Fisheries of northwestern Lake Tanganyika

Study Extent

The field area was located at the northwestern part of Lake Tanganyika along the Congolese shores near and north of Baraka City in the territory of Fizi. Due to logistic constraints and field accessibility (human activities disruption or not, fishing effort) and safety, the sampling and survey sites consisted of main villages established along the coastline in these areas. This region has a tropical humid climate characterized by an alternation of wet and dry seasons and is currently subject to physical factors at different scales. All those beach fishing sites were easily accessible from each one by boat and have fishing activities as main occupation. Whenever necessary, each main site was split up into different small sub-sites according to the type of littoral habitat of the lake, i.e., sandy, rocky, mixed, and the type of fishing practices. The critical habitat of a fish species is defined as a geographic or physical area essential to the realization of the life cycle (Lévêque 1995). However, the knowledge of local communities and advices of experienced local fishermen were considered during the fish sampling in each site. At the field of investigation, some localities of high human influences are undergoing alterations (water pollution and sedimentation, fishing with unsuitable fishing gears and techniques and deforestation) with some fish species exposed to human pressures or extinction in the future.

Sampling

Collections of fish samples were performed once or twice per site during the study period using complementary methods in each selected station. Individuals fish species were collected in different habitats within the selected sites from local commercial catches of fishermen using their different fishing gears: gillnets of different mesh sizes and widths, beach seines and liftnets with mixed mesh sizes, gillnets with various techniques (i.e., monofilament, dormant, encircling and deep gillnets, …) and illegal mosquito nets of smaller mesh-sizes (02-03 mm). These various gears were surveyed in each sampling day and site according to the fishing habitat (lake substratum) and lake site (inshore vs. offshore). We recorded the features of each net directly at the sampling site such as the length, width (near 1.00 m) and mesh-size (near 1.00 mm) using a measuring tape or decametre. We noted the fishing depth, the duration as well as the effort (e.g., number of nets per active fishing unit, number of fisherman and net hauls) for each gear. The presence of each gear at a site allowed assessing the rate of fishing activity and fish distribution within the sampling habitats. The type of fishery and net, the numbers of fishermen involved per trip and per fishing unit were recorded and are discussed in relation to the type of gear used. After each fishing trial, fresh weight (in kg) of each sample was measured per fishing gear and number (net hauls per trip) recorded whenever possible. For each type of fishing, fish samples with a selection of species were usually bought from fishermen, and preliminary sorted at sampling sites (as fishermen did not deliver their entire fish capture) by species and after being weighed. The fish samples (handful) were collected and killed and preserved into ethanol (75%) and then fixed in formaldehyde (10%) to slow decomposition of organs. All fish species captured were identified, weighed and counted following the fishing habitat and effort. The samples were separated into smaller bags by type of fishing-gear, site and other parameters of the fishing-effort and environment and kept in 10% formaldehyde for subsequent analysis in the laboratory

Quality Control

Quality control was implemented through the steps and process outlined for all staff at the Center for Research on Hydrobiology. In addition, there was internal quality control measures that were put in place such as routine monitoring and evaluation of project progress.

Method steps

1. At the laboratory of Biology at the Centre de Recherche en Hydrobiologie (CRH, Uvira, DR Congo) each sample was re-sorted into species by fishing gear and habitat or fishing effort and each species identified following available books and/or keys (Fryer and Iles 1972; Axelrod et al 1977; Poll 1956, 1986; Brichard 1978, 1989; Eccles 1992; Konings 2015; Fermon et al 2007) Then, specimens were sorted by species, counted and the total, standard lengths (TL and SL) and the body height (BH) were measured (nearest 0.1 mm). These measurements and measuring techniques of fish were executed according to Barel et al. (1977), Eccles (1992), Snoeks (1994), Snoeks et al (1994), Snoeks et al (1997), Snoeks (2000) and Hanssens and Snoeks (2003). Sex was determined by exanimating the genital papillae and other external body feature such as coloration patterns (Snoeks 2000). For details in the sex, fish were dissected to determine the maturity stages of gonads following De Kimpe (1964), Micha (1973), Plisnier (1990). Each fish was then weighed (using various scales following species and individual sizes), the viscera and the gonads removed, and weighed (nearest 0.001g) and the body re-weighed to calculate the gonado-somatic index (GSI).

All fish were identified to genus or species.

