Asia-Pacific Marine Finfish Aquaculture e-News No. 36 (12/04/2007)
Dear Asia-Pacific Marine Finfish Aquaculture Network list,
The purpose of this e-News is to facilitate information dissemination on marine fish aquaculture research and development, complementing the quarterly marine finfish eMagazine. We welcome your contributions on research and development, news items, market developments, upcoming events and others - please send to
Finfish Aquaculture Network
1. New date for the 5th Regional Grouper Hatchery Production Training Course 2007 – NACA is pleased to announce the 5th Regional Grouper Hatchery Production Training Course for the Asia-Pacific Marine Finfish Aquaculture Network. The course is now rescheduled to 9 to 29 July 2007 to enable participants to attend an aquaculture conference in Bali (30 July to 3 August) if they wish. More information on this conference will be provided if becomes available.
The course structure will be similar to that of previous years, and new developments in grouper/marine fish breeding techniques will be included in the training course. For background information and the recent training you can download the 2006 training report. To register, please download and return the registration form. The training course fee is US$1,900 per person if registration and payment are received before the deadline (25th April). The training fee covers most lunches and some dinners, airport pickup, local transport for field trips and training course related activities only. The fees and payment deadlines are:
The hotel is around US$18-30/night/person inclusive of breakfast, depend of the type of room chosen. Participants will pay direct to the hotel, However, booking is made through the organizers. If you have further questions please contact Mr Sih Yang Sim at firstname.lastname@example.org.
2. APEC food safety cooperation agreement signed – An APEC’s Food Safety Cooperation Forum was held at the Hunter Valley, New South Wales, Australia in April 2007. The forum was to encourage regional APEC economics to work together to harmonise food safety regulations with international standards to improve health and food safety outcomes and facilitate trade. The major outcome from the forum was an agreed two-year work program recommending to APEC projects that strengthen food safety capacity building in the APEC region. For full article visit http://www.growfish.com.au/content.asp?contentid=8871.
3. FAO Fishery Statistics updated – An updated version of FAO Fisheries Statistics is now available online. Please visit FAO website at the following address which also include FishStat Plus – Universal software for fishery statistical time series. (http://www.fao.org/fi/website/FIRetrieveAction.do?dom=topic&fid=16073).
4. Sea fish cobia able to grow in freshwater – A Virginia company is using a patented technology to raise cobia (Rachycentron canadum), a marine finfish species, in low-salinity water without compromising taste, texture or nutritional content. The technology involves a protein that serves as a calcium-sensing receptor (CaSR), which is a “molecular thermostat”. For full article click here.
5. Breeding tuna like cattle a step closer – An Australia based company claimed that it has the world first breakthrough was achieved using hormonal therapy to stimulate male Southern Bluefin Tuna (SBT) to release sperm in captivity. The courtship behaviour and release of sperm by captive SBT was documented using underwater video camera. The next step for the company will be to stimulate the natural release of eggs from female SBT broodstock and their subsequent fertilization. For full article visit http://www.growfish.com.au/content.asp?contentid=8833.
6. Health management practices for cage aquaculture in Asia – An interesting article produced by InterVet. The article provides some information on the characteristics of Asian aquaculture, the enormous diversity of cultured species, the diversity of culture system and environment, and drawn a comparison with salmon farming in the west. The article also provides disease status in Asian aquaculture particularly on finfish species. It also covers some aspects on irresponsible use of chemicals/antibiotics, inadequate health management practice, etc. The article is a 17 pages article which also provide some practical recommendations to fish farmers in Asia. The full article can be downloaded from http://www.thefishsite.com/articles/264/health-management-practices-for-cage-aquaculture-in-asia-a-key-component-for-sustainability.
7. Aquaculture and Ecosystems: An Integrated Coastal and Ocean Management Approach – This book is the result of a workshop at which multidisciplinary teams of international experts in the fields of aquaculture, ecology, fisheries, geographic information systems, ecosystem modeling and coastal resource management presented and discussed inshore or offshore aquaculture case study scenarios that include marine aquaculture as a technology to improve coastal ecological function, carrying capacity and economic sustainability. The proceedings identifies key factors and parameters needed for ecosystem based management relative to aquaculture and how aqua culture can contribute to ecological function and better water quality in coastal areas. Country teams determined the status of balanced ecosystem approaches to coastal management in their countries and considered the modeling necessary for good decision-making when aquaculture is included in integrated coastal management. The book is available from World Aquaculture Society at Member Price: $45.00 and Non-member Price: $80.00. For further details visit WAS website.
