Evaluating the trophic ecology and feeding habits of three divergent lineages of Sandelia bainsii (Teleostei: Anabantidae), from the Eastern Cape Rivers using stable isotope analysis
- Authors: Nkomo, Thulisile
- Date: 2022-10-14
- Subjects: Anabantidae , Trophic ecology , Food chains (Ecology) , Food web , Freshwater fishes Food , Stable isotopes
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/364984 , vital:65667
- Description: Despite supporting a disproportionately large fraction of the global biodiversity, freshwater ecosystems are ranked as the most highly threatened habitats on the planet, ahead of both terrestrial and marine ecosystems. Many regions are still characterised by limited knowledge regarding the taxonomy and ecology of freshwater fish taxa. The need for ecological information is increasingly becoming important due to the discovery of new species and unique lineages, which require conservation management. The aim of this study was thus to evaluate the trophic ecology and feeding habits of the three recently described and divergent Sandelia bainsii lineages, namely Sandelia sp. ‘bainsii Kowie’ from the Great Fish River, Sandelia sp. ‘bainsii Keiskamma’ found in the Keiskamma River, and Sandelia sp. ‘bainsii Buffalo’ confined to the Buffalo River system in the Amathole-Winterberg freshwater ecoregion in the Eastern Cape Province, South Africa. Based on the allopatric distribution and the generalist feeding habits of these lineages, this thesis postulated that these three lineages were likely to show similar trophic ecology patterns, different dietary composition and as a result would have variable trophic positioning in the different river systems. Therefore, the primary objectives were to use stable isotope analysis to (1) evaluate the food web patterns of the river systems where the three S. bainsii lineages occurred, and (2) determine dietary source contributions for the three lineages using isotope mixing models. The results revealed general variability and significant differences in the δ13C and δ¹⁵N values for the different basal resources, macroinvertebrates and fish community across the different headwater streams. Within and across the different rivers, the S. bainsii lineages exhibited variable isotopic niche sizes, which appeared to coincide with the variation in the isotopic composition of the individual communities. Furthermore, these lineages did not exhibit any discernible patterns in their interspecific interactions in different habitats. This suggests that these lineages’ isotopic niche patterns were largely influenced by spatial differences in both trophic resources and probable interactions with contraspecifics. Assessment of trophic positions of S. bainsii lineages showed that the three lineages had higher trophic positions than other co-occurring species at most sites, except in the Buffalo River. This suggest that the different lineages were generally top predators in the different river systems. Although S. ‘bainsii Buffalo’ had a lower trophic position compared to other co-occurring species, its trophic position was generally characterised by high uncertainty, indicating that this lineage was likely influenced by the occurrence of diet sources that had highly variable stable isotope values. Findings from stable isotope mixing models revealed that the diet sources varied from the dominance of either single diet source in the Fairburn and Tyume 1 River to the importance of multiple prey sources from the Lushington and Kat River system. This suggests that despite being a top predator at most sites, the diet sources for the different lineages were highly variable. The patterns observed in this study did not appear to be attributed to species divergence possibly caused by allopatric speciation, but rather differences in food web characteristics of the river systems, as well as the lineages interspecific relationships and their generalized feeding strategies. Understanding the trophic dynamics of these lineages will assist in implementing effective conservation strategies and policies dealing with narrowly distributed species that are threatened by habitat fragmentation and invasion of piscivorous fish. , Thesis (MSc) -- Faculty of Science, Ichthyology and Fisheries Science, 2022
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- Date Issued: 2022-10-14
Some aspects of the ecology of the Eastern Cape rocky Sandelia Bainsii (Pisces : Anabantidae) in the Tyume River, Eastern Cape, South Africa
- Authors: Mayekiso, Monde
- Date: 1986
- Subjects: Anabantidae , Perciformes , Labyrinth fishes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5196 , http://hdl.handle.net/10962/d1001972 , Anabantidae , Perciformes , Labyrinth fishes
- Description: This is an account of some aspects of the ecology of the eastern Cape rocky, Sandelia bainsii Castelnau in the Tyume river in the eastern Cape. Previous unpublished work carried out by the Zoology Department of the University of Fort Hare in the mid-seventies indicated that the species was rare in the Tyume river. Because of its uncertain conservation status, its restricted geographic distribution and the lack of information on its biology, demography, feeding and reproductive biology were studied. The species occurs in the upper, middle and lower reaches of the Tyume river and is common in rocky , shallow habitats in the middle reaches of the system. The most important threats to the survival of S. bainsii appear to be habitat alteration and alien species. The presence of these threats and the small size of the population suggest that the species may be vulnerable to local extinction. As the total range of the species extends to only a few rivers in the eastern Cape, the species might face extinction if these threats are faced throughout its range. A detailed study on the autecology of S. bainsii was therefore carried out in order to provide a basis for rational conservation and management of the remaining populations of the species.The age structure and the growth rate of S. bainsii was determined using checks on scales and otoliths. Males grow faster and reach a larger size than females. The maximum length of S. bainsii is compared to that of other anabantids. The longevity of males is 5 years and that of females 3 years. Food preferences were determined by three different methods and the indices of relative importance of food items calculated for different length groups and seasons. S. bainsii was found to be an euryphagous and opportunistic predator whose diet consists largely of insects. A considerable overlap was found between the diet of S. bainsii and that of the two alien species, Salmo gairdneri and Micropterus salmoides which indicates a possibility of competition for food. Mark and recapture experiments showed that S. bainsii is a "sedentary " species which is unlikely to be seriously affected by man-made barriers to fish migration, such as weirs. The species reaches maturity during its second growing season (males 80 - 89mm and females 60 - 69mm) and the length at maturity is related to the modal length of males and females. A large proportion of the fish are thus mature at any given time. The fish spawn repeatedly during the summer breeding season, October to February resulting in near continuous recruitment. The possible adaptive value of this habit is discussed. An attempt is made to evaluate the life history style of S. bainsii in terms of the theory of r - and K- selection and altricial and precocial life history styles
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- Date Issued: 1986