Lake Kyogaand Lake Kwania
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The ADP/FS frame survey of Lake Kyoga and Lake Kwania Item Type monograph Authors Hartsuijker, L.; Kibwika, D.; Twongo, T. Publisher Agricultural Development Project Download date 24/09/2021 23:23:44 Link to Item http://hdl.handle.net/1834/35401 ., Lake Kyogaand Lake Kwania 1990 Uganda by L. Hartsuijker D. Kibwika 1: Twongo • Agricultural Development Project " Fishery Survey P.O. Box 343 Jinja Jinja, September 1990 KYO 639.2.06(676.1) -----------' 2 CONTENTS PAGE 1. The need for a census '-' .L:•• ~~en.?us mpthods 2.1 General on census Sample-surveys Survey cost .. .~ "_I • F'repar2.tion of the FI'"·a_me.~Survey" ~.L 1 The area to be covered Design and questionnaires 4. Survev sc: hed u l!-? 4· • 1 L.ogi.stics 4.2 Survey staff 4· • :3 Coverage of the area and the fishery 5 Su~__ ~>(ecut.:i.:on Survey Protoc61; visits and interviews I: ~-: '.~' '" 0'::' Landing site summary ~.::; 5 u '32mp 1':2 record 5.4 The assistance of MAIF personnel (Fisheries Dept.) 6 Sur\fe~sults: Landing .sitE':' summar-v 6.1 Boats 6.1.1 Used, unused and unusable boats 6.1.2 Boat Building and Maintenance 6.1. :::;; Operational fishing boats 6.1.4 Comparison with results of the MAIF census 1988 6.1. 5 Carier-boat, DB-engines, DB-mechanics and Fuel supply 6.2 Fishing gear used by operational' boats 7. Survey results; Sample record 7.1 Oll-mership 7.2 Gillnets 7.2.1 Numbers of boats operating gillnets Mesh-siys No. Nets per boat 7.,2.4 D(~cL::'T·,J.tion Df Ih.3.1f··-n2ts" 7.2.5 Total numbers of gillnets; used and n i2eded 7.3 Seines 7.4 Hooks and Traps 8 Prinripal products 9 §moking and smoking unit~ 10 Gear SUPPfl 11 gther activitie~ 12 Miscellaneous 3 1 • THf.L--'i~lJL.f.:.Q.!~ ~~ G.!?~.t!f~JH?. The ADP Fisheries Survey of Lake Kyoga is charged with a stock-assessment programme. The term stock-assessment is generally used to exp~ess the need of fisheries managers for knowledge on fish stocks which are allegedly over-exploited already. stock-Assessment can be very comprehensive, costly and time-consuming. Essentially however, investigations into exploited stocks and the fishery should provide viable answe~s to the questions of management at the shortest possible notice. Surveys should in any case p~ovide indications concerning the rate of exploitation. That requires the execution of a catch assessment survey (CAS). CAS is done by sampling from the fishermens catches and the extrapolation of results from that sampling to the entire fishery. Therefore, a CAS programme.requires reliable data on the volume and distribution of fishing effort. There is thus a need for a census prior to the desi~n and execution of any CAS programme. 2. CENSUS METHODS ----_.._..-.......---- 2.1: G£n~r~L-9..!L.£ens.J.ls_..tech11iguf:.'s Th~ census of a fishing industry is generally called a FRAME SURVEY. This is a rather comprehensive term, because there are many aspects of a fishery which one might wish to know. This is amply illustrated by the report on the partial census executed by the ADP/FS on the southern landings of L. Kyoga during December 1988. Frame surveys can for that reason be very elaborate and consequently costly. In principle, frame surveys can very well be executed as sample surveys (like CAS), but such sample surveys still require information about the size of the total population and its distribution. For that reason, resea~ch projects in large bodies of water often propose the execution of an aerial census prior to a sample survey of the fishing population. This is indeed a quick, though very costly method to identify the location of landing sites and to count the total number of boats. 2.2: §_~..!ltQ.t~_:-jL'=.t..I:..~'..L~ The extrapolation of sample data is a statisticians occupational hazard. But every sampl~ has its variance and every extrapolation has its level of probability. In simple cases, such as a large number of landing sites, but only one type of boat with one type of gea~, the results of limited sampling can satisfy the demands of fishery management ~""' ,-"--•..,,~"'- ............. ~"'_ ..- _...... -.-.~ ... -~,~, ... -"'~ ,-',' ''>-'-(.. <~ - ··..·.._·'....,·'1-·.,; ..p":; ..' . {.