• bullet Aquaculture and Aquaponics July 2019 AA-1 ISBN 978-1-929054-15-2 Sustainable Capture-Based Aquaculture of Rabbitfish in Pacific Island Lagoons Andre P. Seale1 and Simon Ellis2 1Department of Human Nutrition, Food and Animal Sciences, University of Hawai‘i at Mānoa, 2Marine and Environmental Research Institute of Pohnpei, Madolenihmw, Pohnpei, FM96941, Federated States of Micronesia, and University of Hawai‘i at Hilo Pacific Aquaculture and Coastal Resources Center, Hilo, HI 96720 Introduction Pohnpei (MERIP), opening up an As worldwide landings in capture- exciting new farming opportunity based fisheries increase, catch for rural communities in the Pacific volumes and fish sizes are getting region. The purpose of this fact smaller. Both are clear indications sheet is to inform resource man- of overfishing. Climate change agers, educators, and prospective and ocean acidification are also farmers of the possibilities and threatening fisheries. Over-fishing benefits of sustainable rabbitfish is depleting natural resources in cage culture in the U.S.-Affiliated Micronesia and other parts of Pacific Islands and broader Pacific. the Pacific, creating a clear need to develop alternatives for the Figure 1. Capture-based aquaculture can Why Culture Rabbitfish? economy and food security for be a sustainable option for Pacific island Rabbitfishes comprise a family of fishing communities. Sustain- economies. tropical reef fishes of the family able capture-based aquaculture of Siganidae that are abundant in the high-value finfish species (Figure 1) has proven to be Indian and Western Pacific Oceans.In Micronesia, rab- a viable option for many developing nations worldwide bitfish, which are locally known as “kioak,” make up and makes up about 20% of global marine aquaculture 18% of all subsistence fisheries and are one of the most production [1]. Capture-based aquaculture entails the preferred food fish locally [2]. Rabbitfish are herbivores use of “seed” fish, crustaceans, or molluscs that have (plant eaters), feeding mainly on macroalgae of the genus been caught from the wild. Sustainable capture-based Caulerpa and Sargassum. Herbivores require less protein techniques for rabbitfishes have recently been developed in their diet for good growth than many species of ma- at the Marine and Environmental Research Institute of rine fishes. Their plant-based diet means that formulated Published by the College of Tropical Agriculture and Human Resources (CTAHR) and issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in co- operation with the U.S. Department of Agriculture, under the Director/Dean, Cooperative Extension Service/CTAHR, University of Hawai‘i at Mānoa, Honolulu, Hawai‘i 96822. Copyright 2018, University of Hawai‘i. For reproduction and use permission, contact the CTAHR Office of Communication Services, [email protected], 808-956-7036. The university is an equal opportunity/affirmative action institution providing programs and services to the people of Hawai‘i without regard to race, sex, gender identity and expression, age, religion, color, national origin, ancestry, disability, marital status, arrest and court record, sexual orientation, or status as a covered veteran. Find CTAHR publications at www.ctahr.hawaii.edu/freepubs. UH–CTAHR Sustainable Capture-Based Aquaculture of Rabbitfish in Pacific Island Lagoons AA-1 — July 2019 diets for them can have less protein and more plant-based aquarium trade. materials, which improves sustainability and lowers • Rabbitfish will eat low-protein formulated fish feeds costs. Some species of rabbitfish have additional traits used to feed other commercially important finfish. that make them good for aquaculture, namely schooling They can also feed on algae, or a combination of behavior, or grouping together, and mass spawning [3] algae and formulated diets. in large numbers [4,5]. • Rabbitfish grow fast in reef lagoon conditions. The potential for rabbitfish culture will be influenced • Most rabbitfish are non-aggressive and exhibit by species selection and location. Understanding the schooling behavior in cages. natural life history of local rabbitfish species is one of • Rabbitfish are tolerant to changing conditions, such the first steps in developing a successful capture-based as temperature and salinity, in water. aquaculture program in any region of the Pacific. The • Rabbitfish farming can provide an alternative source following list provides additional advantages for grow- of income for rural communities. ing rabbitfish in comparison with other finfish in the • Rabbitfish spawn at the same time, resulting in large Pacific region: quantities of young fish that are naturally available • Rabbitfish are one of the most abundant fish in for collection