Aquatic monitoring non-target entomofauna of rivers larvicided by the onchocerciasis control programme in Sierra Leone

ONCHOCERCIASIS CONTROL PROGRAMME IN WEST AFRICA PROGRAMME DE LUTTE CONTRE L'ONCHOCERCOSE EN AFRIQUE DE L'OUEST ECOLOGICAL GROUP Nineteenth session Odienn6. 4 - 6 February. 1998 OCP/VCU/HYBIO/98.9 ORIGINAL: English AQUATIC MONITORING NON-TARGET ENTOMOFAUNA OF RIVERS LARVICIDED BY THE ONCHOCERCIASIS COTNROLPROGRAMME IN SIERRA LEONE Daniel Tholley Larviciding of selected rivers in Northem Sierra Leone had been conducted by the Onchocerciasis Control Programme since April 1989. Among the rivers larvicided, three had been selected and monitored for aquatic monitoring of non-target entomofauna since March 1989. These stations and rivers monitored were Outamba Park on the Kaba, Makpankaw on the RokeUSeli and Musaia on the Mongo rivers. Larviciding of these rivers monitored had been intemrpted due to changes in the security situation: on the Rokel since March1994, on the Kaba and the Mongo rivers since March 1995. Larviciding had only resumed on the Kaba and the Mongo river in January 1997 with the Rokel still suspended for larviciding. Relative to the disruption of the larviciding progfttrnme as designed by the Oncho Contol Programme, this year's monitoring report was mainly to assess the effect of larviciding, its suspension and human activities on the non-target aquatic entomofauna. The following were the observations made for various sample types collected for all the stations monitored. (a) Saxicolous fauna (1) Larviciding or its suspension had not been clearly identified to have an effect on the changes in the mean number of individuals per taxa. (2) The mean number of individuals per taxa during periods of suspension of larviciding dropped to levels below the mean number of individuals per taxa during periods of larviciding. (3) Species richness on all the stations remained relatively unchanged but species variation had been affected. There had been a recorded rarification of species like: Neoperla, Aethaloptera and Oligoneuriidae during the suspension period. 2(4) There was the resumption of the dominance of some of the dominant groups in these stations before commencement of larviciding. These were the Tricorythidae at Outamba Park, Chironomidae at Makpankaw and Musaia at this reporting time. (b) Drifting Fauna (1) Day time drift At Outamba Park, the day time drift samples showed that during periods of larviciding Dipteran groups were dominant taxa but on the suspension of larviciding Ephemeropteran groups were the dominant drifting taxa. At Makpankaw, Dipteran groups remained the dominant drifting taxa irrespective of condition at the sampling site but species variation had narrowed during suspension period with Dipteran and Ephemeropteran groups showing similar drift indices specifically in March 1997. At Musaia, there was no clear picture on the impact of larvicide on the difference in abundance between Dipteran and Ephemeropteran groups. There had been an interchange in dominance between these two groups irrespective of larviciding or its suspension. (2) Night time drifi There was a general drop in species richness in all the stations with the rarification of major Ephemeropteran, Tricopteran, Odonatan and Coleopteran taxa in all stations even when larviciding was suspended. Difflerences in abundance between the major taxonomic gloups showed that Ephemeropteran groups are predominant at Outamba Park, Makpankaw and Musaia at this reporting time when larviciding was suspended. Conclusion Larviciding or its suspension had little impact on the changes in faunistic variations, total fauna and differences in abundance between the major taxonomic groups. Relatively, data from water analysis does not show any change in water quality but other environmental and entomofauna information had shown that human activities related to the use of Itcthyotoxins in fish killing and proximity of human and animal populations to the monitoring sites may play a role in the lack of improvement in faunistic variation, species richness' total fauna and drift indices of the non-target entomofauna in the absence of larviciding. LHaslrar ASSESSMENT An evaluarion of habitat qualiry is critical [o any assessment of ecoloeicalintegriw and should be p.rfo"n.a at each site at tire time of the biological sampling' ln the truest sense' ''habitat" incorporares all aspecs of physical and chemi;al constiruen6 along with the biotic interactions' In ,r,.r" pro,o"ois. tnl deflurition of "habitat'' is narrorved to the qualiry of the instream andriparian habitat thar influences rhe structure and function of the aquatic communiry in a stream' The fr.r.n.. of a 6eeraded habirat can somerimes obscure investigations on the effects of toxiciry and/or pollution. Habitat evaluations are firsr made on instream habiut- followed by charurelmorphology' bank strucrural fearures. and riparian vesetation. Generally. a single. comprehensive assessment ls made rhat incorporares fearures ofihe entire sampting reach as rvell as selected t'earures of the catchment. Additional assessments may be made on neiehborine reaches to provide a broader evaluation of habirat qualiry tbr the stream ecos!'stem. The acrual habitat assessment process involves rating the lO parameters as optimal. sutoptimat. marginal- or Poor based on the criteria included on the Habitat Assessment Field Data Shees PRocrounr FoR PERFoRMING Hnsmer AssEssMENt l.Selectthereachtobeassessed.Thehabitatasscssmentisperformedonthesamel00mreach(or other reach d.rigrr",i;;;;;hich the biological sampling is couducted' Some parameters require * oUr.*u,O"n liu iroua., section of"the catchmtni ttt*;utt the sampling reach' 2. complete the station identifrcation section of each field data sheet and habiut assessment form' 3. Generally, it is best to perform the. biological sampting first, so the investigators obtain- a close look at the habitat features. lf the physical and water q"'Iit characterizatioo and habitat assessment are done bcfore the biological sampling. ."" **t ut taken to avoid disnrrbing the sampling habitat' After scrutiniang,r,"'i**am'habi-iut during sampling, rcfinement of the visual-based habiut assessment maY be necessary' complete the Hebitrt Asscssmcnt Ficld Date shcet, in tears of two or more biologists' if porribt., to come to 3 consensus on determination of quality' Q ualrrY AsstrRANcE PRocEDURES l. Each biologist is to be trained in the visual-based habitat assessment technique for the applicable region or state. 2. The judgmcnt criteria for each habiut pafameter are calibrated for the sueam classes under study to be apPlicable to an assessment' j. periodic checks of assessmcnt results are completed using pictures of the sampling reach and discussions among the biologists in the agency a .l ! HABITAT ASSESSMENT FIELD DATA SIMET-LOW GRADIENT STREAMS (FRoNT) STREAM NAME LOCATION STATION #_ RIVERM ILE LAT LONG RIVER BASIN AGENCY th^/ESTICATORS FORM COMPLETED BY AM PM DATE TIME - REASON FOR SURVEY Condition Cr(cgoryHrbitetPerzmeter Optimel Suboptimrl Mrrginal Poor Crcatcr than 50Zo of substratc favoreble for cpifaunal colonization and fish covcr; mix of snags, submcrgcd logs, undcrcut banks. cobblc or othcr srablc habitat and at shge to allow full colonization Dotcntial(i.c., logs./snags that arc not ncw fall and not 30-50% mix of srablc habitat; well-suitcd for full colonization potential; adcquate habitat for rrraintcnancc of populations; prcsencc of additional subsu-ate rn the form of ncwfall, but not yet prepared for colonization (mav rate ar high cnd ofsialei. l0-30% mix of sublc habitari habiur availability lcss than dcsirablc; substratc frcqucntly disturbcd or removcd. Lcss than l0% stablc habrtar; lack of habitat is obvious: substralc unstable or lackrng. I. Epifeunal Substrate/ Avrileblc Covcr SCORE 20 19 18 ,17 t6 t5 t4 13 t2 ll l0 9 .8 7 6 5 4 3'2 I 0 Mixturc of substnte matcrials, with gravcl and ltrm sand prevalent; root rnats and submcrgcd vegetatton comrnon. Mixture of sofr sand, mud, or clay; mud may be dominant: somc ro6t All mud or clav or sand bottom: little oi no root mat; no submerged vcgetatron. Hard-pan clay or bcdrock: no root rnat or vcgetation. SCORE 2. Pool Substretc Che re cteriz:tion 20 t9 ''18 .t7 16 15 t4 t3 t2 ll l0 9 8 7 6 543210 Majority of pools large- dccp; vcry few shallow. Shallow pools much more prevalent than deeD pools. Majoriry of pools small- shallow or pools absent. 3. Pool Variability SCORE 20 19 .18'. l7 16 151413t2u l0 9 8 7 6 5 4 3.2 I 0 Littlc or no cnlarsement of islands or poini bars and less than'5%o 4Oy" for low-grad ient strcams) ofthc bottom affccted bv sediment deposition. Somc ncw incrcase in bar formation. mostlv from grevcl, sand or finc sediment: 5-30% (20-50% for torv- gradicnt) ofthc bottom affected; slight deposition in pools. Moderatc deposition of new gravel, sand or linc sedimcnt on old and new bars; 30-50% (50-80% for low-gradient) of the bottom affcctcdi sedimcnt dcposits at obstructions. constrictions, and bcnds, ls rrrcdcratc tion of Heavy dcposis of fine material, incrcased bar dcvclopmcnt; more than 50% (80% for low- gradicnt) of the bouom changing frequenrly; pools almost absent duc to substantial scd imcnt dcposition. 