KAINJI LAKE, NORTHERN NIGERIA, 1996 by T.A

ISSN: 1119-1449 Nigerian-German Kainji Lake Fisheries Promotion Project Technical Report Series 6.

-17=TAKT-7-, ,-,1111111VW"'7.re7,' ,A321111-T- FISHING GEAR SURVEY OF KAINJI LAKE,LAKE, NORTHERN NORTHERN NIGERIA, NIGERIA, 1036 ros by T.A. DU FEU, 0.S. ABAYOMI AND M.D.B. SEISAY

Nigerian-German (GTZ) Kainji Lake Fisheries Promotion Project firmit.o,

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March, 1997 ISBN 978-037-005-6 © Nigerian-German (GTZ) Kainji Lake Fisheries Promotion Project New Bussa Niger State Nigeria ISSN: 1119-1449 Nigerian-German Kainji Lake Fisheries Promotion Project Technical Report Series 6.

FISHING GEAR SURVEY KAINJI LAKE, NORTHERN NIGERIA, 1996 by T.A. DU FEU, 0.S. ABAYOMI and M.D.B. SEISAY

Nigerian-German (GTZ) Kainji Lake Fisheries Promotion Project

March, 1997

Acknowledgement

Our thanks are expressed toto thethe staffstaff ofof the NationalNational Institute forfor Freshwater Freshwater Fisheries Fisheries Research (MEER), (MEER), Nfr.Mr. \V. Omorinkoba,Omorinkoba, K.K. Appolonius,Appolonius, A. A. Francis, Francis, andand J.J. Odey for their co-operation during the survey.

\Ve alsoalso wish to thank. NfallamNIallarn Naniaaa,7.\laniaaa, Mallam Nfallam Dole Dole anci and MaIlamYaro Yaro from from Kebbi Kebbi and and NigerNiger State FisheriesFisheries DivisionsDivisions forfor their their assistance assistance duringduring thethe annualannual geargear survey.survey.

Our gratitude also extends toto thethe EmirsEmirs of-Borgriof Borgri andand Yauri, thethe VillageVillage Heads Heads andand thethe fishermen around thethe LakeLake forfor their moral support and co-operationco-operation duringduring the suivey.suivey.

FislOng GearGcar Snr e. Kainji Lake. Northern Nigeria. 1996. Page Summary

The survey was Carrcarried ied out out in in September September 19961996 alongsidealongside the annual frame survey. AsAs inin thethe previous surveys, therelvere sixsix mainmain fishingfishing geargear typestypes inin useuse Oilon the lake. These included gill nets, drill nets, beach seines, cast nets, longlines (baited and foul hooking) and fishing traps.

A total of 813 canoes were sampled. The canoe lengths were similar to the previous gear surveys.

Altogether 466 gill nets were measured. They had an average length of 149 ni.,in., and were mostly bottom set. Of the gill nets measured 68% had a mesh size below 3 inches; the minimum mesh size allowable according to the Niger and Kebbi State Fisheries Edict, 1996. Of concern was the large increase in the number of 1 inch meshed nets recorded on the lake.

DODrift nets nets had had a amean mean length length of of 74 74 ni. m. A A total total of of 88% 88% of of all all drill drill nets nets measured measured hadhad aa meshmesh size below 2.5 inches, the minimum mesh size stipulated in the State Edict.

A total number of 102 beach seines were sampled with a mean length of 110 ni,in, the mesh size in use on thethe lakela.ke remained remained as as 0.1 0.1 inches.. inches.. Under Under the the Edict Edict beach beach seines seines are are banned banned Fr0111 from fishing on Kainji Lake. The decline in the lengths of the beach seines (and therefore catch rates)rates) recordedrecorded sincesince 19951995 waswas encouragingencouraging inin lightlight ofof thethe destructivedestructive naturenature ofof thesethese nets.nets.

A total of 30 cast nets were sampled, they had a mean diameter of 9.8 ni.m. and a mean mesh size of 1.9 inches.inchesAll the nets had a hanging ratio of 0.5. Of the cast nets measured 40% had a mesh size below the minimum size of 2 inches recommended by the State Fisheries Edicts. orOf concernconcern waswas thethe continuedcontinued riserise inin thethe number of gill nets with mesh sizes less than 2 inches.

There were two types of longlines in operation on the lake: the baited and the foul hooking longlines. They were mostly bottom set and the hook size nos. 12-14 (Kirby sea hook) were predominant

Two types of fishing traps werevere identified,identified, one was covered with a mesh of thin cane, one with netting material. The fishingfishing trapstraps liadhad aa meanmean heightheight ofof 0.80.8 M.ne and a mean width at the vase of 0.53 ni.ni TheThe meanmean mesh size used was 0.860,86 inches.inches.

CitharilmsCitharinus vas reported as the most targeted of all fish species on the lake. SynodontisSynadolitis membrarraceousmembranaceous waswas alsoalso targeted by most gears especially the smaller meshed nets. Labeo and 7ila1ia7ilopia were low on the list of targeted species but their incidence remains high in the catches.cat ches.

