Quality Seeds for Sustainable Aquaculture

Success in sustainable aquaculture production depends primarily on the availability of good quality seedstock for rearing to marketable sizes using efficient husbandry techniques under suitable farm conditions. AQD therefore determined the optimal conditions and methods to produce adequate quality seedstock by adopting conventional methods of stock improvement, i.e. domestication, broodstock management, strain evaluation and selective breeding or genetic improvement of traditional and emerging freshwater and marine aquaculture species. Biotechnological tools such as DNA markers were used in screening some key aquaculture species to complement the management and selection schemes in genetic improvement. Although genetic intervention can enhance the desired traits in the production of good quality seedstock, i.e. improved growth rate, survival, disease and stress tolerance, broodstock and seedstock improvement through nutritional intervention is also considered. Suitable hatchery and nursery protocols are being developed and refined depending on the level of technology for each species.

Broodstock development

Stock characterization using molecular markers was adopted by AQD to determine the genetic quality of hatchery stocks, so that for the genetic characterization of the abalone (Haliotis asinina) and mangrove crab (Scylla serrata), molecular markers (e.g. mtDNA and/

or microsatellite markers) have been used. Nutritional intervention was also carried out to improve the reproductive traits, especially for tiger shrimp, Indian prawn, sandfish, tilapia, and giant grouper while better breeding stocks of these species are also being developed.

For the abalone, six microsatellite or short tandem repeat (STR) DNA markers were used to characterize the existing AQD stocks and nine wild stocks to be used for broodstock genetic assessment. Abalone stocks or strains with high genetic variability implies genetically better or more fit and adaptable. Initial results indicated that the wild stocks from Agusan del Norte (Mindanao) and Palawan (Luzon) had the highest variability based on the number of alleles (A = 17.8 and 15.5, respectively) and expected heterozygosity (Hexp = 0.861 and 0.901, respectviely). The lowest genetic variability was noted in the stock from Sagay (Visayas) (A = 5, Hexp = 0.792) with the AQD hatchery stock from Iloilo (Visayas) having variability indices that were slightly higher (A = 8 and Hexp =0.872).

Spawning batches were set up for strain comparison of the abalone in terms of reproductive efficiency.

Molecular marker variation data were obtained and correlated with breeding performance. The results showed that the AQD hatchery-bred abalone stocks had the highest number of eggs as well as the number of eggs per gram body weight (BW) of female.

Among the wild abalone, the broodstock from Zamboanga del Sur had the highest fecundity while those from Pangasinan had the most number of eggs/g BW of female, but the stocks from Cebu had the highest larval survival rate. This information and those obtained from the molecular marker variation assessment would be used in the formulation of a broodstock management and selective breeding scheme for the abalone.

For the mangrove crab stocks, genetic characterization based on three novel and three existing STR markers, was carried out to maintain the genetic quality and to check for the negative impacts of domestication in several generations of selected and control stocks from Camarines and Surigao. Initial analysis of the data based on uncorrected estimates of the number of alleles (A) showed that the parental stocks from Camarines and Surigao had 10.17 and 10.33 A, respectively, while two batches of the first generation Camarines control stocks had lower A at 6.67 and 6.5, respectively, and one batch of the first generation Surigao control stock had 6.33. Slightly lower A estimates were noted in the first-generation selected stocks from Camarines (6.17 and 6.5) and Surigao (4.0). The expected heterozygosity estimates were not significantly different between the stocks and across generations based on the existing batches screened. Molecular marker data are being correlated with parameters for selected beneficial traits to determine if the markers could be used as preliminary indicators for genetic improvement.

Hatchery-bred abalone breeders

For the tiger shrimp (Penaeus monodon), experiments to determine the differences and problems in breeding performance of male and female spawners from captive and wild environments, were conducted to understand the conditions that encourage and facilitate mating. Initial findings indicated that the wild and captive male shrimps appeared to pursue more frequently the wild female shrimps than the captive ones. The incorporation of vitamin C in the shrimp broodstock diet reduced the incidence of mortalities in domesticated shrimp broodstock. When young postlarval stages (for on-growing to potential broodstock size) were fed 2% taurine, mass weight was significantly higher compared to treatments with lower taurine levels. On their reproductive performance, tank-reared spawners matured until stage 2 but no stocks matured in the pens. Moreover, polychaete meal would be incorporated in the formulated broodstock diet for adult Indian prawn stocks to determine the effect of these diets on male sperm quality, female ovarian maturation and reproductive performance. The polychaete meal and the test diet are being analyzed further for their proximate composition and stability.

