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One of the main challenges for spiny lobster aquaculture is the successful development of formulated feeds that are attractive, readily consumed by lobsters and promote optimal growth and survival. In a 54-day growth trial, we investigated the performance of four moist formulated feeds containing A) non-homogenised flesh ingredients; B) fish meal only; C) 10% krill meal; or D) homogenised flesh ingredients; and a reference diet of shucked blue mussel (Mytilus galloprovincialis) flesh, on growth, nutritional condition and feeding behaviour of juvenile tropical spiny lobster (Panulirus ornatus) reared either communally or individually. Growth and survival achieved by lobsters fed mussel were significantly higher than all other treatments. However, lobsters fed the formulated feed containing 10% krill meal (treatment C) and reared communally had a significantly higher growth, survival and feeding performance when compared to the formulated feeds with inclusion of non-homogenised and homogenised flesh ingredients (treatments A and D). The highest levels of feed interaction and pellet consumption among the formulated feeds were also recorded for treatment C. We demonstrated that the inclusion of krill meal in formulated feeds provides a benefit when compared to the inclusion of the flesh ingredients. Flesh ingredient format (homogenised or non-homogenised) had no effect on growth performance of lobsters, suggesting that the process of homogenisation of flesh ingredients does not provide any benefit in promoting feed consumption. Furthermore, time-series photography analysis trials showed that all the formulated feeds only promoted a feeding response within the first 2–3 h post-feeding, whereas mussel retained its attractiveness throughout the feeding period. These results suggest that the prolonged attractiveness remains an impediment for formulated feed performance in lobster culture. The present study also showed that growth performance and feeding response were higher in lobsters reared communally than individually. As observed in other spiny lobster species, it is likely that social interactions in communal housing may have provided cues that stimulated feeding responses and promoted higher growth rates.

Apparent digestibility and gastrointestinal evacuation rate were measured to assess the potential of five commercially available protein sources for their inclusion in feeds for juvenile slipper lobster, Thenus australiensis. Protein sources tested were fishmeal, krill meal, lupin meal, soybean meal and squid by-product meal. Apparent digestibility of crude protein ranged from 79.6% to 95.3%, with fishmeal protein significantly less digestible than lupin meal, squid by-product meal and soybean meal. Gastrointestinal evacuation rate was estimated from marker replacement, where yttrium oxide replaced ytterbium oxide. Faeces were collected every 3 h for 48 h, and a kinetic model was used to calculate the rate and time for the second marker to replace the first marker. Gastrointestinal evacuation (≥ 95%) was completed between 4 and 6 h with no significant differences among protein sources. Faeces consisted of both markers in equal parts 2.7 to 5.0 h after the feed switch, with lupin meal reaching the midpoint significantly faster than squid by-product meal and reference feed. The present study is the first in crustaceans to examine the relationship between apparent digestibility and gastrointestinal evacuation, showing more digestible protein sources had slower evacuation rates. The combined approach provides deeper insight into crustaceans' digestive physiology and helps understand their ability to digest specific ingredients. Further research is recommended to understand protein requirements in a broader context to verify highly digestible protein sources meet all nutritional requirements.

We examined the effects of temperature on the growth, feeding, nutritional condition and aerobic metabolism of juvenile spiny lobster, Sagmariasus verreauxi, in order to determine if temperature acclimated aerobic scope correlates with optimum for growth and to establish the thermal tolerance window for this emerging aquaculture species. Juvenile lobsters (initial weight = 10.95 ± 0.47 g) were reared (n = 7) at temperatures from 11.0 to 28.5 °C for 145 days. All lobsters survived from 14.5 to 25.0 °C while survival was reduced at 11.0 °C (86%) and all lobsters died at 28.5 °C. Lobster specific growth rate and specific feed consumption displayed a unimodal response with temperature, peaking at 21.5 °C. Lobster standard, routine and maximum metabolic rates, and aerobic scope all increased exponentially up to maximum non-lethal temperature. Optimum temperature for growth did not correspond to that for maximum aerobic scope suggesting that aerobic scope is not an effective predictor of the thermal optimum of spiny lobsters. Plateauing of specific feed consumption beyond 21.5 °C suggests that temperature dependent growth of lobsters is limited by capacity to ingest or digest sufficient food to meet increasing maintenance metabolic demands at high temperatures. The nutritional condition of lobsters was not influenced by temperature and feed conversion ratio was improved at lower temperatures. These findings add to a growing body of evidence questioning the generality of aerobic scope to describe the physiological thermal boundaries of aquatic ectotherms and suggest that feed intake plays a crucial role in regulating performance at thermal extremes.

Simultaneous measurements of nitrogenous (ammonia and urea) excretion and respiratory gas (O2 and CO2) exchange provide a non-destructive stoichiometric bioenergetic approach to elucidate metabolic energy substrate use which has rarely been used with aquatic ectotherms due to previous difficulties in measuring total CO2 excretion. This study examined metabolic energy substrate use and specific dynamic action (SDA) in cultured spiny lobster, Sagmariasus verreauxi, of different nutritional status. SDA magnitude calculated by stoichiometry was compared to a traditional composite oxycalorific coefficient approach. Protein synthesis can account for a large part of SDA in aquatic ectotherms. This study used a protein synthesis inhibitor cycloheximide to investigate the contribution of cycloheximide-sensitive protein synthesis to SDA and the effect of cycloheximide on nitrogenous and CO2 excretion. Lobsters were subjected to five treatments: 2-day fasted juveniles sham injected with saline (FS treatment); 2-day fasted juveniles injected with cycloheximide (FC treatment); 10-day starved juveniles injected with cycloheximide (SC treatment); post-prandial juveniles fed squid Nototodarus sloanii (FED treatment) and; post-prandial juveniles injected with cycloheximide (FEDC treatment). Protein was the primary energy substrate (65% of oxygen consumption) for 2-day fasted juveniles, with lipid accounting for the remainder (35%). After 10-day starvation lipid became the main substrate, indicating lipid oxidation increased with extended fasting. Following feeding, protein contribution remained above 50%, while lipid (0–43%) and carbohydrate (0–37%) provided significant energy at different time periods, indicating besides protein appropriate proportions of non-protein ingredients are also essential to lobsters. SDA magnitude in FED and FEDC treatments estimated by the traditional approach was 10.5 and 0.4 J g−1, respectively, indicating S. verreauxi expended 96% of post-prandial energy on protein synthesis and that decapod protein synthesis can account for one of the highest proportions of SDA in aquatic ectotherms. SDA magnitude in the FED treatment evaluated by stoichiometry (12.6 J g−1) was comparable to the traditional approach. Interestingly, stoichiometry was not applicable in the FEDC treatment as the respiratory quotient exceeded the theoretical maximum under aerobic conditions. Cycloheximide did not affect CO2 excretion among all treatments or nitrogenous excretion among unfed treatments, while the post-treatment total nitrogenous excretion reduced in fed lobsters. The combined measurement of substrate use and SDA potentially helps optimize the feed to achieve sustainable aquaculture. However, more research is required to decipher limitations and the applicability of stoichiometry for crustaceans.