8. Weekly Marine Fish Wholesales Prices in Hong Kong – April, 2007
The following web link provides marine fish wholesale prices in Southern China and Hong Kong. For details of average prices visit http://www.enaca.org/modules/news/index.php?storytopic=14&storynum=10.
9. Upcoming Events in 2007
10. Recent publications
Aquaculture, Volume 262, Issues 1, Pages 1-172 (14 February 2007): In this issue several articles on marine finfish may be of interest and abstracts are provided:
A relatively new and highly valuable aquaculture industry focuses on three species of bluefin tunas, which are captured from the wild and fattened for several months in sea cages. In teleost aquaculture, mortalities and extra production costs are very commonly associated with metazoan ectoparasites. In tuna, however, the production value lost due to diseases associated with ectoparasites is unknown. We collected epidemiological data on burdens of metazoans on the gills of farmed southern bluefin, Thunnus maccoyii, in a series of monthly samples of tuna from the time of stocking through to harvest (March to August, 2004; N = 210) in five sea cages on a farm off Port Lincoln, Australia. Three species were recorded; for one (a copepod, Pseudocycnus appendiculatus), there was a gradual, significant increase in both abundance (from a mean of 0.1 in March, to 3.83 in August) and prevalence (from 10% to 67.5%). For the other two species (a second copepod, Euryphorus brachypterus, and a polyopisthocotylean flatworm, Hexostoma thynni) there were no discernible trends in prevalences and abundances. These results contrast markedly with those of other intensively cultured species of finfishes, in which parasite epizootics are frequent. This finding may indicate that despite the stresses of captivity, tuna mount a robust immune response to ectoparasites; the relatively low stocking densities at which tuna are farmed may facilitate this. The fall in water temperature during farming (22 °C to 13 °C) may also reduce the reproductive rate of these ectoparasites.
The spawning behaviour of wild caught brood stock as well as
early egg and larval development were studied in yellowtail kingfish
(Seriola lalandi). Spawning occurred naturally in the
austral spring/summer (November–February) when the seawater
temperature was above 17 °C. Courtship behaviour involved one male
and female, and consisted of a high-speed pursuit punctuated by
stalling, nipping and touching. This lasted for approximately
0.5–1.5 h until, immediately prior to spawning, the male would nip
at the female gonoduct, presumably to induce spawning. At this
stage, in 50% of spawns, a second male would become involved. The
release of gametes involved frenzied circling behaviour near the
bottom of the tank and lasted approximately 22 s. Spawning occurred
in the early daylight hours at the start of the spawning season, but
shifted to around dusk in the latter part. Spawned eggs were
positively buoyant, had a high fertilisation rate (> 99%), ranged
1.33–1.50 mm in diameter with a single oil droplet 0.30–0.33 mm
diameter, and developed in a similar manner to that described in
congenerics. Egg viability within the floating fraction was visually
determined to be 74% ± 17% over the entire reproductive season.
Indistinct cell margins and asymmetrical cleavage were the most
common blastomere deformities observed. Egg and oil droplet volume
were found to decrease by 15–20% over the spawning season, though no
relationship was found between visually assessed egg viability and
date. Egg incubation trials between 16 and 24 °C indicated that
temperature accelerated the time to hatch by a Q10 of
5.0. While larvae were found to hatch at a smaller length with a
larger yolk sac and oil droplet at warmer incubation temperatures,
there was little difference in the maximum larval length reached at
the onset of first feeding among the rearing temperatures used. It
is proposed that the reason for this was that higher incubation
temperatures accelerated the hatching process faster than the rate
of tissue deposition. The findings from this study are discussed in
terms of the biological significance and implications for the
larviculture of this species.
The food chain has been postulated as one pathway for tetrodotoxin (TTX)-producing bacteria to enter into fish. However, the background composition of the bacterial community in puffer fish is unclear. Using 16S rDNA PCR denaturing gradient gel electrophoresis (PCR-DGGE) technology, we investigated the composition of bacterial communities in the skin, intestines, and TTX-accumulating organs (ovary, liver) of the striped puffer fish Takifugu obscurus. A total of 38 species of different culture-independent bacteria were isolated and classified according to phylogenetic analysis. Of these species, those belonging to the class γ-Proteobacteria dominated the microbial community in the puffer fish, while others belonged to the group of low DNA G + C content, Cytophaga–Flavobacterium–Bacteroides (CFB) group, α-Proteobacteria, β-Proteobacteria, ε-Proteobacteria and Spirochaetales. Gram positive bacteria of the group of low DNA G + C content were seen as the dominant component in the intestine, while γ-Proteobacteria was the dominant group in the skin or TTX-accumulating organs. The TTX-accumulating organs were found to contain bacteria from all TTX-producing genera reported previously. We also observed large differences in the bacterial assemblages in the intestines of fish fed natural and artificial diets.
