Growth and lipid composition of phyllosomata of the southern rock lobster, Jasus edwardsii, fed enriched Artemia

Newly hatched phyllosoma larvae of Jasus edwardsii were on‐grown to stage V. Using triacylglycerol‐rich marine oil nutrient sources and microalgae, Artemia were enriched with the major polyunsaturated fatty acids (PUFA) to ratios similar to that of wild‐caught phyllosomata. Artemia enriched by different methods were fed to cultured phyllosomata. At each stage animals were counted, measured and sampled for lipid analyses. Survival was highest from stages II to III (62–86%), with mean total survival at 3–12%. From stages I to V larvae increased in mass (0.2–2.2 mg) and total length (2.1–5.8 mm), and decreased in total lipid. The major lipid class in all phyllosomata was polar lipid, followed by sterol, with no triacylglycerol detected. The main fatty acids were 18:1(n‐9)c, 18:2(n‐6), 16:0, 18:0, eicosapentaenoic acid [EPA; 20:5(n‐3)], 18:1(n‐7)c, arachidonic acid [AA; 20:4(n‐6)] and docosahexaenoic acid [DHA; 22:6(n‐3)]. On‐grown phyllosomata had levels of AA and EPA similar to that of wild phyllosomata, but contained markedly lower levels of DHA. Strategies for enhancement of DHA levels will be needed for culture of rock lobster phyllosomata.     

Feeding juvenile Artemia enriched with ascorbic acid improves larval survival in the spiny lobster Jasus edwardsii

Newly hatched Jasus edwardsii phyllosoma were fed unenriched Artemia [endogenous ascorbic acid (AA) concentration of 166 μg g^?1 dry weight (dw)], Artemia supplemented with algae (AA concentration 594 μg g^?1 dw) or with ascorbyl‐2‐polyphosphate (A2P) (AA concentration 11 737 μg g^?1 dw) to examine possible benefits of AA enhancement on culture. Plain or algal‐enriched Artemia were fed continuously for 28 days in two treatments during the study. Four other treatments received A2P‐enriched Artemia on a progressive basis starting from the commencement of the trial (D‐0), the third (D‐3), sixth (D‐6) or ninth day (D‐9) of Stage I (14 days) and similarly during Stage II (14 days). Prior to the commencement of A2P supplementation, plain Artemia were supplied to these animals. By Stage III (28 days feeding), algal, D‐0 and D‐3 phyllosoma had attained the largest size. The uptake and retention of AA by Stage III phyllosoma appeared to be dose‐dependent with the highest concentration of AA incorporation evident in D‐0 phyllosoma (1816 μg g^?1 dw), while algal and plain phyllosoma contained the lowest concentrations (600 and 300 μg g^?1 dw, respectively). Survival at Stage III was highest in D‐0 phyllosoma (89%) and lowest in plain phyllosoma (51%). There was a positive relationship between phyllosoma AA concentration and larval survival (R² = 0.8328, P < 0.0001). D‐0 phyllosoma had the lowest stress index when subjected to an osmotic/temperature activity test, indicative of better survival in culture compared to plain, algal and D‐9 phyllosoma, which had consistently higher indices. A negative relationship existed between phyllosoma AA concentration and stress indices at Stage III (R² = 0.9263, P < 0.0001), suggesting that AA from the Artemia diet conferred stress resistance.     

Impact of wind stress anomalies on the seasonal pattern of southern rock lobster (Jasus edwardsii) settlement in South Australia

Quantified estimates of southern rock lobster (Jasus edwardii) puerulus settlement have been undertaken in the Southern Zone fishery of South Australia since the early 1990s. An analysis of mean monthly puerulus settlement indices from 1995 to 2007 in three monitoring sites revealed a strong seasonal correlation (r > 0.94 between sites) in settlement patterns. Settlement was highest during the winter months of June, July and August with peak settlement in all sites occurring in July. A reduced secondary settlement occurred during February and March. Seasonal trends were correlated with monthly wind stress and direction data in order to investigate possible environmental drivers of settlement. Using monthly averages of wind stress, it was hypothesized that strong along‐shore wind‐stress anomalies (ASWSA) prior to peak settlement would influence puerulus indices. Maximum ASWSA over the December–May period prior to maximum settlement was therefore examined. The results showed significant correlations (P < 0.1, r = 0.51–0.90) between wind stress and puerulus settlement in all but one site. We suggest that storm events, in combination with onshore surface drift during the period of settlement, are the principal physical oceanographic mechanisms influencing settlement patterns within the Southern Zone rock lobster fishery of South Australia.     