Following recent advances in hatchery technology and large-scale larval rearing of spiny and slipper lobsters, a greater understanding of key nutritional requirements is now imperative to facilitate feed development for juvenile culture. However, there is a lack of relevant information available for the slipper lobsters, particularly Thenus species. This study sought to evaluate the potential requirements for and effects of a fresh ingredient component in a formulated feed on the growth performance of hatchery-reared juvenile Thenus australiensis. This was assessed using six formulated experimental feeds incorporating fresh blue mussel flesh (BM; Mytilus galloprovincialis) in a geometric series (0, 1.6, 3.1, 6.3, 12.5 and 25.0% dry matter) administered continuously over 9 weeks. An additional dietary treatment of blue mussel half shells (BMHS) was included as a reference feed to establish a benchmark of growth potential. Survival and moult frequency were unaffected by feed treatment. Lobsters fed BMHS displayed a clustered or synchronised moulting pattern with two major moulting events lasting several days each during the experiment. In contrast, lobsters provided experimental feeds moulted continuously throughout the experiment. The BMHS produced approximately 2-fold greater growth compared to experimental feeds, while BM incorporated into experimental feeds had no beneficial effect on growth at any inclusion level. Growth mirrored feed intake where it was also found that feed intake on a dry matter basis was approximately 2-fold higher for BMHS compared to experimental feeds, while biological feed conversion ratios were similar for all feeds. Thus, dry matter intake appeared to be primarily responsible for the difference in growth rates achieved. Bulk chemical analysis revealed that BMHS-fed lobsters had significantly lower ash content coupled with higher gross energy, total lipid and polar lipid contents on a proportional basis compared to lobsters fed formulated experimental feeds. Lobster haemolymph Brix values were also significantly higher in the BMHS treatment lobsters. Higher Brix coupled with decreasing feed intake suggests these lobsters were on average at a more advanced stage within the moult cycle and offers a possible explanation for differences in body chemistry. In conclusion, while growth rates were lower in animals fed formulated feeds compared to benchmark growth performance, overall survival, moulting and growth performance revealed the potential of the basal experimental feed formulation as a reference for future nutrition research with this species without a requirement for inclusion of fresh BM. The research highlights that significant opportunities exist to improve slipper lobster growth performance through maximising feed intake.

The moult cycle is arguably the most critical aspect of crustacean biology and is associated with dramatic changes in behaviour, physiology and condition. Here we describe the first detailed investigation of the combined changes in morphology, physiological status and nutritional condition over the moult cycle of juvenile T. australiensis. Haemolymph refractive index (measured as Brix) was evaluated as a non-destructive method for predicting physiological status and nutritional condition. Post-moult, inter-moult and pre-moult stages were identifiable by microscopic examination of the pleopod distal tips, though differentiation of the pre-moult substages was not possible using this technique. Monitoring of ecdysial suture lines on the exoskeleton gill chambers was found to be highly useful for visually determining progression through the pre-moult stage and predicting the timing of ecdysis. A classical pattern of inter-moult growth was observed where size and wet weight remained relatively uniform over the moult cycle while highly significant changes in whole-body composition were simultaneously observed over time. Growth was most evident by changes in dry weight and dry matter content which more than doubled by the onset of pre-moult. Changes in dry matter content were generally mirrored by Brix and whole-body crude protein, total lipid and gross energy content. Brix strongly correlated with dry matter content and significant correlations were also found for all other primary measures of nutritional condition. Typical moult-related changes were also found for circulating ecdysteroids. This study clearly demonstrates pronounced cyclical changes in physiology and condition of juvenile T. australiensis over a typical moult cycle. The significant correlations between haemolymph and whole-body composition validates Brix as a practical and non-destructive method to objectively assess physiological status, nutritional condition and quality in T. australiensis and further demonstrates its potential for individual crustacean assessment in experimental research and practical commercial applications.

Understanding the nutrition of lobster larvae through the examination of growth and biochemical composition across different life stages is a critical component of aquafeed development of new aquaculture species. Therefore, in the present study, we benchmarked growth and changes in biochemical composition of Thenus australiensis from first larval stage (S1) to the juvenile first stage (J1). The larval cycle was completed in a maximum duration of 31 d and comprised four successive larval stages followed by a post-larvae stage (nisto) and a subsequent moult to J1. Growth during all larval stages, metamorphosis to nisto, and moult to J1 were tracked through the measurement of size (total length, TL and cephalic/carapace width, CW), individual wet (WW) and dry (DW) weights. Bulk samples of all developmental stages were collected and analysed for ash, crude protein, total lipid, nitrogen free extract (NFE) and gross energy of dry matter (DM). Lipid class, fatty acid and mineral composition of S1, S4 and J1 of DM were also measured to provide more detailed analysis of composition. As expected, TL, CW, WW and DW increased with each subsequent stage except for lower TL and CW of the nisto stage when compared to S4 larvae. The DW increases throughout larval development until nisto and was defined by higher ash, crude protein, total lipid and NFE absolute amounts. However, from nisto to J1, total lipid decreased by half. The total lipid of DM increased as larval stages progressed to the nisto phase, declining rapidly when monitored at J1. The accumulation of lipid during the larval phase highlights the importance of building lipid stores to maintain metabolism during the non-feeding nisto stage and moult to J1. Polar lipid was the dominant lipid group in comparison to neutral lipids stores. The energy content of larvae, nisto and J1 reflected the accumulation of lipid over the larval stages and its depletion during the non-feeding nisto stage. The environmental influence on elemental uptake was evident at the moult to J1 with a >4-fold increase in ash content in individual J1 compared to nisto. This was supported by an increase of major mineral constituents of the exoskeleton, particularly, calcium. The present study is the first describing in detail the growth and biochemical composition of all the larval stages until J1 for T. australiensis. The new knowledge on nutrition will support progress in aquafeed development for this new aquaculture species.

The digestible protein (DP) and digestible energy (DE) requirements for maintenance and growth of brook trout (Salvelinus fontinalis) were determined using a factorial model at either optimum (15 °C) or elevated temperature (19 °C). Several key parameters of the factorial model were measured using a series of inter-related studies. The maintenance requirements for DP and DE were 0.10 gDP kg−0.69 day−1 (15 °C) and 0.31 gDP kg−0.78 day−1 (19 °C), and 34.86 kJDE kg−0.84 day−1 (15 °C) and 46.14 kJDE kg−0.86 day−1 (19 °C). The total requirements for DP were 0.10 gDP kg−0.69 day−1 + 2.14PG (protein gain) (15 °C) and 0.31 gDP kg−0.78 day−1 + 1.98PG (19 °C). The total requirements for DE were 36.86 kJDE kg−0.84 day−1 + 1.58EG (energy gain) (15 °C) and 46.14 kJDE kg−0.86 day−1 + 1.64EG (19 °C). The partial efficiencies for growth were 0.47 (15 °C) and 0.51 (19 °C) for protein, and 0.63 (15 °C) and 0.61 (19 °C) for energy. Nutrient gain was lower at the elevated temperature; however, feed formulation for brook trout should be adjusted to match changes in nutrient requirements at different culture temperatures. The protein and energy requirements model will be useful for developing commercial feeds and feeding charts for brook trout.

