Live Feed Production Research Articles

Effects of Different Co-Feeding Protocols on the Early Weaning of Flathead Grey Mullet (Mugil cephalus) Larvae.

The sustainable expansion of aquaculture relies on a sufficient supply of eggs and larvae, which are the first step of life cycle management. However, marine fish larval rearing generally depends on live feed production, which needs additional facilities and labor. The flathead grey mullet (Mugil cephalus), a promising species for aquaculture diversification, has a precocious digestive system development, supporting the feasibility of early weaning strategies. For these reasons, this study evaluated survival, growth, proximate and fatty acid composition, and gene expression of Mugil cephalus larvae reared under three different weaning protocols. Three co-feeding treatments, two with different Artemia sp. concentrations (A100 and A50, 2 and 1 Artemia sp. mL-1 day-1, respectively) and one with only rotifers administered as live feed along the feeding trial (A0), were assessed from 22 to 36 days post-hatching (dph). The A0 treatment performed better in survival (64.79 ± 7.40%) than the A100 protocol (32.46 ± 12.82%). In contrast, the larvae of the A100 treatment presented significantly higher final length (15.51 ± 0.86 mm) than those of the A0 treatment (12.19 ± 1.45 mm) and higher final weight (41.28 ± 1.48 mg) than those of the A50 and A0 treatments (31.23 ± 3.65 mg and 24.03 ± 7.99 mg, respectively). On the other hand, the expression of digestive enzyme- and somatotropic factor-related genes did not show differences between treatments. The present results support the convenience of treatment A0 in maximizing survival, as rotifers should be maintained until 30-32 dph (until a total larval length of at least 10 mm). However, to improve growth and minimize size dispersion, Artemia sp. addition is recommended from day 26 to day 29 post-hatching (total larval length of 8 to 9 mm).

Tilapia processing byproduct treated with enzymatic hydrolysis and Rhodopseudomonas palustris is feasible for live feed culturing: Pathogen inhibition in vitro, live feeds microbiota, and Bidyanus bidyanus larviculture

Fish processing byproducts are conventionally used in live feed production for larviculture because of their low cost and high productivity. However, waste-generated bacteria may cause pathogen proliferation, and antibiotics are widely used to reduce the bacterial loads of live feeds. In this study, tilapia processing byproducts were hydrolyzed into fish protein hydrolysate (FPH). Subsequently, the FPH was used to culture Rhodopseudomonas palustris, a photosynthetic bacterium (PSB), as a nutritional source for live feed. The results of the in vitro pathogen inhibition assay indicated that R. palustris significantly inhibited the growth of Aeromonas hydrophila, Edwardsiella tarda, Lactococcus garviae, and Streptococcus iniae in the FPH supernatant (p < 0.05). In practical live feed culture, untreated minced tilapia byproduct (control group) or FPH+PSB were used as nutritional sources for the live feeds. The V3–V4 region of the 16 S rRNA gene was amplified and sequenced for microbiota analysis. In the FPH+PSB group, Flavobacteriaceae and Alteromonadaceae were notably enriched. The Aeromonadaceae and Chitinophagaceae were reduced relative to the control group. Burkholdweiaceae, Rhodobacteraceae, Moraxellaceae, and Pseudomonadaceae were the dominant bacterial families in both groups. To examine the effects of different live feed culturing methods on larviculture, the cultured live feed was fed to Bidyanus bidyanus larvae at 5 days posthatch (DPH). After 25 days of larviculture, the growth performance and survival rate of the FPH+PSB group were significantly higher than those of the control group (p < 0.05). These results indicated that treating tilapia byproducts with hydrolysis and R. palustris to culture live feed exerted a positive effect on B. bidyanus larviculture.

