Inert Diet Research Articles

Feeding protocol with live feed and inert diet to determine the ideal age/size for weaning mullet Mugil liza (Valenciennes, 1836).

The Lebranche mullet Mugil liza is a marine fish of great importance for artisanal and industrial fishing, as well as aquaculture. The use of live feeds during the larviculture phase of marine fish is a significant component of production costs. The present study evaluated the effects of the feeding transition on different larval stages of M. liza, from the combined supply of live feed (Brachionus rotundiformis + Artemia franciscana) and live + inert feed (Artemia franciscana + inert diet) until the weaning phase to only the inert diet. A total of 3240 M. liza larvae (weight 0.0133 ± 0.0062 g and length 0.793 ± 0.160 cm) were distributed among the 12 experimental units (n = 270), resulting in four groups with three replicates each. Treatment groups consisted of feed transition with A. franciscana (enriched metanauplii) to commercial inert feed starting weaning at four different larval ages: 28, 31, 34, and 37 days post hatching. Zootechnical performance indexes and intestinal histomorphometry were evaluated. Mortality, condition factor, and length variation coefficient did not show significant differences between treatments. Final weight, final length, weight gain, and length gain were significantly greater in larvae that started weaning at 31, 34, and 37 days post hatching. Weight coefficient of variation was significantly higher in larvae that started weaning at 28 days (67.51 ± 11.70) compared to 37 days (34.40 ± 7.30). In intestinal histology, villi height (180.3 ± 4.4) was significantly higher in larvae that started weaning at 37 days post hatching. Considering the evidence found in the present study, it is recommended to start weaning M. liza on the 31st day post-hatching, using a 2-day co-feeding protocol (31st and 32nd days). From the 33rd day after hatching, M. liza larvae can receive only commercial feed.

Optimized co-feeding strategy of Anabas testudineus (Bloch 1792) larvae with enriched Moina micrura and egg custard-based inert diet; effects on growth, survival, and physio-metabolic responses

Optimized co-feeding strategy of Anabas testudineus (Bloch 1792) larvae with enriched Moina micrura and egg custard-based inert diet; effects on growth, survival, and physio-metabolic responses

Using digestive physiology to develop larval culture protocols for the Blackbanded Sunfish, a threatened centrarchid native to the United States

AbstractObjectiveThe Blackbanded Sunfish Enneacanthus chaetodon is a small centrarchid that is endemic to slow‐moving waters from New Jersey to central Florida, United States. The distribution of this species has been increasingly fragmented, primarily due to habitat degradation. The development of larval culture protocols is essential to produce this species for the aquarium trade and for potential restoration efforts. To streamline the production process, larvae should be transitioned from live feeds to inert diets as early as possible without sacrificing larval growth or survival.MethodsA developmental trial was conducted to determine the timing of digestive tract maturation, which indicates the ability of larvae to better digest inert microdiets (MDs). Blackbanded Sunfish larvae were sampled 12 times from 2 days posthatch (dph; notochord length [mean ± SD] = 4.38 ± 0.22 mm) to 50 dph (total length [TL] = 9.89 ± 1.64 mm) for subsequent analysis of digestive enzyme activity (via microplate assays) and digestive system morphology (via histology). A dietetics trial was conducted to determine the most appropriate commercial MD for this species at early life stages by testing the efficacy of three different MDs against a reference diet of brine shrimp Artemia nauplii. Lastly, a weaning trial was conducted to determine the earliest time point at which MDs should be introduced during the larval period.ResultBlackbanded Sunfish larvae transitioned from agastric to gastric digestion at approximately 40 dph (7.95 ± 0.86 mm TL), as determined by the presence of gastric glands and pepsin activity. In the dietetics trial, certain MDs yielded higher survival than others; however, all diets performed equally when considering the TL of the larvae. In the weaning trial, the highest survival was found when larvae were fed Artemia nauplii exclusively or when an MD was introduced at 48 dph (10.62 ± 1.88 mm TL).ConclusionLarval Blackbanded Sunfish may require up to 48 days of live feeds before introducing MDs but can be successfully transitioned to MDs after 48 dph without significantly affecting survival or growth.

