Induced spawning of rabbitfish, Siganus guttatus (Bloch) using human chorionic gonadotropin (HCG)

A positive spawning response of rabbitfish females to two injections of HCG at 2 I.U./g BW given 24 h apart was observed. The latency period after hormone injection was inversely related to the initial oocyte size. Minimum initial oocyte size required for spawning without hormone injection was 0.46 mm. HCG induction of spawning was necessary for females with initial oocyte size of ≤0.45 mm. Number of eggs spawned (424000), fertilization rate (96%), and hatching rate (59%) did not differ from those of naturally spawned fish

The effect of stress on spawning of brood fish and survival of larvae of the rabbitfish, Siganus guttatus (Bloch)

The effects of stress due to handling, and repeated sham and human chorionic gonadotropin (HCG) injections on spawning and survival of the rabbitfish, Siganus guttatus were studied. Results showed that stress significantly enhanced spawning in captive females, but apparently has no significant effect on the survival of larvae. The results indicate that factors other than stress are responsible for the high variability in larval survival in the hatchery. In addition, the results clearly demonstrate the necessity of exogenous gonadotropin to ensure 100% monthly spawning of captive S. guttatus females

Early development and seed production of Asian seabass, Lates calcarifer

[Extract] The Asian seabass Lates calcarifer (Bloch) is widely distributed in the Indo-West Pacific. Because of its high commercial value, it is widely cultured in most of Asia and Australia. However, seed supply from the wild is not abundant; hence the aquaculture of seabass is based on mass seed production in hatcheries. Seabass spawn naturally in captivity (Toledo et al. 1991). Alternatively, they can be induced to spawn by hormonal or environmental manipulations (Kungavankij 1987, Garcia 1989a, b). the development of methods for broodstock management for reliable reproduction of seabass under captive conditions paved the way for studies on the environmental, physiological and nutritional requirements of the developing larvae and the development of protocols for seed production in the hatchery e.g., Parazo et al. 1998, Schipp et al. 2007).\ud \ud Survival of marine fish larvae is dependent on the interplay of various environmental factors (e.g., temperature and water quality, as well as availability of good quality and nutritionally adequate food supply) with a suite of species-specific characteristics including egg and larval size, amount of energy reserves (volume of yolk and oil globule, if present), utilization rates of energy stores (resorption rates of yolk and oil globule), metabolic demand, initiation of feeding and feeding success, growth rates, swimming and feeding behavior. In general, size provides an advantage (i.e., large eggs give rise to large larvae with large yolk reserves which will sustain larval development and allow the larvae sufficient time to initiate feeding before the onset of irreversible starvation (May 1974)).\ud \ud This Chapter outlines the characteristics of L. calcarifer eggs and larvae, the changes during embryonic and larval development, advances in seed production and at the same time highlights the relative ease in its mass production

mRNA expression patterns for GH, PRL, SL, IGF-I and IGF-II during altered feeding status in rabbitfish, Siganus guttatus.

Feeding time is a major synchronizer of many physiological rhythms in many organisms. Alteration in the nutritional status, specifically fasting, also affects the secretion rhythms of growth hormone (GH) and insulin-like growth factor-I (IGF-I). In this study, we investigated whether the expression patterns for the mRNAs of GH, prolactin (PRL) and somatolactin (SL) in the pituitary gland, and insulin-like growth factor I and II (IGF-I and IGF-II) in the liver of juvenile rabbitfish (Siganus guttatus) follow a rhythm according to feeding time and whether these hormone rhythms changes with starvation. Hormone mRNA levels were determined by real time PCR. The daily expression pattern for the mRNAs of GH, PRL and SL was not altered whether food was given in the morning (10:00 h) or in the afternoon (15:00 h). The daily GH mRNA expression pattern, however, was affected when food was not available for 3 days. In contrast, the daily expression pattern for IGF-I mRNA reaches its peak at roughly 5–6 h after feeding. This pattern, however, was not observed with IGF-II mRNA. During 15-day starvation, GH mRNA levels in starved fish were significantly higher than the control fish starting on the 9th day of starvation until day 15. The levels returned to normal after re-feeding. In contrast to GH, PRL mRNA levels in starved fish were significantly lower than the control group starting on the 6th day of starvation until 3 days after re-feeding. SL mRNA levels were not significantly different between the control and starved group at anytime during the experiment. Both IGF-I and IGF-II mRNA levels in starved group were significantly higher than the control fish on the 3rd and 6th day of starvation. mRNA levels of both IGF-I and II in the starved fish decreased starting on the 9th day of starvation. While IGF-I mRNA levels in the starved group continued to decrease as starvation progressed, IGF-II mRNA levels were not significantly different from the control during the rest of the starvation period. The results indicate that aside from GH and IGF-I, PRL and IGF-II are likewise involved in starvation in rabbitfish