Fish Farming Techniques: Current Situation and Trends

World aquaculture is increasingly diversified and intensive, due to the use of new technologies, having grown a lot in recent decades and contributed significantly to improving food security and reducing poverty in the world, with fish farming being a promising activity for the production of protein with high nutritional value. The large aquaculture companies that recognize the potential of this important modality have invested in the study and production of various productive segments of the most diverse species of fish. This review article aims to provide information on the world panorama of marine fish farming, with the main systems and production stages of the most important organisms with commercial potential, aiming to achieve a highly sustainable production, with high nutritional content and benefits for human health. The production of live feed in the larval stage should be highlighted, in order to optimize survival and weight gain. In addition, trends in the cultivation of estuarine and saltwater fish will be detailed in this review, such as the use of biotechnology and technological innovations, cultivations integration, and biosecurity. Thus, innovative methods to optimize the farming system need to be more ecosustainable, reducing the negative impacts on the environmental level.

Chlorella-Daphnia consortium as a promising tool for bioremediation of Nile tilapia farming wastewater

ABSTRACT The objective of this study was to investigate the effluent treatment from Nile tilapia farming in a biofloc system with a consortium of microalgae (Chlorella vulgaris) and zooplankton (Daphnia similis). Thus, integrated cultures of C. vulgaris and D. similis were performed in two forms of wastewater treatment: sedimentation (S) and non-sedimentation (NS), in four different salinities (1, 2, 3 and 4 g L−1). Water quality, growth of D. similis, behaviour of C. vulgaris, efficiency of removal of nitrogen compounds, orthophosphate, and total suspended solids (TSS) were measured. D. similis had higher density in 3NS (p < 0.05), while population die-off occurred in 4S and 4NS. The 2S and 1NS combinations stood out in bioremediation, achieving removal of up to 70.37% nitrate, 75.74% orthophosphate, and 90.74% TSS. 2S and 3S cultures became self-sufficient from day 21. Thus, the Chlorella-Daphnia consortium using 3NS allowed better production of D. similis, whereas salinities 2 g L−1 (S) and 1 g L−1 (NS) provided better bioremediation, and the use of S wastewater improved the sustainability of the system. These results contribute to a better evaluation of cultures in consortia of organisms for the treatment of aquaculture wastewater and the production of live feed for aquaculture. Highlights Four salinities and two forms of biofloc wastewater processing were evaluated. Salinity 2 and sedimentation of biofloc wastewater showed better bioremediation. Salinity 3 and non-sedimentation of biofloc wastewater had better D. similis growth. C. vulgaris could grow in biofloc wastewater even with Daphnia predation. Chlorella-Daphnia consortium is an option for bioremediation and live food production.

Comparing the performance of four commercial microdiets in an early weaning protocol for European seabass larvae ( Dicentrarchus labrax )

The promise of an off-the-shelf, microparticulate diet for first feeding marine larval fish is still one of the ‘holy grails’ of the hatchery manager. Replacing the laborious live feed production facilities with high-quality microdiets will greatly increase marine larval production, improve hatchery consistency and will help in cost reduction in fry production. Over the last decades, many scientific and industrial efforts have focussed on developing microparticulate diets to reduce or replace the use of live feed for growing marine fish larvae in hatcheries. However, in most professional hatcheries, an extended live feed period is still the standard procedure. Thus, this study aimed to compare the performance of four state-of-the-art commercially available microdiets used in an early weaning protocol to the standard Artemia-based feeding. European seabass larvae were used as a model organism. The three most relevant parameters, survival, growth and deformities were used for the performance-rating of the four different microdiets. The results of the study depict that early weaning of European seabass between 15 and 20 days post-hatching (dph) onto the commercially available microdiets still result in lower survival, reduced growth and an increase in deformities in the early-weaned treatments. Nevertheless, one microdiet outperformed the others in this study, resulting in significantly fewer deformed larvae and improved growth. However, larvae fed with Artemia only still yielded the best results considering growth, survival and deformities.

Rearing water microbiomes in white leg shrimp (Litopenaeus vannamei) larviculture assemble stochastically and are influenced by the microbiomes of live feed products.