Co-feeding na sobrevivência e crescimento de larvas de botia yoyo Botia lohachata durante a transição alimentar

ABSTRACT: This study evaluated the effect of the co-feeding (C) period on the growth and survival of larvae of the yo-yo loach Botia lohachata ornamental species during the weaning period from live food (LF) to inert food (IF). The breeders were subjected to induced spawning using crude pituitary homogenate. A total of 2,400 larvae were used with an average initial weight of 0.39 ± 0.09 mg and an average total length of 4.08 ± 0.21 mm, from a single breeding pair. The live food was newly hatched nauplii of Artemia franciscana, and the inert diet was a commercial ration with 55% crude protein and two particle sizes (142-350 µm and 350-500 µm). As the first food, all larvae received A. franciscana during the first six days, except for the fasting (NC) and inert food (IF) groups. The following co-feeding strategies were employed: C4 = 4 days of co-feeding, C8 = 8 days of co-feeding, C12 = 12 days of co-feeding, and LF = Artemia during the entire experimental period. The longest period with live food promoted better larval growth rates. The specific growth rate of larvae fed live food during the entire period (LF) was higher than that of the other groups, followed by the co-feeding strategies. There was no effect (P > 0.01) on larval survival in the LF, C12, C8, and C4 groups, which ranged from 41% to 53% after 30 days. Treatment R resulted in high mortality and low growth, suggesting that live food should be the first food source for B. lohachata larvae.

The effect of a formulated feed on the body growth and gonads quality of purple sea urchin (Paracentrotus lividus) aquaculture produced

Sea urchin gonads are a prized gourmet product in many areas of the globe, and wild populations are threatened by increasing demand, making this species a very desirable product in aquaculture. Due to the unique needs of each stage of the life cycle, a viable food protocol that seeks to satisfy each stage while optimizing production profitability is required. The objective of this work was to test a formulated feed for sea urchins, through the analysis of somatic growth, gonad development and their fatty acid profile. These results were compared with sea urchins fed natural food (Ulva spp.) At the end of the trial Paracentrotus lividus juveniles fed inert diet had higher total wet weight gain, total specific growth rate, and gonadosomatic index than those fed with macroalgae. However, histological observations did not reveal differences in the maturation state of the gonads. In comparison to sea urchins fed fresh Ulva spp., inert diet showed higher total wet weight gain and higher total specific growth rate. Fatty acid contents of the gonads of each treatment were found to be similar. The DHA levels in the gonads of sea-urchins fed the formulated feed were significantly higher. It was possible to record the biosynthesis activity of some fatty acids such as 20:4 ω 6, 16:4 ω 3, and 20:3 ω 3. It was found that the presence of some essential fatty acids, such as DHA and EPA, in the gonads is only dependent on the food profile. The addition of a DHA-rich ingredient in the formulated feed may have been preponderant in the constitution and development of the sea-urchins’ gonads.

Potential inert diets to supplement Artemia in larviculture of the giant Africa river prawn Macrobrachium vollenhovenii (Herklots, 1857) (Crustacea: Palaemonidae)

The protocol of culture of Macrobrachium vollenhovenii the main indigenous candidate for freshwater prawn culture in Africa is still under study. Though just few information exists, the transition of larvae from stage V to stage VI has been reported as the critical rearing period in larviculture. This study was to evaluate the efficiency of two locally diets to supplement Artemia in the feeding scheme from stage V to post larvae in the larviculture of this species. The two experimental diets were differentiated by the main source of protein: fish silage (Diet 1) and shrimp meat (Diet 2). One batch of larvae was cultured till stage V. The experiment itself was conducted in triplicate with three treatments: feeding Artemia exclusively (TA, control); fed partial replacement of Artemia with inert diet 1 (T1) or fed partial replacement of Artemia with diet 2 (T2). Larval development in T2 was significantly faster than TA and T1. Survival rate was significantly higher in T2 (12.64±1.2%) than TA (6.57±0.29%) and T1 (6.77±0.17%). The total length of larvae in T2 was significantly higher than TA and T1. Though the highest survival obtained in this study is still low, it’s however higher than those reported in other studies with this species. Also, the importance of finding alternatives to Artemia and cheaper diets remains very important.

Trends and New Developments in Artemia Research.