Rapid non-invasive monitoring of spiny lobster nutritional condition has considerable application in the established fishery, live market and prospective aquaculture. The aim of this research was to test the feasibility of near-infrared spectroscopy (NIRS) as a novel non-invasive tool to assess the nutritional condition of three lobster species. Lobster (n = 92) abdominal muscle dry matter (AMDM) and carbon content (AMC) correlated significantly with indices of nutritional condition including hepatopancreas dry matter (HPDM; rho = 0.83, 0.78), total lipid content (HPTL; rho = 0.85, 0.87) and haemolymph total protein (TP; rho = 0.89, 0.87 respectively). Abdominal muscle nitrogen content (AMN) was a poor correlate of nutritional condition. Models based on FT-NIR scanning of whole lobster tails successfully predicted AMDM, AMN and AMC (RMSECV = 1.41%, 0.35% and 0.91%; R2 = 0.75, 0.65, 0.77, respectively), and to a lower accuracy HPDM, HPTL and TP (RMSECV = 6.22%, 8.37%, 18.4 g l-1; R2 = 0.51, 0.70, 0.83, respectively). NIRS was applied successfully to assess the condition of spiny lobsters non-invasively. This pilot study paves the way for the development of crustacean condition models using portable non-invasive devices in the laboratory or in the field.

Southern bluefin tuna (Thunnus maccoyii) ranching in South Australia is one of the most valuable finfish aquaculture industries in Australia. This industry is currently highly reliant upon the use of baitfish; however commercial pelleted diets for this species are now available. Despite the economic importance of these animals there is a general lack of knowledge regarding the digestive physiology of southern bluefin tuna. Measurement of the digestive enzymes trypsin (T), chymotrypsin (C) and calculation of T:C ratios are particularly useful in the assessment of nutritional status in fish. In this study T and C activities were measured in ranched tuna fed a vitamin (Vit) and vitamin + immunostimulant (Vit + Imm) supplemented baitfish diet for 8 weeks. Differences relating to the addition of the supplements were not observed for T, C or T:C ratios suggesting that the supplementation rates did not affect the nutritional status of the tuna or the quality of the baitfish. Trypsin activity plays a key role in the secretion of chymotrypsin and in this study a significant correlation between these enzymes was found. T, C and T:C were not associated with caecum somatic index, caecum pH, caecum temperature, stomach pH or stomach temperature. Although T and C activities are highly sensitive to feeding, activities of these enzymes did not appear to be affected by the presence of baitfish in the stomach. The presence of baitfish did not appear to affect caecum pH, caecum temperature or stomach temperature. Therefore all data were pooled and a significant correlation between caecum and stomach temperature, explained by the endothermic physiology of tuna, was observed. Significantly higher stomach pH values were associated with the presence of baitfish and an inverse relationship between stomach pH and stomach temperature was found in fish with empty stomachs but not those that had eaten. These results are indicative of a digestive strategy which employs maintenance of low stomach pH for rapid digestion of a meal. This study represents the first report of digestive enzyme activities and nutritional status for captive southern bluefin tuna fed a standard and modified baitfish diet. In addition to a better understanding of digestive physiology, these results, in combination with the physiological measures of feeding and digestion, will significantly contribute to the further development of an in vitro digestive model for this species. This model will significantly improve the abilities of the Australian southern bluefin tuna industry to assess the predicted digestibility of commercially produced pelleted diets as well as screen novel dietary ingredients prior to full scale and often commercially expensive in vivo trials.

For aquatic ectotherms, increasing water temperatures cause an exponential increase in metabolic rate and decreasing oxygen solubility. Fish species that regulate their metabolic rate to low dissolved oxygen concentrations are understood to be hypoxia tolerant whereas salmonid fish are considered to be classic metabolic conformers and their metabolic rate is dependent on the environmental oxygen concentration. This study examined Atlantic salmon, Salmo salar , undergoing a progressive hypoxia at optimal temperatures and at temperatures nearing the upper thermal tolerance limit for the species to determine if metabolic regulation occurred. Oxygen consumption was measured on individual Atlantic salmon (150.7 ± 40.8 g) in 66-L static respirometers; oxygen measurements were taken every 5 min until the fish lost equilibrium. Metabolic regulation was observed at all temperatures and occurred in 67, 50 and 50% of the fish at 14, 18 and 22 °C, respectively. The plateau metabolic rate (VO 2PL ) was 293.4 ± 24.5 mg·kg·h − 1 at 22 °C which was significantly higher than in the 14 and 18 °C treatments (191.1 ± 24.5 and 203.9 ± 12.6 mg·kg·h − 1 , respectively). This difference was also reflected in the critical oxygen threshold (P crit ) where the value for the 22 °C treatment (4.59 ± 0.32 mg·L − 1 ) was significantly higher than those of the 14 and 18 °C treatments (3.46 ± 0.14 and 3.39 ± 0.26 mg·L − 1 respectively). These results indicate that some fish from the Tasmanian population of Atlantic salmon have the ability to regulate metabolic rate to low oxygen concentrations and therefore show a relatively high degree of hypoxia tolerance.

The effects on group feed intake and growth performance of changing feeding frequency simultaneously with seawater transfer of Atlantic salmon Salmo salar were investigated. Two feeding regimes of one feed per day (1F) and eight feeds per day (8F) were compared for groups of Atlantic salmon in freshwater. Following seawater transfer groups were either fed on their pre-transfer regimes or swapped to the other regime, resulting in four treatments (n = 3). Regardless of the pre-transfer feeding regime, 1F groups had significantly (P < 0.05) lower feed intake immediately following transfer than 8F groups. However, groups that underwent a change in feeding frequency did not have significantly lower feed intake immediately following transfer than those kept on the pre-transfer feeding regime. During the freshwater phase, overall mean feed intake of 8F groups was significantly greater than 1F groups, whilst there was no significant difference in mean feed intake for any of the treatments during the seawater phase. Growth was better in groups fed 8F in freshwater than those fed 1F in freshwater regardless of post-transfer feeding regime. There were no significant differences in growth depensation throughout the experiment, suggesting that there were no overall differences in hierarchy strength amongst treatments. The main finding of this experiment was that a single meal per day immediately following seawater transfer results in initially significantly lower feed intake than the higher feeding frequency regardless of pre-transfer feeding regime, consequently multiple daily feeds is the recommended feeding regime following seawater transfer.

