Analysis of the length-frequency data on Copadichromis likomae (Cichlidae) from Lake Niassa, Mozambique, suggests an asymptotic length of SL∞=14 cm associated with a K value of 0.93 yearˉ¹. Total and natural mortalities were estimated as 3.2 yearˉ¹ and 1.9 yearˉ¹, respectively. Yield-per-recruit analysis suggests that E=0.36 in this fishery

Massinga, A.V.R.

Aquatic Commons

ABSTRACT 
Revista de Investiga<;ao Pesqueira 
Maputo No. 21 (1992): 59- 68 
Growth, Mortality and Yield-per-Recruit 
of Copadichromis likomae (Cichlidae) 
in Lake Niassa, Mozambique 
by 
ALFREDO V. R. MASSINGA 
Analysis of the length-frequency data on Copadichromis likomae (Cichlidae) from Lake Niassa, 
Mozambique, suggests an asymptotic length of SLoo = 14 em associated with a K value of 0.93 
year-1• Total and natural mortalities were estimated as 3.2 year-1 and 1.9 year-1, respectively. Yield-
per-recruit analysis suggests that E = 0.36 in this fishery. 
RESUMO 
A analise da distribui9ao da frequencia de comprimentos de Copadichromis likomae (Cichlidae) do 
lago Niassa, Mo9ambique, sugere urn comprimento assirnpt6tico SLoo = 14 em, associado a urn valor 
de K de 0,93 ano-1. As rnortalidades total e natural foram estirnadas como sendo 3,2 ano-1 e 1,9 
ano-1, respectivarnente. A analise do produ9ao por recruta sugere uma taxa de explora<;ao E = 0,36 
neste stock. 
59 
60 
INTRODUCTION 
Lake Niassa (i.e., Lake Nyasa or Malawi in English literature) is the most southerly and the least 
studied of the three largest great lakes of Africa. It is about 560 km long and has a greatest width of 
about75 km (Fig. 1). It lies between 9°30'S and 14°30'S at an altitude of about 500 m. The climate 
is tropical. However the lake lies far enough south of the Equator to experience marked seasonal 
variations in wind, temperature, and precipitation (Eccles, 1974). The lake occupies part of the 
southern end of the rift valley system and is to a large extent delimited by faults, particularly to the 
north and on the eastern (Mozamoique) coast. In these areas, the shores are steep and depths in excess 
of 200 m are found close inshore. 
Malawi 
I 
\ 
\ 
\ 
I 
\ 
\._. 
0 20 40 60 SO 100 km 
Tanzania 
~ 
:::J 
o-
.Q 
E 
c 
..... 
0 
~ 
A large fraction of the information on growth 
for African cichlid fishes refers to tilapias. 
However, this group, commercially the most 
important, represents only a small part of the 
adaptive range covered by the Cichlidae 
family as a whole. Another important group 
of cichlids are the haplochromines, of which 
several species are endemic to Lake Niassa 
(see revision of Eccles & Trewavas, 1989). 
They feed on zooplankton and some have a 
well-defined breeding season (Iles, 1971). 
Copadichromis likomae (Fig. 2) belongs to a 
group of zooplankton-feeders known by the 
local fishers as "chisinga". 
First described in the scientific literature by 
lles (1960) as Haplochromis likomae, this 
species is found inshore, over deep rocky 
Fig. 1. Map of Lake Niassa (Malawi) showing sampling grounds throughout the year at all stages of 
area and area of origin of Copadichromis likomae (i.e., 
Likoma Island). growth. Iles (1971) described the growth of 
61 
several small zooplankton-feeding haplochromines 
from Lake Niassa. However, taxonomic problems, 
especially with young individuals (Lewis, 1982) 
have made it difficult to obtain reliable demographic 
Copadichromis likomae 
information on many of the important cichlid species. 
