Visit Tanzania II – and the Petrochromis horii species group

A well hidden dive spot in Tanzania is the habitat of Petrochromis sp. “Red” at Lyamembe.  First discovered by Horst Walter Dieckhoff at Luagala Point in Mahale Mountains National Park in 1986-87 (Konings 1988: 42-46; 1998: 50), the fish was rediscovered by the divers of African Diving in April 2002 at the near shore Lyamembe Reef. The reef is located in the centre of Lyamembe Bay, some 30 kilometres (km) south of Luagala Point and has a varying depth ranging from 4-26 metres (m). Due to suboptimal biotope and the quite shallow nature of the reef, P. sp. “Red” is rare at this locality, and adult individuals are quite seldom observed, though juveniles are seen more frequently. For the ornamental fish trade, the fish is collected several hundred metres off shore where deep water reefs are present. P. sp. “Red” is one of the lake’s most challenging fishes to collect due its free-swimming behaviour, large territories/roaming area, and deep water habitat. Second out in the series “Visit Tanzania” is such an off-shore locality called “Lyamembe Offshore Reef” at 6°27'36" S, 29°54'53" E.

Fig. 1. Lyamembe Village.

During a survey in 2007, the area off Lyamembe was searched with an eco-sounder in order to locate the exact coordinates for off-shore reefs. Rumours existed that local fishermen, fishing for food, caught large quantities of P. sp. “Red” with gill nets in deep water. Directed by two such fishermen, we searched the area in early December hoping to find a deep water habitat shallow enough to be able to dive. The day before, we had witnessed the fishermen’s catch of around 50 pieces males of P. sp. “Red” (see picture below). Surprisingly, no females were caught in their net. From the search, only one suitable locality was found: “Lyamembe Offshore Reef” (the given coordinates). This reef is located about 500 m off Lyamembe Bay and has a shallow point of 35 m. Scattered large boulders and rock formations on a white sandy bottom characterize the underwater landscape.  Several adult specimens of P. “Red” were observed in the habitat, both males (see picture below) and females. Also at the reef, a unique colour variant of Cyprichromis microlepidotus feels at home, and the area harbours one of the southernmost populations of Neolamprologus niger. Bright yellow females and pitch-black males are found in the sand beneath larger rocks. Adjacent to Mahale Mountains National Park, the Lyamembe area is inhabited by several unusually large crocodiles. At Lyamembe Offshore Reef, however, crocodiles are rarely seen due to its offshore location. Water cobras have been spotted at the reef, but, while in the water, the snake is friendly and hardly ever strikes, even at the closest encounter.

The small village of Lyamembe in Lyamambe Bay offers great camping possibilities (very friendly villagers) and comfortable accommodations are available in nearby Mahale Mountains National Park with several options (see external links). At TANAPA guest house, it is possible to buy provisions. Before entering the park, it is mandatory to report to the park rangers at the Mabilibili outpost (just 1.5 km north of Lyamambe). Also, permission from the park’s headquarters is required to enter from the south. As there is no phone service in the park, advance arrangements are necessary. Park fees are payable only at Bilenge headquarters in the northern part of the park (some 60 km to the north).

Camping sites southwards are available in the protected bays of Nanga and Makola, just 5 km from Lyamembe. And at the nearby villages Makola and Sibwesa, it is possible to buy basic provisions.

Fig. 2. Petrochromis sp. "Red" and P. ephippium are equally abundant at deep-water habitat of 35-40 m (in the picture, an individual of the latter species is discernible behind the P. sp. "Red"). In shallow water. P. ephippium clearly outnumbers P. sp. "Red" and, in depths less than 15 m, P. sp. "Red" is normally absent. It is expected that in deeper water (>50m), the relationships are the opposite. Pictures captured in December 2007.

Morphologically defined by the appearance of its brush-like jaw teeth, Petrochromis feeds on the unicellular algae attached on epilithic filamentous algae (Yamaoka 1983: 77). There are presently eight described species of Petrochromis, the latest addition to the genus being P. horii. Though, there is disagreement about the status of Petrochromis ephippium, being treated as synonymous with P. trewavasae (Takahashi and Koblmüller 2014). Intentioned as a biological subspecies of P. trewavasae by Brichard (1989: 401), Maréchal and Poll (1991: 373) continuously treat P. ephippium as such. But P. ephippium is sympatric with P. trewavasae at several locations in southern Congo (Konings 1998: 50), and they are distinct in appearance and behaviour, and prefer different types of habitat, which make them very unlikely conspecific. However, there has not been any type specimen of P. ephippium deposited in any museum collections (which after 1999 is mandatory for a name to be validly published), neither is there any clear information on the type locality (which is to be expected in a description) (Brichard 1989: 401). Introduced by Herrmann (1985b: 489), the colourful Petrochromis sp. “Moshi yellow” is very likely conspecific with P. ephippium, as suggested by Karlsson (1998: 34-35, figs., 45). Previous speculation suggested P. sp. “Moshi yellow” to be a possible conspecific to P. sp. “Red” (Konings 1998: 50), based on the fact that variants of P. sp. “Moshi yellow” (syn. P. ephippium) at Sibwesa, Lyamembe, and further north along the coast of Mahale Mountains, exhibit an orange colouration (vs. yellowish or brownish elsewhere). This variant  is also known as P. ephippium “Moshi orange”; and a similar variant of P. ephippium with orange finnage was documented by Staeck (1983: 324-325, fig.). However, P. ephippium is surely and without doubt distinct from P. sp. “Red”, the former being initially reported on by Staeck (1977: 211, 274, fig. top) as similar to P. trewavasae, and observed in the lake at Kigoma and in the border area of Zambia and Tanzania; later on introduced with its specific name by Zadenius (1982: 8) as Petrochromis spec ephippium, seven years prior to its formal description, when it was reported [translated from Swedish]: “In the lake it becomes all yellowish and is instantly observed in its habitat.”

