Phyllosoma larvae of the southern rock lobster, Jasus edwardsii, were cultured from egg to juvenile. For larvae reared from hatch to Stage III, survival was highest and bacterial contamination was lowest in seawater ozonated at low and moderate levels (400 and 500 mV oxidation-reduction potential, ORP). By contrast, at high ozonation (600 mV), all larvae suffered deformities at the moult to Stage II and terminally starved, while in unozonated water (about 300 mV), all larvae died at Stage III probably as a consequence of Vibrio bacteria proliferation. In a second experiment between Stages VI to VIII, larval survival was highest in ozonated water that had been filtered through activated charcoal and coral sand, compared to ozonated water with no filtration or filtered only through activated charcoal. Ozonated water with the combined filtration was used subsequently but there were ongoing deformities, so the level was progressively reduced from 400 mV at Stage VIII to 330 mV at Stage X, at which time ozonation was discontinued. Larvae were then cultured in unozonated water to metamorphosis of eight pueruli at 377 to 437 days after hatch, of which two survived to juvenile. Ozonation was thus effective up to Stage IX in improving culture water to minimise bacterial disease without problems of larval deformities. 相似文献
This paper presents the effects of feeding level, feeding frequency, salinity of water, kind and particle size of diets, and stocking density on the growth of milkfish (Chanos chanos Forskal) fingerlings which were reared with artificial diets in laboratory tanks. Experimental groups were designed using orthogonal array L8, and the results were evaluated statistically. Growth of the milkfish fingerlings varied markedly with the kind of diets used and feeding level. The feeding frequency and particle size of the diets also affected growth of the fingerlings significantly, but the salinity of the water did not. The weight gain of the fingerlings did not vary with the stocking densities significantly, whereas the increase (%) in body length was greater at a lower stocking density. The milkfish fingerlings showed the best growth in terms of both weight gain and increase in body length when reared on a purified diet containing 35% casein and 15% gelatin as protein sources under the following conditions: feeding level, 30–35% of body weight; feeding frequency, twice a day; particle size of diets, 125–250 μm diameter; and stocking density, tank. The means and confidence limits of the weight gain (%) and increase (%) in body length of milkfish fingerlings under the best conditions adopted were estimated to be 360 ± 63.7 and 62.1 ± 10.6, respectively. 相似文献
The relative growth and production of estuary grouper, Epinephelus salmoides, in response to seven combinations of hiding space and stocking density were studied in floating net cages. Used car tyres were suspended in the net cages to provide hiding space for the fish. The seven combinations of hiding space and stocking density were as follows: Provision of hiding space in the net cages was found to permit an increase in the stocking density from the optimal rate of 60 fish/m3 (without artificial hides) to 156 fish/m3. The net production was found to increase from 8.5 kg/m3 to 19.5 kg/m3 after 3 months. Growth in terms of weight gain per fish, survival rate and food conversion ratio at stocking rates below 156 fish/m3 with hiding space between 116 and 222 cm3/fish was comparable to that observed at the optimal stocking density without hiding space (60 fish/m3). The growth of fish stocked at 180–204 fish/m3 with hiding space of 272–289 cm3/fish, respectively, was found to be significantly depressed. Thus, with the provision of hiding space of 251 cm3/fish, the stocking density could be increased to as high as 156 fish/m3 and the production of fish could be increased by 230% over that at the usual optimal stocking rate of 60 fish/m3 without artificial hides. 相似文献
Methods for induced spawning and artificial incubation of Tilapia nilotica and T. aurea are described. These methods were required for the production, in aquaria, of F1 hybrids between the two species. Spawning families were established in long aquaria from which sexually ripe individuals were selected for stripping by their “on heat” display coloration. Injections of pituitary hormones were not required. The fertilized eggs were incubated in a low speed “shaker”. At correct temperatures Tilapia fry may be produced by this artificial process all year round. 相似文献
The numbers of eggs spawned, attached, and carried through to hatching were examined in three groups of captive lobsters (Homarus americanus). Wild born/lab spawned H. americanus, lab born/lab spawned H. americanus, and hybrids of H. americanus ♂ × H. gammarus ♀ spawned 8800–11500 eggs per female (weight range 336–945 g). Hybrid females attached 77% of all spawned eggs. Purebred females attached either most eggs of a spawn or fewer than 10%. In some instances where attachment was poor, females were known to be virgins or had been mated to a sterile hybrid male. Unfertilized eggs could attach, but the percentage which did was low. Some wild born/lab spawned H. americanus carried portions of their clutches through until hatching; however, many purebreds and all hybrids dropped their clutches before hatching. Possible factors which cause eggs to drop prematurely are discussed. 相似文献
The cultivation of Gracilaria is described, costs and returns of the operation are analyzed, and the market demand is evaluated. Gracilaria culture is a labor-intensive operation. However, annual productivity and profit are high. The increasing demand and rising price of raw Gracilaria, and agar derived from it, are likely to encourage Gracilaria cultivation not only in Taiwan but also in other developing countries with sites suitable for its cultivation. 相似文献
Dover sole (Solea solea (L.)) of 1.3–2.8 cm in length (18–190 mg) were weaned from live Artemia salina nauplii to prepared diest ranging from extruded pastes to dry powders. A variety of techniques was used, including the abrupt change to the new diet, the use of a series of intermediary diets, and the addition of limited quantities of live Artemia during the early stages of weaning. Survival rates of 41–76% were achieved and growth averaged from 0.04 to 0.33 mm/day. 相似文献