Fig. 2. Copadichromis likomae Iles (1959) from ThefisheriesontheMozambicansideofLakeNiassa 
Lake Niassa (adapted from Eccles & Trewavas, 
1989). are traditional, close inshore and mostly in shallow 
water. The fishers use several types of gears (traps, seines, lines and gillnets) to catch a variety of 
fish species. Few historic data on catches are available in Mozambique, but landings of a "Combinado 
Pesqueiro" (a small fishing enterprise) and of the cooperatives, together with records of effort, are 
now being recorded at Metangula (Fig. 1). Copadichromis likomae is caught primarily with 
"chilimila" nets, a type of small purse seine (Fig. 3 ). 
MATERIALS AND METHODS 
Catch and effort from the Combinado Pesqueiro and the fishing cooperatives were recorded daily. 
A modified chilimila net and two dugout canoes were used to sample the fish. In this process the net 
is carried towards the shoal of fish by water currents; as the foot rope is hauled to the surface, the 
net forms a deep narrow-mouthed bag enclosing part 
or all of the shoal (Jackson et al., 1963). In the 
modified net used here, the mesh size was uniformly 
small at about25-mm stretched measure (the artisanal 
fishers use varying mesh sizes). 
Sampling took place near Metangula, at intervals as 
regular as possible. From January 19 83 to December 
1985 samples were taken more or less daily, as often 
as the lake conditions allowed the boats to operate. 
Overall an average of three or four samples were Fig. 3. Sketch showing the shape taken by the 
chilimila net in the water. 
taken per week. 
62 
Each sample was divided into species, and standard length was measured to the millimeter below. 
In order to improve the interpretability of the data, an artificial year was created by regrouping the 
monthly samples of the three years into one. Also the data were regrouped into 7 .5-mm class intervals 
(Table 1). 
These data were used in conjunction with a modified Wetherall plot (Wetherall, 1986; Pauly, 1986) 
to obtain a preliminary estimate of the growth parameter Leo of the von Bertalanffy equation. A 
preliminary value ofK was estimated using the ELEF AN I program with the Loo value obtained from 
the Wetherall plot as input, and fixed values of the parameters WP (winter point) and C (amplitude 
of the seasonal oscillation), expressing the seasonality of growth (see Pauly, this vol.). Fig. 4 
illustrates the seasonal cycle of surface temperature oscillations in Lake Niassa. Minimum 
temperature occurs in mid-August and hence WP = 0.63. The difference between highest and lowest 
• 0 
mean monthly temperature Is about 4 C; hence C was set at 0.4 (see Longhurst & Pauly, 1987). 
Table 1. Length-frequency and ancillary data on C.likomae sampled from Jan. 1983 to Dec. 1985, regrouped 
in an artificial year, in classes of7 .5-mm total length; lhe last column presents probabilities of capture (see text). 
MI.. /month Jan Feb Mar Apr Jul Aug Sept Oct Nov Dec p 
48.75 1.4 2.0 4.8 18.2 39.8 0.002 
56.25 7.2 7.8 41.4 2.7 23.4 8.4 67.2 88.2 213.9 0.020 
63.75 10.4 15.2 93.8 2.1 45.0 253.4 144.0 145.6 133.9 0.044 
71.25 26.1 32.7 60.3 2.1 68.1 504.0 59.7 73.8 45.3 0.052 
78.75 34.9 53.9 66.5 13.5 73.7 207.6 440.8 74.3 44.4 26.9 0.081 
86.26 51.0 29.4 33.6 12.6 171.6 588.9 551.1 123.0 32.7 93.6 0.151 
93.75 76.8 9.4 48.4 4.0 74.8 1099.1 578.3 160.4 46.5 312.2 0.270 
101.25 80.7 7.8 6.0 26.4 1598.7 389.4 169.2 115.2 622.5 0.515 
108.75 82.9 3.8 1264.1 69.4 82.8 145.2 747.9 1.000 
116.25 39.6 1.5 1354.5 5.1 42.9 34.8 198.6 1.000 
123.75 7.4 3.3 560.3 2.9 13.5 5.4 6.2 1.000 
131.25 3.6 28.8 2.1 6.0 2.1 1.000 
138.75 0.2 0.1 2.2 0.1 1.000 
sum a 417 170 350 37 483 6702 2807 950 750 2443 
a Adjusted to represent number of fish caught per haul. 
