OpenUCT :: Browsing by Author "Reed, Cecile C"

Browsing by Author "Reed, Cecile C"

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Open Access
Assessment of the population structure of the South African sardine Sardinops sagax using a multi-method approach and the morphological and molecular characterization of a stock-discriminating digenean parasite biotag of the genus Cardiocephaloides
(2017) Uzonnah, Nwamaka Mary-Immaculata; Reed, Cecile C; Van der Lingen, Carl D
An understanding of the population structure of commercially exploited species is essential for effective fisheries management. Fish stocks are typically identified based on the observation of differences in genetic and/or phenotypic characteristics between fish from discrete units. Recent deliberations on the management of the South African purse-seine sardine fishery recognises the likely existence of two stocks, one on the west and another on the south coasts, following studies that have documented spatial variability in several phenotypic characteristics of this species around South Africa. Those studies typically examined spatial variability in a single characteristic (e.g. gill raker morphology and meristics, body shape, otolith shape, vertebral count, parasite loads), but the application of multiple stock identification methods to the same individual fish has been recommended in order to maximize the likelihood of correctly inferring and identifying fish stocks. This study seeks to assess the population structure of South African sardine Sardinops sagax using a combination of stock identification methods including meristic, morphometric and parasite markers. Most of the sardine samples used in this study were obtained off the west and south coasts of South Africa during pelagic surveys conducted in 2013 and 2014 by Fisheries Branch of the Department of Agriculture, Forestry and Fisheries, with some additional samples obtained from commercial fisheries. Fish caught from the west and south coasts are presumed to be part of the putative western and southern stocks respectively. The variables examined included body shape, gill arch length, gill raker spacing, number of gill rakers, otolith shape indices (otolith circularity and form factor), the number of vertebrae, and the abundance of a 'tetracotyle' type metacercarian parasite found in the eyes of sardine; these were first analysed individually and then collectively (excluding body shape data) in a multivariate analysis to test their effectiveness in discriminating between sardine from the putative western and southern sardine stocks. Analysis using geometric morphometrics revealed significant differences in body shape between sardine from the putative western and southern stocks. Results of GLM analyses indicated that gill arch length, the number of gill rakers, otolith form factor and circularity, and parasite abundance were effective univariate discriminators of sardine stocks. No significant difference in gill raker spacing and the number of vertebrae was found between individuals from the two stocks. A Stock Identification Index (SDI) of 0.75 derived from the univariate analyses, as well as results of the multivariate analysis of data provided strong evidence for the existence of two mixing stocks, therefore, supporting the two-stock hypothesis. The five multivariate classification models used in the study showed varying degree of allocation success. Overall classification accuracy ranged from a low 47% in the Linear Discriminant Analysis model to highs of 82% and 91% in the Classification Tree Analysis and Random Forest models, respectively. Both CTA and RF revealed the combination of variables with the strongest spatial discriminatory power to be the number of vertebrae and abundance of the 'tetracotyle' type metacercarian parasite. These results agree with those of previous studies and further support the inclusion of sardine population structure into management strategies for the purse-seine fishery for South African sardine. Given the importance of the 'tetracotyle' type metacercaria in the discrimination of South African western and southern sardine stocks, further studies were undertaken to identify and describe this parasite using light and scanning microscopy, as well as molecular tools. Such information will assist in the definitive identification of the first intermediate host of the parasite, presently hypothesized to be a sub-tidal gastropod occurring off the west coast only. Definitive identification of the first intermediate host (or hosts) will enable the full life cycle of this parasite to be determined and the parasite endemic area to be identified; a critical knowledge gap in application of the parasite biotag approach to stock discrimination using this 'tetracotyle' type metacercarian parasite. Metacercariae collected from fresh sardine sampled from a commercial landing in Gans Baai, South Africa, were manually excysted, relaxed in warm water, fixed in 70% ethanol and stained with haematoxylin for light microscopy. The metacercarial body is oval-shaped, measuring 762 - 967 x 512 - 677μm. It is divided by transverse folds into a forebody, midbody and hindbody. Diagnostic features include the unique, large excretory bladder lobes situated on the lateral sides of the body; two large pseudosuckers in the anterior part of the midbody; an acetabulum which is larger than the oral sucker; and a large lobulated holdfast organ in the posterior half of the midbody. These features are those of the metacercariae of the genus Cardiocephaloides, confirming the previous hypothesis regarding the genus of this digenean biotag. Analysis of partial 28S rDNA region sequence data showed that the metacercariae and the adult Cardiocephaloides found in the African penguin Spheniscus demersus are of the same species, likely C. physalis. This study is the first documentation of the morphological and molecular characterization of the stock-discriminating Cardiocephaloides metacercaria found in the eyes of Sardinops sagax in South Africa.