The development of effective management strategies to reduce the occurrence of diseases in aquaculture is hampered by the limited knowledge on the microbial ecology of these systems. In this study, the dynamics and dominant community assembly processes in the rearing water of Litopenaeus vannamei larviculture tanks were determined. Additionally, the contribution of peripheral microbiomes, such as those of live and dry feeds, to the rearing water microbiome were quantified. The community assembly in the hatchery rearing water over time was dominated by stochasticity, which explains the observed heterogeneity between replicate cultivations. The community undergoes two shifts that match with the dynamics of the algal abundances in the rearing water. Source tracking analysis revealed that 37% of all bacteria in the hatchery rearing water were introduced either by the live or dry feeds, or during water exchanges. The contribution of the microbiome from the algae was the largest, followed by that of the Artemia, the exchange water and the dry feeds. Our findings provide fundamental knowledge on the assembly processes and dynamics of rearing water microbiomes and illustrate the crucial role of these peripheral microbiomes in maintaining health-promoting rearing water microbiomes.

Microalgae production cost in aquaculture hatcheries

Microalgae are a crucial part in many aquaculture feed applications processes, mainly in hatcheries. Many aquaculture hatcheries maintain a small scale microalgae production facility in-house for the production of live feed. Microalgae are usually grown in non-automated bubble-column systems at unknown production costs. Other reactor systems or scenarios utilizing artificial light or sunlight and at different scales could result in a more cost efficient production processes. To determine the cost-price and cost-distribution of microalgae production facilities in Dutch aquaculture industry and identify the most efficient cost reducing strategies a techno-economic analysis for small scale microalgae production facilities (25-1500 m2) was developed. Commercially available reactors commonly used in aquaculture were compared; tubular photobioreactors (TPBR) and bubble-columns (BC) in two placement possibilities; using artificial light in an indoor facility (AL) and utilizing sunlight in a greenhouse (GH) under Dutch climate conditions. Data from commercial microalgae facilities in the Netherlands are used to model reference scenarios describing the cost price of microalgae production with state of the art technology in aquaculture for a biomass production capacity of 125 kg year−1. The reference cost price for algae biomass (on the basis of dry matter) is calculated at €290,- kg−1 and € 329 kg−1 for tubular reactors under artificial light and a greenhouse, respectively and €587,- kg−1 and €573 kg−1 for bubble-columns under artificial light and a greenhouse, respectively. The addition of more artificial light will significantly reduce production costs (by 33%) in all small-scale systems modelled. Biomass yield on light (Yx,ph) showed the largest effect on cost price when not considering a different scale of the production process. Process parameters like temperature control should be aimed at optimizing Yx,ph rather than other forms of cost reduction. The scale of a microalgae production facility has a very large impact on the cost price. With state of the art technologies a cost price reduction of 92% could be achieved by changing the scale from 25m2 to 1500m2, resulting in a cost price of €43,- kg−1, producing 3992 kg year−1 for tubular reactors in a greenhouse. The presented techno-economic model gives valuable insights in the cost price distribution of microalgae production in aquaculture. This allows to focus research efforts towards the most promising cost reduction methods and to optimize existing production facilities in aquaculture companies to achieve economically sustainable microalgae production for live feed in hatcheries.