4. Scdimcnt Deposition SCORE 20 19 t8 t7 t6 15 14 .13 t2 _lt l0 9 8 7 6 543210 Waler reachcs basc of both lower banks, and minimal amount of channcl substratc is Water fills >75% of the available channcl, or <25o2 ofchannel substratc is cxposcd. Water fills 25-75% of rhe availablc channcl, and./or rilTle substrates arc mostly cxposed_ Vcry littlc warer in channcl and mostly prescnt as st.anding pools SCORE 5. Channcl Flow Strtus ( L E E E E 6 a o L E L( o. 20 t9 18 l.t 16 15 14 13 t2 ll r0 9 8 7 6 543210 rnats and submcrged mixEvcn of IIABITAT ASSESSMENT FTELD DATA SIIEET-LOW GRADTENT STREAMS (BACK) Totel Score Condition Poor U2tcgorY MerginalSuboptimalOptimal Hrbitrt Parrmctcr Banks shorcd with gabion or cemcnt; over 80% of the strcam reach channclizcd and drsruptcd. lnstream habiut grcatly altercd or removcd cnttrcly. Channelrza(ion may bc cxtcnsrve: cmbankmcnts or shonng structurcs Dresent on both banks' ind 40 to 807o ofstrcam reach channclizcd and d isruptcd. Some channcltzation prescnt, usuallY ln areas ofbridgc abutments; cvidencc of Past channclization, r.c., drcdging, (gteatcr than past 20 Yr) rnay bc prcscnt, bu( rccent channclizatron ts not prcscnt. Channclization or drcdging abscnt or minimal; strcam with normal pattcm 5 4 3 2 1.010 9 8 7 615 14 13 12 ll20 -19 l8 l7 16 6. Channel Alteration SCORE Channcl straight: watcrway has bcen channclrzcd for a long d rstance. Thc bcnds in thc strcam incrcasc the strcarh lcngth2to lttmcs longer than if lt was rn a srrarght lrnc The bcnds ln thc stream increasc the strcam lcngth2to3trmcs longcr than if it was in a strarght Irnc. The bcnds in the stream incrcasc the strcam lcngth3to4times longcr than if it was in a straight Iinc. (Note - channel braiding is considcred norrnal in coastal plains and othcr low-lying arcas. This paramctcr is not casily ratcd in these arcas. 543210109876t5 l4 13 l2 ll20 19 '18 17 16 7. Channel Si nuosity SCORE Unstable; many erodcd arcas; "raw" arcas frcqucnt along straight scctions and bends; obvious bank sloughing: 60-100% ofbank has crosional scars Modentcly unstable; 30- 60% of bank in rcach has arcas of crosion: hi8h crosion potcntial during floods Modcratclv stablc: infrcqucntl small arcas of crosion mostly healcd ovct. 5-30Yo ofbank rn rcach has arcas of crosion. Banks stablc: cvidcncc ofcrosion or bank failurc absent or minimal; lrttle Dotcntial for futurc iroblcms. <5% ofbank affcctcd. 210543876l-cfl Bank l0 9 2 "l 0543I 7. 6fught Bank I0 9 8. Bank Strbility (score cach benk) SCORE - (LB) scoRE _ (RB) Lcss than 50% ofthe srcambank surfaccs covercd by vcgetation; drsruption of strcambank vcgetation is vcry high; vegetation has becn rcmovcd to 5 centimetcrs or less in avcrage stubblc hetght. 50-?0% ofthc strcambank surfaccs covcrcd by vcBe12tion; disruption obvious: patchcs ofbarc soil or closcly croppcd vcgetation comnK)n; less rhan one-halfofthc potential plant stubblc height rcmaining. 70-90% ofthc strcambank surfaccs covcrcd by nativc vcgeution, but onc class of plans is not wcll- reprcscnted: disruption cvidcnt but not affcctrng full plant growth potcntial to.ny Srcat cxlcnt: tnorc than onc- helf of thc potcntral plant stubb.lc. hcight rcrTBlntng. Morc lhan 90% of the streambank surfaccs and immediate riparian zone covcrcd by nativc vcgetation, includtng trccs, understory shrubs, or nonwoody macrophytes; vegetative disruption through grazrng or rnowrng mininral or not cvtdcnt: alrnost all planLs allowcd to grow naturallY. 2 t0543876t cft Bank l0 9. Vcgetetive Protcction (scorc each bank) Note: dctcrminc lcft or right side by facing downstream. SCORE - (LB) SCORE - (RB) I0. Riperien Vegctrtive Zone Width (score cach bank npanan zone) SCORE - (LB) scoRE _ (RB) 2t0 -- Width o[riparian zonc <6 mcters: little or no riparian vegetation due to human aclivrtrcs. 543 --- Width of riparian zonc 6- l2 mcters; human activitres havc impactcd zonc a grcat dcal. 876 1I-- Width of riparian zonc I 2- I 8 mctcrs; human activitics havc rmpacted zonc only mrnrmally. Right Bank l0 -- Width of riprrian zone >18 mctcrsi human activitics (r.c., parking lou, roadbcds, clcar{uts, lawns, or crops) havc not impactcd zonc. 2 I 0543876kft Bank l0 9 2 l0543876tught Bank l0 9 E L s '= d E L o ! 