B.J Crear

Growth of juvenile southern rock lobsters, Jasus edwardsii, is influenced by diet and temperature, whilst survival is influenced by diet and tank environment

Abstract The growth and survival of juvenile (2–15 g) southern rock lobsters (Jasus edwardsii) were examined under various culture regimes. In Experiment 1, lobsters held at ambient (13–18°C) or 18°C were fed either fresh mussels, a commercial prawn diet or a moist diet. Growth (specific growth rate (SGR)=1.2–1.32% BW day−1), survival (98%) and food conversion ratios (FCR=1.26–1.29) were significantly better (P 0.05), when the lobsters were fed mussels. There was a significant interaction (P 0.05). The high acceptance and good consumption rate of formulated diets is a positive first step in the development of commercial diets for southern rock lobsters. In Experiment 2, lobsters held at ambient (13–18°C) or 18°C were maintained in tanks containing hides, substrates or neither. Hides increased survival (98%, cf. 60–75%) (P>0.05), although they did not increase growth (P>0.05) compared to tanks without hides. The provision of a substrate to aid the lobsters in the moulting process did not prevent cannibalism. Lobsters grew significantly faster (P

Biochemical composition during growth and starvation of early larval stages of cultured spiny lobster, Jasus edwardsii , phyllosoma

We examined biochemical changes accompanying feeding and starvation from hatch to Stage VI (day 74 after hatch) in spiny lobster, Jasus edwardsii, phyllosoma larvae. Larval dry weights (dw) increased 17-fold from hatch (80+/-1 microg) to Stage VI (1415+/-44 microg). Larvae starved for 6-11 days at Stages II, IV and VI were 14-40% lighter than their fed counterparts fed enriched Artemia. The increases and losses in total dry weight during feeding and starvation were associated with changes in the content of protein (constituting 31.4-41.7% of dw) and carbohydrate (constituting 2.6-5.3% of dw), while larger changes in lipid content indicated its greater importance as an energy substrate. Lipid content increased from 7.9% of dw at hatch to its highest of 12.5% at Stage IV, but declined by 50% or more during starvation. This suggests that protein, carbohydrate and lipid are all important energy stores, although lipids are catabolized at a greater rate during food deprivation. The principal lipid class was polar lipid (PL; 79-92% of total lipid), followed by sterol (ST; 6-20%), with triacylglycerol and other lipid classes at <2%. PL were catabolized and ST were conserved during starvation. Changes in the fatty acid (FA) profile had mostly occurred before the first moult at day 8 after hatch, with gradual changes thereafter to Stage VI, reflecting their abundance in the Artemia diet. There was some conservation of the major essential FAs, 20:4n-6, 20:5n-3, 22:6n-3, and the FA profile showed large gains in the C(18) polyunsaturated FA, 18:1n-9, 18:2n-6. Ascorbic acid content increased 10-fold from hatch to the end of Stage I (36 and 333 microgg(-1) dw, respectively), while the content at the end of Stage II was higher in fed than that in starved larvae (439 and 174 microgg(-1) dw, respectively). Our study will assist in the development of alternatives to nutritionally incomplete diets, such as live ongrown Artemia, to meet the requirements of phyllosoma in culture.

Optimal dietary protein level for juvenile southern rock lobster, Jasus edwardsii, at two lipid levels

This study determined the effect on growth efficiency, nutrient retention and apparent digestibility of varying dietary protein concentration and protein/energy ratio for juvenile southern rock lobster, Jasus edwardsii. Isoenergetic diets were formulated at six crude protein levels (5% increments between 24% and 50%) and at each of two lipid levels (5% and 9%). Duplicate groups of 10 lobsters (initial weight mean 3.58 SE 0.86 g) were held in 50-l tanks, in a recirculating seawater system at 18 degrees Celsius and fed to 95% satiation over a 12-week growth trial. There were significant ( P < 0.05) differences in apparent crude protein digestibility (76.4-83.2%), but no difference in dry matter (mean 59.1 SE 0.8%) or energy digestibility (mean 77.7 SE 0.8%). Survival, feed intake, digestive gland index, protein efficiency ratio, energy efficiency ratio and whole-body composition were not significantly affected by dietary treatment. The relationship between nutrient intake and weight gain indicated optimal dietary digestible crude protein (DCP) levels of 29% and 31% when lobsters were fed diets containing 5% and 9% lipid, respectively. For the two lipid levels studied, the optimal dietary protein/energy requirement was similar for maximum weight gain (29 gDCP/ MJ DE) and feed conversion ratio (FCR, 30 gDCP/MJ DE).