Bioconversion of Fish Hatchery Waste as Feed in the Production of Live Feed

Purple Non-Sulfur Bacteria (PNSB), also known as phototrophic bacteria are widely distributed in both freshwater and marine environment and capable to grow in wide range of substrates. In this study, Bacterium Rhodobacter sphaeroides strain UMS2, a freshwater isolate was used in this study in utilization of fish hatchery waste. This study was conducted to determine the nutritional values of bioprocess product that was grown in fish hatchery waste. Finally, the waste bio-converted product was used as feed supplement to monitor the growth performance of live feed Tubifex spp. Inoculum of Rhodobacter sphaeroides strain UMS2 was developed in 112 synthetic media and 48-h culture of 30% (v/v) inoculum was used in fish hatchery waste during the bioprocess. The nutritional values of bio-converted product, except total ash (%), were not significantly improved with 30% (v/v) inoculum of Rhodobacter sphaeroides, strain UMS2. Feeding trial in bloodworm (Tubifex spp.) with bioconversion product conducted for 15 days to monitor growth (w/v) of live feed. Initial growth 1.42 ± 0.001 g/L of Tubifex spp. was stocked in 15 × 75 × 15 cm plastic tray connected with recirculated system. Tubifex spp. was observed to be comparatively higher (1.55 ± 0.12 g/L) while fed in the product that contained bacterium than the growth (1.44 ± 0.15 g/L) of Tubifex spp. fed in the bioconversion product of without bacterium. The inoculums size (30%) of bacterium not enough to support the growth of Rhodobacter sphaeroides, strain UMS2 in the bioconversion process to improve the nutritional values. However, while used as feed supplement it improved the growth performance of the Tubifex spp. So, bacterium Rhodobacter sphaeroides, strain UMS2 has potentiality to be used as feed supplement in the production of live feed.

Characterization of Finfish Hatchery Waste for Value Added Product

Commercial fish hatchery generates waste both organic and inorganic; the sources are primarily from uneaten food and fish feces. Conventional methods of treating hatchery wastes will increase the operating cost and become extra burden in production. It is necessary to develop a new research application of this nonconventional resource and reduce the negative impacts of hatchery waste on the environment. The whole project is to utilize hatchery waste through bioprocess for probiotic fortified live feed production. In this study, the chemical composition of hatchery waste was determined to understand the suitability waste to get value-added derived products through bioprocess. Composite samples were collected everyday and dried in an oven at a temperature of 65°C until complete dryness. Dried samples were mixed well and grinded into fine powder. The analytical parameters like total solids, ammonium nitrogen, nitrite, nitrate and phosphate were determined from the freshly collected samples. Total nitrogen, total phosphorus and total potassium were determined from the dry samples. Total solids, ammonium nitrogen, nitrite, nitrate and phosphate-phosphorus were observed in the ranged from 75 - 82 mg/L, 0.25 - 8.5 mg/L, 0.05 - 1.9 mg/L, 0.04 - 6.7 mg/L and 4.1 - 16.7 mg/L respectively. On the other hand, the mean content of 3.75% total nitrogen, 1.80% total phosphorus and 0.15% potassium were determined in dry hatchery wastes. The analytical parameters are useful and demonstrate that the nutrients in both fresh and dry waste will be supportive for the growth of microbes in the bioprocess system.

Optimization of techniques and procedures for the production and management of live feed used in the larval culture of the freshwater shrimp Cryphiops caementarius (Decapoda: Palaemonidae)

The variation in saline requirements during larval development of Cryphiops caementarius establishes a particular coexistence in the culture systems between the shrimp larvae, the microalgae and Artemia nauplii. Although the technology for the mass production of freshwater prawn juveniles has advanced positively, the non-commercial availability of an exclusive live feed for amphidromous crustaceans, such as C. caementarius , has created the need to optimize the management of organisms commonly used as feed in the larval culture of marine crustaceans. We investigated the effect of salinity on embryonic development dynamics and the hatching rate of commercial Artemia sp. cysts, including the effect of cooling decapsulated cysts on the hatching rate, and the effect of salinity on the behavior of marine microalgae used as live feed in the larviculture of C. caementarius . The results encourage a sustained and stable production of Artemia nauplii at different salinities, and at the same time, reduce by 80% the daily time used in feeding activities. Also, the information generated in this study adds critical information about activities and procedures for the larviculture of the northern river shrimp, which could be used to improve larval feeding strategies either in C. caementarius or in other amphidromous crustacean species.

