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4. CONCLUSIONS AND RECOMMENDATIONS

1. Echo sounder traces indicate that clupeids are present in all parts of the lake in varying degrees of abundance but due to the presence of trees and other obstructions many areas are unsuitable for trawling on a commercial scale.

The highest catch rates were recorded in the southern part of the lake which also contains other requirements necessary for successful commercial operation, i.e. a large area of open water, clear of obstructions, close proximity to an established market, fuel supplies and sheltered landing points.

The open water area is at present relatively unexploited and therefore interference with the existing fishery would be minimal.

This area is recommended as the most suitable for the introduction of a clupeid trawl fishery.

2. Boats for this fishery should be built with adequate beam and fitted with diesel engines for reasons of economy of operation, safety and reliability. Power units may be as small as ten horsepower if fitted with suitable reduction gears to give maximum pulling ability.

If through non-availability of diesels, outboard engines have to be used, boats should he fitted with keels to improve handling characteristics when towing a trawl and reduce sideways drift. (Fig. 14).

Boats should be as evenly matched as possible, preferably with identical engines to ensure that an equal pull is exerted to each side of the trawl. Revolution counters or tachometers fitted to engines give a useful guide to the amount of power being applied and enable engines to be run accurately at the desired speed.

3. The trawling programme is to continue at Kainji Lake Research project, on a reduced scale. A nucleus of trained personnel is therefore available for running courses in trawl construction and handling.

4. The cleared beaches should be sampled regularly, both for data collection and for demonstration purposes. Local fishermen interested in beach seining may be given assistance with regard to net construction and encouraged to use the beaches at all times.

5. Monofilament/multifilament gill net trials may continue but at this point it seems doubtful that the increased catches of monofilament nets are sufficient to offset the high initial cost of this material. The North West State Government, through the fisheries division is about to distribute numbers of monofilament gill nets to fishermen as part of a compensation programme. This exercise should provide a satisfactory assessment of the ability of this material through direct use by the commercial sector.

Table 1

MID-WATER TRAWL WITH 12 mm COD-END WEIGHT IN GRAMMES
Catch in Weight of Fish Captured by 12 mm Mesh Cod-end during the Month of October 1973

StationsJetty Water Intake
A		Jetty Water Intake
A		Jetty Water IntakeShagunuFoge IslandFoge IslandOld BussaJetty Water IntakeJetty Water IntakeJetty Water IntakeTotal
Dates3.10.734.10.735.10.739.10.7310.10.7311.10.7312.10.7319.10.7322.10.7323.10.73 
No. of Fulls5432212221 
Clupeidae23 5708 4365 275701 9007 0006208 4102 9901 34559 616
Schilbeidae13 40011 6793 9552 4013 8255 0002 1005 7852 8953 51054 550
Mochocidae---13 9004 4708 500----26 870
Others6 8858088141 9253 6983 2002 2601 2355012 40223 728
Lates niloticus20 000---------20 000
Total63 85520 92310 04418 29613 89323 7004 98015 4306 3867 257184 764

Table 2

MID-WATER TRAWL WEIGHT IN GRAMMES
Catch in Weight of Fish Captured by 9 mm & 6 mm Cod-end during the Month of December 1973

Stations9 mmCod-end   6 mmCod-end 
Jetty Water IntakeAmfani BayAmfani Bay
Water Intake		Jetty Water IntakeAmfani BayJetty Water IntakeJetty Water IntakeCoffer DamAmfani BayAmfani Bay
Dates4.12.735.12.736.12.737.12.7311.12.7312.12.7313.12.7314.12.7319.12.7320.12.73
No. of Pulls2332232121
Clupeidae1700080 000139 00034 500164 000162 34087 00058 50086 50087 000
Schilbeidae----300430426160--
Others1 5002 5004 2502 7751 92070460140--
Total1850082 500143 25037 275166 220162 84087 88658 80086 50087 000

Table 3

RESULTS OF THE EXPLORATORY MID-WATER TRAWLING PROGRAMME

Stationkg per hour  
Jetty/water intake83  
Amfani Bay94Southern Sector
Garafini50average 70 kg/hr
Old Bussa53 
Gafara50 
Middle42Main Basin
Ulahira48average45 kg/hr
Shagunu45 
Papiri40 
Mahuta30Northern Sector
Rofia64average47 kg/hr

Fig. 1. MIDWATER TRAWL NO. 1

4 PANELS

Fig. 1
Fig. 2

Fig. 2 RIG GING & TOWING ARRANGMENT.

Fig. 3 MIDWATER TRAWL NO. 2

4 PANELS

Fig. 3

Fig. 4 MIDWATER TRAWL SUITABLE FOR COMMERCIAL USE

4 PANELS

Fig. 4


Fig 5.(a)5.(a) MIDWATER PAIR TRAWLING (The codend is thrown into the water and the remnant of the gear shot while the two boats maintain a straight course)

5.(b) MIDWATER PAIR TRAWLING (The boats are separating just after shooting the net)Fig 5.(b)

Fig 5.(c)5.(c) MIDWATER PAIR TRAWLING (Last phase of shooting. The headline is still visible at the surface)

Fig 6.(a)6.(a) MIDWATER PAIR TRAWLING (15 hp units towing midwater trawl. One wooden planked boat built at project. One glass fibre Yamaha 18 ft)

6.(b) MIDWATER PAIR TRAWLING (Hauling the midwater trawl - 15 hp units - the two big floats mark the upper wing tipsFig 6.(b)

Fig 6.(c)6.(c) MIDWATER PAIR TRAWLING (Last phase of hauling. The codend with catch is hoisted overboard)

Fig 7.(a)7.(a) MIDWATER PAIR TRAWLING (Echo sounder of SEA ROVER passing over trawl in action. Head-rope at 11 m. Foot-rope at 18 m. Net opening height is 7 m)

Fig 7.(b)7.(b) MIDWATER PAIR TRAWLING (The warp length is adjusted so as to maintain the midwater trawl at the level of the fish traces)

Fig. 8. MAP OF KAINJI LAKE

Fig 8
Fig 9

9. UNDERWATER TOPOGRAPHY - as recorded by echo sounder showing old river bed and submerged trees (indicates narrow section of old river bed with tree-lined banks; fish echoes between 3 m and 7 m approximately)

Fig 10.(a)10.(a) BEACH SEINING (Beaches cleared at low lake level may be used for beach seining as the water level rises)

10.(b) BEACH SEINING (Rowing bost with net board across transom simplifies the work of shooting the beach seine which when operated from a canoe required the work of four men).Fig 10.(b)

Fig 10.(c)10.(c) BEACH SEINING (Exposed sand banks in the Foge Island area provide suitable sites where beach seines may be used during the low water period).

Fig 11.(a)11.(a) BEACH SEINING (In the later stages of the haul, many fish are lost over the headrope)

11.(b) BEACH SEINING (The headrope is lifted above water as an attempt to prevent loss of fishFig 11.(b)

Fig 11.(c)11.(c) BEACH SEINING (Typical catch of Tilapia at Foge Island beach seine with 100 mm mesh size in bunt).

Fig. 12 TILAPIA BEACH SEINE

Fig 12
Fig13
Fig14

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