An Analysis of the Fish and Macrobenthos Along the Sand Island Ocean Outfall Using Remote Video: Vi

HANAU-S-96-002 C2

AN ANALYSIS OF THE FISH AND MACROBENTHOS ALONG THE SAND ISLAND OCEAN OUTFALL USING REMOTE VIDEO: VI. 1995 DATA

Richard E. Brock

PROJECT REPORT PR-96-06

March 1996

WATER RESOURCES RESEARCH CENTER UNIlVERSlTY OF HAWAI'I AT MANOA Honolulu, Hawai'i 96822 AUTHOR:

Dr. Richard E. Brock AssociateResearcher and FisheriesSpecialist Sea Grant Extension Service Marine Science Building 204 University of Hawai'i at Mhtoa Honolulu, Hawai'i 96822 Tel.: 808/956-2859 FAX: 808/956-2858

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NOTE: Pleaseindicate PR-9646 on checkor moneyorder for our reference. AN ANALYSIS OF THE FISH AND MACROBKNTHOS ALONG THE SAND ISLAND OCEAN OUTFALL USING REMOTE VIDEO: VI. 1995 DATA

Richard E. Brock

Project Report PR-9644

March 1996

PREPARED FOR Departmentof WastewaterManagement City and County of Honolulu Project Report for "The Assessmentof the Impact of OceanSewer Outfalls on the Marine Environment off Oahu, Hawaii" ProjectNo.: C39805 ProjectPeriod: 1 January1995-31 August 1996 Principal Investigator: RogerS. Fujioka

WATER RESOURCES RESEARCH CENTER University of Hawai'i at Minoa Honolulu, Hawai'i 96822 Any opinions.findings, and conclusions or recommendationsexpressed in thispublication are those of the author and do not necessarilyreflect the view of the Water ResourcesResearch Center, ABSTRACT

Becausethe diffuser of theSand Island Ocean Outfall lies below safe diving depths, a remotely controlled video camerasystem was used to determinethe statusof the fish and diurnallyexposed macrobenthos resident to thediffuser. The use of a remotelyoperated vehicle is stipulatedin theNational Pollutant Discharge Elimination System 301 h!waiver permit for the SandIsland Wastewater Treatment Plant. Video reconnaissance was completed over the entire 1,036m lengthof the outfall diffuser.Five visual"transects," which "sampled" approximately41% of the totaldiffuser length, were established on the diffuserpipe. Video sampling of the diffuser marine communitieswas carried out annually from 1990 to 1995. Onlya fewspecies of diurnallyexposed macroinvertebrates areevident on thevideotapes of the diffuser;the numbersare insufficient for any meaningfulanalysis. In 1995,25 fish species ,796 individuals!having an estimated biomass ranging from 19to 51 g/m~ mean30 g/m2! werecensused; in 1994,32 species,473 individuals!with a standingcrop from 16 to 46 g/m mean35 g/m2!were encountered; in 1993,22 species79 individuals!having an estimatedbiomass ranging from 6 to 39 g/m mean21 g/m2! were encountered;in 1992,31 fish species,936 individuals!having an estimated standing crop ranging from 39 to 77 g/m2 mean53 g/m2! were censused; and in 1991,28 species ,785 individuals!having a biomass ranging from 8 to 106 g/m2 mean 42 g/m2! were counted.Because the 1990 video census coveredonly the terminal183 m of the diffuser,whereas the later surveyswere spread out alongthe entire diffuser length,a directcomparison cannot be madebetween the 1990data and thedata for subsequentyears. In 1990,one "new" fish specieswas encountered for every22.9 rn2of substratumsampled and one fish wasseen for every5.6 m>;in 1991,it wasone new speciesfor every 13.1m2 sampledand one fish for every0.7 m>;in 1992,it wasone new speciesfor every10.3 m2 and one fish for every0.4 m2; in 1993,it wasone new species for every 17.3m2 and one fish for every3.9 m2;and in 1994it wasone new speciesfor every 10.2m2 and one new fish for every0.7 m2.The 1995census noted one new fish speciesfor every 14.7m> of substratumsampled and one fish for every0.7 m2.In the 1991-95period, measuresof the fish community number of species,number of individuals, and biomass! increasedfmm 1991to 1992,decreased in 1993,and haveoscillated annually since that time. From a statisticalperspective, changes in the meannumber of speciesper transectand the mean numberof individual fishesper transectare significant Kruskal-Wailis ANOVA!; changesin the biomass of fishes over the same period are not significant. These changesin the fish community are attributedto changesin the generalviewplane of videotapesrecorded in 1994 and 1995from that of earlier years,as well as to a changein the resolution of the videotape from which the data are derived. Poorer camera resolution results in lower counts; camera cameraresolution is affectedby local wind andcurrents interacting with the camera,tether, and support vesselas well as by water visibility. ControHingthese sources of variation inherent with the useof the remotelyoperated video system is difficult if not impossible.Until an alternative can be found, the remotely controlled video systemis the only low-cost means available to view the marine communities on the diffuser. Until a more accurate means of visual assessmentis available,the biological data generatedby the remotely operatedvideo camera shouldbe viewed asqualitative, with little statisticalrigor. CONTENTS

INTRODUCTION.

MATERIALS AND METHODS ..

RESULTS

DISCUSSION ..

REFERENCES CITED

Figure

1. Schematic of the 1,036-m-long Sand Island Ocean Outfall diffuser pipe showing the approximatelocations of the five transectsestablished in August 1991 and monitored annually using a remotely controlled video recording system..