The efficacy of photoperiod manipulation to influence growth and developmental processes is well documented in a range of temperate aquaculture species. However, the application of such techniques with tropical species requires further investigation. This preliminary 20-day study investigated the influence of continuous photoperiod on growth of barramundi (Lates calcarifer). In addition, diel plasma melatonin profiles provided a physiological measure of how the endocrine system of barramundi responded to continuous photoperiod. Juvenile barramundi (1.33 ± 0.02 g) were held in recirculation systems under 12-h light: 12-h dark (12L:12D) or 24-h light (24L:0D) with a light intensity of 1,000 lux throughout the water column. Fish from both treatments grew to more than 14 times their original weight, with final weight (24L:0D = 21.59 ± 0.85 g; 12L:12D = 19.12 ± 0.55 g), total length (24L:0D = 12.67 ± 0.14 cm; 12L:12D = 11.96 ± 0.13 cm) and specific growth rate (24L:0D = 9.60 ± 0.05% bw day−1; 12L:12D = 9.14 ± 0.06% bw day−1) being significantly higher for fish grown on 24L:0D compared with 12L:12D. There were no significant differences in feed intake (24L:0D = 226.46 ± 6.27 g; 12L:12D = 219.02 ± 5.73 g) or feed conversion ratio (24L:0D = 0.71 ± 0.06; 12L:12D = 0.80 ± 0.07) between light treatments. Barramundi held under 12L:12D exhibited diel melatonin secretion, which peaked mid-dark phase (171.83 ± 4.81 pg ml−1) followed by a gradual decrease in base levels at the onset of illumination (68.61 ± 8.77 pg ml−1). When juvenile barramundi were subjected to 24L:0D, the amplitude of peak melatonin secretion was significantly suppressed during the subjective mid-dark phase (129.71 ± 2.36 pg ml−1). This preliminary study confirmed that barramundi respond to photoperiod manipulation in a similar manner to many temperate fish species, thus demonstrating the future potential use of artificial lighting to improve growth in this species commercially.

This study investigated the efficiency of lysine utilisation for liveweight gain (LG), protein gain (PG) and lysine gain (LysG) in Atlantic salmon (Salmo salar L.) parr fed a diet with a high digestible protein (DP) to digestible energy (DE) ratio. Twelve diets containing 10.15 to 20.79 g dietary digestible lysine (DDLys) kg−1 at a constant 25.0 g DPMJ DE−1 (25.0 DP DE−1) were fed at a fixed ration for 50 days. With increasing DDLys there was a significant (Pb0.001) linear increase in LG. Whole-body crude protein and lysine content increased with increasing wet weight (W), with weight exponents b (Wb) of 1.58 and 2.47, respectively. There were significant linear relationships between digestible lysine intake (DLysI) and LG, PG and LysG. The relationship between DLysI and LysG predicted a maintenance lysine requirement of 7.7 mg kg−0.75 d−1 and an efficiency of 77% for lysine utilisation for lysine gain above maintenance lysine intake. To further examine the effect of the DP DE ratio on lysine utilisation comparison was made to a similar study that used a lower DP DE ratio of 19.8 DP DE−1. Comparison between linear relationships for LG, PG and LysG from the two experiments showed that there were no significant differences between the efficiency of lysine utilisation (slopes) for LG, PG or LysG, nor were there significant differences between the elevations for PG and LysG. This study demonstrated that at two fixed but different protein and energy intakes the dietary DP DE ratio did not influence the efficiency of lysine utilisation for lysine gain over a range of dietary lysine and digestible lysine intakes.

The striped trumpeter, Latris lineata, is a native fish being developed for aquaculture in Tasmania, Australia. Striped trumpeter have a long postlarval stage and rearing has been reliant on the long-term use of Artemia. Two experiments were conducted to investigate weaning strategies. The first experiment used 52 d posthatch (dph) postlarvae previously reared on Artemia from 16 to 52 dph enriched with either low or high ascorbic acid. The treatments were Artemia, a microdiet, or cofeeding. The postlarvae were reared until 67 dph. The Artemia treatment yielded significantly higher mean survival, followed by cofeeding, and the microdiet. Feeding Artemia yielded significantly heavier postlarvae and the microdiet produced significantly smaller postlarvae. A second experiment used 41 dph postlarvae and investigated the effect of cofeeding duration prior to feeding with Artemia and microdiet as controls. Cofeeding periods of 5, 10, and 15 d were tested. Cofeeding for 5 d and microdiet feeding yielded significantly poorer survival compared with Artemia. Artemia feeding yielded significantly heavier postlarvae. In both experiments, the diets did not have a significant effect on jaw morphology. These experiments are the first to examine weaning strategies for striped trumpeter postlarvae and suggest cofeeding postlarvae from 40 dph and feeding microdiet exclusively at 50 dph.

The experiment aimed to measure post-prandial protein synthesis at three different temperatures. Juvenile barramundi (10.81+/-3.46 g) were held at 21, 27 and 33 degrees C and fed to satiation daily. Samples were taken over a 24h period at 0 (24h after the previous meal) and then at 4, 8, 12 and 24h after feeding to measure protein synthesis in the white muscle, liver and remaining carcass. Protein synthesis at 27 and 33 degrees C peaked 4h after feeding in all tissues and returned to pre-feeding rates by 12h. At 21 degrees C protein synthesis remained constant over 24h in all tissues. While the concentration of RNA remained stable over the 24h cycle and across temperatures, the ribosomal activity increased after feeding. This meant k(RNA), not the absolute amount of RNA, was the driving force underlying the post-prandial increase in protein synthesis. However, relative differences in protein synthesis between tissues were attributed to differences in RNA concentration. There was a significant positive relationship between white muscle and whole body protein synthesis. This was the first study to show an interaction between temperature and the time after feeding on protein synthesis for an ectotherm, and that a post-prandial peak in protein synthesis only occurred under optimum temperature conditions.

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).

Rates of protein synthesis were measured in the whole body and tissues of southern dumpling squid Euprymna tasmanica to validate the use of a flooding-dose of (3)H phenylalanine for the measurement of protein synthesis with different size squid and to make a preliminary investigation into the effects of feeding regime. In smaller (2.8+/-0.5 g, mean+/-SE) and larger (14.8+/-2.2 g) squid whole body fractional rates of protein synthesis were 9.45+/-1.21 and 1.49+/-0.29% d(-1), respectively. Differences in total whole body protein content meant there was no difference in absolute rates of whole body protein synthesis between the larger and smaller squid. In larger squid, fractional rates of protein synthesis were significantly higher in the digestive gland (9.24+/-1.63% d(-1)) than in the arm tissue (1.43+/-0.31% d(-1)), which were significantly higher than in the anterior (0.56+/-0.13% d(-1)) and posterior (0.36+/-0.04% d(-1)) mantle. In smaller squid there were no differences in protein synthesis between tissues and high individual variation, due to differences in feeding, was a likely cause. Consequently, the effect of feeding regime on protein synthesis was compared between two groups of individually held squid: daily-feeding and minimal-feeding squid. The daily-feeding squid had significantly higher feed intake, gained mass and had a significantly higher growth rate than the minimal-feeding squid which lost mass. Whole body protein synthesis was significantly higher in the daily-feeding squid as was the protein content of the digestive gland, anterior and posterior mantle. There were few other differences in indices of protein metabolism. Individual squid showed differences in growth and protein metabolism, and there were significant relationships between growth rate and both rates of protein synthesis and protein degradation. Thus, higher individual growth was a consequence of increased protein synthesis, decreased protein degradation and, therefore, increased efficiency of retaining synthesised protein.

