Fishes of the Salonga National Park ( Congo basin , central Africa ) : A list of species collected in the Luilaka , Salonga

distribution of fishes throughout central Africa (Stiassny et al. 2011) provides useful comparative data. That IUCN assessment compiled point data from legacy collections housed in major museums (Darwell and Smith 2011), and in particular the large historical holdings of fishes from collections made around Mbandaka, Boende, and Ikela (Figure 1) housed at the Africa Museum, Tervuren, and these provide the best available comparative data for fishes in the vicinity of the SNP.


Introduction
Created by presidential decree in 1970, the Salonga National Park (SNP) is the largest tropical rainforest preserve in Africa (UNESCO 2012).Covering an area of ca.36,000 km2 , the SNP is entirely located within the sedimentary "cuvette centrale" of the Congo basin (Evrard 1968), where it is divided into two large forest blocks, each delimited by major waterways (Figure 1).Most of the park is situated about 300 meters above sea level with moreor-less continuous low relief cut by broad, meandering rivers with extensive seasonally flooded, or permanently inundated, riparian zones.The climate is equatorial, hot and humid, with an average annual temperature of 25.5°C, and rainfall of around 1800-2200 mm per year (Hughes and Hughes 1992).The densely forested landscape (Figure 2A) encompasses a large and complex aquatic network that traverses much of the terrestrial area of the park.Despite the high importance of the region's fishes for food security and to the local economy, most of the SNP remains remarkably poorly documented ichthyologically.This is undoubtedly a serious impediment for fisheries management in the region, where increasing fishing pressure, and the use of highly destructive fishing techniques is of growing concern both outside and inside the park's boundaries (Inogwabini 2005;pers obs.).
For fishes, a single reference (Inogwabini 2005) reports on 56 species collected at two sites in the SNP; one in the northern block at Etate on the Salonga River, and the second in the southern block at Lokofa on the Luilaka River.Historical literature for the area is equally sparse.Matthes (1964) reported on a series of collections from around Ikela (a settlement on the Tshuapa River some 270 km west of Etate; Figure 1) and that work remains the primary published reference for the entire region.However, a recent assessment of the status and Abstract: A list of fishes collected in and around the periphery of the Salonga National Park in Equateur Province of the Democratic Republic of Congo is provided.While noteworthy for a wide array of rare and endangered terrestrial vertebrates, the fish fauna of the Salonga National Park, the largest protected area in Africa, is very poorly known.One hundred and fifty two species distributed in 24 families are reported on here; of which 9 represent putatively undescribed taxa currently under investigation.Lack of up-to-date taxonomic and distributional knowledge of African fishes is particularly acute in the central Congo basin and the present report, while undoubtedly incomplete, provides a foundation for much needed further work in the region.York with a database accessible at http://entheros.amnh.org/db/emuwebamnh/.

Notes on Collection Sites
Sampled sites share similar physical characteristics, being situated along the banks of the heavily forested Salonga, Yenge, and Luilaka Rivers, with most in seemingly pristine condition.The waters of all three rivers are tea-colored, highly humic, and notably acidic, with low dissolved oxygen and conductivity (Table 2).The Luilaka River, which delimits the northern boundary of the SNP southern block, has an average width of 45 m, varying from 30-60 m between Ifumu (Site 1) and Ikala (Site 9).Depths at collection sites range between 2-10 m (depending on season), the substrate is predominately fine mud, sand, and detritus, with strong flow in the main channel, particularly during the dry season when waters are restricted within the river channel.At its maximum extent, the zone of inundation rarely reaches more than 100 m into the forest on either side of the main channel.The Salonga River has an average width of 60 m, but varies from 40-80 m between Etate (Site 14) and Bomputu (Site 15).Depths at collection sites varies from 3-11 m (depending on season), again with water flow strongest in the main channel during the dry season.The substrate consists primarily of sand, fine mud and detritus, with many large sand bars exposed in the dry season.During the height of the rainy season a zone of inundation of about 100 m extends into the forests on either side of the main channel.The Yenge River, a large left bank tributary of the Salonga, is located entirely within the SNP.Although the smallest of the three rivers sampled in terms of channel width, the zone of inundation of the Yenge is by far the greatest, with waters reaching upwards of 400 m into the forest during the height of the rains.Site 3 (Boangi, Figure 2C), Site 11 (Efofa, Figure 2F), and Site 15 (Bomputu, Figure 2H) are located near village docks, with evidence of forest clearing (mainly for housing and fishing hut construction), and with grassy banks replacing riparian vegetation.

Fish sampling
Standard fishing techniques were employed (Lang and Baldwin 1996), and included deployment of monofilament gill nets, traps, dip nets, cast nets, hook and line, and locally made barrage traps (Figure 2H).Additional specimens were purchased from fishermen along the river and at village markets.
Taxonomic nomenclature used herein is based primarily on Eschmeyer ( 2012

Results and Discussion
A total of 2582 individuals belonging to 152 species, distributed in 24 families and 8 orders are represented in Table 2, with their distribution among sites indicated in columns 1-15.In column 16, distribution data from an IUCN assessment of the status and distribution of central African fishes (Brooks et al. 2011) are used to indicate which SNP species have previously been known to occur in the vicinity of the park.While comparative data are minimal for the rivers of the SNP itself, Brooks et al. (2011) do provide data on the region's fishes, mostly with historical records from around Mbandaka on the Ruki River, and Boende and Ikela on the Tshuapa River, thereby providing the best available comparison for the SNP list provided here.
Based on these data we recognize 33 species that have not previously been recorded from the central cuvette of the Congo basin (exclusive of the main channel of the Congo River), or are known only from isolated regions distant from the rivers of the SNP.Most of these species (Table 3, column 16) represent range extensions within the Congo basin, and a selection of them is illustrated in Figures 3-5.While the present study has significantly increased the number of species known to occur within the boundaries of the SNP, with few exceptions, the species reported on here are widespread in the region and many occur throughout much of the rain forested central Congo basin.Regional endemism is seemingly low, possibly due to the extent of currently interconnected, and densely forested habitat throughout most of the cuvette (Chapman 2001), or as a result of repeated climatic shifts resulting in fluctuating forest contraction and expansion since the Middle Pleistocene (Campbell 2005).Despite the predominance of widespread species in our collections, a number of specimens collected during the course of the present study are not assignable to currently described taxa, and appear to represent undescribed species, indicating that significant regional endemism may remain to be discovered.A selection of these is illustrated in Figures 6-7, and includes a specimen of psammophilous, dorso-ventrally depressed, and depigmented clarioteid catfish (Figure 6A), that belongs to a new genus endemic to the Congo basin (Sullivan, pers.comm.).It is noteworthy that, with the exception of the Alestopetersius (Figure 6B) and Eugnathichthys (Figure 6C) species, most of the specimens unassignable to known species are of small size (Figure 7), and were collected in marginal habitats rather than in the main river channels.As noted previously, most collecting effort was focused in the main river channels and sampling in the many small affluent streams, black water swamps, and peripheral habitats was minimal.Therefore, while the present study represents the best available tally for the SNP and its immediate vicinity, targeted collecting in these marginal habitats will be necessary to provide a fully comprehensive listing for the park, and an accurate assessment of the actual levels of endemism in the region.

FishesFigure 1 .
Figure 1.The Salonga National Park (shaded grey) and associated drainages in Central Africa, with the locations of Sites 1-15 indicated.

Table 2 .
Water chemistry data.