Amararatne Yakupitiyage

Replacement of Dietary Fish Oils by Alpha-Linolenic Acid-Rich Oils Lowers Omega 3 Content in Tilapia Flesh

A 20-week feeding trial was conducted to determine whether increasing linolenic acid (18:3n-3) in vegetable oil (VO) based diets would lead to increased tissue deposition of 22:6n-3 in Nile tilapia (Oreochromis niloticus). Five isonitrogenous and isoenergetic diets were supplemented with 3% of either linseed oil (LO), a mixture of linseed oil with refined palm olein oil (PO) (LO–PO 2:1) and a mixture of refined palm olein oil with linseed oil (PO–LO 3:2) or with fish oil (FO) or corn oil (CO) as controls. The PO–LO, LO–PO and LO diets supplied a similar amount of 18:2n-6 (0.5% of diet by dry weight) and 0.5, 0.7 and 1.1% of 18:3n-3, respectively. Increased dietary 18:3n-3 caused commensurate increases in longer-chain n-3 PUFA and decreases in longer-chain n-6 PUFA in the muscle lipids of tilapia. However, the biosynthetic activities of fish fed the LO-based diets were not sufficient to raise the tissue concentrations of 20:5n-3, 22:5n-3 and 22:6n-3 to those of fish fed FO. The study suggests that tilapia (O. niloticus) has a limited capacity to synthesise 20:5n-3 and 22:6n-3 from dietary 18:3n-3. The replacement of FO in the diet of farmed tilapia with vegetable oils could therefore lower tissue concentrations of 20:5n-3 and 22:6n-3, and consequently produce an aquaculture product of lower lipid nutritional value for the consumer.

The need for dietary mineral supplementation for Nile tilapia, Oreochromis niloticus, cultured in a semi-intensive system

Abstract A study was conducted to evaluate the need for dietary mineral supplementation of Nile tilapia cultured under a supplementary feeding regime. Thirty sex-reversed all male Nile tilapia (23g ± 0.7) were stocked in 1 m 3 netcages suspended in an earthen pond fertilized weekly with urea and triple super phosphate at rates of 4 kg N and 1 kg P ha −1 , respectively. The fish were fed experimental diets supplemented with a complete mineral premix (control) and with incomplete mineral premixes in which specific macro (Ca, P, Mg, Na, K) and micro-minerals (Fe, Zn, Mn, I) were omitted from the mineral premix. Among the minerals studied, the addition of phosphorus was found to significantly affect tilapia weight gain, feed conversion ratio, and protein efficiency ratio.

Selection of a commercial feed for Nile tilapia (Oreochromis niloticus)broodfish breeding in a hapa-in-pond system

Abstract A 95-day trial was conducted on a commercial farm in Thailand to compare the performance of three locally available feeds on the seed production of Nile tilapia (Oreochromis niloticus). Three hundred and sixty female Nile tilapia (mean weight±SE, 91.5±2.3 g) with the same numbers of male (123.4±2.1 g) were stocked in each of 12 large nylon hapas suspended in two fertilized earthen ponds. An estimated 16 million eggs and yolk-sac fry were collected from the mouths of incubating females using hand nets at 5-day intervals. Broodfish were fed near to satiation twice daily. The female groups fed with large and small catfish pellets produced 27% and 30% more (P

In situ assay with the midge Kiefferulus calligaster for contamination evaluation in aquatic agro-systems in central Thailand

The aims of this study were to verify the suitability of in situ tests using the tropical midge Kiefferulus calligaster and to evaluate the most sensitive endpoint for the assessment of aquatic pesticide contamination. In situ tests were carried out in freshwater drainage channels (farm channels) that supply vegetable crops and receive considerable pesticide spray drift, and at channels outside farms (main channels). Moreover a pesticide-free farm was used as reference site. The endpoints analysed were: survival of the larvae, body length increment, capsule width increment, cholinesterase activity and glutathione S-transferase activity. Seasonal change was investigated as rainy season and dry season. Deleterious effects were observed at some farms especially during the rainy season when farmers apply heavier doses of pesticides. However, high mortality rates observed in main channels suggest that these water bodies are also affected by other impacts besides pesticide use. This work shows the potential of the in situ assay with K. calligaster as a tool for the environmental quality assessment of tropical aquatic ecosystems.

The microbiological and sensory quality of septage-raised Nile tilapia (Oreochromis niloticus)

Abstract Septage is widely used in aquaculture, especially in developing countries where artificial fertilisers and feeds are expensive. Previous studies in this field have concentrated on the microbiological quality of the fish at harvest, and the physiological effects on the fish. No work to date has investigated the implications of septage-use on the sensory and microbiological quality of fish during post-harvest storage. Tilapia ( Oreochromis niloticus ) were cultured in three levels of septage (0, 150 and 300 kg COD/ha/day); fish in the 0 kg COD/ha/day pond were fed with commercial pellets. The quality of the water was monitored during the growth of the fish. At harvest, fish were assessed for microbiological quality, growth characteristics, proximate composition, and sensory quality. Fish were then stored on ice and their microbiological and sensory quality monitored at 3-day intervals until rejected by the taste panel. Data indicated that the use of septage influenced the quality of the water, with more faecal organisms isolated from septage-fed ponds. More faecal organisms were also isolated from fish from these ponds. Growth and proximate analysis data indicated that the septage-fed fish were smaller, and contained less fat, than pellet-fed (control) fish. These data also indicated that tilapia will survive and grow where septage is the only added source of nutrient. Fish quality data indicated that there was a preference for the flavour of the septage-fed fish at harvest, but that this difference did not persist. There were no consistent significant differences between sensory scores for control and septage-fed samples during the storage period. There was no evidence that the use of septage had influenced either the microbiological or the sensory quality of the fish samples during iced storage.

