Genetic Approaches To The Analysis of Body Colouration in Nile Tilapia (Oreochromis niloticus)

Body colouration in tilapia is an important trait affecting consumer preference. In the Nile tilapia (Oreochromis niloticus), there are three colour variants which are normal (wild type), red and blond. In some countries, the red variant is important and reaches higher prices in the market. However, one major problem regarding red tilapia culture is their body colouration which is often associated with blotching (mainly black but also red) which is undesirable for the consumer. The overall aim of this work was to expand knowledge on various aspects of body colouration in Nile tilapia using genetic approaches. The results of this research are presented as four different manuscripts. The manuscripts (here referred as Papers) have either been published (Paper IV) or are to be submitted (Paper I, II and III) in relevant peer reviewed journals. Paper I and II investigated the inheritance of black blotching and other body colour components of the red body colour. Specifically, Paper I consisted of two preliminary trials (Trial 1 and 2), to look at the ontogeny of black blotching and body colour components over a period of six months. Trial 1 investigated the effect of tank background colour (light vs dark) on black blotching and other body colour components and was carried out using a fully inbred (all female) clonal red line. Trial 2 was carried out using mixed sex fish and was aimed to investigate the association of black blotching with the sex of the fish. The results from this study were used to guide the experiment described in Paper II. Sixteen red sires with various levels of black and red blotching were crossed to clonal females and the inheritance of blotching and other body colour components were investigated using parent-offspring regressions. The results showed no significant heritability for black blotching and body redness, but a significant correlation for body redness and black blotching was found in female offspring at one sampling point suggesting that attempts to increase body redness may increase black blotching, as had been hypothesized. Paper III was divided into two parts. The first objective was to map the blond locus onto the tilapia linkage map and the second was to investigate the interaction of the blond and red genes on black blotching using the blond-linked markers to distinguish different blond genotypes in heterozygous red fish (i.e. RrBlbl or Rrblbl). In the blond fish, the formation of melanin is almost blocked via much reduced melanophores and this feature may be able to help reducing the black blotching in red tilapia. Two intraspecific families (O. niloticus) and one interspecific family (O. aureus and O. niloticus) were used as mapping families and the blond locus was located in LG5. Four out of eight markers were successfully used to assess the interaction of blond on red blotched fish. The blond gene did not significantly reduce the area of blotching but did reduce the saturation (paler blotching) and enhanced the redness of body colour in the Rrblbl fish compared to the RrBlbl group. Finally, Paper IV aimed to find out the effect of male colouration on reproductive success in Nile tilapia. A choice of one wild type male and one red male was presented to red or wild type females and these fish were allowed to spawn under semi-natural spawning conditions. Eggs were collected from the female’s mouth after spawning and paternity was assessed using microsatellite genotyping and phenotype scoring. No significant departures from equal mating success were observed between the red and wild type males, however there was a significant difference between the red and wild type females in the frequency of secondary paternal contribution to egg batches. The results suggest that mating success of wild type and red tilapia is approximately equal. The results from this research help to broaden our knowledge and understanding on the aspects of body colouration in Nile tilapia and provide fundamental information for further research

Linkage mapping of the blond locus in Nile tilapia (Oreochromis niloticus L.) and preliminary analysis of its effect on blotching in red Nile tilapia

Black blotching of the skin in red tilapia is undesired by tilapia producers since it affects their marketability. This study was carried out with the aims of mapping the blond locus and testing whether the homozygous recessive blond gene reduces or removes blotching in red tilapia by studying the interaction between the red and blond genes. Two types of mapping families (two intraspecific and one interspecific) were used for the mapping of the blond locus. Genome-wide mapping using microsatellites was first carried out to identify molecular markers that were linked to the blond locus. The locus was mapped in linkage group (LG) 5 in an interval that varied between 7.5 and 20.8 cM, depending on the tested family. In the intraspecific families the blond locus was closely linked to the microsatellites UNH309, UNH169 and GM017 (P < 10- 11), while in the interspecific family microsatellite GM636 (P < 10- 8) was also found to be significantly associated, in addition to the above three microsatellites. Linked markers were used to identify the genotype of individual fish for the blond and red loci from the specifically designed crosses so the effect of recessive blond gene on blotched fish could be assessed. The underlying blond trait did not significantly reduce the area of blotching but did reduce the saturation (paler blotching) and enhanced the redness of body colour in the homozygous blond fish compared to the heterozygous (wild type) group

