REPORT DOCUMENTATION FORM WATER RESOURCES RESEARCH CENTER University of Hawai‘i at Maønoa

1 SERIES 2 COWRR NUMBER Project Report PR-2005-05 FIELD-GROUP 05-C 3 TITLE 4 REPORT DATE January 2005 A survey of selected coral and fish assemblages near 5 NO. OF the Waianae Ocean Outfall, Oahu, Hawaii, 2004 PAGES viii + 20 6 NO. OF 7 NO. OF TABLES 4 FIGURES 10 8 AUTHOR 9 GRANT AGENCY

Anthony R. Russo City and County of Honolulu Richard E. Brock Department of Environmental Services

10 CONTRACT NUMBER C00983 11 DESCRIPTORS: wastewater outfall, fish, corals, monitoring, data collections, surveys

IDENTIFIERS: coral reef fish communities, Pocillopora meandrina, Porites lobata, BrayÐCurtis similarity index, Cochran’s Q-test, Waianae Ocean Outfall, Oahu, Hawaii

12 ABSTRACT (PURPOSE, METHOD, RESULTS, CONCLUSIONS) In 2004, coral growth and fish abundance were monitored at stations located at and in the vicinity of the Waianae Ocean Outfall. Fish abundance at diffuser station W-3 was 135 individuals representing 23 species. Station W-2, which was a control station in the past, was replaced by Station Z in 2003. This new station (Z), which is located inside the area of fish haven obstructions (artificial reef) controlled by the Hawaii Department of Land and Natural Resources (DLNR), is approximately 1.0 km southeast of the diffuser at a depth of 16 m. Station W-2 was replaced because of the dangerous deterioration of the sunken ship Mahi at this station. A total of 307 individuals were seen at Station Z, along both transects combined, with 24 species (195 individuals) at Transect 1 and 17 species (112 individuals) at Transect 2. This was an increase from 2003 values. At Station WW, an inshore station located 0.8 km from shore, fish abundance was high, with a total of 1,231 individuals representing 38 species on both transects combined. On the pipeline armor rocks at Station WW, fish aggregated in large numbers, probably due to the artificial relief provided by the rocks. There were large numbers of Lutjanus kasmira (taape) and Abudefduf abdominalis, which are intense competitors for food resources. At this station very large numbers of the damselfish Chromis ovalis were also seen; they accounted for 37% of the total abundance and the large increase in abundance seen in 2004 vs. 2003. The fish species seen inshore are comparable to those seen in similar (boulder) natural biotopes around Hawaii. Permanent coral quadrats were set up at Station Z and photographed for coral cover. Coral cover at five selected quadrats ranged from 8% to 58%. At the diffuser, corals were seen growing on the diffuser pipe and on the riser discharge ports. In 1986, when the diffuser began operation at a discharge rate of 1.5 mgd (0.07 m3/s), no corals were seen at this location. At inshore station WW, corals were sparsely distributed off the pipeline but were numerous and thriving on the armor rock over the pipeline. In 2003, the inshore transect (Alpha), off the armor rock, was covered (approximately 20%) with the alga Dictyopteris plagiogramma. In 2004, no algal cover was seen. The water was clear at all stations surveyed (12 to 15 m horizontal visibility), and the surrounding sediments were clean and white. The high abundance and diversity of fish indicate that no serious effects are caused by the outfall operation and discharge on the biological community at the stations surveyed. There continues to be no evidence that the Waianae outfall is adversely affecting the abundance or diversity of fishes and corals at the selected survey stations in the vicinity of the effluent discharge.

2540 Dole Street • Honolulu, Hawai‘i 96822 • U.S.A. • (808) 956-7847 AUTHORS: Dr. Anthony R. Russo Professor, Oceanography (retired) Mathematics and Natural Sciences Division Leeward Community College 96-045 Ala Ike Street Pearl City, Hawai‘i 96782 Tel.: 808/524-4063 e-mail: [email protected]

Dr. Richard E. Brock Associate Researcher and Fisheries Specialist Sea Grant Extension Service Hawaii Institute of Geophysics 213 University of Hawai‘i at Møanoa Honolulu, Hawai‘i 96822 Tel.: 808/956-2859 FAX: 808/956-2858 Email: [email protected]

$5.00/copy

Please make remittance in U.S. dollars from a U.S. bank or international money order to: RCUH 1002

Mail to: Water Resources Research Center University of Hawai‘i at Maønoa 2540 Dole St., Holmes Hall 283 Honolulu, Hawai‘i 96822 ¥ U.S.A. Attn: Publications Office

NOTE: Please indicate PR-2005-05 on check or money order for our reference. A SURVEY OF SELECTED CORAL AND FISH ASSEMBLAGES NEAR THE WAIANAE OCEAN OUTFALL, O‘AHU, HAWAI‘I, 2004

Anthony R. Russo and Richard E. Brock

Project Report PR-2005-05

January 2005

PREPARED FOR Department of Environmental Services City and County of Honolulu Project Report for “A Five-Year Biological and Sediment Monitoring Program on Specific Marine Communities Near the City’s Ocean Sewer Outfalls: 2002–2006” Project No.: C00983 Project Period: 23 July 2002Ð30 September 2007 Principal Investigator: James E.T. Moncur

WATER RESOURCES RESEARCH CENTER University of Hawai‘i at Møanoa Honolulu, Hawai‘i 96822 Any opinions, findings, and conclusions or recommendations expressed in this publication are those of the authors and do not necessarily reflect the view of the Water Resources Research Center. ABSTRACT