This study investigated whether the efficiency of lysine utilisation for liveweight gain, protein gain and lysine gain was affected by feeding regime in Atlantic salmon (Salmo salar L.) parr. Twelve diets containing from 10.15 to 20.79 g dietary digestible lysine kg− 1 were hand-fed either to satiation or to a controlled fixed ration. The controlled ration was set to equal the feed intake of the basal (lowest) lysine diet so that any growth above that of the group fed the basal diet at the controlled ration was due entirely to the additional dietary lysine. For both feeding regimes, with increasing dietary lysine there were significant linear increases in liveweight gain (P < 0.001) and in protein (P < 0.001) and lysine (P < 0.01) concentration of liveweight gain. Increasing dietary lysine resulted in a significant (P < 0.001) linear increase in feed intake at satiation. Efficiency of lysine utilisation for liveweight gain above maintenance lysine intake was significantly (P < 0.005) higher at satiation than for the controlled ration: 47.7 compared to 34.9 mg liveweight gain per mg digestible lysine intake, respectively. However, feeding regime had no significant effect on the efficiency of lysine utilisation for protein or lysine gain. This study demonstrated that feed intake does not influence the efficiency of lysine utilisation for protein or lysine gain in Atlantic salmon parr. The change in weight-specific lysine composition suggests a robust physiological mechanism maintaining the efficiency of lysine utilisation for lysine gain in Atlantic salmon parr.

Temperature has a marked and direct effect on many of the key physiological processes in ectotherms, including fish. Results from two growth trials on juvenile barramundi (∼ 3–5 g) were used to model the effects of temperature on the feed intake and growth performance, measured as specific growth rate (SGR), productive protein value (PPV) and productive energy value (PEV), across temperatures 21–39 °C (at 3 °C intervals). There were no significant differences between the chemical composition of the fish reared at different temperatures. Optimal temperatures were determined from quadratic polynomials: maximum feed intake (g d − 1 ), maximum growth (SGR, % d − 1 ) and growth efficiency (PPV and PEV, %) occurred at 32.8, 31.4, 31.2 and 30.2 °C, respectively. These models also determined that maximum growth occurred approximately 4 °C higher then previously demonstrated. Feed intake, SGR and growth efficiency remained ≥ 90% of the maximum biological response over an 8 °C temperature range. These models suggest that juvenile barramundi are eurythermal and therefore maximize growth by adopting strategies to optimize nutrient utilization over as wide a temperature range as possible. Furthermore, the decrease in growth efficiency at extreme (high) temperature occurs over only a few degrees and highlights the upper thermal tolerance of barramundi.

Temperature is recognized to be the most important environmental factor affecting growth and protein synthesis in fish. The optimal temperature for growth of juvenile barramundi is 31 °C, although culture often occurs at temperatures which are above and below this optimum. Juveniles (2.96 ± 0.46 g) were held at five different temperatures ranging from 21 to 33 °C at 3 °C intervals. Fish were fed to satiation twice daily (504.5 g kg− 1 crude protein, 190.5 g kg− 1 lipid, 128.5 g kg− 1 ash, and 20.2 GE MJ kg− 1). Daily feed intake (g), growth (% d− 1), growth efficiency, and protein synthesis (measured 24 h after feeding) were determined for each temperature. Feed intake was significantly higher at 33 °C, than at any other temperature. Growth and growth efficiency were not significantly different between the 27, 30 and 33 °C groups but were significantly higher than the 21 and 24 °C groups. In order to take account of the variation in protein synthesis over the 24 h following feeding and model daily protein turnover, daily rates of protein synthesis were estimated from previously determined relationships between white muscle and whole body rates of protein synthesis. This showed that protein synthesis was not significantly different between 27 and 33 °C, synthesis retention efficiency was over 40% at these temperatures, and at 21 °C growth efficiency was poor. Growth efficiency and protein metabolism were optimal over a temperature from 27 to 33 °C.

This study aimed to compare nitrogen budgets for juvenile (1.17 ± 0.07 g, mean ± S.D.) big-bellied seahorses fed live, frozen and pelleted feeds and to examine the potential of non-destructive measurements of excretion to predict feed performance. Three feeds were tested against live Artemia: frozen mysid shrimp species (Paramesopodopsis rufa, Tasmanomysis oculata,Tenagomysis sp.), a pellet prepared from the mysid shrimps and a commercial crumbled feed. Nitrogen budgets were constructed from nitrogen retention measured over a 30 day growth experiment, ammonia and urea excretion measured over 24 h on days 15 and 30, and nitrogen digestibility. After 30 days seahorses fed Artemia and frozen mysid had significantly (P

This study investigated the effects of 100 g/kg increments of crude protein (approx. 250 (P25) to 550 (P55) g/kg of crude protein) in paired iso-energetic diets on the growth performance of the juvenile Australian short-finned eel (1·83 (s.e. 0·01) g average wet weight). The highest growth response was obtained with treatment P45 followed by P35, P55 and P25. It appeared that food efficiency ratio (FER) increased with increasing crude protein content in low energy diets (treatments P25 and P35). However, 100 g/kg increase in dietary crude protein content (from 450 to 550 kg crude protein per kg diet) in high energy diets resulted in lower FER for treatment P55 than for the treatment P45. The protein efficiency ratio (PER, %) was higher in low protein:low energy diets (treatments P25 and P35) than that of high protein:high energy diets (treatments P45 and P55). The protein productive values (PPV, %) for treatments followed a similar trend to PER in this experiment. The lowest PPV was obtained by the treatment P55 and it was significantly different from that of the other three treatments. A proportional increase in dietary crude protein content in paired iso-energetic diets did not significantly change the whole body protein content. However, a small increase in whole body protein content with increasing dietary crude protein in each group was detected. In conclusion, the present study showed protein sparing effects of lipids and carbohydrates in the diets of the short-finned eel. Further studies specifically investigating the effects of dietary carbohydrate to lipid ratios at different protein levels would improve diet formulation and reduce nutrient impact in intensive recirculation systems.

Temperature is recognized to be the most important environmental factor affecting growth in fish. Barramundi are cultured over a wide range of temperatures and extreme high temperatures which they can experience under culture approach the upper thermal tolerance limit for this species. A growth trial was conducted on juvenile barramundi to examine the effects of high temperatures ranging from the minimum optimal temperature (27 degrees C) for growth efficiency to the extreme upper thermal limits (39 degrees C) for feed intake, growth and growth efficiency. Juveniles (4.87 plus or minus 0.32 g) were held at four different temperatures 27, 33, 36 and 39 degrees C and fed twice daily to satiation (503.5 g kg-1 crude protein, 182.5 g kg-1 lipid, 150.1 g kg-1 ash, 20.52 GE MJ kg-1). Feed intake (g per day) and SGR (% per day) increased with increasing temperature up to 36 degrees C. At 39 degrees C feed intake, growth, feed efficiency ratio, protein efficiency ratio and productive energy value were significantly lower than at the other temperatures. This demonstrates that growth was optimized at temperatures from 27 to 36 degrees C and that barramundi have a much wider range for maximum growth efficiency than preciously thought.

