Changes in experimental gillnet catches from the Kafue Floodplain, Zambia, since construction of the Kafue Gorge Dam

The Kafue Floodplain fishery produces an annual fish yield of about 5000 tonnes. The 1971 closure of the Kafue Gorge Dam downstream from the floodplain modified flooding patterns. Pre-impoundment studies predicted this modification would increase fish stocks. Experimental gillnets set in 1975 and 1976 caught 18 species on a regular basis, nine of which were abundant enough for comparison with catches in similar gillnet samples taken prior to completion of the Kafue Gorge Dam. Of these nine species, experimental gillnet catches of three predator species were smaller in 1975–76 than in 1969–70. Catches of only one species increased significantly. Whether this change is due to the modified flooding pattern is unclear; unusually dry flood conditions in 1973 and increased fishing effort may have contributed.     

Serosurvey of Brucella spp. infection in the Kafue lechwe (Kobus leche kafuensis) of the Kafue flats in Zambia

One of the diseases of veterinary and public health importance affecting the Kafue lechwe (Kobus leche kafuensis) on the Kafue flats is brucellosis, for which only scant information is available. During the 2003 (October), 2004 (December), and 2008 (July-December) hunting seasons in the Kafue flats, we conducted a study to determine the seroprevalence of Brucella spp. in the Kafue lechwe and to evaluate serologic tests for detection of Brucella spp. antibodies in lechwe. The Rose Bengal Test (RBT), competitive enzyme-linked immunosorbent assay (cELISA), and fluorescence polarization assay (FPA) were used. A total of 121 Kafue lechwe were hunted for disease investigations in 2003, 2004, and 2008 in the Kafue Flat Game Management Area. Of these, 21.6%, (95% confidence interval [CI]: 14.2-29.1%) had detectable antibodies to Brucella spp. The Kafue lechwe in Lochnivar National Park had higher antibody results than those in Blue Lagoon National Park (odds ratio=3.0; 95% CI: 0.94-9.4). Infection levels were similar in females (21.6%) and males (21.7%). Results were similar among RBT, FPA, cELISA tests, suggesting that these could effectively be used in diagnosing brucellosis in the Kafue lechwe. Our study demonstrates the presence of Brucella infections in the Kafue lechwe in two national parks located in the Kafue flats and further highlights the suitability of serologic assays for testing the Kafue lechwe. Because the Kafue lechwe is the most hunted wildlife species in Zambia, hunters need to be informed of the public health risk of Brucella spp. infection.     

Investigating effects of parasite infection on body condition of the Kafue lechwe (<Emphasis Type="Italic">Kobus leche kafuensis</Emphasis>) in the Kafue basin

Background

The Kafue lechwe (Kobus leche Kafuensis), a medium-sized semi-aquatic antelope, is endemic to the Kafue basin of Zambia. The population of the Kafue lechwe has significantly dropped in the last decades leading to its subsequent inclusion on the red list of endangered species. In order to save the remaining population from extinction, it has become increasingly important that the impact of parasite infection and infestation on the Kafue lechwe is investigated.

Findings

Endoparasites accounted for the majority of parasites observed from a study of 40 Kafue lechwe occurring in the the Kafue basin. Amphistoma spp. were present in all animals examined, while Fasciola gigantica had a prevalence rate of 0.525 (95% CI: 0.36 to 0.69) and species of Schistosoma 0.3 (95% CI: 0.15 to 0.45). Among the ectoparasites, Strobiloestrous vanzyli, had a prevalence rate of 0.15 (95% CI: 0.03 to 0.27), while Rhipicephalus appendiculatus had a prevalence of 0.075 (3/40). Our findings indicate that body condition was not influenced by the parasitic infestation in Kafue lechwe. There was no association between sex and parasitic burden (odds ratio = 0.3, 95% CI: 0.8-1.3). However, an association between age and parasitic burden was observed as older animals above 15 years were more likely to get parasite infections than those aged between 1-5 years (odds ratio = 1.5, 95% CI: 1.1-2.4).

Conclusion

Overall, there was no evidence that parasitic infections and infestations adversely affected the lechwe population on the Kafue basin. These findings indicate that ecto- and endo-parasite infestation might not play a significant role in reducing the Kafue lechwe population on the Kafue basin.