In 2004, coral growth and fish abundance were monitored at stations located at and in the vicinity of the Waianae Ocean Outfall. Fish abundance at diffuser station W-3 was 135 individuals representing 23 species. Station W-2, which was a control station in the past, was replaced by Station Z in 2003. This new station (Z), which is located inside the area of fish haven obstructions (artificial reef) controlled by the Hawai‘i Department of Land and Natural Resources (DLNR), is approximately 1.0 km southeast of the diffuser at a depth of 16 m. Station W-2 was replaced because of the dangerous deterioration of the sunken ship Mahi at this station. A total of 307 individuals were seen at Station Z, along both transects combined, with 24 species (195 individuals) at Transect 1 and 17 species (112 individuals) at Transect 2. This was an increase from 2003 values. At Station WW, an inshore station located 0.8 km from shore, fish abundance was high, with a total of 1,231 individuals representing 38 species on both transects combined. On the pipeline armor rocks at Station WW, fish aggregated in large numbers, probably due to the artificial relief provided by the rocks. There were large numbers of Lutjanus kasmira (ta‘ape) and Abudefduf abdominalis, which are intense competitors for food resources. At this station very large numbers of the damselfish Chromis ovalis were also seen; they accounted for 37% of the total abundance and the large increase in abundance seen in 2004 vs. 2003. The fish species seen inshore are comparable to those seen in similar (boulder) natural biotopes around Hawai‘i. Permanent coral quadrats were set up at Station Z and photographed for coral cover. Coral cover at five selected quadrats ranged from 8% to 58%. At the diffuser, corals were seen growing on the diffuser pipe and on the riser discharge ports. In 1986, when the diffuser began operation at a discharge rate of 1.5 mgd (0.07 m3/s), no corals were seen at this location. At inshore station WW, corals were sparsely distributed off the pipeline but were numerous and thriving on the armor rock over the pipeline. In 2003, the inshore transect (Alpha), off the armor rock, was covered (approximately 20%) with the alga Dictyopteris plagiogramma. In 2004, no algal cover was seen. The water was clear at all stations surveyed (12 to 15 m horizontal visibility), and the surrounding sediments were clean and white. The high abundance and diversity of fish indicate that no serious effects are caused by the outfall operation and discharge on the biological community at the stations surveyed. There continues to be no evidence that the Wai‘anae outfall is adversely affecting the abundance or diversity of fishes and corals at the selected survey stations in the vicinity of the effluent discharge.

v

CONTENTS

INTRODUCTION...... 1

MATERIALS AND METHODS ...... 1

RESULTS...... 7 Station Z...... 7 Station W-3...... 7 Station WW ...... 13

DISCUSSION ...... 16

REFERENCES CITED ...... 19

Figures

1. Biological survey stations in the vicinity of the improved Waianae Ocean Outfall, O‘ahu, Hawai‘i ...... 2 2. Transects at Station Z, Waianae Ocean Outfall, O‘ahu, Hawai‘i...... 3 3. Transect at Station W-3, on the diffuser, Waianae Ocean Outfall, O‘ahu, Hawai‘i ...... 5 4. Transects at Station WW, Waianae Ocean Outfall, O‘ahu, Hawai‘i ...... 6 5. Coral growth in quadrat ABB3 at Station Z, Waianae Ocean Outfall, O‘ahu, Hawai‘i, 2004...... 9 6. Coral growth in quadrat ABA3 at Station Z, Waianae Ocean Outfall, O‘ahu, Hawai‘i, 2004...... 9 7. Fish abundance at Station W-3 for 1999 through 2004, Waianae Ocean Outfall, O‘ahu, Hawai‘i ...... 11 8. Fish species richness at Station W-3 for 1999 through 2004, Waianae Ocean Outfall, O‘ahu, Hawai‘i ...... 11 9. Coral and red sponge growth on diffuser port (quadrat BB2) at Station W-3, Waianae Ocean Outfall, O‘ahu, Hawai‘i, 2004 ...... 12 10. Coral, coralline algae, and bryzoa growth on diffuser port (quadrat BAA1) at Station W-3, Waianae Ocean Outfall, O‘ahu, Hawai‘i, 2004...... 12

Tables

1. Fish abundance at Station Z for 2004, Waianae Ocean Outfall, O‘ahu, Hawai‘i ...... 8 2. Coral cover within five selected quadrats at Station Z, for 2003 and 2004, Waianae Ocean Outfall, O‘ahu, Hawai‘i ...... 10

vii 3. Fish abundance at Station W-3 for 2004, Waianae Ocean Outfall, O‘ahu, Hawai‘i ...... 10 4. Fish abundance at Station WW for 2004, Waianae Ocean Outfall, O‘ahu, Hawai‘i ...... 14

viii INTRODUCTION

The City and County of Honolulu’s conservation district use permit for installation of a wastewater outfall pipe at Wai‘anae, O‘ahu, Hawai‘i, was approved subject to several conditions (Board of Land and Natural Resources letter to the City, 11/15/83; ref. no. CPO-844, file no. OA-4/11/83-1541). Among the conditions was the requirement that, in the vicinity of the outfall diffuser, fishery stocks be assessed annually after the first year of discharge and benthic organisms be monitored photographically annually. The Waianae Wastewater Treatment Plant (WWTP) is a secondary treatment system which discharges 3.22 million gallons per day (0.14 m3/s) of mainly domestic wastewater through an outfall 6,000 feet (1.8 km) offshore at a diffuser depth of approximately 110 feet (33 m). The diffuser is 531 feet (161.8 m) long and discharges at approximately 1.5 feet (0.5 m) above the seafloor through vertical risers. In the fall of 2004, researchers from the University of Hawai‘i and oceanographic personnel from the City and County of Honolulu Department of Environmental Services collaborated in a scuba survey of the marine community near the Waianae Ocean Outfall. This reports summarizes the results of that survey and comparatively analyzes the 2004 data with data collected in previous years.