Following the estimation of growth parameters, a standard length-converted catch curve was 
constructed using ELEF AN II; this was used only to correct for the effect of gear selection, which 
was performed using the appropriate routine of ELEF AN II. The approximate probabilities of 
capture resulting from this are given in Table 1. The corrected length-frequency data were then used 
u 
0 
J F A M J J A s 0 N D 
Month 
Fig. 4. Average water temperature of Lake Niassa at 10-m depth. Based on Eccles (1974) and 
Degnbol & Mapila (1982). 
63 
for the final estimation of growth parameters and of Z. Then, yield-per-recruit analyses were 
performed, based on both the knife-edge assumption and the actual probabilities of capture. 
RESULTS AND DISCUSSION 
The Wetherall plot gives a value ofLoo close to 14 em SL which is compatible with the size ofthe 
largest fish sampled (see Table 1). 
Fig. 5 illustrates the growth curve derived for C. likomae; from this, three age groups may be 
identified. Given the asymptotic length of SLoo = 14 em, K was estimated as 0.93 year-1, with C = 
0.4 and WP = 0.63. This is consistent with the fact that the surface temperature starts to warm up only 
in September, then continues to increase until April when the southeasterly winds start to influence 
the thermal stratification by cooling the surface and inducing turbulence (Degnbol & Mapila 1982). 
Maximum mixing is achieved by early July. Stratification starts to build up again when the SE winds 
cease. 
A comparison between data for the haplochromines and other cichlids shows that the values of K in 
the former group are relatively high, for their average value of about 0.70 year-1 is rarely equalled 
in the latter (Iles, 1971 and see Table 2). In general terms this indicates that haplochromines grow 
rapidly towards their maximum or asymptotic length; overall however their growth performance is 
low compared to the tilapias (Table 2). 
64 
Tweddle & Turner (1977) described the growth of Haplochromis mloto and suggested that strong 
variations of growth occur between years. Careful examination of their figure, reproduced here as 
Fig. 6, suggests that these variations may in fact be due to seasonal growth oscillations, as considered 
in the present contribution. Tweddle & Turner ( 1977) state that "because of poor growth in the second 
year, it was not possible to calculate a von Bertalanffy growth curve following the method outlined 
by Ricker (1958) using the length at yearly intervals". However, using a fitting method which 
E 
E 
.£: 
-o> 
c: 
~ 
"0 
L.. 
0 
"0 
c: 
0 
<n 
J F 
Month 
Fig. 5. Growth curve of Copadichromis likomae caught in Lake Niassa, as estimated using ELEFAN I. The 
curve has the parameters SLoo = 14 em, K = 0.93 year1, C = 0.4 and WP = 0.63 
Table 2. Growth parameters of selected cichlid species, for comparison with C. likomae. 
Speciesa Area TL00 (em) K cpb Source 
Tilapia galilaea Lake Tiberias 36.0 0.55 2.85 lies (1971) 
Tilapia aurea Lake Tiberias 32.9 0.55 2.77 Iles (1971) 
Tilapia saka LakeNiassa 34.7 0.56 2.83 Iles (1971) 
Tilapia squamipinnis LakeNiassa 34.7 0.56 2.83 Iles (1971) 
Tilap ia zillii Egypt 28.1 0.50 2.60 Iles (1971) 
Tilapia mossam.bica Egypt 38.9 0.56 2.93 Iles(l971) 
Tristam.ella simonis Lake Tiberias 19.8 0.63 2.39 Iles (1971) 
Boulengerchromis microlepis L. Tanganyika 52.9 0.56 3.20 Iles (1971) 
Haplochromis virginalis LakeNiassa 12.1 0.78 2.06 Iles (1971) 
Haplochromis quadrimacu.latus LakeNiassa 19.0 0.65 2.37 Iles (1971) 
Haplochromis pleu.rostigmoides LakeNiassa 14.4 0.76 2.20 Iles (1971) 
Haplochromis mloto LakeNiassa 15.6C 0.52c 2.10 Tweddle & Turner (1977) 
Haplochromis anaphynnus LakeNiassa 19.6 0.671 2.41 Tweddle & Turner (1977) 
Copadichromis likomae LakeNiassa 17.3c 0.93 2.44 This study 
aN ames were not updated and thus Tilapia is used where Oreochromis would be more appropriate. 
bGrowth performance index: $=log K + 2 log Leo (Pauly & Munro, 1984); note relatively low values in haplochromines. 