Tables

1. Family and speciesof fishes censusedon five transectsalong the 1,036-m-long diffuser pipe of the Sand Island Ocean Outfall as delineated using a remotely controlled video camerasystem on 16 November 1995... 2. Summary of the diurnally exposedmacroinvertebrates censused on five video transectscarried out alongthe 1,036-m-longdiffuser pipe of the Sand Island Ocean Outfall on 16 November 1995 .. 3. Summary of diurnally exposedmacroinvertebrates censused on five transectsalong the 1,036-m-tongdiffuser pipe of the Sand Island OceanOutfall as delineatedusing a remotely controlled video camera systemin August of 1991 through 1994.. 4, Summary of the characteristics of five transects carried out at various points along the 1,036-rn-longSand Island OceanOutfall diffuser, with data from the fish censuses carried out at each transect in November 1995 .. 5. Fainily and speciesof fishescensused on five transectsalong the 1,036-m-longdiffuser pipe of the Sand Island OceanOutfall as delineated using a remotely controlledvideo camerasystem on 22 August 1991...... 6. Family and speciesof fishescensused on five transectsalong the 1,036-m-longdiff'user pipe of the Sand Island OceanOutfall as delineated using a remotely controlledvideo camerasystem on 28 August 1992...... 7. Family and speciesof fishescensused on five transectsalong the 1,036-m-longdiffuser pipe of the Sand Island OceanOutfall as delineated using a remotely controlled video camera system on 5 August 1993. 8. Family and speciesof fishes censusedon five transectsalong the 1,036-m-longdiffuser pipe of the Sand Island OceanOutfall as delineated using a remotely controlled video camerasystem on 10 August 1994...... 9. Comparative summary of fish community developmentmeasured over five yearsat five locations along the 1,036-m-longSand Island Ocean Outfall diff'user

vu 10. Summaryof the nonparametric Student-Newman-Keuls multiplerange teston ranked values of parametersmeasured in the fish community at fivepermanent transects along the 1,036-m-long Sand Island diffuser censusedin Augustof 1991through 1994 and November 1995 .. INTRODUCTION

In recent years controversy has arisen regarding the impact that sewageeffluent from the Sand Island Wastewater Treatment Plant may have on marine communities resident to the receiving waters. The outfall was constructed in 1975, and screenedsewage has been dischargedsince 1976.The oceanportion of the outfall is comprisedof 2,780 m of 2.1-m- diameterreinforced concrete pipe that terminatesin a 1,036-m-longdiffuser. The diffuser is madeup of reinforcedconcrete pipe of threediameters: 490 m of 2.1-m-diameterpipe, 271 m of 1.7-m-diameterpipe, and 275 m of 1.2-m-diameterpipe at the terminus.Along its Length, the diffuser, which lies in water from 68 to 73 m in depth,has 282 portsthat rangefrom 7.6 to 9 cm in diameter.The diffuser restson a gravelpad and has someballast rock placedat the juncturesbetween sections. Fishes and macroinvertebrates have taken up residencealong most of the length of the deep ocean outfall. This study has been undertakenin an attempt to semiquantitativelyascertain the impactsthat may be occurringto thc communitiesresident to the dischargeport areasof the outfall. This reportpresents a synopsisof the datafrom the sixth annualsampling effort carried out on 16November 1995 and comparatively analyzes these data with informationcollected annuaHy since 1991.

MATERIALS AND METHODS

A remotelycontrolled video camera was used to conductthe census because the fish and diurnally exposedmacroinvcrtebrate communities of interestto this studyreside in waters belowsafe diving depths.In addition,the system was used because thc waiverpermit issued by theU.S. Environmental Protection Agency/Hawaii Department of Healthrequites the use of a remotelyoperated vehicle. There are a numberof drawbacksas weH as positive aspects to using a video camera system to visually census fishes and diurnally exposed macroinvertcbrates.The drawbacksinclude problemswith cameraresolution, making species and size identificationsdif6cult, andthe problemof adequatelycontroHing the camerato focus- in onrapidly fleeing fishes, adding further difficulty to identificationproblems. On the positive side,a permanentrecord of theorganisms in thepath of thecamera is obtained.An additional benefitto usinga videosystem is thatit eliminatesthe need for divingto greatdepths. Thereare some weH-known problems with usingvisuaL census methods to assesscoral reeffish populations,regardless of whethera cameraor diveris in thewater conducting the census.One of theseis the simplefrightening of waryfishes on the approachof the diver or camera. Another is the underestimation of cryptic species such as moray eels family Muraenidae!and nocturnal species such as squirrelfishes family Holocentridae! and bigeyes or 'aweoweo family Priacanthidae!. This problem is compoundedin areas of highrelief and coral coveragethat affords numerousshelter sites. Species lists and abundanceestimates are more accuratefor areasof low relief, althoughsome fishes with cryptichabits or protective coloration,such as scorpionfishesor nohu family Scorpaenidae!and catfishes family Bothidae!, might still be missed.Another problem is the reducedeffectiveness of the visual censustechnique in turbidwater. This is compoundedby thedifficulty of countingfishes that movequickly or arevery numerous.Additionally, bias related to theexperience of thecensus takershould be considered in inakingcomparisons between surveys. Despite these problems, the visual censustechnique carried out by diversis probablythe most accurate,nondestructive assessmentmethod currently availablefor counting diurnally active fishes Brock 1982!.Use of a remotelycontrolled video system to obtaincensus data compounds many of the above problems,but it is probablyone of themost cost-effective methods available for assessingfish communitiesat depthsbeLow safe diving limits. Otherthan exposed sessile species corals in shallowwater and some sponges in deeper water!, most tropical marine invertebratesare cryptic, remainingunder shelteruntil darkness whenthey emerge to feed.Only a fewmotile macroinvertebrates remain fully exposedduring theday; among these are some holothurian sea cucumber! and echinoid seaurchin! species. Problemswith speciesidentification preclude the enumeration of mostof thediurnally exposed invertebrates.Identification of holothuriansis basedon a microscopicexamination of skin spiculeconfiguration, and spicules are also used for theidentification of sponges.Thus, in this study,the identification and enumeration of exposedmacroinvertebrates ate confined to large arthropods spiny lobsters!and sea urchins; as for speciesof holothurianspresent along the SandIsland diffuser pipe, educated"guesses" are made. This study utilized a remotely controlled video systemto visually assessthe fish and macroinvertebrate populations resident to the diffuser pipe. The video "transect" was undertakenby the OceanographicTeam of the Departmentof WastewaterManagement, City and County of Honolulu. In the first threeannual surveys, the video cameragenerally traveled from 0.5 to 1.5 m abovethe diffuser pipe, occasionallymoving to the right or left side and down! to surveythe substratumalongside the pipe, The cameraviewed a pathfrom about 1.5 to 3 m in width. For purposes of data analysis, we assumedthat the camera path was approximately2 m in width, and we attemptedto count only fishes seenin this path. At times, the camera would tilt up toward the horizon!, allowing a viewing aheaddown the pipe, Visibility under thesecircumstances ranged from about0.5 m in a dischargeplume! to about 8 m, which is approximatelythe length of one pipe section.In the fourth 993! survey, the cameraroughly followed the samepath, but on occasionit roseto about4 m abovethe pipe. In doing so, a widerfield of view was attained,but with the small averagesize of fish presentthis meanta decreasein resolutionwith greaterheight above the pipe, resulting in a decreasein apparentabundance of fishes. The path of the camerain the 1994and 1995surveys was quite different. The camera remainedalong one inshore! sideof the pipe while traveling toward the outfall terminus,and on reaching the terminus, the camera was moved to the opposite offshore! side, for its travel back to the beginningof the diffuser. The censusesfor the 1994and 1995surveys were carried out at each of the five transectsites on the offshore side of the diffuser only, to make data betweensurveys comparable. The cameragrossly underestimates the numberof fish and invertebrates,thus everything seen in an arbitrary 2-m-wide path was counted, regardless of whether it was encountered directly below the camera as when viewing from above!or severalmeters ahead as when the camera is in a horizontal position!. The fish census involved not only the counting of populationsbut alsothe estimating of lengthsof all fishesfor lateruse in calculatingstanding crop. The standing crop of all fishes was estimatedby use of linear regressiontechniques Ricker 1975; Brock and Norris 1989!. Species-specificregression coefficients have been developedover the last 30 years by the author and others at the University of Hawaii, the Naval UnderseaCenter seeEvans 1974!,and the Hawaii Division of Aquatic Resourcesfrom weight and body length measurementsof capturedfishes; for many species,sample sizes were in excess of a hundred individuals.

