News & Events
CTSA Ongoing Projects: Midterm Updates
Jun 17, 2014
Aquaculture Potential of Hawaiian Polychaetes for Use as a Shrimp Maturation Feed
Several species of polychaetes have been collected from various locations around Oahu including sediments at He’eia Kea state park, He’eia Kea boat harbor, Waiāhole beach Park and Maunalua Bay, and on floats beneath a dock at Pearl Harbor. The species that were identified as candidate species for culture include Marphysa sanguinea (Fig. 1), Lumbrineris japonica, Sabellastarte spectabilis, Malacoceros indicus, Chaetopterus variopedatus, and Sipunculida sp. On each occasion that polychaetes were collected for transport to Oceanic Institute (OI), 20% of the collected worms were screened for the presence of White Spot Syndrome Virus, Taura Syndrome Virus, Infectious Hypodermal and Hematopoietic Necrosis Virus, and the bacterium causing Early Mortality Syndrome. In addition to screening of worms prior to transport to OI, a subsequent disease screening was performed on tissue from shrimp that were maintained in the effluent water from the polychaete culture vessels and/or consumed tissue from the cultured polychaetes.
Specimens of all previously mentioned species and some unidentified species have been successfully cultured for over three weeks in the OI culture system (Fig. 2). Lumbrineris japonica and the Sipunculida sp. have been cultured for over 90 days. Gametes (eggs) were obtained from some of the polychaete species. We are currently developing methods for successful spawning/fertilization. Four of the six candidate species have been screened for palatability. One species, Marphysa saguinea, appeared to be preferred by the shrimp. This species is now being focused on as a primary candidate for development of culture methods.
Thus far, this project has fostered the development of a better understanding of the habitats in which polychaetes that are viable as shrimp feeds can be found. We now know the optimal areas in which to look for these large polychaetes. We have also identified a primary species, M. saguinea, on which to focus future work. The accomplishment of this step in the project is of great benefit to the industry. We have shown that there are species of polychaetes in Hawaii that are of suitable size and palatability to be used as shrimp broodstock feeds. In the coming months we will develop methods for culturing this species and develop nutrition profiles to ensure that this species will provide adequate nutrition for shrimp broodstock.
Broodstock Management, Seed Production and Grow-out of Rabbitfish, Siganus lineatus (Valenciennes, 1835) in Palau, Year 2
The rabbitfish broodstock that have been spawning in Tank 2 were again sorted and split to two separate broodstock tanks to further monitor the spawning. Each tank was stocked with 24 fully matured spawners with the sex ratio of 1 female: 2 males. Rabbitfish spawners in Tank 1 were fed with high protein shrimp feeds while those in Tank 2 were fed with milkfish feed. Spawning was monitored five days prior and after the full moon of each month and the first spawning for the year 2014 occurred on March 16 to March 21 in both Tank 1 and Tank 2. The total number of eggs produced from each tanks was 1,266,334 and 1,200,667 with 74% and 68% viability, respectively. The average hatching rate was 40% in Tank 1 and 34% in Tank 2. Successive spontaneous natural spawning was recorded in the succeeding months that took place 3 to 5 days before and after the full moon phase.
A preliminary larval rearing trial was conducted utilizing the eggs that were spawned on March 20, 2014. About 250,000 newly hatched larvae were stocked in a 5ton capacity larval rearing tank. The rearing water was sterilized by adding 5liter chlorox solution and was subsequently neutralized after 1 hour with 600g Sodium Thiosulfate prior to stocking of the larvae. Rotifers Brachionus rotundiformes that serve as initial live food organism were added into the rearing water the next day after stocking with a density of 5 rotifers per ml. About 10liter fully grown live microalgae Nannochloropsis sp. was added to nourish the rotifers in the larval rearing water. After Day 12, the larvae were fed with newly hatched artemia at a density of 0.5 per ml. Feeding of artemia was continued until Day 21 at the density of 5 artemia per ml. About 2,352 larvae have survived after 21 days of culture making the survival rate equivalent to about 1%.