'l!ased on growth curve in Fig. 6 and the program of Gaschiitz et al. (1980), with C = 0.41 and R2 = 0.964. 
dcorresponding to SL = 140 mm 
150 
..... 
E 
E 100 
.&:; 0 Nomiosi 
-01 t:. South West Arm c 
~ 
• Moldeco 
0 50 
• Monkey Bay 
-0 1-
0 
Aug Dec Apr Aug Dec Apr Aug Dec Apr Aug Dec Apr Aug 
Month 
Fig. 6. Growth of Haplochromis mloto, as derived by plotting models against date (from 
Tweddle & Turner, 1977); note clear indication of seasonality of growth curve (see text). 
65 
explicitly considers seasonal growth oscillation (i.e., that of Gaschtitz et al., 1980) to fit the data in 
Fig. 6leads to TLoo = 15.6 em, K = 0.52, C = 0.4 and a clear minimum in midyear, as for C.likomae. 
The <j)' value corresponding to these estimates (Table 2) is lower than the values for most 
haplochromines so far studied, but not unrealistic. 
The length-converted catch curve for C. likomae (Fig. 7) led to an estimate of Z = 3.2 year-1. The 
estimate of natural mortality obtained using the empirical equation of Pauly (1980) was 1.9 year-1, 
rounded up toM= 2 year-1 for all analysis below. This suggests that F = Z- M = 1.2 year-1, i.e., E 
= EfZ = 0.38. 
The yield-per-recruit and biomass-per-recruit analyses (Fig. 8) suggest, when one uses a realistic 
selection ogive, that the value ofE corresponding to 
a reduction of the stock of C. likomae to half its 
unfished biomass occurs atE= 0.36, corresponding 
to F = 1.1, and that yield-per-recruit is near its 
maximum at E = 0.5. Thus, the C. likomae stock 
reported upon here appears to be fished optimally. 
The results of the yield-per-recruit analysis based on 
the knife-edge assumption suggest that an increase of 
0 
:~0 0 0 °
: ·r 
1.';--------!---:--------!---' 
0 2 
Relative age (years- t0 J 
Fig. 7. Length-converted catch curve for C. 
likomae in Lake Niassa, constructed according to 
Pauly (1990), i.e., accounting for seasonally 
oscillating growth. 
66 
;t: 
:::ll 
..... 
u 
41) 
... 
... 
Q) 
c. 
"0 
41) 
>. 
41) 
> 
-.2 
Q) 
a:: 
1.0 
0.9 
0.8 
0.7 
0.6 
0.5 
0.4 
0.3 
0.1 
0 
0 
Assuming knife---
edge selection 
(with L50= IOcm> 
0.2 0.4 0.6 0.8 
Exploitation rate <E= F/Z) 
1.0 
-:::ll 
..... 
u 
41) 
..... 
..... 
41) 
c. 
Cll 
Ill 
0 
E 
0 
:c 
Q) 
> 
:;: 
0 
Q) 
a:: 
0 
'\'\•-----Assuming knife-
edge selection 
(with L 50= IOcm) 
'\.~---Using actual 
selection curve 
0.2 0.4 0.6 0.8 1.0 
Exploitation rate ( E = F/Z) 
Fig. 8. Yield-per-recruit and biomass-per-recruit analyses for C. likomae in Lake Niassa. Dots indicate present 
state of fishery. 
effort would increase yields, but as also shown in other contributions included in this volume, this 
is but a (dangerous) artifact. 