Effects of starvation and feeding on the fatty acid profiles of Stage I phyllosoma of the spiny lobster, Jasus edwardsii

Fatty acid analyses were conducted on newly hatched and 8‐day‐old‐starved and fed Stage I phyllosoma larvae of the spiny lobster, Jasus edwardsii. Fed animals were offered excess 1.5 mm juvenile Artemia (enriched using the alga Isochrysis galbana, Tahitian isolate, T. iso.). After 8 days, there were significant increases in larval dry weight and the proportion of lipid in fed phyllosoma, whereas these parameters decreased in starved phyllosoma. The abundance of the saturated fatty acids 16 : 0 and 18 : 0 increased in both starved and fed phyllosoma, whereas the main monounsaturated fatty acids 16 : 1n‐7, 18 : 1n‐9 and 18 : 1n‐7 increased with feeding but decreased with starvation. There were no significant differences in the relative proportions of the highly unsaturated fatty acids (HUFAs) arachidonic (AA, 20 : 4n‐6), eicosapentaenoic (EPA, 20 : 5n‐3) and docosahexanoic (DHA, 22 : 6n‐3) acids between newly hatched and starved animals, whereas quantitatively DHA decreased with starvation and feeding. The DHA/EPA ratio was significantly lower in the starved and fed phyllosoma (0.5) compared with that found in the newly hatched phyllosoma (0.9). The lipid profiles of the newly hatched, starved and fed phyllosoma contained large amounts of n‐6 fatty acids resulting in low n‐3 : n‐6 ratios (2.8, 2.7 and 1.6 respectively). The importance of these results and the ability of enriched Artemia to provide a suitable fatty acid profile for this species are discussed.     

Evaluation of Commercial Shrimp Grow-Out Pellets as Diets for Juvenile Southern Rock Lobster,Jasus edwardsii

Abstract

The growth, survival, and biochemical composition of juvenile southern rock lobster, Jasus edwardsii, were examined in response to a variety of diets, consisting of a natural food organism (blue mussel, Mytilus edulis) and/or commercial shrimp pellets. Blue mussel supported significantly better (a minimum of 25% higher) growth than a range of shrimp diets. Diet intake (0.83-1.26% wet body weight/day) and feed conversion ratio (1.34-2.48) with the formulated diets were generally similar to that with blue mussel (1.03% wet body weight/day; 1.55 feed conversion ratio). Changes in the chemical composition of southern rock lobsters due to treatments were more clearly observed in the digestive gland than in the whole body. Carapace color and tissue carotenoid level varied significantly with carotenoid content of the diets. A caro-tenoid level of 115 mg/kg is required in formulated diets to produce southern rock lobsters of similar color to wild-caught juveniles. In a separate experiment, a blue mussel diet was compared to mixed diets comprised of blue mussel and a shrimp, Penaeus monodon, diet. In the mixed diets, blue mussel was replaced with the formulated diet for either ×days/week or 6 days/week. Growth and survival did not differ significantly among treatments. The use of formulated diets in the culture of southern rock lobster appears feasible but will require increased knowledge of the nutritional requirements. Until specific diets are developed, this study has shown that similar growth can be obtained from a mixed diet, consisting primarily of a cheap formulated diet supplemented with blue mussel once per week. Such a scenario offers real possibilities for significantly reducing the cost of southern rock lobster production.     

Environmental influences on daily commercial catch rates of South Australia's southern rock lobster (Jasus edwardsii)

The extent to which catchability of southern rock lobster (Jasus edwardsii) due to short‐term environmental factors, rather than abundance, may be affecting legal‐size catch rates from the South Australian Southern Zone rock lobster fishery was examined. Multivariate weighted linear regression was applied to daily aggregated commercial catch rates using several environmental covariates in addition to year and month. Model pruning via backward selection identified the following variables as being significantly related to catch rate: wave height and period, lagged wave height, bottom temperature, moon phase, and a spatial block index. These variables explained 7% of the total variance in log‐transformed daily catch rates and another 84% was explained by month and year. A negative relationship was found between catch rate and each of bottom temperature and same‐day wave height, while the relationships between catch rate and days prior to full moon, and average wave height over the past 3 days were positive.     

