Ecology and life history of penaeid shrimps

Fourteen species of penaeid shrimps with commercial value in Batan Bay and Tigbauan-Guimbal waters were identified as follows: Penaeus monodon, P.semisulcatus, P.japonicus, Metapenaeus ensis, M.burkenroadi, M.endeavouri, Metapenaeopsis palmensis, M.stridulans, Trachypenaeus fulvus, and Parapenaeus longipes. Among the 14 penaeids, P.semisulcatus, M.ensis and M.palmensis were found to be the dominant species within each genus. There are seven existing fishing gears for shrimping in the Batan Bay and Tigbauan-Guimbal waters: fish corrals, lift net, filter net, gill net, skimming net, baby trawler and commercial trawler. In general, female penaeids are larger than males. The largest P.monodon female measured was 81 mm in carapace length with 23 g in body weight. The largest male measuring 59 mm in carapace length with 119 g of body weight was caught in Batan Bay. Judging from spermatozoa occurrence on both sexes of P.monodon, the biological minimum size for male is 37 mm in carapace length and 49 mm for female. A total of 133 Penaeus postlarvae obtained from the offshore were identified by comparison with those reared in the laboratory. The postlarvae of P.japonicus-latisulcatus complex were quite dominant (60 . 2%), followed by P.semisulcatus (18 . 0%), and P.merguiensis-indicus complex (17 . 3%). The number of P.monodon postlarvae was relatively small (4 . 5%). The modal carapace length of P.monodon postlarvae from the offshore was 1 . 3 mm with three or four dorsal and no ventral spines on the rostrum, while P.monodon fry from the shoreline had 2 . 3 mm with five or six dorsal and one or two ventral spines.

Land-based mass production of prawn (Penaeus monodon Fabricius) spawners

The first spawnings were obtained 12 days after ablation with 4 spawners yielding 784,000 eggs and a harvest of 250,000 P SUB-10 fry. Survival of females after 1 month was approximately 30%. Mortalities were mostly due to handling stress during the regular ovarian samplings as well as disease frm the accumulated excess feeds on the bottom of the tank. Male survival could not be recorded because of transfers to other tanks and addition of new stocks. Development seemed to peak 3 weeks after ablation. The average number of eggs per ablated spawner was 120,000. However, many of the partially spawned females were removed from the spawning tanks the following day so that remaining eggs released in the next 2 to 3 days could not be recorded. Estimate of the average number of eggs per ablated spawner is 120,000-150,000 in contrast to 500,000 per wild spawner. However, the low production cost more than compensates for the difference. Fry reared in the Wet Laboratory were used for experiments, mostly on feeding. Therefore, survival at harvest is not to be taken as a reflection of stock quality. Although fewer in number, larvae from ablated prawns are as healthy in terms of vigor in swimming and feeding as those from wild females. Most mortalities are due to inability to molt caused by lower water temperatures and inadequate feeding.

Notes on ovarian rematuration of ablated sugpo (prawn) Penaeus monodon Fabricius

To what extent spent P. monodon females can remature and spawn successive broods is an important question in terms of recycling spawners in a commercially viable operation. Corollary to this is the quantity and quality of fry from rematured females in comparison to those from first spawning. Of 347 experimental females, only 10.1% had a second spawning, and 1.4% a third spawning. To a large degree the low rate of rematuration is due to high spawner mortality - average survival period after spawning was only 6 days in a sample of 176 spawners. It took an average of 23 days after ablation for a prawn with undeveloped ovaries to mature and spawn. An ablated female may have another spawning in as little as 5 days after the previous one. Average fecundity was 180,000 eggs per second spawning, and 140,000 eggs per third spawning. The average number of eggs from first spawning ablated females was 110-120,000. Hatching rate was lower for rematuration: 44% for second spawnings, and 35% for third spawnings, as compared to 64% for first maturation.

Effect of some physico-chemical factors on the survival and growth of Penaeus monodon postlarvae

Growth and survival rates of P. monodon postlarvae were examined at different temperatures, salinities, and nitrite and ammonia concentrations, using one feed level. Condition of postlarvae greatly affected the experimental results shown in some instances where very low survival rates were obtained, even for the controls. Results indicated that postlarvae from PSUB-10 and up can tolerate salinity changes of 10 to 20 ppt without prior acclimation. Survival generally appears the same for temperatures between 24 and 36 C. It appears that P. monodon postlarvae have higher temperature tolerance. Tolerance of postlarvae at the early postlarval stage is between 30 and 50 ppm of nitrate. They were more tolerant from PSUB-10 upwards. Although survival was high in runs containing nitrite, growing appears to have been affected. Postlarvae could tolerate ammonia concentrations up to about 50 ppm. At 100 ppm higher mortality rates were observed. Whether or not there was any permanent effect by nitrate and ammonia at high but apparently tolerable levels is not known.

On the occurrence of mature penaeid prawn Penaeus merguensis in a shallow solar salt works reservoir along the Okhamandal Coast of Gulf of Kutch and its spawning in laboratory

Penaeus merguensis is so far reported to attain complete maturity and spawn in the sea or deep culture ponds only. Mature specimens of stage III to V collected from a shallow reservoir of solar saltworks were studied and spawned in laboratory. A comparison of spawning of spawner from sea and reservoir is also reported.

Advantages of liquid nitrogen freezing of Penaeus monodon over conventional plate freezing

Liquid nitrogen frozen products are biochemically and organoleptically superior to conventional plate frozen products but beneficial effect of liquid nitrogen freezing over conventional plate freezing can exist only up to 59 days at a commercial storage temperature of -18°C.