Simple SummaryArtemia is an important crustacean group, especially for aquaculture live food and as a model organism for toxicity assessment. The present study aimed to identify the current trends, research gaps, and literature development in the study of Artemia around the world. This primitive Arthropod has undergone significant evolution in terms of its application in various industries as well as relevant literature patterns in terms of scientometric analyses. An increasing number of scientists since 1970 has examined Artemia as an important species in aquaculture-related fields. However, a global scientometric review of Artemia literature is still lacking, which is the objective of this research. Using a CiteSpace analysis, the distribution of core authors and institutions, highly cited keywords and papers, author and journal contributions, and hot topics in the literature, as well as a co-citation analysis, particularly regarding authors, journals, documents, and clusters, were determined. Hence, 8741 relevant publications were generated from the Web of Science Core Collection database. The results revealed that the most significant contributions in Artemia research primarily originated from the USA, Brazil, Spain, India, China, and Belgium. Moreover, Artemia research focused mainly on top keywords such as brine shrimp and antimicrobial activity. Emerging trends related to Artemia research were Atlantic halibut, elongation factor, Artemia salina, lean protein, inert diet, alpha-crystallin protein, and Artemia embryo. At the same time, the study generated a vast total of 45 co-citation clusters. The present study provides the existing body of knowledge on Artemia research by sharing a visual knowledge map. This study offers a valuable perspective and profound understanding for researchers, farmers, and consortia interested in promoting Artemia as a sustainable live food in the global aquaculture industry.

First feed matters: The first diet of larval fish programmes growth, survival, and metabolism of larval ballan wrasse (Labrus bergylta)

The use of cleaner fish, such as the ballan wrasse (Labrus bergylta), is important for combatting the sea lice problem in salmonid cage farming. Ballan wrasse is the only wrasse species that is cultivated, though only about 50% of the approx. 3 million ballan wrasse used in 2020 was produced by aquaculture. The major obstacle for large scale cultivation of ballan wrasse is the difficult first feeding phase and a lack of functional feeding protocols.Like most pelagic marine fish larvae, ballan wrasse do not accept inert diets as first feed, and feeding regimes based on rotifers and Artemia (brine shrimps) usually lead to mixed results and are far from being optimal nutrition for the larvae.In a 48-day start feeding experiment, we studied the feasibility of replacing rotifers by an Experimental cirriped diet or copepod nauplii (Acartia tonsa) and replacing Artemia by nauplii of the cirriped Semibalanus balanoides. Later, all treatments received the same formulated diets. We sampled larvae at each feed transition to analyze different response variables such as growth, morphometry, gene expression, lipidomics, histology, and microbiology.We found significant differences in survival rates and growth. Larvae fed copepods as the first diet had significantly higher survival rates than larvae start-fed on either rotifers or small experimental cirripeds, and this pattern was also reflected in early growth and bone development. Gut histology at the end of the experiment (48 days after hatching) showed a more developed intestinal tissue in the larval group fed copepods first and cirripeds as the second diet compared to the other larval groups.Gene expression at day 48 post hatch still revealed pronounced differences between the larval group first fed on rotifers and larvae from the other three feeding regimes which received natural, unenriched diets. Even weeks after receiving the same formulated diets, lipidomics analyses revealed that several lipid species correlated either negatively or positively with larval growth rates or mortality.Our results are a clear indication for nutritional programming, pointing towards the importance the first diet has for the further life of a fish.

FOOD ACCEPTANCE IN DIFFERENT LARVAL STAGES OF <i>Macrobrachium carcinus</i>

Food acceptance in different larval stages of Macrobrachium carcinus was evaluated by investigating the stage at which the ingestion of inert moist diet food begins and by the incidence of Artemia nauplii and inert moist diet in the digestive tract throughout development. Two experiments were carried out: in the first study, the acceptance of the inert diet was evaluated in 60 larvae of each stage (I to XII) fed ad libitum after two hours of fasting. The inert diet was 100% accepted at zoea stage V. In the second study, newly hatched larva was then kept in larval tanks and fed with Artemia nauplii and inert moist diet simultaneously. Fifteen minutes after feeding, 50 specimens of each larval stage were examined and evaluated for the ingestion of these foods. Larvae at stage I did not feed, while larvae at stage II consumed both live and inert food. From the stage of zoea IX, the exclusive consumption of Artemia nauplii was not verified. These data indicate that feeding M. carcinus in larviculture can be initiated at stage II with inert moist diet and Artemia nauplii, and an exclusive supply of inert moist diet from stage IX can be recommended.