In this experiment, 23% of fish meal protein was replaced with protein from Australian soybean meal (SBM), lupin meal (LM), corn gluten meal (CGM) and meat meal (MM) in nutritionally balanced experimental diets. Growth and growth efficiencies of juvenile Australian short-finned eel Anguilla australis australis (Richardson) elvers (2.23 ± 0.4-g average wet weight) were compared Elvers were fed twice a day to a total of 5% body weight per day for 63 days. Total weight gain (g), specific growth rate (% day-1), protein efficiency ratio (%) and productive protein value (%) were significantly higher (P < 0.05) for elvers fed the MM diet than for those fed the LM diet. There were no differences in diurnal ammonia-nitrogen excretion rates. However, diurnal urea-nitrogen excretion rates were significantly (P < 0.05) affected by diet and rates were two to three times higher for all diets, except CGM, 4 h following the afternoon feed. Diet significantly affected apparent digestibility (AD); ADs of protein for SBM and LM were significantly (P < 0.001) higher than for control diet, CGM and MM; AD of energy for LM was significantly (P < 0.05) lower than for all the other diets. Fish meal protein was replaced by CGM, SBM and MM without compromising growth rates of the Australian short-finned eel. However, whole lupin seed meal (LM) depressed growth and growth efficiencies most likely because of the high indigestible carbohydrate content. © 2005 Blackwell Publishing Ltd.

The experiment aimed to examine the effect of changing feeds on individual feed intake and feeding and dominance ranks in groups of African catfish. Following feeding on a commercial feed (Com.) groups (n = 3) of 6 catfish were either fed fish meal (FM42) or maize gluten (MG35) based feeds for 5 days before being switched to the other feed for 5 days. Energy intake was significantly lower on FM42 than on MG35, dry matter intake and protein intake were significantly lower on FM42 than on Com. and this occurred whether FM42 was fed first or second. There were no significant differences between intake of MG35 and Com. Thus, the action of changing the feed on its own did not affect feed intake since the decrease was shown to be feed-specific to FM42. Six types of agonistic behaviours were identified and used to assign dominance rank, there were no correlations between dominance and feeding ranks. This was due to non-linear hierarchies with one dominant fish in each group. Feeding ranks were more stable when feeding MG35 than FM42. Feeding rank stability (Kendall's coefficient of concordance) was significant in 5 out of 6 groups fed MG35 (compared with 3 out of 6 fed FM42). Feeding rank stability was higher in 5 out of the 6 groups when they were fed MG35 than when the same group was fed FM42. The experiment provided evidence that the introduction of a novel feed can, but does not necessarily, alter feed intake and that feed can influence the stability of feeding ranks.

The effect of phytase supplementation to a canola-meal-based diet on phosphorus utilisation in Atlantic salmon was studied in a two-by-two factorial design. Diets were prepared without phytase or inorganic phosphorus supplementation, with phytase, with supplemental inorganic phosphorus and with both phytase and supplemental inorganic phosphorus. Available phosphorus was set below requirement and the total phosphorus set to meet requirements for salmonids. After 12 weeks, there were no significant differences in survival, feed intake and weight gain between diets. There was an interaction effect between supplements on bone ash, bone phosphorus and whole-body phosphorus so that adding phytase, inorganic phosphorus, or both resulted in significantly (P

A recently developed radioimmunoassay (RIA) for measuring insulin-like growth factor (IGF-I) in a variety of fish species was used to investigate the correlation between growth rate and circulating IGF-I concentrations of barramundi (Lates calcarifer), Atlantic salmon (Salmo salar) and Southern Bluefin tuna (Thunnus maccoyii). Plasma IGF-I concentration significantly increased with increasing ration size in barramundi and IGF-I concentration was positively correlated to growth rates obtained in Atlantic salmon (r2=0.67) and barramundi (r2=0.65) when fed a variety of diet formulations. IGF-I was also positively correlated to protein concentration (r2=0.59). This evidence suggested that measuring IGF-I concentration may provide a useful tool for monitoring fish growth rate and also as a method to rapidly assess different aquaculture diets. However, no such correlation was demonstrated in the tuna study probably due to seasonal cooling of sea surface temperature shortly before blood was sampled. Thus, some recommendations for the design and sampling strategy of nutritional trials where IGF-I concentrations are measured are discussed

The replacement of fish oil with a dried product made from thraustochytrid culture, a marine microorganism, in canola-oil-based diets for Atlantic salmon was investigated. Salmon (37 g) were fed for 51 days on diets containing only canola oil, canola oil and fish oil, or canola oil and the thraustochytrid. There were no significant differences in final weight (106.1 +/- 1.1 g), weight gain (69.6 +/- 1.1 g), feed consumption (16.5 +/- 0.2 mg dry matter g(-1) d(-1)), feed efficiency ratio (1.15 +/- 0.03 g (g-1)), or productive protein value (51.2% +/- 1.7%) between the diets. Nor were there any significant differences in whole-body chemical composition, organ somatic indices, or measures of immune function. However, following transfer to seawater and 2 challenges with Vibrio anguillarum, cumulative mortality was significantly lower in fish fed some fish oil than in those fed the 2 diets containing no fish oil. In conclusion, the thraustochytrid had no detrimental effects on the performance of salmon but, at the current inclusion of 10%, failed to confer the same effect as fish oil under challenging conditions.

The consequences of photothermal manipulation of reproduction in Jasus edwardsii broodstock on the morphology of newly hatched larvae and their biochemical characteristics were examined. The treatment of compressed temperature and photoperiod delayed the time of moult, mating and egg extrusion, but reduced the period until larval hatch, and reduced the hatching duration in individual females compared to the ambient treatment of simulated natural photoperiod and water temperature. Thus, the availability of phyllosoma for hatchery rearing was extended. However, the broodstock in the compressed treatment produced smaller phyllosoma and more larvae failed to develop beyond the naupliosoma stage than animals from the ambient cycle. Phyllosoma from the compressed treatment contained a higher proportion of polar and triacylglycerol lipid classes, lower wax esters, elevated levels of the essential fatty acid docosahexaenoic acid, a higher ratio of n-3/n-6 fatty acids, and lower levels of ascorbic acid. The changes in larvae from the compressed treatment may adversely affect their viability, and are probably due to the higher water temperatures experienced during late embryonic development.

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.

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).

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.