Spoilage bacteria of Penaeus indicus

Bacteria isolated from raw (untreated and unprocessed) prawn (Penaeus indicus) stored at 28±2°C, 4°C and-18°C were tested for spoilage potential, namely, production of protease, lipase, amylase, reduction of trimethylamineoxide (TMAO) to trimethylamine (TMA), production of off odours from flesh broth and halo zone around the colony grown on flesh agar. About 63 % of the total isolates tested were potential spoilers. Members of Vibrio, Pseudomonas and Acinetobacter were found to be dominant potential spoilers at all temperatures.

Preliminary studies on growth and survival of Penaeus japonicus postlarvae fed with Tapes and commercial formula feeds

Growth and survival of P. japonicus postlarvae was studied using Tapes philippinarum and commercial formula feeds. After a 28-day feeding period, the highest survival rate of 100% was obtained in prawns receiving Diet-B, followed by those on Tapes Kyowa Hakko shrimp meal with survival rates of 80 and 76.7%, respectively. The lowest survival rate of 48.3% was obtained among postlarvae fed with squid meal. In this batch cannibalism was observed which resulted in low survival. Growth was highest in the postlarvae fed with Kyowa Hakko and mysid feeds. Diet-B gave a slightly lower weight increase but gave similar gain in length. The composition of the artificial diet, Diet-B, and growth and survival rates are tabulated.

Viability of Penaeus monodon eggs after simulated transport conditions

P. monodon spawners, transported from maturation pens suffer from stress which in turn may lead to lowered spawning rate or fertility. Spawning the females in the maturation site and transporting the eggs to the hatchery site is being considered as an alternative. Egg transport costs may be reduced to a minimum by using eggs from ablated spawners, transported at high density with no aeration. Experiments on higher egg densities as well as on transport of nauplii should, however, be undertaken.

Isolation and culture in artificial media of Lagenidium from Penaeus monodon larvae

Fungal infection of P. monodon larvae is a problem in hatchery operations. The fungus, which attacks the nauplius to postlarval stages and causes up to 100% mortality, has been tentatively identified as belonging to the genus Lagenidium . This pathogenic organism has recently been isolated and cultured. A description is given of the fungus, and features of its biology and pathology are discussed.

The food and feeding habit of Penaeus monodon Fabricius collected from Makato River, Aklan, Philippines

The food of Penaeus monodon collected from Makato R., from Sept 1977 to Jan 1978 is described with preliminary observations on its feeding habit and rate of foregut clearance. Feeding behaviour appears to be associated with the tidal phase. Foregut clearance rate is rapid, with 95% of food transported from the foregut 4 h after feeding. Frequency of occurrence and proportion of total food of various foregut contents are shown, as are dry weight, percentage mineral, organic and crude protein nitrogen from individual and pooled samples of gut contents, and foregut index in P. monodon collected during different phases of one tidal cycle.

Growth and survival of Penaeus monodon postlarvae fed shrimp head meal and fish meal as primary animal source of protein

Although shrimp head meal alone does not provide for good growth and survival, fish meal can provide high survival rate. The addition of shrimp head improves this diet. It is suggested that cholesterol present in shrimp could have caused this difference. Composition of the test diets is tabulated, as are proximate chemical analysis of the diets, and the mean initial weights, final weights, weight gains, survival rate, feed consumed, protein consumed, of Penaeus monodon postlarvae, feed conversion and protein efficiency ratio.

A preliminary study on the evaluation of casein, shrimp meal, squid meal and spirulina as protein sources of Penaeus monodon (Fabricius) postlarvae

P. monodon postlarvae were fed with fresh brown mussel (Modiolus metcalfei ) meat, and artificial diets containing casein, shrimp (Metapenaeus ensis ) meal, squid (Loligo ) meal, and Spirulina as protein sources at a rate of 20% of their biomass per day for a period of 10 days. No statistical difference was found among the weight gains of shrimp fed on various experimental diets. However, shrimp fed squid meal diet had highest weight gain followed by shrimp meal, fresh brown mussel meat, casein and Spirulina . Shrimp fed squid meal diet had a significantly better feed conversion and those receiving other experimental diets. Poorest fed conversion was observed in shrimp fed Spirulina . The protein efficiency ratio was statistically highest for the squid meal diet, with the lowest value again for Spirulina diets. Survival rate was significantly highest for shrimp fed the shrimp meal diet. No statistical differences were found among shrimp fed other experimental diets. Appropriate data are tabulated.

Relationship between diet composition and growth rate of the zoeal and mysis stages of Penaeus japonicus Bate

Diets containing Chaetoceros gracilis plus Artemia nauplii artificially prepared diet, Diet-B, and two commercial feeds Tapes and mysid meals, were fed to larvae of P. japonicus. Highest survival rate was obtained when larvae were fed with Diet-B. The results show that the early larval stages of P. japonicus can be reared on artificially prepared diets. Since the chemical composition of the diet is known, it can be used as supplemental data for larval feeding development and nutritional requirement studies for the early larval stages of Penaeus japonicus and/or other penaeids. Information is tabulated on feeds and feeding rates used, composition of the artificial diet, fatty acid composition of lipids of the different diets, and of the sterols of the different diets.

Toxicity of malachite green to the larvae of Penaeus monodon Fabricius

A study was undertaken examining the effect of malachite green on the development and survival of the zoeae, mysis and post-larvae of Penaeus monodon. Sensitivity varied with the different larval stages; the zoeae appeared to be the least tolerant. The prophylactic potentials of malachite green in the control of Lagenidiumand Zoothamnium infesting P. monodon larvae are considered briefly. Toxicity risks may be reduced by application between ecdyses or by the removal of the dye by filtration through activated carbon.