The latest of the congeners is Petrochromis horii. It was discovered by M. Hori at Kasenga, slightly northeast of Mpulungu, around 1996 or earlier (Takahashi and Koblmüller 2014). During its discovery it was considered being “similar to P. fasciolatus in body colouration and stripe pattern but did not have a protruding lower jaw... “ (Takahashi and Koblmüller 2014) This observation is similar to Herrmann’s (1985b: 490) statement on the similarities between P. fasciolatus and P. sp. “Gold” [translated from German]: “...at a first look it is very similar to P. fasciolatus, regarding body shape and colouration...[but] the mouth is terminal and the jaws equally protruding”.

Petrochromis horii was recognised as a distinct species based on both morphological and molecular analyses, and congeneric species from all major groups (so-called “Operational Taxonomic Units”), as well as all described species, of the genus were included in the analyses, except for Petrochromis sp. “Gold” and related species, which were only included in the molecular analysis, not in the morphological. P. horii proved to be morphologically distinct from all other species, but appeared closely related molecularly to P. sp. “Katete”. An mtDNA based phylogeny is suggesting the two species to be potentially conspecific (Takahashi and Koblmüller 2014). P. sp. “Katete” is very likely synonymous with P. sp. “Yellow” (Herrmann 1987: 142, 137, fig. top right; 1994: 14-17) and P. sp. ”Gold” (Konings and Dieckhoff 1992: 179, fig; Konings 1996: 94; 1998: 186). If also morphologically compared, P. sp. “Gold” (syn. “Katete”, “Yellow”) and P. horii would likely prove to be closely related in such a study as well.

From both personal experiences and public reports, we have learnt that Petrochromis sp. “Red” or closely related species occur in the whole southern part of the lake, i. e. continuously all around the shores, from Mahale Mountains at the central east coast via the Zambian coast to Cape Tembwe at the central west coast. Due to habitat-specific restrictions and deep water living conditions and thereby an obvious seclusion, plus an occasional inconspicuous colouration, the group is suggested to possibly have an even wider distribution in the lake. Based on unifying attributes, such as gross morphology, behaviour, physiology, ecological* preference, these species may together be regarded as a species group, in this case a monophyletic group of allopatrically isolated species. They are considered being distinct species, but closely related based on several attributes of traits (variable) and characters (non-variable). Pending a taxonomic study of all of the species, only gross differences/similarities are identified and mentioned. The species are the following:

1. Petrochromis sp. “Red”; occurs in the east central part of the lake; characterized by conspicuous sexual colourational dimorphism (adult males differ in colouration from females and juveniles; intensive red vs. brown).

2. Petrochromis sp. “Red mpimbwe”; occurs in the south eastern part of the lake; characterized by dark brown conspiciuously striped juveniles and dark brown partially striped adults with only weak dimorphism among sex; females tend to be more obviously striped than males. Populational differences in terms of being more or less red, orange or yellow. This species was introduced as P. sp. “Mpimbwe” from Cape Mpimbwe by us in 1991 (Zadenius 1991a: 37: “an unusual species, [in aquarium] brown yellowish with yellowish finnage”; Zadenius 1991b: 44-45: “A brand new deep living Petrochromis from Mpimbwe area, which has proven to be very peaceful. It is collected at a depth of 35 metres where it is occuring very sporadically”), but soon thereafter changed to P. sp. “Red mpimbwe” (Johansson 1994: 43; Johansson and Uusiportimo 1994: 43, fig.), by which it was exported for about ten years. The deep living habit of P. sp. “Red mpimbwe” was further documented by us in a species inventorial diving log from Cape Mpimbwe (Lundblad and Karlsson 1992). In 2002 when we found P. sp. “Red” at Lyamembe, and realized that the two species were practically identical, less colouration, we referred to both as P. sp. “Red”. We also considered P. sp. “Red” and P. sp. “Gold” to be potentially the same species, when we in 2003 displayed pictures of each species’ juveniles on our website mounted side by side, to demonstrate the similarities (see crop of 2003 website below). The southernmost variant was discovered at Kambwimba during a survey in 2008 when P. sp. “Red mpimbwe” was found at every rocky location from Karema all the way south to Kalambo River. Samples were collected at various locations, including Kambwimba, just north of the river. This variant, which was subsequently named “Flame tail”, was recently mentioned by Takahashi and Koblmüller (2014) as resembling P. horii; deposited at the Swedish Museum of Natural History. The variants in Kipili area and south to Fulwe Rocks, known as P. sp. “Kipili brown” (Konings 1996: 96; 1998: 50) are conspecific with P. sp. “Red mpimbwe”.