Fish meal is the most widely used protein source in commercial eel foods and information on the nutritive value of more economical protein sources is needed in order to improve cost-effectiveness of diets. This investigation was conducted to determine apparent digestibility coefficients of available plant and animal meals for juvenile Australian short-finned eel (Anguilla australis australis, Richardson). The suitability of a modified Guelph-type settlement faecal collector in eel digestibility studies was assessed. Animal by-product (spray-dried meat solubles; blood meal; high fat poultry meal) and plant protein (soya bean; canola; maize gluten; lupin; field pea) meals were mixed with a reference diet and marker (0·3: 0·69: 0·01) and the resultant test diets given to the juvenile eels (3·15 (s.e. 0·42) g) at 0·05 live weight per day. The reference diet and all the test diets were well accepted by the fish. Apparent digestibility coefficients for crude protein (ADCCP) for maize gluten meal (MGM), lupin meal (LM) and blood meal (BM) were found to be 0·97, 0·96 and 0·96 respectively and they were significantly (P < 0·001) higher than that for the other ingredients. However, apparent digestibilities for dry matter (ADCDM) and energy (ADCkJ) were significantly (P < 0·0001) higher for animal by-products than for plant proteins except for maize gluten meal. This was explained by the higher content of nitrogen free extractives in the former plant proteins. There was a strong positive correlation between ADCDM and ADCkJ for all ingredients (P < 0·01). Weaker positive correlations were also found between ADCCP and ADCDM and between ADCCP and ADCkJ. Similar results obtained for warm water species using similar faecal collection techniques and over limited eel digestibility data support the suitability of the modified Guelph-type settlement collector system in digestibility studies with juvenile eels.

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

The growth, condition, and feed utilization patterns of juvenile southern bluefin tuna (SBT) fed moist-pellets were examined over a 19-wk period from March to July 1999. The SBT had significant weight gain over the course of the study, increasing on average from about 27 to 34 kg (dependent on size class). No significant weight gain by the SBT occurred in the first 5 wk of the study. Following this initial period of slow growth, the rate of weight gain increased, ranging between 40 to 90 g/d. Weight gain peaked after 11 wk, with no further gain occurring after this time point. Weight gain was strongly related to average daily feed intake (AFI) which was predominantly influenced by water temperature. Weight gain was minimal following the decrease of water temperatures below 15 C, consistent with a decrease in feed intake from peak values at the beginning of the study to basal levels by week 13. Basal feeding levels were maintained for the remainder of the study through to week 19. Although water temperature and AFI were strongly related, other time related effects also appeared to be signillcant. A relationship between condition index and feed intake was also identified. Condition index of the SBT increased from about 19 kg/m3 to 22 kg/m3 over the 19-wk period. Similar to the patterns observed in growth, there was also an initial delay in increases of condition index. The results from this study support that the majority of weight gain by juvenile SBT occurs during the early part of the production season and that this is most likely influenced indirectly through responses to water temperature. The results of this study also suggest that there is little value in conducting growth trials beyond the point where water temperatures decrease below 15 C. Although there was minimal weight gain or improvement in condition beyond the 11-wk time point, these parameters would need to be considered in conjunction with flesh quality characteristics to identify optimum harvesting regimes.

The utilization of dehulled lupin as a partial replacement for fish meal was studied in diets of rainbow trout. Fish were fed diets with 0%, 10%, 20%, 30%, 40% and 50% of dehulled lupin, at a daily feeding rate of 2% body weight for 8 weeks at 15 ± 0.5 °C. Growth performance generally decreased with increasing dehulled lupin in the diet (R2 = 0.81, P

Development of a formulated pellet to replace ‘bait’ fish in farmed southern bluefin tuna (SBT), Thunnus maccoyii (Castelnau), feeds is in progress; however, inherent difficulties have been encountered in conducting large-scale growth trials to evaluate experimental pellet quality. Consequently, alternative methods are being investigated to develop a suitable feed more rapidly. This work explored whether Atlantic salmon, Salmo salar L., could be used as a ‘surrogate’ species for nutrition research on SBT by screening experimental SBT feeds. Atlantic salmon (initial mean weight 161.4 g) were fed a commercial salmon feed (Com.Sal), a commercial northern bluefin tuna feed (Com.NBT), one of three experimental SBT feeds (CRC-A, -B, -C) or dry pelleted pilchards for 42 days, at which time growth was assessed. In vivo and in vitro protein digestibility of the feeds was also evaluated. Weight gain of Atlantic salmon fed Com.Sal (99.8 g) and Com.NBT (93.5 g) were found to be significantly (P

This study aimed to measure protein synthesis and growth performance in flatfish, Rhombosolea tapirina, fed on three feeding regimes: 1% body wt. fed in the morning (MM1); 2% body wt. fed in the morning (MM2) and 2% body wt. fed in equal amounts in the morning and in the afternoon (MA2). After 6 weeks there were no significant differences in wet wt., protein growth or efficiency of protein-nitrogen flux. Significantly lower protein consumption on MM1 resulted in significantly lower rates of protein synthesis and degradation compared with MM2 but not MA2. After 18 weeks there were still no significant differences between feeding regimes although trends in growth and efficiency reflected the situation after 6 weeks. Fish were maintained individually, and when analysed on this basis, there were significant relationships between protein consumption and protein synthesis [k(s)=0.92, k(r)+1.16 (n=17; r(2)=0.49; P

This study was undertaken to assess whether collection of faeces by a stripping method was suitable for measuring digestibility in large seawater Atlantic salmon of up to 5 kg. Experiments were conducted to determine the effects on the apparent digestibility coefficient (ADC) of faecal collection technique, urine and mucus contamination of faecal samples, immediate repeated sampling on individuals, stripping pressure during the collection of faeces, dorso-flexion of the tail prior to faecal sample collection, variation between individual fish and section of gut sampled. Faecal collection by rectal suction and dissection was compared with the stripping collection method. Rectal suction produced comparable results to stripping; however, ADC for crude protein was significantly ( P P P

Many studies with fin fish have demonstrated the potential to use alternative dietary protein sources to fish meal based on growth responses, although these trials mostly neglect to determine if such protein sources affect immune function. This study investigated the effect of fish meal replacement with dehulled lupin meal (LPN) or hydrolysed poultry feather meal (FTH). Atlantic salmon (Salmo salarL.) parr were supplied isonitrogenous and isoenergetic diets with 40% of the dietary protein provided by LPN or FTH, or 400 g/kg of the dietary protein provided equally by LPN and FTH (MIX). A diet mainly containing fish-meal protein acted as a control (CON). Growth, immune function, blood chemistry and disease resistance were assessed after 56 days. Significant differences (P< 0·05) in weight gain were detected between Atlantic salmon given the CON and FTH diets, whilst those salmon given LPN and MIX did not differ from any other. Productive protein values were significantly lower (P< 0·01) for salmon on FTH compared with those on CON and MIX. Immune function (as assessed by lysozyme, antiprotease, neutrophil oxygen radical production and plasma total immunoglobulin) and blood chemistry (as assessed by plasma total protein and glucose) were not significantly (P> 0·05) affected by any diet. Mortality rates of Atlantic salmon challenged with Vibrio anguillarum were not influenced by diet. These data suggest Atlantic salmon could be supplied diets with the fish meal component reduced to supply approximately 600 g/kg of the total protein, with the remaining 400 g/kg supplied by dehulled lupin meal or a combined dehulled lupin and hydrolysed poultry feather meal without any adverse effects on growth, immune function or blood chemistry.

