A comparison of mangrove and estuarine fish diversity using eDNA metabarcoding and baited remote underwater visual surveys in South Africa and Mozambique
Date
2023-12
Authors
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Publisher
Stellenbosch : Stellenbosch University
Abstract
ENGLISH ABSTRACT: Within estuaries, mangroves and seagrass beds are critical habitats that act as nurseries and
refuge
areas for fishes and provide food for coastal communities. However, in southern Africa, there are
knowledge gaps regarding fish diversity in 1) mangrove ecosystems and 2) under-studied estuarine
bays such as Inhambane Bay, Mozambique. Environmental DNA (eDNA) metabarcoding and baited remote
underwater video systems (BRUVs) are used as complementary tools for biomonitoring as they provide
a better insight into the presence of species and their interactions with the environment. This
project investigates OTU (operational taxonomic unit) and genera richness in South Africa and
Inhambane Bay using eDNA metabarcoding and BRUVs. The aims were to 1) identify whether mangrove
fish diversity varies over a latitudinal gradient, 2) compare genera richness inside and outside
the locally managed marine areas (LMMAs) in Inhambane Bay, and 3) compare the use of complementary
tools BRUVs and eDNA in both sites.
At all study sites, estuarine water was sampled and BRUVs were deployed for an hour. In South
Africa, eDNA recovered 110 OTUs with 58 genera and BRUVs recovered 28 genera with only 12 common
taxa detected using both methods. Fish diversity did not follow a latitudinal gradient in the
mangroves as hypothesized. In Inhambane Bay, eDNA recovered 176 OTUs between the three locations.
For the comparison between methods, 76 genera were recovered by metabarcoding and BRUVs only
recovered 10 genera. There was no significant difference in fish diversity inside and outside the
LMMAs. In both studies, the dual use of BRUVs and eDNA was valuable by detecting species unique to
those methods. The results indicated a need to improve the study design, conduct more research on
estuarine and mangrove fish diversity, and to improve reference databases and fish guides for southern Africa.
AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar.
AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar.
Description
Thesis (MSc)--Stellenbosch University, 2023.