Fig. 3. Petrochromis sp. “Red” from Lyamembe and P. sp. “Gold” from Mtoto. The individuals were displayed side by side to demonstrate the similarities. Extract from African Diving Website; Display; Petrochromis page 5; August 2003.

3. Petrochromis horii; occurs in the most southern part of the lake, at Kasenga in Zambia, but likely further to both east and west. Morphology is limitedly known, but it seems to be characterized in colouration by a “moss green or dark green” body (appears very lightly coloured in photograph); and no apparent sexual differences, the largest specimen being a female (137.6 mm SL), suggesting the possibility of a reversed sexual dimorphism in body size (Takahashi and Koblmüller 2014), which seems less likely given corresponding characteristics of the other three species.

4. Petrochromis sp. “Gold”; occurs in the south western and west central part; characterized by an ontogenetical dimorphism (juveniles and adults completely differ in colouration; bright yellow vs. grey). P. sp. “Gold” has been documented as being rare in its natural habitat, which is basically due to its deep-living habit. From reports by Staeck (1994: 11): During three trips to the lake it was observed only twice; the first time in relatively shallow water when snorkel diving; both times at depths of 10-15 metres in Cameron Bay; and both individuals sub-adults. The idea, or statement, that only juveniles of P. sp. ”Gold” and not adults exhibit the bright yellow colouration, was presented in the same report (Staeck 1994: 13), and confirmed by Herrmann (1994: 15) based on aquarium studies made in 1983. An alternative view was presented by Brichard (1989: 396) thinking of P. sp. “Gold” as a small species, not growing larger than the observed yellow individuals, a view which was supported by Büscher (1994: 14). Büscher added to the fact that also very small juveniles (3 cm) are yellow (see also Herrmann 1985a: 443, fig. bottom), and further reported on a natural distribution between Cape Kashese and Mwerazi; and Konings (1996: 94) between Katete to Mtoto. Based on personal experience, we can also include Cape Tembwe to its natural surroundings, and confirm that adult individuals (15-20 cm) in the lake are not yellow; they are dark grey and commonly striped.

Fig. 4. Petrochromis sp. "Red Mpimbwe” in aquarium in Dar es Salaam, Tanzania: the very first individuals, collected at Cape Mpimbwe in 1991. The individuals were exported to Åleds Akvarium, Sweden September 6, 1991 (Zadenius 1991a).

The species group may be referred to as the Petrochromis horii species group. Some of the unifying characters are morphological (body pattern of vertical bars appearing the same, absence of egg-spots, almost identical shape and size of body); behavioural and physiological plus ecological* preferences (a curious species not easily scared away, relatively weakly territorial and mildly aggressive, usually living in deep water with sandy surrounding and occasional large rocks; semi-pelagic lifestyle, i. e. may keep a notable distance from substrate and  rocks vs. among rocks as seen in congenerics). Separating characters are basically morphological (e. g. colourational differences, ontogenetical dimorphism). Major rivers that flow into the lake, mark the distribution of the different species.

The four species are presumably diagnosable units: distinct phylogenetic species. They are nevertheless highly likely closely related, and would not unlikely end up as sisters on a cladogram. They are a species group, a taxon larger than species but smaller than genus, of allopatrically isolated species. Alternatively, they may together be treated as a polymorphic superspecies, as recently suggested for two of the species (Tawil 2010).

* Ecological specifications are not considered as diagnosable characters, but rather as an indication that such may be present. Regarding attributes, traits and characters: Kullander (1999), Wiley and Lieberman (2011).

External links:

TANAPA Mango Tree Bandas (mid-range, budget):
http://www.mahalepark.org/information.html

Greystoke Mahale (exclusive):
http://www.nomad-tanzania.com/west/greystoke-mahale

Kungwe Beach Lodge (exclusive):
http://www.mbalimbali.com/camps/kungwe_beach_lodge.php

Flycather Camp (mid-range):
http://www.flycat.com/camps/index.html

Reference;

Brichard, P. (1989) Pierre Brichard's book of cichlids and all the other fishes of Lake Tanganyika. T.F.H. Publications, Neptune City, NJ, 544 pp.

