Organochlorines in common dolphins caught in shark nets during the Natal ‘sardine run’

The concentrations of organochlorines were determined in blubber and liver samples from common dolphins inhabiting the coastal waters of the south-east coast of southern Africa. Liver levels of PCBs and DDTs are far lower and do not appear directly associated with those in blubber. In males, blubber residue concentrations increased with age but in females a marked rapid decline in concentrations of PCBs and t-DDT was evident between the eighth and eleventh growth layer groups, approximately the age of sexual maturity and subsequent to their first or second ovulation. Lower levels in females are explained through transfer to the new-born calf during lactation and the consequences of this for the newborn calf are discussed

Shark predation on Indian Ocean bottlenose dolphins Tursiops truncatus off Natal, South Africa

The incidence of shark induced scars on Indian Ocean bottlenose dolphins caught in gill nets off Natal, on the south-east coast of southern Africa, was monitored between January 1983 and June 1987. The occurrence of dolphin remains in sharks caught in these nets between January 1980 and December 1985 was also recorded. Of the dolphins caught, 10,3% exhibited scars or wounds consistent with shark bites. Only 1,2% of over 6000 sharks caught contained cetacean remains. Four species of shark, the Zambesi (Carcharhinus leucas), the tiger (Galeocerdo cuvieri),the great white (Carcharodon carcharías) and the dusky shark (Carcharhinus obscurvs) were implicated as dolphin predators. Estimates from the number of these four species caught annually and the frequency of occurrence of dolphin flukes and vertebrae in their stomachs suggest that a mininum of 20 bottlenose dolphins or 2,2% of the estimated population in southern Natal coastal waters are killed each year by sharks

Potential of using host plant resistance, nitrogen and phosphorus fertilizers for reduction of Aspergillus flavus colonization and aflatoxin accumulation in maize in Tanzania

Aflatoxin contamination (AC) in maize, caused by the fungal pathogen Aspergillus flavus(Link), starts at pre-harvest stage. Hence, interventions that reduce entry and development of A. flavus in the field are required. Trials were carried out at Seatondale and Igeri, to evaluate the effects of nitrogen and phosphorus fertilizer combinations, hereafter referred to as fertilizers, on A. flavus and AC in maize kernels. The main treatments were four combinations of N and P fertilizers (60 or 120 kg Nha−1 with 15 or 30 kg Pha−1) and sub-treatments were of six popular maize hybrids. Plants at 50% silking were inoculated with the fungus through the silk channels. Grains from inoculated and control ears were analysed for AC using Enzyme Linked Immunosorbent Assay, and pathogen content quantified by Quantitative Polymerase Chain reaction. Higher AC (mean 6.51 μg kg−1) occurred at Seatondale than Igeri (mean 0.45 μg kg−1), probably due to low temperatures (8–23 °C) at Igeri. Fertilizers didn't cause significant differences in neither pathogen colonization nor AC at both sites. However, mean A. flavusaccumulation, as measured by pathogen host DNA ratio, was thrice (0.16) as high in sub-optimal fertilizer conditions compared to optimal fertilizer rate (0.05). All hybrids were susceptible to A. flavus and AC, though a difference in AC was noted among the hybrids at both sites. PAN 691 showed the highest AC (14.68 μg kg−1), whereas UHS 5210 had the lowest AC (1.87 μg kg−1). The susceptibility varied among the hybrids and was mostly associated with ear droopiness, husk tightness, days to 50% silking, 50% pollen shed, Anthesis to silking interval, diseased ears, insect damaged ears, kernel texture, dry matter, grain filling, ear height, kernel ash content and kernel moisture content. At Seatondale, A. flavus accumulation was positively correlated with aflatoxin (r = 0.606), and both A. flavus accumulation and AC were positively correlated with diseased ears. Selection and growing of less susceptible varieties under optimal fertilizer regime offer ideal strategy for sustainable reduction of A. flavus and aflatoxin contamination in maize at pre-harvest