Video surveillance methods to evaluate individual feeding response in rainbow trout (Oncorhynchus mykiss,Walbaum)—implications for feeding regime optimisation

Aquaculture International - Precisely analysing and optimising feeding regimes is central to salmonid growth performance and delivery of special diets. The current study developed novel video...     

Can the polyculture with South American catfish improve the feeding efficiency of rainbow trout culture?

The objective of this study was to determine if the South American catfish (Rhamdia quelen) is suitable to be farmed in polyculture with rainbow trout (Oncorhynchus mykiss) in intensive systems during the juvenile phase to maximize feed efficiency. Juveniles of rainbow trout (3.94?±?0.11 g) and South American catfish (2.07?±?0.04 g) were distributed in 16 tanks (100 L) with continuous water renewal at the density of 50 fish/tank. The experimental design was completely randomized with four treatments (proportions between species) and four replicates. The treatments were 100% trout (100T), 70% trout and 30% catfish (70T30C), 50% trout and 50% catfish (50T50C), and 100% catfish (100C). Fish were fed twice daily with pelleted commercial feed (45% crude protein) during an experimental period of 56 days. No feed was provided for the catfish in polyculture. The weight gained by the trout was higher in polyculture. Fish survival did not differ among the treatments. The average survival of the trout in all tanks was 99.6?±?1.0%, while the survival of the South American catfish was 97.9?±?2.7%. The total feed conversion ratio was lower in the 70T30J treatment, followed by the 100T treatment. Rainbow trout and South American catfish are compatible species for farming together in the first phase of their juvenile development. The different spaces occupied by these species inside tanks probably prevent competition or agonistic behavior. Catfish eat the non-ingested leftover diet from the trout, which improves feed conversion and increases sustainability.     

Effects of feeding (ω-3) HUFA-enriched Artemia during a progressively increasing period on the larviculture of freshwater prawns

Larvae of the freshwater prawn (Macrobrachium rosenbergii) were reared to post-larvae in a closed recirculation system. Six treatments were designed where freshly-hatched Artemia nauplii were first given to the larvae for 3, 7, 11, 15, 17 and 25 days according to the treatment. After that (-3) HUFA-enriched Artemia were given until the 28th day at which time the test was terminated and evaluated. The requirement for (-3) Highly Unsaturated Fatty Acids (HUFA) for the larval stages of M. rosenbergii was confirmed by this experiment. Moreover, the longer the period of feeding on (-3) HUFA-enriched Artemia nauplii, the better the results in terms of growth, metamorphosis rate, survival and stress resistance.     

Are Acartia tonsa cold‐stored eggs a suitable food source for the marine ornamental species Amphiprion polymnus? A feeding study

Copepods are the natural food items for marine fish larvae but are still difficult to be cultured on a continuous basis. Therefore, suitable storage techniques for copepod subitaneous eggs are of great interest. Cold‐stored copepod embryos still develop and retain a physiological activity during the cold storage period. As a consequence, their nutritional quality may change over the time of storage with these changes possibly affecting both eggs viability and larval fish survival and development. In this study, the clownfish, Amphiprion polymnus, was used as an experimental model to compare, for the first time, the effects of diets based on enriched rotifers and Artemia (control), Acartia tonsa copepods of a continuous culture and A. tonsa originated from 6 months cold‐stored eggs. The effects of the different diets were tested through morphometric, molecular and biochemical approach. This study demonstrated that after a 6 months cold storage period, the quality of copepods obtained from those eggs was suboptimal for A. polymnus larval rearing. In fact, larvae fed those copepods showed lower growth and survival performances respect to the other experimental groups.     

Freshwater catfish jundiá (Rhamdia quelen) larvae are prepared to digest inert feed at the exogenous feeding onset: physiological and histological assessments

This study assessed the morphological development of jundiá larvae’s digestive system and digestive proteolytic activity. Specific serine proteinases activities varied over time, with the highest peak at 12 h after hatching (AH), which corresponded to 296.38 ± 84.20 mU mg^?1 for trypsin and 315.45 ± 42.16 mU mg^?1 for chymotrypsin. Specific aspartic proteinases activities increased up to the start of weaning, oscillated during that phase, but showed a consistent increase after that, resulting in the highest specific activity at 252 h AH (7.88 ± 0.68 mU mg^?1). Gel assays showed different molecular forms, especially of serine proteinases. Histology showed the gastrointestinal tract development onset at 0 h AH and open mouth at 4 h AH. At 16 h AH, the following differentiation of the digestive tract was evident: oropharyngeal cavity, esophagus, liver, pancreas, stomach, and intestine. At 40 h AH, zymogen granules in the pancreas were observed, and at 48 h AH, mucus in the digestive tract and gastric glands in the stomach. Findings indicate that jundiá has a functional stomach before the end of vitelline reserves. Therefore, jundiá larvae are probably capable to digest inert feed at the exogenous feeding onset.     

The effects of feeding rates in juvenile Korean rockfish, (Sebastes schlegeli) reared at 17 °C and 20 °C water temperatures

Two feeding trials were conducted to determine the effects of feeding rates in juvenile Korean rockfish, (Sebastes schlegeli) reared at 17 and 20 °C water temperature. Fish averaging 5.5 ± 0.2 g (mean ± SD) at 17 °C and 5.5 ± 0.3 g (mean ± SD) at 20 °C water temperature were randomly distributed into 18 indoor tanks. At each water temperature, triplicate tanks were randomly assigned to one of six different feeding rates: 2.8, 3.8, 4.1, 4.4, 4.7 % and satiation (4.99 % BW day^?1) at 17 °C and 2.8, 3.8, 4.1, 4.4, 4.7 % and satiation (5.0 % BW day^?1) at 20 °C. After 4 weeks of feeding trial, weight gain (WG) and specific growth rate of fish fed groups at satiation and 4.7 % (BW day^?1) were significantly higher than those of fish fed groups at 2.8, 3.8 and 4.4 % (BW day^?1) in both 17 and 20 °C temperature. Feed efficiency and protein efficiency ratio of fish fed group at 2.8 % (BW day^?1) was significantly lower than those of fish fed groups at 3.8, 4.1, 4.4 and 4.7 % (BW day^?1) in both experiments. Hematocrit was significantly higher in fish fed group at 4.4 % (BW day^?1) at 17 °C, and there was no significant difference in hemoglobin content amongst all fish fed groups at 20 °C. Glutamic oxaloacetic transaminase and glutamic pyruvic transaminase of the fish fed group at 2.8 % (BW day^?1) were significantly higher than those of all other fish fed groups in both experiments. Broken line regression analysis of WG indicated that the optimum feeding rate of juvenile Korean rockfish was 4.48 % (BW day^?1) at 17 °C and 4.83 % (BW day^?1) at 20 °C. Therefore, these results indicated that the optimum feeding rate could be >4.1 % but <4.48 % at 17 °C and >4.4 % but <4.83 % at 20 °C. As we expected, current results have indicated that 5 g of juvenile Korean rockfish perform better at 17 °C than at 20 °C water temperature.     

Effects of temperature on the survival,feeding, and growth of pearl gentian grouper (female Epinephelus fuscoguttatus × male Epinephelus lanceolatus)

Fisheries Science - Pearl gentian grouper (Epinephelus fuscoguttatus ♀&nbsp;×&nbsp;Epinephelus lanceolatus ♂) is an important commercial and economic fish from the...