Effects of dietary carbohydrate on growth of juvenile New Zealand rock lobsters, Jasus edwardsii

The commercial aquaculture of spiny lobsters is impeded by the development of effective practical diets, which is partly due to a lack of knowledge of the digestive capabilities and nutritional needs of these species. Carbohydrates have the potential to provide a low cost energy source in practical diets for spiny lobsters. This research investigated the effect of algal carbohydrates, on the growth of juvenile rock lobsters. Juvenile lobsters, Jasus edwardsii, (10-12 mm carapace length) were provided with one of five diets; blue mussel, squid (Nototodarus gouldii), or a mussel diet partially substituted with algal carbohydrates, either agar, carrageenan or alginate over 80 days in culture. In all treatments, diet consumption and lobster growth were maintained or increased over time. Growth was highest for the mussel diet followed by the agar diet. Similar lobster growth occurred on the carrageenan and alginate diets, with the least on the squid diet. After 80 d there were significant differences in the percent lipid and glycogen stored in the mid-gut gland with highest levels of glycogen in lobsters fed the mussel only diet. Percent protein in the tail muscle was greatest for mussel fed lobsters. The mid-gut index (mid-gut weight/whole wet weight) was highest for the mussel only diet and this was similar to control lobsters at the start of the experiment. The results indicate that glycogen from mussels and agar could be used as carbohydrate source in the future development of a practical diet for spiny lobsters.     

The first returns of tagged juvenile lobsters [Homarus gammarus (L.)] after release to the wild

The success of re-stocking lobster fishing grounds has been difficult to assess given the problems of tagging juvenile lobsters. A system of tagging using a 1 mm long × 0.25 mm diameter stainless steel micro-tag has been used during a study of the feasibility of restocking fishing grounds with hatchery-reared juvenile lobsters. The first returns of juveniles tagged by this method are described.     

Does Morning as Opposed to Night‐time Feeding Affect Growth in Juvenile Spiny Lobsters,Jasus edwardsh?

Previous research on juvenile lobsters has shown that they display a nocturnal rhythm in their oxygen consumption and ammonia excretion, such that lobsters that are fed in the morning have shorter specific dynamic action (SDA) response than those lobsters that are fed at night. It was therefore suggested that juvenile lobsters should be fed in the morning to maximize energy utilization. This research tested the hypothesis that the growth of juvenile rock lobsters would be improved by feeding in the morning rather at night. Juvenile spiny lobsters Jasus edwardsii were fed a squid meal (5% body weight) either in the morning or at night over a period of 80 d. Lobsters fed in the morning had a 108% weight gain, an increase of 4.6 mm in carapace length and a growth rate (SGR) of 0.92%. These were significantly higher than the 78% weight gain, carapace length increase of 3.8 mm, and growth rate of 0.76% recorded for lobsters fed at night. Abdomen muscle protein and mid-gut gland lipid and glycogen content were similar after 80 d. The digestive gland index (DGI) was the same in lobsters exposed to the different feeding regime but had decreased compared with control lobsters at the start of the experiment. Morning-fed lobsters outperformed night-fed lobsters in all aspects of growth and survival, and it is suggested that commercial farmers feed their lobsters in the morning rather than at night. Because these growth differences were predicted from specific dynamic action measurements, it is concluded here that this technique would be useful for the rapid evaluation of the effectiveness of natural and artificial diets on lobster growth.     

Acute toxicity of emamectin benzoate (SLICE™) in fish feed to American lobster, Homarus americanus

SLICE? (active ingredient 0.2% emamectin benzoate (EMB)), a feed premix developed by Schering‐Plough Animal Health for the control of sea lice on cultured salmonids, is registered for use in several countries and is being prescribed on an emergency basis in Canada and the United States. The concentration of EMB in feed administered to farmed salmon ranges from 1 to 25 μg g^?1. To determine the acute toxicity of the compound to juvenile and adult American lobster (Homarus americanus), commercial salmon feed was coated with SLICE? at a range of concentrations and provided to the animals for 7 d in the laboratory. The LC₅₀ is estimated to be 644 μg g^?1 (95% CI=428, 1275) for adult lobsters and >589 μg g^?1 for stage V and VI juvenile lobsters. The consumption of medicated pellets by adult lobsters decreased significantly with increasing concentration of EMB. Adult lobsters that died during the study had a significantly greater concentration of emamectin B1a in their muscle tissue than those that survived. These results support the conclusion that salmon feed medicated with EMB at the concentrations used by the aquaculture industry is unlikely to pose an acute lethal threat to adult and small juvenile American lobsters.     