Feed availability and its relationship to survival, growth, dominance and the agonistic behaviour of the southern rock lobster, Jasus edwardsii in captivity.

Abstract The effect of feed availability (ration level and feeding frequency) on the culture performance of the juvenile (5–22 g) southern rock lobster Jasus edwardsii was examined to determine whether multiple daily feeding of a formulated feed would stimulate growth. Furthermore, the relationships between feed availability, agonistic behaviour, dominance, growth and survival were examined. A total of 252 lobsters (mean weight 5.26 g) were stocked into 28 black 52-l tanks at a density of nine lobsters per tank (42 m −2 ) and maintained at a temperature of 18.8 °C in a recirculating seawater system for 119 days. Lobsters were fed with high (4% BW day −1 ) or low (0.5% BW day −1 ) rations divided between one, two or four meals per day. These regimes were compared to a regime of fresh mussels ( Mytilus edulis ) fed to excess once per day. Feeding lobsters with a high-ration level, 4 day −1 , made no significant ( P >0.05) improvements in specific growth rate (SGR) (0.77–0.82% BW day −1 ), survival (75–84%) or biomass yields (96–102 g) compared to feeding 1 or 2 day −1 . Low-ration-fed lobsters had a higher final mean weight (17.5–20.9 g) compared to high-ration lobsters (13.4–14.3 g), however, survival of lobsters that were fed with low ration of 4 day −1 (41%) was significantly ( P P Lobsters were size-ranked (g) to determine the effects of feed competition on the growth and survival of individuals of different rank. The ability and/or motivation of the largest lobsters to maintain their size status increased as feed availability decreased, suggesting that feed restrictions increased the strength of dominance. Size-ranking also demonstrated that small lobsters were more vulnerable to being cannibalised, especially when the feed-ration level was low. Feed competition was consistent with the concept of economic defensibility, predicting that levels of agonistic behaviour are highest when a low ration was patterned into smaller, more easily defended meals (low-ration fed, 4 day −1 ). In contrast, feed competition and agonistic behaviour were rarely observed when feed was freely available (high-ration fed, 4 day −1 ). The high levels of cannibalism of small size-ranked lobsters meant that assessing growth depensation was not a useful approach to the evaluation of the relationships between competition and growth in groups. The implications for J. edwardsii culture are that feeding high-ration levels of formulated feeds, more than once daily, reduces feed competition and incidence of agonistic behaviour. However, there appear to have few benefits in terms of growth or survival. The recommendation from this study is to feed lobsters once daily to excess after dusk.

The effect of temperature on survival, growth, feeding and metabolic activity of the southern rock lobster, Jasus edwardsii.

This study investigated the effect of temperature (18, 20, 22 and 24°C) on growth, feeding and metabolism of post-puerulus lobsters as part of a larger study of the culture potential of farming the southern rock lobster, Jasus edwardsii. There was no significant difference (P>0.05) in the specific growth rates (SGR) at 18, 20 or 22°C; however, growth decreased significantly (P 0.05) in survival at 18, 20 or 22°C. The response of feed conversion ratio (FCR) to temperature was described by a quadratic regression (FCR=0.011T2−0.434T+5.231, r2=0.995), which suggested that the optimum temperature for feed conversion was 19.3°C. Oxygen consumption rates (MO2) increased with increasing temperatures between 18°C and 22°C and declined at 24°C; whilst total ammonia nitrogen (TAN) excretion increased with increasing temperature. The relationships were described by regression equations: MO2=−0.044T2+1.91T−18.553 (r2=1.0); TAN=0.127T−1.174 (r2=0.91). A temperature of 24°C appears to be above the upper thermal tolerance of juvenile J. edwardsii. Lobsters held at this temperature showed reduced survival (compared to those at 18°C), reduced growth (compared to those at 22°C) and appeared to be suffering from respiratory stress (moult-related mortalities, low Q10 between 22°C and 24°C). Overall, the results indicate that juvenile J. edwardsii can be cultured at 22°C without adversely affecting their growth, survival or feed efficiency with optimal temperature range between 19 and 21°C.