     

Reproduction of Blackchin Tilapia, Sarotherodon melanotheron, Within an Impounded Mangrove Ecosystem in East-central Florida

I investigated the reproductive biology of introduced blackchin tilapia, Sarotherodon melanotheron, over a twelve month period within a seasonally impounded mangrove ecosystem in east-central Florida, and compared the data to published accounts from native African habitats. Eggs and free embryos were collected from the buccal cavity of adult males from April to October indicating a protracted spawning season, however gonadosomatic indices suggested that most spawning occurred in April and May. The timing of reproduction was adjusted to occur immediately before temperatures reached optimal levels for juvenile growth and when increasing rainfall produced abundant food and shelter for the young. Temperatures below 24°C inhibited reproduction from November to March. The overall sex ratio was essentially 1:1. The minimum and maximum size at maturity were much larger in this study than those reported from Africa; the smallest mature male was 128mm standard length and 0.47 of the maximum size, while the smallest mature female was 145mm standard length and 0.54 the maximum size. However, because of the difficulty in aging this species and a lack of published information, it could not be determined whether the population in this study possessed a relatively early or delayed maturation compared to African populations.     

Phylogenetic relationships between 21 species of three tilapiine genera Tilapia, Sarotherodon and Oreochromis using allozyme data

With the aim of detecting speciation events in Tilapia sensu lato , 24 enzyme loci were studied in eleven species of the genus Tilapia , four species fo the genus Sarotherodon , five species fo the genus Oreochromis and five other species belonging to similar genera ( Pelmatochromis, Chilochromis, Tylochromis, Hemichromis and Chromidotilapia ). The phylogenetic trees obtained show a clustering of species (except for Sarotherodon melanotheron ) according to their genera, i.e. Tilapia, Sarotherodon or Orechromis , which confirms the systematics adopted by Trewavas. The phylogenetic trees obtained by rooting with species belonging to similar genera confirm the hypothesis that mouthbrooders ( Sarotherodon and Oreochromis ) have a single origin, i.e. egg layers ( Tilapia ), and negate the hypothesis of multiple speciation of Peters and Berns.     

The ecology of the Kafue lechwe population of Zambia before the operation of hydro-electric dams on the Kafue River

Aerial surveys from 1970 onwards suggest a stable Kafue lechwe population of 94 000±9% on the Kafue Flats. The present distribution shows a contraction in dry and wet season range in comparison with 1953/54. Sex ratios of populations on both the North and South banks of the Kafue river do not differ significantly from unity. North bank males have a higher survival rate than South bank males. Survival curves for males and females on the South bank show the same pattern. For both the 1971 and 1972 breeding seasons 73% of South bank females older than 1½ years are expected to have bred successfully. The peaks of conceptions for both seasons are from mid-December to mid-March, suggesting a main lambing period from mid-July until mid-October. Present sex ratio, age structure, reproductive status and the reproductive cycle have been compared with 1961/62 data. Variation in physical condition, based on monthly measurements of the kidney fat percentage, dressing-out percentage and live weight, although influenced by the physiological demands of rut and pregnancy, is correlated with the availability of flood-plain grazing. The lowest values of condition parameters are found during the period of maximum flood, after the end of the rains (April/May), until the receding flood makes flood-plain grazing available, usually in early June. A high level of tuberculosis, lungworm infection and many other pathogens amongst the South bank population are reported. Animals from the North bank are thought to be in better physical condition. The Kafue Gorge dam, completed in 1971, and the Iteshi-teshi dam, at present under construction, will prolong the high flood period in wet years and prevent most flooding in dry years, both of these effects will reduce the carrying capacity of the flood plain for lechwe and a large reduction of the size of the population is expected to result from the operation of the dams.     

The potential trade‐off between artisanal fisheries production and hydroelectricity generation on the Kafue River,Zambia