MATERIALS AND METHODS

Specific locations of the three sampling stations are provided in Figure 1. General information about the stations and their locations is given below. Station Z is located in the fish haven set up by the Hawai‘i Department of Land and Natural Resources (DLNR), 1.0 km southeast of the diffuser, at a depth of approximately 16 m. The substratum is flat limestone and rubble, with coral growth. Two transect lines (25 m long each), spaced 27 m apart, perpendicular to shore, were permanently placed near concrete slabs, which make up part of the fish haven habitat, and near a ledge which drops off to the 23-m depth (Figure 2). Station Z was set up in 2003, 300 m east of the old Station W-2, which was on the sunken ship Mahi. Because of dangerous shifting and corrosion of the ship, it was deemed unsafe to continue diving on the wreck for permanent coral transect and fish counts. DLNR gave the City and County of Honolulu permission to set up Station Z to replace Station W-2 3 N WAIANAE WASTEWATER TREATMENT PLANT

Original WW Outfall 3

10

Outfall Extension

20 W-3 Diffuser

Fish Haven Obstructions

Z

5 3

0 1,000 2,000 3,000 ft

0 0.5 1.0 km 20 Contour in fathoms

10 Survey Station

Adapted from Russo and Lau (1986)

FIGURE 1. Biological survey stations in the vicinity of the improved Waianae Ocean Outfall, O‘ahu, Hawai‘i

2 Two Transects OFFSHORE

90 ft (27.42 m) ABC2 ABC1

EWA

ABA4 ABB4

Ka‘ena Pt.

ABA3 ABB3

Ledge

ABA2 ABB2

75 ft ABA1 ABB1 (22.86 m)

54 ft (16.46 m) depth

INSHORE

Z Plates (concrete slab) Waianae Coral Transect “Z” (close to Z plate) N 21°25'16.6" W 158°11'31.8" Artificial Reef

FIGURE 2. Transects at Station Z, Waianae Ocean Outfall, O‘ahu, Hawai‘i

3 Station W-3 is located at the middle of the diffuser at a depth of approximately 30 m. The 42-inch (1.07-m) diameter diffuser pipe is buried in the sediment and covered with tremie concrete. Discharge is through risers projecting vertically from the pipe. Surrounding sediments consist of coarse carbonate sands. A fish and coral transect was set up on the diffuser (Figure 3). Station WW is located 1 km offshore on the effluent pipeline at a depth of approximately 8 m. Two transects—one approximately 20 m north of the pipeline (Transect Alpha) and the other on the pipeline (Transect Beta)—were set up at this station (Figure 4). The outfall pipe is covered with tremie concrete and surrounded by large armor rock boulders. Transect Alpha lies on flat limestone substratum and Transect Beta on the armor rock covering the pipeline. Both transects are approximately 25 m long and run perpendicular to shore. With authorization from DLNR, Station WW became a permanent station in 1994; it was established to monitor, temporally, any inshore movement of effluent discharged from the outfall. Transect Alpha was monitored in 1990 and 1991, although its monitoring was not then a requirement of DLNR. It was not monitored in 1992 or 1993 because it was destroyed by Hurricane Iniki in September 1992. A new Transect Alpha was established in 1994. In late April 1995, the CCH Oceanographic Team found the 2-inch (5.08-cm) diameter transect wire at Transect Alpha to be damaged and large sections moved or altogether gone from the area. It is not certain whether this was due to natural causes (wave action) or other causes (vandalism, anchor dragging). The transect wire was replaced on 8 and 9 May 1995 by the CCH team. There is no spatial control station in this study; the stations selected are all located at different depths and differ in bottom type and relief. At the chosen stations, relief is provided by artificial structures (i.e., the diffuser, concrete slabs, and armor rock). Because of the uniqueness of each station, comparisons cannot be made among stations spatially for coral and fish abundance and species richness. Only year-to-year comparisons of survey data obtained at the same station can be made. Artificial reefs (concrete slabs) in the vicinity of Station Z attract fishes and provide substrata for coral growth. Artificial structures (boulders and diffuser ports) at Stations WW and W-3 provide habitats for fish as well as surfaces and relief for coral settlement, colonization, and growth. At Station WW (depth of 8 m) armor rock covering the pipeline provides relief in areas where normally flat limestone with 1% to 2% coral cover exists. At all stations fish counts were made along the permanent 25-m transects (Figures 2, 3, and 4) by divers equipped with scuba (Brock 1982). Fishes were counted along the transect as the diver swam upline looking 3 m to the right and then downline looking 3 m to the right.