The role of cholecystokinin and peptide YY in feed intake in Atlantic halibut (Hippoglossus hippoglossus) larvae

Control of appetite and feed intake in fish larvae are still largely unexplored. Two of the key players in controlling vertebrate's feed intake are cholecystokinin (CCK) and peptide YY (PYY). Here we investigated the mRNA expression of pyy, cck and cck receptors (cckr) in the brain (head) and gut of Atlantic halibut larvae in response to three consecutive meals. We used Artemia nauplii cysts that are commonly ingested by halibut larvae when present as inert feed, and three water-soluble extracts as attractants to stimulate appetite. Cyst intake was not affected by the use of attractants and overall ingestion rate was low. Differences in mRNA expression of cck and pyy were observed between the halibut larvae that had eaten and those that had not despite readily available feed (cysts), supporting that mechanisms for control of feed intake are at least partly functional. All genes analysed were present in the brain and gut, however the different expression profiles between paralogues suggest potential divergent functions. In the gut, cck2 and pyyb mRNA expression was significantly higher in the larvae that ate cysts compared to larvae that decided to not eat, indicating that these genes play a satiety function in the halibut larvae similar to the general vertebrate scheme. However, cck2, cck2r1, and pyy mRNA expression in the brain were lower in the fed-filled larvae group compared to larvae before eating, which contrasts with the presumable anorectic function of these genes. Further research is required to fully evaluate how PYY and CCK affect the feeding biology in halibut larvae, contributing to formulate inert diets that can stimulate appetite and feed intake.

Effects of salinity, stocking density and feeding in Macrobrachium pantanalense larviculture

Macrobrachium pantanalense is a recently described endemic shrimp from Pantanal. The species completes its life cycle in freshwater and is used as an ornamental species for freshwater aquaria, as well as a model organism in risk assessment trials of anthropic impacts. However, all risk assessment trials performed to date have used wild specimens. As such, it is paramount to standardize the laboratory culture of M. pantanalense to allow the use of cultured specimens that safeguard the reliability and replicability of trials being performed. The present work evaluated the use of freshwater and different salinity levels (2, 4 and 6) for the larviculture of M. pantanalense, as well as larval stocking densities of 20, 40 and 60 larvae L−1. Six different larval feeding regimes were also evaluated: 100 % newly hatched Artemia nauplii (AN), 100 % wild zooplankton (WZ), 100 % inert diet (ID), 50 % AN + 50 % WZ, 50 % AN + 50 % ID and 50 % WZ + 50 % ID. Larvae of M. pantanalense were able to successfully metamorphose to post larvae (PL) when cultured in freshwater, although a higher % of PL was achieved under a salinity of 4 (25.6 ± 15.0 %). No significant differences were recorded in survival under different stocking densities. The best larval feeding regime tested was 100AN, promoting a higher production of PL (44.3 ± 18.3 %) when compared with other diets. Overall, the larviculture of M. pantanalense can be enhanced by using brackish water instead of freshwater. By employing a moderate larval stocking density (up to 60 larvae L−1) and an easy to use “of-the-shelf” larval live feed (Artemia nauplii) PL of M. pantanalense can be produced in the laboratory. The present findings are a first step towards the development of a production protocol for M. pantanalense in the laboratory to perform risk assessment trials of growing anthropic stressors impacting Pantanal.

Dry matter, protein, and energy digestibility of diets for juvenile Pacific white leg shrimps (Litopenaeus vannamei) reared at different salinity levels

ABSTRACT: This study evaluated the effect of low, medium, and high-water salinity (5, 35, and 50 ppt) on the apparent dry matter, protein, and energy digestibility of two formulated and six commercial diets for juvenile whiteleg shrimp, Litopenaeus vannamei, in a 120-day trial. Digestibility was determined in vivo using chromic oxide as an inert diet marker. Hydrostability in pellets varied from 86.8% to 99.9%; dry matter digestibility varied from 49.1% to 64.1%; protein digestibility showed greater variations at all salinities (56.9%-85.8%); and energy digestibility ranged from 70.1 to 86.4%. Salinity had a significant effect on dry matter, protein, and energy digestibility. Using a principal component analysis (PCA) with a covariance matrix, our findings suggested that the E2 (fishmeal-based formulation) diet and 35 ppt salinity provided optimum hydrostability and digestibility to Pacific white leg shrimp juveniles.