'o c E o L E L I I Epifaunal substrate/AiilnT:rt#ill,* quantiry and variety of natural structures in ' the stream, such as cobble (riffles), large rocks, fallen trees' logs and branches, and undercut banlls, available as refugia. feeding. or sites for spawning and nursery functions of aquatic macrofauna. A wide variety and/or abundance of submerged srructures in the stream provides macrohvertebrates and fish with a large number of niches, thus increasing habitat diversiry' As varieN and abundance of cover decreases' habitat structure becomes monotonous, diversity decreases. and the potential for recove.v- following disturbance decreases' Riffles and runs are critical for maintaining a variery and abundance of insects in most high-gradient streams and serving as sparvning and feeding refugia fo, certain fish. The extent and quatiry of the riffle is an impJrtant facror in the support of a healthy biological condition in irigl_graaienr streams. fuffles and runs offer a diversity of habit-at through variety of particle size. and. in many smallhigh- gradient strealns, will provide the most stable habitat' Snags and submerged logs are among the most productive habitat structure for macroinvertebrate colonization and fish refugia in lorv- gradient strearns. However, "new fall" rvill not yet be prepared for colonization. Pool Substrate Characterization (Low Gradient): Evaluates the type and condition of boftom substrates found in pools. Firmer sediment types (e.g., gravel, sand) and rooted aquatic plants support a wider variely of organisms than a pool substrate dominated by mud or bedrock and no plans. In addition, a stream that has a uniform substate in its pools will support far fewer types of organisms than a stream that has a variety of substrate types. 4. Sediment DePosition: ) 3 Pool VariabilitY (Low Gradient): Rates the overall mixture of pool types found in streams' according to size and depth. The four basic types of pools are large-shallow, large-deep, small-shallow, and small-deep' A stream rvith many pool types rvill support a wide variery of aquatic species. Riu"o with low sinuosity (ferv bends) and rntno,onor. pool characteristics do not have suflicient quantities and types of habitat to support a diverse aquatic community' General guidelines are any pool dimension (i'e', length' w-idth' oblique)lreater than half the cross-section of the stream for separatin! [arge from small and I m depth separating shallow and deep. Measures the amount of sediment that has accumulated in pools and the changes that have occurred to the stream bottom as a result of deposition. Deposition occurs from large-scale movement of sediment. Sediment deposition may cause the flormation of islands, point bars (areas of increased deposition usually at the beginning of a meander that increase in size as the channel is diverted torvard the outer bank) or shoals, or result in the filling of runs and pools. Usually deposition is evident in areas that are obstructed by natural or manmade debris and areas where the stream flow decreases, suc[ as bends' High levels of sediment deposition are symptoms of an unstable and continually changing environment that becomes unsuitable for many organisms. ca 5. Channel Flow Status: Channel Alteration: The degree to which the channel is filled rvith water' The florv status riill change as the channel enlarges (e.g., aggrading stream beds with actively rvidening channels) or as flow decreases as a result of dams and other obitructions, diversions for irrigation' or drought. When lvater does not cover much of the streambed' the urno,int of suitable substrate for aquatic organisms is limited' In high-gradient streams, riffles and cobble substrate are exposed; in low-giadient strealns, the decrease in water level exposes logs *d snugs, thereby reducing the areas of good habitat' Channel florv is Jspecially useful for interpreting biotogical condition under abnormal or lowered flow conditions. This parameter becomes important rvhen more than one biological index period is used flor surveys or the timing of sampling is inconsistent among sites or annual Periodiciry' 6 Is a measure of large-scale changes in the shape of the steam channel. Many streams in urban and agriculnrral ar6as have been straightened, deepened, or diverted into concrete charurels, often for flood control or irrigation purposes. Such streams have far fewer natural habitats for fish, macroinvertebrates, and plants than do naturally meandering streams. Channel alteration is present when artificial embankments, riprap, and other forms of artificial bank stabilization or structures are present; when the stream is very straight for significant distances; when dams and bridges are present; and when other such changes have occurred' Scouring is often associated with channel alteration. 