Büscher, H. H. (1994) Ergänzende Beobachtungen an der gelben Petrochromis-Art. P. 14 in: Staeck, W. (ed.) Buntbarsch Jahrbuch, 2, Bede-Verlag, Ruhmanns-felden, Germany, 96 pp.

Fitzpatrick, M. and Bewer, B. (2012) Lonely Planet. Country guides, Tanzania. Fifth edition. Lonely Planet Publications Pty Ltd, 408 pp.

Herrmann, H.-J. (1985a) Alte und neue Petrochromis - und kein Ende in Sicht (1). DATZ, 38 (10): 441-444. Alfred Kernen - Verlag, Essen.

Herrmann, H.-J. (1985b) Alte und neue Petrochromis - und kein Ende in Sicht (Schluß). DATZ, 38 (11): 487-490. Alfred Kernen - Verlag, Essen.

Herrmann, H.-J. (1987) Die Buntbarsche der Alten Welt - Tanganjikasee. Reimar Hobbing, Essen, West Germany, 239 pp.

Herrmann, H.-J. (1994) An intriguing yellow Petrochromis. Pp. 14-17 in: Konings, A. (ed.) The Cichlids Yearbook, 4. Cichlid Press, Lauenau, 96 pp.

Johansson, J.-Å. (1994) Importnytt från Åleds Akvarium AB. Ciklidbladet, 27 (6): 42-43. Nordiska Ciklidsällskapet.

Johansson, J.-Å. and Uusiportimo, J. (1994) Importnytt från Åleds Akvarium AB. Ciklidbladet, 27 (10): 42-44. Nordiska Ciklidsällskapet.

Karlsson, M. (1998) Norrut mot Kejsaren igen. Ciklidbladet, 31 (2): 26-48. Nordiska Ciklidsällskapet.

Konings, A. (1988) Tanganyika cichlids. Verduijn Cichlids and Lake Fish Movies, Zevenhuizen and Herten, 272 pp.

Konings, A. (1996) Back to nature guide om Tanganyikaciklider. Fohrman Aquaristik AB, Jonsered, Sweden, 129 pp.

Konings, A. (1998) Tanganyika cichlids in their natural habitat. Cichlid Press, El Paso, TX, 272 pp.

Konings, A. and Dieckhoff, H. W. (1992) Tanganyika secrets. Cichlid Press, St. Leon-Rot, Germany, 207 pp.

Kullander, S. O. (1999) Fish species - how and why. Reviews in Fish Biology and Fisheries, 9: 325-352. Kluwer Academic Publishers.

Lundblad, J. and Karlsson, M. (1992) Ett besök i den tysta världen - I vattnet vid Cape Mpimbwe. Akvariet, 66 (9): 268-272.

Maréchal, C. and Poll, M. (1991) In: Daget, J., Gosse, J.-P., Teugels, G. G. and Thys van den Audenaerde, D. F. E. (eds.) Check-list of freshwater fishes of Africa (CLOFFA), vol. 4. ISNB, Brussels, MRAC, Tervuren, ORSTOM, Paris, 740 pp.

Staeck, W. (1977) Cichliden: Verbreitung, Verhalten, Arten. Band 2. Engelbert Pfriem Verlag, Wuppertal-Elberfeld, Germany, 296 pp.

Staeck, W. (1983) Cichliden: Entdeckungen und Neuimporte. Band 3. Engelbert Pfriem Verlag, Wuppertal, 351 pp.

Staeck, W. (1994) Eine Rarität aus dem Tanganjikasee - Anmerkungen zu einer gelben Petrochromis-Art. Pp. 10-13 in: Staeck, W. (ed.) Buntbarsch Jahrbuch, 2, Bede-Verlag, Ruhmanns-felden, Germany, 96 pp.

Takahashi, T. and Koblmüller, S. (2014) A new species of Petrochromis (Perciformes: Cichlidae) from Lake Tanganyika. Ichthyological Research, DOI 10.1007/s10228-014-0396-9.  http://link.springer.com/article/10.1007%2Fs10228-014-0396-9

Tawil, P. (2010) Petrochromis sp. 'red'. The Cichlid Room Companion. Retrieved on May 22, 2014 http://www.cichlidae.com/species.php?id=1855&content=profile

Wiley, E. O. and Lieberman, B. S. (2011) Phylogenetics: Theory and Practice of Phylogenetic Systematics, Second Edition. Wiley-Blackwell, Hoboken, NJ, 432 pp.

Yamaoka, K. (1983) Feeding behavior and dental morphology of algae scraping cichlids (Pisces: Teleostei) in Lake Tanganyika. African Study Monographs, 4:77–89. http://repository.kulib.kyoto-u.ac.jp/dspace/bitstream/2433/68000/1/ASM_4_77.pdf?origin=publication_detail

Zadenius, M. (1982) Importnytt. Ciklidbladet, 15 (4): 8. Nordiska Ciklidsällskapet.