Effectiveness of Marine Protected Areas in Managing the Drivers of Ecosystem Change: A Case of Mnazi Bay Marine Park, Tanzania

Marine protected areas (MPAs) are being promoted in Tanzania to mitigate the drivers of ecosystem change such as overfishing and other anthropogenic impacts on marine resources. The effectiveness of MPAs in managing those drivers was assessed in three ecological zones, seafront, mangrove, and riverine of Mnazi Bay Marine Park, using Participatory Community Analysis techniques, questionnaire survey, checklist and fishery resource assessment methods. Eleven major drivers of ecosystem change were identified. Resource dependence had a major effect in all ecological zones of the park. The results indicated that the park’s legislations/regulations, management procedures, and conservation efforts are reasonably effective in managing its resources. The positive signs accrued from conservation efforts have been realized by the communities in terms of increased catch/income, awareness and compliance. However, some natural and anthropogenic drivers continued to threaten the park’s sustainability. Furthermore, implementation of resource use and benefit sharing mechanisms still remained a considerable challenge to be addressed.

Use of Yeast-Fermented Canola Meal to Replace Fishmeal in the Diet of Asian Sea Bass Lates Calcarifer (Bloch, 1790)

Fishmeal is a significant protein source for aquatic feed, especially for carnivorous fish. Currently, the price of fishmeal is increasing, also it is mentioned as a competition of human food fish. Replacing fishmeal by other protein sources is therefore an important target. This study tested yeast-fermented canola meal in the diet of Asian sea bass, Lates calcarifer to determine its effects on growth, feed acceptance, feed utilization, nutrient digestibility, body proximate, minerals and their utilization. Diets consisted of a 35% fishmeal base (control) and four diets in which fishmeal protein was replaced by yeast-fermented canola meal at levels of 25, 50, 75 and 100%. For each diet, three groups of fish with an initial weight of 5 g were fed to satiation twice a day for 60 days. Feed intakes and survival rates of test fish fed the diets with up to 50% replacement were not significantly different (P > 0.05). Fish fed the diet with 100% replacement rejected the feed and all died within two weeks. Fish fed the diet in which 75% of fishmeal protein replacement had lower final mean weight, daily weight gain, protein efficiency ratio, nutrient digestibility and higher feed conversion ratio (P < 0.01) than fish fed the control, 25% and 50% replacement diets. Increasing the protein replacement level lowered body crude protein, ash, Ca, Mg, P and their utilization of Asian sea bass (P < 0.05). This seemed to relate to increasing dietary phytic acid as the inclusion level of yeast-fermented canola meal increased. It was concluded that 50% of fishmeal in the diet of Asian sea bass could be replaced by yeast-fermented canola meal without overall impact on growth. This study also showed the possibility of < 10% dietary fishmeal for this species since fish accepted a diet containing only 8.75% fishmeal.

Coastal debris analysis in beaches of Chonburi Province, eastern of Thailand as implications for coastal conservation

This study quantified coastal debris along 3 beaches (Angsila, Bangsaen, Samaesarn) in eastern coast of Thailand. Debris samples were collected from lower and upper strata of these beaches during wet and dry seasons. The results showed that Bangsaen had the highest average debris density (15.5m-2) followed by Samaesarn (8.10m-2), and Angsila (5.54m-2). Among the 12 debris categories, the most abundant debris type was plastics (>45% of the total debris) in all beach locations. Coastal debris distribution was related to economic activities in the vicinity. Fishery and shell-fish aquaculture activities were primary sources of debris in Angsila while tourism activities were main sources in Bangsaen and Samaesarn. Site-specific pollution control mechanisms (environmental awareness, reuse and recycling) are recommended to reduce public littering. Management actions in Angsila should focus on fishery and shell-fish culture practices, while Bangsaen and Samaesarn should be directed toward leisure activities promoting waste management.

Effects of microplastics on sessile invertebrates in the eastern coast of Thailand: An approach to coastal zone conservation

This study assessed the microplastic contamination of 3 most abundant sessile and intertidal invertebrates (Rock Oyster: Saccostrea forskalii, Striped Barnacle: Balanus amphitrite, Periwinkle: Littoraria sp.) in 3 beaches of the eastern coasts of Thailand. The results showed a significant accumulation of microplastics in the invertebrates at rates of 0.2-0.6 counts/g indicating higher pollution levels along the coastline. Filter feeding organisms showed comparatively higher accumulation rates of microplastics. Thus, contaminated bivalves pose potential health risks for seafood consumers. The plastic pollutant prevalence in sessile and intertidal communities was corresponded with pollution characteristics of contaminated beach habitats where they live. Thus, bivalves, gastropods and barnacles can be used as indicators for contamination of microplastics in the areas. This study also demonstrated the need for controlling plastic pollution in Thai coastal areas.