https://commons.ru.ac.za/vital/access/manager/Index en-us 5 https://commons.ru.ac.za/vital/access/manager/Repository/vital:4612 Wed 12 May 2021 23:46:16 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:4253 Wed 12 May 2021 22:44:52 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:5830 Wed 12 May 2021 20:57:23 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:3804 Wed 12 May 2021 20:49:22 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:5783 Wed 12 May 2021 20:24:25 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:4578 Wed 12 May 2021 20:19:45 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:3788 Wed 12 May 2021 20:13:45 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:5617 Wed 12 May 2021 19:58:51 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:5682 Wed 12 May 2021 19:55:48 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:5803 Wed 12 May 2021 19:48:40 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:941 Wed 12 May 2021 19:27:00 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:4645 Wed 12 May 2021 19:05:21 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:4916 Wed 12 May 2021 17:42:33 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:5047 Wed 12 May 2021 17:19:18 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:4106 Wed 12 May 2021 16:37:22 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:5775 Wed 12 May 2021 16:18:56 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:5234 0.05) between slopes of the control and 0.11 ± 0.02 mg/l Cu, and between 0.29 ± 0.02 and 47 ± 0.04 mg/l Cu before and after introducing food in the tanks. The slopes of both the control and 0.11 ± 0.02 mg/l Cu were significantly different from those of 0.29 ± 0.02 and 0.47 ± 0.04 mg/l Cu (p < 0.05). There were significant differences in the mean opercular movements per minute between treatments (p < 0.05). There was hyperventilation at 0.11 ± 0.02 mg/l Cu i.e. 87 ± 18 opercular movements per minute (mean ± standard deviation) and hypoventilation at 0.29 ± 0.02 and 0.47 ± 0.04 mg/l Cu i.e. 37 ± 34 and 13 ± 6 opercular movements per minute compared to the control. Hypo- and hyperventilation were related to the lesser and greater gill damage, respectively. In conclusion Cu accumulation and effects on histology of the liver, gills and were related to the concentration of Cu in the water and duration of exposure showing a gradual increase in incidence and intensity with larger duration of exposure time and increasing Cu concentration. The fish were initially able to homeostatically regulate and detoxify Cu. However, as the exposure continued, the homeostatic mechanism appears to have failed to cope with the increasing metal burden causing advanced histological changes.]]> Wed 12 May 2021 15:54:00 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:5384 Thu 13 May 2021 15:44:25 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:3766 Thu 13 May 2021 15:43:37 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:1141 Thu 13 May 2021 13:30:21 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:4140 Thu 13 May 2021 09:31:13 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:5201 Thu 13 May 2021 07:12:53 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:5131 Thu 13 May 2021 07:07:07 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:3957 Thu 13 May 2021 07:02:42 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:4303 Thu 13 May 2021 06:34:49 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:4214 Thu 13 May 2021 06:22:34 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:5484 Thu 13 May 2021 05:52:34 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:4681 Thu 13 May 2021 05:45:23 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:5312 85% in confiscations and research collections, and did not change significantly over the period of examination. Comparison of illegal catches with an adjacent site indicated that the emergent abalone population at Cape Recife had a significantly higher proportion of undersized emergent animals (p<0.001) and they were significantly smaller than the abalone from the closest site, Noordhoek, and other areas in Port Elizabeth from 2000–2002 (p<0.001). The apparent declines in emergent abalone abundance indicated by the poaching data were corroborated by sampling of emergent abalone abundance at Cape Recife. Numbers of abalone declined significantly from 125.6 to 53.8 per 20min count (p<0.001), from April 1998–October 2001 and density declined from 1.3 to 0.8m⁻² over a similar period (p<0.001). Juvenile density did not change over this period, although there were significant differences in density observed between two different habitats (p<0.001). Initial releases of cultured juvenile abalone showed that they could be distinguished from their wild counterparts for at least a year after release, by their different shell colouration. Short-term, small-scale trials (7–10 days) using animals between 17 and 30mm SL had mean survival rates of 64–82% (mean 70.4%) and the effect of size on survival was not significant in most cases, although the power to detect differences was low. Attempts to measure the effect of habitat on survival were not conclusive, although refuges under sea urchins appeared to be favoured by both seed and wild abalone, although urchins were not an absolute requirement for survival. Similar medium-term trials (31–74 days) in sheltered sites yielded mean returns of 53.1% using 25mm SL animals and similar trials in a more exposed area had more variable survival rates of between 18.4 and 73.6%, after 25–27 days. A comparison between careful hand-seeding and surface-scattering seed release methods in the open-ocean habitat showed no significant differences in survival rate after 41 days. Larger seed survived significantly better than the smaller seed when scattered on the surface (p<0.0001) and the smaller seed survived significantly better when seeded carefully by hand onto the substrate (p<0.028). Further medium-term releases of large numbers of seed abalone, released using the surface-scattering method in open-ocean habitat, gave mean survival rates of 32.8% over periods of 83–114 days. Assessment of a seeding trial using release modules to seed juvenile animals in the open-ocean was hampered by poor sea conditions and difficult to search substrates, and a mean recovery rate of 3.1% was obtained for the sites that were sampled. Movement of seed was low in the more sheltered sites, and also appeared to be affected by the amount of available habitat. Growth of seed was measured using changes in shell colouration and there were significant differences between areas. An average growth of 1.6mm.month⁻¹ shell length was calculated for all areas. The potential for commercial scale abalone ranching to be used to enhance a territorial user right fishery was investigated using a model of economic feasibility. Internal rates of return of 30.3 and 36.9% were obtained from two harvest regimes using different harvest sizes. There was a high degree of risk associated with these figures owing to a lack of consistent seed survival rate estimates, and the input parameters, which are subject to variation, showed a significant effect on profitability. The operation of this type of ranching scheme is probably not economically feasible as a stand-alone operation but could probably be operated effectively in conjunction with an existing abalone farm. By adding a small wild catch component the profitability of a ranching scheme could be significantly improved. The results of the present study indicate that high levels of poaching at Cape Recife have led to declines in emergent abalone abundance, which will probably lead to stock collapse in the near future. This implies that fisheries managers have failed to fulfil the provisions of fisheries policy in South Africa. The present results from seeding trials show that cultured juveniles can survive and make a contribution to overall stock abundance. Furthermore, while there are obstacles to economic feasibility, commercial ranching has the potential to be a valuable addition to current abalone management strategy.]]> Thu 13 May 2021 03:57:52 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:4374 Thu 13 May 2021 03:57:29 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:4003 Thu 13 May 2021 03:38:55 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:4088 Thu 13 May 2021 03:34:04 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:5731 Thu 13 May 2021 02:58:05 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:5291 0.05). Protein (p<0.0001) and energy (p<0.0.1) levels of suspended solids were significantly greater in raceways dedicated to feeding Abfeed. The infestation level (number of tubes/centimetre on the grwoing edge) was significantly higher (p<0.001) in Abfeed-fed abalone. The morphometrics of the sabellids indicated that sabellids from Abfeed-fed abalone were larger in various body measurements: length (p<0.00001); neck width (p<0.001); base width (p<0.001); and surface area (p<0.001). This study suggests that abalone diet has an important influence on the infestation level and size of sabellids and that this is likely to be due to the fragmentation and leaching of nutrients from the artificially enriched commercial abalone diet.]]> Thu 13 May 2021 02:34:35 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:4254 Thu 13 May 2021 01:19:44 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:3961 Thu 13 May 2021 01:02:05 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:3753 Thu 13 May 2021 00:58:14 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:5508 Thu 13 May 2021 00:04:31 SAST ]]>