4 STATION W-3 to End of Pipe

BBB4

BBB3 BBB1 Profile

BBB2 12 ft

BBA4

BBA1 Profile BBA3

BBA2 Waianae 12 ft Ocean Outfall

Diffuser Section SHORE BAC4

BAC3 BAC1 Profile OFFSHORE BAC2 12 ft

BAB4

BAB1 Profile BAB3

BAB2 12 ft

BAA4

BAA3 BAA1 Profile Diffuser BAA2 Nozzle

Typical quadrat

to Waianae Wastewater Treatment Plant

FIGURE 3. Transect at Station W-3, on the diffuser, Waianae Ocean Outfall, O‘ahu, Hawai‘i

5 STATION WW

SHORE

EBA1 EEA1 19.7 m 20 m 24 ft (7.3 m) Deep 24 ft (7.3 m) Deep

Wire Rope

EAA4 ECA4 13.9 m 15 m

Waianae Ocean Outfall Armor Rock EAA3 ECA3 9.8 m 10 m

Cement Bag

EAA2 ECA2 4.6 m 5 m

EAA1 ECA1 0 m 0 m 25 ft (7.6 m) Deep 25 ft (7.6 m) Deep

56 m ALPHA (Offshore Makaha)- BETA (Offshore Ma‘ili)-

FIGURE 4. Transects at Station WW, Waianae Ocean Outfall, O‘ahu, Hawai‘i

6 In the future, comparisons of fish abundance, diversity, and species composition will be made between years for each station using similarity indices. Since errors can occur because of differences in technique and capability among observers, the same diverÐobserver will perform the fish counts annually. That person, beginning in 2004, is Dr. Richard E. Brock. Estimates of coral cover on selected permanent quadrats at Station Z were made using bottom photography and the subsequent projection of photos on a grid. Coral cover was estimated by total grid cover relative to the total area of the quadrat. For Station Z, percent cover of selected quadrats containing coral was compared between years 2003 and 2004 using a paired t-test (Daniel 1987; Sokal and Rohlf 1995). For the three stations, the presence of all macroinvertebrates seen were recorded.

RESULTS

The figures and tables in this report only report data from 1999 to present; however, in the discussion of results some reference is made to pre-1999 data for comparison. Station Z At Station Z, total fish abundance (both transects combined) was 307 individuals representing 31 species (Table 1). The abundance and species richness increased from 2003 to 2004. The area is generally flat, but there is some relief to attract large numbers of fishes. This area may still be in the process of reaching fish community equilibrium. Coral cover at selected quadrats ranged from 8% to approximately 58% (Table 2; Figures 5 and 6). A large number of sea urchins were seen: 34 at Transect A and 6 at Transect B. Mollusk shells (Arca ventricosa and Spondylus tenebrosus) and annelids (Spirobranchus giganteus corniculatus) were also seen. Station W-3 On the diffuser transect at Station W-3, a total of 135 fishes representing 23 species were counted in 2004 (Table 3), whereas 71 fishes representing 11 species were counted in 2003. There were relatively large numbers of the butterflyfish Chaetodon kleinii and the saddleback wrasse Thalassoma duperrey. In 1986, 24 fishes representing 6 species were seen at this station (Russo 1992). In 1988 and 1991 no fishes were seen on the transect, although they were seen swimming in the area. In 1987 and 1989 this station was not monitored. Fish abundance and species richness for 1999 through 2004 are shown in Figures 7 and 8. As in earlier years, corals of the genus Pocillopora (10 to 17 cm in diameter) were seen growing on the concrete cover of the outfall and on the riser ports (6 to 11 cm in diameter) in 2004 (Figures 9 and 10). In the last few years the number of coral heads (mostly

7 TABLE 1. Fish Abundance (no./transect) at Station Z for 2004, Waianae Ocean Outfall, O‘ahu, Hawai‘i No. of Individuals Taxon Transect 1 Transect 2

FAMILY ACANTHURIDAE Acanthurus nigrofuscus 49 4 Acanthurus nigroris 30 Naso hexacanthus 027 Naso sp. 1 1 Zanclus cornutus 02 Zebrasoma flavescens 10 FAMILY BALISTIDAE Melichthys vidua 11 Sufflamen bursa 41 Sufflamen fraenatus 01 Xanthichthys mento 015 FAMILY CHAETODONTIDAE Chaetodon kleinii 14 32 Chaetodon miliaris 10 Chaetodon multicinctus 22 Chaetodon quadrimaculatus 20 Forcipiger flavissimus 30 FAMILY CIRRHITIDAE Paracirrhites arcatus 12 FAMILY DIODONTIDAE Canthigaster jactator 20 Canthigaster sp. 2 0 FAMILY LABRIDAE Macropharyngodon geoffroy 30 Oxycheilinus bimaculatus 02 Pseudocheilinus octotaenia 10 Pseudocheilinus tetrataenia 20 Thalassoma duperrey 33 FAMILY MONOCANTHIDAE Cantherhines dumerilii 01 FAMILY MULLIDAE Parupeneus multifasciatus 14 0 FAMILY POMACANTHIDAE Holacanthus arcuatus 01 FAMILY POMACENTRIDAE Chromis vanderbilti 59 0 Dascyllus albisella 19 16 Plectroglyphidodon johnstonianus 31 FAMILY MURAENIDAE Gymnothorax sp. 1 0 FAMILY SCARIDAE Scarus psittacus 40

Total No. of Individuals 195 112 Total No. of Species 24 17

8 FIGURE 5. Coral growth in quadrat ABB3 at Station Z, Waianae Ocean Outfall, O‘ahu, Hawai‘i, 2004

FIGURE 6. Coral growth in quadrat ABA3 at Station Z, Waianae Ocean Outfall, O‘ahu, Hawai‘i, 2004