Sub-adults of silver pomfret (Pampus argenteus), produced and reared in the mariculture experimentation facilities of Mariculture and Fisheries Department of Kuwait Institute for Scientific Research (KISR), suffered 55–70% mortalities due to scuticociliatosis by Uronema sp. The parasitic infestation was noticed during April–May 2005. Affected fish showed varying levels of tissue damage including severe epidermal and dermal necrotic lesions. The disease occurred with the raise in water temperature from 20 to 22 °C during April. Loss of scales, appearance of bleached spots that coalesced to form brownish patches, haemorrhagic and severe dermal necrotic lesions were the major clinico-pathological manifestations. The parasite was found abundantly in the blood, peritoneal fluid and the cerebrospinal fluid, the skin and the gill wet mounts. Extensive fouling, necrotic degeneration of the gill epithelium and deep dermal necrosis resulted in mortality of the infected fish. The parasite was noticed in the lumen of the collecting ducts of the kidney and the alimentary canal. The parasite was also seen distributed extensively in the entire brain causing widespread nerve necrosis. Earliest separation of the clinically normal fish from the affected fish resulted in significantly higher survival. The investigations are of significant importance in view of the mariculture potentials of the fish especially after the success of captive spawning and larval rearing achieved by the KISR.
Growth of fouling organisms on suspended fish cages is an impediment to aquaculture projects in coastal waters around the world. The present study characterized ecological succession of fouling communities on the netting of fish cages at an open ocean aquaculture site 10 km east of New Hampshire, USA in the western Gulf of Maine. Ecological succession can be defined as the process by which a community moves from a simple level of organization to a more complex community. Routine cleaning of the cages causes loss of organisms and initiation of ecological succession. Experimental panels of nylon net material were deployed at different times of the year and for different durations from September 2002 to September 2003 (eleven sets of 1-month panels, four sets of 3-month panels, two sets of 6-month panels, and one set of 1-year panels), with four replicates of each deployment. Panels were randomly arranged on a grid that was attached to a fish cage at a water depth of ~15 m. There were substantial and significant differences in density and biomass of the total communities of most successional sequences when comparing panels deployed during May–September to those deployed during the cooler months, October–April. However, the blue mussel, Mytilus edulis, dominated in density and biomass in almost every sequence, regardless of time of initiation or duration. Other species that occurred in high numbers and/or biomass were the amphipods Caprella sp. and Jassa marmorata, the molluscs Hiatella arctica and Anomia sp., the seastar Asterias vulgaris, and the anemone Metridium senile. Juveniles and adults of some species were also present in some early (1-month) successional sequences, indicating that migration may be an important process in community development. Some of the dominant species listed above were present in all successional stages (early, intermediate and late), differing only in relative abundances in the community. The consistent dominance of M. edulis, and other differences in successional patterns compared to what has been typically observed for epifaunal communities in the region, were hypothesized to be the result of a combination of factors: a lack of predators such as seastars and fish that typically consume mussels in natural communities, excessive predation by nudibranchs on those species (e.g., Tubularia sp.) normally abundant in early successional stages, year-round availability of mussel larvae, and cage cleaning protocols that do not remove all the organisms present. The introduction of predatory fishes or seastars into or onto the cages might provide some amount of control on the growth of fouling organisms.
The expansion of artificial habitats and aquaculture activities in coastal environments has been accompanied by an increased demand for tools to mitigate the effects of biofouling pests. One approach is to manage anthropogenic pathways to prevent the spread of established pest organisms to uninfected localities that are beyond their natural dispersal capacity. This paper describes the efficacy of acetic acid treatments against a variety of cosmopolitan fouling taxa, and evaluates a potential application in the treatment of foulers transported with movements of shellfish seedstock between mussel farming areas in New Zealand. Laboratory and field experiments demonstrated that immersion in 4% acetic acid (in seawater) for as little as 1 min can eliminate many soft-bodied fouling organisms, with lower concentrations requiring longer immersion times. The effects of immersion treatment were enhanced when combined with a 24-h air exposure phase to simulate the inter-regional transport of mussel seedstock. We demonstrate that it is possible to cost-effectively treat mussels to eliminate the majority of problematical foulers without resulting in significant adverse effects to the stock either by: (i) a 4% treatment followed by a rinse to remove the acetic acid residue before transport, or (ii) application of the 4% treatment at the end of the transport phase. A concentration of 4% is equivalent to the acetic acid content of domestic vinegar, hence does not represent a significant environmental or occupational risk provided appropriate measures are put in place for handling and waste disposal. Acetic acid concentrations remain stable over time in the presence of organic matter, but may change during repeated use of treatment solutions. To ensure treatment criteria are being achieved, field determination of acetic acid levels can be made using simple titration-based approaches. Because of an apparent buffering effect in the case of sequential shellfish seedstock immersion, pH could not be used to estimate acetic acid concentrations in this instance, but may provide a simple and reliable field-based indicator for other fouling treatments. Further work to refine the treatment method should seek to maximise the ‘window’ between pest mortality and mussel survival, to provide assurance that high-risk species can be eliminated with minimal risk of adverse effects on seedstock. Where treatments that are completely effective against all pest organisms result in unavoidable mussel mortality, decisions about whether or not to apply them must balance treatment costs and benefits against the unmanaged risks and consequences of pest incursion.
