Largemouth yellowfish

Abstract: Eighty largemouth yellowfish, Labeobarbus kimberleyensis, were collected between April 2005 and February 2006 with gill nets close to the island (26‹ 52, 249Œ S, 28‹ 10, 249Œ E) in the Vaal Dam. The fish were killed, weighed and their length determined. Muscle, liver and spinal cord tissues were collected from each fish and the intestines removed and opened to expose Bothriocephalus acheilognathi. The tapeworms were collected in glass bottles and frozen. Water and sediment, as well as liver, muscle and tapeworm samples were digested and thereafter metal concentrations of 23 elements (lithium, beryllium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, arsenic, selenium, molybdenum, cadmium, tin, antimony, tellurium, barium, mercury, thallium, lead and uranium) were determined with an ICP-MS. Bioconcentration of metals (selenium, mercury, and lead during autumn; copper, zinc, selenium, cadmium, antimony, thallium and mercury during winter; lithium, zinc, selenium, cadmium and antimony during spring; and zinc during summer) occurred in tapeworms. The highest mean value was recorded in sediment, followed by water, tapeworms and host tissue. A seasonal trend showed that a higher concentration of the metals had accumulated in tapeworms during winter when water levels were at their lowest.

Abstract: The aim of this study was to use specimens of the largemouth yellowfish Labeobarbus kimberleyensis, southern Africa's largest cyprinid [IUCN red-listed as Near Threatened (NT)], obtained from gillnet by-catch to describe aspects of its biology in order to assist future conservation and management decisions. Ninety three L. kimberleyensis were collected between March 2007 and May 2008 from Lake Gariep, South Africa. Labeobarbus kimberleyensis was present in 38% of all gillnet catches, but in low numbers (2% of the catch) and it contributed 8% to the catch by mass. Age was estimated using astericus otoliths. Growth increment formation on these otoliths was validated as annual using edge analysis and the mark-recapture of chemically tagged captive fish. Resultant analysis showed that the species is slow growing and the oldest aged fish was a 17 year, 690 mm fork length (L(F)) male. The smallest ripe female fish measured 394 mm L(F) and was 7+ years old and the smallest mature male was 337 mm L(F) and 5+ years old. Slow growth and late maturity make this species vulnerable to exploitation emphasizing the need for continued high conservation priority.

Abstract: Infection of fish by the Asian tapeworm can damage intestines and cause abnormal growth. Eighty largemouth yellowfish Labeobarbus kimberleyensis were collected in the Vaal Dam (26°52.249′S, 28°10.249′E) with the aid of gill nets during a study between April 2005 and February 2006. The fish were killed and the weight and length determined. Thereafter the intestines were removed, the length determined and the intestines opened to expose the tapeworms. The distance between the beginning of the intestine and the attachment position of the first tapeworm was measured, and thereafter all the worms were collected. The prevalence, abundance and mean intensity was calculated for all the surveys. Seasonality and intensity of tapeworms were compared to the intestine and total lengths of the fish. All the tapeworms were identified as the Asian Tapeworm Bothriocephalus acheilognathi Yamaguti, 1934. The position of the first tapeworm was located between 10% and 20% from the anterior end of the intestine in close proximity to the bile opening. A total of 100% prevalence was recorded for all the surveys and the highest mean intensity of 231.1 was recorded during the autumn survey. The lowest mean intensity of 73.7 was recorded during the summer survey. Although the infection rates were very high, the fish condition was good and apparently the fecundity of the fish was not negatively affected as young fish fry was collected during the summer survey. Parasite numbers are higher and differ from a study conducted in 2000 and this is attributed to water temperature and water quality. No correlation was observed between parasite intensity and total length of each fish. This indicates that intensity is not dependant on host size and that infection is not the result of a buildt of over years.

Abstract: SUMMARY Fish population changes in the Hendrik Verwoerd Dam are presented as sampled with a series of multifilament gill nets from Spring 1971 to Summer 1977. During this period, species such as Barbus halubi (smallmouth yellowfish), B. kimberleyensis (largemouth yellowfish), Labeo capensis (Orange River labeo), Cyprinus carpio (common carp) and Clarias gariepinus (sharptooth catfish) appeared to favour the newly created dam-environment. L. umbratus (moggel), however, showed a slight decline in abundance, while the Orange River rock catfish, Gephyroglanis sclateri, disappeared entirely from the gill net catches four years after inundation. Low numbers of Labeo umbratus x L. capensis hybrids were sampled, mainly in areas where small streams enter the dam. Rainbow trout (Salmo gairdnerii) and brown trout (S. trutta) were netted annually during the early summer months. Fluctuations in water level and siltation are probably the main factors causing continual changes in food supply and juvenile production and,...