at low cost. Western Pacific lagoons. • Sustainable capture of juvenile rabbitfish for farm- • There is presently no long-term sustainable capture- ing is more suitable for developing areas than costly based aquaculture of rabbitfish in the Pacific Islands. hatcheries. • There is a demand for sustainably produced reef fish • Growing rabbitfish in lagoon cages is inexpensive throughout the region. compared with growing them in tanks, where pump- • Rabbitfish are diverse in color pattern and appear- ing water is required. ance, making some species suitable for the marine • Start-up costs are relatively low. A B C D D Figure 2: A) Juvenile S. argenteus aggregate in large numbers to feed on algae, Fagaʻalu Bay, Tutuila Island, Ameri- can Samoa; B) Adult S. argenteus hovers over reef area, Pohnpei, F.S.M.; C) Pair of adult S. vulpinus near reef area, Pohnpei, F.S.M.; D) Adult siganid exhibiting mottled coloration at night, Palau. Images: A. Seale. 2 UH–CTAHR Sustainable Capture-Based Aquaculture of Rabbitfish in Pacific Island Lagoons AA-1 — July 2019 Biology algal flats are often seen in schools (Figures 2A and 2B Rabbitfishes have an oval and compressed body with show juvenile and adult Siganus argenteus, respectively), a narrow caudal peduncle. Their name is derived from whereas pair-bonding species are typically seen together the large dark eyes and small mouths, with the upper lip on coral reefs (Figure 2C). During rest and at night, broader than the lower lip, resembling those of a rabbit. rabbitfish have the ability to change color to a mottled Rabbitfish have many spines: pelvic fins are formed from pattern (Figure 2D). They may also exhibit this mottled two spines, and there are 13 dorsal and 7 anal fin spines. coloration when stressed, such as during handling. Although their spines are venomous, and wounds from the spines are very painful, the damage inflicted is not Suitable Culture Species as serious as injuries from scorpionfishes, and they are The family Siganidae contains 28 species in the genus not considered dangerous to adult humans [7,8]. Most Siganus, all from the Indo-Pacific region. Five of the spe- rabbitfish have complex and bright color patterns and cies have notably long snouts and were formerly placed range between 10 and 14 inches (25 and 35 cm) in size. in the genus Lo, which is now regarded as a subgenus of Their intestines are long because they eat mainly plants. Siganus [7]. Generally, the reef-associated pair-bonding They are active during the day (diurnal) and are mainly species are of limited aquaculture value, whereas gregari- herbivorous grazers, feeding on algae, seagrasses, and ous schoolers, which are non-aggressive and can handle in some cases, small invertebrates such as tunicates and large changes in temperature and salinity, are considered sponges. Their skin is smooth with small scales, and the to have the greatest commercial value and aquaculture caudal fin varies in shape from truncate to deeply forked. potential. Several species of siganids have been reared in Rabbitfish are generally split into two groups based on hatcheries with success, including S. randalli, S. cana- their behavior: pair-bonding individuals and gregarious liculatus, S. lineatus, S. fuscescens, S. rivulatus, and S. schoolers. Most species that forage in seagrass beds and guttatus. Many studies on spawning, seedstock produc- Foxface rabbitfish, Often targeted and cultured for the marine ornamental Siganus vulpinus trade. Golden rabbitfish Fully developed aquaculture and controlled hatcheries Siganus guttatus in Asia Forktail rabbitfish Siganus argenteus Suitable candidates for capture-based sustainable cage-culture food fish development in Pacific Island lagoon environments Randall’s rabbitfish Siganus randalli Figure 3: Popular rabbitfishes for culture and marine ornamental trade, including suitable targets for capture-based sustainable aquaculture development. Images: A. Seale. 3 UH–CTAHR Sustainable Capture-Based Aquaculture of Rabbitfish in Pacific Island Lagoons AA-1 — July 2019 tion, broodstock management, and advanced aquaculture adults spawn together based on the phase of the moon. practices are available for two species, S. canaliculatus When larvae hatch, they are carried by tides and currents and S. guttatus, which are currently bred in hatcheries out of the lagoon into the open ocean, where they develop and consistently aquacultured at production levels in Asia for between 30 and 60 days. Larvae undergo a transition, [9,10]. Four species have been used in grow-out trials in which is called metamorphosis, as they return to their the Pacific:S. argenteus (Solomon Islands, Pohnpei, FSM, home lagoons to settle. During metamorphosis the larval and the Cook Islands), S. lineatus