Effects of marine reserve protection on spiny lobster (Jasus edwardsii) abundance and size at Tonga Island Marine Reserve,New Zealand

• 1. Diving surveys were undertaken to investigate the effects of marine reserve protection on spiny lobster (Jasus edwardsii) populations at Tonga Island Marine Reserve, northern South Island, New Zealand over a 2 year period from December 1998 to December 2000.
• 2. Spiny lobsters were 2.8 times more abundant overall, and mean size was 19 mm carapace length larger in shallow transects and 28 mm carapace length larger in deep transects, in the marine reserve than at adjacent fished sites. That pattern was evident despite very high variability within sites, and among sites within reserve and fished areas.
• 3. Large reproductive males were 10 times more abundant within the reserve compared to adjacent fished areas, suggesting that more eggs would be fertilized in the reserve than on the adjacent fished coast.
• 4. Estimates of size‐specific fecundity, combined with abundances of females, suggested that almost nine times more eggs would be produced in the reserve than in fished areas.
• 6. We estimate that the mean abundance of spiny lobster in the reserve has increased by 22%, 5 years after its establishment, indicating an annual population increase of 4.4%. Over the same period, abundance of spiny lobster outside the reserve has declined by 2.9% per annum.
• 7. Based on known spiny lobster movements, we suggest that marine reserves of more than 10 km length should be given priority over smaller reserves. Smaller reserves will, however, protect part of the population for at least a portion of their lifespan.
• 8. Previous studies of movement of J. edwardsii suggest that spillover from the reserve should occur, and as population density increases we predict that more spiny lobsters will move out from the reserve.

Copyright © 2002 John Wiley & Sons, Ltd.     

Differing environmental drivers of settlement across the range of southern rock lobster (Jasus edwardsii) suggest resilience of the fishery to climate change

Temporal and spatial trends in settlement of the southern rock lobster, Jasus edwardsii, were examined to identify the influence of environmental variables over different spatial scales. Settlement data were collected from 1994 to 2011 along the Southern Australian and New Zealand coasts. We identified common settlement trends at a regional scale (100–500 km): the magnitude of settlement at sites from South Australia (SA) and Victoria (VIC) were similar, but different to sites in Tasmania (TAS). In New Zealand, three spatial regions were identified: northern (NNZ), middle (MNZ) and southern regions (SNZ). Higher settlement in SA, VIC and MNZ occurred in years with higher rainfall and storms in spring and El Niño conditions. In TAS and SNZ, higher settlement occurred during La Niña conditions. These results suggest that settlement over regional scales is modulated by oceanic processes, but outcomes vary between regions. At a local scale, a higher wave period and wind relaxation were relatively more important than the sea surface temperature (SST) in SA and VIC. In TAS, the current velocity also influenced the strength of settlement. However, much of the local settlement variability was not explained by the models suggesting that settlement in J. edwardsii is a complex process where larval behaviour, biological factors and oceanographic processes interact over different scales. The apparently complex processes affecting settlement showed that environmental conditions that reduced settlement strength in one region of the fishery often increased settlement strength in other regions. This could provide resilience to climate change at the stock level.     

Tissue content, fecundity and quality of eggs and phyllosoma larvae after supplementing the diet of spiny lobster Jasus edwardsii broodstock with ascorbic acid-enriched Artemia biomass

Ascorbic acid (AA)‐enriched Artemia in alginate pellets and unenriched pellets were fed to Jasus edwardsii broodstock to supplement AA intake of the basal diet (mussels, squid and compound prawn pellets) during ovarian development before egg extrusion. Pellet AA content ranged from 150 μg g^?1 (unenriched) to 9153 μg g^?1 (enriched). The basal diet (150 μg AA g^?1) was compared with low (150 μg AA g^?1), medium (450 μg AA g^?1) and high (1350 μg AA g^?1) AA supplementation. Dietary AA content was obtained using combinations of unenriched and AA‐enriched Artemia in combination with the basal diet. Supplementation resulted in ovarian AA saturation at ～240 μg g^?1, a significant increase over 152 μg g^?1 at time 0. Digestive gland concentrations were 76–92 μg AA g^?1 for diets containing ≤450 μg AA g^?1, but reached 270 μg AA g^?1 for the high supplement. The considerable AA store in tail muscle appeared to be translocated to the ovary during maturation. There was no significant AA depletion in eggs during embryogenesis suggesting minimal AA utilization during this phase. Jasus edwardsii spawns once annually, unlike other multiple spawning crustaceans. Therefore, AA supplementation did not alter fecundity or phyllosoma quality, but resulted in a dose‐dependent increase (up to 33%) in AA content of eggs and phyllosoma.     