Fishing Gear Survey. Kainji Lake,Lake. Northern Nigeria, 1996, Page 2 Table of Contents

SUMMARY 2

INTRODUCTION 5

METHODS 5

3, RESULTSRESULTS 6

3.1. F1S11111G1 s111NG CANOES CANOES 6 3.2.3,2.RS1HNGHSI IING GEARS 7 32.1.GinGi11 Nets Nets 3.2.2.Drift Nets 10 3.2.3.Beach Seines 11 3.2.4.Cast Nets 12 3.2.5.Longlines 14 3).6.32.6.Fishing Traps 15 3.3.TAR(11:1'TARCEF SPECIFS SPtJFS 16 REFERENCES 19

GLOSSARY 20

Fishing Gear Stiri,e.Stiri,e, Kainjikaiini Lake,Lake. Northern Nigeria,Nigeria. 1996. Page 3 List of Figures

Figure I.The Distribution ofof Canoe Canoe LengthLength (meters)(meters) RecordedRecorded during the 1993-1996 Fishing Gear Sun eys.eys. KainjiKainji Lake 6 Figure 2.The Distribution ofof GillGill Net Net Headline Headline Length Length (meters) (meters) Recorded Recorded during thethe 1993-1996 Fishing Gear Surveys.Surveys. KainjiKainji Lake. 9 Figure 3.The Distribution ofof GillGill Net Net Mesh Mesh Sizes Sizes (inch)(inch) Recorded Recorded duringduring thethe 1993-1996 Fishing Gear SunSul, eys.evs. KainjiKainji Lake 9 Figure 4.The Distribution of DriflDrill Net Net Mesh Mesh Sizes Sizes (inch) RecordedRecorded duringduring thethe 1993-19961993-1996 Fishing Fishing Gear Surveys.Surveys. KainjiKainji Lake. 10 Figure 5.The Distribution of of Beach Beach Seine Seine HeadlineHeadline LengthLength (meters) (meters) Recorded Recorded duringduring the the 1993-19961993-1996 Fishing Gear SunSur\ eys,evs, Kainji Kainji Lake. 12 Figure 6.The Distribution ofof Cast Cast NetNet MeshMesh SizesSizes (inch) RecordedRecorded during the 1993-1996 Fishing Gear Suneys.Sur\ evs. Kainji Kainji Lake. 13 Figure 7 The Distribution ofof MeshMesh SizesSizes (inch) of FishingFishing TrapsTraps Recorded duringduring 1993-1996 FishingFishing Gear Surveys,Surveys. KainjiKainji Lake. 15

List of Tables

Table 1 The Percentage of of Illegal Illegal Gill Gill NetsNets onon KainjiKainji Lake. 8 Table 2.The Percentage of of Illegal Illegal Drill Drill Nets onon KainjiKainji Lake. 11 Table 3.The Percentage of of illegal Illegal CastCast Nets Nets on on Kainji Kainji Lake.Lake, 13 Table 4The Distribution of BaitedBaited Longlines Used on KainjiKainji Lake,Lake. 1993- 1996,1996. 14 Table 5The Distribution of Unbaited (foul(fouHiooking) hooking) LonglinesLonglines in UseUse on Kainji Lake.Lake, 14 Table 6.The PercentagePercentage of of Illegal Illegal FishingFishing TrapsTraps onon KainjiKainji Lake. 16 Table 7.Target Species andand SpeciesSpecies Caught Caught Listed Listed inin OrderOrder of Importance (summed(sununed for allall geargear types). 17 Table 8.The Target Species ListedListed inin Order with PercentagePercentage OccurrenceOccurrence forfor Legal and Illegal GearGear Types 18

Fishing Gear Survey.Survey. KainjiKainji Lake. Northern Nigeria. 1996. Page 4 . Introduction

-1The lie annual annual fishing fishing gear gear survey survey of of Kainji Kainji LakeLake waswas conductedconducted inin September, 1996 together with the annual framefiame survey

There have been 3 gear surveys pre\previously iously performed on the Lake by the Nigerian- German Kainji Lake Fisheries Promotion Project (du Feu, 1993; Yisa et al, 1994 and du Feu, 1995).

The purpose of the survey was to obtain and compare with previous surveys, the characteristics of the fishing gears in use on the lake. The survey also determined the targeted fish species for each gear type and the percentage of illegal gears operating on the lake.

N.teasurements teasurements of of the the gears gears will will assist assist in in the the standardisation standardisation of of units units ofof fishingfishing efforteffort usedused during the frame survey and catch and effort monitoring. The information obtained frotnfrom the analysis could assist in the formulation,formulation, anciand monitoring the effectiveness of, management measures so far introduced for the Kainji Lake fishery.

2.Methods

The methodology of the fishing gear survey was the same as the previous surveys described by du Feu, 1993, Yisa et. al., 1994, du Feu 8z-ez- Kasali, 1995.

Like the previous surveys the 1996 gear survey took place in September \vhilstwhilst the lake water was rising.

Alternate villages around thethe lakelake werewere visitedvisited andand thethe follo\vingfollowing measurementsmeasurements werewere takentaken from fishing gears found in houses or on the beaches: canoe length, net headline length, net depth, stretched mesh size, twinetwine size,size, netnet hanginghanging ratio,ratio, distancedistance bet\veenbetween hooks,hooks, hookhook snoodsnood length.length, fishing trap height and width.

The data VvaSwas entered entered into into the the fishing fishing gear gear database database (du (du Feu, Feu, 1996)1996) forfor analysis.analysis. SPSSSPSS software wasvas usedused toto perform the statistical tests.tests

Fishing Gear Survey. Kainji Lake. Northern Nigeria,Nigeria. 1996. Page 5 3.Results

3.1.Fishing CanoesCanoes All the canoes sampled were made up of wood planks and locally built in Malale, Kokoli, Ulaira and Yauri.

The number of canoes sampled was 813. The majority are designed to be paddled (87%) as opposed to motorised with an outboard engine (13%). Motorised canoes were mainly used by the beach seine fishery (66% of all canoes), whilst the gill net and fishing trap fisheries rarely used motorisation (7%). The cast net, longline and drill net fisheries hardly ever used engines (2%).