Open Access
Biodiversity patterns of wetland macroinvertebrate assemblages in the South-Western Cape, South Africa
(2009) Mlambo, Musa; Day, Jenny; Reed, Cecile C
Despite the recent surge in interest in wetland invertebrates, given their immediate importance in overall wetland functioning, these studies have largely been conducted in the northern hemisphere and very little is known in South Africa. In order to fill this knowledge vacuum, this study was conducted to investigate biodiversity patterns of wetland macro invertebrates assemblages in the south-western Cape, South Africa. 140 wetlands were sampled in four geographic clusters, the Cape Flats, the West Coast, the Cederberg and the Agulhas Plain. Open-water, submerged vegetation and emergent vegetation habitats were sampled separately using a square-framed sweep net with a 23.5cm mouth and 80l1m mesh and physico-chemical attributes measured at each site. A total of 126 taxa emanating from more than 26 000 individuals representing 73 genera and 51 families was recorded. Currently, five species new to science were also discovered, three from Hydraenidae (Prosthetops sp. nov, Parhydraena sp. nov and Mesoceration repandum Perkins, 2009), Hydryphantidae (Hydryphanres sp. nov) and Streptocephalidae (Streptocephalus sp. nov). However, all of these new species but one were recorded from single location, suggesting that they might be rare or unique. Richness estimators predicted true taxon richness at about 20-47 taxon more than the observed taxon richness. The high number of uniques and singletons, as well as the Incidence-based Coverage Estimator, suggest that sampling was not adequate to capture the full biodiversity suite. However, I believe this is not necessarily true and this is discussed in detailed in the discussion. The sub-area Cederberg was found to be the biologically richest area, with the three of the new species recorded there. A significant difference was observed in relative abundance (RA) and frequency of occurrence between open-water habitat and vegetated habitats (submerged and emergent vegetation). On the other hand, a significant difference was not found between wetlands with different number of habitat types. No appreciable congruence was seen between different taxonomic groups (i.e. at order and family level) themselves, suggesting that neither can be used as a surrogate for the others. However, predators - which by the way had the highest frequency of occurrence and 2nd highest relative abundance after gatherers - were strongly correlated with overall assemblage and Hemiptera. In addition, together with Hemiptera they had ≥75% similarity with the overall assemblage, suggesting that they are fairly good surrogates for overall assemblage. These results are quite promising especially for biomonitoring programmes and warrant further research. Environmental variables contributed significantly higher in explaining assemblage composition, and the model containing pH, Phosphate, conductivity, turbidity and ammonium was found to explain significant variation in macro invertebrate assemblage.
Open Access
The biology and macroparasites of the sixgill sawshark Pliotrema warreni
(2017) Foor, Brandon; Attwood, Colin; Reed, Cecile C
Thirty-two specimens of the sixgill sawshark, Pliotrema warreni, were trawled near Bird Island in Algoa Bay on the Eastern coast of South Africa in April and May 2015. The specimens were examined for anatomical proportions, reproductive characteristics, diet, and parasite assemblages. Several external measurements were collected including mass, total length, standard length, girth, rostrum length, interoccular to pre-caudal length, first dorsal origin to second dorsal origin, first dorsal origin to pre-caudal origin, and mouth width. The equation for mass (g) vs. total length (mm) was ln(Mass)=0.2997*ln(TL)+2.0383 for females and ln(Mass)=0.3321*ln(TL)+1.941 for males. 1st Dorsal to 2nd dorsal origin length (DD) to total length equations for females and males were DD=0.2451*TL-26.677 and DD=0.2598*TL-34.535, respectively. Mean lengths and masses were 11.5% greater and 50.3% heavier in females than males, respectively. Females were on average, 994 mm (759 mm – 1283 mm) in length while males were 891.8 mm (763 mm – 1015 mm). Average mass for females was 1702.5 g (602.5 g – 3478.5 g) whereas males it was 1132.6 g (687 g – 1593.5 g). Based on these data both sexes display isometric growth. Males were determined to reach sexually maturity around 850 mm which is similar to that reported by Ebert et al., (2013) around 830 mm. Females were found to reach sexual maturity at 1000 mm which is 100 mm smaller than what is reported by Ebert et al., (2013). Stomach mass increased with total mass and total length regardless of sex (female R² = 0.507; male R² = 0.213 for length and female R² = 0.6123; male R² = 0996 for mass). Females consumed larger prey items in terms of mass and length as well as a higher quantity of prey than males presumably because they are the larger sex and have an increased need for nourishment to provide for pregnancy. Prey items were redeye round herring, Etrumeus whiteheadi (64.96% of the diet), a benthic shrimp species not identified (7.69%), and Cape horse mackerel, Trachurus trachurus capensis (0.85%). Despite strict adherence to the guidelines for age determination for elasmobranchs provided in the literature, the conventional method used which involved extensive cleaning of the vertebral centra with an array of chemicals, setting and cutting in an epoxy resin, and staining for microscopy, did not yield readable results which could be used to determine the ages of these sharks. The highest abundance of parasites were found in the stomachs. Three specimens of a cymothoid isopod was found externally. Two specimens of Ascaris sp. nematode were found in the visceral cavity. The remaining 18 parasites consisted of three Neoechinorhynchidae sp. of acanthocephalan and 15 Proleptus obtusus nematodes all of which were found inside the stomachs. Given the results of the parasite survey, males and females do not have the same parasites as females have four different species while males only have one. More collections from other areas and times of year are necessary to obtain a better description of the species.
