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.     

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.     

A recirculating system for small-scale experimental work on juvenile lobsters (Homarus americanus)

A refrigerated closed system unit for performing small-scale experimental studies on juvenile lobsters (Homarus americanus) is described. Water is recirculated through a series of filters to juvenile lobsters housed in trays and separated from each other by movable dividers. Tests showed that there was minimal fluctuation in water quality and that lobster development and survival were more a function of nutritional variation than of changes in physical parameters. The system is compact, inexpensive and well suited to small-scale research with aquatic animal culture.     

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.     

Ammonia production and oxidation during the culture of marine prawns and lobsters in laboratory recirculation systems

Data obtained during the culture of tropical prawns Penaeus sp. and European lobsters Homarus gammarus (L.) in 20 laboratory recirculation systems over a number of years were used to obtain gross estimates of (a) the rates and diurnal patterns of ammonia excretion, (b) food utilization and wastage, and (c) nitrification rates in biological filters. Ammonia excretion in Penaeus monodon decreased with increase in animal size from 0·93 to 0·30 mg N g^?1 day^?1 at 1·6 and 27 g live weight, respectively. Large lobsters (300 g) excreted 0·3 mg N g^?1 day^?1. Peak excretion times were approximately 3, 9 and 15 h after a single morning feed for prawns and after 6 and 12 h for lobsters. Uneaten food solids amounted to 11% (lobsters) and 32% (prawns) of the daily ration and, for 4 g animals, only 69% (lobsters) and 45% (prawns) of the food nitrogen in the daily ration was converted into crustacean flesh. Nitrification rates ranged from 0·03 to 0·43 g N oxidized per m² of filter media surface per day. Some evidence for periodicity in nitrifying activity was also found and is discussed in relation to the published literature.     

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).     

Lobster,Homarus americanus,Gastric Fluid Is a Barrier to the Ciliate,Anophryoides haemophila,in an in vitro Study

ABSTRACT

Ciliated protozoan disease caused by Anophryoides hae-mophila, also called “bumper car” disease, has been noted in impounded American lobsters, Homarus americanus, in the Gulf of Maine from 1990 to the present. One possible infection route for ciliated protozoan disease in the American lobster is through the digestive tract. The survival of A. haemophila in gastric fluid from healthy lobsters was tested in vitro. “Bumper cars” did not survive exposure to diluted gastric fluid for longer than one minute. Most ciliates (99%) died within 30 seconds of exposure to gastric fluid. All ciliates died within one minute. Disruption of the ciliate cuticle was apparent after two minutes. The cuticle was completely lysed in six minutes. All ciliates were digested in 8 minutes. These data suggest ciliate infection of American lobsters through the digestive tract is unlikely and cannibalism of infected lobsters is unlikely to result in transfer of the disease.     

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.     

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.     

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.     

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 Effect of Dissolved Oxygen Level on the Weight Gain and Shell Hardness of New-Shell American Lobster Homarus americanus

Abstract— New-shell American lobsters Homarus americanus stored in tidal pounds or on-shore tank systems are fed to promote weight gain and shell hardness prior to shipping. Maintaining adequate dissolved oxygen (DO) levels in the water is an important consideration in this process, and information on optimum DO levels is needed. In this study, 90 post-molt lobsters were weighed and tagged and held in a recirculating seawater system. Three DO treatments, 50%. 100%. and 250% saturation, were applied in three replicates; the lobsters were held for 35 d and fed daily. After this period they were re-weighed and shell hardness was measured. Results showed that increasing oxygen saturation above 100% did not increase weight gain or shell hardness and at lower levels (50%) there is only a trend to reduced shell hardness and weight gain.     

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.     

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.     

