. In the coastal deep wa ter trawling grounds, four species are reported. These are Penaeous semisulcatus , Metapenaeous monoceros , Penaeous latisulcatus and Penaeous japonicus . The catch composition of the P. semisulcatus was 67.8%, that of M. monoceros was 26.9% while the composition of the other two species collectively was only 5.3% in the summer months. Shrimps were more catchable during the night (80%) while the catch was very low during the daytime (20%). The overall shrimp distribution whether in the summer or in the winter months had similar trends along the coast-deep water axis . But the catch rate was always decreasing towards the deep waters with a comparatively higher level in the winter months. In the North-South axis, the overall shrimps distribution showed increasing trend from the north towards the south in both seasons. But the catch rate in the winter was about four folds of that reported in the summer season. The richest fishing grounds are located at Fishing areas 3E and 4E along the Sudanese Red sea coast, where the catch rate averaged 13.1 kg/ hour. The Green Tiger Prawn was only found in the coastal deep waters and not in the shallow coastal lagoons. Its catch composition in the commercial production was about 71% by weight and 64% by numbers. A very strong negative relationship between the catch rate of this animal and the length of the trawling fishing dur ation was found. The best trawling fishing duration for this animal was tw o hours. The best time of fishing the Green Tiger Prawn was from 8.00 pm to 4.00 am. This might have suggested that this animal was nocturnal in its distribution. The distribution of P. semisulcatus had the same trends of distribution as the overall shrimps did in the two axes. The morphometric relationships are established of the Green Tiger Prawn were established. This animal is detritus and most probably feeds on silt, mud, organic matter. Female s had a high sex ra tio in May and December. Smaller female s had a low ratio (20%) and the bigger ones had a higher ratio (80%). Fec undity data occur in October show a maximum number of 9660 and an average of 4778 eggs.