Open Access
Estimates of length-at-50% maturity of two South African demersal species: Monkfish, Lophius vomerinus, and Kingklip, Genypterus capensis
(2019) Guerra, Alessandro; Attwood, Colin; Reed, Cecile C; Singh, Larvika
Long-lived and slow-growing fish species are especially vulnerable to overfishing. Deep-sea species are elusive and difficult to study, making their management challenging. South African monkfish, Lophius vomerinus, and kingklip, Genypterus capensis, are two demersal species living off the west and south coast of South Africa. These species are exploited as bycatch in the Hake fisheries, and represent an important resource for the fishery. However, reproductive information is scarce, and key life-history parameters have not been updated in recent years. Length-at-50% maturity (L50) is a fundamental biological parameter to monitor stock-health, spawning potential and improve fishery management. This research was focused on computing L50 estimates for both species, separated by sex and coast. As the stock structure for both species is still under debate, reproductive information and L50 estimates were compared between west and south coast. In addition, L50 was compared with previous studies to detect significant differences or changes over time. Demersal survey samples were used. Individuals were classed a 5 stage maturity scale and consequently referred to as mature or immature. For L. vomerinus, a significant difference in L50 between sexes was found, in contrast with previous findings in literature. However, no significant difference between the two areas was reported, corroborating the one-stock hypothesis. Furthermore, I speculate that L. vomerinus aggregate for spawning activities. The analysis of G. capensis revealed differences between coasts, reinforcing the theory of multiple South African stocks. Most importantly, the results showed a critical reduction in females L50 from previous studies. This reduction is believed to be a consequence of excessive fishing pressure exerted particularly during the latter half of the 20th century, which overexploited immature females on the west coast and main female spawners on the south coast. Further research needs to be done to verify these findings and the stock structure of the populations.
Open Access
Habitat association and distribution of Nauticaris marionis at the Sub-Antarctic Prince Edward Islands
(2016) Haley, Craig; Atkinson, Lara Jane; Von der Meden, Charles; Reed, Cecile C
The habitat associations between the caridean shrimp Nauticaris marionis and sessile epibenthic assemblages and substratum types of the Sub-Antarctic Prince Edward Islands were investigated. Twenty five stations, varying in substratum type, depth and location on the shelf and slope around the islands were sampled photographically with a towed benthic camera sled. At each station the substratum type was classified, sessile epibenthic cover was quantified through the use of digital quadrats and shrimp density was estimated. Results add to the broadly described distribution patterns of N. marionis by identifying specifically the habitat characteristics they generally utilize. The distribution of N. marionis was found to be influenced by a combination of substratum and sessile epibenthic assemblages, but not substratum type alone. Shrimp inhabited stations with >50 % biogenic cover on mud and gravel substrata, but were not found at stations with rocky-sand or rocky-mud substrata. Their distribution appears to also be influenced by depth, as shrimp were only found within a depth range of 50 - 160 m in this study. A strong correlation was found between N. marionis density and depth. Shrimp were found both inshore around the islands, and on the relatively shallow saddle between the islands. In comparison with previous studies, N. marionis was found at similar, if not higher, densities in this study, although they occupied a narrower depth range.
Open Access
Instrumental conditioning and learning in Poroderma Pantherinum
(2017) Meyer, Imke; Reed, Cecile C; McCord, Meaghen
Recent research has shown that higher cognitive functions and learning occur in teleosts and elasmobranchs. Very little is known about the cognitive abilities of benthic sharks and no research has been published on the learning ability of the endemic Leopard catshark (Poroderma pantherinum) species of South Africa. This species is listed as data deficient on the IUCN red list and known threats due to anthropogenic impacts include fatalities because of bycatch and depredation in the small-scale commercial fishing industry. It has been suggested that sharks can be attracted to fishing boats through the sound of outboard motors and an association can be formed between the sound and easy prey on the hooks of fisherman. This pilot study examined the learning capacity of Leopard catsharks in Hermanus, South Africa, by using a series of food-reward tests based on instrumental conditioning. A target with black and white stripes was used as the discriminative stimulus, while an auditory cue acted as a bridging stimulus for the food-reward task. Sharks were collected by hand whilst diving and shore-angling in Hermanus from August 2015 to November 2015 and acclimatised before the onset of experiments. Four juvenile sharks were trained through operant conditioning using visual and auditory stimuli for ten days each, consisting of six trials per day. A fifth juvenile shark, acting as the control, was trained through the same method without the auditory stimulus to test the influence thereof on the learning rates of Leopard catsharks. This study showed that Leopard catsharks have the ability to associate a visual stimulus with a food reward through the aid of an auditory cue. The auditory cue was also shown to increase learning rates significantly as an association was formed between the presence of food in front of the target and the auditory signal. The individual sharks in this study displayed differing levels of stress and learning rates. It is suggested that even though Leopard catsharks show high diversity in learning rates and adaptation to stress, they possess the ability to learn and adapt rapidly to changing environments. The results possibly have important implications for the understanding of learning and conditioning in Leopard catsharks and the likely anthropogenic threats caused through learned behaviour in benthic sharks.