RESULTS

Video "transects" of the fish communities resident to the Sand Island diffuser pipe have been carried out on six occasions:7 November 1990, 22 August 1991, 28 August 1992, 5 August 1993, 10 August 1994,and 16 November 1995.The November 1990survey only covered the final 183 m of the 1036-m-longdiffuser pipe. In the more recent surveys,the cameracommenced just shorewardof the first dischargeport on the diffuser and "sampled"the fish and macrobenthosfor the entire diffuser length.The 1991survey tape was viewed several timesto determinewhere representative transects could best be established. Five transect sites selectedas being representative sections of the diffuserpipe were sampled using the visual censustechnique. These transects were locatedusing known points on the pipe and by countingsections of pipe from thosepoints. The five transectsites were again sampled in subsequentsurveys, thus allowing for datacomparison between years. Thelocation of eachtransect is shownin Figure1. The transects range from 44 to 110m in length;thus, in total,approximately 848 m> of substratumwere sainpled in thissurvey. The resultsof all fish censusesare presentedin Table 1, aadthe datafor eachtransect are discussed below. In tallying the numberof speciesseen on a giventransect, all fishes that could not be positively assignedto a givenspecies were lumped into groups such as "labrid unidentified"!; in thetally of species,each of thesegroups was counted as a singlespecies, even though more than one speciesmay have beenpresent. The diurnaHyexposed macroinvertebrates that were present ia each transect area are tallied in Table 2, and the macroinvertebrate census data from previousannual surveys are presented in Table 3 for comparativepurposes. Transect1 commeaced58 m downfrom the beginningof the diffuser pipe andcontinued for approximately95 m alongthe pipe toward the terminus Figure 1!. This transectsampled 13.5sectioas of thc 2.1-m-diameterdiffuser pipe. The depth at thetop of thc diffuserpipe was approximately 68.5 m at the start of the trazmct and about 70.1 m at the end. Eleven speciesof fish 53 individuals! were notedon this transect,and the biomasswas estimatedat 19 g/m>.This amountsto one new speciesencountered for every 17.3m> of substratumsampled and one individual fish seenfor every0.8 m>.Of thespecies that could be identified, the most abundanton this transectwas the damselfish Chroniis sp., probably C. hanui and/or C. agilis!. The unidentified wrasse labrid unidentified! was also commonon this transect. In terms of standing crop, three bridled triggerfish or humuhumu mimi Sufgamenfraenatus! accountedfor 23% of the total. Two macroinvertebratespecies two individuals! were censusedon this transect Table 2!. Of notewas a singlespiny lobsteror 'ula Panulirus marginatus!estiaiated to weigh0.5 kg. Transect 2 commenced355 m down from the beginning of the diffuser pipe in about 71 m of water and ended91 m down the pipe from that point Figure 1! in approximately 71.3 m of water depth to thc top of thc pipe!. This transectsampled 12.5 sections of the 2.1- m-diameterportion of the diff'userpipe. Fourteenspecies of fishes were censused Table 1!; this translatesto oaenew species seen for every13.0 m> of substraaimsampled. In total,433 individualfishes were counted, and one new fish wasseen for every0.4 m>of substratum sampled.Again, thc most commoa fish speciesseen was the damselfish Chrornis sp. 62% of the total!. Unidentified wrasses comprised 10% of the total number of fishes seen. Important speciesby weight were three large yellowfin surgeonfishor pualu Acanthurus xanthopterus 35% of the total weight! and a single spiny puffer or 'o'opu 'okala Diodon holocanthus 18% of the total weight}. The biomassof fisheson Transect2 wasestimated at 37 g/m>.One macroinvertebrate species Chondrocidaris gigantea! was seen on this transect Table 2!. '0 CL

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III O» III R Q .Olg CUJ Vl III > mg Q>o U < o Ol C0 TABLE1. Family and species of fishes censused onfive transects along the 1,036-m-long diff'userpipe of theSand Island Ocean Outfall as delineated using a remotelycontrolled video camerasystem on 16 November1995. Areas sampled on the five transectsvaried: 190m2 for Transect1, 182m2 for Transect2, 220m2 for Transect3, 168m2 for Transect4, and88 m2 forTransect 5.The numbers of individuals of each species censused are given in thebody of the table.Totals for numbersof speciesand individuals and an estimate of biomassfor each transect are given at the foot of the table.