Successful nursing of Mekong giant catfish (Pangasianodon gigas, Chevey 1930) larval by replacing live feed with microcapsule diet

The larviculture of Mekong giant catfish (Pangasianodon gigas, Chevey 1930) solely relies on live feeds.This study aimed to investigate the proper time to replace live feeds with a microcapsule diet (MC diet) in the earliest stage of larvae to reduce dependency on live feeds in larval rearing of Mekong giant catfish. Crude enzyme of the 3-dph (days post hatching), 7-dph, 14-dph, and 30-dph larvae were extracted for determination of proteolytic digestive enzyme activities. Specific activities of total protease, chymotrypsin-like and trypsin-like of larvae displayed an elevated tendency with increasing life stage of larvae. The highest specific activities of all digestive enzymes were noticed at 30 dph (p < 0.05). In vitro protein digestibility of fish protein hydrolysate (FPH) and fish meal digested by different-stage larval extracts showed that protein digestibility of both ingredients significantly increased with increasing life stage of the larvae (p < 0.05). Protein digestibility of FPH was significantly higher than that of fish meal at 3 dph, 7 dph, and 14 dph (p < 0.05). The highest protein digestibility of both ingredients were statistically observed in 30-dph larvae (p < 0.05). The results of in vitro experiments indicate that the metamorphosis of digestive system of larvae, which begins after 14 dph, is a suitable time to firstly introduce an inert diet for this catfish larval nursing. In a 28-day feeding exper TITLE \\* MERGEFORMAT iment, 15-dph catfish larvaewere fed under three different feeding regimes including: Group A (live feed as a control) hand fed with Moina spp. from 15 dph to 42 dph; Group B (Moina and then MC diet) fed with Moina as a live feed and then MC diet from 15 dph to 27 dph and switched to MC diet as an inert diet from 28 dph to 42 dph; and Group C (MC diet) fed with MC diet from 15 dph up to 42 dph. They were fed three times daily for 28 days. The results showed improvement in weight gain rate and specific growth rate of catfish in Group B were comparable to that Group C fed with MC diet alone (p < 0.05). No significant difference in survival rate among the treatments was found (p > 0.05). Feeding MC diet did not cause any histopathological alterations in liver and intestine of catfish. In conclusion, early introduction of catfish larvae with MC diet alone can start at 30 dph, which helps in shortening Moina feeding period, providing growth rate and survival rate benefits.

Feeding strategy induces compensatory growth in Heros severus fingerlings, an Amazonian ornamental fish

The aim of the present study was to evaluate the compensatory growth of severum (Heros severus) fingerlings fed inert diet for 30 days, after 13 days of larviculture at different feeding rates. The production cost with Artemia nauplii was also evaluated. For that purpose, a growth trial was performed with 400 severum post-larvae, distributed in twenty aquaria (1 L) at density of 20 post-larvae L−1. The experiment was conducted in a completely randomized design with five treatments and four replicates. For 10 days, the post-larvae received Artemia nauplii at different feeding rates: 100, 150, 200, 250 and 300 nauplii post-larvae−1 day−1. Subsequently, three days of food transition to an inert diet was performed. After this period, the severum stocking density was halved and the fish received inert diet for 30 days. The post-larvae fed with 200 Artemia nauplii post-larvae−1 day−1 presented the best results of final length, length gain and specific growth rate for length. On the other hand, post-larvae fed with 300 nauplii post-larvae−1 day−1 presented the highest results for final weight, weight gain and specific growth rate for weight. The average cost of using Artemia nauplii incresed directly with the increasing amount of nauplii supplied. The fingerlings presented best results of final weight and final length when received 250 nauplii post-larvae−1 day−1 during the larviculture. The weight gain of fingerlings did not differ for fish initially fed with 150–300 Artemia nauplii post-larvae−1 day−1, proving that the fingerlings expressed partial compensatory growth. The specific growth rate for length and weight were higher in fingerlings initially fed with 100 Artemia nauplii post-larvae−1 day−1, however, the survival rate was lower in fingerlings fed that amount of Artemia nauplii. Therefore, it is recommended 150 Artemia nauplii post-larvae−1 day−1 during the larviculture of severum to induce partial compensatory growth and reduce cost.

