Live Prawns Research Articles

The effect of choice of targeted market, production scale, and land tenure on the economics of integrated tilapia-prawn production

Integrated aquaculture systems have the potential to enhance the environmental sustainability of aquaculture production, if economically feasible. Data from integrated tilapia-prawn production trials were used to develop economic-engineering enterprise budgets for ponds with and without substrate that targeted two different types of markets, using two production scales and two forms of land tenure. Inclusion of substrate increased investment and fixed costs and decreased net returns. Recreational markets (live tilapia for fee fishing and live prawns as bait) were profitable, but sales to supermarkets were not. Production scale and land tenure affected economic outcomes with increased pond size and leasing ponds demonstrating greater profitability. Results provide evidence of the need to carefully evaluate economic trade-offs associated with varying commercial-scale applications to increase the likelihood of adoption of new technologies.

Sensitivity of the freshwater prawn, Macrobrachium lanchesteri (Crustacea: Decapoda), to heavy metals

Adult Macrobrachium lanchesteri were exposed for a 4-day period in laboratory conditions to a range of copper (Cu), cadmium (Cd), zinc (Zn) and lead (Pb) concentrations. Mortality was assessed and median lethal times (LT₅₀) and concentrations (LC₅₀) were calculated. At the end of the 4-day period, live prawns were used to determine bioconcentration of the metals. LT₅₀ and LC₅₀ increased with the decrease in mean exposure concentrations and times, respectively, for all metals. LC₅₀s for 96 hours for Cu, Cd, Zn and Pb were 32.3, 7.0, 525.1 and 35.0 µg/L, respectively. Cu, Cd, Zn and Pb bioconcentration in M. lanchesteri increases with exposure to increasing concentrations and Cd was the most toxic to M. lanchesteri, followed by Pb, Cu and Zn. Comparison of LC₅₀ values for metals for this species with those for other freshwater crustacean organisms reveals that M. lanchesteri is equally or more sensitive to heavy metals than most other tested crustaceans.

The Impact of Electronic Clock Auction Systems on Shellfish Prices: Econometric Evidence from a Structural Change Model

AbstractEconomic theory suggests that different auction systems may lead to different price equilibria under specific conditions. By changing the trading rules, the introduction of electronic clock auction systems (ECAS) on primary fish markets is likely to modify the price formation process. A relationship between the prices of live prawns (Nephrops norvegicus) in two French ports where different ECAS have been successively introduced is estimated through two univariate models and a vector autoregressive model applied to stationary weekly data series. Using a recent multiple break searching procedure (Econometrica, Vol. 66, 1998, 47; Journal of Applied Econometrics, Vol. 18, 2003, 1; Econometrics Journal, Vol. 6, 2003, 72), a single structural change matching the date of implementation is discovered in the two ports and shows a different impact partly explained by the type of auction system in force. The introduction of the Euro in January 2002 also appeared to play an influential role in the adoption of electronic clock auction markets.

Energy budget of juvenile fat snook Centropomus parallelus fed live food

The fat snook Centropomus parallelus is a tropical estuarine species with importance for recreational and commercial fisheries and further aquaculture potential. Considering ingested energy ( C) is channeled into growth ( P), metabolic expenditure ( R), excretion ( U) and feces ( F), a balanced energy budget was established for isolated and grouped juvenile C. parallelus (5.18 to 10.25 g wet mass) by experimental quantification of each of these parameters. Fish were fed live prawn ( Macrobrachium sp.) at 25 °C and 20‰ for 19 days and daily energy budgets could be calculated. Energy content of food (live prawn), fish whole body and feces were 17.7, 14.5 and 6.1 KJ g − 1 dry mass (DW), respectively. Mass-specific rates of oxygen consumption and ammonia-N excretion were 0.271 and 0.0082 mg of O 2 or NH 3–N g − 1 wet mass (WW) h − 1 , respectively, resulting in O : N = 23.4. Daily ingestion ( C) was dependent on the amount of food offered and ranged between 4.9% to 7.4% of initial wet weight. Growth ( P) was positively correlated with initial mass varying from 0.008 to 0.104 g day − 1 . Feces release also correlated to fish mass and averaged 9.53 mg dry mass day − 1 . The components of energy budget showed mean values of 2.39 ( C), 0.24 ( P), 1.96 ( R), 0.11 ( U) and 0.06 ( F) KJ ind − 1 day − 1 . As percentage of ingested energy, C. parallelus channeled 10% in growth ( P), 82% in metabolism ( R), 4.6% in excretion ( U) and 2.5% in feces ( F). Gross ( K 1) and net ( K 2) growth efficiencies were 9.2% and 9.9%, respectively. On the course of this period of juvenile development, K 1 and K 2 increased significantly. Partitioning of ingested energy in P, R, U and F was significantly different in individually and group maintained fish ( P < 0.05). Energy budget of C. parallelus fed a highly digestible diet (live prawn) revealed poor growth and growth efficiencies ( K 1 and K 2) possibly associated with an elevated metabolic demand and a high channeling of metabolized energy ( P + R) into metabolism ( R) in both isolated and grouped fish. Data can be applied to ecosystem modeling and may contribute to identify species potential to aquaculture.