This study aimed to determine excretion rates of ammonia and urea of Australian short-finned elvers as influenced by varying dietary crude protein intake. Elvers (2.3±0.02 g) were fed diets containing dietary crude protein levels of 25% (P25), 35% (P35), 45% (P45) and 55% (P55) dry matter equivalent to 14.17, 19.24, 20.57 and 26.39 g CP/MJ, respectively (pairs of diets P25, P35 and P45, P55 were isoenergetic). Elvers were fed twice a day to a total of 6% BW/day and nitrogenous excretory products (ammonia- and urea-nitrogen) measured during the following 24 h and peak excretion rates occurred 4–8 h following both the morning and afternoon feed. Daily ammonia-nitrogen excretion was significantly (P

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

Greenback flounder Rhombosolea tapirina (c. 2 g) fed to satiation had significantly (P

Growth was found to be associated with the changes of trypsin activity in the pyloric caecal tissues and the level of plasma insulin in Atlantic salmon (Salmo salar L.). A decrease in trypsin activity accompanied by an increase in plasma insulin was detected one month before an enhanced growth was observed. There were significant relationships between weight specific consumption rate, plasma insulin levels and fish growth. The correlation of weight specific consumption rate was higher with growth rate (R 2 D 0:7, p < 0:0001) than with plasma insulin concentration (R 2 D 0:4, p< 0:0001). When the comparison was made between Atlantic salmon carrying and lacking the trypsin variant TRP-292, the fish with the variant had lower maintenance ration (p < 0:05), higher capacity for protein synthesis in the white muscle (p< 0:02), and a greater ability to utilize the feed at a restricted ration than the fish without the variant. In Atlantic salmon lacking the variant, both plasma insulin concentrations and growth rates were significantly lower (p < 0:05) in the fish fed 0.5% bw day 1 than those fed 1% bw day 1 . Whilst the growth rates of TRP-292 salmon fed the different rations became similar one month after similar levels of plasma insulin were observed between them. The TRP-292 salmon may be defined as a high protein growth efficiency fish with low protein turnover rate. Genetic variation in trypsin isozyme pattern affects feed utilization, plasma insulin levels and growth in Atlantic salmon.

Silver trevally (Pseudocaranx dentex), also known as striped jack or shimaaji, is farmed intensively in Japan (Watanabe et al., 1990) where it can reach 1 kg after 2 years (T. Takeuchi, pers. comm.). Growth rates in Australasian waters are unknown, although data from New Zealand fisheries suggest that juveniles are moderate to fast growing in the wild (Stewart and Grieve, 1993). This study was conducted to obtain information about the influences of temperature on feed intake and to assess growth performance in order to evaluate the aquaculture potential of silver trevally at the southern limit of their distribution in Australia. Juvenile silver trevally caught using a beach seine between April and June 1995 at Stieglitz Beach, Tasmania (142°19'E; 41°20'S) were maintained at the Taroona Marine Research Laboratories. Prior to the experiment described here the fish had been used in a feed experiment for 12 weeks. Diet did not have a significant effect on growth (Gardner, 1998) and the fish were fed commercial feed for 3 weeks before the present experiment. Ration was 2% BW/day over the 15 weeks. Seventy-four fish of mean [SE] weight (37.0 [12.3] g) were randomly allocated to each of three 4 m tanks supplied continuously with unfiltered seawater. Fish were maintained indoors at ambient temperature (16.7 °C decreasing to 12.8 °C) and salinity (31–34‰) under a L8:D16 photoperiod for 112 days (23 January to 14 May 1996). A commercial salmon feed (Gibson’s Ltd, Tasmania: 52.0 (0.01) % crude protein; 13.0 (0.12) % crude fat; 11.8 (0.07) % ash; 21.0 kJ/g GE) was fed to satiation by hand four times per day and total feed intake (g) recorded daily. Wet weight (W, g) and fork length (L, cm) were measured at the start and after 56 and 112 days. Fulton’s condition factor (K) was calculated as 100 3 (W/L). Specific growth rate was calculated for wet weight (SGRW) and fork length (SGRL) as SGR (%/day) 5 100 3 [(ln X2/ln X1)/t]

This study aimed to measure protein synthesis using a stable isotope method, investigate protein-nitrogen flux in a flatfish Pleuronectes flesus, and use the data to test the hypothesis that individual differences in growth efficiency were related to individual differences in protein-nitrogen flux mediated through differences in protein synthesis and degradation. Three measurements of protein-nitrogen flux via consumption, protein synthesis and nitrogenous excretion were made for individual flounder during a 212-day period and fractional rates of protein-nitrogen flux were scaled for a 50–g flounder to provide mean values for protein consumption (2·11 ± 0·21% day−1), protein synthesis (2·08±0·23% day−1), protein growth (0·71±0·06% day−1) and protein degradation (1·37±0·24% day−1). Mean rates of nitrogenous excretion were 0·142 mg N g−1 day−1 and 0·047 mg N g−1 day−1 for ammonia and urea, respectively. Individual flounder had different protein growth efficiencies and this was correlated negatively and significantly with mean rates of protein synthesis (r - 0·70; P

In developing the mariculture of the southern bluefin tuna, there is a need to reduce handling of large tuna and to be able to assess their recent growth in research and commercial situations. The potential of various indices as correlates of growth and nutritional status was examined in PIT tagged juvenile tuna grown for 133 days. The study focused on the correlations between specific growth rate for wet weight (SGR) or fork length (SGRL) and morphological (condition factor and tissue–somatic indices), physical (muscle temperature) and biochemical (tissue protein, RNA and DNA concentrations) indices. Tuna held in cages were fed twice per day to satiation on one of four feeds (defrosted pilchards, research and two commercial prototypes). Final wet weight, change in wet weight, SGR, SGRL, condition factor and white muscle concentrations of protein, RNA and DNA were all higher for tagged tuna fed pilchards. Irrespective of diet, the white muscle protein, RNA and DNA concentrations and the ratios between them were all significantly and positively related to SGR. Liver protein, RNA and DNA concentration and the protein:DNA ratio were significantly and positively related to SGR. SGR was predicted by condition factor and by muscle temperature and this was reflected by the positive and significant correlations between muscle temperature and biochemical indices from muscle tissue. Regression models best predicted SGR from condition, pyloric caecal somatic index and white muscle RNA concentration and were tested by predicting (known) SGR of tuna grown in the previous year.

The aims of the present study were to investigate food consumption, growth and the dynamics of feeding hierarchies in the same groups of juvenile greenback flounder (Rhombosolea tapirina:Teleostei) fed either high or low rations. Differential food consumption by individual greenback flounder held in groups of 20 showed the presence of feeding hierarchies in which individuals consumed between 0 and 22% of the available food. Inter-individual differences in food consumption resulted in different growth rates leading to growth depensation (measured as an increase in the coefficient of variation for weight). Intra-individual differences in food consumption tended to be larger for flounder which consumed a lower share of the available food. When the group ration was reduced the inter-individual and intra-individual variations in food consumption increased. Consequently, the relationship between inter-individual and intra-individual variation in food consumption tended to become stronger at lower food availability and indicated an increase in the strength of the feeding hierarchies. This study suggests that individual differences in food consumption, mediated through exploitation competition, contribute to growth depensation in this species of flatfish.