7 Channel SinuositY (Low Gradient): Is a way to measure the sequence of riffles and thus the heterogeneity occurring in a stream. fuffles are a source of high- qualityhabitat and diverse fauna, therefore, an increased *"qrio"y of occurrence geatly enhances the diversity of the stream communicy. For areas where distinct riffles are uncommon, a run/bend ratio can be uscd as a measure of meandering or sinuosiry. A high degree of sinuosity provides for diverse habitat and fauna, and the stream is better able to handle surges when the stream fluchrates as a result of storms' The absorption of this energy by bends protects the stream from "*...iiu" erosion and flooding and provides refugia for benthic invertebrates and fish during storm events' To gain an apprcciation of this parameter in some streams, a longer segment oi'rea.h than that designated for sampling may be incorporated into the evaluation. In some situations, this parameter may be rated tiom vierving accurate topographical maps' The "sequencing" pattern of the stream morphotogy is important in rating this parameter. In headwaters, riffles are usually continuous and the presence ofcascades or boulders provides a florm of sinuosiry and enhances the structure of the stream' In "oxbow" streams oIcoastal areas and deltas, meanders are highly exaggerated and transient. Natural conditions in these streams or" r[iRing channels and bends, and alteration is usually in the formofflorvregulationanddiversion.Astablechannelisone that does not exhibit progressive changes in slope, shape' or dimensions. although short-term variations may occur during floods (Gordon et at. 1992). a 8. 10. Bank Stability (condition of banks): Measures rvhether the stream banks are eroded (or have the potential for erosion). Steep banks a-re more likety to collapse and suffer from erosion than are gently sloping banks, and are therefore considered to be unstable. Signs of erosion include crumbling, unvegetated banks, exposed tree roots, and exposed soil. Eroded banks indicate a problem of sediment movemenr and deposition, and suggest a scarcity of cover and organic input to streams. Bank Vegetative Protection: Measures the amount of vegetative protection afforded to the stream bank and the near-stream portion ofthe riparian zone. The root systems of plants grorving on strearn banks help hold soit in place, thereby reducing the amount of erosion that is likely to occur. This parameter supplies information on the ability oi the bank to resist erosion as rvell as some additional intbrmation on the uptake of nutrients by the plan6, the control of instream scouring, and stream shading. Banks that have full, natural plant grorvth are better for fish and macroinvertebrates than are banks rvithout vegetative protection or those shored up rvith concrete or riprap. This parameter is made more effective by defining the natural vegetation for the region and stream type (i.e., shrubs, trees, etc.). In areas of high grazing pressure from livestock or where residential and urban development activities disrupt the riparian zone. the gro"vth of a narural plant communiry is impeded and can extend to the bank vegetative protection zone. Riparian Vegetative Zone Width: Measures the rvidth of natural vegetation from the edge of the stream bank out through the riparian zone. The vegetative zone serves as a buffer to pollutants entering a stream from runoff, controls erosion, and provides habitat and nutrient input into the stream. A relatively undisturbed riparian zone supports a robust stream system: narrow riparian zones occur when roads, parking lots, tields, larvns, bare soil, rocks, or buildings are near the strearn bank. Residential developments, urban centers, golf courses. and rangeland are the common causes of anthropogenic degradation of the riparian zone. The Presence of "old field" (i.e., a previously developed field not currently in use), paths, and rvalkrvays in an otherwise undisrurbed riparian zone may be judged to be inconsequentia[ to destruction of the riparian zone. ln some regions of the country, an increase in the specified width of a desirable riparian zone is rvarranted. I 9 a