The feeding ecology of Ambassidae (Osteichthyes: Perciformes) in Natal estuaries

The diets of three species of Ambassis in six estuaries of southern Africa were investigated using four methods of stomach content analysis. Diets varied from one estuary to another as the faunal composition changed according to physical conditions. Ecological separation among the species is achieved to a large extent through diet alone. While all Ambassis feed mainly on a wide variety of zooplankters, Ambassis productus and A. natalen-sis are also piscivorous and insectivorous respectively. Seasonal analysis of diet showed that A. gymnocephalus feeds mainly on fish eggs during winter (June-August). The possible impact of egg predation on fish numbers at St Lucia is discussed. Feeding periodicity was investigated using dry mass and volumetric methods. All Ambassis showed similar bimodal feeding intensities during the night with peaks in early evening and early morning. Food selection at different levels in the water column showed that all Ambassis feed mainly on food in suspension. Additionally A. natalensis feeds on surface prey while A. productus takes ben-thic prey. It is postulated that interaction between Ambassis and filter-feeding planktivores in St Lucia is minimal due to feeding strategies and feeding periodicity. In addition the impact of the piscivorous predatory role played by Ambassis on estuarine fish communities is emphasized.     

Stomach contents of some shore-caught teleosts of Natal,South Africa

Stomach contents of shore-caught teleosts feeding on the Natal nearshore substratum were visually analysed for percentage composition. Commonly caught fish, namely Rhabdosargus sarta, R. holubi, Pomadasys commersonni, Trachinotus africanus and T. botta, were opportunistic omnivorous predators and fed largely on sand mussels and benthic crustacea. Less frequently caught predatory fish (15 species) fed mainly on benthic crustacea and other teleosts. The results are discussed briefly and will provide an input to a current ecosystem study on the environment in which these fish feed.     

Aspects of the ecology of feral cats on Dassen Island,South Africa

Numbers of feral cats on Dassen Island (33°25'S/18°06'E) increased from 20–25 in May 1979 to 37–50 in June 1980. Kittens were born in eight months of the year with birth peaks in October-November and in January. Mean litter size was 2,7 and 80% of kittens born between August 1979 and January 1980 survived until June 1980. Kittens died from starvation and disease. In June 1980 51–56% of the cats were <1 year old. The number of cats is recovering rapidly from heavy culling. Depredation by cats is a potential threat to sea-bird colonies. The diet and feeding behaviour of the cats were studied in order to assess the importance of this threat. An ‘average’ cat's annual diet, assessed from scats, included: 134 European rabbits (Oryctolagus cuniculus), 37 jackass penguins (Spheniscus demersus), 25 Cape cormorants Phalacrocorax capensis), 31 other birds and 24 house mice (Mus musculus). Each cat killed 105 rabbits and 13 birds each year, the balance of its diet being made up by carrion. Adverse effects of the presence of cats, compared to other factors, were not yet so serious as to necessitate artificial control of cat numbers.     

Long-term trends in the shore fishery of the Transkei coast,South Africa

The hypothesis that a single dominant male (GAA) monopolized all matings within the elephant population of South Africa’s Addo Elephant National Park between 1982 and 1996 was tested using microsatellite analysis. In addition, behavioural data on male musth periods, female oestrous periods, and observations of matings were collected between 1996 and 1999, and used to determine whether there is any behavioural evidence of current mating monopoly by GAA. Exclusion analysis and a likelihood-based approach were employed to assess paternity using genetic data, although low genetic diversity in the Addo elephant population limited the power of these techniques. However, GAA could be excluded as father of a minimum of 34 % of calves, and was the most likely father of a maximum of only 28 % of calves. Behavioural data support the genetic data, since there is no indication that GAA monopolizes mating opportunities. Therefore, the hypothesis that a single dominant male has monopolized all matings within the Addo elephant population since 1982 can be rejected.     

A Study of Feeding in Some Inshore Reef Fish of the Natal Coast,South Africa

A detailed quantitative investigation of the feeding habits of seven important Natal inshore reef fish (Epinephelus andersoni Boulenger, 1903, Coracinus mulfifasciafus (Pellegrin, 1914), Pomadasys olivaceum Day, 1875, Diplodus sargus Linnaeus, 1758, Sarpa salpa (Linnaeus, 1766), Acanthurus triosfegus Linnaeus, 1758 and Neoscorpls lithophilus (Gilchrist & Thompson, 1908)) is described. Qualitative information on the feeding of 23 other species is also given, and when all species are considered the ratio of carnivores, omnivores and herbivores is 4:1:1.     