Paddled canoes hadliad aa lengthlength rangerange ofof 5.05.0 -11.8-11.8 IIIin. andand meanmean length of 6.9 in.m. (95% Cl;Cl; 6.88-6.88- 6.99). Nlotorised canoes were longer and had a mean length of 9.6 m.ni. (95% Cl;.C.I; 6.88-9.99).6,88-9.99), TheieThete was no evidence that the mean length of the motorised and the paddled canoes had significantly changedchanged from from 1993 1993 to to 19961 1996..

The distribution of canoe lengths is shown in figure I.1. ApartApart fromfrom thethe 7-7.997-7.99 metermeter sizesize classclass which showed a rise in numbers no variation was seen within the other size classes.

The fishing canoes constructed locally are cheap to buy and hare a long life span. l'he canoes are particularly robust and the small draft (depth in the water) allows the fisherntan access to the shallow areas ofof the lake. At present the large width planks needed fsor construction are still available and unless this becomes a problem the NGKLFPP sees no justificationjustification toto alteralter thethe typetme or the design ofof thethe canoes.canoes.

Figure 1.The Distribution of Canoe Length (meters) Recorded during the 1993-1996 Fishing Gear Surveys, Kainji Lake.

5.0-5.99 6.0-6.99 7.0-7.997,0-7,99 8.0-8.99 9.0-9.99 canoe length (meter)

I Mann-Whitnel,Nlann-Whitney UU test:test: \\\ \here here groups groupsof ofmotorised motorised and and paddled paddled areare testedtested separately.separately. P= 0.66 and P=0.39P=0,39 res.res.

Fishing Gear Survey,Surre\ KahniKainji Lake, Northern Nigeria, 1996.1996, Page 6 3.2.Fishing GearsGears The main fishing methods used by the fishermen on the Lake included Gill(.301 netsnets priR1)riR netsnets Beach seines (:astCast nets Longlines Fishing traps.traps

3.2.1.Gill NetsNets The gill net is a passive gear that captures fish by entanglement or gilling.Oiling. It is especially effective for the fish species whichw:hich are are adorned adorned with with spines. spines. The The gear gear is is usually usually set set overnight overnight with the catch collected in the morning.

['AiringDuring, the 1996 gear survey, a total of 466 gill nets were measured. The nets had length range of 30- 500 M. with a mean length' of 149 ni.in. (Std.-- 91.6). The mean headline length of gill nets liadhad increased by an average of 16% during every year fromfi-om 1993 1993 and and was was significantly significantly longer in 1996 from all the previous sut-veys'. Figure 2 shows that the most frequently used net len,gthlength waswas oneone bundlebundle long.long. TheThe meanmean depthdepth of gill nets in 1996 was 2.34 ni. A hanging ratio of 0.5 wasvas usedused forfor thethe netsnets throughoutthroughout thethe lake.

The mesh sizes recorded for gill nets varied between 0.5 to 10 inches with the most commonly used nets having a mesh size ofof 2.0-2.0- 2.52.5 inchesinches (Figure(Figure 3).3). TheThe meanmean meshmesh size size was was 2.4 2.4 inches inches (Std.(Std.= 1.36), 1.36), this this vas was significantly significantly lower lower (P=0.00)4 (P=0.00)4 than than thethe meanmean meshmesh of 2.8 inches recordedrecorded in 1995 but not significantly lowerlower (P=0.09)4(P-0.09)4 thanthan 2.6 inches recorded in 1993.

hiereThere is is no no evidence evidence that that the the number number of of large large I meshedneshed netsnets Yoto targettarget largelarge CitharinusCitharinus andand Lates is increasing. As outlined in previous reports (du Feu, 1997) these large fish are re,sponsibleresponsible forfor thethe highhigh recruitmentrecruitment andand sustainingsustaining thethe catchescaches of the small meshed gears. UntiLfurtherUntil f-urther informationinformation aboutabout stockstock sizessizes isis obtainedobtained it would be unwise to support a growth in the large meshed nets,nets, whichwhich maymay leadlead toto lowlow recruitmentrecruitment duedue toto overlishingovolishing of the parent stock.

Based on the State Fisheries Edicts which states that only gill nets with mesh sizes 3 inches or above should be used on the lake, 68% of this gear wasvas illegalillegal inin 19961996 (Table(Table 1).1). ThisThis impliesimplies that the majority of nets in use target juveniles or immature fish which is dangerous for the sustained exploitation of the lake fisherv.fishery. The number of legal and illegal nets sampled during the surveysttrvey variedvaried significantlysignificantly duringduring thethe yearsyears bet\veenbetween 19931993 toto 19965.1996. Nets Nets ofof differentdifferent meshmesh sizes were occasionally joined together to make a fleet which was then set as one unit.

2 5% trimmed mean 3 Mann-Whitney U test. P=0.00 for the three tests 1996 to 1993. 1996 to 1994 ez. 1996 to 1995 I Mann-Whitney U test s Chiad square square test.test. P=0.t)t)P=0.00

Fishing Gear Survey. Kainji Lake.Lake, Northern Nigeria, 1996. Page 7 Of concern is (hethe increased use of undersized meshedmeshed itnets; particularlyparticularly one inch meshmesh lids:lets whichwhich increasedincreased fromfrom 6% Yo 21 %%from from 19951995 toto 1996.1996. TheThe nets are especially destructive since they are allall constructedconstructed withwith nylonnylon (trinetrine whichwhich makesmakes themthem very qfficientefficient inin entanglingentangling:juveniles. juveniles. The NGKLFITNGKLFP.P should should highlight highlight this this area area during during enlightenment enlightenment campaigns on the use of undersized meshed gill nets.