EFFECT OF THE C:N RATIO ON &lt;i&gt;Daphnia magna&lt;i&gt; (Straus, 1820) PRODUCTION USING TILAPIA FARMING WASTEWATER

The purpose of this study was to produce Daphnia magna in wastewater from Tilapia farmed in a biofloc system, to evaluate three different carbohydrate:nitrogen ratios. The experiment was conducted for 30 days following a completely randomized experimental design, with the three treatments: C:N 10:1, C:N 15:1 and C:N 20:1, all fed with Chlorella vulgaris. The physical-chemical variables of the water analyzed were: temperature, dissolved oxygen (DO), pH, TAN, NO2 , hardness and alkalinity. The following growth variables of the Daphnia were also evaluated: Maximum average density (MAD), Maximum density day (MDD), Specific growth rate (SGR), Doubling time (DT) and yield (Y). The water quality variables remained in the range of ideal conditions for the species, presenting significant differences (p &lt;0.05) among the treatments for: pH, DO, hardness and alkalinity. Regarding the growth variables, significant differences (p &lt;0.05) were observed, with higher MAD, Y and SGR values for the 10:1 treatment (3,433 ± 267 ind L-1, 245 ± 19 ind L-1 day- 1 and 45.3 ± 0.6% day-1, respectively) and lower for the 20:1 (1,011 ± 283 ind L-1, 55 ± 15 ind L-1 day-1 and 28.3 ± 1.6% day-1, respectively). The MDD occurred on day 12 for the 10:1 treatment and on day 18 for the 15:1 and 20:1 treatments. Alkalinity and hardness had stronger influence on the growth variables, which was also indicated by the simple linear regression. The principal component analysis (PCA), with 80% of explanation, identified high values of SGR, density and Y for the 10:1 and high values of alkalinity, hardness, DT and NO2 for the 20:1. Thus, the use of effluent from Tilapia farming in a biofloc system with a C:N ratio of 10:1 provided better production results for D. magna, demonstrating that it is an option for the production of live feed for aquaculture.

Is it possible to successfully rear meagre (Argyrosomus regius Asso 1801) larvae without using rotifers?

In hatcheries, meagre Argyrosomus regius larvae still depend on an adequate supply of rotifers and Artemia, as no artificial diet can totally fulfil their nutritional requirements. However, production of live feed is highly expensive and demands intensive labour and specific facilities. This study investigated the effect of a dietary regime without the use of rotifers, to simplify the meagre larval rearing protocol. Two feeding treatments (T1 & T2) are compared to investigate their effects on survival and growth of meagre larvae. In T1, larvae were fed rotifers from 2 to 5 days post hatch (dph), and Artemia from 4 to 15 dph. In T2, larvae were kept under dark conditions and fed Artemia from 6 to 15 dph. Standard larval length (SL) was significantly higher in T1 (p < .01) until 8 dph in comparison with larvae reared initially without rotifers. No significant difference in SL was found among treatments (p = .187) at 15 dph. Significant difference was found among treatments in survival rate at 15 dph (p < .003). The survival rate observed at 15 dph in T2 (30 ± 4.2%) represents an important finding, although the highest survival rate was observed in T1 (45.0 ± 3.4%). This study showed that it is possible to conduct larval rearing of meagre without using rotifers. Nevertheless, further research efforts are still needed to improve these results in comparison with the common larval rearing protocol.

Effects of different wavelengths and intensities of visible light on the hatching success of Acartia tonsa Dana eggs

Mass production of copepod eggs in intensive systems has recently been demonstrated to be economically feasible; a few companies producing copepod eggs have been established. It is well documented that water physiochemical variables could significantly influence the hatching success of Acartia tonsa Dana, 1849 (Copepoda: Calanoida) eggs. This information is important to end users in order to achieve a predictable output of nauplii when hatching eggs for live feed production in marine larviculture. The effect of different wavelengths and intensities of light on the 48-h egg hatching success (HS) of fresh and cold-stored (2 °C) A. tonsa eggs were examined in the present study. No correlations were observed between HS and light environment for fresh or cold eggs when they were hatched at wavelengths between 400 and 630 nm and at light intensities of 0.0016, 1, 5 and 16 µE m−2 s−1. Fresh eggs displayed the highest HS and declined with the time of storage. However, eggs being of same age showed a similar HS regardless of the light intensity and wavelength, including when hatched in darkness. We suggest that A. tonsa eggs produced in intensive cultures can be hatched without any concern to the light environment.