FAMILY and Species

MUM~ AE Gymnothoraxsp, SEMVPHDAE Pseudanttuassp. 35 148 45 62 CARANGIDAE Canuu ignobilis LUTJANIDAE Lutjanus kasmirtt 25 MULUDAE Parupeneus multifasciatus 10 Parupeneuspleurostigma 1 PRIACANTHIDAE Priacanthussp. CK~DONTIDAE Chaetodon kleinii Chaetodon miliari s Chaetodonsp. POMACAÃTHIDAE Centropyge!Bheri ?! POMACENTRIDAE Chromis sp. 198 601 54 Pomacentrid unidentified 10 23 3 LAB RIDAE Bodianus bi lunulatus Macropharyngodongeqghp ?! Anampses chrysocephalus Labrid unidentified 27 65 13 ACANTHURIDAE Acanthurusxanthopterus Acanthurussp. BALISTIDAE S~n fruensttus MONACANTHIDAE Cantherhines dumeritu DIODONTIDAE Diodon holocanthus CANTHIGASTEMDAE Canthigaster cinctus Canthigaster sp. Unidentified Fish

Total No. of Species ll 14 14 9 10 Total No. of Individuals 253 433 882 128 100 Biomass 8/m~! 19 37 21 24 51 TABLE 2. Summary of the diurnally exposed macroinvertebratescensused on five video transectscarried out along the 1,036-m-longdiffuser pipe of the SandIsland OceanOutfall on 16 November1995. The numbersof individualsof eachspecies censused are given in the bodyof thetable. Totals for numbersof speciesand individuals for eachtransect are given at the foot of the table.

TtallMCt PHYLUM and Species

ARTHROPOD A Panuli rus marginatus

ECHlNODERMATA Bohadschia vitiensis ?! Chondmcidans gigantea Holothuna atra l6 Tri pru.ustes grati lia l

Total No. of Species 3 3 Total No. of individuals 10 21

Seventy-three meters from the end of Transect 2, Transect 3 was established see Figure 1!. The ~ater depthat the beginningof the transectwas 71.3 m to the top of the pipe; at the end of the transectat 110 m away,it was 71.9 m. Transect3 sampled2.5 sectionsof the 2.1-m-diameterportion of the diffuser pipe and 12.5 sectionsof the 1.7-m-diameterportion. Fourteenspecies of fishes were countedand one new fish specieswas seenfor every 15.7m2 of substratumsampled. The numberof individual fishesencountered on this transectwas 882, and one new fish was seenfor every 0.2 m2 of substratumsampled. The most abundantfish specieson this transectappeared to be Chromissp. 8% of the total! and the brightly colored seabass Pseudanthias sp. 7% of the total!. The standingcrop of fishes was estimatedat 21 g/m~, 38% of which was comprisedof Pseudanthiassp. and 22% of unidentified wrasses labrid unidentified!. Table 2 presentsa summaryof the macroinvertebratesencountered on Transect3; threespecies 0 individuals! werecounted, including a single0.5-kg spiny lobster Pantdims tnarginatus!. Transect 4 was established 161 m from the end of Transect 3 toward the diffuser terminus Figure 1!. It commencedat a depthof about70.7 m depthto the top of the pipe! and endedat a depthof 70.1 m. Transect4 sampledabout 84 m of the diffuser pipe, covering 2.5 sections of the 1.7-m-diameterportion of the pipe and 9 sections of the 1.2-m-diameter portion. In total, nine speciesof fishes 28 individuals! were seenat this station. Equating thesefigures to the areasampled results in onenew fish specieswas seen for every 18.7m2 and one fish encounteredfor every 1.3 m>. The most abundant fish on Transect 4 was Chromis sp., which comprised42% of the total numberof fishes seen,and Pseudanthiassp., TABLE3.Summary ofdiurnally exposed macroinvertebrates censusedon five transects along the1,036-m-long diffuser pipe of the Sand Island Ocean Outfall asdelineated using a remotely controlledvideo camera system in August of 1991through 1994. Areas sampled onthe five transectsvaried: 190 m2 for Transect1, 182m2 for Transect2, 220m> for Transect3, 168m2 forTransect 4,and 88 m2 for Transect 5,The numbers ofindividuals ofeach species are given in thebody of thetable. Totals for numbersof speciesand individuals for eachtransect are given at the foot of the table.

1991 1992 PHYLUM and Species Tfansecf. Ttansect 1 2 3 4 5 2 3 4 5

ARTHROPODA Panulirus marginatus

ECHINODERMATA Bohadschia vitiensis Cuicita novaeguineae Diadema setosum 7 Holothuna atttt 2 2 32 12 1 14 11 4 Tripneustesgratilla 3

Total No, of Species 2 2 2 1 2 2 2 1 1 Total No. of Individuals 9 3 33 12 4 2 3 21 11 4

1993 1994 PHYLUM andSpecies T~ Ttansect 1 2 3 4 5 2 3 4 5

ARTHROPOD A Panulintsmarginatus

ECHINODERMATA Bohadschia vitiensis ?! 1 1 2 3 Chontroctdansgtganaaa 1 1 1 Culcita novaeguineae 1 1 Holothuna atns 2 2 21 23 7 4 16 10 Tripneustes gnttilla 1 1