The'The twinetwine sizesize recordedrecorded forfor the netting material was 6 ply (27.7%), 9 ply (70,8%) andand 1212 plyply (1.3%). The nets had widely spaced mountings of the sheet netting material to the head and foot topes

The twine usedused forfor thethe constructionconstruction of of the the 11 lletS et s is is very rely thin. IVith the wide spaced mounting ofof thethe netting'toting material along thethe headhead andand potpot ropes ropes used used am' am' fish fish coming coming imito into contact with thetire netnet willwill hebe easilyeasily entangledentangled byby thethe thinthin twinetwine andand thethe looseloose 'pockets''pockets' ofof netnet. Jrfrhen hen formulatingformulating meshmesh sizesize regulationsregulations forfor thethe gillgill netnet fisher),fishoy thisthis was into account since within Kainji Lake thethe Jis!:fish are more likely to become tangled than gilled asas inin conventionalcom.entional gill nets.

As in the previous surveys 53% of all nets were bottom set \vhilstwhilst 46%were surface set, the remaining 1% were both surface and bottom set. The type of settingsettinu used varies with the season

Table 1.The Percentage of illegal Gill Nets on KainjiKainii Lake, Fishing Gear Survey 1993- 1996.1996

Year We al nets (%) 1993 66 1994 47 1995 54 1996 68

Fishing Gear Survey, KninjiKainji Lake, Northern Nigeria, 1996,1996. Page 8 Figure 2.The Distribution of Gill Net Headline Length (meters) Recorded during the 1993-1996 Fishing Gear Surveys, Kainji Lake.

60 1993 50 M 1994 DCI 19951995 40 1996

lo10

'70170 6'oN 6o,.., 70070:0 7207,D0 79'0 76-, 76, 0'0 D26. `D370 0,9 79'0 76b 760 `Doo, `17o.. 9 T7 76, L.To "9 '709 279 200 7,9 '7,9 .cp7t99 9 s'pOtp9 Headline length (meter)

Figure 3.The Distribution of Gill Net Mesh Sizes (inch) Recorded during the 1993- 1996 Fishing Gear Surveys, Kainji Lake.

Illegal MeshMesh SizesSizes Legal Mesh 40 1993 35 o M 1994 ;.:30 .0 El 1995 25 (.7) El 1996 20

12 10 ri 5

7.6a ,5*o o,0 o 719 7'50'77.99 -5t s9 19 99 19'299'19 99 1.0,5t.99.99 Mesh Size Groups (inches)

Fishing Gear Survey.Survey. KainjiKainji Lake,Lake. Northern Nigeria, 1996. Page 9 3.2.2.Drift NetsNets The drift net is an active gear thatthat isis usedused inin thethe riverineriverine sectionsection inin thethe notnoith th of the lake. It's use is however becoming prominent in the still water lacustrinelacusti ine areasareasof the central and southern basins (Apeloko && dudu Feu,Feu, i1996). 996),

A total of 122 nets \verewere measured. The length of the drifl nets had a mean6 of 74.2 m. (Std. 389) The depth of the nets varied between 2.5 and 20.8 ni. with a mean of 8.8 (Std(St(' 3.2)

The mesh sizes recorded varied between 0.5 and 6.0 inches with a mean of 1.68 inches ( Std.-- 0.88). The mean mesh size recorded vas significantly smaller than 1995 (P-0,00)7 but not significantly differentdifferent fromfrom thethe meanmean mesh mesh size size of of 1993 1993 (P=0.07)5 (P=0 07)5or or 1995 1995 (P---0.20)7. (P---020)7. TheThe drift net fishermen do not mix bundles of different meshes within the fleets as in the gill net fishery.

About 88% of drifl nets operated onon thethe lakelake werewere illegalillegal (-Fable(Table 2). There was strong evidence that the number of illegal drifl nets varied between years'. The distribution of the mesh sizes recorded for the 1993-1996 gear surveys is shown in Figure 4.

The nets werevere commonlycommonly surfacesurface setset andand made of 6 ply, 9 ply and 12 ply twine with a hanging ratio of 0.5.

Figure 4.The Distribution of Drift Net Mesh Sizes (inch) Recorded during the 1993- 1996 Fishing Gear Surveys,Surveys, KainjiKainji Lake.Lake.

40mill..11.11411111111=111MERERiiimummeal I199301993 35 M 19941994 ri, 30 1 ...s...... 019950 1995 25 [31996El 1996 20 15 10 5 M1ilrm.I Elk E Loam.NI: -desuh stIzes11----÷. .0'r I5O7 979 os9 Mesh size groups (inches)

6 5% trimmed mean Mann-Whitnev U test Chi squarespate test. test, P-0.00P-0.00

Fishing Gear Survey, Kainji Lake, Northern Nigeria, 1996. Page 10 Table 2.The Percentage of Illegal Drift Nets on Kainji Lake, Fishing Gear Survey 1993-1996.

Year life al nets (9-'6) 1993 93 1994 98 1995 8? 1996 88

3.2.3.Beach Seines This fishing gear vas specifically designed and introduced by the fishermen to catch the small pelagic clupeid fish species , However, during fishing the small meshed encircling net, which is pulled towards the sliore,shore, also captures the juvenilesjuveniles ofof otherother commerciallycommercially importantimportant fishfish species e.g. e.g. (71110:111110% Cithuri/rus, Tilapia. Tilapia. Lates Lates etc.etc

The basic principlepiinciple of operation of this gear has been described by du Feu, 1993. Fishing with beach seines usually starts by 6.00 am. and can extend into the night. Because of the nets bulk it requires a lar,_ger canoe to set it.Beach seine fishermen are highly mobile migrating around the lake. About 66")/066°/0 of of the the canoescanoes werewere recordedrecorded asas beingbeing motorised,motorised, higherhigher thanthan for any other gear.