Sustainable milkfish production in marine fish cages through strong government support and effective public-private partnerships: a case study from Panabo City Mariculture Park in Davao del Norte, Philippines

This case study presents the successful practice of sustainable intensification of milkfish aquaculture in marine fish cages under semi-intensive grow-out conditions in the Panabo City Mariculture Park (PCMP) in Davao del Norte, Philippines. Established in 2006, PCMP became operational through the promulgation of a City Ordinance declaring 1 075 hectares of municipal waters in Panabo City as a Mariculture Development Zone/Park. The operations of PCMP were so successful that in just five years it became the third largest among the 63 operational MPs in the Philippines during 2011, with 86 private investors-locators operating a total of 322 units of cages. At present, a total of 372 units of fish cages are operating in the mariculture park (MP). A combination of factors contributed to the successful operation of PCMP, but the success is usually attributed to the effective partnership between the government (both local and national) and the private sector. The Comprehensive MP City Ordinance that governs the PCMP is strictly implemented and includes, among others, the tenurial rights and access to locators. Regulations on distances between cages are strictly enforced and security measures in the total area are jointly undertaken by the government and the locators. The national government, through the Bureau of Fisheries and Aquatic Resources-National Mariculture Center (BFAR-NMC), provides technical support in all aspects from stocking to harvest during the production cycle. BFAR-NMC staff conduct regular periodic sampling of the stocks and compute feeding rates for the stocks which are implemented by the technicians/caretakers. Likewise, BFAR-NMC staff regularly monitor the water quality of the MP and the health status of the stocks. Since it became operational in 2006, the PCMP did not report a single incident of mass fish kill, which indicates that the technical guidelines of MP operations are strictly followed. Workers are trained and organized into groups by BFAR-NMC such as caretakers, cage framers, netters, harvesters, fish processors, and others, and actively participate in discussions related to MP operations to ensure protocols are properly followed. Harvests of stocks are done by skilled workers trained by BFAR-NMC, all done in the “Bagsakan Center” or fish landing area and are well-coordinated. The support facilities in the fish landing area are provided by both the local and national government and the PCMP Producers Association. The operators provide complete data for their operations to BFAR-NMC for record keeping. The strong partnership between the national government through BFAR-NMC, the local government unit, the investors, as well as the acceptance and support from the community for the PCMP is the hallmark of its success

Thyroxine injection of female rabbitfish (Siganus guttatus) broodstock: changes in thyroid hormone levels in plasma, eggs, and yolk-sac larvae, and its effect on larval growth and survival

The thyroid hormone levels in female rabbitfish, Siganus guttatus, plasma, eggs, and yolk-sac larvae were measured before and after thyroxine (T4) injection in female spawners at doses of 1, 10, and 100 μg T4/g body weight (BW) fish. T4 and triiodothyronine (T3) levels in maternal plasma, eggs, and yolk-sac larvae were elevated following T4 administration. Apparently, there is conversion of T4 into T3 in the broodfish which suggests the presence of the enzyme, 5′-monodeiodinase, in rabbitfish. T4 and T3 in maternal circulation were easily transferred into the oocytes and subsequently into the larvae. Larvae from spawners treated with 10 and 100 μg T4/g BW tended to be longer and showed sornewhat better survival compared to the control and those injected with 1 μg T4/g BW 7 days after hatching. These findings suggest that thyroid hormones may play an important role during early larval development of rabbitfish

Nursery and grow-out culture of Asian seabass, Lates calcarifer, in selected countries in Southeast Asia

In this chapter, the practices of growing Asian seabass in nursery and grow-out culture systems in selected Southeast Asian countries like the Philippines, Thailand and Indonesia are described

Seed production of rabbitfish Siganus guttatus

This manual is mainly intended to serve as a practical guide to fishfarmers and other stakeholders interested to venture in operating a rabbitfish hatchery. It details site selection, hatchery design & layout, and protocols in broodstock management, spawning, larval rearing, and harvest & transport. It has also a section on natural food production for rabbitfish larvae