Further records of Penaeoidea from the East coast of South Africa

Fifty-four specimens of ten penaeoid species were identified. Of particular interest was the finding of pelagic juveniles of two species, Funchalia (Funchalia) villosa and Penaeus marginatus.     

Marine connectivity and fish length frequencies of selected species in two adjacent temporarily open/closed estuaries in the Eastern Cape Province,South Africa

The effects of timing, frequency and duration of mouth opening and marine overwash events on fish assemblages in two, adjacent temporarily open/closed estuaries were investigated. Sampling was conducted biannually over two years during summer and winter, using selective sampling gear to target estuarine-associated marine species. During this period the East Kleinemonde Estuary opened more frequently than the West Kleinemonde Estuary and it also experienced a greater number of bar overwash events when larval recruitment can occur. The timing of mouth opening and the frequency of marine overwash events did not influence species richness of marine-spawning species but had a pronounced effect on abundances (catch-per-unit-effort) of species. The species composition of both estuaries was similar, but the catch-per-unit-effort in the East Kleinemonde Estuary was more than three times greater than that of the West Kleinemonde Estuary. The East Kleinemonde also supported a greater proportion of immature individuals of Rhabdosargus holubi and Monodactylus falciformis, and the length frequency distributions of both these species differed significantly between the two estuaries. The larger fish sizes in the West Kleinemonde Estuary were attributed to the prolonged mouth closure that resulted in the trapping of larger juveniles and mature fish within the estuary.     

The diet,food selectivity and niche of Rhabdosargus sarba (Teleostei: Sparidae) in Natal estuaries

The juveniles and subadults of Rhabdosargus sarba are one of the most common components of the benthic fish community of Natal estuaries. The diet consists mainly of aquatic macrophytes and filamentous algae although a significant proportion is made up of bivalves and the amphipod Grandidierella lignorum. The last two taxa are positively selected when little plant material is consumed. R. sarba feeds during daylight with a peak in the early afternoon. The relationship between R. sarba and the very similar sympatric R. holubi and R. auriventris are discussed in relation to their diet, divergence and distribution. Resource partitioning in Natal estuaries between R. sarba, the Gerreidae and Pomadasys commersonii is also discussed.     

The life-cycle and seasonal abundance of Echinoparyphium montgomeriana n. sp. (Trematoda: Echinostomatidae) in Natal,South Africa

A new species of Echinoparyphium, E. montgomeriana, is described from Durban, South Africa. Certain unusual aspects of its morphology are discussed. The adult fluke is a parasite of the alimentary tract of birds. Its larval stages are common parasites of freshwater snails belonging to the family Planor-bidae including Buiinus africanus,the intermediate host ofSchistosoma haematobium and S. mattheei in the area. These intra-molluscan stages are shown to have a seasonal transmission cycle.     

Species identification,distribution and abundance of Gerreidae (Teleostei) Bleeker,1859 in the estuaries of Natal

Comparison of published meristic and taxonomic data with measurements taken from specimens collected from Natal estuaries have provided information for an identification key to the Gerres of southern Africa. Body markings were different on each species of fry (< 40 mm S.L.) as well as immatures and adults (> 40 mm S.L.). A comparison of otoliths from the different species showed that they can be used to Identify specimens from a standard length of 20 mm. Turbidity may be a factor limiting the distribution of the genus in estuaries. The known distribution of Gerres species in the estuaries of southern Africa is given. The species of Gerres which is dominant in a particular locality depends on the salinity.     

New host and geographical records of siphonostomatoid copepods associated with elasmobranchs off the KwaZulu-Natal coast, South Africa

The Siphonostomatoida (Copepoda) consists of 40 families comprised mainly of symbiotic members. Representatives of 12 families occur in symbiosis with elasmobranchs. Only eight families, 19 genera and 35 species have been reported from 37 elasmobranchs off the coast of South Africa. Elasmobranchs caught in the nets of the Natal Sharks Board and by fishermen of the Meer-en-See Boat Club, KwaZulu-Natal Province were examined for symbiotic siphonostomatoids. Additional to previous families reported, members of Cecropidae and Sphyriidae are being reported. Genera for the first time reported from South African waters include Entepherus, Carnifossorius, Eudactylina, Eudactylinodes, Kroeyerina, Pannosus, Phyllothyreus and Paeon. Therefore, currently ten siphonostomatoid families are reported from 49 species of elasmobranchs including 27 genera and 58 species.     