A total number of 102 samples of beach seines were sampled with a length range of 30-200 in. and a mean length' of 110 m. (Std.= 42) (Figure 5). Despite a significant increase in the length ofof thethe netsnets recordedrecorded from from 1993 1993 to to 199611', 1996r, there there is is evidence evidence thatthat thethe beachbeach seines became shorter from 1995 to 19961'

Catch rates and hence by-catch increaseincrease asas beachbeach seinesseines becomebecome longer.longer lfith the(he ban o beach seines it may be that fishermen are reluctant to 'add on bundles of beach seine netting as they did in the past.past ShorteningShortening ofof beachbeach seine nets can therefOre be viewed as beneficial to the fishery.

The net depth varied between 2.00-9.602.00-9.60 M.m. with a mean of 5.225.22 in,ni. (( Std.=Std.= 1.39).1.39), TheThe meshmesh 51Z0 remained as 0.1 inches. As stipulated in the Niger and Kebbi State Fisheries Edicts beach seines are banned on Kainji Lake.

5')/0trimmeci trimmed meanmean Manii-ViltitnevMarni-Whitnev U test.tesi. p=().01 Mailn-WhittICvNiams-Whitilev U U test. test. P--,1).1)(1 P-1).1)(1

Fishing GeorGear Survey. Kainji Lake. Northern Nigeria.Nigeria, 1996. Page 11 Figure 5,5.The Distribution of Beach Seine Headline Length (meters) Recordedduring the 1993-1996 Fishing Gear Surveys, Kainji Lake,Lake.

45 U.1993U1993 40 o IN 1994 35 30 0 1995 25 0 19961996 20

E15 uu- 1010 a) a_ 5

57, eso C ,q, 7,, 7vo 700 'Po 0 "t9 , '77,9 '7 s7 '7 Beach seine headline iength (meters)

3,2.4.3.2.4.Cast Nets The nets are of small mesh and circular in shape with lead weights attached around the outer circumference. The net is either cast from the shore or from a canoe. As it sinks to the bottom the weighted edge sinkssinks moremore rapidlyrapidly thanthan thethe centrecentre svithwith the net entrappingentrapping anyany fishfish beneathbeneath it. When hauled using the center rope the net closes, the pockets and lines around the outer edge help to ensure that the fish are trapped. Cast nets are usually fished for 2-8 hours per day.

A total number of 30 cast nets were sampled. Despite anati increase recorded in the mean mesh size from 1993 it fell sharply from 1995 to 199612. In 1996 the mesh sizes ranged from 0.5-4,00.5-4.0 inches svith a mean of 1.92 inches (Std.= 0.93),0,93),

The distribution of the cast net mesh sizes over the 4 years gear surveys is shown in Figure 6.6, The graph shows a sharp rise in the number of nets of 1 to 2 inch mesh in use from 1993 to 1996, whilst the numbernumber ofof netsnets above 2 inchesinches fellfell TheThe most commonlycommonly usedused netsnets onon the lake in 1996were the ones with mesh sizes below 2 inches, unlike 1995 when\\lien thethe majoritymajority ofof netsnets used had a mesh size higher than 2 inch.

The minimum allowable stretchedsti etched meshmesh sizesize isis 2.02.0 inchesinches (State(State FisheriesFisheries Edict,Edict, 1997),1997), thethe percentage of illegal nets is shown in table 3. There is evidence that the number of illegal cast nets recorded on the lake were significantly different between the years".years",

121 2 Significant,Significant. P---(1.t12.Mann-Whitney N1ann-Whitnev U U testtest 131 3 ChiChi squarescriare test.test. P,--0.01P-0.1)1

Fishing ClearGear Surve,Survey, Kainji Kainji Lake. Lake, Northern Northern Nigeria,Nigeria, 1996, Page 12 The most h»portantit»portant Fishfish species caughtcautzlit by by cast cast nets nets are are Citharinus Citharima and Tilapia. ItIt has been estimated that 31% by number of each these species is caught every year by the gear on the lake and these are mainly undersized fish (du Feu, 1997). Like the beach seine, cast nets cause high mortality of juvenile fish,

Cast tietnet efficiency can bebe inctinct easedeased byby usinizusing larRerlarger diameter nets; there is however aa limitlimit toto the size of net which can be effectively spread when thrown. The cast net diameter has inct eased since 1993 and the 1996 mean diameter (9 8 tu.) was significantly higher than any preceding years recordsli

The increased use ofof small meshed castcast netsnets since since 1993 1993 which which areare usedused to to targettarget juvenilesjuveniles of the mainmain commercialcommercial species, species, Citharinus °Marlin's andand Tilapia, Tilapia, is is ofof major major COnCelllCOnCelll andand shouldshould be addressed byby thethe enlightenmentenlightenment campaigns of thethe AVKLF1-1),AVKLFPP

Figure 6.The Distribution of Cast Net Mesh Sizes (inch) Recorded during the 1993- 1996 Fishing Gear Surveys, Kainji Lake.

