Academic literature on the topic 'Barramundi (Lates calcarifer)'

The most common problem in barramundi Lates calcarifer seedling production is the high mortality (> 90%) caused by nervous necrosis virus (NNV) infection. This research aims to evaluate the resistance and gene expression of barramundi challenged by NNV. Two populations were used in this study, i.e., Australian, and Situbondo-originated barramundi populations. The immune-related gene expression levels in the liver, head of kidney, and spleen were observed at 48 and 96 hours after post-infection (hpi). Barramundi’s survival and blood parameters were evaluated post-NNV infection. The results showed that the highest survival was revealed in Situbondo’s barramundi (42.0±4.47%) compared to Australian barramundi (20.0±7.07%) and no mortality was observed in the control without NNV infection. The higher survival rate in barramundi from Situbondo was in line with the blood profile. The number of red blood cell from Situbondo barramundi post-NNV infection (ST) at 96 hpi was higher (P<0.05) than Australian barramundi post-NNV infection (AT). The number of white blood cell of ST at 48 hpi was higher (P<0.05) than AT, but started to decrease at 96 hpi in ST barramundi. The total white blood cell in AT barramundi increased from 48 to 192 hpi. TNFα and IL1-β gene expression levels were significantly higher in the liver, head kidney, and spleen of Situbondo compared to Australian barramundi at 48 hpi, while MHCIIα gene expression in Situbondo’s was significantly higher compared to Australian barramundi at 96 hpi. These results indicate the important roles of all the genes in the barramundi’s immune responses against viral infection. Based on the results of the research, Situbondo’s barramundi has the potential to be used as a candidate for generating broodstock of disease-resistant strain.

Barramundi (Lates calcarifer) is one of the commercial fish in Indonesia. The phenomenon of climate change due to global warming has affected the life of aquatic biota, including fish. The objectives of the present study were to determine a critical thermal maximum (CTMax) and the behavior of Barramundi (L. calcarifer) due to the increase in water temperature. The research was conducted at the Fishing Technology Laboratory, Faculty of Marine and Fisheries, Universitas Syiah Kuala in February 2021. The experiment was conducted in 10 aquariums equipped with heaters. The initial temperature of the treatment was 28oC and increased gradually every one minute by 0.2oC. The results showed that the abnormal behavior of Barramundi fingerling was started to appear at 37oC where the fish began to swim fast, then swim sideways at 38oC-39oC, hit the container wall at 39oC-40oC, jumped and weakened then dead at 40oC and 41oC. The average critical temperature of Barramundi fingerling was recorded at a temperature of 41oC within 65 minutes. Therefore, it is concluded that the Barramundi (L. calcarifer) display an abnormal behavior above the temperature of 35oC, however, they can survive up to 42oC exposure for 70 minutes.Keywords:Critical thermal maximumTemperature riseGlobal warming

Barramundi, L. calcarifer, were collected from seven localities in the Northern Territory, the Daly, Finniss, Mary, Glyde, Roper and McArthur rivers and Blue Mud Bay, and from the Ord River in Western Australia. Barramundi were sampled seven times from the Daly and Finniss rivers over a 14-month period. In total, 46 loci were identified using starch-gel electrophoresis of enzymes and polyacrylamide electrophoresis of muscle proteins. Twelve loci were polymorphic at the P0.99 level. Most loci were in Hardy-Weinberg equilibrium. A contingency Χ2 analysis for homogeneity of alleles over all loci and all localities was highly significant (P < 0.001). Comparisons of data from adjacent pairs of localities revealed that the overall heterogeneity was attributable to heterogeneity among seven of the eight localities; the Daly and Finniss river areas were not significantly different from one another. No evidence of heterogeneity over time was found among the collections from the Daly River area. The considerable amount of heterogeneity observed suggests that each of these seven localities supports a genetically discrete stock of barramundi; this conclusion is consistent with the documented life history of Australian barramundi. The genetic heterogeneity of the stocks should be considered when management policies for L. calcarifer are being formulated.

Larval barramundi in the size range 2.8-5.2 mm were collected from plankton in two estuaries in north-eastern Queensland from 31 October 1979 until 13 February 1980. After leaving the plankton, barramundi moved into nearby brackish and freshwater swamps. These areas acted as nursery grounds, offering both protection from predators, and abundant prey in the form of insect larvae, other fish and crustaceans. These habitats exhibit a wide range of salinities (fresh water-44 × 103 mg l-1) and surface water temperatures (23-36�C). Juvenile barramundi commenced migration from these swamps into permanent tidal creeks around April where they remained for up to 9 months before dispersal into the estuary, up rivers or along coastal foreshores. The diet of the barramundi in these tidal creeks was exclusively fish and crustaceans. Juvenile barramundi were resident in tidal creeks that had been subjected to substantial human interference through habitat alteration. Destruction of nursery swamps may pose a serious threat to local barramundi stocks near centres of human population on the eastern Queensland coast.

Movements of juvenile barramundi resident in tidal creeks of two north-eastern Queensland coastal bays were determined using tag and recapture techniques. In a 3-year period from 1978, 1268 mainly young- of-the-year barramundi were tagged and 213 (17%) recaptured. Most fish were recaptured at the original tagging location, with only 32 (2.5% of all fish tagged) caught away from the tidal creeks where they were released. Marked fish continued to be recaptured within the tidal creeks until they were about 1 year old. Barramundi of this age moved out into the main estuary and dispersed into adjacent streams and coastal habitats. After leaving the tidal creeks, barramundi tagged in Trinity Bay moved an average distance of 7.6 km, whereas those tagged in Rockingham Bay moved an average of 23 km. Factors which may limit the movements of these juvenile fish are discussed.