The Brazilian flounder, Paralichthys orbignyanus, is a promising candidate for aquaculture, especially due to the euryhalinity demonstrated experimentally for large juveniles (3 g) and sub-adults. Flounder are observed in estuaries and were already reared in fresh and salt water, however little is known with respect of salinity tolerance during their early development. The objective of this work was to evaluate the effects of salinity from fertilization to juvenile settlement. Three experiments were conducted to evaluate the effects of salinity. In trial 1 adult flounder were captured in the wild, transferred to the laboratory and induced to spawn. The gametes were hand striped, split in four samples and fertilized with water at 10, 15, 25, and 35‰. Eggs were considered fertilized when the first cell divisions were observed under the microscope. For the trial 2 newly hatched larvae were reared in four salinities (5, 10, 20, and 30‰) and their growth and survival were observed until metamorphosis. In trial 3 larvae and juvenile of different ages (6, 16, 30, 45, and 60 dah — days after hatching) were evaluated for their tolerance to fresh water. Although the fertilization rate was directly proportional to salinity, hatching was successful only in full salt water. Larvae did not survive in low salinity water (5‰) longer than 6 days, whereas growth was improved when larvae were reared at 20 and 30‰. Young larvae cannot survive in salinities below 4‰, but at 30 dah juvenile presented 100% survival in fresh water. The present findings demonstrate the need for high salinity water (30–35‰) for the successful reproduction and incubation of P. orbignyanus eggs. Flounder can be reared successfully at intermediate salinities (20‰) during larviculture, but at lower salinities (5 and 10‰) their survival and growth are impaired. However, immediately after flounder metamorphose into juveniles they survive even in fresh water, demonstrating the strong euryhalinity of this species even at early stages of development.
· Inclusion of citric acid and/or amino acid-chelated trace elements in alternate plant protein source diets affects growth and excretion of nitrogen and phosphorus in red sea bream Pagrus major, by Md. Shah Alam Sarker, Shuichi Satoh and Viswanath Kiron (Pages 436-443)
Nutrient dense diets not only challenge the physiological capabilities of fish but also result in discharge of excess amounts into the environment, causing eutrophication of the receiving water. This study investigated the effect of dietary levels of citric acid (CA) and/or amino acid-chelated trace element (AA-CTE) on growth and nutrient retention in red sea bream and loading of phosphorus (P) and nitrogen (N). Six practical diets were formulated, the control being a fish meal-based diet (F0) without addition of P, CA and AA-CTE. Diet F1 was supplemented with 1% mono calcium phosphate (0.25% P). In diets C1 and C2 fishmeal was replaced with alternate plant protein ingredients and supplemented with 1% and 2% CA, respectively. Diets A1 and A2 were akin to diets C1 and C2, respectively but contained AA-CTE instead of the inorganic trace element. Fish weighing around 12 g were offered the respective diets to satiation during the 12-week trial. Growth and feed performance were lowest for fish fed F0 diet, but significant improvement (P < 0.05) was noticed among those fed diets supplemented with P, CA or AA-CTE. The F1 group had the best growth (final body weight 85.02 g) while A1 group had the best FCR (1). Absorption of P was significantly higher (P < 0.01) for fish that received CA and/or AA-CTE (C1, C2, A1 and A2) compared to group that did not receive them (F0 and F1). The P and nitrogen (N) retention values in fish fed diets with CA and/or AA-CTE were significantly (P < 0.01) greater compared to the rest and this facilitated a reduction in excretion rates. The diet supplemented with 1% CA to an alternate plant protein sources diet without inorganic P supplementation had better performance compared to the diets supplemented with 2% CA, 1% CA + AA-CTE, and 2% CA + AA-CTE. Thus, without addition of inorganic P, 1% CA supplementation to alternate plant protein sources diets significantly improved fish growth, FCR and nutrient retention, besides lowering N and P loading. An efficient level of CA is suggested to be 1% or less in alternative plant protein source diets (containing 35% fish meal). These findings would contribute to the pursuit of environment-friendly feed for red sea bream.