Embryonic cold storage capability from seven strains of Acartia spp. isolated in different geographical areas

Calanoid copepods from the genus Acartia are well studied because they are promising live feeds in marine larviculture. Several Acartia spp. are adapted to the occurrence of sudden unfavorable environmental conditions and can arrest their embryogenesis by entering quiescence. This trait can be used practically for establishing an egg bank, where embryos can be kept alive and hatched at a later time. The stored embryos can be shipped to end-users and the hatched nauplii used directly as live feed as well as they can be used to establish new copepod cultures. Acartia tonsa (Dana) is a cosmopolite and therefore an obvious candidate for being mass produced centrally at specific offsite installations, transferred and used worldwide. Moreover embryos from other species from this genus are shown in the present paper to have similar capacities in terms of survival in cold storage. To avoid the transfer of exogenous species in new environments, it is recommended to cultivate regional or even local species of copepods. In the present contribution we compare the cold storage capacity of embryos produced by seven strains of Acartia spp. isolated from different zoogeographical regions ranging from Northern Europe to the subtropical USA and tropical Asia. Our results showed that cold storage capacity of embryos is very dependent on egg size. The longest storage capacity, with egg hatching success >50% is demonstrated for embryos originating from temperate European waters and in particular from Adriatic Mediterranean and Baltic Sea waters (240 and 150days, respectively) while the shortest storage capacities were found from species from sub-tropical Mexican Gulf, USA (10days). Higher survival has a tendency to correlate with larger egg biovolume. However, we cannot exclude a possible and unknown unidirectional selection for embryo storage tolerance caused by the management practice in long term continuous cultures. We conclude that the studied embryos from the genus Acartia can all be stored for different time periods and hence are relevant for being used as regional/local egg banks and further studies for developing future live feed items. Statement of relevanceWe consider calanoid copepod live feed products as a valuable supplement or alternative source for hatcheries. This is due to the fact that by introducing copepod nauplii as first feed items more fish species with small mouth gapes will be cultivated. Copepod organisms cannot be shipped due to the fact that they are fragile organisms. However, their embryos in a cold storage situation enter arrested development that lasts viable for months. We investigate seven strains of Acartia spp. embryos for their capabilities to be cold stored and conclude that all strains have that capability. This is considered promising for future mass production of calanoids for the benefit of the industry.

A new large egg type from the marine live feed calanoid copepod Acartia tonsa (Dana)—Perspectives for selective breeding of designer feed for hatcheries

Abstract Mass cultivation of marine copepods as live feed requires predictable and uniform production of a standard product for the end users, the hatcheries. A previously undescribed large egg type, measuring a mean diameter of 106.5 μm, was characterized and compared to normal eggs (82.3 μm) from a continuous culture of Acartia tonsa. The large egg type was significantly larger than the normal eggs, and only 1 large out of approximately 100 000 normal-sized eggs was found. Mean egg densities was 1.34 ± 0.16 g/cm3 and 1.20 ± 0.07 g/cm3 for normal and large eggs, respectively. The hypothesis that large eggs were dormant, as indicated from the relatively low hatching success of 60%, within 48 h, was rejected as no significant difference was found in egg volume-specific respiration rates or histological analysis of the chorion between the two egg types. The nauplii hatched from large eggs were correspondingly large, and the copepods remained large when developing into adulthood. The fact that copepods hatched from large eggs were fertile indicates no chromosomal abnormalities and suggests that this egg type represents the upper tail end of eggs in a classical normal distribution of size vs. frequency. The next generations' eggs were not as large as the ones they originated from suggesting that the rare large eggs represent a maternal effect. The large size eggs do however pose an interesting selection potential for designing large species-specific live feed products in aquaculture.

