The Friends of Hanauma Bay (FOHB) was very pleased to award a travel grant of $1,300 to Ms. Ling Ong in support of research she is conducting on the parrotfish that populate Hanauma Bay. Ms. Ong, a doctoral student at the University of Hawaii, submitted a proposal for a research travel grant to the FOHB. The grant request involved travel to the Azores where similar research on parrot fish was being conducted. The FOHB was pleased to be able to support Ms. Ong's research and when resources are available will consider other grant requests for Hanauma Bay related marine research.
The study of parrotfish in Hanauma Bay
Ling Ong
The following research topics are part of my dissertation as a graduate student at the Zoology Department, University of Hawaii. I can be reached at ongl@hawaii.edu, if you have any questions about the research.
Click Image for Enlarged Photo
Chlorurus perspicillatus
(Spectacled parrotfish)
Photography ©, courtesy of Dave R. Schrichte, schrichtd001@hawaii.rr.com
Some basic questions answered:
What are parrotfish?
Parrotfish belong to the family Scaridae and are aptly named so because of their beak-like teeth and often have bright colors. They are most closely related to wrasses. All parrotfish have a pharyngeal mill, which are modified bones at the back of their throats which grind and crush any rock or coral that they ingest into sand. They have no stomachs but have a long intestine. Most parrotfish like wrasses undergo sex change, where they may switch from female to male sometime in their adult life.
Why study parrotfish?
Parrotfish have been studied intermittently from the early 60's to the present. Most studies suggest that they are major biological contributors to sand production on the reef. Other studies also suggest that they eat a significant amount of live coral and thus have an impact on coral growth. None of these issues have been addressed in Hawaii as yet.
Why Hanauma Bay?
Of the seven parrotfish species found in Hawaii, Oahu has 5 species, namely the
Stareye parrotfish Calotomus carolinus
Spectacled parrotfish Chlorurus perspicillatus - Endemic to Hawaii
Bullethead parrotfish Chlorurus sordidus
Palenose parrotfish Scarus psittacus
Redlip parrotfish Scarus rubroviolaceus.
My species of study are the Redlip and Spectacled parrotfish, which grow up to a length of 60 cm (two feet) or a little more.
Hanauma Bay is one of the few areas in Oahu where all five species are readily seen. Also, being a protected reserve since 1967, the fish are habituated to human presence. This makes behavioural observations easy and less likely to influence their normal behavior. Hanauma Bay is also one of the few places on the island where parrotfish close to their maximum size are abundant.
Parrotfish: their ecological role as bioeroders and sand producers on our reefs
Sand production estimates have varied widely from species to species. Australian studies show that the Bullethead parrotfish (Chlorurus sordidus - also found in Hawaii) produces only around 20 kg/individual-yr while the Heavybeak parrotfish (Chlorurus gibbus) up to 1000 kg kg/individual-yr! So far my studies have produced estimates somewhere in between the two, around 300 -500 kg/individual-yr. Approximately half of all the sand they produce is deposited in sand patches or gullies in the bay.
These estimates were calculated by using the following formula:
Mass of substrate eroded = mean bite volume of individual X
no. of bites per day X
no. of days per year X
proportion of bites leaving scars X
density of substrate
Spectacled Parrotfish with bites in the background. Click here for an enlarged photo.Also, contrary to popular belief, the Redlip and Spectacled parrotfish do NOT graze on LIVE coral in Hawaii to any significant degree. More than 90% of all observed bites were taken from dead coral covered with turf or crustose algae.
Other related researches involve determining the particle sizes of sand they produce and where the sand ultimately goes to.
Resource management of parrotfish: how large is their home range and how long do they stay in a particular area?
Starting sometime in November 2003, several individual parrotfish will be implanted with ultrasonic tags. Each individual will be followed over a few days to determine their short-term home range (active tracking) while longer term passive monitoring will be conducted to determine if the parrotfish are long-term residents in the bay. Results will help calculate the minimum reserve size needed to conserve healthy stocks of parrotfish as well as determine when the mating season is, if there is indeed any.
Volunteer tracking in the bay on a kayakVolunteering
Volunteers are ALWAYS welcome. Much of my work would not have been possible without the generous time and energy of volunteers. You need to be comfortable snorkelling and be able to swim fairly long distances in the water (I work mainly in the outer bay). Volunteers normally spend an hour to an hour and a half in the water at a time. Send an email to ongl@hawaii.edu to enquire. I work mainly during the day on weekdays and Saturdays.
Useful resources:
JE Randall (1996) Shore Fishes of Hawaii. Natural World Press
JP Hoover (2002) Hanauma Bay - a marine life guide to Hawai'i's most popular nature reserve. Mutual Publishing
Photo credits:
1st parrotfish Photo courtesy of Dave R. Schrichte, schrichtd001@hawaii.rr.com
Bite Mark photo - Tom Delmundo
Volunteer tracking - Ling Ong