For the sandfish (Holothuria scabra), appropriate diet to improve breeding performance and larval quality in sandfish, is being developed. The basic biological composition (protein, lipids, fatty acids, etc.) of wild and hatchery-produced sandfish were determined. Using the proximate composition of wild-caught mature sandfish as reference, the practical diet is being developed to ensure that the nutritional requirements for enhancing breeding

performance in adult sandfish are met. Preliminary feedings suggest that sandfish would require only low dietary levels of both protein and lipid, and that high lipid content appears to impede their growth.

In the development of technologies for aquaculture of giant grouper, broodstocks had been collected from local sources and kept at the Igang Marine Station for regular monitoring of gonadal maturity. Molecular characterization of the stocks and induced spawning trials had been started. Hybridization has been tried at AQD by crossing a female giant grouper with male tiger grouper.

The effectiveness of biofloc as starter feed and settlement substrate for early stage polychaete (Marphysa mossambica) is being analyzed. Critical stages during early development, optimum stocking density and sediment depth required during their nursery and grow-out phases, and the effect of light exposure on the growth and survival in the grow-out phase, are being established. Egg hatchability and larval development of M. mossambica subjected to varying irradiance and photoperiod treatments are also being investigated.

Maturation diets are being refined to improve reproductive performance of

sandfish

Polychaete Marphysa mossambica:

4 days after hatching (left) and adult (right)

Refinement of hatchery and nursery protocols

Enhancements to laboratory and field-scale production of natural food organisms and alternative food items which serve as early stage diets were evaluated by AQD to increase production of the larval and juvenile stages of important aquaculture species. Improvements on rearing conditions and interventions to enhance survival of aquatic organisms during larval development were also carried out.

For the abalone, the effectiveness of using chemical cues (positive ions, algal extracts) to improve settlement rate and increase production of juveniles through improved culture techniques has been established by AQD. Efficient sorting and harvesting protocols using muscle relaxant were developed to improve the survival rate of abalone juveniles.

For the effectiveness of algal cues as settlement inducer, the presence of agar-bound microparticulate diet and ammonium chloride (NH₄Cl) on top of the diatom Nitzschia sp., resulted in consistently higher settlement rates in transparent tanks of 12.06% and 2.83% after 5 and 10 days, respectively, compared to only Nitzschia sp., which produced settlement rates of 5.11% and 1.95%, respectively. When the potential chemical cues (NH₄Cl, GABA and serotonin) for abalone settlement were tried in bigger tanks, i.e. in 1.5- ton fiberglass tanks using NH₄Cl in combination with Arthrospira platensis and Nitzschia sp., highest settlement rate of 4.49% was attained after 5 days, while settlement after 10 days was 1.95%.

For the blue swimming crab (Portunus pelagicus), a formalin stress test has been promoted in hatcheries to ensure that only good quality larvae are used for further rearing. Results in hatchery and nursery-rearing of the blue swimming crab, indicated that crab instar 1-2 could tolerate salinities of 16-32 ppt, and about 8-20 ppt for the later stages (crab instar 3) but higher survival was achieved at 16-32 ppt. Crab molting intervals and increments were similar in all salinities from 16 to 32 ppt. The optimal stocking density for nursery rearing of the blue swimming in hapas within pens was then established at 10-15 individuals/m². For the hatchery rearing of mangrove crab seedstock, the use of algal paste in rotifer culture was evaluated. Nanochlorum paste was used in rotifer culture but Tetraselmis paste proved to be a better option. Therefore, in order to improve the growth and density of rotifer, the protocol for the use of Tetraselmis paste will be established and compared with the Nanochlorum batch culture.