1. Freshwater resource managers are increasingly obligated to consider the impacts of large river engineering projects on ecosystem services. We evaluated the effect of altered water regime from the operation of a large dam on the production of the downstream tropical floodplain fishery of the Kafue River, Zambia. We compared the benefits of increased hydropower relative to potentially lost fishery production. 2. We compiled a long‐term data set consisting of experimental gillnet catches, artisanal harvesting effort and monthly river flows for 25 years prior to and 29 years after the 1977 completion of the upstream Itezhi‐Tezhi Dam. As a metric of the flood regime, we calculated a canonical correlation score for each hydrological year before and after dam closure. For the period following dam construction, we used the Muskingum method of flood routing to estimate ‘no‐dam’ flows through the fishery area and downstream hydroelectric turbines at the Kafue Gorge Dam. 3. We compared 16 alternative models of catch per unit effort (CPUE) with and without an effect of water regime on fish population growth rate. Using the two best fitting models, we estimated the total observed fishery harvest and simulated ‘no‐dam’ fisheries harvest and found no significant effect of altered water regime on fishery production. 4. We estimate that the large upstream dam increases downstream hydropower production by about $18 million USD per annum. The reduction in fishery production caused by the altered water regime is not significantly different than zero, although the average reduction amounts to about $2.3 million annually. The total estimated value of harvest ranges from $1.3 million to $56 million annually. 5. Large observed declines in fish abundance over the 54‐year study period are attributed primarily with similarly large increases in total fishing effort in this mostly open‐access artisanal fishery. 6. These results contrast with other examples of the effects of flow alteration on fish, probably because levels of fisheries exploitation on the Kafue River are very high relative to better studied regions on other continents; our focus on the whole fish community; and the unprecedented length of the time series we considered. If the goal is to sustain fishery production, investments in altering flow regime are likely to be less effective than investments to decrease fishing effort.     

Feeding behavior of the cichlid,Sarotherodon galilaeum: selective predation on Lake Kinneret zooplankton

In laboratory feeding trials, we analyzed the feeding behavior and selectivity of the cichlid, Sarotherodon galilaeum, for zooplankton prey from Lake Kinneret, Israel. The feeding behavior was dependent on fish size. Fish less than 20 mm SL fed on zooplankton as obligate particulate feeders. Fish from 20 to 42 mm SL fed either as particulate feeders or as filter feeders. Fish larger than 62 mm SL fed as obligate filter feeders. Particulate-feeding fish were size selective and had highest feeding electivities for large-sized zooplankton species. Filter-feeding fish had highest feeding electivities for zooplankton species with poor escape ability. In general, S. galilaeum predation pressure would be greatest on Ceriodaphnia reticulata, a large-bodied and easily captured species which is selected by both particulate-feeding and filter-feeding fish.     

Census of the Kafue lechwe by aerial stratified sampling

The Kafue lechwe population of the Kafue Flats, Zambia, was counted four times within a 26-month period (April 1970-June 1972) by aerial stratified random sampling. The censuses gave good agreement which did not differ statistically. By combining the data for the three most precise surveys, the estimated population is 93 975 with 95% confidence limits of ± 8563 (or ± 9-1%). A method of sampling was used which is based on calculation of animal densities on a linear basis, instead of on densities per unit area. This method has several advantages and is discussed in relation to the problems involved in aerial census. The past and present status of the Kafue lechwe population is reviewed.     

Validation of daily increment deposition and early development in the otoliths of Sarotherodon melanotheron

A one-to-one relationship was found between days of rearing and counted daily increments in the otoliths of Sarotherodon melanotheron verifying daily increment deposition. A marked hatch check was found in all otoliths from both the reared fish and the wild specimens. Five to 10 faint prolarval increments were visible but the rate of their formation was not investigated. The rate of increment deposition of S. melanotheron is apparently independent of somatic growth and increments found in the otoliths of this species can therefore be used for ageing.     

Reproductive seasonality in Kafue lechwe antelope

Kafue lechwe antelope ( Kobus leche kufuensis ) inhabit a wetland area of the Kafue Flats in southern Zambia and have seasonal peaks in mating and calving. The construction of a hydroelectric scheme has recently altered the time of year when flooding starts, and there has been a corresponding change in peak mating and calving dates. In this study, Kafue lechwe mated mainly during the dry part of the year when grass quality and quantity was at its lowest and when water levels were increasing and thus inundating any potential food. As rising water levels corresponded with increases in numbers of oestrous females on leks (both before and after dam impoundment), and with increased mating rates in two other subspecies of lechwe (the black and red lechwe), floods appear to act as a proximate cue for the initiation of mating. Mating during rises in water levels results in most calving occurring seven months later (the gestation period) when the floodwaters are receding and exposing optimal forage, irrespective of the time of year, and this increases the survival of the lactating mothers and their calves.     