9 TABLE 2. Coral Cover Within Five Selected Quadrats at Station Z for 2003 and 2004, Waianae Ocean Outfall, O‘ahu, Hawai‘i Coral Cover (%) Quadrat 2003 2004

AAB1 60.8 57.6 ABA1 24.0 25.2 ABA3 25.4 26.0 ABB3 48.1 49.5 ABC2 8.2 7.8

TABLE 3. Fish Abundance at Station W-3 for 2004, Waianae Ocean Outfall, O‘ahu, Hawai‘i Taxon No. of Individuals

FAMILY ACANTHURIDAE Acanthurus dussumieri 2 Acanthurus nigroris 2 Acanthurus olivaceus 43 Ctenochaetus strigosus 3 Naso brevirostris 4 Naso hexacanthus 3 Naso lituratus 2 FAMILY AULOSTOMIDAE Aulostomus chinensis 1 FAMILY BALISTIDAE Sufflamen bursa 1 Xanthichthys mento 6 FAMILY CHAETODONTIDAE Chaetodon kleinii 23 Chaetodon miliaris 4 Forcipiger flavissimus 3 FAMILY CIRRHITIDAE Paracirrhites arcatus 3 FAMILY DIODONTIDAE Canthigaster jactator 4 FAMILY LABRIDAE Pseudocheilinus octotaenia 1 Pseudojuloides cerasinus 2 Stethojulis balteata 2 Thalassoma duperrey 4 FAMILY MONACANTHIDAE Cantherhines dumerilii 1 FAMILY MULLIDAE Parupeneus multifasciatus 3 FAMILY POMACENTRIDAE Chromis agilis 6 Chromis vanderbilti 12

Total No. of Individuals 135 Total No. of Species 23

10 160

120

80 FISH ABUNDANCE

40

0 1999 20002001 2002 2003 2004

FIGURE 7. Fish abundance at Station W-3 for 1999 through 2004, Waianae Ocean Outfall, O‘ahu, Hawai‘i

25

20

15

10 NO. OF FISH SPECIES

5

0 1999 20002001 2002 2003 2004

FIGURE 8. Fish species richness at Station W-3 for 1999 through 2004, Waianae Ocean Outfall, O‘ahu, Hawai‘i

11 FIGURE 9. Coral and red sponge growth on diffuser port (quadrat BB2) at Station W-3, Waianae Ocean Outfall, O‘ahu, Hawai‘i, 2004

FIGURE 10. Coral, coralline algae, and bryzoa growth on diffuser port (quadrat BAA1) at Station W-3, Waianae Ocean Outfall, O‘ahu, Hawai‘i, 2004

12 P. meandrina) in the diffuser vicinity increased from each previous year, and coral heads grew larger (>20 cm). The most dominant species of corals seen at this station include Pocillopora meandrina, Porites lobata, and Montipora verrucosa. In 1986, the year the outfall was completed and in service below full discharge capacity (1.5 mgd [0.07 m3/s]), no corals were seen growing on the diffuser or in its vicinity. Only after 1991 were corals seen colonizing the diffuser substratum. In 1991 the sewage discharge rate was approximately 2 mgd (0.09 m3/s); it increased to 2.9 mgd (0.13 m3/s) in 1994 and to approximately 3.22 mgd (0.14 m3/s) in 2001. Other macroinvertebrates recorded in 2004 were one cone shell (Conus lividus) and the sea urchins Echinostrphus aciculatum (4 individuals) and Echinometra mathaei (6 individuals). Two sea cucumbers (Holothuria atra) were also recorded. Station WW The location of Transect Alpha is the same as that of the transect set up in 1990 to monitor inshore movement of effluent. Station WW was monitored for scientific interest and was not authorized by DLNR as a permanent sampling station until 1994. The station was not monitored in 1992 or 1993 because of the effects of Hurricane Iniki, which changed the substratum characteristics and destroyed the permanent transects emplaced in 1990. New transects were set up at Station WW in 1994. At Station WW, total fish abundance (Transects Alpha and Beta combined) was 1,231 individuals (38 species). At Transect Beta on the armor rocks covering the pipeline, 1,209 individuals representing 33 species were seen, whereas at Transect Alpha, 22 individuals representing 9 species were seen (Table 4). The most abundant species were the bluelined snapper (ta‘ape) Lutjanus kasmira (200 individuals), the ovate damselfish Chromis ovalis (447 individuals), the sergeant major (mamo) Abudefduf abdominalis (124 individuals), and the yellowfin goatfish (weke‘ula) Mulloidichthys vanicolensis (109 individuals). L. kasmira, which normally congregate in large schools, and A. abdominalis were also abundant during the last six years of study. In 1999 there were large numbers of the yellowstripe goatfish (weke) of the genus Mulloidichthys. Over the years, abundance generally increased while fish species diversity moderately fluctuated. There is probably intensive interspecific competition for new niche space, and fish species composition fluctuates slightly as community equilibrium is approached. Rare species are usually not counted as often, relative to the three or four dominants which increased dramatically over the last few years. In recent years the damselfish A. abdominalis and the mempachi (genus Myripristis) have been dominant. Many more fish individuals and species were recorded at Transect Beta (on the pipeline) than at Transect Alpha. Fishes appear to aggregate over artificial substrata, which provide ample hard structure for the colonization of corals. In 1998, the bottom at Transect Alpha was covered (30%) with the alga Dictyopteris plagiogramma, and there was very little relief. In 1999, this