The author discusses the recent development and present status of a Eucheuma seaweed farming industry in The Philippines. He describes Eucheuma cultivation methods, assesses farm productivity, and considers the economics of Eucheuma farming by Filipino families. The author concludes with a discussion of current problems and an evaluation of future prospects for the industry. 相似文献
The culture of seahorses has usually relied on cultured live foods or collected wild live foods as feed. This can be expensive in the case of culturing live foods and unreliable in the case of harvesting wild live foods. This investigation examined whether juvenile Hippocampus abdominalis from 0 to 2 months of age could be experimentally weaned onto frozen (Cyclop-eeze copepods) and artificial (Golden Pearls) food over 30-day periods with Artemia as a live food control, with 0-, 5-, 10-, and 20-day mixed feeding periods. Newborn juveniles could not be weaned onto Golden Pearls, with almost complete mortality. One-month-old juveniles could be weaned onto Cyclop-eeze with no effect on survival but with lower growth. One-month-old juveniles could be weaned onto Golden Pearls but with lower survival and lower growth. Two-month-old juveniles could be weaned onto Cyclop-eeze but with lower survival and lower growth. Two-month-old juveniles could be weaned onto Golden Pearls with no effect on survival but with lower growth. In all experiments, the rate of feeding strikes on Cyclop-eeze and Golden Pearls was lower than that on Artemia (e.g. range of mean 0.16–0.97 vs. 2.2–2.76 feeding strikes/min), both when Artemia were the sole food presented and when Artemia were cofed with the nonlive foods. However, mixed feeding Artemia with nonlive foods did appear to increase the rate of feeding strikes on nonlive foods. These results indicate the potential for incorporating more cost effective and reliable nonlive foods into seahorse culture. 相似文献
The factors affecting production of estuary grouper, Epinephelus salmoides, in floating net cages are discussed. The concept of economic production in cage culture is outlined. Economic production of estuary grouper could be achieved by providing a suitable culture site with good water quality; ensuring proper farm management and regular maintenance of cages; preventing disease and ensuring efficient treatment; providing optimum stocking density, a balanced diet, optimal feeding frequency; manipulating fish behaviour by providing artificial hides; and manipulating physiological characteristics, e.g. by the use of growth promoters.The paper futher describes environmental parameters, such as dissolved oxygen content, water temperature, salinity, water current, bacteria count, pH, and bottom sediments, as important factors in site selection. Their effects on the growth and production of fish are discussed and their optimal levels determined. The problems involving management and maintenance of the farm are also outlined. The main problem in cage culture is fouling which demands considerable labour and money for cage maintenance. Other problems such as predators, poaching, and cannibalism are discussed at length. It is suggested that by manipulation of stocking density, production could be increased. The optimal stocking rate was found to be 60 fish/m3 which gives a high yield of marketable fish. Stocking could be further intensified by providing artificial hides using used car tyres. The net production could be increased by 230% if hiding space of 251 cm3 per fish was provided and the stocking density increased to 156 fish/m3. Although formulated feeds enhanced growth by 27.1% over that of groupers fed on trash fish, the production cost was much higher, rendering the use of formulated feeds alone uneconomical for commercial fish culture. Growth promoters such as 17α-methyltestosterone and nitrovin have been found to promote growth of young estuary grouper by 43.4 and 62.8%, respectively.Using various combinations of culture techniques, it was shown that net production could be increased from 23.76 kg/m3 using conventional culture methods to 136.75 kg/m3 with a combination of hiding space, heavy stocking, appropriate feeding frequency and formulated feeds incorporating growth promoters. The production time was also shortened considerably from 6 months to 2.7 months.Cost-benefit analysis of the eight culture techniques tested indicated that the production cost could be reduced from US$2.00/kg with conventional methods to as low as US$1.28/kg using a sophisticated method. However, based on current market proces, the conventional culture technique was still economically feasible, as the net income over total capital costs was 33.3%. Improvements of the conventional culture technique will increase the ratio of net income over total capital costs by 1–3 times. 相似文献
Experiments were conducted to control reproduction of Tilapia nilotica using cage culture compared with growth and reproduction in ponds. Three rearing densities (5, 15, and 45 fish per cage), and three kinds of aquatic plant (Hydrilla sp., Lemna sp., and Chara sp.) were used as feed.Results of the study showed that Tilapia reproduced in both cages and ponds; however, the intensity of reproduction was low. Growth rates of fish reared in cages were higher than those of fish reared in ponds.Lemna sp. as feed gave the best results in terms of growth rate and protein content of fish flesh. There was no interaction between feed and rearing density. 相似文献
The preparation of microencapsulated diets for rearing the larvae of Penaeus japonicus is described. Once the correct microcapsule size and feeding concentration had been determined, experiments showed that survival rates of 50% to post-larva were possible. Comparative experiments using artificial diets in the form of free particulates indicate that survival rates may be even higher (66–68%) on these diets providing precautions are taken to avoid bacterial blooms. Further investigations revealed that microencapsulated semi-defined diets may be used to determine the nutritional requirements of Penaeus larvae. 相似文献