Evaluation of fungicides for Haliphthoros milfordensis and their toxicity to juvenile European lobsters

Twenty-two potentially fungitoxic compounds were evaluated for their in vitro inhibition of the mycelial growth of Haliphthoros milfordensis. Chemicals with a minimum inhibitory concentration of 10 ppm or less were further tested for toxicity to juvenile European lobsters. Of these compounds, malachite green and Furanace had the lowest minimum inhibitory concentrations at 0.25 and 2.5 ppm respectively. Acriflavine, crystal violet, methylene blue, nifuroxime, butyl paraben and chloroxine were inhibitory to the fungus at a concentration of 10 ppm. Dip and swab applications were tested to assess in vivo toxicity to lobsters of the effective chemicals.     

The suitability of VIE tags to assess stock enhancement success in juvenile European lobsters (Homarus gammarus)

Assessments of stock enhancement programmes for European lobsters (Homarus gammarus) require mark‐recapture analysis of stocked individuals. However, established tag technology is deemed unsuitable for extensive use by many current lobster hatcheries, particularly upon the early juvenile stages. We tested the suitability of fluorescent Visible Implant Elastomer (VIE) tags for use in 5‐month‐old juvenile lobsters. Three treatment groups comprising 348 cultured lobsters in total were used to examine survival, growth and tag retention, and to assess mobility, shelter use and moulting behaviours. Tagging had no significant effect on lobster survival, growth, mobility, shelter use or moult frequency. Survival over 7 weeks was 75% among lobsters tagged with two elastomers, 76% in those with one elastomer and 74% among untagged controls. Mortality during moulting did not increase in tagged (6%) compared to untagged lobsters (9%). We found no evidence that VIE tags cause any negative effects that would be expected to inhibit survival upon wild release, but tag loss had reached 12% in both tagged treatments after 7 weeks and showed no sign of abating. Our study suggests that VIEs effectiveness in discerning cultured lobsters long after wild release may be limited when used in smaller juveniles.     

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.     

Effect of Dietary Lecithin in Combination with Casein or Crab Protein on Cholesterol Uptake and Transport in the Lobster Homarus americanus

Purified diets, formulated with and without lecithin and containing either casein or a protein isolated from whole crab, were fed to juvenile lobsters. In order to examine the role of these dietary factors on cholesterol uptake and transport, levels of cholesterol were determined in serum, lipo-protein fractions, tissues, and feces of juvenile lobsters fed the experimental diets. Lobsters fed diets supplemented with lecithin had significantly higher levels of serum and lipoprotein cholesterol than lobsters fed diets without supplemental lecithin regardless of the proteins used. Levels of fecal total cholesterol also were generally greater for lobsters fed lecithin-supplemented diets. Tissue, serum, and fecal levels of intubated radiolabeled cholesterol, however, were not significantly different among diet groups, and apoprotein electrophoretic mobility was not affected by the choice of dietary protein.     

The Effect of Different Dietary Energy Levels on Growth and Survival of Eyestalk Ablated and Intact Juvenile Lobsters Homarus americanus

When fed formulated diets containing 45% protein derived from the rock crab Cancer irroratus , wheat gluten, gelatin, lipids adjusted from 3–14% and carbohydrates adjusted from 5–24%, the average survival of bilaterally eyestalk ablated juvenile lobsters and intact controls were 91% and 99%, respectively over a 90-day experiment. Photopenad (13 light: 11 dark vs 3 light: 21 dark) did not have a significant effect on growth or survival of ablated or intact lobsters. The optimal digestible energy levels and protein/energy ratio for the greatest growth in both ablated and intact lobsters were 3.7 to 3.8 (kcal/g dry) and 0.12 [g protein/(kcal/g)], respectively. The best feed conversion ratios (0.97 and 1.40 diet given/weight gain) for ablated and intact lobsters were obtained with diets containing 3.83 kcal/g and 3.63 kcal/g diet, respectively. The present study also demonstrated that crab protein served as a good protein source for intact and ablated lobsters.     

The use of fresh food supplements to ameliorate moulting difficulties in lobsters, Homarus gammarus (L.), destined for release to the sea

Abstract. Compounded diets given to juvenile lobsters, Homarus gammarus (L.), during the critical post-settlement phase of their development induced moulting abnormalities that resulted in limb loss and deformity. These potentially lethal effects were minimized, and in some cases overcome, through the provision of a supplement of natural food given just once or twice each week. The degree to which a poor diet could be improved was proportional to the quality and frequency of supplementation. Both moult increment and frequency were affected by dietary regime. A quantitative index of general health was derived from selected physical attributes exhibited by juvenile lobsters, which was useful in assessing a combination of responses to different diets and supplements.     