13 TABLE 4. Fish Abundance (no./transect) at Station WW for 2004, Waianae Ocean Outfall, O‘ahu, Hawai‘i No. of Individuals Taxon Transect Alpha Transect Beta

FAMILY ACANTHURIDAE Acanthurus nigrofuscus 018 Acanthurus olivaceus 011 Ctenochaetus strigosus 029 Naso lituratus 04 Naso unicornis 01 Zanclus cornutus 02 Zebrasoma flavescens 04

FAMILY AULOSTOMIDAE Aulostomus chinensis 04

FAMILY BALISTIDAE Melichthys vidua 02 Rhinecanthus rectangulus 20 Sufflamen bursa 11

FAMILY CHAETODONTIDAE Chaetodon miliaris 03

FAMILY CIRRHITIDAE Paracirrhites forsteri 01

FAMILY DIODONTIDAE Canthigaster jactator 10 Canthigaster sp. 1 0

FAMILY HOLOCENTRIDAE Myripristis amaena 0 100 Neoniphon sammara 01 Sargocentron diadema 09

FAMILY LABRIDAE Cheilio inermis 01 Halichoeres ornatissimus 01 Oxycheilinus bimaculatus 10 Thalassoma duperrey 48

FAMILY LETHRINIDAE Monotaxis grandoculis 024

FAMILY LUTJANIDAE Lutjanus kasmira 0 200

FAMILY MONACANTHIDAE Cantherhines dumerilii 22

FAMILY MULLIDAE Mulloidichthys vanicolensis 0 109 Parupeneus bifasciatus 05 Parupeneus pleurostigma 09

14 TABLE 4—Continued No. of Individuals Taxon Transect Alpha Transect Beta

FAMILY POMACANTHIDAE Centropyge potteri 02

FAMILY POMACENTRIDAE Abudefduf abdominalis 0 124 Chromis hanui 09 Chromis ovalis 0 447 Chromis vanderbilti 60 Chromis verater 023 Dascyllus albisella 037 Stegastes fasciolatus 014

FAMILY SCARIDAE Scarus psittacus 41

FAMILY SERRANIDAE Cephalopholis argus 03

Total No. of Individuals 22 1,209 Total No. of Species 9 33

15 alga disappeared. In 2000 and 2001, it reappeared with approximately 30% to 45% bottom cover. In 2002, the algal cover was approximately 10%, followed by an increase to about 20% in 2003. This alga was not reported in 2004. Corals were seen colonizing on the armor rock and a 2-inch (5.08-cm) diameter cable that was discarded or moved close to Transect Alpha during Hurricane Iniki in 1992. More coral heads (mostly Pocillopora meandrina) were seen in this area in 2003 than in 2001 and 2002. Still, the coral bottom cover was below 2.5%. At both Transects Alpha and Beta, large numbers (>100) of sea urchins were seen.

DISCUSSION

Off the Wai‘anae coast, coral cover is normally low (1% to 2% of bottom area) and is dominated by two coral species, Pocillopora meandrina and Porites lobata (Reed et al. 1977). This dominance existed long before the modified Wai‘anae outfall pipeline began discharging wastewater in January 1986. The old outfall pipe, which discharged effluent into water less than 20 m deep, was modified and extended to discharge into the 33-m isobath approximately 1.8 km offshore. At Station Z, in the artificial reef zone, moderate numbers of fish individuals (307) and species (31) were counted on both transects combined. Unlike the old station (W-2), there is little topographical relief on the bottom; therefore, not as many fishes are attracted to this site as they were to the sunken ship Mahi. This station (Z) will be monitored closely and compared from year to year for fidelity of species composition, abundance of fishes, and coral cover. At Station W-3, fishes were fairly abundant and corals were seen colonizing the areas near the diffuser and on the diffuser riser ports themselves. The surrounding sediments were clean and white. From 1986 through 1988, corals were not seen at this station. After 1993 coral heads (approximately 10 to 25 cm in diameter) of Pocillopora meandrina and Porites lobata became established (Russo 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2001, 2002, 2003). At Station W-3, fish abundance decreased from 1999 to 2003 and increased in 2004 (Figure 7). Fish species richness decreased from 1999 to 2001 and increase from 2001 to 2004 (Figure 8). Variations in fish abundance and diversity may be affected by food resources, especially particulates in the water column. If effluent loads are not excessive, some particulate matter may be utilized by water-column-feeding fishes (Hobson 1984; Pastorak and Bilyard 1985). The particulate load is decreased under secondary wastewater treatment, which began in 1996. Fish abundance and diversity increased quickly after that year. Secondary treated effluents (nitrate rich) can be utilized by phytoplankton more rapidly than primary treated

