One of the paradigms in the management of fish resources is that annual yield is a function of water quality. Consequently, the use of shorthand methods for predicting yields from morphological and /or edaphic factors of the water body are most appropriate for tropical multi-species fisheries. In this study, the morpho-edaphic index (MEI) was used to estimate the productivity of Ologe lagoon (Nigeria). The predicted yield was 73.8 kg ha super(-1) yr super(-1) and a comparison with yields in other African waters showed that Ologe lagoon is highly productive. However, its potential is not fully harnessed due to the traditional nature of the fishin

Akin-Oriola, G.A.

Awokoya, T.A.

Aquatic Commons

PRODUCTIVITY ESTIMATION OF OLOGE LAGOON, LAGOS
By
AKIN-ORIOLA, G. A. AND AWOKOYA, T. A.
Fisheries and Zoology Dept, Lagos State Universi0)
P.M.B. 1087, Apapa Lagos.
ABSTRACT
One of the paradigms in the management offish resources is that annual yield is a function of
water quality. Consequently, the use of shorthand methods for predicting .yields
morphological and/or edaphic factors of the water body are most appropriate for tropical multi-
.species fisheries.
In this study, the morpho-edaphic index (MEI) was used in estimating thee productiviO) of Ologe
ktgoon. The predicted yield was 73.8 kg ha -1 yr -1 and a comparison with yields in other African
waters showed that Ologe lagoon is highly productive. However, its potential is not fitlly
harnessed due to the traditional nature of the fishing.
INTRODUCTION
One of the major features of the West African coastline is the large number of rivers, coastal
lagoons, estuaries, creeks, inland lakes and swamps (Iscandri, 1990).
These support a rich assemblage of aquatic flora and fauna and provide a means of livelihood for
many riverine communities. In order to ensure proper and sustainable utilization of this rich natural
resource, it is necessary to monitor periodically the physical, chemical and biological components of
these ecosystems. The maintenance of essential ecological processes, life support systems and the
preservation of biodiversity has led to the survey of aquatic ecosystems.
Previous investigation (studies) on coastal ecosystems in West Affica include those of Sandison and
Hill (1966), Olaniyan and Fagade (1972), Egborge (1988) and Ajao (1990) on the biota and Lagos
lagoon Biswas (1978), Biney (1990) and Iscandri (1990) studied the ecology and productivity of
Ghanaian and Sierra Leonean coastal systems The present study provides baseline information on
the physico-chemical characteristics, and productivity of Ologe lagoon Lagos.
Study Area
Ologe Lagoon is situated in the south western part of Lagos State lying between longitude 6°27
and 6°30 N and latitude 3°2 and 3°7E with a surface area of 9.4km2 and mean depth of 2.5m
(Odewumi, 1995). It is main source of waster is .River Owo and it opens up to the Atlantic Ocean
via Lagos harbour and Badagry creek (Fig 1). It is surrounded by many fishing villages while an
industrial town-Agbara is situated at the northern border of it. Agbara is the location of a number
industries with agro-allied, chemical and pharmaceutical products.
The lagoon experiences dry and rainy seasons typical of the southern part of Nigeria. The climate
is of the equatorial type with two peak rainy periods which are generally May-July and September -
October. Rainfall is usually heavier during the first peak period about 52% of total rainfall the dry
season lasts from November - April and is characterised by the harmattan brought by the North-
east trade winds.
26
The vegetation around °loge lagoon is characterised by still rooted trees with a dense undergrowth
of shrubs, palm trees and swards of floating grass. The water hyacinth, Eichhomia crassipes usually
covers the edges of the lagoon while floating islands of it occur further out in the lagoon.