Artemia prey size and mode of presentation: Effects on the survival and growth of phyllosoma larvae of southern rock lobster (Jasus edwardsii)

Performance of phyllosoma of thesouthern rock lobster (Jasus edwardsii)was examined after feeding Artemia-baseddiets. Survival and growth of newly-hatchedlarvae cultured to Stage III were lower(p < 0.05) when fed 0.8 mm Artemia than1.5 mm or 2.5 mm Artemia alone or 1.5 mmArtemia in combination with pieces ofmussel (Mytilus edulis planulatus) gonad.This could not be attributed to deficiencies inthe composition of fatty acids but appeared tobe due to the inability of larvae to capturesufficient appropriate-sized, enrichedArtemia for their nutritional requirements.There was an indication that survival andgrowth were higher between Stages III and Vwhen fed 2.5 mm Artemia than 1.5 mmArtemia alone or in combination with musselpieces. However, Stage VI larvae grew to asimilar size at Stage VIII when fed 1.5 mm or2.5 mm Artemia. Unexpectedly, larvae fedthe combination of 1.5 mm Artemia plusmussel supplement had lower survival than foundpreviously, and generally lower than when fed 1.5 mm Artemia alone. This was despitean apparent nutritional profile (lipid contentand fatty acid composition) of mussel more akinto that of newly-hatched phyllosoma thanenriched Artemia. On the other hand,survival and growth to Stage VIII were higherwhen larvae were fed alginate pelletscontaining Artemia than when fed 1.5 mmor 2.5 mm Artemia alone.     

Ingestion of artificial diets with different textures as determined by the inert marker ytterbium oxide during culture of early‐stage phyllosoma of the spiny lobster,Jasus edwardsii

Instar 1 and 2 Jasus edwardsii (Decapoda; Palinuridae) phyllosoma larvae were fed an artificial diet formulation (based on fish and mussel) consisting of three different gelatin combinations (firm, 4% inclusion; medium, 2% inclusion; and soft, no gelatin). The diet contained ytterbium oxide (Yb₂O₃; 1% inclusion), an inert heavy metal marker, which was used to confirm diet consumption in instar 1 and 2 phyllosoma. Over a 6‐h feeding period, instar 1 phyllosoma showed a preference for the soft and medium diets as opposed to the firm diet, but this effect was not significant with instar 2. The artificial diets remained palatable over the duration of the experiments, suggesting leaching did not influence diet attractiveness. It is suggested that diets comprising softer food items such as microencapsulated pellets or gelatinous formulated diets and pastes are most suitable for early‐instar phyllosoma. Furthermore, it is also suggested that Yb₂O₃ is a potentially useful marker for ongoing quantitative work on diet utilization in lobster larvae.     

Optimal feed pellet size for culturing juvenile spiny lobster Jasus edwardsii (Hutton, 1875) in New Zealand

There is intense international interest in the development of spiny lobster aquaculture and of particular interest is the development of artificial diets for spiny lobsters. However, there is little information on the feeding behaviour of spiny lobsters and their ability to handle and consume artificial feeds of different dimensions. Observations of the feeding behaviour of juveniles of the spiny lobster Jasus edwardsii in culture found that they waste significant amounts of food through externally fragmenting the feed pellets before sweeping particles into the mouth. The consumption efficiency of different sized pellets was found to change markedly with increasing size of the juvenile lobsters. Up to 50% of artificial food was wasted by the inefficient feeding behaviour of the lobsters. However, consumption of the feed could be reduced by as much as 19% by altering pellet size. These results indicate that the size of feed pellets, and their consistency and fragmentation characteristics, will be critical aspects of cost‐effective feeding of cultured spiny lobsters.     

