The effect of feed frequency on growth, survival and behaviour of juvenile spiny lobster (Panulirus ornatus)

Spiny lobsters have a range of complex chemical communication pathways that contribute to feeding behaviour. Feed intake is modulated by feed availability and feed characteristics, such as attractiveness and palatability, with behavioural factors, such as social competition and circadian rhythm, providing an extra layer of complexity. In this study, we investigated the effect of feed frequency on survival and growth of early-stage (instar 26) juvenile Palunirus ornatus. In addition, we investigated the interactive effect of feed frequency and circadian rhythm on lobster feed response. Lobsters were fed a set ration at a frequency of either one, two, four, eight, sixteen or thirty-two times per day over 49 days. The effect of feed frequency on growth and survival was determined. Circadian feeding activity under these feeding treatments was assessed by time-lapse photography. Increased feed frequency from one to sixteen feeds daily improved growth by increasing apparent feed intake (AFI) and feed attraction, as confirmed by the increased presence of lobsters in the feeding area. The rapid leaching of feed attractant, particularly free amino acid, suggests a beneficial effect of multiple feeding frequencies on feed intake and growth. However, more than sixteen feeds per day resulted in decreased feed intake and a subsequent reduction in growth. The decrease in feed intake is thought to be associated with saturation of the culture environment with attractants, resulting in a reduced behavioural response to feed supplies. This may indicate the need for depletion of attractants to retrigger a feeding response. As lobsters were grown communally, faster growth at sixteen rations per day was also coupled with increased cannibalism, likely driven by increased vulnerability with the occurrence of more frequent ecdysis events. Whereas circadian rhythm indicated more activity at night, an interaction between daytime activity and feed frequency was not observed

Interactions between dietary docosahexaenoic acid and other long-chain polyunsaturated fatty acids on performance and fatty acid retention in post-smolt Atlantic salmon (Salmo salar)

A study with varying dietary inclusion levels (1, 5, 10, 15 and 20 g kg-1) of docosahexaenoic acid (DHA; 22:6n-3) was conducted with post-smolt (111 ± 2.6 g; mean ± S.) Atlantic salmon (Salmo salar) over a 9-week period. In addition to the series of DHA inclusion levels, the study included further diets that had DHA at 10 g kg-1 in combination with either eicosapentaenoic acid (EPA; 20:5n-3) or arachidonic acid (ARA; 20:4n-6), both also included at 10 g kg-1. An additional treatment with both EPA and DHA included at 5 g kg-1 (total of 10 g kg-1 long-chain polyunsaturated fatty acids, LC-PUFA) was also included. After a 9-week feeding period, fish were weighed, and carcass, blood and tissue samples collected. A minor improvement in growth was seen with increasing inclusion of DHA. However, the addition of EPA further improved growth response while addition of ARA had no effect on growth. As with most lipid studies, the fatty acid composition of the whole body lipids generally reflected that of the diets. However, there were notable exceptions to this, and these implicate some interactions among the different LC-PUFA in terms of the fatty acid bio- chemistry in this species. At very low inclusion levels, DHA retention was substantially higher (*250 %) than that at all other inclusion levels (31–58 %). The inclusion of EPA in the diet also had a positive effect on the retention efficiency of DHA. However, EPA retention was highly variable and at low DHA inclusion levels there was a net loss of EPA as this fatty acid was most likely elongated to produce DHA, consistent with increased DHA retention with addi- tional EPA in the diet. Retention of DPA (22:5n-3) was high at low levels of DHA, but diminished with increasing DHA inclusion, similar to that seen with DHA retention. The addition of EPA to the diet resulted in a substantial increase in the efficiency of DPA retention; the inclusion of ARA had the opposite effect. Retention of ARA was unaffected by DHA inclusion, but the addition of either EPA or ARA to the diet resulted in a substantial reduction in the efficiency of ARA retention. No effects of dietary treatment were noted on the retention of either linolenic (18:3n-3) or linoleic (18:2n-6) acids. When the total n-3 LC-PUFA content of the diet was the same but consisted of either DHA alone or as a combination of EPA plus DHA, the performance effects were similar

A Study on the Factors Influencing the Growth and Survival of Juvenile Sea Cucumber, Holothuria atra, under Laboratory Conditions

In recent years the sea cucumber fishery has emerged as a lucrative business in Mauritius. However, few studies on these marine detritivorous animals have been carried out in the island either in the wild or for aquaculture. The aim of the present study was to investigate the influence environmental factors such as salinity and temperature and biological factors such as stocking density and feed type on the growth and survival of juvenile sea cucumbers Holothuria atra. The study was conducted from mid-October 2006 to end of January 2007 period. For the experiment, 150 juvenile H. atra of similar size and weighing (27-30 g) were collected from Le Morne and Albion Lagoons. The experiments were carried out in round polyether tanks of 2 m3 with an area of 1.5 m2 at Albion Fisheries Research Centre. The juveniles H. atra (6 specimens per tank in duplicate) were reared at salinity 25, 30 and 35 ppt; temperature 26, 28 and 32°C; and were given two feed types (crushed algae and a formulated feed (85% crushed algae and 15% fish feed)). For studying stocking density duplicate tanks containing 6, 12 and 18 specimen (per sq m) were used. At one-week intervals, the sea cucumbers were starved for 24h and then weighed. The wet weight was used as an index for its growth performance over the experimental period. The highest specific growth rate (SGR) and survival were obtained at temperature of 28°C (1.43 ± 0.15 g and 100% respectively). At temperature 32°C, the SGR was a lower (0.78 ± 0.12 g) and a survival of 67%. Specific growth rate and survival was lowest in stocking density 18 (0.12 ± 0.23 g & 69% respectively). At salinity of 25 ppt there was decrease in SGR during the experimental period (-4.61 ± 0.29 g). Feeding H. atra with crushed algae produced little increase in growth (0.18 ± 0.16 g) while feeding with formulated feed the specific growth rate was notable (0.97 ± 0.14 g). Under the conditions of the experiments, growth and survival of juvenile H.atra were greatest at 35‰ salinity, temperature 28ºC, and a formulated feed made from algae and dried fish feed and density of 6 specimens per m2.Keywords: Holothuria atra; Salinity; Temperature; Stocking density; Feed type; Specific growth rate (SGR); Surviva

