(,J

The removal of non target organisms has beena cause of concern for fisheries managmentfor many years, the extensive capture ofjuvine and yong fish commercially importantspecies has frequently been regarded as athreat to recruitment of stocks. Manyfisheries harvest individuals of the targetspecies before they reach size in terms offuture yield. The use of lager mesh in thecollection (cod end) was among the firsttechnical measures imposed by fisheriesmangers to prevent the capture ol'juvinile. Amore recent concern, begining in the 19705,was the unintended capture and killing ormore charismatic animals, like marinemammals, seabirds and turtles. by

fisheries. The usc of fishing gear in suchenviroment sometimes creates unintendedimpacts sufch as remoal of oranisms that forvarious reasons, should not be taken (e.gjuvinile threated species)

A 2004 FAO report provided an estimatediscard in commercial fisheries of27 milionsoftons per year compared to 50 milion tons ofdirect human consumption. A more recentFAO document estimated that dscard wre intheorder of above 20 millin tons in 2007. Themajority of the world's fisheries are nultispecies m nature and consequently it isdifficult to optiisc mangmcnt measures for allthe species caught. Commercial fishinginvolve a wide range of gem and techniquesused in environment that ar also occupied byorganisms that are not targeted by the

INTRODUCTIONIt is now clear that the world's fisheriesrecourses are been subjected to explitaion atonabove their capacity to produce maximumsustainable yields. At the same time as thesetrends are being felt, thee is a very largewastage of fisheries resources fromdiscardingunwanted cachers at sea.

Keywords: By catcb gera mofifiation, fish discords, turtle excluder

AbstractTheehave been considerable efforts in recent tears to modify fishing gears and practices to targetparticular sizes and species offish (fin and shell) and other marine organisations more efficiently.These efforts are corning on the heels of the negative impact they lead to have on the populationoforganisms in the aquatic ecosytem.By catch consideration and gear modification play on important role in regulation of severalconsideration and gera mofificfation play an important role in regulation of several majorfisheries and new by catch reduction devices and other innovative gear modification arecontinously being proposed and tested to mitigate against these problems among which are theturtleexcluder device (TEDS) in the shrimp trawls to reduce mortality of endangered sea turtle,sortinggrids and scaring device in long fisheriesRecommendation are made on effective monitoring offishing gears to ensure that devices armedatreducing by-catch are included and fishermen usc only the appropariate gears to limit by-catchanddiscards.

ByOgunfowora, 0* and Uka, U.N.

National Institute fOT Freshwater Fisheries Reserach, PMB 6006New Bussa, Niger State

*Correspondence author's email adrcss:

REDUCING THE INCIDENCE OF BY-CATCH THROUGH FlSHI:\G GERAMODIFICATION

62

waters shallower than 18m arc prohibited andcod end of s a shrimp trawl shold have morethan 44mm mesh size. yet observation offishlanding and activieies at the sea suggest thatthese statutory provision of the fishingregulations are not being strictly compliedwith. The by catch problem has beenimmensely compounded by the concentrationof the shrimp trawl industry presentlyonbrown shrimps at grounds, which appearsto be nursery ground of young and juvenilefishes, apart from fin fishes, non-fish speciesare also caught as by catch: Crabs -protunusvalidus (smooth swim crab at aroung 30mdepth)And \Lobster - Pamulirus reginus (5-4001depth); brown cuttrle fish Sepia officianlis(down to 200m) and octopus; Turtle -EretmochJys imbriate (hawksbill). Mollusese.g snails and bivalves. Exploratory trawlhaus betwen November 1980 and March 1981of commercial boats in the Niger delta area byAjayi and Adetayo (19&2) and catch and effortdata gatherd by FDF since 1970 fromindustrial' fleet analysis reveals the majorspecies and compsition of fidh by catchdiscarded as shown inTable 1.

