A scientific mission to survey the ecology of fish communities in lake Tanganyika (Tanzania)
About 670 km long, Lake Tanganyka is one of the largest lakes in the world. It is also a veritable laboratory of evolution inhabited by hundreds of fish species that are found nowhere else (endemic). Among them, more than 220 belong to the single Cichlidae family.
For scientists, Lake Tanganyika offers countless examples of the speciation process wich leads to the appearance of new species. The specific ecological condition of this lake with the dimensions of an inland sea gave birth to many diverse morphological types, strikingly reminding a wide variety of different marine fish families. Studying how tens of closely related species share the same habitat resources is interesting in terms of speciation (level of ecological differenciation according to kinship), and in comparison with their marine counterparts ("ecological equivalents"). ...
This scientific diving mission lasted from April 11 to 27, 2015. It was held in Kipili (south of the lake, Tanzania) with a team of 8 volunteer divers. Its main goal was to assess habitat preferences of the different species sharing the same rocky environment in a given location. After an exploration phase around several islands, we selected a survey site in Mvuna Island (see map). The survey protocol we used had already been tested during several field missions. The principle is to "quantify" as many features as possible of the close environment of a given number of fish individuals by semi-quantitatively assessing a series of variables describing the habitat (topography, living cover...) and the way the fish places itself within this context. The results have not been completely analysed yet. However, a few graphs are provided here together with the photos.
This trip was organised in partnership with the French tour operator Blue World, and was hosted by Lake Shore Lodge in Kipili, a renowned high standard resort. The team managed by Patrick Louisy (Emmanuel Gouin, Marie Gromand, Patrick Noël, Marie-Joëlle and Pierre Rouillan, Denis Sabatier, Hervé Thédy) deserves congratulations for their hard work and enthusiasm. And many thanks to Louise and Chris Horsfall and all the Lake Shore Lodge team for their kindness and involvement in the achievement of our mission.
Hervé, Denis, Pierre and Marie-Joëlle checking their photos, identifying the species and recording the observations made during the day.
A lot of work, but in a nice place...
Date:
22 April 2015
Informations
Title:
Manu and Marie recording the observations of the day
Description:
A serious job with a nice landscape!
Date:
22 April 2015
Informations
Title:
The slate used for underwater habitat records
Description:
In order to study habitat preferences, for each individual fish observed, the underwater observers had to record 40 different parameters.
Main subject of the survey: herbivorous Cichlid fish
Description:
The study of habitat preferences was performed on 17 species* of herbivorous Cichlid fish (algae grazers) in a sheltered rocky habitat between 0 and 11 m depth.
* List of species surveyed:
Tropheus brichardi, Simochromis diagramma, Pseudosimochromis curvifrons, Interochromis loocki, Petrochromis ephippium, P. famula, P. fasciolatus, P. sp. Kipili brown, P. cf. macrognathus "Rainbow", P. polyodon "Texas", Ophthalmotilapia boops, O. ventralis, Cunningtonia longiventralis, Asprotilapia leptura, Eretmodus cyanostictus, Telmatochromis cf. brachygnathus, T. vittatus.
The 17 herbivorous species studied: Tropheus brichardi
Date:
14 April 2015 10h07
Informations
Title:
The 17 herbivorous species studied: Tropheus brichardi...
Date:
24 April 2015 12h29
Informations
Title:
The 17 herbivorous species studied: Tropheus brichardi...
Date:
13 April 2015
Informations
Title:
The 17 herbivorous species studied: Tropheus brichard...
Date:
16 April 2015 12h30
Informations
Title:
The 17 herbivorous species studied: Simochromis diagramma
Date:
24 April 2015 12h57
Informations
Title:
The 17 herbivorous species studied: Simochromis diagramma...
Date:
20 April 2015 12h27
Informations
Title:
The 17 herbivorous species studied: Pseudosimochromis...
Date:
20 April 2015 12h34
Informations
Title:
The 17 herbivorous species studied: Petrochromis polyodon...
Date:
17 April 2015 12h38
Informations
Title:
The 17 herbivorous species studied: Petrochromis polyodon...
Date:
23 April 2015 11h36
Informations
Title:
The 17 herbivorous species studied: Petrochromis ephippium
Date:
14 April 2015 17h43
Informations
Title:
The 17 herbivorous species studied: Petrochromis cf....