The effects of temperature and diet on the survival, growth and food uptake of aquarium-held postpueruli of the rock lobster Jasus lalandii

Aquaculture of the rock lobster Jasus lalandii has been considered, but is hindered by a paucity of knowledge about conditions that promote yields. This study investigated the influences of temperature and diet on the growth of aquarium-held postpueruli of J. lalandii. First, postpueruli (11.5±0.2 mm CL) were exposed to temperatures spanning 12–24 °C for a total time period of 77 days, while being given a constant diet of mussel flesh. Under these conditions, intermoult period (IMP) was longest at 12 °C (50.6±1.2 days) and at 24 °C (>57 days), and shortest at 18 °C (35.5±1.1 days). Growth increments (GI) were large at 12–18 °C, smaller at 21 °C and negative at 24 °C. Survival was 100% at 12–16 °C, above which mortalities rose to 70% at 24 °C. Food consumption, body mass and condition all peaked at 18 °C. Thus, growth was optimal at 18 °C, but survival greatest at 12–16 °C.

Second, diet-controlled experiments examined the effects of three different diets (blue mussel, commercial shrimpfeed or an alternation of the two) on survival, growth (IMP and GI) and food uptake of postpueruli (11.0±0.3 mm CL) held at 18 °C for a total time period of 77 days. Feeding rate, average growth, body mass and condition were all highest on the mussel diet, and lowest on the shrimpfeed, and the postpueruli consumed more mussel flesh than shrimpfeed. There was little difference in survival of postpueruli subjected to the three diet treatments.

A diet of exclusively blue mussel yielded higher growth, body mass, condition and food uptake than a diet of either shrimpfeed alone or an alternation of mussel and shrimpfeed. The postpueruli acclimated well to culture conditions and survived on a diet of artificial pellets, thus showing good potential for mariculture. On the present evidence, greatest returns are likely at 16–18 °C and with a diet of mussel flesh.     

Feeding has the largest effect on the ammonia excretion rate of the southern rock lobster, Jasus edwardsii, and the western rock lobster, Panulirus cygnus

The total ammonia nitrogen (TAN) excretion of spiny lobsters Jasus edwardsii and Panulirus cygnus, was determined in relation to temperature, body weight, emersion, daily rhythm and feeding. Temperature and body weight had large influences on the rate of TAN excretion. Exponential relationships were found between temperature (T) and TAN excretion of both species. These were described by the following equations: J. edwardsii Log₁₀ TAN=0.041T−3.57 (r²=0.979, F=143.2, P=0.001), P. cygnus Log₁₀ TAN=0.057T−3.90 (r²=0.987, F=302.2, P<0.001). TAN excretions of both species were positively correlated to body weight (W), and the relationships were described by the following equations: J. edwardsii Log₁₀ TAN=0.473 log₁₀ W−1.704 (r²=0.42, F=14.05, P=0.001), P. cygnus Log₁₀ TAN=0.499 log₁₀ W−1.346 (r²=0.69, F=44.18, P<0.001). TAN excretion increased significantly when lobsters were re-immersed after a 30 min period of emersion. However, it returned to pre-emersion levels by the second hour of re-immersion. Daily rhythm resulted in a significantly higher nocturnal TAN excretion rate for J. edwardsii; no daily rhythm was observed for P. cygnus. Feeding had the largest influence on TAN excretion, with maximum increases of 6.28 (J. edwardsii) and 5.60 (P. cygnus) times the pre-feeding level. TAN excretion rates remained significantly higher than the pre-feeding levels for an extended period (26 h, J. edwardsii; 30 h, P. cygnus). Implications for the use of purging tanks in lobster holding facilities and for the design of biofiltration systems are discussed.     

An evaluation of the nutritional value of alternative lipid sources to juvenile southern rock lobster, Jasus edwardsii

Experimental lobster feeds are currently based on fish meal and fish oil formulations, and although survival and growth similar to that of lobsters fed fresh blue mussels has been achieved, varying the protein level in previous experimental feeds has not increased growth beyond that of lobsters fed natural food. This experiment assessed the growth performance of lobsters fed pelleted feeds containing constant amounts of protein, lipid and energy where the lipid was provided by a range of oil-rich ingredients (fish oil, FO; fish oil with added soybean lecithin, FOL; canola oil, CO; tuna oil, TO; mussel meal, MM; and squid meal, SQM). Feed performance was assessed by lobster growth rate, survival, final biochemical composition, nutrient retention and nutrient efficiency. Twenty tanks containing 15 post-larval lobsters each (1.5 ± 0.04 g) were randomly allocated one of six test feeds in triplicate, and the two remaining tanks were fed freshly opened blue mussels (FRM) as a reference feed. Lobsters were fed daily to excess for 10 weeks. Final individual weights of whole body and digestive gland were measured, and tissue chemical composition analysed. There were no significant differences in survival (88.4 ± 3.3%), or specific growth rate (1.3 ± 0.1%.day^− 1) among the formulated feed fed lobsters, which were significantly lower than the survival (100 ± 0.0%) and SGR (2.2 ± 0.1%.day^− 1) of FRM fed lobsters. The SQM fed lobsters had a significantly lower lipid efficiency ratio and lipid productivity value than lobsters fed TO, FOL and MM feeds. The digestive gland lipid content (g.100 g wet tissue^− 1) of lobsters fed the feeds TO (3.7 ± 0.4), FO (3.5 ± 0.3) and SQM (2.2 ± 0.2) were significantly lower than lobsters fed feeds MM (9.9 ± 1.1), FOL (9.0 ± 2.3) and FRM fed lobsters contained most digestive gland lipid (12.3 ± 1.5).     