The Effect of Biomass Density, Temperature, and Substrate on Transport Survival of Market-Size Freshwater Prawn, Macrobrachium rosenbergii

After harvest, adult prawn are often transported for sales to live markets, such as ethnic Asian outlets, in major urban centers. Poor survival during transportation has hindered development and expansion of these markets. Methodologies to increase survival during transport could contribute to industry viability. Three independent trials were conducted. In the first trial, three biomass densities (25, 50 and 100 g/L) were evaluated in 100-L, open plastic containers aerated with pure oxygen and compressed air. Water quality analyses were performed prior to stocking. After 24 hours in the model transport containers, water quality analysis was conducted and all prawn were removed, determined to be alive or dead, and each group weighed and counted. There was no significant difference (P > 0.05) for prawn survival (overall mean 98%) among the three densities. Concentrations of dissolved oxygen and nitrite were not effected by hauling density (P < 0.05). Total ammonia-nitrogen and un-ionized ammonia-nitrogen concentrations increased (P < 0.05) as biomass densities increased, though values remained within what are considered tolerable ranges. In the second trial, the effect of added substrate and temperature on transport survival was evaluated with prawns stocked at the high density (100 g/L). Two water temperatures (21°C and 26°C) with and without substrate were evaluated in a 2 × 2 factorial with three replicate, 100-L model transport containers per treatment combination (12 containers total). Factorial analysis indicated no significant statistical interaction (P > 0.05) between the presence of substrate and water temperature on any measured variable. The main effects of substrate and temperature were then analyzed separately. The presence or absence of substrate had no significant impact (P > 0.05) on prawn survival. However, temperature had a highly significantly impact (P < 0.01) on survival; prawn survival at 21°C averaged 97% compared to 24% at 26°C. The third trial was a commercial verification trial in which 500 kg of live prawn were transported to New York from Kentucky. These data indicate prawn can be successfully transported at 100 g/L for 24 hours when temperatures are maintained near 21°C. Adding substrate to the transport tank appears to provide no benefit.

Pressure immobilisation bandages in first‐aid treatment of jellyfish envenomation: current recommendations reconsidered

To evaluate whether applying pressure equivalent to that of pressure immobilisation bandages (PIB) causes release of additional venom from discharged jellyfish nematocysts. In-vitro experiment--the venom beads released from electrically activated Chiropsalmus sp. nematocysts were viewed under direct microscopy before and after applying 40 mmHg pressure (replicating the pressure of PIB); and saline washings of discharged nematocysts before and after applying pressure were tested for toxicity (time to ventricular standstill after injecting into live prawns). Applying 40 mmHg pressure caused the venom beads to visibly increase in size, consistent with pressure expressing further venom from the discharged nematocysts. First washings of the nematocyst shafts before compression produced ventricular standstill in prawns within 60 seconds (n=3); second washings did not produce standstill during 540 seconds of observation (n=3); and washings after applying 40 mmHg pressure showed a return of toxicity, with ventricular standstill in all prawns within 180 seconds (n=3). Discharged nematocysts are by no means empty and harmless. Applying pressure results in further release of nematocyst venom. The currently recommended practice of applying PIB in the initial treatment of patients stung by a jellyfish may exacerbate the envenomation, and thus should not be recommended.

Catch performance of small prawn pots in terms of selectivity and escape

The size distribution of entrapped prawns in a pot may be governed by the construction of the pot entrance. The selectivity of entrances was studied. To clarify how the pot entrance design affects the size distribution of entrapped prawns in a pot, a series of tests were carried out with live prawns in a tank. In each case, the variations in the mode of sizes could be explained satisfactorily by the differences in the diameter of the opening. The escapement ratio, a could be used as the principal index to evaluate the selectivity of the entrance. The results suggest that the pots with large openings accelerate the escape of the prawns.

おがくず詰め活きクルマエビにおける筋肉中のＡＴＰ関連物質および乳酸の量的変化

Changes in the levels of ATP-related compounds and lactic acid in the muscle of live prawn Penaeus japonicus kept in the sawdust at 15C° were investigated to find an index suitable for evalua-tion of parwn activity during the transportation in the sawdust. The concentration of ATP in the muscle markedly decreased after storage of 48h, resulting in a rapid increase in the AMP level. The level of lactic acid in the muscle also gradually increased during storage in the sawdust. The ratio of ATP to the ATP-related compounds (the total nu-cleotides) in the muscle which colsely related with the survival rate of prawn was found to be sui-table as a criterion to evaluate the activity of prawn during transportation in the sawdust. The levels of the ATP-related compounds in the muscle of prawn kept in the sawdust recovered to their original levels within 1h after they were returned to the sea.

Floating hatchery and net cage culture of Penaeus indicus in the Straits of Johore, Singapore

A simple floating hatchery system with partially submerged tanks (bags made of flexible, plastic-coated fabric) was used to rear the larvae of Penaeus indicus. A total of 1.96 million active nauplii were reared in 6000-l tanks at average densities of 67 nauplii and 42 nauplii/l of tank capacity. Development time from spawning to metamorphosis was 9 days and the average survival rate of nauplii to age PL6 was 49%. From age PL6, post-larvae were reared in nursery net cages (6 × 3 × 0.6 m) in the sea. At densities of 50 000–60 000 post-larvae/cage, the average survival rate from age PL6 to age PL20–22 was 78%; from age PL20–22 to age PL37–44 at densities of 25 000/cage it was 83%. One batch of juveniles was stocked in a prawn pond at age PL27 and another was stocked at high densities in two sizes of net cages at age PL37–50. The prawns grown in the pond reached a mean size of 9 g after 76 days (at age PL103). In large net cages (5 × 5 × 2.5 m) stocked at a density of 80/m 2, prawns reached a marketable size of 9.8 g after 113 days (at age PL157) with an average survival rate of 32%. Based on these results, the costs of producing post-larvae and juveniles using the floating hatchery and nursery net cage system and of producing live prawns of marketable size by net cage culture were calculated. Modifications in the net cage culture techniques employed are recommended to improve growth and survival rates and reduce production costs.