Recent records of megalopae of the crab Varuna litterata (Fabr.) entering Natal estuaries

An unusual occurrence Involving the stranding of many thousands of megalopae of the crab Varuna litterata on an outgoing tide is recorded. The locality was sandflats adjacent to the mouth of the Mgobezelenl estuary at Sodwana Bay, Natal, In mid-May 1985. Other records of recent local sightings are Included.     

Aspects of the ecology of the Asian tapeworm, Bothriocephalus acheilognathi Yamaguti, 1934 in yellowfish in the Vaal Dam, South Africa

Seasonal surveys were conducted at the Vaal Dam between April 2000 and January 2001. Twenty smallmouth yellowfish (Labeobarbus aeneus) and 20 largemouth yellowfish (Labeobarbus kimberleyensis) were collected with the aid of gill nets. Surface water quality variables were included. The cestodes were identified as either Bothriocephalus acheilognathi Yamaguti, 1934 or "other cestode spp.". The majority (99.8%) of the cestodes found in both yellowfish species were identified as B. acheilognathi (Asian tapeworm). The prevalence, mean intensity and abundance of B. acheilognathi in both yellowfish species were calculated. Ecological parameters including species specificity, seasonality, gender specificity and relationships between fish size and the Asian tapeworm prevalence were also included. In this study, B. acheilognathi preferred L. kimberleyensis over L. aeneus although a low intensity was observed in smallmouth yellowfish. Furthermore, the infection (in terms of prevalence, abundance and mean intensity) in largemouth yellowfish was markedly higher. Seasonal patterns observed in the Asian tapeworm's infection of smallmouth yellowfish are attributed to breeding and subsequent feeding patterns of this fish species with relatively high infections recorded in winter and spring. For L. kimberleyensis no explanation can be given regarding the seasonal patterns observed for the mean intensity and abundance of B. acheilognathi. The maximum and minimum mean intensity and abundance values in largemouth yellowfish were recorded in autumn and spring, respectively. In addition, the prevalence of B. acheilognathi was consistently high in all four seasons.     

The ecology of sandy beaches in southern Africa

The physical features, macrofauna and meiofauna of four exposed sandy beaches along the southern coast of South Africa were quantitatively investigated. All beaches had medium to fine sands with relatively poor to moderate macrofauna and very rich meiofauna. The results are compared with the present knowledge of the southern African coastline. Sandy beaches types around the southern African coastline are summarized according to geomorphology and wave action and three Zoogeographie provinces are recognized. The macrofauna is dominated by crustaceans, mostly scavengers, on the warmer east coast and by molluscs, mostly filterfeeders, on the temperate south coast. Relationships between diversity and abundance of macrofauna, beach slope and particle size are analysed in detail. Intertidal zonation of macrofauna is described and a zonation scheme based on crustaceans proposed. Relationships between meiofauna composition and particle size are described as well as intertidal distribution patterns of the meiofauna. The role of surf circulation patterns and macrofaunal food sources in determining beach trophic structure is emphasized.     

Description and ecology of larvae of Glossogobius callidus and Redigobius dewaali (Gobiidae) from temperate South African estuaries

This paper describes the morphology and ecology of the larvae and early juveniles of two common gobiids in warm temperate South African estuaries. The early developmental stages of Glossogobius callidus and Redigobius dewaali were collected during plankton surveys in seven permanently open and five intermittently open estuaries along southeastern South Africa. Larval G. callidus have a characteristic ventral row of pigment that extends from the cleithral symphysis along the ventral midline of the tail to the end of the caudal peduncle; notochord flexion takes place at the yolk-sac stage, between 3 and 4 mm BL. Larval R. dewaali are characterized by having two very large stellate melanophores on the ventral surface of the trunk and tail, and internal pigment between the snout and hindgut; notochord flexion takes place between 4 and 6 mm. Body lengths at settlement for G. callidus and R. dewaali are 13 mm and 16 mm, respectively. G. callidus and R. dewaali dominate the larval gobiid catch in warm temperate estuaries. Estuary type and freshwater input played a defining role in the occurrence of larvae of these, often sympatric, species in temperate estuaries. Larval G. callidus occurred in both permanently open and intermittently open estuaries, and were most abundant in mesohaline regions over the spring/summer period. By contrast, larval R. dewaali occurred exclusively in permanently open estuaries and were more prevalent in the fresh and oligohaline regions in autumn. Larvae of both species were more prevalent in freshwater-rich estuaries. Densities of G. callidus and R. dewaali peaked at 101 and 3829 larvae per 100 m³respectively. The usefulness of using the early stages of these gobiids as indicators of estuarine health based on their specific and often prolific estuarine occurrence is discussed.     