Dietary methionine spares the requirement for taurine in juvenile Yellowtail Kingfish (Seriola lalandi)

Taurine, a β-sulphonic amino acid, is a growth and health promoting dietary supplement in commercial finfish aquaculture. Reported recommendations for taurine supplementation in Seriola spp. feeds broadly range from 2.6 to 10.2 g kg−1 diet. Methionine is an essential amino acid and substrate for various metabolic compounds and acts as a methyl and sulfur donor, potentially sparing taurine. Dietary methionine requirements are currently unknown for Yellowtail Kingfish (Seriola lalandi); however, recommendations for the closely related Japanese Yellowtail (Seriola quinqueradiata) indicate that 11.1 g kg−1 diet is adequate. The taurine requirement and sparing effect of methionine of juvenile Yellowtail Kingfish was quantified by conducting a feeding experiment and applying a factorial, orthogonal dose-response design. Fourteen isonitrogenous and isoenergetic diets were prepared using practical raw ingredients with either one of two levels of methionine (10.9 ± 0.2 g kg−1 or 17.2 ± 0.6 g kg−1) and either one of seven levels of taurine, increasing from 1.6 to 20.4 g kg−1, respectively. Triplicate groups of 14 fish (53.3 ± 0.4 g fish−1) were fed one of the 14 diets over seven weeks. Based on growth and feeding results, juvenile Yellowtail Kingfish do not require dietary taurine supplementations when the basal taurine diets content is at least 1.6 g taurine kg−1 at a dietary methionine content of 17.2 ± 0.6 g kg−1 diet. This demonstrates that dietary methionine has a sparing effect on taurine supplementation. Yellowtail Kingfish fed dietary methionine exceeding the current minimum industry standard (~11.1 g kg−1), grew more rapidly than those fed high dietary taurine contents at dietary methionine levels approximating that of current industry practice, indicating the indispensability of adequate methionine supply. Breakpoint analysis on the specific growth rate in Yellowtail Kingfish fed a methionine level of current industry practice, estimated a digestible taurine requirement of 1.98 g kgBW−1 d−1 at an average digestible methionine intake of 3.4 g kgBW−1 d−1 This equates to a dietary taurine content of 7.7 g kg−1 diet at a dietary methionine content of 10.9 g kg−1 diet. Our results indicate that in juvenile Yellowtail Kingfish: adequate dietary methionine spares dietary taurine supplementation; insufficient dietary methionine provokes a taurine requirement; and current industry specifications for dietary methionine for Yellowtail Kingfish aquafeed require reassessment

The interactive effect of dietary choline and water temperature on the liver lipid composition, histology, and plasma biochemistry of juvenile yellowtail kingfish (Seriola lalandi)

The study examined the interactive effects of choline content (supplied as choline chloride salt (CC); no added CC, 3.0, or 6.0 g CC kg−1 diet) and water temperature (16 °C vs 24 °C) on liver lipid composition, liver histology and plasma biochemistry. Liver and plasma samples were collected from juvenile yellowtail kingfish (Seriola lalandi; YTK; 156 g body weight), fed fishmeal-based practical diets, at the conclusion of an eight-week feeding experiment. The results showed that higher liver lipid content at 24 °C was due to greater triacylglycerol (TAG) accumulation. Liver phospholipids content remained similar regardless of CC supplementation and temperature (P > 0.05). As expected, liver phospholipids were mainly composed of phosphatidylcholine (PC); however, in most cases liver phospholipids were almost completely made up of PC. Phospholipid classes were also not significantly affected by CC supplementation and temperature. The results indicate that these lipid classes were tightly regulated in the liver of juvenile YTK. Fatty acids composition among TAG, FFA, and phospholipids fractions were different; however, within the phospholipids fraction, the long chain polyunsaturated fatty acids (LC-PUFA) proportion in the liver of YTK remained unchanged regardless of treatments. In general, histological examination did not show severe lesions in fish livers across all treatments. Fish also had significantly more hepatocytes with large nuclei at 16 °C than at 24 °C which is a response that requires further research. Plasma analytes were profoundly affected by temperature rather than by CC supplementation; however, there is no strong evidence indicating compromised health in fish reared at either temperature. This study demonstrates that fish fed fishmeal-based practical diets generally had normal looking livers; nevertheless, some liver and plasma health indicators can be affected in juvenile YTK reared at sub-optimal temperatures and fed diets without supplemented choline