Methodology
Five stations (A-E) were selected at the eastern end of °loge lagoon. Stations B and E were
located adjacent to Idolumo village and Agbara industrial estate respectively while C was located in
the midst of the lagoon (Fig. 1).
Sampling was can-ied out on a weekly basis between January and April 1997 usually from 10.00 -
12.00 hours. Water temperature and depth were determined in situ using a mercury thermometer
and a weighted graduated rope. Hydrogen-ion concentration was determined using a Griffin model
40 pH meter dissolved oxygen concentration, carbon dioxide and Total dissolved solids were
detemined following methods described in Boyd (1979) Phosphate, Sulphate and nitrate-nitrogen
determinations were carried out at 690, 420 and 410 nm respectively on an Alpha-4
spectrophotometer.
The morpho-edaphic index (MET) was obtained from the equation:
MEI lotAl dissolved solids (mg,r) (Ryder, 1965)
Mean depth (m)
This index can be converted to yield using the relationship:
Yield 23.4 1V1EI0-42 enderson and Welcomme 1974).
RESULTS
Mean values of physico-chernical parameters of Ologe lagoon are summarized in Table 1. Depth,
temperature, pH and total dissolved solids showed minimal variation during the study.
Temperatures were generally, high ranging between 28°C and 31°C. pH values were neutral and
total dissolved solids were generally low. However, dissolved oxygen and carbon dio-x.ide exhibited
wide fluctuations with the characteristic inverse relationship between them (Fig. 2). Sulphate
concentration were appreciably high while nitrate-nitrogen concentration were extremely low (<0.1
mg1-1) (Fig 3). The morpho-edaphic index of Ologe lagoon was calculated as 15.4 and table 2
shows the relationship between no, potential and actual yields in some African water bodies.
Discussion
Physico-Chemical Parameters
Ologe lagoon is a freshwater lagoon system which is supplied by a seasonal river-River Owo.
Hence the dry season usually heralds an increase in temperatures and reduction water levels. The
water of Ologe lagoon at this period were very dilute with pH being neutral. This may be due to
low tidal influence since the lagoon is more inwardly situated. Egborge (1994) however, reported
salt water intrusion. The photosynthetic activities of plankton and aquatic macrophytes appears to
be responsible for the observed fluctuations in oxygen and carbon dioxide concentrations. Despite
these fluctuations, pH remained relatively stable indicating that the waters are well buffered. The
discharge of effluents into the lagoon from Agbara Industrial Estate may account for the higher
levels of sulphates and phosphates in the water. The low concentrations of nitrate-nitrogen
throughout the study is an indication that it is an irnportant limiting factor of primary production
27
Productivity
The great diversity of species in the lagoon and its use as a breeding ground by marine/brackish
fishes (Anetekhai el al., 1998) makes it imperative to focus attention on the sustainable exploitation
and conservation of the resource. It is therefore necessary to know its potential and actual yields
for management purposes. Ho-w-ever, the small (diagramm figure)xxxx= scale nature of the
fisheries, the lack of time series data on catch and effort and the occurrence of diverse species in
small proportions hinder the use of standard theoretical models in assessing its productivity. The
MEI is a usefiil index in this situation and the highly significant correlation coefficient coupled with
its closeness to actual yields (Tabl.e 2) attests to its reliability. The average productivity of torpical
waters is about 50kg ha' (lscandri, 1990) this the predicted yield of 73.8kghdlyfl suggests that
Ologe lagoon is very productive. However, its productivity is not fiilly utilised because the fishery