Exposure to wave action: some consequences for the sea urchin Stomopneustes variolaris on the Natal coast

Population size structure in the intertidal echinoid, Stomo- pneustes variolaris, has been observed to vary between habitats, in a manner which suggests the influence of factors in addition to variation in recruitment success. This paper reports on an investigation into the hypothesis thai exposure to wave action might be a factor accounting for the variation in population size structure between habitats at Sheffield Beach.     

The occurrence and feeding of Pomatomus saltatrix (elf) and Lichia amia (leervis) juveniles in two Cape south coast estuaries

The seasonal occurrence of Pomatomus saltatrix and Lichia amia juveniles in a permanently open (Knysna) and a periodically open (Swartvlei) estuary is described. P. saltatrix was caught only in Knysna from September to April. L. amia was found in both systems intermittently throughout the year. Small juveniles were most abundant from November to February in Knysna and from December to February in Swartvlei. Prey selected varies with size and species although there is some overlap. Behavioural and morphological differences are discussed in relation to prey selection.     

Mysidacea of the Mtentu River Estuary,Transkei, South Africa

The Mtentu River has a straight open tidal estuary flowing between steep grassy or indigenous forest-covered slopes. Total high-water surface area is about 0,3 km.^a The zooplankton was studied by periodic sampling over a period of thirteen months. Some physical characteristics of the estuary are presented. The seasonal and spacial distribution and relative importance of four species of mysid, is discussed. The most common mysid in the estuary was Mesopodopsis africana, although Rhopalophthalmus terrcmatalis, in view of its larger size, contributed more to the overall mass of mysids in the samples.     

The Ecology of Patella From the Cape Peninsula South Africa

Forty-six species were recorded in association with Patella spp., but most of these are casual associates, seeking temporary shelter. The shell surface offers an important substrate for algae.

The amphipod Hyale grandicornis is often associated with Patella, particularly in the juvenile stages. It is a facultative inquiline which vacates its hosts at high tide. The isopods Dynamenella australis and D. scabricula are predominantly associated with limpets and complete their life cycles under limpets. Choice chamber experiments demonstrate their preference for sheltering under limpets. The copepod Scutellidium patellarum is similar, but the association is more marked.

Calliopiella michaelseni (Amphipoda) is commensal and show a preference for certain limpet species. Its colour changes in relation to the host species. Feeding occurs on limpet faeces and algal fragments. The life cycle is completed under the limpet, two reproductive peaks occurring each year. Adults usually occur in pairs and there is a positive correlation between host and amphipod size. Juveniles remain with their parents initially, and then disperse to other limpets. Adult pairs may defend their host, excluding other amphipods. Calliopiella is strongly photonegative and thigmotactic.

The turbellarian Notoplanapatellarum is preferentially commensal with Patella oculus. This can be experimentally demonstrated. It feeds on small Crustacea, including Scutellidium.     

Parasites of South African wildlife. XII. Helminths of Nyala, Tragelaphus angasii, in Natal.

The helminths of 77 nyala, Tragelaphus angasii, from 4 game reserves in Natal, were collected, counted and identified. Ten nematode species and 4 nematode genera, a trematode species and paramphistomes, and 2 cestode genera were recovered from the antelope. Of these, a Cooperia rotundispiculum race, Gaigeria pachyscelis, a Gongylonema sp., Haemonchus vegliai, Impalaia tuberculata, an Oesophagostomum sp., a Setaria sp., Trichostrongylus deflexus, Trichostrongylus falculatus, the larval stage of a Taenia sp., a Thysaniezia sp. and Schistosoma mattheei are new parasite records for this host. Individual nematode helminth burdens varied from 3 to 13 493 and the total mean nematode burden was 700. The mean burdens of nyala from Mkuzi were the largest and those from animals from the Umfolozi Game Reserve and the False Bay Park the smallest. Ostertagia harrisi was the most prevalent nematode, and it was also the most numerous in nyala from Umfolozi, Mkuzi and False Bay. A race of Cooperia rotundispiculum was the most numerous in nyala from Ndumu. No clear-cut trends in the seasonal abundance could be discerned for any of the worm species recovered in this study.