16 sewage (ammonia rich). The increase in planktivorous fishes since secondary treatment began seems to support this idea. At Station WW, many fishes were counted over the pipeline and armor rock (Transect Beta), whereas fewer were seen over the flat, algal-dominated limestone bottom (Transect Alpha). Over the survey years from 1999 through 2004, fish abundance and species richness increased at Transect Beta. In 2002 and 2003, numbers were relatively high (479 and 471 individuals, respectively). In 2004, the abundance increased dramatically to 1,209 individuals due to the large number (447 individuals) of Chromis vanderbilti encountered. That bottom relief is important in structuring fish communities is evidenced by the much greater abundance and diversity of fishes seen at Transect Beta, which has an appreciable structure of armor rock. Fishes at Transect Alpha may be attracted to the armor rock at Transect Beta, as evidenced by the large number of fishes seen on the latter transect. Large numbers of the mempachi (genus Myripristis), the black damselfish (‘øalo‘ilo‘i) Dascyllus albisella, the goatfish (weke ‘aø) (genus Mulloidichthys), and other common fish species were seen swimming over the rocks at Transect Beta. The bluelined snapper (ta‘ape) Lutjanus kasmira and the sergeant major (mamo) Abudefduf abdominalis were very abundant at Transect Beta in 2002, 2003, and 2004. Lutjanus kasmira was introduced to Hawai‘i from the Marquesas Islands in 1958 (Randall 1987). Since then it has dramatically increased in abundance and has spread throughout the entire Hawaiian archipelago. Local fishers suspect that L. kasmira may eat the juveniles of locally important fish species since 40% of its diet is fish (Tabata 1981). However, there is little conclusive evidence to support this. Oda and Parrish (1981) found some evidence of holocentrid fish (genus Myripristis [mempachi]) remains in the guts of L. kasmira but not in sufficient quantity to justify its classification as a major fish predator of locally important fishes. L. kasmira is an active, generalized carnivore that feeds mainly on crabs and juvenile fishes (Oda and Parrish 1981). However, there seems to be no significant overlap in diet to warrant a conclusion of intense competition for food with locally important fish species such as Parupeneus porphyreus (kuømuø) or Mulloidichthys flavolineatus (weke ‘aø). The ecological niche of L. kasmira is still not completely understood, and more information is needed to conclusively determine why it has increased greatly in abundance since 1958 while, coincidentally, other fish species important to local fishers have declined. One other important factor, the possibility of overfishing, must still be addressed before cause-and-effect relationships can be made about the impact of L. kasmira on Hawai‘i fish community dynamics (Grigg 1994). The armor rock surrounding the outfall pipe provides ample habitat space for hiding and mating, ample surface for the colonization of food sources, and a reference point above the

17 substratum for aggregation and maintenance of schools. Artificial structures placed in an area normally devoid of bottom relief can attract large numbers of fish and provide surfaces for coral and other sessile organism attachment. In 1975, total fish abundance at a transect located approximately 1 km offshore from the Waianae WWTP near the pipeline was 18 individuals representing 6 species (number adjusted to a 30 m × 6 m transect area) (Reed et al. 1977). At Transect Alpha of Station WW, which is close (less than 50 m) to the above-mentioned transect, five individual fishes representing two species were recorded in 2000. Aggregations of fish species comparable to those found in similar biotopes around the Hawaiian islands were seen over the armor rock (Transect Beta) at Station WW during the 1999 through 2004 surveys. For example, Hobson’s (1984) record of aggregations over “boulder” regions includes schools of the yellowstripe goatfish (weke ‘aø) Mulloidichthys flavolineatus, the surgeonfish (na‘ena‘e) Acanthurus olivaceus, several species of mempachi (‘u¯‘uø) (Myripristis sp.), and the saddleback wrasse (hõønøalea lauwili) Thalassoma duperrey. These same species, and many others identified with the boulder biotope, were seen over the armor rock at Station WW in 2004. In 2004 there was no observable indication that the Wai‘anae sewer outfall effluent was adversely affecting the fish, coral, or macroinvertebrates at selected stations in the vicinity of the discharge. Since studies before 1986 were not conducted at the same deeper stations but in an area closer to shore (depth of 8 m), a before-and-after-discharge comparison of the studied stations cannot be made. However, generally, the dominant fishes and coral species seen from 1986 through 2004 were essentially the same as those seen in earlier discharge years and before the outfall was modified (Reed et al. 1977). Sediments at all stations were clean, and horizontal visibility was good. At Station W-3, corals were growing on the diffuser ports and seemed to be thriving where none were seen prior to 1991. Fishes associated with corals became more abundant after 1991. At Station WW (the inshore station), fish populations were abundant and diverse, as well as representative of similar biotopes (Hobson 1984) found in Hawai‘i. Coral coverage was generally low on natural substrata—a condition typical of shallow, flat, low-relief bottoms in this area (Reed et al. 1977). However, corals were thriving on the armor rock at the inshore pipeline, probably because of artificial topographical relief. Fishes are frequently used as bio-indicators since they are relatively easy to identify and are of particular interest to local agencies because of recreational and commercial fishing. Monitoring fish populations is recommended over the long term and, if it is determined that biological impacts do occur, there may be a strong argument for adaptive management strategies where particular factors such as effluent flow rate, treatment, and periodicity of discharge can be changed or monitored to improve environmental health (Smith et al. 1999).

18 This continuing study showed that, since the beginning of biomonitoring in 1986, no significant deleterious effects have occurred to the fish and coral communities at the stations surveyed.