Date:
14 April 2015 16h55
Informations
Title:
The 17 herbivorous species studied: Petrochromis cf....
Date:
14 April 2015 16h39
Informations
Title:
The 17 herbivorous species studied: Petrochromis famula
Date:
18 April 2015 16h11
Informations
Title:
The 17 herbivorous species studied: Petrochromis sp....
Date:
17 April 2015 12h36
Informations
Title:
Les 17 végétariens étudiés : Petrochromis sp....
Date:
21 April 2015 09h44
Informations
Title:
The 17 herbivorous species studied: Petrochromis fasciolatus
Date:
24 April 2015 11h47
Informations
Title:
The 17 herbivorous species studied: Petrochromis fasciolatus
Date:
24 April 2015 11h47
Informations
Title:
The 17 herbivorous species studied: Interochromis loocki
Description:
This fish has long been called Petrochromis sp. orthognathus "tricolor" (Konings, 1998).
Date:
17 April 2015 13h14
Informations
Title:
The 17 herbivorous species studied: Ophtalmotilapia boops...
Date:
13 April 2015
Informations
Title:
The 17 herbivorous species studied: Ophtalmotilapia boops...
Date:
16 April 2015 11h59
Informations
Title:
The 17 herbivorous species studied: Ophthalmotilapia...
Date:
21 April 2015 13h03
Informations
Title:
The 17 herbivorous species studied: Ophthalmotilapia...
Date:
15 April 2015 18h25
Informations
Title:
The 17 herbivorous species studied: Ophthalmotilapia...
Date:
22 April 2015 12h28
Informations
Title:
The 17 herbivorous species studied: Cunningtonia...
Date:
21 April 2015 10h01
Informations
Title:
The 17 herbivorous species studied: Asprotilapia leptura
Date:
13 April 2015
Informations
Title:
The 17 herbivorous species studied: Eretmodus cyanostictus
Date:
24 April 2015 17h50
Informations
Title:
The 17 herbivorous species studied: Telmatochromis vittatus
Date:
13 April 2015
Informations
Title:
The 17 herbivorous species studied: Telmatochromis cf....
Description:
According to Konings (2015), this fish could be a morphological variation of Telmatochromis temporalis. However, on our survey site in Mvuna, it coexists with T. temporalis from which it differs by its morphology, colour pattern and habitat preferences.
Date:
16 April 2015 11h53
Informations
Title:
Graph: observed sizes
Description:
This graph shows the size range of the adult and subadult individuals observed for the habitat preferences survey in Mvuna.
NB Sizes were estimated underwater; the maximal sizes in the graph are not necessarily the maximum sizes reached by these species on this location.
Date:
11 May 2015
Informations
Title:
Graph: observation depths
Description:
This graph shows the depth range of the 17 herbivorous species surveyed in the site called Nursery (Mvuna).
The blue bars indicate the observation depth of the adult and subadult individuals included in the habitat preferences survey in the sheltered rocky section of the site.
Date:
11 May 2015
Informations
Title:
Graph: distance from substrate
Description:
This graph shows the results for one of the numerous parameters recorded in the habitat preferences survey of herbivorous Cichlids in Mvuna: the distance from the substrate.
- Two species (Asprotilapia leptura and Eretmodus cyanostictus) are always very close to the substrate (less than 2 cm; see dark green bars). Telmatochromis cf. brachygnathus and T. vittatus, which hide in narrow crevices, also remain almost in contact with the rock most of the time.
- Although much more mobile, Tropheus brichardi, Simochromis diagramma and Pseudosimochromis curvifrons swim very close to the substrate most of the time (about 60 %).
- On the opposite, Ophthalmotilapia boops and O. ventralis prefer clearly to swim away from the substrate (dark blue bars) although they graze algae on the rocks.
- The often larger Petrochromis (and Interochromis) species mostly hover at an intermediate distance, between 3 and 20 cm from the rock.
Date:
11 May 2015
Informations
Title:
Cyphotilapia gibberosa (juvenile)
Description:
Considered a synonym of C. frontosa by Konings (2015).
According to Konings (2015), this species is synonymous with Neolamprologus pulcher. However, the population in the Kipili area clearly displays the colour pattern formerly considered to be typical of N. brichardi.
pictures