INCIDENCEOFBYCATHI~ NIGERIAPast and present studies in Nigeria, watershave shown the proliferation of fish bycatches, their species/size cornposirionl,andmode ofutilization.In Nigeria, efforts have heen made to ensureresponsbile inshore fishing practices throughprornulation of sea fisheries law and (Act ofparlirnent No 71 of 1992). But effectivemonitoring and enforcement of theseregulations is lacking. The occurrence ofsmall but mature fish species in pcnaidtrawling ground makes a selection withinfishing gear rather dillicult. even though,trawling shrimps which attracts the highestincidental catch within the first five nauticalmiles of the Nigerian continetal shelf and in

commercial fisheries in particu.ar, theincidental capture and mortality ofendangered or threaten species that arc longlived and have low reproducive reates hasaroused growing conflict. The unseenmortality due to fishing by lost gear hasrecently also attracted much attention whichhas stimulated extensive research anddevelopment efforts by many countries tosolve the many problems. As the upper limitsproduction from capture fisheries especiallymarine have become more obvious, fisheriesmanagers have introduced a variety of newcontrols, including regulation to limit accessto fishing grounds, to limit fishing efforts andto set total allowable catches and by catchlimits. Subquent technological modificationsin fishing gems and their operation haveproved successful in many fisheries that arefacing bycatch problems. This paper reviewsthe successful development and applicationsof selective fishing techniques that have beenused to achieve by catch reduction and as wellassesses the incidence of by catch in Nigeriaand the effects f discarding them at the sea.The paper highlights ways of ensureingeffective monitoring of the modified fishgears to achieve sustainability of theresources.

63

PriSIiuat cridncSc iuni d",'

l laemul iadeEnhiuidac

Cvnoalossi dac[)I Cohauida C

Snecies No Si:H RallPe (em)Hcmicuranz bicolor 7 ~-14Selene dorsalis 17(\'110!!0::;::;usseneca lensis l<1 10.23Drc oann A t'riL::ll1<l 92 LUIChuci oduu crus .m!) J 6.12P()l11ada.,y~ juhel ini 2(, {).I ,I(iii(eode s dccad act \·111" ~7 10- 1(,Polvdact \ 11I~cllhldnii II i~ 7() 10.1:'1111~b;\I'rii."HLI ('I .'.2 ~1':--:11\.1p[;111.1:-,1.1~:lllb III 11- I ~I'. <cuc zulcu-r-, 1;\., :-IX1'.I~r .' Ix.~ i ...-1(1j\'g,dll ~1)..::llpl i J I-.-l

I 1\':.!;ll.IS ,"'1' ~() (J. I .\I-r I')

Carnngi tint'Familv

Otobotckcrc t 19c)9) rcccnilv reponed cv idcncc otsalc otdiscards CSI1JlWh.'d abourLmctric tonsdaily. The species and size range» or ~lllIpk:dfish cut-catch sold intu Riverine local marketsarc shown illTable 2.Table 2 Si:L~ rW1g~'"or [ish sunplcs or discards sol d al sci! by shrimp trawlers in Nigcr-Delruwaters

Source: Adcbavo and Aiavi, 19R2

Dprepau« AfricanaTricltiurus I l'PIIlt'II:il.arim us peliGetres 11It'/C/I/()f)tel'IIS

Cvuoglos us cauarient S

C. scncgalinsi SC. moudodiArtus. Haudeloti.:1. la ;scII/(/1 IfS/'>('1/ I (f II<'I/II,I,~ q11; I7tJ narisGalcuodvv decadartylusPoll 'do( ti Ills auadii IiI is

I PomudasvsjubcliniI P'suillu»Raja 11/ iracl ell I,"Dasyastic margaritaChuractcrias Tall/TIsBnKh.n/('11 tents aunuus

. 111;,/10AlricatraI'oilier sctpiuis

_.Pseudoto! if/1!IS typosl'. senegal ells isP. c!£'11 !!II tus

major grOl'l)S nd components species of iucideutal fish catchMeilll Composition of Component speciesCommercial landlns

Mixed

Salce haia ns

Pomadasydarc

Polyncrni dac

Aritida tc

.-Cynoglossi cine

-Sciaenidae

Table One: theFish Croup

64

Akinde ( 1991') reported the ratio of shrimp toby catch based on the catch data ofcommercial vessel between 1992 and 1997

trash, juvinile and nun-commercial speciesmay be caught annually, by woo activelyoperating vessel (Olaniyi, 1999).