Dietary carbohydrate/lipid ratios and nutritional condition in juvenile southern rock lobster, Jasus edwardsii

Abstract The availability of formulated diets is considered economically imperative if rock lobster aquaculture, based on the collection and ongrowing of puerulus, is to progress. Central to the development of diets is an understanding of the nutritional requirements of the species. This study determined the effect of different dietary carbohydrate/lipid ratios (17:1, 5:1, 2:1, 0.8:1) on the growth and nutritional condition of juvenile southern rock lobsters, Jasus edwardsii, by measuring standard growth parameters, proximate composition of the whole body and digestive gland, and from a histological investigation of the digestive gland. Four replicate groups of eight lobsters (initial weight 5.08±0.98 g (mean±S.D.)) per diet treatment were held in 50 l tanks, in a recirculating system at 18 °C for 84 days. Maximum growth and the highest levels of lipid and dry matter in digestive glands and whole bodies was found in lobsters fed a diet containing 27% carbohydrate and 13.5% lipid (2:1 ratio) suggesting that of the four experimental diets, this diet provided the best balance of lipid and carbohydrate. Digestive gland histology supported this conclusion and lobsters fed low carbohydrate, high lipid diets were in the best nutritional condition, with high lipid accumulation, and structurally sound epithelial cells. Digestive gland epithelial cells of lobsters fed the high carbohydrate, low lipid diets were compressed, of inconsistent shape and size, with low lipid accumulation. Histology is therefore seen as a feasible method, in addition to growth and proximate composition data, to further examine the effect of diets in nutritional studies of crustaceans.

The effect of extrinsic and intrinsic factors on oxygen consumption by the southern rock lobster, Jasus edwardsii.

The oxygen consumption rate of the southern rock lobster, Jasus edwardsii, was evaluated in response to body weight, temperature, activity, handling, diurnal rhythm, feeding and oxygen saturation level. There was a positive relationship between standard oxygen consumption (M(O(2))) and both body weight and water temperature. The relationship between total oxygen consumption and wet whole body weight was described by the equation: LogM(O(2))=0.595log W-0.396 (r(2)=0.83). The relationship between weight-specific oxygen consumption and temperature was described by the equation: LogM(O(2))=0.047T-2.25 (r(2)=0.94). Activity had a significant influence on the oxygen consumption rate, causing a three-fold increase above the standard rate at the temperature of acclimation (13 degrees C). However, at temperatures approaching the upper and lower extremes, lobsters had a decreased ability to increase their oxygen consumption rates during activity. Lobsters took 4.5-5 h to return to standard oxygen consumption rates after a period of emersion and handling. A strong diurnal rhythm to oxygen consumption was recorded. J. edwardsii displayed a classic postprandial increase in oxygen consumption. A peak (1.72 times standard M(O(2))) occurred 10-13 h after feeding with an increase above standard M(O(2)) being maintained for 42 h. In its rested state J. edwardsii was an oxygen regulator down to a critical oxygen tension of 58 Torr, whilst activity resulted in the critical oxygen tension increasing to 93 Torr.

Diet immersion time: effects on growth, survival and feeding behaviour of juvenile southern rock lobster, Jasus edwardsii