Open Access
Investigating trophic interactions between parasites and their marine fish hosts using stable isotope analysis
(2018) Weston, Mark Jonathan; Reed, Cecile C; Van der Lingen, Carl D
Parasitism is accepted as being an essential driver in the organization of biological communities. However, although there are estimated to be more parasitic than free-living organisms, parasites have been largely neglected from ecological studies and we have a relatively limited understanding of their trophic ecology. Hence, in order to incorporate parasites into food-web models and ecological studies, basic trophic interactions between parasites and their hosts need to be assessed. Here, I investigated host-parasite interactions using stable isotope analyses on a broad range of marine fish hosts and their associated copepod and monogenean gill parasites. The study also provides insight into the gill parasite diversity of a number of host species from South African marine waters. Seventeen species of fish hosts, ranging from lower to upper trophic levels, were collected from South African waters in 2015 and 2016 during surveys conducted by the Department of Agriculture, Forestry and Fisheries from South African waters. These host species were; Thunnus albacares, Thunnus maccoyii, Thunnus alalunga, Thunnus obesus, Isurus oxyrinchus, Prionace glauca, Xiphius gladius, Brama brama, Thyrsites atun, Seriola lalandi, Sarda sarda, Genypterus capensis, Merluccius paradoxus, Merluccius capensis, Lampanyctodes hectoris, Sardinops sagax and Trachurus capensis. The head region, gills and operculae from a total of 1513 fish were examined and any ectoparasites removed, identified down to the lowest taxonomic level possible, and counted. A total of 32 parasite taxa, comprising 20 copepods and 12 monogenean species, were recorded. Two new host records and 15 new geographic records for South Africa were catalogued. The new host records are Mazocraes sp. infecting T. atun, and Caligus dakari infecting T. capensis. The new locality records consist of Euryphorus brachypterus recovered from T. alalunga and T. obesus, Pseudocycnus appendiculatus recovered from T. albacares, T. alalunga and T. obesus, Hexostoma sp. recovered from T. albacares and T. obesus, Nasicola klawei recovered from T. albacares and T. obesus, Tristoma adcoccineum recovered from X. gladius, Eobrachiella elegans and two species from the genus Parabrachiella recovered from S. lalandi and Anthocotyle merlucci recovered from M. paradoxus and M. capensis. These new records have substantially contributed to the known parasite biodiversity within the South African marine environment. Host-parasite interactions between 15 species of fish host and their copepod and monogenean gill parasites were investigated by means of stable isotope analysis. Host white muscle tissue, host gill tissue and parasite samples were analysed for their carbon and nitrogen isotopic signatures. Results indicated that δ¹⁵N is tissue-specific, with host white muscle tissue showing significantly greater enrichment in ¹⁵N compared to host gill tissue (n =60; Z=5.66843; p<0.00001), and as gill tissue is what the parasites are presumably feeding on, host gill tissue was therefore selected as the most appropriate proxy.
Open Access
Metabolic changes to GLUT-4 levels in urban Chacma baboons on the Cape Peninsula: raiding their way to type 2 diabetes?
(2013) Van Velden, Julia; Reed, Cecile C; Kohn, Tertius
The Chacma baboons (Papio ursinus) of the Cape Peninsula are established raiders of human food, leading to widespread conflict between this intelligent, adaptable species and humans. The modern Western diet that these baboons have become exposed to has many deleterious effects on health, including obesity and type 2 diabetes. The aim of this study was to investigate whether this population of baboons have lowered GLUT-‐4 transporter protein levels in comparison to wild-‐feeding baboons, as an indication of insulin abnormalities. GLUT-‐4 levels were analysed via Western Blot and DXA scanning was used to compare physical characteristics between these two groups. No significant difference in GLUT-‐4 levels was found, however the two groups differed in three physical variables, with the semi-‐provisioned Peninsula group having higher total weight (kg)(p<0,05), total body lean mass (kg) (p<0,01) and bone mineral content (kg)(p<0,001) than the wild-‐feeding controls. These results indicate that male individuals from the Peninsula population are bigger but not fatter than wild-‐feeding male baboons from the Eastern Cape population. Although it could not be determined whether human food is causing insulin abnormalities in the Cape Peninsula’s population of Chacma baboons, this study indicates that this is a promising area of research, likely to affect the management strategies used on this population.
Open Access
Observations on myxozoans (Myzozoa: Myxosporea) and the spatial and temporal variation in parasite assemblages of the nosestripe klipfish, Muraenoclinus dorsalis Bleeke, 1860 (Perciformes: Clinidae)
(2010) Tang, Laura; Reed, Cecile C
The coast of South Africa is one of the most biologically diverse marine systems in the world but little is known about the parasites occurring in this environment. A survey of the parasites of an intertidal clinid, Muraenoclinus dorsalis Bleeker, 1860, captured from Granger Bay, Kommetjie and Jacobsbaai, South Africa during Summer 2008/2009 and Winter 2009 revealed twenty-three parasitic species. Five myxozoans, all likely new to science, were found to infect M dorsalis. Ceratomyxa sp. and Sphaeromyxa sp. 1 were found in the gall bladder and bile ducts, Kudoa sp. in skeletal muscle, and a Myxobolus sp. on the eyes. Spores of Ortholinea sp. were also detected in gall bladder squashes, but the actual location of infection is unknown. The endoparasite community composition and structure, and their persistence over space and time were also probed. Non-metric multidimensional scaling, cluster analysis and Analysis of Similarity showed that community composition during both summer and winter differed most between Kommetjie and Jacobsbaai, the sites geographically furthest apart. This observation implies a decay in similarity over geographic distance. The endoparasite component communities from Granger Bay showed no significant dissimilarity in composition between summer and winter while the component communities from Kommetjie showed little dissimilarity (Global R: 0.105; p-value = 0.002). These results suggest that season or seasonassociated factors play weak roles at both localities. Contrastingly, the summer and winter component communities from Jacobsbaai showed significant dissimilarity (Global R: 0.201; pvalue = 0.003) because of the higher parasite load in winter. This is attributed to the sheltered nature of Jacobsbaai, where violent winter waves do not disturb the fish but rather push up the tide thereby extending the submergence period of M dorsalis. A longer period of submergence may provide parasites with increased opportunities to infect a host. Nestedness analysesconfirmed a nested subset structure in all component communities, likely a result of differentiated colonization, passive sampling, or a combination of both. This result lends evidence to the theory that parasite community structure is persistent over space and time and that there are laws in parasite ecology.