REFERENCES CITED

Brock, R.E. 1982. A critique of visual census methods for assessing coral reef populations. Bull. Mar. Sci. 32:24Ð35. Daniel, W.W. 1987. Biostatistics: A foundation for analysis in the health sciences. New York: Wiley and Sons. Grigg, R.W. 1994. Effects of sewage discharge, fishing pressure and habitat complexity on coral reef ecosystems and reef fishes in Hawaii. Mar. Ecol. Prog. Ser. 103:25Ð34. Hobson, E.S. 1984. The structure of reef fish communities in the Hawaiian archipelago. In Proc. N.W. Hawaiian Island Symp., MR-84-01, University of Hawaii Sea Grant College Program, Honolulu, pp. 57Ð70. Oda, D.K., and J.D. Parrish. 1981. Ecology of commercial snappers and groupers introduced to Hawaiian waters. Proc. 4th Int. Coral Reef Symp., vol. I, Manila, Philippines. Pastorak, R.A. and G.R. Bilyard. 1985. Effects of sewage pollution on coral reef communities. Mar. Ecol. Prog. Ser. 21:175Ð189. Randall, J. 1987. Introductions of marine fishes to the Hawaiian islands. Bull. Mar. Sci. 4(2):490Ð502. Reed, S.A., E.A. Kay, and A.R. Russo. 1977. Survey of benthic coral reef ecosystems, fish populations, and micromollusks in the vicinity of the Waianae sewage ocean outfall, O‘ahu, Hawai‘i—summer 1975. Tech. Rep. 104, Water Resources Research Center, University of Hawaii at Manoa, Honolulu. 36 pp. Russo, A.R. 1992. A survey of selected coral and fish assemblages near the Waianae Ocean Outfall, 1992. Spec. Rep. 10.19:92, Water Resources Research Center, University of Hawaii, Manoa, Honolulu. 8 pp. Russo, A.R. 1993. A survey of selected coral and fish assemblages near the Waianae Ocean Outfall, O‘ahu, Hawai‘i, 1993. Proj. Rep. PR-94-10, Water Resources Research Center, University of Hawai‘i, M¯anoa, Honolulu. 14 pp. Russo, A.R. 1994. A survey of selected coral and fish assemblages near the Waianae Ocean Outfall, O‘ahu, Hawai‘i, 1994. Proj. Rep. PR-95-04, Water Resources Research Center, University of Hawai‘i, M¯anoa, Honolulu. 23 pp. Russo, A.R. 1995. A survey of selected coral and fish assemblages near the Waianae Ocean Outfall, O‘ahu, Hawai‘i, 1995. Proj. Rep. PR-96-01, Water Resources Research Center, University of Hawai‘i, M¯anoa, Honolulu. 25 pp.

19 Russo, A.R. 1996. A survey of selected coral and fish assemblages near the Waianae Ocean Outfall, O‘ahu, Hawai‘i, 1996. Proj. Rep. PR-97-03, Water Resources Research Center, University of Hawai‘i at M¯anoa, Honolulu. 26 pp. Russo, A.R. 1997. A survey of selected coral and fish assemblages near the Waianae Ocean Outfall, Oahu, Hawaii, 1997. Proj. Rep. PR-98-03, Water Resources Research Center, University of Hawai‘i at M¯anoa, Honolulu. 26 pp. Russo, A.R. 1998. A survey of selected coral and fish assemblages near the Waianae Ocean Outfall, Oahu, Hawaii, 1998. Proj. Rep. PR-99-04, Water Resources Research Center, University of Hawai‘i at M¯anoa, Honolulu. 26 pp. Russo, A.R. 1999. A survey of selected coral and fish assemblages near the Waianae Ocean Outfall, Oahu, Hawaii, 1999. Proj. Rep. PR-2000-02, Water Resources Research Center, University of Hawai‘i at M¯anoa, Honolulu. 27 pp. Russo, A.R. 2001. A survey of selected coral and fish assemblages near the Waianae Ocean Outfall, Oahu, Hawaii, 2000. Proj. Rep. PR-2001-06, Water Resources Research Center, University of Hawai‘i at M¯anoa, Honolulu. 27 pp. Russo, A.R. 2002. A survey of selected coral and fish assemblages near the Waianae Ocean Outfall, Oahu, Hawaii, 2001. Proj. Rep. PR-2002-08, Water Resources Research Center, University of Hawai‘i at M¯anoa, Honolulu. 27 pp. Russo, A.R. 2003. A survey of selected coral and fish assemblages near the Waianae Ocean Outfall, Oahu, Hawaii, 2002. Proj. Rep. PR-2003-06, Water Resources Research Center, University of Hawai‘i at M¯anoa, Honolulu. 28 pp. Russo, A.R. 2003. A survey of selected coral and fish assemblages near the Waianae Ocean Outfall, Oahu, Hawaii, 2003. Proj. Rep. PR-2004-05, Water Resources Research Center, University of Hawai‘i at M¯anoa, Honolulu. 23 pp. Russo, A., and L.S. Lau. 1986. Benthic and fish survey in the vicinity of the Waianae sewer outfall. Unpubl. rep. to City and County of Honolulu. Water Resources Research Center, University of Hawaii at Manoa, Honolulu. Smith, A.K., P.A. Ajani, and D.E. Roberts. 1999. Spatial and temporal variation in fish assemblages exposed to sewage and implications for management. Mar. Environ. Res. 47:241-260. Sokal, R.R., and F.J. Rohlf. 1995. Biometry: The principles and practice of statistics in biological research. 3d edition. San Francisco: W.H. Freeman & Co. 887 pp. Tabata, R. 1981. Ta‘ape: What needs to be done? Workshop Proc. Paper 46, University of Hawaii Sea Grant College Program, Honolulu. 31 pp.

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