Geese and Red-knobbed Coot on the Kafue Flats in Zambia, 1970–1974

The occurrence, chronology of breeding and wing-moult, and feeding habits of the Pigmy Goose Nettapus auritus, Knob-billed Goose Sarkidiornis melanotos, Spur-winged Goose Plectropterus gambensis, Egyptian Goose Alopochen aegyptiaca and Red-knobbed Coot Fulica cristata on the Kafue Flats in Zambia are described based on observations made between October 1970 and January 1974 at Lochinvar National Park and, from the air, over the central section of the Flats. The Pigmy Goose, Knob-billed Goose, Egyptian Goose and Red-knobbed Coot fed largely by grazing. They were most abundant between March and June, occurring in greatest numbers at Lochinvar. Egyptian Geese occasionally nested on the flood-plain at Lochinvar between August and January, but there was no proof of the other species nesting there. Many Pigmy Geese and male Knob-billed Geese moulted on the lagoon at Lochinvar between March and June; small numbers of Egyptian Geese and Red-knobbed Coot also moulted in the Park, the former between February and May, the latter in June and July. The Spur-winged Goose fed mostly by grazing and grubbing. Numbers on the Flats were greatest between June and November when 60,000–90,000 moved downriver as the floods subsided. Many bred between January and March in the fringing zone and moulted on the floodplain between May and July. A hydroelectric scheme, completed in 1975, may benefit the Pigmy Goose and Red-knobbed Coot but harm the Spur-winged Goose.     

A review of diseases of parasites of the Kafue lechwe (Kobus leche kafuensis).

The diseases of the Kafue lechwe (Kobus leche kafuensis) are reviewed in this paper. Kafue lechwe are an important natural resource for Zambia. Bovine tuberculosis is widespread within the lechwe population and they are host to many parasites, especially the warble Strobiloestrous vanzyli.     

Trematode infections in freshwater snails and cattle from the Kafue wetlands of Zambia during a period of highest cattle-water contact

A total of 984 snails, comprising nine species, were collected from six areas in the Kafue wetlands between August and October 2003 to assess larval trematode infections. Of these, 135 (13.7%) were positive. Most trematode infections were recorded from Lymnaea natalensis (42.8%), which harboured four of the five morphologically different cercariae found. No trematodes were recovered from Bellamya capillata, Biomphalaria pfeifferi, Melanoides tuberculata, Physa acuta and Cleopatra nswendweensis. One snail (0.2%) of 416 Bulinus snails shed brevifurcate-apharyngeate distome cercariae while three (0.7%) shed amphistomes. Gymnocephalous and longifurcate-pharyngeate distome were the commonest types of cercariae recorded while xiphidiocercaria was the least common. The highest prevalence rates of F. gigantica (68.8%) and amphistomes (50.0%) in cattle (n = 101) were in Chiyasa while those in Kaleya had the lowest (9.1 and 18.2%, respectively). In most habitats, infections were recorded in both cattle and snails. Critical determinants of infection may have been the distance of settlements and/or cattle kraals, the number of animals in nearby homesteads and the presence of susceptible host snails. This study suggests that fascioliasis and amphistomiasis could be major constraints of cattle production in the Kafue wetlands because favourable factors were available to introduce and maintain the infections. It further provides a starting point for some comprehensive studies on snail-related aspects of transmission and snail host ecology in Zambia.     

Detritus and energy consumption and conversion efficiency of Sarotherodon melanotheron (Cichlidae) in a West African lagoon

The growth, standing stocks and production of tilapia Sarotherodon melanotheron (Cichlidae) in the 1 km² Sakumo Lagoon near Tema, Ghana, are estimated by application of recently developed models to previously published data. The new estimates are used to obtain values of food (i.e. sediment) consumption, some related statistics, and to assess bioturbation as caused by S. melanotheron.

Zusammenfassung

Detritus, Energieverbrauch und Konversionseffizienz von Sarotherodon melanotheron (Cichlidae) in einer westafrikanischen Lagune
Das Wachstum, die Biomasse und die Produktion von Tilapia Sarotherodon melanotheron (Cichlidae) in der 1 km² Sakumo Lagune bei Tema, Ghana, wurden bestimmt auf der Basis von neueren Modellen und bereits veröffentlichten Daten. Die neuen Modellparameter werden benutzt, um die Nahrungs-, d. h. Sedimentkonsumption und verwandte Größen zu bestimmen, und um die Bioturbation zu schätzen, die S. melanotheron verursacht.