Open Access
The occurrence of a testicular coccidian Eimeria sardinae (Thélohan, 1820) (Reichenow, 1921) in southern Africa sardine Sardinops sagax (Jenyns, 1842)
(2013) Ssempa, Nurudean Norman; Reed, Cecile C; Van der Lingen, Carl D
A total of 553 male southern African sardine Sardinops sagaxcollected between 2010 and 2012 from around southern Africa, including from the northern Benguela off Namibia and from the South African west, south and east coasts, were examined for the occurrence of a testicular coccidian Eimeria sardinae to assess its potential use as a "biological tag" in order to differentiate between hypothesized discrete sardine stocks within the region. Sardine from Namibia and from the South African east coast showed no infection by E. sardinae, whereas fish from the South African west and south coasts were infected. Average prevalence infection values of 48.9 ± 6.3 and 48.1 ± 9.7% were recorded for sardine from the west and south coasts. Average infection intensity of 49.5 ± 15.8 oocysts per sample was recorded for the west coast and 69.8 ± 33.5 oocysts per sample for the south coat sardine. There was no significance difference in E. sardinae infection (t=0.08; p=0.94) in S. sagax from the South African west coast and south coast. These results provide some support for the hypothesis of multiple sardine stocks off southern Africa and hence are important for fisheries management. The intensity of infection had a significant (Analysis of Variance-NOVA, p<0.05) negative effect on the gonadosomatic index values of infected fish from both the west and south coasts. There was a declining trend in condition factor values with increasing intensity of infection category, however no significant effect was observed. The marked negative effect of infection intensity on GSI, with heavy infection possibly leading to parasitic castration, has potentially important implications for sardine population dynamics and requires futher research.
Open Access
Parasite assemblages of Cape horse mackerel (Trachurus capensis Castelnau, 1861) from the northern and southern Benguela
(2013) Le Roux, Jessica Louise; Reed, Cecile C; Van der Lingen, Carl D
A survey of parasites infecting Cape horse mackerel, Trachurus capensis Castelnau, 1861, from both the southern and northern Benguela ecosystems was conducted to test the hypothesis of discrete stocks in each subsystem. One hundred and twenty five T. capensis of two size classes were collected off the coasts of South Africa and Namibia and their bodies and organs were examined for parasitic infections. Differences in parasite assemblages between smaller and larger T. capensis within each subsystem, between T. capensis of each size class from the two subsystems, and between larger fish collected in different seasons within the southern Benguela, were assessed. A total of twenty-nine parasite species were found infecting T. capensis. Ten of these were identified to species level (Ceratomyxa australis, Davisia donecae, Ectenurus lepidus, Gastrocotyle trachuri, Goussia cruciata, Lernanthropus trachuri, Nybelinia lingualis, Rhadinorhynchus cadenati, Scolex pleronectis and Tergestia laticollis), three to genus level (Anisakis sp., Caligus sp. and Kudoa sp.). Significant spatial differences in T. capensis parasites were observed, with larger fish differing in infection intensity and abundance of Anisakis sp. and infection intensity of L. trachuri. Significant spatial variation in parasites was also observed in smaller fish, which differed in Anisakis sp. abundance, L. trachuri infection intensity and abundance, G. trachuri abundance and G. cruciata infection intensity and abundance. Significant fish size effects on T. capensis parasites were also observed in both subsystems. Anisakis sp. infection intensity and abundance and G. cruciata abundance differed significantly between larger and smaller fish from the southern Benguela. Larger and smaller fish from the northern Benguela differed in G. cruciata infection intensity and abundance, G. trachuri abundance and L. trachuri abundance. No seasonal differences in parasites of larger T. capensis from the southern Benguela were observed. By using a discriminant function analysis parasite abundance data correctly assigned 92% of larger fish and 96% of smaller fish to their respective southern and northern Benguela sub-populations or stocks. These results show that analyses of parasites can be used to infer population structure and support the hypothesis of distinct T. capensis stocks in the northern and southern Benguela subsystems.
Open Access
Parasite communities associated with the Cape gurnard (Chelidonichthys capensis) and the lesser gurnard (C. queketti) from South Africa
(2019) Mackintosh, Amy Leigh; Reed, Cecile C; van der Lingen, Carl D
The Cape gurnard (Chelidonichthys capensis) and the lesser gurnard (Chelidonichthys queketti) are two members of the Triglidae family found off Southern Africa. Chelidonichthys capensis is distributed from depths of 10 m to 390 m in subtropical waters between Namibia and Mozambique, while C. queketti is distributed from 0 m to 150 m in subtropical waters from Namibia to southern Mozambique. Little is known about the biology, ecology and life cycles of these two species. Additionally, the parasite community of these two gurnards has not yet been surveyed, although there are records of a number of copepods infecting both species that have been documented for taxonomic purposes. This study aims to examine the macroparasite assemblages of both gurnard species from the west and south coasts of South Africa and determine whether the parasite communities show significant intra-specific, special differences or inter-specific differences. A total of 70 Chelidonichthys capensis and 87 C. queketti were examined, with a total of 13 parasitic taxa found infecting C. capensis, ten of which are new host records, while 15 parasitic taxa were found infecting C. queketti, 13 of which are new host records and one of which is a new geographic record. The nematode Anisakis pegreffii was the most prevalent parasite infecting C. capensis (75.7%), and an unidentified cyst was the most prevalent parasite infecting C. queketti (69%). Parasites recorded to infect both gurnard species include the cestode Tentacularia coryphaenae, the acanthocephalan Corynosoma australe, and the copepods Lernentoma asellina and Medesicaste penetrans. A Caligus species was only recorded to infect C. capensis and the unidentified cyst was only recorded infecting C. queketti. This study was also able to identify two biological tag species for potential use in population structure studies of both gurnards, namely A. pegreffii and T. coryphaenae, based on significant regional differences in prevalence and infection intensity levels. In comparison to other Chelidonichthys species, C. capensis has the second highest and C. queketti has the third highest number of recorded parasite taxa, with C. lucerna having the highest number (22 species) of parasites recorded. The new host records for C. capensis and C. queketti, and the new geographic record, contribute to our knowledge of these demersal fish species and of marine biodiversity in South Africa.