Zadenius, M. (1991a) Importnytt - Nyheter från Åleds Akvarium. Ciklidbladet, 24 (8): 36-38. Nordiska Ciklidsällskapet.

Zadenius, M. (1991b) Importnytt - Nyheter från Åleds Akvarium. Ciklidbladet, 24 (9): 42-45. Nordiska Ciklidsällskapet. 

Displaced Tropheus in Lake Tanganyika.

Repeated observations of displaced cichlids in habitat have been reported by several collectors in the ornamental fish trade (pers. comm.). During surveys in 2007/2008, displaced cichlids or hybrids were found (predominantly Tropheus, the commonmost being T. sp. “Kaiser”) at numerous localities (20) along the Tanzanian shores of the lake. The largest impact is suggested to derive from accidental releases of fish from portable storage cages kept in the lake. But also, sick or weak fish, if dumped overboard, could contribute to the fish displacement. The combined observations show that at most well-known collecting sites along the Tanzanian shore of the lake, individuals of many of the most prized Tropheus variants could be encountered (even variants originating from the Congo and Zambia).

Figs. 1-3. Three different forms of hybrid Tropheus.

The problem seems to be most common at pick-up and transshipment points, where fish are kept in submerged cages in wait for further transportation by road/air or for transit transportation to such a pick-up point. At three localities, the occurrence of alien Tropheus variants was found to be significant, namely at Shashete Bay, Cape Mpimbwe (transshipment point, Congo fish), Nanga Bay (sheltered bay), and Mlowa Point, Kipili (near pick-up point). At the latter locality, the alien Tropheus variants almost outnumbered the local congeneric. Allegedly, two weeks earlier a larger number of Tropheus from Zambian waters had escaped from a cage in the adjacent Kikopyo Bay near Kipili village. Though displaced cichlids could be found at many localities, it is expected that pick-up points at Kasanga, Kipili, Udachi/Kabwe, and Kigoma are the most affected areas in the Tanzanian part of the lake. Similar problems have been reported from Zambia (see below).

The northern side of Udachi Point was used by collectors as a temporary camp site, where fish often were kept in storage cages in the lake. Observations at Udachi of several alien fishes from the Congo were made in 2007 (genera Tropheus and Ophthalmotilapia). However, in 2012, no displaced fish were observed in the locality. The previously observed displaced individuals could have had time to spread over a larger area or been suppressed to deeper water (common for weak or old individuals). They could also have perished due to difficulties in establishing territory in the new environment, followed by intense food competition or fallen victim to predators. Two Tropheus hybrids were however found at Udachi in 2012 (see photos), an indication of non-native fishes previously being present in the area.

Fig. 4. Crocodiles sunbathing on rocks near Udachi Point. Cape Mpimbwe in the distance.

Tanganyika fisheries basically operate under an open access regime. This is clearly untenable and will lead to overexploitation of the valuable food source (FAO 1997: 52; Mölsä et al. 1999: 11). Also, the ornamental fishery needs to be regulated, and the parties involved should be informed about the lake’s unique fish fauna. Freelance collectors for the ornamental fish trade, selling fish at the lake to the highest bidder, are reported to be in operation in Tanzania, Congo and Zambia (at least as of 2007-2012). Lack of permanent stations at the lake and shortage of proper equipment (such as wire-meshed storage cages) may be a leading factor for the displacement of cichlids. Collected fish kept in cages at pick-up points along the shore are likely to escape if the net is torn by utters, crabs, larger predatory fish, and even by wear caused by waves.

The ornamental fish trade is self-remediating to some extent by collectors’ common tendency to catch odd looking individuals, as “new fish” are in demand from their clients. But a message to all active collectors would be an urging to ensure secure storage cages (or abandon the use of such altogether for fish originating elsewhere), and to remove alien individuals and hybrids from the habitat whenever observed. With awareness and joint forces the problem could diminish or even cease to exist. If disregarded, it could eventually lead to disruptions in the lake’s native fish fauna.

Hybridization among naturally sympatric species (non-displaced) in Lake Tanganyika seems uncommon; alternatively, hybridization is difficult to detect. The situation in Lake Malawi is said to be similar: “There have been only a handful of documented hybridizations in Lake Malawi” (Stauffer and Kellogg 1996: 26). But “recent work shows that hybridization and introgression are more frequent than imagined by earlier evolutionists...” (Coyne and Orr 2004: 41); and recently Koblmüller et al. (2007) showed on a net-like phylogeny for shell-breeding Lamprologini, instead of the normally tree- or bushlike, as an indication of hybridization. So, even though hybridization unlikely is a frequent phenomenon, it has potentially influenced evolution. The non-hybridization may indicate ecological and phenotypical balance among sympatric species. Thus, dislocation of species, and introduction of alien, invasive species, may likely disturb the balance. One of the results may be hybridization.