Influence of food concentration and abiotic parameters on population density growth of the ciliated marine protozoan Euplotes sp. under controlled conditions

High mortality is common when culturing most marine fish larvae, especially during the transition from endogenous to exogenous feeding. In aquaculture, many species of marine fish are not able to survive when only fed enriched rotifers and Artemia spp. nauplii. Ciliates are a potential alternative live food organism for first-feeding larvae, because they can grow to high population densities, accept inert diets, and are natural prey organisms of marine fish larvae. The range of culture parameters to optimize population growth of the ciliate Euplotes sp. are unknown. Five experiments were conducted to determine the effects of food concentration and abiotic factors including salinity, aeration rate, temperature and photoperiod on population growth of the ciliate Euplotes sp. Results indicated the optimal ranges for population growth of Euplotes sp. was a temperature between 26 and 32°C, salinities from 20 and 35 g/L, food (Protein Selco®) concentrations of 250 and 500 mg/million ciliates, absence of or low aeration (8.5 cm3/min) and the photoperiod 0L:24D. Euplotes sp. can tolerate high ammonia and very low dissolved oxygen concentrations, and population growth can occur in these conditions for at least 7 days.

The effect of live and inert feed treatment with lactobacilli on weaning success in intensively reared pike-perch larvae

Weaning to inert diet in intensively reared pike-perch larvae is confronted with significant fish loss, which prevents successful commercialization of pike-perch production. Achievement of satisfactory feed quality and effective assimilation of nutrients by larval fish is the major challenge in larval production process. Aim of this study was to evaluate whether treatment of live and inert feed with lactobacilli could alleviate growth retardation associated with early weaning of pike-perch reared in recirculating system. Weaning started on 18th day post-hatching (DPH) either as sudden weaning (SW) or by co-administration of Artemia for six days (gradual weaning, GW). Prior to administration to fish, Artemia was treated with Lactobacillus salivarius BGHO1/Lb. reuteri BGGO6-55, while inert feed was treated with Lb. paracasei subsp. paracasei BGHN14/Lb. rhamnosus BGT10. Treatment with lactobacilli slightly raised neutral lipid level in Artemia nauplii, but significantly reduced their content in dry feed. Fish were sampled on the 24th DPH. Survival, morphometric indices, skeleton differentiation, digestive enzyme activity and opportunistic pathogenic bacteria level were assessed in whole fish specimens. GW fish were presented with better survival, body growth and phospholipase A2 (PLA2) activity. Alongside, Vibrio spp. growth was suppressed in these fish and skeleton development was improved, according to Alizarin Red staining and Col1A1/Sparc mRNA expression data. Lactobacilli application in GW fish correlated with an increase of survival, condition factor and growth rate, according to trypsin and chymotrypsin activities, indicating better utilization of dietary proteins for muscle building. In SW fish, lactobacilli elevated chymotrypsin activity, PLA2 to lipase activity ratio and improved survival and ossification, as evident from Alizarin Red staining and Col1A1/Sparc mRNA expression. This indicated improved fatty acid absorption and control of metamorphosis process. Furthermore, lactobacilli suppressed Vibrio spp. growth in SW fish. Aside from demonstrating the ability of lactobacilli to aid weaning in pike-perch larvae, this study indicated that different types of food treatment may direct fish growth in a predictable manner, allowing further cost-effective improvements of larval pike-perch rearing in intensive system.

Lecithin-enriched Artemia combined with inert diet and its effects on reproduction and digestive enzymes of Aequidens rivulatus

The present study investigated the effects of soybean lecithin bioencapsulated in adult Artemia franciscana and unenriched Artemia in combination with an inert diet on digestive enzymes activity and reproductive performance in Aequidens rivulatus (green terror cichlid). Eight hundred and ten fish (3.1 ± 0.2 g) were randomly allotted into glass tank (80 L) and assigned to ten dietary treatments with 5 different levels (0, 25, 50, 75, and 100%) of either lecithin-enriched Artemia (EA) or unenriched Artemia (UA) over a period of 90 days. The amount of total polar lipid increased from 39.2% in the unenriched Artemia to 43.7% in the lecithin-enriched Artemia (P < .05). The fish fed with 50% EA had higher total weight, and total length compared with other groups (P < .05). The peculiar functions of total alkaline proteases, α-amylase, and lipase in green terror increased in the groups fed with lecithin-enriched Artemia, compared to the un-enriched groups (P < .05). The highest total alkaline proteases activity was observed in the fish fed with 75% EA treatment. In comparison to the other groups, fish fed 100 and 0% levels of Artemia replacement had significantly highest and lowest α-amylase activity values, respectively. Concerning reproductive performance, the highest average fecundity, egg diameter, egg weight, fertilization, hatching, and larval survival rates, as well as the lowest time between two spawning episodes, were obtained in fish fed 50% EA. In conclusion, this feeding strategy is advisable for a proper nutritional management of broodfish of green terror cichlid.