Open Access
The parasites of Callorhinchus capensis (St. Joseph elephant fish).
(2012) Awa Solange Bih; Reed, Cecile C; Moloney, Coleen
The extent of parasitism by macroscopic parasites was assessed and the relationships between the parasites and their fish hosts in terms of sex, size and the condition factor of the fish were investigated.
Open Access
Parasites of Kunene horse mackerel Trachurus trecae (Smith-Vaniz, 1986) with a comparison of parasites of Cape horse mackerel T. capensis (Castelnau, 1861) in the northern Benguela
(2013) Bowker, Jenna; Reed, Cecile C; Van der Lingen, Carl D
Two species of horse mackerel (Trachurus trecae and Trachurus capensis) reside in the northern Benguela ecosystem. Both are important economic commodities for the Angolan and Namibian fisheries and therefore need to be managed appropriately. Although the two species of horse mackerel share similar morphological characteristics and co-occur in Namibian waters in the northern Benguela, few studies have compared their parasite assemblages. To date there are no studies regarding the parasite profile of T. trecae. This study is the first to identify and document the parasite assemblage of T. trecae from the northern Benguela and forms the only parasite profile for this horse mackerel species. This study also assesses the effects of fish size and fish sex on the parasite assemblage of T. trecae, and compares the parasite assemblage of this species with that of T. capensis from the northern Benguela. Results indicate that the largest significant difference in parasite assemblage is between the two horse mackerel species (by convention p<0.01), but that significant differences are also found between small and large T. trecae and between immature, male and female T. trecae. The coccidian Goussia cruciata was found to have the strongest discriminatory power in all comparisons, and therefore serves as a potential indicator parasite or biotag for discriminating between different stocks of T. trecae and between T. trecae and T. capensis in the northern Benguela. Due to the lack of literature regarding the life history of T. trecae it is difficult to assess why there are sex effects on parasites infecting this species, as well as whether the interspecific difference in parasite assemblage is due to environmental conditions or species-specific relationships. Further investigations regarding the life history of T. trecae would assist interpretation of the results obtained here. This study provides a comprehensive knowledge of the parasite assemblages infecting T. trecae and thus lends to possible future studies regarding T. trecae stock structure. It also provides a starting point for conducting studies of the parasite assemblages of other fish in the northern Benguela.
Open Access
Resurrection ecology of invertebrates in temporary wetlands in the Cape Floristic region: effects of urbanisation and fire
(2017) Blanckenberg, Michelle; Mlambo, Musa; Reed, Cecile C
Despite their importance to regional biodiversity, temporary wetlands and their invertebrate communities are generally understudied and under-conserved. Resurrection ecology is used to study the communities present in the dry phase of temporary wetlands to gain a better understanding of the functioning and health of these systems. The hatching success of invertebrate propagules in dried soil sediments, collected from temporary wetlands in Cape Sand Fynbos regions of Cape Town, were investigated in 2016. Soil samples were collected from conserved and urban sites (during May and June 2016) using a standard soil auger method and complemented with monthly aquatic phase sampling using standard sweep net methods (during September and October 2016). The effects of fire were tested, on hatching success by staging vegetation fires over the collected soil samples for five temporary wetland areas in the same region. Mann-Whitney U tests were used to test differences in abundances between treatments, whereas for comparison of taxon richness, Shannon diversity and Pielou's evenness linear mixed effect models (LMER) were used. Non-metric multidimensional scaling (nMDS) plots were used to graphically visualize the community composition between the different treatments, with 'adonis' analysis used to test their statistical significance. Results found a total of 18 invertebrate taxa hatched, while a total of 27 taxa were identified from the wet phase. Results from hatching assays showed no significant differences in diversity patterns of invertebrates between conserved and urban areas in the dry phase. However, wetlands that were in the conserved area supported higher invertebrate diversity during the wet phase, although not significant (lmer, Z = -1.75, p = 0.08). These results suggest that human activity (alien vegetation, littering and polluting) in the area did not impact the ability of invertebrate propagules to emerge, but did slightly affect the natural aquatic phase. Fire had a significantly negative impact on invertebrate diversity measures (lmer, p < 0.001) and community composition (adonis, F = 24.494, p = 0.001) during hatching assays. Management of unpredicted and uncontrolled fire in urban areas is essential to ensure future protection of critical biodiversity areas created by these temporary wetlands. More research should focus on the impact of increasing fire frequency and intensity on these systems to understand the management challenges in a changing climate.