Pompano (Trachinotus blochii) are opportunistic feeders and can readily feed on wild zooplanktons present in ponds or in fish cages in marine waters. As means of attracting wild zooplanktons as supplemental food in the culture of pompano, the possibility of using artificial lighting in the nursery net cages was explored to reduce the costs of feeding caged pompano with formulated diets especially during its early stages.

For the growth and survival of sandfish juveniles up to 20 g fingerling size, rearing was divided into two nursery phases: primary nursery phase for early juveniles (5 mm > fish >

40 mm or 3 g) and secondary nursery phase for late juveniles (3 g = fish > 20 g). The use of shaded and open hapa-in-tank nurseries was compared in rearing the sandfish, and the results showed that growth of sandfish juveniles in shaded tanks was twice greater than those in open tanks during the first month but on the second month, sandfish in the open tanks grew faster.

The potential of using locally-available microalgal strains as food for the minute rotifer, Proales similis de Beauchamp, was evaluated while the biochemical, proximate and cost of producing Chlorella sorokiniana microalgae was determined.

Semi-batch culture trials showed lower cost of C.

sorokiniana paste production. Also, P. similis could tolerate high salinity (30 ppt) but better results could be obtained if acclimatization is done prior feeding with the algae.

For milkfish (Chanos chanos), a protocol for transporting juveniles (average total length of 5-6 inches) from the nursery to sea cage facilities was developed, and the optimal temperature and salinity requirements for their transport had been defined. Preliminary findings showed that survival of milkfish juveniles a week after being transported for 4 to 6 hours at 25°C regardless of salinity levels (0 to 20 ppt) attained high survival (94-100%), while transporting milkfish juveniles at 25°C in higher salinities resulted in good survival. Prolonging the transport time to 12 hours did not have any adverse effect on the juveniles.

Experimental setup on the use of artificial illumination in the floating cage culture of pompano

Minute rotifer (Proales similis) used as food for fish larvae

Size of milkfish juveniles used in the transport experiment

Promotion of technically and economically-viable breeding and seed production schemes The breeding and seedstock production methods developed at AQD were verified on farm to ensure that these are cost-effective. Nile tilapia (Oreochromis niloticus) and giant freshwater prawn (Macrobrachium rosenbergii) seeds were produced at AQD’s Binangonan Freshwater Station (BFS), to verify and demonstrate the methods for urban agri-aquaculture (aquaponics), and the latter to serve the needs of small-scale prawn farmers in the vicinity.

Despite the small-scale production, the total tilapia produced from seed production tanks in March to December was about 111,284 pcs of fry and 70,744 pcs of A-net size seedstock.

On the other hand, 53,970 fry and 29,145 A-net size seedstock were obtained from the tank meant for producing potential broodstock. All the seedstock produced were stocked in cages for on-growing to fingerlings or juveniles.

For the giant freshwater prawn, broodstock on-grown from juveniles obtained from the BFS hatchery-bred stock, were placed in 12 units of spawning tanks. Results showed that postlarvae (PL) production from January to August 2017 was recorded at 248,094 pcs with 54.11% survival to PL and mean number of days of metamorphosis to PL at 43. In April, breeder performance was poor with no PLs produced. Potential spawners were thus obtained from Isabela Province in September and stocked for spawning. In October, PL production totaled 33,771 with 65% survival to PL, while November data recorded production of 26,427 PL but still awaiting metamorphosis to PL and in December production data recorded 101,840 hatchlings and awaiting metamorphosis to PL.

To verify, demonstrate and promote prawn- and/or tilapia-based urban agri-aquaculture technologies, two portable aquaponic systems were constructed at BFS. In the first set-up, water morning glory or “kangkong” (Ipomea aquatica) seedlings were transplanted to the aquaponic substrates (1 cocopeat:1 carbonized rice hull:1 fine sand:1 plain rice hull). Giant freshwater prawns (12 pcs, ave wt: 10.74 g) and red tilapias (40 pcs, ave wt: 34.8 g) were stocked separately in the tanks where the red tilapias were fed daily with fish pellets. For the second set up, Chinese white cabbage or “pechay” (Brassica rapa) were planted in the

Portable aquaponics setup to explore the possibility of promoting the

pots while tilapias were stocked in a blue drum that serves as fish holding tank. Training on aquaponic systems would be organized soon.