Economic feasibility of copepod production for commercial use: Result from a prototype production facility

During the last three decades, it has been shown that copepods are a superior live feed for marine finfish larvae compared to other commonly used live feed items, such as Artemia and rotifers. The use of copepods, which have a better biochemical composition, increases survival rate, improves growth condition, reduces mal-pigmentation and allows breeding of ‘new’ marine finfish species. However, copepods are not yet commercially produced and therefore not widely used in the aquaculture industry. One of the bottlenecks for large-scale production has been lack of economic knowledge on the feasibility of producing copepods for commercial application. This is the first empirical study to investigate the economic feasibility of copepod production for commercial use. To this end, a standard cost-benefit analysis based on a prototype production facility of Acartia tonsa (Dana) eggs at Roskilde University, Denmark, is employed. The result reveals that commercial production of copepods is economically feasible considering the existing market prices on both copepods and competing live feed items such as rotifers. The study provides valuable information for businesses who consider investing in live feed production for marine finfish aquaculture. Furthermore, the study also highlights the economic benefits of production and utilization of copepods on productivity and species diversification in marine finfish aquaculture. • A prototype intensive production facility for the copepod species Acartia tonsa was built. • Unique data set was collected when the system was built and while it was running. • Cost-benefit analysis was employed to assess the economic feasibility of production. • Both NPV and IRR show that the production facility is economically viable and worthwhile. • Commercial application of copepods will enhance productivity growth in aquaculture.

Advances in the culture of striped trumpeter larvae: A review

Striped trumpeter, Latris lineata, was chosen as the best new candidate for sea cage culture in Tasmania in the late 1980s. It has a complex and extended post-larval or ‘paperfish’ stage lasting up to 9 months and has historically proven difficult to culture. Excellent progress has been made in understanding and controlling reproduction and broodstock are spawned year-round through photothermal control. Problems with early larval rearing have been overcome and egg incubation and early larval rearing protocols have been established. A mortality peak associated with first feeding has been reduced using better live feed production techniques and improved water quality. Using antibiotics showed that high bacterial loads were an important factor in larval mortality. A new water filtration and ozonation system has removed the need for antibiotics. Larval nutrition research focused on the link between potential deficiencies or imbalances in the three essential PUFA in live feeds: docosahexaenoic acid, eicosapentaenoic acid and arachidonic acid. Novel experimental emulsions were applied with dose response experimental designs to identify the dietary requirement for selected PUFA and vitamins. Despite the advances in live feed enrichments, the live feeds, particularly Artemia, were found to have sub-optimal lipid profiles. Copepods were cultured, as a supplement to traditional live feeds, and improved larval rearing success. Costs to scale-up production and to control extensive cultures presently restrict the usefulness of copepods. Important breakthroughs have occurred in health with the detection and control of nodavirus, myxozoan and bacterial disease. Ozone disinfection of eggs and sterilisation of hatchery seawater have been important control measures. Another bottleneck to production has been mortality of larvae from notochord flexion to metamorphosis. System changes to reduce nocturnal movements and a better understanding of optimal live feed densities, and weaning onto formulated diets, have improved survival and growth. High rates of jaw malformation remain a challenge and no definitive cause has been established. Reduced rates of malformations have been associated with one or a combination of high feed rates, lower larval densities and temperatures, and reductions in ‘walling’ behaviour. Future research is aimed at finding ways to reduce malformations, develop probiotics and early weaning strategies, control parasites and scale-up production to assess performance of juveniles in sea cages.