Nothwithstanding the lower commercialspecie is a serious concern lor biologicaldiversity and sustainability of the shrimptrawling fisheries. The estimate based on theassumption of three and four trips per annumfor while prawn an dbrown shrimpsrespectively is that about 3000mtfyear or

Table four: Catch analysis of shrimper (Kg) between 1999~-1994;\lonth Prawns Shrimps Totals Fish hy Shrimp to

catch fish ratio:-.!ov!Dcc 92 3270 370 J646 5840 1:2Ian 93 )900 544 444 lO200 L:2Ft:b!Nlar 93 4126 990 5116 7500 1:2May 93 3556 140 37% 7300 1:2June/Jut (X> 195(, 63(, ::~92 IM20 I:()Jul/Aug .(_).l .11()~ (,74 .1~42 (15(,(1 1.'1• .<.

Scp.Oct '93 227-1 2392 4 (l()() 1954{1 1:4Oct/Nov -93 2412 3954 ~Q76 30600 1:5[kc'9) 12 5004 L0720 20520 1:3Jan 94 326 10718 5868 23600 1:2Feb/Mar ·94 -1-1:-1 55-1:: 13626 10080 I.')Apr '94 1048 13178 11262 J-L200 L:1vlayJune ·')4 )52~ 10.21-1 1!l492 22(JIlO 1:2July '1)-1 27)() 4964 950(, J 4<)6(1 1.7Aug':>! S~rl·q..J ..JS() 6750 L232(l .215211 1.7Towl 28-190 11861 1165_,8 17BSO I·)

Take J indicate, the percentage compostion of shrimping operation at vari ng depth on majorfishing ground in Nigeria waters.

The average adult lcr ~b and size at maturity of Ihcsc fishes indicate t hat (I fairly large quantityof them arc removed be fore reaching matu riry and this is bound to h..we ~1Jl adverse consequenceUII recruitment. The results ora recent study of the fish by catch problem at various depths ofsome popular fishing grounds in Nigeria confirm again that Ihere is high percentage of by catchaccompanying penacid shrimping in \"igeria. with catch composition varying frum one fishingground In another depending on the targeted species (Otnbotekere 1(91))

Source: lsehor, 19i)<)

50.! 4.7 () 41.()2:-;.2 () o. I 71 .(),.., - n OA 72.1-'- ..)55 () 0 45~() 1.7 ·L 57.44·' 4.X 1.2 51.l

(,l.X l.X o 34425.7 24 () 50 ..369.0 9.1 3.6 17.3

By Catch

Sengana L,(~')ob() I ()Kwa lbo 10Calabar 10

I-scra V(lS

141010f.)

LagosLagos entracclhcjuLekki

Table three: Percentage composition or shriping operations at 10-14 meters at various fishinggmunds _ _Fishin~ ground Depth Fi:;h('!·o) Shrin p (I~O) Crab i"l\)

{m)10

65

Effects of discarding fish at seaEconomic effect

• Income that has been forgotton as aresult of juvenile and adult targetspecies discards

• Income forgone in other fisheries as aresult of dicarding non-commercialspecies

• The cost of managing discards andmeasuring their quantities

Biological effects• Survial of most discarded specdies is'

low. Discards therefore may be asigni ficant part of fishing moratality,

• Reproductive activities ofsuch fishes

• Technical reasonsThey are usually by-catch of fishingoperations which compose of juveniles andthose of netting damage adult inviduaL Theselectivity of fishing operation variesdepending on the tye of gear being used whcihoften has an effect on the survival rate the fishbeing discard. Using the same fishing gear indifferent areas can induce different discardproblems depending on local biodiversity andspecies abdundance of the fishing area.

of the catch which maximzes value. This iscommonly referred to as high grading anddiscards are made of part of the catch afterstorage space on board. Fish that arc damagedduring operations are often discard because oftheri unmarktable aspects. Catch issometimes returned to the sea even before itreaches the dock. This can occur on somepelagic trawlers if the species composition inthe catch is not deeemed to be sufficient valuebefore pumping process to bring that catchboard is initiated.The economic reasons for dumping fish bycatch are summarized in the following:

• Damaged or mutilated fish• Species with no current market• Achievement of quota• Undersized individuals• Unmarketable species eg dolphins,

sea turtles

..