The present study examined the effects of dietary vitamin A (vitA) deficiency and excess on growth, serum anti-bacterial activity and serum enzyme activities of juvenile Japanese flounder, Paralichthys olivaceus. Three semi-purified diets containing 0, 10,000 and 25,000 International Units of vitA per kg of diet (IU vitA/kg) were fed to juvenile Japanese flounder (initial weight 1.59 g) for 120 days. At the end of the feeding trial, blood samples were taken from the fish for haematocrit, serum biochemical analysis and serum anti-bacterial activity. Growth performance, in terms of weight gain and specific growth rate, was improved significantly (P < 0.05) with the addition of vitA to the diet. Total retinol contents in the liver increased with increasing dietary vitA levels. Haematocrit values did not show significant difference among the groups, but the values tended to increase with increasing dietary vitA levels. Serum total protein and albumin contents, and glutamyl oxaloacetic transaminase (GOT) activity tended to be lower in fish fed with 10,000 IU vitA/kg but significant difference was not observed among the groups. Serum total bilirubin content was significantly higher in treatment with no vitA than the other treatments. Glutamyl pyruvic transaminase (GPT) activity was significantly higher in the fish fed 25,000 IU vitA/kg than the other two groups. Serum anti-bacterial activity was significantly higher in the groups fed with 10,000 and 25,000 IU vitA/kg than that of the fish fed with 0 IU vitA/kg. These data suggest that dietary vitA significantly improved the growth performance and anti-bacterial activity of juvenile Japanese flounder. The tendency observed of high values in the blood serum parameters of the fish the diets of 0 and 25,000 IU vitA/kg after 120 days, suggests some negative effect on the liver (the main vitA storage site).
Gilthead sea bream cultured along the northern Mediterranean coast are affected by the winter season when low temperatures reduce fish feed intake and growth. The coldest episodes can provoke a fish pathology known as ‘winter disease’. The effects of low temperatures, as well as concurrent fasting, have been studied by transferring three groups of gilthead sea bream from 16 °C to 14 °C, 12 °C and 8 °C. Fish at 12 °C and 8 °C refused food, whereas those at 14 °C were not fed following the temperature drop. Changes in body indices, organ composition, liver metabolism, and in particular, lipid fractions and their fatty acids were analysed on days 7 and 20 after the temperature shift. Only the rapid reduction of non-polar lipids in muscle was common for the three conditions. Fasting effects were linked to the maintenance temperature, being maximal after 20 days at 14 °C where fish body weight, hepatosomatic index, and perivisceral fat were reduced by 18%, 40%, and 60%, respectively. In this group, liver lipids did not change, as was the case for the enzymatic activities of liver glucose-6-phosphate and phosphogluconic acid dehydrogenases (G6PDH and PGADH) and lipoprotein lipase (LPL). In contrast, the liver of sea bream submitted to 8 °C accumulated large amounts of non-polar lipids (from 80 mg to 125 mg in 20 days), changing in size and aspect (bigger, pale, and friable). Simultaneously, liver LPL and hepatic lipase (HL) activities decreased. After 20 days at 8 °C, sea bream exhibited incipient acclimation responses to low temperatures: rising levels of unsaturation ratio in gill and liver polar lipids, of docosahexaenoic acid (DHA) in muscle polar lipids, and of G6PDH and PGADH hepatic activities. Fish at 12 °C presented some changes similar to those of the group at 14 °C (e.g., in morphological indices, and LPL and HL activities) and others like the group at 8 °C (increases in G6PDH and PGADH), suggesting a temperature threshold for gilthead sea bream (below 13 °C).
Embryo dechorionization is a common practice used in certain fish species for different purposes. It facilitates techniques like microinjection, transfection or electroporation in embryos. Dechorionization is easily achieved in some fish species but is a more complex problem in species that have very thick chorions. In this study, we address this problem in turbot embryos, where chorion removal is practically unachievable post-chorion hardening. For this purpose, different solutions that lacked ions required for the hardening of this envelope or contained inhibitors of enzymes involved in the process were used during egg fertilization. The toxicity of the solutions was assessed, and their effect on embryo cleavage and on chorion structure was studied by light and scanning electron microscopy (SEM). The results demonstrated that embryos are very sensitive to these solutions and that first cellular cleavages are affected with most of them. This study also provides the first report on turbot chorion structure, analyzed by SEM. The chorion is a very thick envelope in this species, and its total removal was not observed with the employed treatments. Nevertheless, partial dechorionization was achieved when embryos were fertilized in some of the tested solutions and later treated with pronase (3 mg/ml).