50 45 Illegal Mesh Sizes Legal Mesh sizes E119931993 o 4.7, 40 1994 IDEl 1996.1996- f. 19961996

7 7 0 t5?, 0 0 0 .? 7 '7 srg,719 9 qp srsSr0 . 90 Mesh size groups (meters)

Table 3.The Percentage of Illegal Cast Nets on kainjiKainji Lake,Lake, Fishing Gear SurveySurvey 1993-1996,1993-1996.

ear-ear nets (%)(%) 1993 40 1994 13 1995 37 1996 40

I' -Hike\-Hike\ ss honestihonesti significant testtest

Fishing Gear Surs ey.ey. KainjiKainji Lake,Lake. Northern Nigeria,Nigeria. 1996,1996, Page 13 3.2.5.Longlines LonglineLong.fine are are passive passive gearsgears withwith thethe mainmain Uneline bearing many hooks onon snoods.snoods. TheyThey areare quitequite selective for species and to a considerable extent for fish size. The longlines may be baited or unbaited (foul hooking longline) They are normally set in the evening and titled for checking in the morning.

A total number of 88 baited longlinestonalities were sampled. The hook size number ranged from 7-14 (Kirby sea hook) with a mean of 12.95. The distance between hooks varied between 1.6- 4.5 111.,(mean (mean 3.42 3.42 ni.), 111.), the the snood snood length length varied varied from from 0,1-0.3 0,1-0.3 m. ni. (mean (mean 0.20 0.20 m.),m.),

Longlines with baited hooks \versewere all all bottom bottom set. set. The The number number ofof hookshooks variedvaried betweenbetween 24-50024-500 per line with a mean of 88.67 hooks. The hook size distribution for baited linestines is shown in table 4. The most frequently used hooks on the lake were the smaller ones with sizes 12,13 and 14.

For the foul hooking longlines 78% verewere bottombottom set,set, 19%19% werewere surfacesurface set,set, whilewhile 3%3% werewere both bottom and surface set. The number of hooks ranged between 50- 612 per line. The distance between hooks was 0.2-4.8 ni. The hook size varied between 7-14 (Kirby sea hook) with a mean of 12.7 (Table 5). The snood length varied between 0.1-0.3 m.

Table 4 The DistributionDistribution ofof BaitedBaited LonglinesLonglines Used Used onon KainjiKainji Lake, Lake, 1993-- 1993- 1996. YEAR No. & HOOK SIZE % 6 7 8 9 10 ii11 12 13 14 15 1993 No. 84 0 00 0 0 00 0 00 0 ok 100 0 0 0 0 0 0 0 0 1994 No 113 3 00 0 0 00 0 00 0 0 % 97.4 2.6 0 0 0 00 0 00 0 0

1995 No. 11 0 0 0 0 1 41 27 32 0 % 9.7 0 0 0 0 0.9 37.2 23.9 28.3 0

1996 No 0 0 3 0 2 1 11 10 31 0 0 0 5.2 0 3.4 1.7 19.0 17.2 53.4 0

Table 55 TheThe Distribution Distribution of of UnbaitedUnbaited (foul (foul hooking)hooking) LonglinesLonglines in use onon KainjiKainji Lake, 1993-1996. YEAR No.& HOOK SIZE % 6 7 8 9 10 11 12 13 14 15 I 1993 No. 4 3 0 0 3 8 16 7 3 4 °A 8.3 6.2 0 0 6.2 16.7 33.3 14.6 6.2 8.3 1994 No. 0 0 0 0 0 0 00 0 0 0 % °A 00 0 00 0 0 0 0 0 0 0

1995 No. 0 0 00 0 0 O 0 0 0O 0 % 0 0 0 0 0 0 0 0 00 0

1996 No. 0 1 0 0 0 0 15 5 10 0 % 0 3.1 0 0 0 0 50.0 15.6 31.2 0

Fishing Gear Survey. Kainji Lake,Lake. Northern Nigeria, 1996. Page 14 3.2.6.Fishing Traps The fish trap is a passive geargear set set on on the the bottom, bottom, fish fish . areare attracted by bait and enterenter throughthrough anan opening,opening whichwhich has has a a seriesseries ofalines lines making making escape escape difficult. difficult. Since Since the the fish fish staystay alive alive forfor longlong periods traps areare usuallyusually checkedchecked lessless frequently frequently thanthan otherother fishingfishing methods. ThereThere werewere twotwo types ofof fishing trapstraps inin operationoperation aroundaround thethe lake,lake, oneone wasvas covered covered with with thinthinCanes and one with nettingnetting material.

A totaltotal ofof 2525 fishingfishing traps traps werewere sampledsampled during thethe 19961996 gear survey. TheThe fishingfishing trap height ranged fromfrom 0.47-1.80m with aa meanmean of 0.77m0.77m (Std.=(Std.= 0.29).0.29). TheThe widthwidth at at the the base base variedvaried between 0.36-1.50m0.36-1.50m with aa mean of 0.53m (Std.= 0.24). TrapTrap efficiencyefficiency can can be be increasedincreased by usintzusing widerxvider traps, traps, especially especially if if the the traps traps are are usedused also for fish fencingfencing wherewhere they become fullfull with fish.fish.