Reduction of skeletal anomalies in meagre (Argyrosomus regius, Asso, 1801) through early introduction of inert diet

The consolidation of meagre (Argyrosomus regius) in aquaculture requires an understanding and optimization of larval rearing and nutritional conditions. The aim of this study was to analyse the effects of an early introduction of inert diets during larval rearing, on growth performance, digestive enzymes activity and development of skeletal anomalies. This study evaluated the effects of three different timings for the introduction of inert diet during larval rearing: a control group (CTRL) where inert diet was initiated at 14 days after hatching (DAH) and two treatment groups that had an earlier introduction of inert diet at 8 DAH (T1) and 11 DAH (T2). Meagre larvae exhibited similar pancreatic and intestinal enzymatic activities among the different dietary treatments. No differences in the overall prevalence of anomalies were observed between treatments at 25 or 50 DAH, however, a significant reduction was observed in all groups with the transition from larval to juvenile stage. The precocious introduction of inert diet shifted the distribution of vertebral anomalies to a more anterior vertebral column region. Altogether, this study shows that earlier introduction of inert diets in meagre hatcheries can be beneficial for meagre production in aquaculture.

Microalgae Ankistrodesmus gracilis as feed ingredient for ornamental fish Xiphophorus maculatus

A trial evaluated the effectiveness of macrophytes, Azolla caroliniana (AAC) and Lemna minor (ALM) as a culture media for microalgae Ankistrodesmus gracilis, and their possible use as feed ingredient for ornamental fish. Water quality in all aquariums was adequate for the growth of Xiphophorus maculatus, whilst pH acidity in inert diet (ID) treatment and high content of P in AAC diet treatment did not interfere in fish development. Growth performance parameters were higher (P < 0.05) in ALM diet treatment, except condition factor and feed conversion ratio, with similar rates (P > 0.05) in all diet treatments. Survival was above 75% and total length was similar (P > 0.05) for ID and AAC diet treatments. Lipid levels ranged between 7 and 11%, and was enough to maintain high survival rates (> 80%) and weight gain above 0.42 g to mixed diet (AAC and ALM) and 0.27 g to inert diet. Ankistrodesmus gracilis and macrophytes as a culture media are useful as functional ingredients, because biomass may be incorporated with the food supplement for X. maculatus to enhance nutrition quality and to maintain high growth performance. Although A. caroliniana and L. minor may be used with culture media, L. minor provided the best results to microalgae growth biomass and ornamental fish.

Changes in digestive enzyme activities during early ontogeny of Seriola rivoliana.

This study contributes to basic knowledge on the development of larval digestive enzyme activities of Seriola rivoliana, a carnivorous species that has shown high mortality in larval stage. The study was conducted under laboratory-controlled conditions until larvae reached 30days after hatching (DAH). The specific activity of amylase and pepsin was analysed by spectrophotometric methods, and lipase, trypsin, chymotrypsin and alkaline phosphatase by fluorometry. The results showed that S. rivoliana larvae had different enzyme patterns depending on their developmental stage, and also when exogenous food was administered (rotifers and Artemia). At hatching (2.98 ± 0.14mm SL), lipase, alkaline phosphatase, trypsin and chymotrypsin activities were detected, but the last two enzymes showed an activity close to zero. Trypsin, chymotrypsin, lipase and alkaline phosphatase sharply increased their activities after starting the first feeding. Amylase activity was not detected until 5 DAH (3.51 ± 0.18mm SL) and had a peak on day 15 (4.59 ± 0.39mm SL); no activity was observed from then on. Pepsin activity was detected approximately at 15 DAH, showing a constant increase onwards. Trypsin had a peak on day 15 and then decreased on the following days. Chymotrypsin had the highest peak at 5 DAH, then a sharp decrease on day seven (3.88 ± 0.11mm SL), and it increased gradually until day 30 (11.71 ± 1.59mm SL). Lipase showed the highest activity at 15 DAH and then decreased its value. Finally, alkaline phosphatase showed the highest value at 3 DAH (3.62 ± 0.06mm SL); then, a severe decrease was observed with activity stability on the following days. In conclusion, S. rivoliana larvae had a similar pattern as that observed in other marine-carnivorous fish larvae, so it could be considered as juvenile at 20 DAH in terms of digestive physiology; based on our results and previous study, the weaning process could start after this age, which would allow establishing a co-feeding protocol using inert diet.