Economic measuresThere is often a strong economc motivationfor dicarding. Some species have nocommercial value locally or sesonally due topoor conditions whilst other species arecaught in unmarketable sizes. After themajority of hauls and especially during longtrips, the catch is sorted to return only that part

REASON FOR DISCARDING FISH BY­CATCHDiscard fish by-cash arc based on thesereasons: Management measures, Economicsand Technical reasons.Management measuresManagment measures in some fisheries placea legal obligation on fishermen to discard apart of their catch at sea. When the alowablecatch quota is achieved for a species, landingof excess 'catch are probibited and thefisherman theoretically have no otheralternativge but to dump the over quotavolume at sea However, in reality over quotacatches are often landed illegaly and daretermed "black fish". Maximum landings sizeregulations protect juveniles from beinglanded but those that are caught by fishinggear must be discarded to ensure compliance.In some fisheries a specific small mesh size isallowed for a target species for small size butin order to protect other species being caughtthere is a maximum threshold allowed in thelandings for commercial non-target speciesexpressed as a percentage to the retainedcatch. Closed and protected fishing areas arealso used to restrict the catch of somecommercial species which can be caught at allor allowed to be caught in a limitedproportion. Some species are protected byregulations or international conventions suchas CITES List of endangered speies (marinemamma, turtles, etc) and should beimmediately returned to sea when caught.

(Table 4) some naturally small sized fishspecies were observed to continute more than70% of catch at some grounds, also there areindiation from the Gulf of Guinea largemarine escosystem survey carried outbetween February and March (1999) of serveimpact of shrimp trawling fisheries on thejuvinile of cornmccial finfish resources

REFEREl'ICRAjayi. T.O. and Adetayo. J. A (1982) On the

fgish by-catch and discard of theshrimp fishery of Nigeria. Technicalpaper No 5. Nigeria. Institute ofOceanography and Marines ResearchLagos.

lsorbor, C.E. (1999) Proposed FAG project onthe Reduction of the impact of tropicalshrinp trawling fisheries on livingmarine resources.

John willy Valdernarsen and Petri Suuroneri(2005). Modifiying fishing gearachieve ecosystem objectives. FAOoccasional paper no 18 FAO Rome

Orobotekere, AST (1999) Reduction ofimpact of Tropical Shrimp TrawlingFish Fisheries on Living MarineI{esources (ProjectlH\!INT!724!GRG)

on the profitability of the fishing operation.There are currently no universal methods ofmodifying gears to reduce habitantdissturbance. Solution are specific to gears,fisheries and habitat and are stronglyinfluened by regulatory and economicconsidderations, understanding the captureprocess offishing gear in various environmentis the key element in developing modificationand practices that can reduce by-catch andescosystcm impact. In essessence there is aneed for the government to enoree a strongpolicity to combat by-catch and discardsreduction most especially in the wake of eco­labelling in the international market whichadhere to strict fishing standard. Thefollowing are therefore recommended.

• Enforment of fishing regulations (uscof correct mesh size and otherdevices) before going to sea, while atsea and on landing

• Economic reward should be offeredfor the creation of new types of gearand modification that reduce by-catchand minimize impact on habitats

• Enforcement of gear regulatiun Iortargeted fish species.

Conclusion and recommendationI)iscarding of unmarketable, retrictcd speciesand small sized individual tagged by catch is aglobal. economic, environmental, andpolitical problem which can be reducedthrough fishing gear modification.The technologies developed in recent yearsdemonstrate that the impact of fishing gear onnon target species and habitat can hesignificantly reduced without negative effect

TURTLE excJusing device (TED)• It is a dymnamic and rigid device• It is inserted in from of the cod end• [t allows for the escape of turtles out or

the trawl.

Appliation on selective fishing techniquesIn recent years some technologicalmodifications in fishing gears and theiroperation have proved successful in manyfisheries that are facing by catch problems.For example the introduction of "Turtleexclusion device (TED) in shrimp trawl hasdramatically reduced the mortality ofendangered sea turtlesThe spectacular decline of the by-catches anddiscards of'finfish in many fisheries have beenthe result of by-catch reduction device such assorthing grids, square mesh panel, scaringdevice in lognlines and nordrnorc grids whichmain feature are highlighted below.

Social effects• Varies between nations and sections of

socty depending on ethical belief,cultural differences etc

• Itaffects the dynamics of the expolitedstocks in terms of yields recruits

• They can affect other fisheries sincethey by-catch speeies in one fisherymay be the target of others Iihcrics.

may be significantly affected.• The populations of endangered

species are further threatned• Certain ecological riches are created

for scavenging fish.