Biological study of red snapper, Lutjanus sanguineus

Among the red snappers caught by trawling in the South China Sea, L. sanguineus is the most important species, comprising more than 10% of the total catch. Although L. sanguineus is widely distributed in the South China Sea, its pattern of distribution seems to be rather patchy. However, they were most abundant at 35—80 m. water depth and inhabit muddy-sand areas especially where “Neptune’s cup” are abundant. Size frequency histograms indicate four to six size groups, with peaks of almost the same height. The growth rate of fish of 23 cm. was taken to be approximately 2 cm. per month. As no significant difference in length-weight relationship between male an female was observed, the following formula can be applied for both sexes. W = 7.64 x 10–5 L2.823 where, W = body weight (g). L = body length (mm). The number of ovarian eggs ranged from 69 to 260.104 and the regression between the number of eggs in thousand (N) and fish weight in gram (W) was N =0.4459W + 83.2. High values of gonadal index from March to November with a peak in April—June suggests a prolonged spawning season

Overview of penaeid shrimp culture in Asia

Marine shrimp farming is a century-old practice in some Asian countries. Past sluggish development of the industry is mainly due to the inadequacy of hatchery technology resulting in inconsistent and insufficient supply of shrimp fry hence offsetting large scale development of the industry. Recent success in hatchery techniques coupled with high market demand have generated world-wide interest in developing shrimp farms in Asia. This paper attempts to make an in-depth review of the various aspects confronting the development and expansion of the shrimp farming industry. The cultural significance of the various penaeid shrimps cultivated in Asia (Penaeus monodon, P. japonicus, P. indicus, P. merguiensis and P. orientalis) is critically reviewed in relation to other subtropical species such as P. stylirostris and P. van-namei successfully cultivated in South America. The major constraints confronting large scale cultivation of P. monodon and other commonly important species are discussed and research gaps outlined. Present status of hatchery techniques is discussed and the need for standardization of viable techniques for technology packaging and verification is highlighted to ensure reliable source of seed supply. The various problems in hatchery development, including development of artificial larval feeds, are emphasized. This paper attempts to compare the technological and financial inputs in high technology with traditional farming practices in the region. The grow-out technology in relation to farming intensity and level of investment are outlined with special reference to the socio-economic condition in Asia. The need to develop viable and appropriate shrimp farming technology within the technical and financial capabilities of the rural small shrimp growers is discussed

An incidence of swimbladder stress syndrome in hatchery-reared sea bass (Lates calcarifer) larvae

Contribution No. 166 from the SEAFDEC Aquaculture Department.This paper describes an incidence of swimbladder malfunction causing high positive buoyancy and mass mortality in 2-week-old sea bass (Lates calcarifer) larvae reared in an outdoor hatchery tank under conditions of high ambient temperature (26–32°C) and salinity (32–34‰), and a dense diatom bloom. The problem occurred soon after handling the larvae by seine and bucket, and seemed to have been a case of swimbladder stress syndrome (SBSS). The development of the swimbladder in sea bass larvae is briefly described

Intensification techniques in the extensive culture of Penaeus monodon

Traditional shrimp (Penaeus monodon) farming is characterized by low yields, 100-300 kg/ha/yr. To provide farmers with appropriate technology that can immediately improve pond yield with minimal investment, experiments were conducted in brackishwater earthen ponds in two phases. The first phase was to evaluate the optimum stocking density without transfer of stock during the culture period up to harvest time. In the second phase, the best stocking density in the first phase was selected to determine the effect of transfer to newly-prepared ponds at 45-day and 60-day intervals. In the first phase, the ponds were stocked with hatchery-bred fry at the stocking rates of 1, 2 and 4/m2 with no supplementary feeding for the first two months of culture. Feed was introduced after the second month at 6% body weight for the third month and at 4% body weight on the fourth. The yields after four months were 171 kg., 317 kg and 382 kg/ha/crop with survival rates of 85%, 83% and 74%, respectively. The stocking density of 2/m2 was selected for the second phase experiment. The yield was 422 kg, 525 kg and 372 kg/ha/crop at 45 days and 60 days transfer and nontransferred, respectively

Biology and culture of sea bass (Lates calcarifer)

Reprinted June 1989 as Aquaculture extension manual; no. 11.Information is presented regarding the biology and culture of Lates calcarifer in order to serve as a practical guide for extension workers and farmers. Hatchery design, seed production and hatchery techniques, culture of seabass and financial aspects of the seabass culture industry are described

An improved traditional shrimp culture technique for increasing pond yield

Reprinted June 1989 as Aquaculture Extention manual; no. 15.Details are given of the technology required for an improved method of extensive shrimp (Penaeus monodon) culture, describing the following: grow out facilities, seed supply, pond preparation and management, harvesting and yield. A financial analysis is also included

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

A prototype warm water shrimp hatchery

Reprinted June 1989 as Aquaculture Extention manual; no. 12.A description is given of the prototype warm water shrimp hatchery established and operated by SEAFDEC Aquaculture Department since 1982. Hatchery design, operation and management, larval rearing in small indoor tanks, larval rearing in large nursery tanks, routine hatchery management, harvesting and transportation and financial aspects are covered

Shrimp hatchery design, operation and management

Reprinted June 1989 as Aquaculture extension manual; no. 14.Details are given of factors to be taken into account for successful hatchery operation. The following aspects are covered: 1) site selection; 2) hatchery design and construction; 3) life cycle; 4) preparation of broodstock for spawning; 5) larval feed; 6) spawning, hatching and larval rearing facilities; 7) spawner selection and egg collection 8) nauplii hatching and transportation; 9) larval rearing; 10) routine hatching, management; 11) port-larvae nursery; and 12) larval harvesting and transportation