~" .. quite easily. But the situations gets complicated where there are more boat types, and several gear types. The problem gets even more complicated if the ecological characteristics of the water body lead to divergent patterns of distribution of the major fish popUlations, because this also leads to divergent patterns in the distribution of ~ishing methods with different boat - and/or geartypes. ..,. nd Since in a new situation (first census) the sampling variance is not well known beforehand, the size of the sample should also be to large, like one out of every third landing, or the sampling should be stratified over large, medium sized and small landings. The latter usually implies the sampling of all large landings, about half of the medium-sized landings and one fifth of the smallest sites, or something similar. Practically this means travelling over the entire area and sampling some 2/3 of all landing sites anyway. This is reason enough to do a complete census on any first occasion, but a second census could be limited on the basis of the degrees of variance found previously. i.? .. 3: The aerial survey had been budgeted for about U.Shs. 5,&25,000 in the ADP One-Year Action Plan March 1990-March 1991. Considering the aims of the survey, the statistical uncertainti~s and the cost of an aerial survey, it became obvious that th~ execution of a complete lake-wide census could be much less expensive and much s more effective than the execution of a sample survey after an by i:\ E)'(' i iii 1 Cf:)nsus. Actually, the entire operation with 10 members of staff 20 days i nthe f i. (.:~ 1d c 0 ~;.-l~ abo1I t U_S h s • 1. , E, 0 0 , 000 ( Jun t;> 1 9'30 vallie (:~ ,,' • UB$'tOOO) ., • ~o :3. :I. : The Lake Kyoga complex is much more extensive than the surface of the two major lakes Kyoga and Kwania. In fact the entire complex should be the project's survey area, but all swampy areas and series of minor lakes east of Lale on L. Kojweri and Iyingo on L .. Kyoga are virtually inaccessible by canoe, difficult to reach by road and partially still in insecure areas.. Moreover the expense to cover these areas remains prohibitive. Howev~r~ previous data on fishing populations and catches include much of t:hf:~ ~::.\I,li,\lllpy litkE' i"rE:'ctS :i....·, ~)oT·ot:i d:i.!;;t.:r:i.ct.: ,:tnd t:h:i.~; ~:.holllcl be kept in mind in all comparisons with historic data. ~.:.; 3.2~ P... !~ ..~:LL~~.lJ. .. _f.~.tl ..Q.. _JJ~J..f:.§.IIP.!i!jB.I.B.E~~. Th (." .Lr.:.~~.n}.~L_~i..':.U::Y..~Y. __ .~i.s.l')..9.!.~.~:.\.1~. 7 i • e • '1; h (~ bud!l ('? t 'f' (~q u i 'I' e d of 0 'f' i 'I; f:; execution, had to be pTepaTed on the basis of an estimate of the time needed to visit all landings and to inteTview a laTge numbe~ of boat opeTatoTs on those landings. III The table below pTovides infoTmation fTom pTevious sUTveys and 1990 sUTvey Tesults fOT compaTison alTeady~ CE"'SUS U~KE KYOGA LAKE I<.W(.:)I-JIA ADP 1987 78 L. 3459 used 556 unused included with L. Kyoga MAIF 1988 100 L. 3074 boats NO DATA 22 L. 421 boats NO DATA ADP 1990 102 L. 3189 used 563 unused 48 L. 694 used 76 unused Th.E:~ 8.~f~,~Q.!J.2..!:.!,~i.....J,~~ ..8? on southeTn L. Kyoga coveTed 28 landings with 1S01 used boats dUTing 17 days an~ extTapolated the Tesults to a total of 78 landings on the entiTe L. Kyoga complex. The MAIF census of 1988 mentions 122 land!ng sites without fUTtheT specification. But that infoTmation means that a full census could take 122: 28 x 17 ~ 74 days with one team of enumeTatoTs. HoweveT the sUTvey effoTt and expense had to be bTought back to about 20 ~ays, with 2 teams of enumeTatoTs still a laTge opeTation anyhow. -It means that enumeTating teams would have to coveT 120:20:2 ~ ~bout 3 landings peT team peT day. Large landings could take mOTe than half a day's wOTk. It was theTefoTe necessaTy to reduce the questionnaiTe to vital information only. The expeTience gained dUTing the ADP 1987 sUTvey was helpful. ~_an.Qj...D..!L si..:!:;e i_Dfo.l:..matJoD, could best be obtained f'f'om the Gabl.mgc\ (fishing chief) in Tesidence 0'1' any otheT peTson in chaTge. It was not realistic to expect all Tesident boat opeTatoTs to tUTn up faT an inteTview. TheTefoTe it was decided to use 2 fOTms: a landing, site summaTy; a sample TecoTd fOTm. MOTeoveT those sUTvey fOTms had to be designed in such a way that some pTioT analysis could be done in the field at the end of any day, including the check on eTTOTS and omissions. 2. THE LANDING SITE SUMMARY was extTacted fTom the fOTm used dUTing the pTsvious sUTvey, including only basic questions on fishing equipment and economic aspects. It includes two new questions: the names of neiahbouring sites~ fOT cOTTect map TefeTence and in oTdsr to avoid skipping lan~ing sites; -......--- W"'-_~_'._ _... .........- ... _·",._._>"-........ _••~~_1·· . ,.-........... ~" -'.'_. _._""'--.- ......... -,-,,-.~ ._,,.,...~_-ce,., '~ , '7~__ ''.