Fishing trapstraps are used toto formform an impenetrable wall toto blockblock thethe channelchannel exitsexits during.fishdurinkfish fencing. Fish fencing occurs during the drawdraw down period (March to June) andand isis mostmost prominent in the flood plainplain areasareas of the lake. The practise isis highly destructivedestructive catchingcatching juveniles of TilapiaTilapia andand Citharimts.Citharinits. StoppingStopping thethe incidenceincidence offishoffish fencingfencing shouldshould bebe anan urgent activity activity of of the the ATGKLEPP NGKLFPP

The mesh sizessizes ofof thethe fishingfishing traps variedvaried from 0.25 -1.0 inches with aa meanmean of 0.860.86 inches (Sid(Std.= = 0.20). The mesh sizesize distributiondistribution of the fishing trapstraps for thethe 4 years ofof the fishingfishing gear surveys is shown in FigureFigure 7,7, apparentapparent was the increased useuse ofof trapstraps \vithwith a mesh size 1-1.491-1.49 inches recorded inin 1996. The most commonly usedused fishingfishing traps traps were were the the onesones withwith mesh mesh sizessizes between 0.5-1.490.5-1.49 inches.inches. The The twine twine used used xvas was mostly mostly ofof 99 ply.ply. AlmostAlmost all traps in use onon thethe lake have aa meshmesh sizesize below below 22 inches;inches; thethe minimum minimum allowableallowable sizesize according to the State Edicts (Table 6).6)

Figure 7.The Distribution of Mesh Sizes (inch) of Fishing Traps Recorded during 1993-1996 Fishing Gear Surveys, Kainji Lake. Illegal mesh Legal mesh 80

70 o 60 .0 III 19941994 50

40 cr)cr/ 30 cu 20 a)" 20 0_ 10

0 7 02,5,0 '019"019 6,099'099 7.0'71,971,9 5,77 999,9 19 Mesh size (inches)

Fishing GearGear Survey. KninjiKainji Lake. Northern Nigeria. 1996. Page 1515 Table 6.The Percentage of Illegalillegal Fishing Traps on Kainji Lake, Fishing Gear Survey 1993-1996.

)car Ille111 e al al trafro (%)(9ó) 1993 100 1994 100 1995 95 1996 100

3.3.Target SpeciesSpecies For each gear measurement mademade duringduring the surveysurvey the fisherman wasvas askedasked which which speciesspecies hehe wished to target.target, The results of the combined data frontfrom the 1993- 19961996 surveyssurveys are given in table 77 whichwhich shows thethe totalstotals forfor allall geargear types.types. Table Table 8 8 lists lists the the six six most most important important tat-get target species forfor each legallegal andand illegalillegal gear type.

Target species listinglisting by the fishermenfishermen areare importantimportant forfor management since since they they will will not necessarily be thethe samesame as as the the major major species species caught. caught. For FOr example example Tilapia, Tilapia, a a fairly fairly lowlow value species onon thethe lake.lake, isis thethe thirdthird most important commercialcommercial species species caughtcaught butbut onlyonly appeared appeared in fifth position position on on the the choicechoice ofof fishfish species species targeted byby thethe fishermen.fishermen. ItIt wouldwould bebe misleadingmisleading perhaps toto managemanage on on the the basis basis of of Tilapia Tilapia ifif itit is not really aa targeted species duedue to to it's it's lowlow value.

CiihariiiitsCidiarinits was vas the major fish speciesspecies fishermen wished to target with 66 ofof thethe 1010 geargear types having it asas first andand allall geargear typestypes having Citharimts0/ha/lints either either inin firstfirst or second place.place. ItIt isis taruetecltargeted especiallyespecially byby thethe largerlaruer castcast net.net. drift netnet andand gillgill net net fisheries. fisheries. There There seems seems highhigh fishinE.,,_fishing pressure pressure on onthis this species species which which appeared appeared second second place place in in the the commercialcommercial speciesspecies caught.

SpiodwitisSinodontis membranaceoltsmembranaceoits wasvas another species whichwhich waswas targetedtargeted byby allall gear gear typestypes especially the smaller gill andand drift nets, nets, thethe speciesspecies isis howeverhowever onlyonly in sixth positionposition inin thethe commercial speciesspecies caught. Labe° is the opposite, it isis thethe forthforth mostmost importantimportant species species caughtcaught on the lakelake butbut appearedappeared fairly fairly IONV low on on the the fishermen's fishermen schoice choice list list and and was was only only a a target target speciesspecies for thethe larger drifldrift andand gill nets.nets.

Bagru.s,Rogrus, anan important commercialcommercial species,species, WaSwas targeted targeted byby almostalmost allall gears gears onon the lake especially the small meshedmeshed cast netsnets andand toto aa lesserlesser extent extent by by the the small small meshedmeshed gill gill andand driftdrill netsnets.

Ale.s.tesAle.sles featurefeature surprisinglysurprisingly high high in in the the targeted targeted species species being important forfor thethe largerlarger !nestledmeshed gill nets,nets, theythey are only the twelfth mostmost itnportantimportant commercial commercial species species caughtcaught on the lake.

The high va1uevalue LatesLates appearsappears surprisingly surprisingly low onon thethe fishermen'sfishermen's target target species species andand wasvas onlyonly targeted by thethe smallsmall meshedmeshed castcast nets.nets.

Clarias was only targetedtarueted byby the lonalinelongline fishery,fishery.

Fishing Gear Sur\Survey. eN. Kainji Lake,Lake. Northern Nigeria, 1996. Page 16 The detrimental nature of oneone urdíinch gill nets, which catch mainly:juveniles,mainly juveniles, isis apparentapparent from the target species list which displays all the major commercial species in the top six.

It is interesting toto itnote thatthat thethe majormajor targetedtargeted speciesspecies are similar in the illegal and legal meshed nets. The nets are therefore targeting the same species only at smaller sizes. This will assist in enlightenment campaigns suggesting that the same species can be left to grow before being caught at larger size by larger meshed gears.

Table 7.Target Species and Species Caught Listed in Order of Importance (summed for all gear types).