Gaffkemia in the California spiny lobster, Panulirus interruptus: Infection and immunization

Infection (gaffkemia) can be induced in the California spiny lobster (P. interruptus) with injections of Pediococcus homari (formerly Gaffkya homari). An LD_{5 0} of 10³ microbes per ml hemolymph is observed at 17°C. Prior immunization of lobsters (P. interruptus) with an avirulent strain of P. homari protects lobsters against 100 × LD_{5 0}. This is the first report of acquired immunity to P. homari in a susceptible species. The high incidence of gaffkemia in American lobsters (Homarus americanus) held in live holding facilities makes prophylactic measures essential in regions outside the enzootic area of the North Atlantic to avoid inadvertent transplantation of the disease to other susceptible populations of animals.     

Effect of stocking density,oxygen level,light regime and swimming velocity on the incidence of sexual maturation in adult Atlantic salmon (Salmo salar)

The effects of various environmental parameters on sexual maturation of two sea-winter Atlantic salmon (Salmo salar) were tested in two separate experiments. In the first experiment Atlantic salmon with initial mean individual weight 1.5 kg (smolt 13 months before) were reared for 8 months from June to February at different oxygen levels and stocking densities using continuous light. Oxygen levels of 5–7, 7.5–9.5 and 10–12 mg O₂ l⁻¹ and stocking densities starting at about 20, 30 and 40 kg m⁻³ and increasing as the fish grew to 80–90 kg m⁻³ for the highest densities were tested in a factorial design. Only male fish matured, and incidence of maturation among males varied from 4.1% to 25% between tanks. The highest percentage of mature males was found in the tanks with low stocking density. No clear effect on oxygen level was found.The second experiment lasted 20 months from seawater transfer in May until the fish weighed 3.3–3.5 kg. Two water current speeds (14–16 and 20–24 cm s⁻¹) and two photoperiod regimes (LD 20:4) and continuous light (LL) were tested in a factorial design. Neither swimming velocity nor photoperiod affected growth rate. Continuous light reduced the incidence of sexual maturation. The average proportion of maturation among males was 8% and 25% under the LL and LD 20:4 regimes respectively. The fish reared under the LD 20:4 light regime had a significant lower condition factor and significant larger hearts than the fish reared under continuous light. Swimming velocity had no significant effect on the incidence of maturation. The results indicate that the swimming velocity must be higher than 0.5 BL s⁻¹ in order to influence the energy stores. An important finding in this study is that light cues are not required for gonadal growth. The results also indicate that environmental factors can affect maturation even after the first sea-winter.     

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.     

A comparison of claw morphology and dominance between wild andcultivated male European lobster

Claw size and dominance in cultivated versus wild European lobsters Homarus gammarus were compared. Normally, lobsters develop a short, high and wide crusher and a slender scissor claw. In culture, both claws often develop into scissor claws. With growth, cultivated males developed one significantly elongated scissor claw (major claw), and one normal scissor claw, compared to wild males (minor claw). The differences increased with size. The wild males had higher claw index than cultured ones, due to the crusher claw. Wild lobsters with higher claw index were dominant. Cultivated males with claw indices at least 200 mm² higher than the opponent, won. Only scissor claws were broken in the encounters. Even if cultivated lobsters in time develop claws equal to wild lobsters, they might still be less robust. In the light of these findings, we suggest that lobsters cultivated for restocking purposes should be given access to an appropriate substrate allowing them to develop one claw into a crusher during the early benthic stage.     

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.     

Stimulation of crusher claw development in cultured lobsters, Homarus gammarus (L.)

Abstract. During the culture of large numbers of lobsters, Homarus gammarus (L.), it was noticed that more than half the animals lacked a distinct crusher claw. The majority bore two morphologically similar cutter claws even though their ages ranged up to 3 years (92mm carapace length). The proportion of 3-month-old juveniles (11–13 mm carapace length) bearing clearly differentiated crusher claws was increased from approximately 30% to over 80% by adding live oyster spat to the rearing chambers. The differentiation of the crusher claws was completed within approximately 4 moults (71–83 days) and was morphologically more pronounced in lobsters grown in the presence of spat than in the 30% of control lobsters which developed crusher claws spontaneously.