Potential virulence factors of bacteria associated with tail fan necrosis in the spiny lobster,Jasus edwardsii

Tail fan necrosis (TFN) is a common condition found in commercially exploited spiny lobsters that greatly diminishes their commercial value. Bacteria possessing proteolytic, chitinolytic and lipolytic capabilities were associated with TFN in spiny lobsters, Jasus edwardsii. In this study, 69 bacterial isolates exhibiting all the three enzymatic capabilities from the haemolymph and tail fans of J. edwardsii with and without TFN were further characterized and compared, including morphology, biofilm formation, antimicrobial activity, antimicrobial resistance, and production of siderophores, melanin and ammonia. The genomic patterns of the most common Vibrio crassostreae isolates were also compared between TFN‐affected and unaffected lobsters. Biofilm formation was stronger in bacterial isolates from both haemolymph and tail fans of TFN‐affected lobsters compared to those from the unaffected lobsters, while melanin production and siderophore production were stronger in the isolates from tail fans of lobsters with TFN. By contrast, the other characteristics of isolates were similar in lobsters with and without TFN. The Vib. crassostreae isolates from the affected lobsters had similar genomic patterns. Overall, the results indicate that in addition to proteolytic, chitinolytic and lipolytic activities, the bacteria associated with TFN commonly have enhanced activity of important virulence factors, including biofilm formation, melanin production and siderophore production.     

The effect of PUFA enriched Artemia on growth, survival and lipid composition of western rock lobster, Panulirus cygnus, phyllosoma

Western rock lobster, Panulirus cygnus, phyllosoma were grown from hatching to stage IV. Larvae were fed with Artemia enriched with a (i) base enrichment (Base) containing 520 g kg^?1 squid oil or tailor made enrichments in which oils high in polyunsaturated fatty acid (PUFA) have been added at the expense of squid oil. These treatments were (ii) base enrichment supplemented with docosahexaenoic acid (DHA) rich oil, (iii) base enrichment supplemented with arachidonic acid (AA) rich oil, or (iv) base enrichment supplemented with DHA and AA (D + A) rich oils. Total survival of phyllosoma to stage IV was high, with no significant difference between treatments (range 12.3–17.5%). By stage IV, the larvae fed the DHA or AA enriched Artemia were significantly larger (3.33 mm length) than larvae fed the Base or D + A enriched Artemia (3.18–3.24 mm length). Phyllosoma were sampled at stages II and III for biochemical analysis. The major lipid class (LC) in all phyllosoma was polar lipid (PL) (88.9–92.4%), followed by sterol (ST) (6.2–9.7%). Triacylglycerol (TAG), free fatty acid (FFA) and hydrocarbon/wax ester were minor components (≤1%) in all phyllosoma samples. In contrast, the major LC in all enrichments and enriched Artemia was TAG (76.3–85.1% and 53.4–60.2%, respectively), followed by PL (11.4–14.8% and 30.6–38.1% respectively). The main fatty acids (FA) in phyllosoma were 16:0, 18:1n‐9, 18:1n‐7, 18:0, AA, eicosapentaenoic acid (EPA) and DHA. Addition of AA, and to a lesser extent DHA, to enrichments resulted in increased levels of those FA in Artemia and phyllosoma compared with the Base enrichment. This was particularly evident for stage III larvae. Comparatively, elevated growth for phyllosoma to stage IV was achieved with DHA and AA enriched diets. Our findings highlight the importance of lipids and in particular essential long‐chain PUFA, as nutritional components for phyllosoma diets.     