Another larval rearing trial using 4 units of 5ton capacity larval rearing tanks was conducted in May 12, 2014. The purpose of this trial was to compare the survival rate of the rabbitfish larvae when frozen algae paste product and live micro-algae were added into the larval rearing water as food for the rotifers. Each tanks were stocked with 250,000 newly hatched larvae and were given the same amount of rotifers and newly hatched artemia throughout the larval rearing period following the previous larval rearing feeding scheme. Two tanks were added with frozen algae paste product (Nanno 3600, Reed Mariculture Instant Algae) while the other two were given 10L fully grown live Nannochloropsis sp. Larval rearing was terminated after 21 days of culture and the larvae in tanks fed with frozen algae paste product had an average survival rate of 2.8% while those larvae in tanks fed live microalgae had only 1%.
The 2,352 pieces 21days old rabbitfish fries that were produced in April 2014 were further grown inside the same tank to continue the nursery phase of rearing until they metamorphose into about 0.5 to 1inch fingerlings. The fry were fed with artemia at a density of 5 individuals per ml and 10g artificial feed each day. Gradual mortalities were observed starting Day 27 until Day 34 when the fry started to metamorphose and graze on the filamentous algae that grew on the walls of the tank. At Day 37, the rabbitfish fry were observed to have completely metamorphosed and about 798 pieces 1inch fingerlings were harvested. The survival rate on this preliminary nursery rearing trial was about 34%.
To document the growth and survival of hatchery-produced rabbitfish, a preliminary grow-out trial was conducted utilizing the fingerlings that were produced. A total of 798 pieces 40 days old fingerlings with average body weight of 1.02g and total length of 1.8cm were stocked in a 2m x 6m rectangular concrete tank with a water depth of about 0.5m. The tank was designed to have a flow-through water system and the fingerlings were fed with commercial feed powder and crumbles. After 50 days of culture the rabbitfish fingerlings were sampled and the average body weight and total length of the 3 months old was already 6.69g and 7.11cm respectively.
Establishing bivalve farming in Hawai`i
Researchers are assessing the effects of seasonality on reproduction and condition index (CI) for Crassostrea gigas in Hawai`ian fishponds and other sites to determine ideal harvest and stocking schedules and maximum stocking densities. Preliminary results indicate that although the growth rate is high enough to produce 3-4 inch oysters in 6-9 months, the condition index is low. This indicates that diploid oysters are not “fattening” well, i.e. glycogen deposition is low. This is common with diploid oysters in warm water areas. While the oysters are still marketable, this indicates the need to develop a diploid oyster that performs better in the warm waters that characterize Hawaii. It is also interesting to note that oysters produced using broodstock from the OSU Molluscan Broodstock project (MBP) grow more rapidly and have a higher condition index than oysters produced using “wild” Oahu broodstock. This suggests that if Hawaii is to develop a selective breeding program to improve oyster performance, starting with MBP stock may be a strategy to develop an improved oyster strain more quickly than starting with wild stock.
The alternative is to use triploid oysters for culture in Hawaii. Kualoa Ranch, the only oyster farm that is selling oysters to date, is focusing on growing triploids which have much better meat production. The issue with triploids is that there is a general scarcity, and new or small producers have difficulty in obtaining small amounts of large, triploid spat on a regular basis. Additionally, the patent which covers production of tetraploids which are the most efficient way to produce triploids, expires in early 2015. There is general concern in the industry that once the patent expires, the patent holders may not continue producing tetraploids due to the possible lack of financial potential. Even now, obtaining tetraploid oysters under a licensing arrangement has been extremely difficult. Hawaii needs to assure it can produce its own tetraploids and triploids once the patent expires or risk stifling Hawaii’s industry development at this early stage.
We have now been selectively breeding Dendostrea sandvichensis for three years and larger sizes (over 2 1/ inches) have been obtained. The growth rate is slow, which may limit production, similar to the same phenomena with Ostrea conchaphila (Olympia oyster), although the latter is still a highly desired product. Hawaiian oysters may now be a feasible market product. He`eia pond has approximately 4000 D. sandvichensis under culture. Keawanui has approximately 2000. Aside from the possibility of marketing these oysters, the Hawaiian fishpond practitioners are also interested in working to restore the species in the wild as it is now uncommon in areas where it was found before. We purchased Kumamoto broodstock from the OSU MBP repository farm and a cooperating oyster farm in Washington was holding these oysters so they could develop gametes naturally. Unfortunately these broodstock were lost in a winter storm. The cooperating farm owner has promised to replace these free of cost; this is expected in June 2014.