Estimating larval density in cod ( Gadus morhua) first feeding tanks using measurements of feed density and larval growth rates

Due to unpredictable mortality in larval cod rearing, a reasonably accurate estimate of the larval biomass in rearing tanks is important for production management such as determination of feed doses and planning of live feed production. A good estimate of larval numbers can also give an early warning if a larval group is suffering high mortality. Because direct measurement of the larval density is difficult, a model based estimator is developed to estimate the larval density from parameters that are simpler to measure, such as feed density and larval size. The estimator is based on an extended Kalman filter using measurements to update a process model. The estimator was tested by acquiring data on feed densities and larval growth rates in a first feeding experiment on cod. Cod larvae were reared from hatching up to day 16 post hatch in nine 160 l tanks at three different densities. The larvae were fed with rotifers ( Brachionus plicatilis) from day 3 until the end of the experiment. Results show that the estimator is able to correctly detect differences in larval density.

Design of a pilot-scale tropical marine finfish hatchery for a research center at Mazatlán, Mexico

A multispecies, 2668m2 pilot-scale tropical marine finfish hatchery was designed to fulfill the requirements of finfish juvenile research and development (R&D) at the Research Center for Food and Development, in Mazatlán, México. The main goals of the facility were (1) scale-up and study experimental results at a pre-commercial-scale; (2) assess technical and financial feasibility and improve these technologies before transfer to commercial-scale; (3) adapt technology to other fish species. In the hatchery, a semi-intensive, green water strategy is used for larval rearing, and rotifers are produced using a high density, intensive production technique. An intensive, tank-based nursery is used to study juvenile husbandry. Although the main objective of the facility is to package technology, the annual production capacity for juvenile to supply to industrial partners is about 160,000–200,000 one-gram juveniles produced in three or four rearing cycles. Seawater intake is based on a sand and gravel prefiltered system and two 30hp seawater radial pumps, each with the capacity to fulfill the whole system requirements (500gpm, 31L/s, sustained flowrate). Most of the water is delivered directly to the broodstock and nursery areas after sand and cartridge filtration and a UV lamp (≤60,000μWs/cm2), and the rest is used to fill four 25m3 high density polyethylene (HDPE) storage tanks. From the storage tanks, the seawater is directed through three pressurized sand filters and a series of high capacity cartridge filters (16μm). For live feed production and larval rearing, water is further filtered using line cartridge filters (as small as 0.22μm) and a continuous-flow UV lamp (≤60,000μWs/cm2). There is a freshwater system for 60m3/day and an air distribution system that includes three 10hp blowers, each with the required capacity for the entire facility. The broodstock areas have 40 tanks (0.6–50m3) with a total capacity of 410m3. Initially there are six 3m3 larval rearing tanks and in a second stage a 40m3 mesocosms tank facility will be added. The indoor (160m2) live food culture facility is capable of a daily production of about 8m3 of four microalgae species (1–40×106cells/ml, depending on the species), 2.5×109 enriched rotifers, 6×108 enriched Artemia metanauplii and 4×107 copepods.

Can Atlantic cod ( Gadus morhua) larvae be weaned faster onto dry feed at higher temperatures?

Live feed production is costly, labour intensive, and comprises a large proportion of the hatchery production cost. The cost of live food production required to culture marine finfish larvae such as Atlantic cod ( Gadus morhua) can be reduced by a shorter and more efficient weaning period. In this study, hatchery reared cod larvae were exposed to different temperatures while being weaned from Artemia (brine shrimp) to dry food from 45 days post-hatch (dph). In the first experiment, two temperatures were used: 11.5 and 7.5 °C. During weaning, the amount of Artemia fed to the larvae was gradually decreased while the dry feed was increased. Larval foraging behaviour and mortality were monitored. The growth rate and mortality of the larvae were not significantly different between the two treatments. However, the larvae in the 11.5 °C treatment showed a significant increase in the intake of dry feed. Thus, a second experiment was conducted at 11.5 and 14.5 °C to examine if weaning could be further improved. Results showed that the growth rate of larvae between the two temperatures did not differ significantly, however, mortality rate in 14.5 °C treatment was significantly higher than 11.5 °C treatment. Larval orientation towards and ingestion of dry feed were not significantly different in experiment two. Results of our experiments suggest that a possible optimal weaning temperature for larval cod between is 11.5 and 14.5 °C.