Résumé

Détritus, dépense d'énergie et efficience de la conversion de Sarotherodon melanotheron (cichlidés) dans une lagune en Afrique de l'ouest
La croissance, la biomasse et la production du tilapia Sarotherodon melanotheron (Cichlidés) ont été estimées pour le stock de la lagune de Sakumo (1 km²), près de Tema, Ghana, en utilisant des modèles recents et des données déjà publiées. Les nouvelles valeurs sont utilisées pour l'estimation de la consommation en nour re (= sediment) ainsi que quelques autres charactéristiques de S. melanotheron , et pour estimer le taux de bioturbation qui résulte de ses activités.     

Ciliate protozoa in the rumen of Kafue lechwe, Kobus leche kafuensis, in Zambia, with the description of four new species.

The composition of the rumen ciliate fauna in 76 Kafue lechwe inhabiting a limited area in Zambia was surveyed and five genera containing 24 species with 16 formae belonging to the family Ophryoscolecidae were identified. Four new species belonging to Diplodiniinae were recognized and described as Diplodinium lochinvarense n. sp., Diplodinium leche n. sp., Diplodinium zambiense n. sp., and Metadinium ossiculi n. sp. In addition, Ostracodinium gracile form fissilaminatum Dogiel, 1932 was found for the second time and described as Metadinium fissilaminatum n. comb. The species composition was fairly unusual. Seven of the species have been found only in African wild antelopes and these species were found more frequently than cosmopolitan species. There was no evidence of isotrichid species. The average density of ciliates per 1 ml of the rumen fluid was 25.7 x 10(4), and the number of ciliate species per head of host was 10.8.     

Ciliate Protozoa in the Rumen of Kafue Lechwe, Kobus leche kafuensis, in Zambia, with the Description of Four New Species

ABSTRACT The composition of the rumen ciliate fauna in 76 Kafue lechwe inhabiting a limited area in Zambia was surveyed and five genera containing 24 species with 16 formae belonging to the family Ophryoscolecidae were identified. Four new species belonging to Diplodiniinae were recognized and described as Diplodinium lochinvarense n. sp., Diplodinium leche n. sp., Diplodinium zambiense n. sp., and Metadinium ossiculi n. sp. In addition, Ostracodinium gracile form fissilaminatum Dogiel, 1932 was found for the second time and described as Metadinium fissilaminatum n. comb. The species composition was fairly unusual. Seven of the species have been found only in African wild antelopes and these species were found more frequently than cosmopolitan species. There was no evidence of isotrichid species. The average density of ciliates per 1 ml of the rumen fluid was 25.7 times 10⁴, and the number of ciliate species per head of host was 10.8.     

Effect of temperature on growth of juvenile Oreochromis mossambicus and Sarotherodon melanotheron

Synopsis Survival and competitive ability of juvenile fish is often dependent on their growth rate. Temperature is the physical component of their environment which most affects growth rate. To determine the effect of temperature on the growth rate of two exotic warm water species we measured growth of Oreochromis mossambicus and Sarotherodon melanotheron at 25, 30 and 35°C. There was a significant interaction of species and temperature on growth. The growth rate of O. mossambicus was faster than that of S. melanotheron at 25 and 30°C but slower at 35°C. Weight gain of S. melanotheron was significantly greater at 30°C than at 25°C. Weight gain of O. mossambicus at 25 and 30°C was significantly greater than at 35°C. Temperature had no effect on the weight-length relationship of either species.Scientific Series No. 1546-AEL from UM-CEES, Appalachian Environmental Laboratory     

Naphthalene-induced changes in carbohydrate metabolism in Sarotherodon mossambicus Peters (Pisces: Cichlidae)

Sarotherodon mossambicus Peters was exposed to naphthalene concentrations ranging from 7.9 to 0.92 mg/l for periods ranging from 4 days to 10 weeks and changes in glycogen, glucose, pyruvic acid and lactic acid contents of liver and muscle were studied. While glucose levels remained unaffected, major effects could be seen in the other constituents following both lethal and sublethal naphthalene treatment. Whereas glycogen and pyruvic acid levels showed considerable reduction, lactic acid levels increased markedly. These changes are indicative of a metabolic stress leading to a shift to anaerobic metabolism. The effects do not appear to be related to the feeding and growth rates of the naphthalene-intoxicated fish.