Evaluation of artificial feeds for shrimp (Penaeus monodon) production in brackishwater ponds

Abstract only.The experiment was conducted in fifteen 500-m2 brackishwater ponds to determine the response of Penaeus monodon juveniles fed with various artificial diets. Five treatments with three replicates each were: two commercial feeds containing 45% and 40% crude protein (treatments I and II), two experimental diets formulated to contain 35% crude protein (treatments III and IV) and control, without feeding (treatment V). Shrimp were fed twice daily at feeding rates based on shrimp consumption. Highest mean harvest weight was attained in treatment I (23.47 g) > III (19.25 g) > II (18.86 g) > IV (11.29 g) > V (9.27 g). Statistical analysis showed that differences in growth were significant at 5% probability level. However, growth in treatments I, II and III are comparable, also growth in treatments II, III and IV. Growth in treatments I, II, III and IV was significantly different from treatment V. Highest mean survival was attained in treatment III (91.82%) > I (88.93%) > II (86.95%) > IV (83.62%) V (82.62%). Statistical analysis showed no significant differences among treatments at 5% probability level. Projecting on a hectare basis, mean yield for each treatment was: I (628.37 kg) > II (496.35 kg) per crop in 120 days culture. Good yield was attributed to provision of formulated feeds, use of pumps in addition to tidal change for water exchange and control of predators, and pest eradication through proper pond preparation

Induced spawning and larval rearing of grouper (Epinephelus salmoides Maxwell)

Excerpt from The First Asian Fisheries Forum. Asian Fisheries Society, Manila, Philippines.Broodfish of grouper (Epinephelus salmoides ) were induced to spawn by hormonal induction. The hormones used for this experiment were HCG + pituitary gland (PG) and LRH-a. The results showed that at dosages of 500 IU HCG + 3 mg of PG per kg of fish for first injection and 1,000 IU HCG + 3 mg of PG per kg of fish at the final injection at an interval of 24 hours, the treated fish spawned naturally in a spawning tank 12 hours after the final injection. At lower dosages of 500 IU HCG + 3 mg PG at 12-hour intervals or 500 IU HCG + 3 mg PG at 24-hour intervals or using 10 mg LRH-a at 12-hour intervals, the eggs can be artificially fertilized only by stripping. The larval rearing experiment was conducted in a 250-l fiberglass tank at the stocking density of 2,500 larvae per tank. Feeds used in this experiment were: (a) Isochrysis + sea urchin eggs; (b) Isochrysis + Brachionus ; and (c) Tetraselmis + Brachionus . The results showed that newly hatched larvae fed with Isochrysis mixed with sea urchin eggs and then Brachionus from day 10 had the best survival rate (9% at day 30)

Acetes as prime food for Penaeus monodon larvae

This paper presents research attempts to develop a suitable artificial diet for shrimp larvae with locally-available materials. Larval rearing experiments using finely ground Acetes tissues conducted under various climatic conditions and hatchery systems were completed. In the dry season, larvae in outdoor tanks fed dry Acetes had the highest survival rate (68%) compared to larvae fed Chaetoceros (48%) or fresh Acetes (39%). In contrast, larvae from an indoor hatchery reared with Chaetoceros had higher survival rate (52%) than those fed with Acetes (35%) and fresh Acetes (24%). During rainy months, the survival of larvae reared with Skeletonema , dry and fresh Acetes in outdoor tanks was 72%, 52% and 38% and in indoor tanks 62%, 40% and 23%, respectively

Spawning response latency and egg production capacity of LHRHa-injected mature female sea bass, Lates calcarifer Bloch

Mature female sea bass (Lates calcarifer Bloch) were injected once intramuscularly with 20 μg luteinizing hormone-releasing hormone analogue (D-Ala6, Pro9-LHRH-ethylamide) per kg body weight (BW) at different times of the day. Following hormone injection, the incidence of initial spawning and the number of eggs spawned by each fish were recorded. Saline-injected fish did not spawn. Fish spawned at dawn or 33.7–40 h after an LHRHa injection at either 11.00 h or 17.00 h. When LHRHa was administered at 23.00 h or 05.00 h, sea bass spawned during the day or at 38–47.3 h post-injection. Mean egg production levels of 26.8–34.4 × 104 per kg BW were higher for fish which spawned at dawn. Low mean egg production levels (6.2–19.9 × 104 eggs per kg BW) were observed when LHRHa-injected fish spawned during the day. These results demonstrate that the time of initial occurrence of spawning varied with the time of day that LHRHa was administered and that the number of eggs shed was influenced by the time of day that hormone-induced sea bass spawned

Size- and weight-dependent cannibalism in hatchery-bred sea bass (Lates calcarifer Bloch)

The relationship of predator size to maximum prey size, and predator weight to weight of prey consumed among cannibalistic sea bass (Lates calcarifer Bloch) in a hatchery were assessed. Maximum prey size was computed from morphological measurements (predator mouth width, prey body depth and fish total length), while prey consumption was determined from predators kept in experimental beakers and fed only prey sea bass for a 7-day period. Maximum prey size was 61–67 % of predator total length $(TL_{prey} = 0.5944 TL_{predator} + 0.0724)$. Gut dissection of predators showed that size of ingested prey increased with increasing predator size not exceeding the maximum size limit indicated by the above equation. Daily prey consumption of predators in the beakers was expressed as $W_{Prey} = -0.2407\; W_{predator^{2}}+ 0.7697W_{predator}-0.1141$. During hatchery rearing of sea bass, fish with length differences of more than 33 % must be separated and food of appropriate size provided to limit cannibalism

Bioactivity of stored luteinizing hormone-releasing analogue (LHRHa) in sea bass, Lates calcarifer Bloch

The spawning induction activity of dissolved and pelleted (D-Ala6, Pro9 N ethylamide) luteinizing hormone-releasing hormone analogue (LHRHa) stored for various periods was assessed in mature female sea bass. The spawning response of mature fish was reduced significantly after injection of dissolved LHRHa (20 μg kg−1) stored for more than 90 days in a refrigerator (4–10°C) or for more than 30 days at room temperature (28–30°C). Similar to fish administered fresh preparations of LHRHa, fish spawned successfully after injection of a solution of LHRHa previously frozen, subjected to alternate freezing and thawing, exposed to sunlight or implanted pelleted LHRHa (50 ng kg−1) stored at room temperature for 30–120 days. Loss of hormone bioactivity after prolonged storage may have been due to bacterial growth in solubilized preparations. Injection or implantation of stored LHRHa did not influence egg production among treated sea bass. These results demonstrated the relatively prolonged shelf life of stored LHRHa