Status and trends in coastal fishery resources of Sarawak, Malaysia - a focus on tropical deltaic estuary

The sustainable use of fisheries resources is a major concern for coastal resource management. Malaysia is endowed with vast coastal fisheries resources which contribute about 1% to national GDP. Sarawak is the major state of Malaysia having high potentials for coastal fisheries. This study was conducted from December 2018 to May 2019 to inquire the status of the coastal fisheries and to identify gaps for further research and measures for sustainable fisheries. The study was undertaken through desk-based review and analysis of secondary data along with a focus on the primary fish landing data collected directly from fishers’ catches and Gnian (type of Estuarine Set Bag Net-ESBN) fish sampling. FAO production data (1950-2011) for fishing zone 71 (data of Sarawak-Sabah fishing zone) showed a sharp incremental trend (70100 to 682004 MT; R = 0.992). According to DoF data from 2000 to 2016, the Sarawak fishery was mainly contributed by coastal catches which is about 70% of the total catch, and a clear monthly fluctuation was observed in fish catches from Sarawak coast. In the same dataset (DoF 2000-2016), there was constant landing from March to August whereas declining trends from September to February. Data from case study site (Daro) exhibited 40.9 MT catch in 2018 and varied every month from the lowest 3004 kg (November) to the highest 3693 kg (March). Fishing efforts in terms of fishermen, vessels and gears were steadily increased over the period of year 2000 until 2016. The main contributing species/groups by weight were prawn and shrimp (39%) followed by Bornean grenadier anchovy (15%), and eeltail catfish, crabs and Gangetic anchovy (4%). There were 78 contributing species/group/guilds including fresh water, estuarine and coastal fishes showed in historic database of Daro via the catch assessment forms. However, there were only 34 species found to be contributing to catch during 2018. Out of 34 species, 23 were found contributing regularly (12 months) whereas the other 11 species were found contributing seasonally to catch. The study during surveys in Daro in April 2019 discovered 27 species. The ecological variation in seasonal pattern might be the driving factor for these species contributing variation to catch

Green aquaponic system: a project to generate community income

Aquaponics is a combination of Aquaculture and Hydroponics in a recirculating aquaculture system (RAS). Waste from fish tanks were pumped into plant growing beds and then filtered out by the plants as nutrients, after which the cleaned water is recirculated back into the fish tanks. This project is an extension project which was conducted from 2008 to 2010. It is a collaborative project between Institute of Tropical Aquaculture (AQUATROP) Universiti Malaysia Terengganu, Terengganu Department of Fisheries, Agriculture Department, a local company W.H.K Integrated Sdn Bhd and the Committee of KRT Telaga Batin. The project is currently being maintained by Committee of KRT Telaga Batin. The fish cultured was catfish (Clarias gariepinus) and vegetables grown were Chinese mustard and lettuce. In the project, 3-4” catfish fingerlings were cultured until market size that is after 4 months and the vegetables took 30-35 days before being harvested. In this current project, tilapia (Oreochromis niloticus) will be cultured with combination of Chinese mustard and lettuce because tilapia will fetch a higher price (RM8-10/kg) compared to catfish (RM3.50-5/kg). This project will be conducted by one intern graduate student and final year project students. The final year project students will be involved in the monitoring and collecting data of the water quality, plant and fish growth and hydraulics. Aquaponic system at Kg. Telaga Batin consist of four fiberglass fish tanks (1.8 L x 1. 8 W x 0.92 H m) and 24 plant growing beds (1.8 L x 0.61 W x 0.2 H m). Plants grown in the green house of size 6.1 L x 9.2 W m. An air-lift system is used to distribute the water from fish tank to the growing bed using the pressure from the blower