Open Access
Stream invertebrates and water temperature : evaluating thermal tolerances in the Cape floristic region (South Africa) - implications of climate change
(2009) Ketley, Zoma Anne; Picker, Mike; Reed, Cecile C; Dallas, Helen Fiona
Temperature is an important environmental variable for aquatic invertebrates as it affects their development, reproduction and survival. Temperature also affects the abundance and distribution of individuals in a stream or river. Stream temperatures are affected by human impacts which include not only impacts such as pollution, abstraction of water and the removal of riparian vegetation, but also the affects of climate change. In the Western Cape Province, South Africa, it is predicted that air temperatures will increase and winter rainfall will decrease. This in turn will affect water availability and water temperatures in streams and rivers. Thermally sensitive species are threatened by increases in water temperature, but currently very little information exists on the thermal tolerances of aquatic invertebrates in South Africa. In order to rectify this problem baseline data on thermal tolerances of aquatic species needs to be collected, together with stream temperature and associated invertebrate community data. An attempt was made to collect some of these much needed data in the Western Cape Province. Two methods, namely Critical Thermal Maxima (CTM) and LT₅₀ experiments, were used to determine the thermal tolerances for a range of aquatic insect nymph species from the southwest fynbos bioregion and the south coast fynbos bioregion. The results from the experiments provided information on the relative thermal sensitivities of the species. Overall Aphanicerca capensis (form C and undescribed form), Notonemouridae ranked as the most thermally sensitive for both experiments. The A. capensis species complex (and possible other notonemourid stoneflies) may potentially be used as an indicator of changing stream temperatures in the Western Cape Province. To rapidly determine thermal sensitivities the CTM experiments are recommended rather than the more time consuming LT₅₀ experiments as the relative thermal tolerance for the species tested ranked the same for both experiments. It is suggested that LT₅₀ experiments of longer duration be investigated in order to compare the experiments to naturally-occurring thermal stress. Stream temperature and community composition data were collected from Window Gorge Stream, on Table Mountain, to provide baseline data for future monitoring and understanding of potential changes in thermal profiles. Temperature loggers were placed at six sites along the stream. Stream temperatures were fairly low but the stream ran dry during the late summer months (February through to April/May). From the community composition data collected the highest diversity was found during the winter months, as expected. The community composition did change down the length of the stream, with the species composition found near the source being quite different to that of the species composition found lower down the mountain. Temperature and associated oxygen saturation were two important variables related to the community composition down the length of the stream. It is important that experimental data be combined with field data, enabling field sampling to focus on the collection of information on the abundance of the thermally sensitive species (e.g. A. capensis species complex). Recorded stream temperatures also provide reference conditions for the species tested in the laboratory. Climate change is likely to have an affect not only on stream temperatures but also on water availability, which will both influence stream communities and ecosystems and it is important to understand what these potential effects might be.
Open Access
A survey of the metazoan parasite assemblage of snoek, Thyrsites atun (Euphrasen, 1791), off South Africa with an assessment of host-parasite relationships and potential biological tags
(2015) Nunkoo, Muhammad Azher Irfan; Reed, Cecile C; Kerwath, Sven E
Parasites are a ubiquitous but often unseen, unacknowledged and understudied component of biological communities. However, their roles in structuring ecosystems, their influence on the evolutionary history of host species and their potential applications are slowly being uncovered. The snoek, Thyrsites atun, is a nomadic predator native to the cold coastal waters of the southern Hemisphere. Being a major target of the South African inshore line-fishery, the snoek is a socioeconomically important species whose ecological significance in the southern Benguela should not be underestimated. This study aimed to survey the metazoan parasite community of snoek off South Africa, assess host-parasite relationships and evaluate the potential of parasites as biological tags for stock structure studies. Examination of 210 snoek (FL 411 - 1040 mm) revealed them to be host to 16 parasite taxa. These included 9 new host records (Tentacularia coryphaenae, Caligus coryphaenae, Caligus dakari, Corynosoma australe, Nothobomolochus fradei, Hatschekia conifera, Bolbosoma vasculosum, Rhadinorhynchus cadenati, Digenea sp.) and 4 new locality records (Molicola uncinatus, Pseudoterranova sp., C. dakari, B. vasculosum). A further three cosmopolitan taxa (Anisakis sp., Kudoa thyrsites, Hepatoxylon trichiuri) as well as Caligus zei were also recorded.