Survival and growth of western rock lobster Panulirus cygnus (George) fed formulated diets with and without fresh mussel supplement

Two trials were conducted to compare the growth and survival of western rock lobster Panulirus cygnus post-pueruli and year 1 juveniles fed different diets. Trial 1 compared lobsters fed a formulated pelletised feed developed for Panulirus ornatus supplemented with fresh mussels (Mytilus edulis) two days per week, with lobsters fed a daily diet of pellets. Trial 2 compared lobsters fed the pellet-mussel supplement diet with those fed a daily diet of fresh mussels.In the first trial, diet treatment did not significantly affect survival, although it was higher in tanks supplemented with mussels. Growth of post-pueruli and year 1 juveniles fed the pellet diet (0.03 g/day; 0.14 g/day, respectively) was significantly lower than growth of post-pueruli and year 1 juveniles fed pellet-mussel supplement diets (0.07 g/day; 0.2 g/day, respectively). Year 1 lobsters fed the pellet-mussel supplement diet consumed considerably less pellet (0.27 vs 0.40 g pellet dry matter/day (DM/day)) than those fed pellets indicating that they will preferentially favour mussel over pellet diets. Feed conversion ratio (FCR) was significantly better for lobsters fed the pellet-mussel supplement diet as a result of the poor growth of pellet-fed lobsters.In the second trial, survival was significantly higher for lobsters fed mussels only. Growth of post-pueruli fed a mussel diet (0.14 g/day) was significantly higher than those fed pellet-mussel diets (0.11 g/day), but there was no significant difference in growth for year 1 juveniles (0.33 g/day). Feed intake of mussel on a dry matter basis was higher than pellet intake for both size classes, with mussel intake being more than double pellet intake for post-pueruli (0.20 vs 0.49 g DM/day).Poor growth of P. cygnus on a pellet only diet indicates that the current formulation for P. ornatus may be inadequate for P. cygnus. However, as pellet intake declined dramatically for year 1 lobsters offered a mussel supplement, and pellet consumption was significantly lower than mussel consumption, it is more likely that poor growth may be attributed to inadequate palatability and intake. The similarly good survival of lobsters fed pellet and pellet-mussel diets indicates that the pellet diet is an acceptable maintenance diet for P. cygnus, but is not suitable for maximising growth for this species. Further research is needed to improve palatability, intake and potentially nutritional composition of this pellet diet before its suitability for P. cygnus is assured.     

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

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.     

Bait-subsidized diets and their effects on ovigerous North American lobsters (<Emphasis Type="Italic">Homarus americanus</Emphasis>)

Ovigerous American lobsters (Homarus americanus) display a protracted period of ovary maturation and maternal care when incubating their eggs, potentially influencing offspring fitness. Lobsters consume a wide range of food items; however, trap bait may comprise a larger proportion of their diet in some fished areas compared to non-fished areas, and the long-term consequences of a bait-based diet remain largely unexplored in lobsters. We tested the hypothesis that disproportionate amounts of bait in the diets of pre-ovigerous females affect the quality of their ovaries and eggs. We held pre-ovigerous lobsters (n?=?29) over a period of ~?300 days (range?=?270–378) and fed them diets of herring bait, natural prey items (crab, mussel, urchin, macroalgae), or a combination of both diet types. Nutritional status, measured as biweekly blood indices and total glucose levels, suggest differences between lobsters fed a natural or combination diet and lobsters fed a bait-based diet (ANOVA; P?<?0.05). We found that bait diets contained more protein (58.5%) and lipids (31.6%) compared to natural diets (34.5 and 13.2%, respectively) and lipid levels in ovaries and eggs significantly correlated with each other for all treatments (r?=?0.76, n?=?15, P?=?0.028). Histopathological analysis indicates that ovaries contained more variable maturation in starved lobsters or those fed with bait, with some animals showing delayed gonad maturation. Results suggest that a varied diet promotes the overall fitness of ovigerous lobsters and the associated reserves that are used for ovarian development and subsequent oocyte formation.     

The effect of photoperiod on growth, survival, colour and activity of juvenile southern rock lobster, Jasus edwardsii

Juvenile (1–10 g) southern rock lobsters, Jasus edwardsii, were subjected to five photoperiods [0L(light):24D(dark); 6L:18D; 12L:12D; 18L:6D; 24L:0D] during a 112‐day trial, and growth, survival, colour, food consumption and activity were examined. Lobsters grown under the 6L:18D and 24L:0D photoperiods had significantly lower (P < 0.05) final mean weight and specific growth rate than any other treatments. Photoperiod had no effect on survival or colour of lobsters. Food consumption differed significantly during the first week of the trial; after 5 weeks, food consumption was similar in all treatments. Major peaks in activity occurred during dark periods for lobsters exposed to photoperiods that had a light:dark regime. Activity of lobsters exposed to continuous light or dark regimes remained constant and at low levels during the 24‐h period. Food consumption or activity does not appear to determine the rate of growth of lobsters in the different photoregimes. One over‐riding outcome of this and other studies on photoperiod is that the growth and survival response of juvenile J. edwardsii was not significantly better than those of the standard 12L:12D cycle.     

