The reproductive biology of warty sea cucumber, Neostichopus grammatus Clark (Holothuroidea: Echinodermata) under natural and integrated multi-trophic aquaculture (IMTA) conditions in the Eastern Cape Province, South Africa
- Authors: Senekal, Heleen Ester
- Date: 2024-10-11
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/464451 , vital:76512
- Description: This study investigated the reproductive cycle of the warty sea cucumber, Neostichopus grammatus, in the wild and in a farming environment, to test its suitability for co-culture with abalone Haliotis midae in an IMTA system. The research formed part of a broader EU H2020 program, Aquavitae, and was conducted at Wild Coast Abalone in South Africa. The study investigated several environmental parameters, such as temperature, day length, and substrate, to determine if these have any effects on the gonadal development and reproductive cycle. The natural gametogenic cycle of wild warty sea cucumbers was determined by monitoring the Gonadosomatic Index (GI) values monthly for a period of 16 months. The GI index was validated by means of other maturity assessment techniques including measurement of the size and colour of the gonads, oocyte diameter measurements and gonad histology sections. Wild collected sea cucumbers were maintained in abalone farm rearing tanks on a diet of abalone feed and faecal waste for a period of 10 months, with GI values being determined monthly. The wild and farmed sea cucumber GI data was correlated with environmental parameters. Seasonal water temperature was strongly correlated with the GI values of wild warty sea cucumbers, suggesting that water temperature likely influences gonadal development. Sea cucumbers matured sexually during colder months (May to September) and spawned from September to February, during summer. The results of oocyte measurements, macroscopic and microscopic analyses, and histological analyses in combination with the GI values, provides a practical indicator of sexual maturity for captive breeding purposes. Farmed warty sea cucumbers followed the same annual reproductive cycle as wild sea cucumbers, however they came into spawning condition approximately one month later than wild conspecifics. As the farm water temperature was significantly higher than the ambient ocean water temperature, it was hypothesised that this may have affected the gonadal development of the farmed sea cucumbers. Furthermore, the farm-reared sea cucumbers lost weight and condition, indicating a nutritional deficiency. Previous studies indicated that the presence of a sand sediment facilitated the assimilation of organic detrital matter by sea cucumbers. An additional trial was thus set up to determine the effect of a sand sediment and cooler ambient temperature on the growth and gonadal development of the warty sea cucumbers. The growth and GI values of sea cucumbers in the cool water treatment did not differ significantly from the ambient temperature control groups. However, the addition of a sand substrate to the sea cucumber tanks had a significant positive growth effect on sea cucumber body mass and GI values. Sea cucumbers fed a diet of abalone waste material on the sand substrate exhibited final average GI values of 2.99 % (SE ±0.56). In contrast, sea cucumbers kept in bare tanks and only received abalone waste as food had significantly lower average GI values of 1.36 % (SE±0.2). This suggests that the provision of a sand sustrate in sea cucumber rearing containers is essential for the adequate nutrition and gonadal development. The results of this study indicate that the warty sea cucumber is a promising candidate for inlcusion in an IMTA system with South African perlemoen abalone. , Thesis (MSc) -- Faculty of Science, Ichthyology and Fisheries Science, 2024
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The effect of Gracilaria gracilis (Rhodophyta) on growth and behaviour of farmed abalone Haliotis midae when included in the abalone diet
- Authors: Madlala, Njabulo Praiseworth
- Date: 2024-04-04
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/435332 , vital:73148
- Description: Abalone feed naturally on algae, but commercial abalone farms rely on formulated feed. The inclusion of algae with the formulated feed in the diet improves growth, health and feed conversion ratio (FCR). However, the kelp that is currently included in the feed is wild harvested and this resource is limited and under increasing pressure. Thus, there is a need to develop an alternative sustainable source of algae. The aim was to use Gracilaria gracilis algae (that was produced with mussel in an integrated multitrophic aquaculture system; IMTA) which was then included into abalone feeds and its influence on abalone growth, FCR and behaviour was evaluated. Sea-based G. gracilis was harvested off an existing IMTA system, manufactured into Abfeed® and fed to abalone to determine growth efficiency. Abalone (30 - 40 g abalone-1) originated from the same cohort at Whale Rock Abalone Farm (Pty) Ltd., Hermanus. Abalone were fed either: Abfeed® S34 only with no algae (G0, the control); Abfeed® with sea-based IMTA G. gracilis included in the formulated feed at 0.75 % (G0.75); 1.50 % (G1.50); 3.00 % (G3.00); 6.00 % (G6.00); and 12.00 % (G12.00) inclusion; and Abfeed® S34 with fresh-live G. gracilis (cultured at Whale Rock Abalone Farm (Pty) Ltd.; Gfresh + S34s). Abalone shell length, whole body mass and FCR were measured at a four-months interval over eight months (two growth cycles). Differences in behaviour (i.e., level of activity and feeding activity) were also monitored and comparing between treatments. There was significant difference in mean whole-body mass between treatments (RMANOVA, F(6, 29) = 3.71, p = 0.007). Abalone fed the diet with the highest inclusion of dry G. gracilis (G12.00) had a lower mean whole-body mass value (74.13 ± 2.94 g abalone-1) than abalone from all the other diets after eight months. There was a negative relationship between the condition factor and dry G. gracilis inclusion rate for the first growth cycle (y = - 0.0044x + 1.222, R2 = 0.24, p=0.009) and second-growth cycle (y = - 0.0096x + 1.2233, R2 = 0.51, p = 0.00002). Abalone receiving fresh G. gracilis were less quiescent and more alert on the first hours after food distribution (p < 0.05). The same proportion of abalone with G0, G0.75, and G6.00 G. gracilis inclusion were feeding all along the 9 hours post-feeding. This study will potentially reduce the dependence of abalone farms on wild-harvested kelp in formulated feed. This will improve their contribution to a more environmentally sustainable global production of sea food products, making them more competitive on international markets. , Thesis (MSc) -- Faculty of Science, Ichthyology and Fisheries Science, 2024
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The androgenic and anabolic effects of pine pollen on Nile tilapia (Oreochromis niloticus)
- Authors: Abaho, Ivan
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/431615 , vital:72790
- Description: Access restricted. Expected release date in 2025 , Thesis (PhD) -- Faculty of Science, Ichthyology and Fisheries Science, 2023
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