Total No. of Species 4 3 4 3 1 2 1 3 1 1 Total No. of Individuals 5 4 25 27 7 2 1 6 16 10 which madeup 35%of the total.The standingcrop of fishesat Transect4 wasestimated at 24 g/m>,and the species contributing most heavily were a singlemoray eel or puhi Gymnothoraxsp. 14%of the total! andthree bridled triggerfish or humuhumumimi Su@amenfraenatus 44%of thetotal!. Three macroinvertebrate species Holothuria atra, 1'ripneustesgrarilla, and bohadschia vitiensis [? J! were seen on this transect Table 2!. Transect5 coveredthe final 44 m of the diffuserpipe andthe terminus.This transect sampled5.5 sections of pipeand the diffuser terminus. It commencedata depthof about71 m depthto thetop of thepipe! and ended at a depthof approximately69.5 m atthe top of the diffuserterminus. Ten species of fishes00 individuals!were encountered during the census. As for areasampled, one new species of fish wasseen for every8.8 m> and one new fish for every0.9 m>. The most abundant species seen included Pseudanthias sp. 2% of thetotal! and Chromissp. 6% of the total!. The standingcrop of fisheson Transect5 wasestimated at 51 g/m>,and the speciescomprising the greatestproportion were two Diodon holocanthus 1% of thetotal!, a singleAcanthurus xanthopterus 2% of thetotal!, and a singlewhite trevaUyor papio Caranx ignobilis 20%of thetotal!. Only one macroinvertebrate species the black seacucumber Holothuria atra! wasseen on this transect Table 2!. The results of the five transectscarried out in 1995 using the video cameraare sumniarizedin Table 4. Thevisual fish census transects from the video shot in Augustof 1991 through1994 covered the same five sections of thediffuser pipe as those in thepresent survey; thusdata for the five yearscan be comparativelyanalyzed. The 1991through 1994 data are presentedin Tables5 through8, respectively,and data for ail five yearsare summarized in Table9. In general,the 1992and 1994 census data showed higher numbers of speciesthan the 1991and 1993data. These differences may be due to ! bettercontrol of the remotely operatedcamera in viewingthe substratum or ! improvedability to identifyfishes recorded with a videocamera with the passageof time. Froma reviewof all tapesfor 1991through 1995,it is suggestedthat maximumvisibility was aboutthe same 8 m! for all yearsbut coverageby the camerawas better in 1992and 1994.The control of the camera steadinessand areacoverage! in 1993appeared to be less than in other years,and the resolutionin the 1993 videotape was considerably less. Average visibility in 1993 was about 3 m, less than in previous surveys.The net result is an apparentdecrease in fish speciesand individuals in the 1993 data. As noted above, Table 9 presentsa summaryof the parametersmeasured in the fish community along the SandIsland diffuser for the five samplingdates. Statistically significant differenceswere found for the meannumber of fish speciesencountered on a transectamong the five years Kruskal-Wallis ANOVA, d.f. = 4, p ! 0.004; see Siegel 1956!. The nonparametricStudent-Newman-Keuls multiple rangetest on rankedvalues of eachvariable

10 TASLE4. Summaryof thecharacteristics of five transectscarried out at variouspoints along the 1,036-m-long Sand Island Ocean Outfall diffuser, with data from the fish censusescarried out at eachtransect in November1995, Means are presented in the right column.

Transect Mean

Transect Len8th m! 95 91 110 84 44 85

AreaSampled m2! 190 182 220 168 88 170

No. of Species 11 14 14 9 10 12

No. of Individuals 253 433 882 128 100 359

No. of mi SampledPer New Species 17,3 13,0 15,7 18,7 8.8 14.7

No. of mi SampledPer Intbvidual 0.8 0.4 0.2 1.3 0.9

Biomass g/m~! 19 37 21 24 51 30

SAS Institute, Inc. 1985! was used to delineatestatistically significant differencesfor the meannumber of fish speciesper transectamong the five years.These results are presentedin Table 10; only the meannumber of fish speciesfor 1993differed significantly from the other four years. The same analyseswere performed for the mean number of individual fishes censusedon a transect.Again, the Kruskal-Wallis ANOVA pointed out that a statistically significantdifference exists in the meannumber of individual fishesper transectamong the five years d.f. = 4, p > 0.008!. The Student-Newman-Keuls multiple range test found no statisticallysignificant differences among the five years.No statisticallysignificant differences were found in the mean standing crop of fishes encounteredon a transectamong the five samplingdates Kruskal-Wallis ANOVA, d.f. = 4, p ! 0.13, not significant;see also Table 10!. The 1990videotape only recordedthe fishes presenton the final 183 m of the diffuser Brock 1992a!;thus the data are not directly comparableto the 1991through 1995transect information. In the 1990study, Brock 992a! found 16species of fishesand one new species for every22.9 m2 of substratumsampled, and 67 individualfishes and one new fish for every 5.5 m . Thestanding crop of fisheswas estimated at 17g/m2. Based on thecriteria used i,e., biomassand number of squaremeters sampled to encountera newspecies or an individual fish!, the fish communitiesalong the diffuser pipe werefound to increasefrom 1990to 1991.

11 TABLE5. Familyand species of fishescensused on five transectsalong the 1,036-m-long diffuserpipe of theSand Island Ocean Outfall as delineated using a remotelycontrolled video camerasystem on 22 August 1991.Areas sampledon the five transectsvaried: 190 m2 for Transect1, 182m2 for Transect2, 220m~ for Transect3, 168m2 for Transect4, and88 m2 . forTransect 5. Thenumbers of individualsof eachspecies are given in thebody of thetable. Totals for numbersof speciesand individualsand an estimateof biomassfor eachtransect are given at the foot of the table. Data from Brock 1992b!