Aquaculture, Volume 263, Issues 1-4, Pages 1-324 (6 March 2007): In this issue several articles on marine finfish may be of interest and abstracts are provided:
In the present study, the quality of post-thaw sperm of red seabream Pagrus major frozen with 6–24% DMSO was investigated. The motility, average path velocity and fertilizing capacity of fresh and their corresponding post-thaw sperm were examined for evaluation of the post-thaw sperm motion characteristics and its association with fertilizing capacity. An analysis of sperm motility before and after cryopreservation has been performed using computer-assisted sperm analysis (CASA). For post-thaw sperm frozen with 12–21% DMSO, the percentages of motile sperm were not significantly (P > 0.05) changed 10 s after activation. Moreover, the main motility pattern and swimming velocity of the motile post-thaw sperm were not significantly (P > 0.05) changed and the progressive linear motion was still the dominant pattern. However, the total motility of post-thaw sperm (72.3 ± 6.3%) 30 s after activation was (P < 0.05) lower than the corresponding fresh sperm (82.7 ± 7.2%). Additionally, the fertilizing capacity of post-thaw sperm was investigated with a standardized sperm to egg ratio 500:1. There is a linear regression relationship between the percentage of motile post-thaw sperm and fertilizing capability. These data demonstrate that 12–21% DMSO can provide good protection to the sperm during the freezing–thawing process.
Pre-slaughter and killing procedures can be regarded as prominent topics in fish culture management. Pre-slaughter procedures should be carried out without causing avoidable excitement, pain, fear or stress conditions, so to assure not only acceptable standards of fish welfare, but also high quality fish fillets. With regard to the sea bass and the sea bream, this paper aims to describe the effects of routine pre-slaughter and killing procedures on some stress indicators and, accordingly, on the fish welfare as well as on the quality of the resulting product. Two pre-slaughter procedures (low and high density) and two killing methods (asphyxia in air and asphyxia in chilled water at 1,4 ± 1 °C) were compared in cultured Mediterranean sea bass and sea bream. Both species were bred in a tank supplied with sea water at 11 °C pumped by a flow-through system. The time necessary to get to an unconsciousness status was recorded. The onset and development of Rigor mortis were also studied. Moreover, for the first time for the species of interest, the production of reactive oxygen metabolites (ROMs) as well as the anti-oxidant power (AOP) were investigated. A specific standardised micro method was employed in either case. The time necessary to reach irreversible unconsciousness, muscle pH and Rigor state proved to vary significantly depending on the pre-slaughter and slaughter procedures adopted. Fish asphyxiated in air turned out to struggle longer than those killed in chilled water, whether crowded or uncrowded. Uncrowded fish died earlier than crowded fish in both species. Anyway, our data on the development of Rigor suggested that both ordinary killing methods were highly stressful. ROMs values as well as AOP values were relatively low, in comparison with other animal species previously tested by the same methods. As far as ROMs are concerned, the sea bream showed higher values than the sea bass. For both species, a negative correlation between ROMs and AOP was observed in crowded fish, whereas a positive correlation was recorded in uncrowded fish.
The present work describes an easy to operate recirculated maturation system for different types of marine ornamental decapods that: i) demands shorter periods of time to perform routine tasks, while allowing better water quality for broodstock keeping, ii) eliminates the need to capture ovigerous females (or euhermaphrodites) before larval release, minimizing the risks of disrupting reproductive pairs, iii) separates newly hatched larvae from the reproductive pair, impairing adults from preying on larvae and iv) allows live prey to be provided to larvae immediately after hatching if needed. Breeding pairs of the following species were used to test the maturation system: cleaner shrimp Lysmata amboinensis, fire shrimp L. debelius, Monaco shrimp L. seticaudata, peppermint shrimp L. boggesii, cleaning rock pool shrimp Urocaridella antonbruunii, sexy shrimp Thor amboinensis, dancing shrimp Rhynchocinetes durbanensis, boxer shrimp Stenopus cyanoscelis, S. hispidus, hermit crabs Clibanarius tricolor, C. erythropus and the emerald crab Mithraculus sculptus. Larger species displaying strong agonistic behavior toward conspecifics (L. debelius and S. hispidus) had to be kept in larger divisions (0.20 m × 0.30 m × 0.15 m), while all other species were successfully kept in smaller divisions (0.20 m × 0.15 m × 0.15 m). All tested species were able to successfully mate and produce consecutive larval batches during the experimental period, and routine tasks (e.g. checking for and collecting newly hatched larvae, monitoring molts of breeding pairs, recording the presence of specimens carrying embryos about to hatch, tank siphoning, filters cleaning and water changes) were daily performed in about 1 h. The unidirectional water flow inside each maturation tank, as well as the presence of actinic light in the front glass, allowed newly hatched caridean, stenopodid, anomuran and brachyuran larvae to be successfully removed from the chamber containing the reproductive pair. The simple use of 150 μm mesh size screens inside maturation tanks allowed larval prey (Artemia nauplii) to be provided to larvae immediately after hatching, avoiding the negative effects of early larval starvation. The use of suitable maturation and larviculture systems will play a vital role for the successful development of profitable commercial scale culture protocols for the most heavily collected marine ornamental decapod species.