Deliberate displacement of species made by humans are usually referred to as ’translocation’. The translocation of Cynotilapia afra from Likoma Island to Thumbi West Island (both locations in Lake Malawi) resulted in intergeneric hybridization with the native population of Maylandia zebra; same result with the translocation of M. callainos from Nkhata Bay area to the same island (Stauffer and Kellogg 1996: 26; Barlow 2000: 236). Additional species reported being translocated to Thumbi West Island are e. g. Tropheops sp. “Mbenji blue”, Melanochromis loriae, Pseudotropheus perileucos, P. johannii, Labidochromis freibergi, L. gigas, L. joanjohnsonae, L. strigatus (Lewis et al. 1986: 63-67; Konings 2007b: 75); Maylandia aurora, T. sp. “Membe” and P. socolofi (Konings 2007a: 176, 197, 204).

In 1998 about 300 individuals of Tropheus were collected from several sites in the southern part of Lake Tanganyika, intentioned to be exported for the tropical fish trade (Salzburger et al. 2006). But export permit was not granted and the fishes were released back into the lake; however, not to their domestic locations but dumped in a small harbour bay in Mpulungu; this was followed soon thereafter by a study on the assortative reproduction patterns among Tropheus (Salzburger et al. 2006). Based on colouration, five different variants could be identified: a light-olive variant conforming to the indigenous population, identified as or resembling the Mbita type; a dark-olive variant conforming to populations found along the Zambian east coast [most likely from Isanga, also known as Kalambo type]; an orange type, Ilangi; a red type, Chilanga; a stripe-red type, Chimba (Salzburger et al. 2006). The origins of the latter three were “assigned to the shoreline northwest of the Lufubu estuary, between Cape Inangu and Moliro”. A neighbouring population, situated about 50 metres away from the composite population, was included in the study as a reference group. This group plus Mbita and Kalambo were grouped together with mtDNA sequences into the same lineage (descent), while the other three (Ilangi, Chilanga, Chimba) clustered together in a different lineage. Tropheus samples were analysed based on colouration and DNA*. Sampling of both composite and reference population was done in 1999, 2000, 2001, and eventually the result showed that 68% of the offspring seemed to have originated from within-morph matings, and only 1,6% (3 juveniles out of 180) came from mating between the two different lineages (olive/reddish). Most of the hybrids produced were between Mbita and Kalambo. The interpretation of the result was in line with assortative matings, and signals such as visible, chemical, acoustic were suggested to be decisive, especially signals relating to colour-assortative matings.

The study was followed up in 2010 (Egger et al. 2012). Samplings of both the composite and reference population were done, as well as a re-evaluation of the result from the 2006 study. The result was different this time, and showed that intermediate phenotypes (a mix of two or more colour variants) were present already in 2000 and increased dramatically in abundance between 2001 and 2010. In the neighbouring population, no intermediate phenotypes were identified from 1999 to 2001, but were present in 2010. For both the neighbouring and composite population sampled in 2001 and in 2010, only few individuals could be assigned to a particular colour variant with correct genetic corresponding, indicating a high frequency of hybridization between morphs. The result also showed that the hybrids and nonindigenous individuals from the composite population in the harbour bay had spread to the neighbouring population (intermediate colour morphs were found, Egger et al. 2012: 517); therefore, a hybridization event in general is unlikely geographically isolated, but may spread to other populations.

The hybridization is speculated of being due to periodic algal blooms or increased sedimentation causing turbid conditions (Egger et al. 2012). But studies of Tropheus have shown that the frequency of inter-morph matings increases with increasing colour pattern similarities, i. e. similar looking Tropheus-variants more easily hybridize than differently looking variants (Egger et al. 2008). Therefore an alternative cause of increasing hybridization is the weakening of ideals; where just a single phenotype used to characterise the ideal are now several, of which may increasingly be accepted among individuals. 

Concludingly, it seems to be rather safe to say that displacement of species will eventually result in hybridization.

* Analyses of DNA sequences of mitochondrial control region plus five microsatellite loci.

Reference;

Barlow, G. W. (2000) The cichlid fishes - Nature’s grand experiment in evolution. First paperback edition, printed in 2002. Basic Books, New York, NY, 335 pp.

Coyne, J. A. and Orr, H. A. (2004) Speciation. Sinauer Associates, Inc. Sunderland, MA, 545pp.

Egger, B., Obermüller, B., Eigner, E., Sturmbauer, C. and Sefc, K. M. (2008) Assortative mating preferences between colour morphs of the endemic Lake Tanganyika cichlid genus Tropheus. Hydrobiologia, 615 (1):37–48.   http://link.springer.com/article/10.1007%2Fs10750-008-9564-0

Egger, B., Sefc, K. M., Makasa, L., Sturmbauer, C. and Salzburger, W. (2012) Introgressive hybridization between color morphs in a population of cichlid fishes twelve years after human-induces secondary admixis. Journal of Heredity, 103 (4): 515-522.  http://jhered.oxfordjournals.org/content/early/2012/05/03/jhered.ess013.full

FAO (1997) Technical guidelines for responsible fisheries, 4, ‘Fisheries management’. FAO, Rome.