Lipid and fatty acid composition of likely zooplankton prey of spiny lobster (Jasus edwardsii) phyllosomas

Several of the world's major spiny lobster fisheries, including Jasus edwardsii in Australasia, have gone into dramatic decline due to decreasing recruitment of their lecithotrophic postlarvae. There is evidence that the decline is related to poor nutritional condition of the postlarvae, especially lipid that is accumulated in large quantities during the preceding pelagic larval stage. Therefore, characterizing the lipid composition of the likely potential zooplankton prey of the larvae (phyllosomas) of spiny lobsters will provide new insights into their nutritional requirements. The lipid class and fatty acid composition of more than 30 species of likely zooplankton prey of the larvae of the spiny lobster, J. edwardsii, were determined. These results showed that most zooplankton prey had a high proportion of their lipid content as polar lipid (PL) (range of 9.4–94.8%, mean of 76.1 ± 2.6%). Zooplankton prey provide phyllosomas with polyunsaturated fatty acids (PUFA) for growth and development, as well as a range of other important fatty acids that are accumulated as PL and used for fuelling the migration of the subsequent lecithotrophic postlarvae across the continental shelf. Overall, these results indicate that phyllosomas consume prey with wide ranging lipid content, but dominated by PL, and high in docosahexaenoic acid, eicosapentaenoic acid and the key fatty acids used for energy storage.     

The effect of temperature on the growth, survival and food consumption of the east coast rock lobster Panulirus homarus rubellus

The successful culture of the east coast rock lobster Panulirus homarus rubellus is reliant, among other factors, on the provision of optimal water quality for growth and survival. This study investigated the effect of temperature over a range of 9.7 °C (18.9 ± 0.7 °C to 28.6 ± 1.5 °C) on the growth and survival of juvenile (40.4 ± 9 mm CL; 63.64 ± 12.05 g) P. h. rubellus fed a diet of fresh mussel flesh. Specific growth rate (SGR) was significantly different between temperatures (p = 0.01), with the highest values recorded for the 24 and 28 °C treatments. There was no significant difference in moult increment (MI) between temperatures in terms of both an increase in weight (p = 0.83) and carapace length (p = 0.54). Intermoult period (IMP) differed significantly between temperatures (p = 0.0015) with mean IMP lowest at 24 °C, although not significantly different from the means of the 26 and 28 °C treatments. IMP was highest at 19 and 21 °C. Apparent feed intake was significantly different between treatments (p < 0.0001) and exhibited a strong positive correlation with increasing temperature (y = − 1.67 + 0.16x ; r² = 0.81). Food conversion ratio (FCR) differed significantly between temperatures (p = 0.02) with 24 °C exhibiting the most efficient FCR. Results indicate that efficient growout of juvenile P. h. rubellus, in terms of both growth and food conversion efficiency, is obtainable at 24 °C.     

The effect of dietary carbohydrates on the growth response,digestive gland glycogen and digestive enzyme activities of early spiny lobster juveniles,Jasus edwardsii

The effect of various carbohydrate sources (glucose, sucrose, agar, wheat, tapioca, maize, potato and dextrin), and inclusion levels of gelatinized maize starch (0, 70, 170, 270 g kg^?1), incorporated in semi‐purified diets on the performance [growth, survival, food consumption (FC), enzyme activity and glycogen content of the digestive gland (DG)] of spiny lobster juveniles was investigated in a 12‐week culture experiment. There was no difference in specific FC among diets (1.1% BW day^?1), but lobsters fed with fresh mussel grew significantly faster (specific growth rate = 1.8% BW day^?1) than on the formulated diets (0.9–1.1% BW day^?1). None of the carbohydrate supplements tested produced a significant improvement in growth or survival over a basal control diet. However, the diet containing 270 g kg^?1 native wheat starch resulted in the highest moulting (mean = 2.1 moults per lobster), glycogen (3.3 mg g^?1) and free glucose (1.1 mg g^?1) concentrations among lobsters fed with the formulated diets, suggesting a superior utilization of this source of carbohydrate. The greater glycogen (8.0 mg g^?1 tissue) and free glucose (2.0 mg g^?1 tissue) concentrations, as well as higher specific activity of α‐amylase (2.3 versus <0.7 U mg^?1 for other diets), found in the DG of lobsters fed with fresh mussel indicated a metabolism strongly directed to the utilization of glycogen.