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REPORT DOCUMENTATION FORM WATER RESOURCES RESEARCH CENTER University of Hawai‘i at Ma¯noa 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, Bray–Curtis 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 M¯anoa 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 Ma¯noa 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 2002–30 September 2007 Principal Investigator: James E.T. Moncur WATER RESOURCES RESEARCH CENTER University of Hawai‘i at M¯anoa 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