Tfansect FAMILY and Species

MUlVtENIDAE Gymnothorax flavimarginatus SERIVJ~AE Pseudanthiasthompsorti 18 18 MRGONIDAE Apogon kallopterus ?! LUT JANIDAE Lutj anus kasmi ra 5'IULLIDAE Parupeneus multifascuuus CHAEI'ODONIIDAE Chaetodon multicinctus Chaetodon kleinii ?! Chaetodon sp. Heniochus dI phreutes ?! POMACAYI'HIDAE Holocanthus arcuatus POMACENTRIDAE Chromis hanui 41 23 Chromis verator ?! 1 Chromis sp, 31 118 91 LAB RIDAE Bodianus bilunulatus Tlutlassomaduperrey ?! Thaktssoma sp. 1 Pseudojuloides cerasinus 4 11 19 Labtid unidentified 69 50175 62 41 ACANTHURIDAE Acanthurus dussumi eri Acanthurus xanthopterus Acanthurus sp, ZANCLIDAE Zanclus cornutus 8ALISHDAE Sujfl'amenfraenatus MONACANTHIDAE Candu rhines dumeri lii TET RAODONTIDAE Arothron hispidus Arothron mehagris ?! CPDPfMGASTERIDAE Canthigaster jactator ?! Canthigaster coronata

Total No. of Species 12 13 14 ll il Total No, of Individuals 169 217 1,045 147 207 B iomass g/m2! 32 8 55 10 106

12 TABLE6. Familyand species of fishescensused on five transectsalong the 1,036-m-long diffuserpipe of theSand Island Ocean Outfall as delineated using a remotelycontrolled video camerasystem on 28 August 1992.Areas sampledon the five transectsvaried: l90 m> for Transect1, 182m2 for Transect2, 220m2 for Transect3, 168m2 for Transect4, and88 m2 for Transect5. The numbers of individualsof eachspecies are given in thebody of thetable, Totals for numbersof speciesand individuals andan estimateof biomassfor eachtransect are given at the foot of the table. Data from Brock 1993a!

FAMILY and Species

M%V~>AE G mnothorarflavimarginatus G'ymnothorax sp. AULOSTOMIDAE A ulostomus chinensis PRIACANTHIDAE Priacanthussp. ?! SER1VtNIDAE Pseudanthiasthompsoru 24 158 41 148 LUTJANIDAE Lujtonus kasmira 261 Lutjanus fuivus 2 2 Lujtanussp. ?! 722 153 375 MULLIDAE Parupcneusmultifasciatus 24 32 CHAETODONHDAE Chaetodonnudticinctus ?! Chactodonldeinii ?! Chaetodonsp. POMACANTHIDAE Holocanthus arcuatus 1 Centrrrpygcsp. ?! 16 POMACENTRIDAE Chromis hanui 52 31 28 19 8 Chromissp. 76 126 91 55 il Potnacentnd unidentified ll 3 LAB RIDAE Bodianus irilunulatus 1 Thaiassomaduperrey ?! 23 17 8 Pseudojuloidcscenxsinus 3 15 Gomphosusvari us 3 Macropharyngodon1 tqghry 1 3 Halichoercsornatisstmus '?! 1 1 1 Labtid unidentified 111 83 56 30 ACANTHURIDAE Acanthurus dussumr'crt' ZANCUDAE Zanclus cornutus BALISTIDAE

MONACANTHIDAE Cantherhines dumeritii TEI'RAODONTIDAE Arothronhispidus CANTHIGASTERIDAE Canthigastcrjacraaar ?!

Total No. of Species 15 20 23 13 Total No, of Individuals 308 593 1,144 325 566 Biomassig/mi! 39 45 58 77

13 TABLE7.Family and species of fishes censused onfive transects along the 1,036-m-long diffuserpipe of the Sand Island Ocean Outfall as delineated using a remotelycontrolled video camerasystem on 5 August1993. Areas sampled on the five transectsvaried: 190m for Transect1, 182m2 for Transect2, 220m2 for Transect3, 168m for Transect4, and88 m> forTransect 5.The numbers ofindividuals ofeach species are given in thebody of the table. Totalsfor numbersof speciesand individuals and an estimate of biomassfor eachtransect are given at the foot of the table. Data from Brock 1993b!

FAMILY and Species Transect

SERRAAIDAE Pseudanthutsthompsoni

LUTJANIDAE Lu janus kasmira 14

MULLIDAE Parupeneus multifasciatus

CHP~ODONTIDAE Chaetodonsp, Heniochusdiphreutes

POMACENTRIDAE Chromis hanui 14 Chromis sp. 6 8 24 44 Pomacentrid unidentified 5

LAB RIDAE Pseudojuloidescerasinus ?! Tha/assomasp. 2 2 Labtid unidentified 18 15 34 10 ACNVTfIURIDAE Acanthurusxanthopterus Acanthurussp. Ctenochaetusstrigosus ?! JVasounicornis ?!

ZANCLIDAE Zanclus cornulus

BAUSTIDAE Sug%uaenfimnatus Rhinecanthus aculeatus ?!

MONACANI'HIDAE ' Cantherhines dumerilii

TETI&ODONTIDAE A rothron hispidus

CAN THIGASTERIDAE Canthigasterj actator Candugaster coronata

Total No. of Species 11 10 ll 8 9 Total No, of Individuals 42 52 126 23 36 Biotnass 8/mt! 6 12 ll 39 39 TABLE8. Familyand species of fishescensused on five transectsalong the 1,036-m-long diffuserpipe of theSand Island Ocean Outfall as delineated using a remotelycontrolled video camerasystem on 10 August 1994.Areas sampledon the five transectsvaried: 190 m2 for Transect1, 182m2 for Transect2, 220m2 for Transect3, 168m2 for Transect4, and88 m2 for Transect5. Thenumbers of individualsof eachspecies are given in thebody of thetable. Totals for numbersof speciesand individualsand an estimateof biomassfor eachtransect are given at the foot of the table. Data fTomBrock 1993b!

