University of Zululand Faculty of science and agriculture 494030232410 Department of zoology3rd year Research proposal 2019Title:The influence of life stage on habitat selectivity of fish taxa in the Mlalazi Estuary Student: Buthelezi P.S (201602964) Mtshali M.C.G (201639702) Ngcobo Z.H (201759857)Supervisor: MR Q SchutterINTRODUCTION ESTUARINE ENVIRONMENTAn estuary is a semi-enclosed coastal body of water, which either permanently or temporally opens to the sea and within whereby there will be a dilution of seawater with fresh water from the land drainage (Day 1981). Estuaries are considered to be one of the most productive systems in South Africa and play a large role in economic uplift every year increasing. The more studies generated toward estuaries could decrease the destruction by human activity thus increasing the economic value (Lamberth and turpie (2003)).The Mlalazi estuary is said to be a temporally open or closed estuary (DWS.2015). Mlalazi estuary is a Nature Reserve managed by Ezemvelo KZN Wildlife (EKZNW) and it also is known as a pristine estuary. Mlalazi is one of the estuaries that prioritize the need for protection to meet the standard required for national biodiversity plan (Turpie et al., 2012c). Most studies all over the world have shown estuaries as important areas and this may be due to that they have a large impact on both the freshwater and marine biodiversity (Nokane et. al. 2009). They are the nursery for juvenile fish and they have these factors such as high abundance, high growth of organisms, the survival of juvenile fish (Nicola. Estuaries are mostly dominated by the euryhaline organisms this may be due to the relatively inconstant environment, with the fluctuating salinities. They comprise almost 40% of the marine organisms independent of the estuarine environment. Estuarine residing organisms make only 8% (Cyrus.et.al.2015). Most species may be dependent on estuaries only during their juvenile stages and may migrate into the marine or freshwater when big and able to avoid predators (Whitfield 1998). The low water level unable some predators from being able to access the shallow water intertidal pools (Rieucau et.al.2015). There are few piscivores, sheaves and some small juvenile fish like the Terapon jabua that can access these shallow water (Nakane et.al.2010). The understanding of Juvenile early life cycle history of fish may be the key to the conservation management (Thanh et.al.2018)HABITAT CLASSIFICATIONMangroves are trees surviving through tidal wave action and saline environments due to their abilities to release excess salt (Hexham et.al (2004)). The mangrove habitat is a shallow soft-bottom habitat that acts as a nursery to juvenile fish and needs to be protected as it is one of the threatened habitats mostly in the tropic regions and also serves as an important feeding site. The productive and structurally complex environment provided by mangrove stands is used as feeding grounds and refuges by juvenile fishes (Thayer et al., 1987; Ruiz et al., 1993; Laegdsgaard and Johnson, 2001). These trees are by far the support of the species community in estuaries as they can accommodate the migrating and originating species as shelter or nurseries for juveniles due to their abilities to deceive predators with its many root forms. Mangroves, when compared to other habitats, have not yet shown or proven to be the best nursery than others like eelgrass or mudflats (Hexham et.al (2004)). KUSHODA MUDFLAT AND SANDFLATEXPERIMENTAL SPECIES Rhabdosargus holubi species inhabit estuaries and shallow waters over sand and between rocks and the feed on bilvaves, shrimps and crabs (Smith.J and Smith M.1986). Rhabdosargus holubi depend on the structured sheltered environment and also feeding sites provided by an estuary (Nel et al. 2017). In addition in most cases, Rhabdosargus species use the seagrasses habitat as a nursery site. Pomadasys incises is a coastal demersal species that reside in marine habitat and brackish water that is near sandy or muddy substrate with the depth of 10 to 100 (Kapiris et al. 2008). Pomadasy incises is a fish of shallow, nearshore water and from subtropical water.Terapon jabua species is found in coastal waters with sandy substrates and juveniles are common in brackish waters. They come into estuaries during their larvae stage with the flood tide during May and November to feed mostly (Liu et.al.2015). They are usually interspersed among their prey (Kolomann et.al.2017). Adults return to the deep water of about 50 to spawn (Liu et.al.2015). These species feed on ectoparasite, crustacean and increasingly on the whole juvenile fish scales throughout their ontogeny (Kolmann et.al.2017). Gerris Oyena inhabit the bank waters of the middle reach (Thanh et.al.2018) and the coastal estuarine waters of temperate tropic regions (Gray.2019) RESEARCH QUESTIONADD HERE!!!!!!!!!!AIMIs to determine the spatial distribution of marine- estuarine dependent fish and the population structure of each species within Mlalazi estuaryHYPOTHESISALTERNATE HYPOTHESIS (NA)Marine-estuarine dependent fish utilizes the mangrove habitat than mudflat and sand flat habitats.NULL HYPOTHESIS (Nₒ)Marine- estuarine dependent fish reside evenly to mudflat, mangrove and in sand flat habitat.OBJECTIVESThe objective of this project is to compare the abundance, species and the size composition of the marine- estuarine dependent fish taxa.To determine the juvenile recruitment and seasonality of marine-estuarine dependent fish in three sites at Mlalazi estuaryMATERIALS AND METHODSTUDY SITEThis study will be conducted at Mlalazi estuary, Kwazulu Natal, South Africa. Mlalazi estuary is estimated at 42 to 507 km2 and it length is about 40 to 68km. The estuary is situated in the Mlalazi Nature Reserve (Mabaso 2002). The estuary is surrounded by mangrove trees such are Avicennia marina which is the white mangrove, Rhizophora mucronata which is a red mangrove and bruguieria which are the black mangroves. ADD HERE!!!!!!!!!!SamplingTIME FRAMEREFERENCESDepartment of Water & Sanitation (DWS). 2015. Resource Directed MeasuresGray CA .2019. Age determination, growth and mortality of gerris subfasciatus Cuvier, 1830 in Southern Australia. Journal of Applied Ichthyology 35.Huxhama M, Kimani E, Augley J. 2004. Mangrove fish: a comparison of community structure between forested and cleared habitats. Estuarine Coastal and Shelf Science 60: 637-647.Kapiris K, Kallias E, Conides A. 2008. Preliminary biological data on Pomadasys incisus (Osteichthyes: Haemulidae) in the Aegean Sea, Greece. 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