A study was carried out in four vifiages of Makenene Sub-Division some 85 km north-west of Yaounde, between November 1993 and March 1994 to assess the prevalence and intensity of schistosomes and other helminth infections among senior primary school pupils aged 9–16. An extensive questionnaire was used to collect sociodemographic information and information on water-related activities.The overall prevalence of S. mansoni infection was 228 (23.6%) while S. haematobium infection was practically non-existent 03 (<1%). Infection rates with intestinal nematodes were very high, up to 98% in some villages. Prevalence rates of schistosomiasis varied significantly (P<0.05) between vifiages with the highest (36.2%) recorded in Makenene. Infections with other parasite species encountered were significantly different (P<0.01) while a marked association was observed between water contact activities and the distribution of S. mansoni infections. However, S. mansoni infection intensities were not significantly different (P>0.05) between those with a history of previous infection and treatment and those without.

The acute toxicity of alkylbenzene sulphonate (ABS) detergent to the toothed carp. Aphyosemion gairdneri (L.). was investigated using static bioassays and continuous aeration over a period of 96 h. The 96-h LC,^, opercular ventilation rates per minute and behaviourial responses were evaluated. The 96-h LC was determined to be 25.11 ± 8.4 mg 1"'. The toxicant led to an initial increase in the opercular ventilation, which then decreased below the initial values by the 96th hour of exposure. Prior to death, erratic swimming, lost of balance and respiratory distress were observed. Skin lesions and haemorrhaging of the gill filaments were observed on dead fish. brook charr Salvelinus fontinalis (Mitchill), Arctic charr, Salvelinus alpinus (L.), and their hybrids S DumasGroupe de recherche en recydage biologique et aquaculture (GREREBA), Universite Laval, Quebec Canada Abstract Net body and yolk weights at hatching, growth rates during yolk absorption, yolk ahsorption rates, yolk conversion efficiencies, and subsequent growth during rearing were studied in brook charr, Salvelinus fontinalis (Mitchill) (FF), Arctic charr, (Salvelinus alpinus (L.) (AA) and hybrids between these species (FA, AF: first letter indicates the species of the female). Both the maternal and paternal species affected the net body weight at hatching while yolk weight was determined by the nnaternal species: progeny from female brook charr had more yolk than those from female Arctic charr. Growth rates during yolk absorption were similar in FF, AF and AA, and were faster than those observed in FA. Yolk absorption rates were determined by the paternal species: progeny from brook charr males used their yolk more rapidly than those from Arctic charr. Following the onset of feeding, weight of the hybrid FA, which was smaller at hatching, became not significantly different from that of the other hybrid. As development progressed, hybrid weights during rearing were intermediate to those of the parental species, with brook charr juveniles being heavier than Arctic charr.

Summary :Two regions of the Jos Metropolis in Plateau State, Nigeria, with contrasting topographic features and harbouring many snails infes

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