Initial trials using predator exclusion mesh for manila clam culture were not effective. We conducted a trial in He`eia pond using weighted predator mesh that is commonly used in the Northwest U.S. for predator exclusion. Total mortality resulted due to crab predation. Cage culture of clams has produced better performance although growth is still slow compared to the Pacific Oysters. Therefore, clams may represent an alternative product for some producers, but is is clearly more feasible for most beginning producers to focus on oyster production. Regarding outreach, we have worked closely with the four stakeholder groups in Hawaii since this research is largely conducted in a participatory manner and have provided training through this modality. The printed materials are awaiting completion of the remaining research. We have also worked closely with the new oyster hatchery in Hilo and their WA State parent company on this research.
Developing diets for Hawaii cultured abalone with normal shell color and high growth performance using local algae and their co-products- Year 2
Five diets were formulated including control diet and the diets supplemented with 3% dried pacific dulse, porphyra or spirulina pigment ingredients or 0.015% extracted shell pigment. Fresh Pacific dulse sample was collected from Big Island Abalone Corporation (BIAC) and freeze-dried at OI Nutritional Biochemistry lab. The dried Porphyra seaweed was purchased from local supermarket. Spirulina byproduct was from support of Cyanotech Incorporation. Shell bilin pigments (mainly containing biliverdin and cysteine-biliverdin) were extracted from shell of Ezo abalone of BIAC. Algae sample including Pacific Dulse, Porphyra and Spirulina contained bilin pigments of Phycocyanobilin or/and Phycoerythrobilin, which are isomers of the abalone shell pigment (biliverdin). The five diets were processed by extruder method at Feedmill of Oceanic Institute (OI) and shipped to BIAC for the feeding trial. Each of 20 buckets was stocked with around 1000 abalone (4.0 kg). Each of the five diets singly fed three repetitive buckets and Kelp seaweed (protein enhanced) from BIAC fed two repetitive buckets. Two commercial feeds currently used by BIAC, Abfeed and Abkelp boosted protein were used as reference diets in the feeding trial. The feeding trial was performed by a hired student, a BIAC expert (Ms. Cecilia) and technicians. Abalone weight and shell length were measured monthly, and mortality, feed amount and floating feed pellet number were recorded daily. After 5 months feed trial, 20 buckets of abalone were harvested. Forty abalones from each of the tested buckets were randomly sampled; the individual abalone sample was weighted, measured its shell length and recorded its shell color appearance. The 40 abalone from each bucket were shipped to OI for nutrient and pigment analysis. All the remaining abalone were sorted and graded; qualified abalone (90%) were loaded to BIAC production line and continued culture until market size.
The five-month growth data found that OI formulated and processed diets had better growth performance than Abfeed from South African (P>0.05) and Abkelp boosted protein diet from Mexico (P
0.05) among five OI diets.
Developing Strategies for the Prevention and Mitigation of Francisella noatunensis subsp. orientalis (syn. F. asiatica) Outbreaks in Cutltured Tilapia in Hawaii
Fno bacteria has been successfully isolated and cultured from an outbreak during the reporting period. To address the objective to determine whether Fno remains in the environment after infected fish are removed, an Fno challenge test is being planned where naïve O. honorum, O. aurea and O. mossamibcus will be exposed to the Fno pathogen and the infection can be monitored both in the infected fish and also the water column.
Currently, project work group members have established a means when Fno has been identified in a private backyard aquaponic system, the tilapia are removed from the system for a minimum of two weeks. The system is allowed to go fallow during that time and no disinfection is done. It has been found that the available nitrate remains elevated and may represent a cost effective means of eliminating the pathogen, particularly in an aquaponic system. At the end of the two-week period, known Fno free tilapia stocks are replaced to the owner’s system. At present, most of the Fno free tilapia are sourced from our Windward Community College Facility. However, with the Fno free certification of Hapa Farms and B&B Nursery, additional backyard aquaponic producers have begun to use them as sources of Fno free tilapia stocks. If success of fallowing continues, it is anticipated that we have a means to mitigate the pathogen in backyard aquaponic units.