Koblmüller, S., Duftner, N., Sefc, K. M., Aibara, M., Stipacek, M., Blanc, M., Egger, B. and Sturmbauer, C. (2007) Reticulate phylogeny of gastropod-shell-breeding cichlids from Lake Tanganyika—the result of repeated introgressive hybridization. BMC Evolutionary Biology, 7 (7): 13 pp.  http://www.biomedcentral.com/1471-2148/7/7

Konings, A. (2007a) Malawi cichlids in their natural habitat.  Fourth edition. Cichlid Press, El Paso, TX, 424 pp.

Konings, A. (2007b) Die Buntbarsche der Insel Thumbi West. DCG-Informationen, 38 (4): 73-78. Deutsche Cichliden-Gesellschaft e. V.

Lewis, D. S. C., Reinthal, P. N. and Trendall, J. (1986) A guide to the fishes of Lake Malawi National Park.  World Wildlife Fund, Gland, Switzerland. 71 pp.

Mölsä, H., Reynolds, J. E., Coenen, E. J. and Lindqvist, O. V. (1999) Fisheries research towards resource management on Lake Tanganyika. Hydrobiologica, 407: 1-24.

Salzburger, W., Niederstätter, H., Brandstätter, A., Berger, B., Parson, W., Snoeks, J. and Sturmbauer, C. (2006) Colour-assortative mating among populations of Tropheus moorii, a cichlid fish from Lake Tanganyika, East Africa. Proc. R. Soc. B, 273: 257–266.http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1560039/

Stauffer, J. R., Jr. and Kellogg, K. A. (1996) Sexual selection in Lake Malawi Cichlids. Pp. 23-28 in: Konings, A. (ed.) The Cichlids Yearbook, vol. 6. Cichlid Press, Lauenau, 96 pp.

Visit Tanzania!

Under this heading we will over time post recommendations to different interesting dive sites along the Tanzanian shore of Lake Tanganyika. First out is Frontosa Reef, an untouched underwater world in the deep where fish is in abundance.

Located barley 4 km off Kolwe Point Cape Mpimbwe, Frontosa Reef offers one of the most amazing diving experiences in Lake Tanganyika. The submerged reef's shallowest depth is about 40 metres and it consists of huge boulders, some measuring up to more than 10 meters in diameter. In the deeper regions of the reef are dispersed open areas covered with thick layers of hard shell fragments. While the water is often crystal-clear, a strong current may occur from time to time, making some dives a bit of a challenge. Coordinates to Frontosa Reef: 7°06'38'' S, 30°27'44'' E (shallow point).

Fig. 1. Fisherman fishing with line and hook off Cape Mpimbwe.

Local fishermen from Msalaba, fishing for Cyphotilapia with line and hook, showed us the offshore location in July 1994. To find shallow points at the reef, a larger area was during a one week period scanned with eco-sounder. Though like finding a needle in a haystack, the task eventually resulted in the fact that we found several spots with depths around 40 m (one of the coordinates given above).

The most common fish species found at the reef is Cyphotilapia gibberosa, a species which was not identified as a distinct species of its own until 2003 (Takahashi and Nakaya 2003). Earlier the fish at the reef was known as Cyphotilapia frontosa. C. gibberosa is very curious by nature and will readily approach a visitor. They occur at the reef in very large numbers, and among the boulders at 50 metres, individuals of more than 40 cm are occasionally seen. They tend to be solid blue.

In the least deep areas, the first fish species one will encounter are Cyprichromis sp. “Mpimbwe zebra”, C. pavo, Neolamprologus sp. “Calliurus giant” and Lepidiolamprologus mimicus. In appearance and behaviour, C. sp. “Mpimbwe zebra” is similar to C. zonatus from Zambian waters. The latter was prior to formal description known as C. sp. “Zebra” (Takahashi et al. 2002; Konings 2003). The two species may be closely related, and interjacent similar populations along the coast have been discovered (pers. obs.). Both males and females ofC. sp. “Mpimbwe zebra” are nicely coloured; males orange and females yellow.

Fig. 2. Cyprichromis sp. "Mpimbwe zebra" at Frontosa Reef", depth 45 m.

Neolamprologus sp. “Calliurus giant” may be synonymous with N. calliurus, which in turn is synonymous with N. brevis, at least according to Poll (1986) and according to several scientific studies and field observations, e. g. Ota et al. (2012). However, N. sp. “Calliurus giant” appears and behaves differently than the ‘ordinary’ N. calliurus (syn. N. brevis). At the reef, no members of the N. savoryi species complex (Verburg and Bills 2007) seems to have been established (pers. obs.), and the niche which at other places normally is occupied by some of the members in this complex, is here at Frontosa Reef instead inhabited by N. sp. “Calliurus giant”. They exist in great numbers. A strikingly orange spot adorns their head. Both males and females are known to grow relatively large, commonly 11 and 9 cm respectively. They do not breed in empty shells, but in crevices and openings in the rocky habitat; and they normally dwell in the open water collecting plankton, sometimes in large schools. This behaviour is very similar to most members of the N. savoryi species complex elsewhere.