Abstract The effect of water immersion time of a formulated shrimp diet on growth, survival, food conversion and carapace colour of juvenile southern rock lobster, Jasus edwardsii , was determined during a 16 week growth trial. Lobsters were fed one of five diets: pre-soaked shrimp diet (0.5, 2, 4 and 8 h) or non-soaked shrimp diet (0 h). Despite a significant loss in dry matter, protein, ash and astaxanthin from the diet as a result of pre-soaking, there was no effect on the growth, survival, food conversion or carapace colour of lobsters. Feeding behaviour of juvenile J. edwardsii was assessed using glycine, taurine and betaine, previously identified as strong chemoattractants to other crustaceans. Quantification of the antennular grooming frequency (AGF) was identified as the best method of assessing chemoattractant detection in J. edwardsii . The highest rate of AGF was observed in response to glycine at concentrations of 10 −4 to 10 −6 mol l −1 . AGF was subsequently used to assess the excitatory capacity of shrimp diet extract and fresh mussel ( Mytilus edulis ) extract. Two separate experiments were performed to determine the influence of water immersion on the excitatory capacity (ability to detect the source-(AGF)) and the attractability (capacity to attract to the source-(foraging preference)) of the shrimp diet in comparison to that of fresh mussel flesh. The excitatory capacity of the non-soaked shrimp diet, soaked shrimp diet and fresh mussel extracts were similar. However, the attractability of the non-soaked shrimp diet was greater than soaked shrimp diet and mussel flesh. Lobsters are capable of detecting the shrimp diet regardless of prolonged exposure to water; however, they will selectively move towards a “fresh” rather than a “stale” diet. The results of this study show that the loss of chemoattractants and nutrients from a shrimp diet, caused by leaching, had little impact on the culture performance of J. edwardsii . Thus, even though some lobsters have a slow feeding response and may not feed for several hours after being fed, the dispensation of feed only once per day will not impact on culture performance. However, the influence of leaching on the performance of diets specifically developed for J. edwardsii will need to be re-assessed.

Bacterial decontamination of on-grown Artemia

The bacterial load of on-grown Artemia was manipulated using a variety of commercially available enrichment DHA boosters, selected algal species (Skeletonema costatum; Nannochloropsis oculata; Tetraselmis suecica; Chaetoceros muelleri), and ozone to decontaminate enteric and external surfaces, respectively. Enrichment in C. muelleri over a 6-h period, with an additional algal exchange mid-enrichment, provided the most efficient method for enteric decontamination as measured by total viable counts. Direct exposure to ozone at 4 ppm for 5 min provided further bacterial reduction, resulting in a combined bacterial load reduction of 99.5% without compromising Artemia viability. The commercial enrichment A1 DHA Selcok (TM), containing antibacterial compounds, provides an alternative to algal-based enrichments, however, its decontaminating properties were inferior. Fluorescence in situ hybridisation (FISH) was used on occasions to verify total bacterial abundance estimates obtained by standard plating procedures. In all except one case, Johnsons Marine Agar (JMA) provided results comparable to direct counts by FISH. This indicates that the bacterial community present in on-grown Artemia cultures is dominated by several fast-growing r-strategists amenable to culture on conventional plates. Underestimation of bacterial abundance using marine agar was therefore unlikely.

Potential use of radiography for measuring feed intake of southern rock lobster (Jasus edwardsii)

The potential of using radiography for measuring feed intake in southern rock lobster Jasus edwardsii (Hutton) was evaluated. Lobsters (14–40 g) readily consumed feeds containing radio-opaque marker (400—450 μm). Marker particles were clearly identified in the stomach 90 min after feeding enabling feed intake to be estimated. Initially low estimates (15±17%; mean±S.D.) of feed intake (expressed as percentage of gravimetric estimates) were recorded due to loss of markers prior to ingestion. Radiographic estimates improved (100±23%; mean±S.D.) when changes to pellet diameter (1.5 mm), moisture content (11%) and binding agent (alginate) were made. Thus, estimates were dependent on pellet diameter and resistance to fragmentation prior to ingestion. To test for the presence of feeding hierarchies in groups of lobsters an experiment was conducted to examine the effect of ration level (high ration: 2.0% BW day−1 and low ration: 0.2% BW day−1) on intra-individual (measured as coefficient of variation for feed intake: CVC) and inter-individual variation (measured as mean share of the group meal: MSM%). There was a significant (P<0.05) negative correlation between CVC and MSM% for the low ration treatments which indicated that small lobsters (CVC=114±19% and MSM%=22±10%: mean±S.D.) were less successful than large lobsters (CVC 44±11% and MSM%=41±13%: mean±S.D.) at obtaining feed. This may be indicative of the formation of feeding hierarchies.