Trash fish used as aquafeeds in marine cage cultivation sometimes induced environmental risk. In this study, nitrogen, phosphorus, and energy waste outputs were measured in four marine cage-cultured carnivorous fish species – Sciaenops ocellatus, Plectorhynchus cinctus, Epinephelus coioides, and Rhabdosargus sarba – fed with trash fish for 6 weeks in laboratory. Waste outputs of cultured fish were divided into soft tissues in uneaten feed, bones in uneaten feed, scales in uneaten feed, soluble uneaten feed, solid faeces, soluble faeces, urine, caducous scales, and other parts. The results showed that an increase in 1 g of fish mass produced: 1) 34.4–67.2 mg nitrogen in urine, uneaten feed, faeces, and caduceus scales; 2) 3.4–10.9 mg phosphorus in uneaten feed, faeces, and caduceus scales; and 3) 12.0–23.8 kJ in metabolism, uneaten feed, urine, and caduceus scales. In the nutrient budget, urine was the most important component of nitrogenous waste and accounted for 7.8–14.4% of total nitrogen input. Bones and scales in uneaten feed carried the bulk of phosphorus waste, and these accounted for 4.1–13.8% of total phosphorus input. Metabolism was the largest energy consumed and it accounted for 12.0–20.8% of total energy input. The ratio of energy:nitrogen:phosphorus in waste outputs was 1.0–1.4:3.9–4.5:1. The information on nutrient and energy in waste output of the four fish in this study would help to assess and predict pollution of trash fish used as aquafeeds.
We have studied the possible use of soybean meal (SM) in sharpsnout seabream diets by progressively increasing its inclusion level (0%, 20%, 40% and 60%) at the expense of fish meal in isonitrogenous (45%) and isoenergetic formulated (20 MJ/kg) diets. Fish of two different sizes (48 g and 195 g of initial weight) were kept in seawater tanks (26 °C on average) and fed to satiety until they reached a weight of 118 g and 340 g, after 64 and 91 days respectively. Feed consumption increased along with the soybean meal content of the diet, the differences becoming statistically significant in smaller animals as from 40% of inclusion. In larger animals, the diet containing the highest level of soybean meal produced the lowest final weight. As the soybean meal content increased, feeding efficiency and protein utilization of the diet decreased, an effect probably due to the smaller digestibility coefficient observed for these diets. Based on the results of the sensory test, flesh quality was very little affected, albeit fish feeding on diets with partial replacement of fish meal tended to be somewhat softer. Despite extending the fattening period required to reach the same final weight, the economic analysis indicates that inclusion of soybean meal in the diet reduces feeding costs.
The aim of this study was to determine the impact of dietary replacement of fish oil by vegetable oils on sharpsnout seabream growth, nutritive utilization, somatic parameters, body composition, feed digestibility, and muscle fatty acid profile, as well as to make an estimate of its economic repercussions. To this end, three isonitrogenous (48% crude protein) and isoenergetic (23 MJ/kg) experimental diets were formulated, using three different lipid sources: fish oil (FO), soybean oil (SO) and linseed oil (LO). These diets were fed to triplicate groups of 30 sharpsnout seabream with an initial average weight of 14.9 g, three times a day to apparent satiation, over 92 days at 24.6 ± 1.1 °C. Our results show that the replacement of fish oil with soybean or linseed oil in sharpsnout seabream diets does not affect growth or feed utilization after three months of feeding. Fish on an SO diet exhibited higher hepatosomatic indices, whereas fillet percentages were significantly lower in fish that had been fed an FO diet. Apparent digestibility coefficients for dry matter, crude protein and crude lipid were significantly lower in fish that had consumed an LO diet. The muscle fatty acid composition reflected that of the diet. Consumption of vegetable oils reduced the muscle content of ARA (arachidonic acid), EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) to a lower degree than their corresponding reductions in the diet after fish oil replacement, which highlights their importance. Vegetable oils also increased the muscle content of linoleic and linolenic acids. In terms of economic performance, the SO diet was the least expensive diet, and had the best economic conversion ratio.