Open Access
Temporal and spatial variability in 'Tetracotyle' type and metacercariae infection in the South African sardine, Sardinops sagax
(2013) Weston, Laura Frances; Reed, Cecile C; Van der Lingen, Carl D
Spatial and temporal variation of "tetracotyle" type metacercariae infection in the eyes of the South African sardine, Sardinops sagax, was examined to elucidate the potential use of this parasite as a biological tag, and to test the hypothesis that the sardine population is divided into discrete western and southern subpopulations or stocks. Adult S. sagax specimens of 15 to 22 cm caudal length were collected monthly from five commercial fishery landing harbours to the west (St. Helena and Gans Bay) and to the east (Mossel Bay and Port Elizabeth) of Cape Agulhas in 2011 and 2012. Samples were preserved whole in 70% ethanol, or frozen, and then bagged and labelled. Fish were measured (caudal length in cm), sexed and dissected and summary statistics on the infection by "tetracotyl"e- type metacercariae in their eyes were recorded. Prevalence of infection (%), infection intensity and parasite abundance were analysed seasonally, over a period of 18 months, in fish caught to the west of Cape Agulhas and presumed to be part of the putative western stock of sardine, and in fish caught to the east of Cape Agulhas presumed to be part of the putative southern stock. Generalised linear models were used to model these three indices as dependent on stock, season, year and caudal length, where a binomial distribution was assumed for prevalence and a negative binomial distribution was assumed for infection intensity and parasite abundance. All factors contributed significantly to all models, but it was found that stock was the most significant contributor to the deviance seen in prevalence (%) and parasite abundance, and was the second most important contributor to the deviance seen in infection intensity. Fish to the west of Cape Agulhas were found to have significantly higher parasite loads in comparison to fish from the east of Cape Agulhas (p< 0.001). Season was the second most significant contributor to the deviance seen in prevalence and abundance, and was the most important contributor to the deviance seen in infection intensity, indicating that a seasonal signal was present. This seasonal signal was slightly delayed in fish from the putative southern stock in comparison to those from the putative western stock. Interannual differences in infection rates were also observed, being higher in 2012 compared to 2011. These results suggest that """"tetracotyle- type metacercariae can be used as a biological tag in stock discrimination studies and that, despite temporal variability, the clear spatial difference in the distribution of infection of S. sagax by """"tetracotyle- type metacercariae supports the hypothesis of western and southern stocks of sardine off the coast of South Africa.
Open Access
Temporal variation in infection of male sardine (Sardinops sagax) by a coccidian testicular parasite (Eimeria sardinae)
(2016) Malongweni, Nwabisa; Reed, Cecile C; Van der Lingen, Carl D
Temporal variability in infection of South African male sardines (Sardinops sagax) by a testicular coccidian parasite Eimeria sardinae was examined between putative western and southern stocks of this fish species. Samples were collected by commercial vessels from five localities; Gansbaai, St Helena Bay, Mosselbay, Port Alfred and Port Elizabeth (west and south coast) between 2012 and 2013. A total of 461 sardines were examined for the presence of Eimeria sardinae, including 185 males and 41 females from west coast and 180 males and 55 females from the south coast. Sardine females did not show any infection by the parasite. For males, prevalence of infection was 74.9% for the western stock and 76.5% for the southern stock. Mean infection intensity and standard error of the western stock was 6.7±0.7 and for the southern stock was 8.3±1.0. Parasite abundance and standard error of the western stock was 5.3±0.2 and 6.1±0.3 for the southern stock. A significant difference was observed within testes position (anterior, middle and posterior), with anterior being highly infected followed by middle and posterior (KW chi-square = 86.029, df = 2, p<0.05). Infection from the left and right testes did not show a significant difference (W= 623, p = 0.13). There was no significant difference in prevalence of infection, infection intensity index and abundance index per region across seasons. Seasonal pattern was the same in both stocks. There was a significant difference in monthly average GSI data of male sardines from west and south coast between 1996-2014 (KW = 5416.9, df = 11, p < 0.01). There was no significant difference between seasonal GSI and seasonal infection intensity index.
Open Access
The thermal tolerances and preferences of native fishes in the Cape Floristic Region: towards understanding the effect of climate change on native fish species
(2017) Reizenberg, Jody-Lee; Dallas, Helen Fiona; Shelton, Jeremy Mark; Reed, Cecile C
Global climate change models indicate that a rise in temperature and reduction in rainfall in the Western Cape Province of South Africa is inevitable and unavoidable. Within the Western Cape lies the Cape Floristic Region (CFR); a biodiversity hotspot with high levels of endemism. This includes its freshwater fish assemblage. Whereas the current greatest threats to native fish biodiversity are habitat degradation and invasion by non-native species, predicted climate change is likely to further impact fish communities negatively. As a master abiotic variable in aquatic ecosystems; temperature influences the fitness, behaviour, and life-histories of aquatic biota. Thermal alteration may therefore affect sensitive fish species. The upper thermal limit, determined via the critical thermal method, has been validated as a measure of thermal sensitivity. To better understand the impacts of climate change on the native fish of the CFR, upper thermal limits (critical thermal maxima/CTmax) were determined for seven native species of freshwater fish. Thermal preferences were also determined for five of these species using the acute gradient tank approach to elucidate thermal habitat preferences. Species that were identified by the IUCN as vulnerable, endangered, or critically endangered were selected from the four main families of native fish in the CFR (Anabantidae, Austroglanidae, Cyprinidae, and Galaxiidae), from four Rivers. Overall, Cape galaxias (Galaxias zebratus), Breede River redfin (Pseudobarbus burchelli), Berg River redfin (Pseudobarbus burgi), Clanwilliam redfin (Pseudobarbus calidus), and fiery redfin (Pseudobarbus phlegethon) were found to be most sensitive to increased temperature (CTmax= 29.8-32.7⁰C). Clanwilliam rock-catfish (Austroglanis gilli) and Cape kurper (Sandelia capensis) were found to be moderately sensitive (CTmax= 33.0-35.3⁰C). Similar trends were found using the thermal preference approach as CTmax and thermal preference were found to correlate well. The results were related to in-situ water temperature, which influenced both parameters. Thermal tolerances and preferences of all the native species exceed that of invasive salmonids (Onchorynchus mykiss and Salmo trutta). However, non-native centrarchids (Micropterus spp.) are more thermally tolerant, indicating an increase in threat by warm adapted non-natives. These data suggest that species interactions and distributions are likely to undergo substantial changes in response to elevated water temperature.