Fig. 3. Neolamprologus sp. "Calliurus giant" at Frontosa Reef.

Open areas with scattered medium sized rocks are found in certain deeper areas. In these areas Julidochromis regani is common. The variant found here is one of the largest in the lake. In the same habitat lives an unidentified species of Telmatochromis, as well as (what seems to be) the delicate Xenotilapia nasus. Beneath boulders in the deeper regions of 50 metres or more, one of the lake’s less commonly known fish species can be found. This is Trematochromis benthicola (syn. Trematochromis schreyeni (Takahashi et al. 2006), Ctenochromis benthicola (Geerts 2006)). It is a timid species and spends much of its day-time hiding in the rocky environment. On rare occasions, deep orange mutant coloured individuals can be spotted. Such colour variation by this species is known to occur elsewhere in the lake as well, and has been reported from Uvira and Pemba, in the northern part of the lake (Poll 1979). Further on, exceptionally large individuals of Benthochromis horii are found hovering over the boulders.

Even though we recommend anybody to dive the reef we do recommend a certain level of dive experience before venturing the dive site. For navigation purposes in the rocky maze, a hand held dive reel or a bright beacon attached to an ascending line is recommended in order to practise a safe dive and secure ascent.

At the given coordinates is a shallow point of 40 m. The depth is measured from the top of a group of boulders and it gets abruptly deeper when getting off the boulders. If inexperienced it is recommended to stay at the boulders within reach of the descending line and from there enjoy the spectacle of nature.
Because of the offshore locality and deep water nature, there are no hippos, crocodiles or water cobras at the reef so you don’t have to watch your back but could enjoy the dive to the fullest.

High standard accommodation is available at Kipili, 40 km south of the reef with three different options; the stunning Lupita Island Resort (exclusive), the universally praised Lake Shore Lodge (PADI-certified diving operations) and the lakeside guesthouse St. Benedict Mission (budget). At Karema, 30 km north of the reef, Julieta Guesthouse (budget) is located on the beach side of town. In addition to this, several suitable campsites are available at nearby Cape Mpimbwe.

External links:

Tanzania National Parks: http://www.tanzaniaparks.com/
Tanzania Tourist Board: http://www.tanzaniatouristboard.com/
Lake Shore Lodge: http://lakeshoretz.com/
Lupita Island Resort: http://tanzaniafirelightsafaris.com/

Reference;

Fitzpatrick, M. and Bewer, B. (2012) Lonely Planet. Country guides, Tanzania. Fifth edition. Lonely Planet Publications Pty Ltd, 408 pp.

Geerts, M. (2006) Cichlidesque. Actualiteiten en Wetenswaardigheden. Verwikkelingen rond Trematochromis schreyeni. Cichlidae - Journal of the Dutch and Belgian Cichlid Associations, 32 (4): 99-100.

Konings, A. (2003) New Cyprichromis from Zambia. Cichlid News, 12 (2): 6-15. Aquatic Promotions Division, Miami, FL.

Ota, K., Aibara, M., Morita, M., Awata, S., Hori, M. and Kohda, M. (2012) Alternative reproductive tactics in the shell-brooding Lake Tanganyika cichlid Neolamprologus brevis. International Journal of Evolutionary Biology, 2012 (915265): 10 pp.

Poll, M. (1979) Un Haplochromis rouge du lac Tanganika, femelle de H. benthicola Matthes, 1962 (Pisces, Cichlidae). Revue de Zoologie Africaine, 93 (2): 467-475.

Poll, M. (1986) Classification des Cichlidae du lac Tanganika. Tribus, genres et espèces. Académie Royale de Belgique, Mémoires de la Classe des Sciences, Collection in 8°, (2), 45 (2): 1-163.

Takahashi, T. and Nakaya, K. (2003) New species of Cyphotilapia (Perciformes: Cichlidae) from Lake Tanganyika, Africa. Copeia, 2003 (4): 824-832.

Takahashi, T., Hori, M. and Nakaya, K. (2002) New species of Cyprichromis (Perciformes: Cichlidae) from Lake Tanganyika, Africa. Copeia, 2002 (4): 1029-1036.

Takahashi, T., Snoeks, J. and Nakaya, K. (2006) Trematochromis schreyeni Poll, 1987, a junior synonym of 'Ctenochromis' benthicola (Matthes, 1962) (Perciformes: Cichlidae) from Lake Tanganyika. Journal of Fish Biology, 68 (A): 56-67.

Verburg, P. and Bills, R. (2007) Two new cichlid species Neolamprologus (Teleostei: Cichlidae) from Lake Tanganyika, East Africa. Zootaxa, 1612: 25-44.