Survival and growth of juvenile lobster Homarus gammarus L. raised for stock enhancement within in situ cages

The growth of juvenile lobster Homarus gammarus L. reared on sandy sediments under laboratory conditions was compared with the growth of lobsters reared within in situ cages in the wild. The caged lobsters, left without any attention or care for 3 months, achieved an average size similar to that attained under optimal laboratory conditions. (8.8 mm carapace length; CL). Growth was positively correlated to cage size and depth. Overall average survival was 66%, ranging from 0% to 90% for clusters of 30 individually caged juveniles.     

Effects of container transparency and reflectivity upon oxygen consumption of hybrid lobsters

The effect of intra-specific visual communication on the rate of oxygen consumption of hybrid lobsters (Homarus americanus × H. gammarus) was tested in a partitioned metabolic chamber. Three partition linings were tested: opaque rubber, clear plexiglass, and glass mirror. Short-term mean oxygen comsumption rates observed for lobsters separated by rubber-lined partitions were 8% lower than those of lobsters separated by the clear partitions, and 29% lower than those of lobsters separated by mirrored partitions (P < 0.001).     

IMPROVED FACILITIES FOR EXPERIMENTAL CULTURE OF LOBSTERS

Experimental culture facilities for juvenile lobsters have been improved, resulting in more uniform water quality, and greater precision of experimental results. Water-powered rotating arms distribute freshly treated water throughout the system, and a mechanism for rapid flushing aids in maintaining water quality and removing solid waste. These systems which can be used for other benthic invertebrates now provide culture conditions close to optimum for highly controlled nutrition experiments.     

A comparison of techniques for the measurement of growth in adult lobsters

Four non-destructive measures of growth (wet weight in air, wet weight in water, displacement volume and carapace length) were correlated to two destructive measures of growth (dry weight and total body protein level) in adult American lobsters (Homarus americanus). All non-destructive parameters were significantly (P < 0.05) correlated to dry weight and protein for female lobsters. Only wet weight in water was significantly correlated to dry weight and total body protein level in male lobsters.     

Use of formulated diets as replacements for Artemia in the rearing of juvenile American lobsters (Homarus americanus)

American lobsters, Homarus americanus, have been successfully reared in hatchery operations for over a century, yet formulated diets have never been commercially produced. In recent years, commercial Artemia replacement (CAR) diets have been developed and marketed for use in aquaculture production of marine shrimp. Three separate experiments assessed the utility of rearing American lobsters on these shrimp CAR diets. First, survival and growth of stage IV American lobsters fed one of three CAR diets (Artemac 5, CAR1; Economac 4, CAR2; and Progression 3, CAR3) were compared to those of animals fed frozen adult n-3 fatty acid enriched Artemia. Survival to 3 months was highest for animals fed CAR3 (85%), while animals fed Artemia had the greatest weight gain (> 6 % day^− 1). A cost / benefit ratio analysis showed that CAR2 was the most cost efficient for juvenile production because of its low overall purchase cost. Second, stage IV lobsters were fed either CAR2 or frozen adult n-3 fatty acid enriched Artemia exclusively, or in combination (2 : 5, and 5 : 2). Again, CAR2 was a cost effective feed to use, even as a partial replacement for Artemia. Survival was higher in diets that included CAR2, and feeding it two days per week compensated for low quality Artemia. Finally, 1.5 year old lobsters fed a gelatin-bound mix of 80% CAR2 and 20% frozen Artemia for five months survived and grew equally well compared to lobsters fed gelatin-bound frozen adult Artemia, and better than a custom formulated maintenance diet. The benefits of incorporating formulated feeds into American lobster rearing programs to increase the effectiveness of enhancement programs is discussed.     

Sterol requirement of juvenile lobsters, Homarus sp.

Juvenile lobsters were fed purified or unrefined diets in which the qualitative and quantitative sterol composition varied. Dietary cholesterol was required. A level of dietary cholesterol as low as 0.12% (dry weight) in a purified diet was satisfactory for normal growth and survival. No significant increases in growth were observed when lobsters were fed unrefined diets with cholesterol levels ranging from 0.19 to 0.59% (dry weight). Total cholesterol content of the whole body tissue lipid ranged from 0.012 to 0.046% (wet weight), lowest values being characteristically associated with those animals fed purified diets virtually devoid of cholesterol. Serum sterol levels were similar except for reduced levels associated with the sterol-free diet.Total replacement of cholesterol with a mixture of phytosterols composed primarily of β-sitosterol did not yield good growth and survival. Phytosterols composed large proportions of the total body sterols of those lobsters fed diets containing phytosterols exclusively. At least a portion and possibly all of the sterol requirement of juvenile lobsters is specific for cholesterol.