Species Target species Ranking in commercial Sum of percent importance

Citharinus 183 2

S. merobranaceousmernbranaceous 92 4

Bagrus 63 7

Atestes 60 12

Tilapia 59 3

Other synodontis 45 8

Lates 28 10

Clupeids 26 1

Labeo 18 66

Clarias 18 17

Auchenoglanis 15 13

Hydrocynus 13 15

Other catfish 6 17

Heterobranchus 6 18

Chysichthys 6 5

Fishing Gear Survey. Kainji Lake. Northern Nigeria. 1996. Page 17 Table 8. The Target Species Listed in Order with Percentage Occurrence for Legal and Illegal Gear Types Gear type Mesh size 1 inch S. rnembranac. 1 18 Citharinus% Target species isted in or er (with 2 16 A estes 3 % 1 8 %figure of occurrence Bagrus 4 7 % 7 Titania 6 % Oth.synodontOth.synodon is s 4 6 4 Gill net >=3 inch 3incly3inch' CitharinusCitharinus 2116 AlestesAiestes 11 S. rnembranac.membranac. 1011 LabeoBagrusLebec 64 OtherHydrocynus synodontis 658 HydrocynusOth.synodontis 65 Drift net ,<.2.5>=2.5 inchinch- inch S. rnembranac. Citharinus21nctv2::iriCti. ... S. rnembranac. 2415 CithartnusS. membranac. 1014 OtherBagrus synoctontissynodontis 7 9 AlestesLabeo 711 Titapta Labe°Other synodontis 5 AuchenaglanisTilapiaTilaptaLates 45 seineBeachCast Net >=2 inch ClupeidsCitharinusBagrus 262817 AtestesCitharinusTitaniaTilapia 814 AlestesLates Citharinus 81012 S.Other membranac. synodontis 6 Bagrus 711 Titabia LatesS. membranaceous 5 5 Oth.synodontisLates 5 longlineBaitFoul Citharinus 1211 BagrusCiarias 10 ClariasTitania 89 HeterobranchusBagrus 69 TitabiaTitaniaS. membranac. 65 OtherAlestes catfish Traeslongiinelongtine Shaded areas indicate illegal fishimz gears according to the State Fisheries Edicts Citharinus 19 Auchenogianis 11 Titania 8 S.S membranac. embranac. 7 0 her synodontis 7 hysich hys Fishing Gear Survey, Kainji Lake,Lake, NorthernNorthern Nigeria,Nigeria, 1996. 1996. page 18 References

Apeloko F. and T A. du Feu, (1996).(1996). FrErnieFrame survey. survey. Kairtii Kainji Lake,Lake, Nigeria,Nigeria, Februaiy,Februaty, 1996.1996. NGKLFPP Tech. Rep. Ser. 36p. du Feu.Feu, l.A.TA. (1993). Fishing gear survey of Kainji Lake, NGKLFPPNGKLEPP Tech.Tech. Rep.Rep. Ser.Ser. du Feu.Feu, TA,1.A, (1996).(1996). AA guideguide toto thethe designdesign andand useuse ofof thethe computerisedcomputerised datadata systemsystem forfor KainjiKainji Lake. NGKLFP1'"NGKLFPP Tech.Tech. Rep.Rep. Ser. du Feu. T.AT A and A.A Kasali.Kasali, (1996).(1996). FishingFishing geargear survey.survey, Kainji Lake, Nigeria, September, 1995. NGKLFPP Tech. Rep. Ser. du Feu, T.A.TA, (1997)(1997). Fisheries Fisheries statistics statistics ofof KainjiKainji Lake.Lake. NorthernNorthern Nigeria, NGKLFPP

Tech. Rep. Ser. (in press). 103p.1 03 p.

Niger State Fisheries Edict.Edict, 1997. Edict No. 3 of 1997. Pub. by Ministry ofJustice, Minna, NigeriaNigeria. JuneJune 1997

Kebbi State Fisheries Edict, 1997. Edict No. 3 of 1997. Pub. by MinisttyMinistry ofJustice, Birnin Kebbi, Nigeria.Nigeria June 1997

Visa.Visa, Z, F. Apeloko and A. Kasali, (1994). Fishing gear survey of Kainji Lake, Nigeria, West Africa.Africa, N1arch, 1994,1994. NGKLFPPNGKLFPF Tech. Rep. Ser. 17p.

Fishing Gear Surve. Kainji Lake. Northern Nigeria, 1996. Page 19 Glossary

HansaHausa names Fishing canoes Jirgi Gill net TamTaro hako DrilDrill netnet Taro-Tam duroduru Beach seine Dalla Cast net Birigi Longline Kugiya Fishing traptal) Gota or N'durutu

NGKLITPPNGKLUTP, The Nigerian-German (G.112)(GTZ) Kainji Kainji Lake Lake FisheriesFisheries PromotionPromotion Project

All mesh sizes are quoted in inches and refer to stretched mesh size. AHAll meansmeans ofof geargear lengthslengths havehave beenbeen expressedexpressed asas 5%5% trimmedtrimmed meansmeans soso asas notnot toto decreasedecrease the accuracy caused by extremely short or long gears. Gill net lengths are expressed by the fishermen as number of bundles. The length of a bundle varies but is taken to be 100 yards (91 meters) of unmounted netting material. LonglinesLotiLdities on on Kainji Kainji Lake Lake all all use use Kirby Kirby Sea Sea hooks. hooks. The The sizesize ofof hookshooks isis thereforetherefore expressedexpressed for this hook. One box (100 hooks) forms one line. The targeted fish species quoted are the same taxonomic groupings used in the NGKLFPP CAS survey.

Fishing Gear Sur\Survey. ey. Kainji Lake. Northern Nigeria.Nigeria, 1996. Page 20