1. Lates mariae
   rank: species
2. Boulengerochromis microlepis
   rank: species
3. Limnotilapia dardennii
   rank: species
4. Shuja horei
   rank: species
5. Oreochromis tanganicae
   rank: species
6. Stolothrissa tanganicae
   rank: species
7. Limnothrissa miodon
   rank: species
8. Petrochromis polyodon
   rank: species
9. Lamprichthys tanganicanus
   rank: species
10. Perissodus microlepis
    rank: species
11. Neolamprologus pleuromaculatus
    rank: species
12. Grammatotria lemairii
    rank: species
13. Chrysichthys brachynema
    rank: species
14. Dinotopterus cunningtoni
    rank: species
15. Boulengerochromis microlepis
    rank: species
16. Stolothrissa tanganicae
    rank: species
17. Grammatotria lemairii
    rank: species
18. Lates stappersii
    rank: species
19. Stolothrissa tanganicae
    rank: species
20. Limnothrissa miodon
    rank: species
21. Grammatotria lemairii
    rank: species
22. Boulengerochromis microlepis
    rank: species
23. Callochromis spp.
    rank: genus
24. Lates microlepis
    rank: species
25. Shuja horei
    rank: species
26. Lamprichthys tanganicanus
    rank: species
27. Trematocara spp.
    rank: genus
28. Chrysichthys sianenna
    rank: species
29. Bathybates fasciatus
    rank: species
30. Benthochromis tricoti
    rank: species
31. Simochromis diagramma
    rank: species
32. Chrysichthys sianenna
    rank: species
33. Mastacembelus moorii
    rank: species
34. Stolothrissa tanganicae
    rank: species
35. Limnothrissa miodon
    rank: species
36. Limnotilapia dardennii
    rank: species
37. Shuja horei
    rank: species
38. Limnotilapia dardennii
    rank: species
39. Boulengerochromis microlepis
    rank: species
40. Simochromis diagramma
    rank: species
41. Callochromis spp.
    rank: genus
42. Lepidiolamprologus cunningtoni
    rank: species
43. Lamprologus callipterus
    rank: species
44. Synodontis grandiops
    rank: species
45. Grammatotria lemairii
    rank: species
46. Telmatochromis dhonti
    rank: species
47. Benthochromis tricoti
    rank: species
48. Hemibates stenosoma
    rank: species
49. Bathybates fasciatus
    rank: species
50. Benthochromis tricoti
    rank: species
51. Chrysichthys sianenna
    rank: species
52. Limnotilapia dardennii
    rank: species
53. Petrochromis microlepis
    rank: species
54. Cyathopharynx furcifer
    rank: species
55. Limnochromis auritus
    rank: species
56. Gnathochromis permaxillaris
    rank: species
57. Trematocara spp.
    rank: genus
58. Xenotilapia spp.
    rank: genus
59. Boulengerochromis microlepis
    rank: species
60. Lates microlepis
    rank: species
61. Auchenoglanis occidentalis
    rank: species
62. Chrysichthys brachynema
    rank: species
63. Limnochromis auritus
    rank: species
64. Bathybates fasciatus
    rank: species
65. Hemibates stenosoma
    rank: species
66. Trematocara spp.
    rank: genus
67. Gnathochromis permaxillaris
    rank: species
68. Chrysichthys sianenna
    rank: species
69. Grammatotria lemairii
    rank: species
70. Limnothrissa miodon
    rank: species
71. Stolothrissa tanganicae
    rank: species
72. Limnotilapia dardennii
    rank: species
73. Petrochromis spp.
    rank: genus
74. Shuja horei
    rank: species
75. Boulengerochromis microlepis
    rank: species
76. Oreochromis tanganicae
    rank: species
77. Lamprologus callipterus
    rank: species
78. Lepidiolamprologus cunningtoni
    rank: species
79. Neolamprologus brevis
    rank: species
80. Stolothrissa tanganicae
    rank: species
81. Simochromis diagramma
    rank: species
82. Shuja horei
    rank: species
83. Callochromis spp.
    rank: genus
84. Neolamprologus burtoni
    rank: species
85. Synodontis grandiops
    rank: species
86. Grammatotria lemairii
    rank: species
87. Oreochromis tanganicae
    rank: species
88. Limnotilapia dardennii
    rank: species
89. Neolamprologus sarvoyi
    rank: species
90. Lates stappersii
    rank: species
91. Limnothrissa miodon
    rank: species
92. Limnothrissa miodon
    rank: species
93. Stolothrissa tanganicae
    rank: species
94. Shuja horei
    rank: species
95. Neolamprologus pleuromaculatus
    rank: species
96. Limnochromis auritus
    rank: species
97. Neolamprologus pleuromaculatus
    rank: species
98. Limnotilapia dardennii
    rank: species
99. Shuja horei
    rank: species
100. Triglachromis otostigma
     rank: species
101. Synodontis grandiops
     rank: species
102. Petrochromis spp.
     rank: genus
103. Lobochilotes labiatus
     rank: species
104. Tropheus duboisi
     rank: species
105. Simochromis diagramma
     rank: species
106. Lepidiolamprologus elongatus
     rank: species
107. Perissodus microlepis
     rank: species
108. Gnathochromis pfefferi
     rank: species
109. Stolothrissa tanganicae
     rank: species
110. Neolamprologus pleuromaculatus
     rank: species
111. Chrysichthys sianenna
     rank: species
112. Telmatochromis temporalis
     rank: species
113. Limnothrissa miodon
     rank: species
114. Lates stappersii
     rank: species
115. Lates microlepis
     rank: species
116. Shuja horei
     rank: species
117. Boulengerochromis microlepis
     rank: species
118. Limnotilapia dardennii
     rank: species
119. Bagrus docmak
     rank: species
120. Lophiobagrus cyclurus
     rank: species
121. Tylochromis polylepis
     rank: species
122. Lates microlepis
     rank: species
123. Oreochromis tanganicae
     rank: species
124. Grammatotria lemairii
     rank: species
125. Limnotilapia dardennii
     rank: species
126. Bathybates fasciatus
     rank: species
127. Lamprologus callipterus
     rank: species
128. Aulonocranus dewindti
     rank: species
129. Bagrus docmak
     rank: species
130. Chrysichthys sianenna
     rank: species
131. Limnotilapia dardennii
     rank: species
132. Grammatotria lemairii
     rank: species
133. Bathybates fasciatus
     rank: species
134. Auchenoglanis occidentalis
     rank: species
135. Lepidiolamprologus profundicola
     rank: species
136. Cyathopharynx furcifer
     rank: species
137. Chrysichthys sianenna
     rank: species
138. Lates stappersii
     rank: species
139. Limnothrissa miodon
     rank: species
140. Lates stappersii
     rank: species
141. Limnothrissa miodon
     rank: species
142. Stolothrissa tanganicae
     rank: species
143. Tylochromis polylepis
     rank: species

Northern Lake Tanganyika within the boundaries of the Democratic Republic of the Congo.