Methods
Data acquisition and
processing
We retrieved occurrence records from two fish classes (Actinopterygii
and Sarcopterygi) in Ugandan water bodies from GBIF online data
repository (GBIF 2020). We used the occ_download_get function
in rgbif package to retrieve data (Chamberlain et al. 2020).
Except for genera Astatoreochromis and Pseudocrenilabrus , we
changed all other haplochromine cichlids genera to Haplochromisto conform with FishBase nomenclature (Froese & Pauly 2019), which is
based on Oijen (1996). Thus, names such as Astatotilapia nubilawere changed to Haplochromis nubilus ; Schubotzia
eduardiana to H. eduardianus ; and Astatotilapia pallida
to H. pallidus . Occurrences that were outside the geographic
range described in FishBase, and whose identity could not be verified
based on recent survey data, were discarded. We also excluded all
occurrences without complete scientific names (genus and specific
epithet), e.g., Haplochromis sp. and Oreochromis sp.
Occurrences with unknown and incorrect water bodies were excluded, e.g.,
all records of H. eduardii that were recorded in Lake Albert in
the GBIF datasets were discarded, as the species is endemic to Lake
Edward (Froese & Pauly 2019). For occurrence records without a named
waterbody of origin but with coordinates were determined based on the
GPS coordinates. We used habitat descriptions, verbatim locality, and
location remarks to identify the waterbody of origin. We also discarded
all occurrences from manmade water bodies, such as ponds, tanks, and
aquarium. Lakes Salisbury and Kasudho were changed to Bisina and Kasodo,
respectively, to conform to the current names and avoid duplication of
records for the same lakes. We categorized lakes <200
km2 as small lakes and
>200km2 as large lakes, resulting in 7
large and 37 small lakes (Appendix S1 and S2). After preliminary
processing of the data, a total of 14,452 occurrences records were
retained for further analysis.
Conservation priority index
formulation
We retrieved the conservation status of each species from the
International Union for Conservation of Nature (IUCN) Redlist database
(www.iucnredlist.org/). The species are classified as data deficient
(DD), least concern (LC), critically endangered (CR), near threatened
(NT), endangered (EN), and not evaluated (NE) (IUCN 2012). We used
waterbody surface area, species richness, IUCN statuses, rarity, and
scaling constant to develop the conservation priority index (CPIw),
based on the formula:
\begin{equation}
\mathrm{CPIw\ =}\ \frac{\sum_{\mathrm{i\ =\ 1}}^{\mathrm{n}}{\mathrm{\text{Cwt}}_{\mathrm{i}}\mathrm{\text{.\ R}}_{\mathrm{i}}}}{\mathrm{(Aw\ .\ 7)}}\nonumber \\
\end{equation}where, for species i per unit surface area of a waterbody,
Cwti is the species weight based on its IUCN status
(i.e., CR (5), EN (4), VU (3), NT (2), LC (1)); n is the number of
species in a particular waterbody; Aw is the total surface area of the
lake, and Ri is the frequency of occurrence of a species in the water
bodies (i.e., if a species occurred in one waterbody, then a weight of 5
was assigned, 2-3 water bodies (weight 4), 4-5 water bodies (weight 3),
6-10 water bodies (weight 2), and >10 water bodies (weight
1)). The value 7 is a scaling constant, indicating the total number of
IUCN categories (IUCN, 2012). Note that fish species that were
registered as NE and DD in the IUCN database were assigned a
Cwti of 5 on the basis that such species can go extinct
unnoticed and, therefore, should be considered in the same category as
CR species (IUCN 2012). The surface area for each lake was obtained from
the literature (Burgis & Symoens 1987; Vanden Bossche & Bernacsek
1990; Ogutu-Ohwayo et al. 1999; Schofield & Chapman 1999; Olowo et al.
2004). We used Google Earth to approximate the surface area for lakes
Gawa, Kabaleka, Wamala, Nakabale, Owapet, Kirimira, and Kabaka because
it was not found in the literature. The surface area of Lakes Natuali,
Chankaranga, Okurachere, Kasunju, Nkuruba, and Mutabyo could not be
determined from both literature and Google Earth, and thus we could not
calculate their CPIw values.