Tl'ansect FAMILY and Species

MUR~DAE Gymnothorassp, AULOSIOMIDAE Aulostomus chinensis SERKVADAE Pseudanthiassp. IS 91 35 103 /tiPOGONIDAE Apogon kallopterus 17 CAIVtNGIDAE Caranxmclampygus LUI3ANIDAE Lutj'anus kasmira 72 20 MUUJDAE Parupencus multifasciatus hfulIoidichthysvanicolensis

Chactodon klcinii Chaetodon mi liars's POMACAYTHIDAE Centropygejishcri POMACENIRIDAE Chromis hanui IS 16 64 14 4 Chromis agilis 9 7 Chrontis sp. 141 90 339 77 22 Pomacenttid unidentified 6 19 4 4 I Plectroglyphidodonj ohnstonianus ?! I LAB RIDAE Pscudojuloidcscerasinus ?! IS 15 12 Bod/anus bilunulatus Anampscschrysocephalus 1 Halt'chocres ornatissimus 3 Labtid unidentified 15 2250 IS ACANI'SUNDAE Acanthurussp. /Vaso unicornts ?! /paso brevi rostris ZANCLIDAE 2anclus cornutus 8ALISTIDAE

MONACANTMDAE Canthcrhines diunerilii Alurcrascripta lEIRAODONIIDAE Arothron hispidus CAYIHIGASIHUDAE Canthigatter j actator Canthigastercoronata

Total No. of Species 14 16 24 16 14 Total No. of Individuals 225 194 691 IS6 177 Biomass S/mi! 16 46 42 43 5s TABLE9. Comparativesummary of fishcommunity development measured over five yearsat five locationsalong the 1,036-m-longSand Island Ocean Outfall diffuser. Dataare drawn from Tables1 and5 through8, andgrand means for thefive transectsare given at thefoot of the table.

No, of S ies No. of Individuals Transect 1991 1992 1993 1994 1995 1991 1992 1993 1994 1995

12 15 11 14 11 169 308 42 225 253

13 20 10 16 14 217 593 52 194 433 14 23 11 24 14 1,045 1,144 126 691 882 11 13 8 16 9 147 325 23 186 128 11 12 9 14 10 207 566 36 177 100

Means 12 17 10 17 12 357 587 56 295 359 Biomass m2! Transect 1991 1992 1993 1994 1995

32 39 6 16 19

8 45 12 46 37

55 58 11 42 21

10 44 39 43 24

106 77 39 28 51

42 53 21 35 30

TABLE 10. Summaryof the nonparametricStudent-Newman-Keuls multiple range test on rankedvalues of parametersmeasured in the fish communityat five permanenttransects along the 1,036-m-long Sand Island diffuser censusedin August of 1991 through 1994 and November of 1995. The meanson a per transectbasis are given in the body of the table. Horizontal lines connect means that do not differ significantly; breaks in the line show significant differences p ! 0.05!.

Year and Means

Mean No. of SpeciesPer Transect 1994 1992 1991 1995 1993 17 17 12 12 10

Mean No. of Individuals Per Transect 1992 1995 1991 1994 1993 587 359 357 295 56

Biomass g/m2! 1992 1991 1994 1995 1993 53 42 35 30 21

16 DISCUSSION

Since 1991,the estimatedstanding crop of fishes rangedfrom 6 Transect 1, 1993! to 106g/m> Transect5, 1991!.The overall mean standing crop all years!is 36 g/m>:in 1991,it was42 g/m>;in 1992,53 g/m>;in 1993,21 g/m>; in 1994,35 g/m>;and in 1995,30 g/m>. The censusof Transect5 in 1991resu1ted in a highbiomass estimate 06 g/m~!;this was due to a largeresident yellowmargin moray eel or puhi paka Gytnnothoraxflavimarginatus! and two tablebossor 'a'awa Bodianusbilunulatus! that wanderedthrough the path of the video camera.If these three fishes are removedfrom the biomassestimate, the standingcrop for 1991becomes 24 g/m>.The grand mean estimate of thebiomass would then be 33 g/m> all years combined!. Goldman and Talbot 975! suggestedthat a reasonablemaximum biomass of coral reef fish is about200 g/m>.Space and cover are importantagents governing the distributionof coral reef fishes Sale 1977!.Similarly, the standingcrop of fisheson a reefis correlatedwith the degreeof vertical relief. Thus Brock 954!, using visual techniqueson Hawaiian reefs, estimatedthe standing crop of fishes to range from 4 g/mz on sand flats to a maximum of 186g/m> in an areaof considerablevertical relief. The large variation seen in standingcrop of fisheson coral reefsis tied to the structuraldiversity of the habitat Risk 1972!.Some authors Risk 1972; Gladfelter and Gladfelter 1978; Brock et al. 1979; Ogden and Ebersole 1981; Anderson et aL 1981; Shulman et al. 1983; Shulman 1984; Eckert 1985; Walsh 1985; Alevizon et al. 1985!view reef structureas an importantfactor in determiningthe speciescomposition of coral reef fish communities.Thus someevidence suggests that both the biomassand species compositionare influencedby the complexityof the local topography. The substratumin the vicinity of the SandIsland outfall diffuser appearsto be a sandy plain. Sandhabitats typically supporta low diversity of fish speciesand biomass, i.e., biomass rangingfrom 0.5 to 20 g/m> Brock 1954;Brock et al. 1979;Brock andNorris 1989!.The diffuser pipe situatedon a gravelpad with someballast stoneplaced at the endsof most pipe sectionsprovides additional local topographicalstructure, which hasprobably influencedthe developmentof the fish community.Because of the small gradedsizes used, the ballast stone and gravel pad provide only small-scaleshelter. Small-scaleshelter favors speciesthat are either smail as adultsor juveniles of larger species.The averagesize of the fishescensused in this survey supportsthis contention.Additionally, many of the larger fishes seen especially Acanthurusxanthoptems! were in the vicinity of known areasof topographicalrelief, suchas the set of large tires near the start of the diffuser pipe, the discarded55-gallon drum, and the constructiondebris. The accuracyof censusingis lesswith smallerfishes.