is mainly traditional with obsolete fishing gear and craft.
Conclusion
There is need to modernise the fishery of Ologe lagoon to ensure maximum exploitation supply
more protein to the population and increase economic profits (returns) for the fishermen. In
addition, catch and effort data on the fisheiy should be collected.
Acknowledgement
Facilities for the research were provided by the Department of Fisheries and Zoology, Lagos State
University.
REFERENCES
Ajao, E. A. (1990).
Akinyemi, 0. (1987).
Bernacsek, G. M. (1984).
Biney, C. A. (1990).
Biswas, S. (1978).
The influence of domestic and industrial effluents on
populations of sessile and benthic organisms in Lagos
lagoon. Ph.D Thesis, University of Ibadan, Nigeria, 413 pp.
Management of Lake Eleiyele and Lake Asejire Fisheries:
Application of bionomic models. Ph.D Thesis, University of
fbadan, 265p.
Guidelines for dam design and operation to optimize fish
production in impounded river basins (based on a review of
the econological effects of large dams in Africa). CIFA
Tech. Pap. 11: 98p.
A review of some characteristics of fi-eshwater and coastal
ecosystems in Ghana: Hydrobiologia 208:45-53.
Observations on phytoplankton and primary productivity in
Volta Lake, Ghana. Vern. Internat. Verein. Limnol 20:
1672-1676.
28
Iscandri, N. B. (1990).
Karlman, S. (1982).
Odewumi, S.G. (1995).
Biologicl observations on fresh water systems adjacent to
the coast of Sierra Leone. Hydrobiologia 208:63-73.
The annual flood regime as a regulatory mechanism for
phytoplankton production in Kainji Lake, Nigeria.
Lagos State: Location, extent and constituency. In
Fundamentals of General Studies. Noah, A.O.K. (Ed.) Rex
Charles Publications. 114-131.
Olaniyan, C. I. and Fagade, S. O. (1972).
The biology of the West African Shad, Ethmalosa ftmbriata
(Bowdich) in Lagos Lagoon. J. Fish Biol. 4:519-533.
Ryder, R. A. (1965). Method for estimating the potential fish production of north
temperate lakes. Trans. Am. Fish. Soc. 94:214-218.
Sandison, E. E. and Hill, M. B. (1966).
The distribution of Balanus pallidus stutsburi Darwin,
Gryphaea gasar (Adanson) Dautzenberg, Mercierella
enigmatica fauvel and Hydroides uncinata (Philipi) in
relation to salinity in Lagos harbour and adjacent creeks. J.
Amm Ecol. 35:235-250.
29
Egborge, A. B. M. (1988). Salinity and Water hyacinth occurrence in the Lagos
Harbour Badagry Creek System. Proceedings of the
International workshop/seminar on water hyacinth. FMST,
Lagos, Nigeria. 46-51.
Egborge, A. B. M. (1994). Cladocera of costal rivers of western Nigeria. Hydrobiologia
272:39-46.
Henderson, H. F. and Welcomme, R. L. (1974).
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Rome, CIFA Occ. Pap. 1, 19p.
NA-Not Available
Source: Bemacsek, 1984; Akinyemi, 1987.
30
{PRIVA
TE
}Dates
Depth
(m)
Temp
(°C)
DO
(mg')
CO2
(mg')
pH TDS
(mg1-1)
PO4
(mg1-1)
SO4
(mg1-1)
NO3
(mg1-1)
2 / /97 2.41 29.8 8.12 5.74 7.65 37.88 1.30 1.53 <0.1
4/2/97 2.46 30.2 4.92 8.91 7.27 38.97 0.01 2.42 <0.1
18/2/97 2.45 30.4 5.76 7.92 7.63 38.27 0.03 1.70 <0.1
25/2/97 2.45 28.8 7.08 7.33 7.51 38.08 0.23 2.11 <0.1
11/3/97 2.43 29.9 4.36 8.32 7.28 38.50 1.26 1.70 <0.1
18/3/97 2.50 30.0 5.82 10.10 7.53 38.76 0.08 2.34 <0.1
25/3/97 2.45 30.2 7.28 9.29 7.61 38.91 0.80 2.19 <0.1
1/4/97 2.45 30.6 6.40 8.85 7.49 39.09 1.08 2.30 <0.1
{PRIVATE }Waterbody MEI Predicted Yield (Kghdlyr-1) Actual (KghaTlyr-1)
Ayame (Ivory Coast) 10.0 61.6 63.8
Mcllwaine (Zimbabwe) 15.9 74.8 114.0
Volta (Ghana) 6.83 52.4 53.4
Kairiji (Nigeria) 8.88 58.6 58.9
0 .oge (Nigeria) 15.4 73.8 NA
Asejire (Nigeria) 14.0 71.0 89.0
Eleiyele (Nigeria) 29.1 96.4 102.0
Table 1: Mean h sico-Chemical Characteristics of 01 e Latwoii
Table 2: The relationship between ME!, predicted and actual yields in some African
Waters


Productivity estimation of Ologe Lagoon, Lagos

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