This preliminary assessment of the artisanal fishery near Metangula will have to be extended to other 
areas and species for verification. 
ACKNOWLEDGEMENTS 
Many thanks are due to staff of the Combinado Pesqueiro for their willing help and collaboration in 
collecting samples. 
I am also grateful to Dr. Daniel Pauly of the International Center for Living Aquatic Resources 
Management (ICLARM, Manila, Philippines) for his help and advice given during the preparation 
of this paper. 
Finally, sincere thanks are due to all those who directly or indirectly contributed to make this work 
possible. 
REFERENCES 
DEGNBOL, P. AND S. MAPILA (1982)- Limnological observations on the pelagic zone of Lake 
MalaWi from 1970 to 1981./n Biological studies on pelagic ecosystem of Lake MalaWi. 
FI:DP!MLWn5/019. FAO Tech. Rep. 1: 5-48. 
ECCLES, D.H.; (1974)- An outline of the physical limnology of Lake Malawi (Lake Nyasa). 
Limnol. Oceanogr. 19(5): 730-742. 
ECCLES, D.H. AND E. TREWA VAS (1989)- Malawian cichlid fishes: the classification of some 
haplochromine genera. Lake Fish Movies, Herten, Germany, 335 pp. 
GASCH0TZ, G., D. PAULY AND N. DAVID (1980)- A versatile BASIC program for fitting 
weight and seasonally oscillating length growth data. I.C.E.S. C.M. 1980/D:6, Statistics 
Cttee., 14 pp. 
ILES, T .D.; ( 1960) -A group of zooplankton feeders of the genus H aplochromis ( Cichlidae) in Lake 
Nyasa. Ann. Mag. Nat. Hist., Ser. 13,2:257-280. 
ILES, T.D.; (1971)- Ecological aspects of growth in African cichlid fishes. J. Cons. ClEM 33(3): 
363-385. 
JACKSON, P.B.N., T.D. ILES, D. HARDING AND G. FRYER (1963)- Report on the survey of 
northern Lake Nyasa, 1954-1955. Jt. Fish. Res. Organ. Government Printer, Zomba, 
Nyasaland, 171 pp. 
LEWIS, D.S.C.; (1982)- Problems of species definition in Lake Malawi cichlid fishes (Pisces: 
Cichlidae). Ichthyol. Bull. J.L.B. Smith Inst. Ichthyol., Special Publication 23. 
LONGHURST, A.R. AND D. PAULY (1987)- Ecology of tropical oceans. Academic Press, San 
Diego, California. 407 pp. 
PAULY, D.; (1980)- On the relationship between natural mortality, growth parameters and mean 
environmental temperature in 175 fish stocks. J. Cons. ClEM 39: 175-192. 
68 
PAULY, D.; (1986)- On improving operations and use ofELEFANprograms. Partlll. Correcting 
length-frequency data for effects of gear selection and/or incomplete recruitment. Fishbyte 
4(2): 11-13. 
PAULY, D.; (1990) - Length-converted catch curves and the seasonal growth of fishes. Fishbyte 
8(3): 33-38. 
PAULY, D. AND J.L. MUNRO (1984) - Once more on growth comparisons in fishes and aquatic 
invertebrates. Fishbyte 2(1): 21. 
RICKER, W.E.; (1958)- Handbook of computation for biological statistics offish populations. Bull. 
Fish. Res. Board Can. 119: 300 pp. 
TWEDDLE, D. AND J .L. TURNER (1977)- Age, growth and natural mortality rates of some cichlid 
fishes of Lake Malawi. J. Fish Biol. 10: 385-398. 
WETIIERALL, J.A.; (1986) - A new method for estimating growth parameters from length-
frequency data. Fishbyte (4)1: 12-14. 


Growth, mortality and yield-per-recruit of Copadichromis likomae (Cichlidae) in Lake Niassa, Mozambique

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Growth, mortality and yield-per-recruit of Copadichromis likomae (Cichlidae) in Lake Niassa, Mozambique

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