A survey of the shrimp resources of Nigeria

Previous planned resources surveys of the Nigerian coastal waters were performed with research vessels, gear and personnel not specialised for shrimp fishing. The results have, therefore, only indicated relative abundance of shrimps in the areas fished, rather than showing the absolute catches which a commercial fishing vessel in the area may expect to make. The present survey used two commercial shrimp trawlers together with their crews, who already had long experience of shrimp trawling both in the Nigerian shrimp grounds and elsewhere. Four shrimp species were caught: Penaeus duorarum, P. kerathurus, Parapeneopsis atlantica and Parapenaeus longirostris. Of these, P. duorarum, P. atlantica and P. longirostris are of commercial importance, P. duorarum being the most important. The distributions and concentrations of these 3 species are shown, together with the size distribution of P. duorarum, and the fish by-catch at each station. With the exception of the transect off the Nun Entrance, all transects sampled showed areas of high concentrations of P. duorarum, that is, 54 to 113 lbs (24 to 51 kg) of head-on shrimps per hour of trawling. The oceanographic conditions prevailing at the time of the survey were normal for the area. Records of previous shrimp landings from the area show a regular seasonal variation and the period of the survey to be one of lowest catches. The catch rates obtained in this survey are, therefore, the minimum which might be expected for the year. From a consideration of the operating costs of the type of shrimp trawler considered adequate for use in the area, it is found that the break-even shrimp catch is about 41 lbs (19 kg) of head-on per hour.