17 The data from 1991to presentsuggest that there is considerablevariation in the fish and invertebratescounts over time. The identification of somespecies of fishes in this study was not difficult becauseof their size such as adult Acanthurus xanthopterus and Bodianus bilunulatus! or color such as Zanclus cornutus!. In past years some speciessuch as the bluelinedsnapper or ta'ape Lujtanus kasmira!occurred in suchhigh abundance that species identificationwas not difficult. Despitethis, a numberof fisheshave consistently been difficult or impossibleto identify becauseof ! poor cameraresolution, ! their rapid movementto cover, ! their small size, or ! their being on the peripheral field of view. Someof these fishes were small damselfishes probably ChroInis hanui or C. agilis!, small Lujtanus sp. probably Lujtanus kasmira!, and small wrasses family Labridae, possibly Cheilinus bimaculatus, Pseudocheilinusspp., Thalassomaspp., or Pseudojuloides cerasinus!. As for abundance,these unidentified fishes are important, but they generallycontribute little to the biomass estimates because of their small size. The countsfor the parametersmeasured in the 1994fish censusappear to be higher than thosefor 1993.The changein operationof the cameracommencing in 1994to view the fish community along eachside of the diffuser rather thancontinually crossingover the pipe from side to side as donein previousyears may accountfor someof the increase.Thc bettercamera resolution in 1994, comparedwith 1993,is probably anotherreason for the increasein the apparentabundance of fishes on the diffuser. In 1995the cameraagain traveledconsistently along one side of the diff'user, but becauseit was often elevatedsuch that identification of fisheswas difficult, lower estimatesof abundanceand biomass resulted. Overall, the variability in fish countsover the yearsis influencedby manyother factors.Manipulation of the remotely operatedand tetheredvideo camerais difficult, especiallywhen consideringthat more than 60 m of electricalcable are between the cameraand the operatoron the surfacevessel. Not only doesthe wind createdifficulties with keepingthe surfacevessel on station,but currentsmay interact with the cable and camerabelow. Thesefactors serve to move the cameraaway from the area of interest, maltmg accuratecensusing of fishes and invertebrateson the resulting videotapevery difficult at best.These problems, coupled with highly variableturbidity due to the interaction of material dischargedfrom the diffuser ports with local currents, result in highly variablevisibility that servesto addvariability to the counts. Controlling the sourcesof variationinherent with the usc of the remotelycontrolled video systemis difficult if not impossible.The remotelycontrolled video cameraused for the annual inspectionby Departmentof %astewaterManagement personnel probably provides sufficient resolution and information with respectto the physicalstatus of the outfall and diffuser, but it appearsto be inadequatefor monitoringthe statusof fish andmacrobenthos on thediffuser, Until an alternative can be found, the remotely operatedvideo systemis thc only low-cost

18 means available to view the marine communities on the diffuser. Until a more accurate means of visual assessmentis available,the biologicaldata generated by the remotelycontrolled video camerashould be viewedas qualitative, with little statisticalrigor.

REFERENCES CITED

Alevizon, W., R. Richardson,P. Pitts, and G. Serviss. 1985.Coral zonation and patternsof communitystructure in Bahamianreef fishes.Bull. Mar. Sci. 36:304-318.

Anderson, G.R.V., A.H. Ehrlich, P.R. Ehrlich, J.D, Roughgarden,B.C. Russell, and F.H. Talbot. 1981.The communitystructure of coral reef fishes.Am. Nat. 117:476-495. Brock, R.E. 1982. A critique on the visual census method for assessingcoral reef fish populations.BulL Mar. Sci. 32:269-276.

Brock, R.E. 1992a.An analysisof the fish communitiesalong the Sand Island deep ocean outfall using remote video I. 1990 data. Special Rep. 04.02:92, Water Resources ResearchCenter, University of Hawaii at Manoa,Honolulu, Hawaii. 6 pp. Brock, R.E. 1992b.An analysisof the fish communitiesalong the Sand Island deep ocean outfall using remote video II. 1991 data. Special Rep. 04.08:92, Water Resources ResearchCenter, University of Hawaii at Manoa,Honolulu, Hawaii. 14 pp. Brock, R.E. 1993a.An analysisof the fish communitiesalong the Sand Island deep ocean outfall using remote video III. 1992 data. Special Rep. 01.15:93, Water Resources ResearchCenter, University of Hawaii at Manoa,Honolulu, Hawaii. 15pp.

Brock, R.E. 1993b. An analysis of the fish and macrobenthosalong the Sand Island deep ocean outfall, 0'ahu, Hawai'i, using remote video IV 1993. Proj. Rep. PR-94-12, Water Resources Research Center, University of Hawaii at Manoa, Honolulu, Hawaii. 17 pp. Brock, R.E. 1995. An analysis of the fish and macrobenthosalong the Sand Island Ocean Outfall using remote video: V. 1994 data. Proj. Rep. PR-95-06, Water Resources ResearchCenter, University of Hawai'i at Mhnoa,Honolulu, Hawai'i, 19 pp.

Brock, R.E., C. Lewis, and R.C. Wass. 1979.Stability and structureof a fish community on a coralpatch reef in Hawaii. Mar. BioL 54:281-292. Brock, R.E., and J.E. Norris. 1989.An analysisof the efficacy of four artificial reef designs in tropical ~aters. Bull. Mar. Sci. 44:934-941. Brock,V.E. 1954.A preliminaryreport on a methodof estimatingreef fish populations.J. WildL Mgmt. 18:297-308. Eckert, G.J. 1985.Settlement of coral reef fishesto different naturalsubstrata and at different depths.In Proceedingsof the5th InternationalCoral Reef Congress, vol. 5, Tahiti,385 390.

19 Evans, E.C., ed. 1974. Peart Harbor biological survey final report. Report No. NUC-TN- 1128,Naval UnderseaCenter, Hawaii Laboratory.

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