A quantitative approach is presented to evaluate fatty acid incorporation in fish. Fatty acid composition of European sea bass juvenile was studied during an experiment using 6 isoproteic (54%) and isolipidic (18%) diets containing 0.23, 0.56, 0.72, 0.86, 1.01 and 1.86% DM n-3 highly unsaturated fatty acids (n-3 HUFA). Whole body fatty acid compositions were studied at the beginning and after 52 and 81 days feeding, fatty acid profiles evolved during time under dietary influences. Incorporations of individual fatty acids into total lipids were calculated as increases in individual fatty acids as percentages of the increase in total fatty acids during growth, on a per animal basis. Relative incorporations (RI) so defined generated similar profiles for the two periods for each dietary treatment, consistent with fatty acids being incorporated in a stable way during the experiment. For most fatty acids, linear regressions could be drawn between RIs in whole fish and % of fatty acids in dietary lipid. RIs for DHA, EPA and AA demonstrated these HUFAs were incorporated in the fish in lower proportion that diet contents, in this experiment. Fractional retentions (FRs) of individual fatty acids were also calculated by dividing the quantities of given fatty acids present in lipid accumulated by the fish by the quantities of corresponding fatty acids ingested in the diet. Lipogenic activity was evidenced by 16:0 and 18:0 having FRs greater than unity. FR values greater than unity for 18:3n-6 and 20:3n-6, and 18:4n-3 in diets containing low levels of HUFA demonstrated some bioconversion capacity from 18:2n-6 and 18:3n-3 precursors, respectively. FRs for n-3 HUFA were negative in fish fed 0.2% n-3 HUFA. In other treatments FRs of n-3 HUFA were 0.5 to 0.6, lower than other dietary fatty acids as linoleic (0.75) or linolenic (0.70) acids. Results indicated a basal loss of DHA estimated around 14 μg g− 1 ABW d− 1 during the experiment. We conclude that dietary requirements of HUFA by marine fish comprise not only quantities required for production of polar lipids during growth, but also quantities required to replace losses probably induced by the active roles of HUFA. The results also indicate that RI and FR transformations are useful tools for better understanding fatty acid incorporations in juvenile fish.
The larval ontogeny of redbanded seabream Pagrus auriga was studied histologically and histochemically from 0 until 30 days after hatching (DAH). According to the source of food and the structural changes in the digestive tract, larval development was divided into four stages: (1) lecitotrophic (0–2 DAH), (2) lecitoexotrophic (3–4 DAH), (3) exotrophic I (5–15 DAH), and (4) exotrophic II (16–30 DAH). During the first three stages, larvae underwent an intense organogenesis, this being particularly intense from stage 2 (mouth and anus opening) to early stage 4 (appearance of gastric glands). Subsequent development during stage 4 was characterized by the proliferation and growth of pre-existing structures. During stage 1, the mouth and the anus were closed and the digestive tract undifferentiated (straight tubular segment), as well as the majority of the organs (observed as undifferentiated cells groups or primordial structures). As resorption of endogenous reserves proceeded (3–4 DAH) larvae acquired initial absorptive and digestive equipments necessary for first feeding (enterocytes brush border, zymogen pancreatic granules, and ducts connecting accessory glands to the gut). During stage 2, the digestive tract started to differentiate and buccopharyngeal cavity, oesophagus, incipient stomach, and anterior, mid and posterior intestine were distinguished. During stages 2 and 3, prey capture became guaranteed (early development of jaw, fins, teeth, and taste buds) and the digestive and absorptive processes continued developing (appearance of the gut mucosa folds and protein supranuclear inclusions and lipid infranuclear vesicles in enterocytes). The endocrine elements (Langerhans islets and thyroid follicles) except corpuscles of Stannius appeared from 3 to 5 DAH (mouth opening and total yolk resorption). During stage 2 and early stage 3 (3–7 DAH), the circulatory and excretory systems became functional, with the compartmentalization of the heart and the development of renal corpuscles, tubules, and collecting ducts. The beginning of stage 4 was marked by the appearance of gastric glands (16 DAH), which subsequently proliferated in association with the increase in size of the accessory glands. Such event ensured the development of gastric digestion, which around 30 DAH became fully guaranteed (transition from larval to juvenile stage). During stage 4, gill filaments and lamellae proliferated, the heart completed its compartmentalization, the pronephric and mesonephric regions in the kidney developed, and endocrine elements proliferated. The structural information presented here constitutes an initial step towards the determination of the functional systemic capabilities of P. auriga larvae, and thus the physiological requirements needed for optimal welfare and growth.
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