In 2016, Barramundi, Lates calcaifer juveniles imported from Thailand to the aquaculture station at Sultan Qaboos University exhibited remarkable external clinical signs of losing scales, severe muscle necrosis, and ascites. Fin rot was also observed in the diseased fish. The mortality reached more than 90 % and it was assumed that certain bacterial species were associated with the diseased fish. The objective of the present study was to investigate the infection route of disease, revealing the causative agent and finding the most effective antibiotic treatment. The suspected pathogen vehicle was mosquito larvae in the outlet of the culture tank as bacterium was isolated inside the mosquito larvae. Primary, traditional phenotypic tests and the vitic test confirmed that the bacteria were pathogenic Aeromonas sobria and Lactococcus garvieae. Eight of the most commonly used antibiotics in the aquaculture industry was used for antibiotic susceptibility test. It showed that that Gentamycin was the most effective antibiotic while the most effective environmentally friendly source was henna, Lawsonia inermis, at a concentration of 10%.

In 2016, Barramundi, Lates calcaifer juveniles imported from Thailand to the aquaculture station at Sultan Qaboos University exhibited remarkable external clinical signs of losing scales, severe muscle necrosis, and ascites. Fin rot was also observed in the diseased fish. The mortality reached more than 90 % and it was assumed that certain bacterial species were associated with the diseased fish. The objective of the present study was to investigate the infection route of disease, revealing the causative agent and finding the most effective antibiotic treatment. The suspected pathogen vehicle was mosquito larvae in the outlet of the culture tank as bacterium was isolated inside the mosquito larvae. Primary, traditional phenotypic tests and the vitic test confirmed that the bacteria were pathogenic Aeromonas sobria and Lactococcus garvieae. Eight of the most commonly used antibiotics in the aquaculture industry was used for antibiotic susceptibility test. It showed that that Gentamycin was the most effective antibiotic while the most effective environmentally friendly source was henna, Lawsonia inermis, at a concentration of 10%.

AbstractBarramundi (Lates calcarifer) are a highly valued aquaculture species, and, as obligate carnivores, they have a demonstrated preference for dietary protein over lipid or starch to fuel energetic growth demands. In order to investigate how carnivorous fish regulate nutritional cues, we examined the metabolic effects of feeding two isoenergetic diets that contained different proportions of digestible protein or starch energy. Fish fed a high proportion of dietary starch energy had a higher proportion of liver SFA, but showed no change in plasma glucose levels, and few changes in the expression of genes regulating key hepatic metabolic pathways. Decreased activation of the mammalian target of rapamycin growth signalling cascade was consistent with decreased growth performance values. The fractional synthetic rate (lipogenesis), measured by TAG 2H-enrichment using 2H NMR, was significantly higher in barramundi fed with the starch diet compared with the protein diet (0·6 (se 0·1) v. 0·4 (se 0·1) % per d, respectively). Hepatic TAG-bound glycerol synthetic rates were much higher than other closely related fish such as sea bass, but were not significantly different (starch, 2·8 (se 0·3) v. protein, 3·4 (se 0·3) % per d), highlighting the role of glycerol as a metabolic intermediary and high TAG-FA cycling in barramundi. Overall, dietary starch significantly increased hepatic TAG through increased lipogenesis. Compared with other fish, barramundi possess a unique mechanism to metabolise dietary carbohydrates and this knowledge may define ways to improve performance of advanced formulated feeds.

Disease is a major impediment to world aquaculture, amplified by the increase of the intensity of aquaculture relieving pressure from over depleted wild stocks, but with intensity brings disease and particularly disease of the fragile gill organ, exposed directly to the water environment. There is little literature on barramundi biology and the various forms of culture impacting on health, particularly the gill and much research is required in gaining a further understanding of this popular eating fish. The light microscope is a pivotal tool with cytology and histology mandatory in assessing gill health. The gill biopsy should be considered part of a clinical examination as the water medium surrounding the gill and on the gill contains often fragile organisms that would otherwise be lost in fixation for histology alone, but easily viewed with cytology. Barramundi are easily anaesthetised and recovered like many terrestrials and gill re-growth is rapid, healing within days. Biopsies should be viewed unstained with and without phase contrast and then stained and reviewed, recognizing some ectoparasites maybe lost with anaesthetic agents and stains. The sacrificing of the fish after a live gill biopsy is necessary with histology and microbiology our major tools for diagnostics, with no other non invasive methods readily available as for terrestrials. Every year many new water organisms related to aquaculture are described in the literature and the finding of novel and new organisms makes the veterinary examination of the live fish exciting yet imperative. A major concern is the gill pathogens found in wild barramundi were similar to those found in culture. For example the prevalence of the parasite Henneguya a Myxosporidean was 90% in sea cages 60 km offshore from Darwin in the Bathurst Island river system and 66% for ponded fish with water drawn from the Darwin Elizabeth river, compared to 33% infected in the wild habitat of the Mary river system close to Darwin by road. However the bacterial disease Epitheliocystis had a prevalence of 66% in the sea cages and 18% of similarly sized fish in the Mary river system, yet nil found in the pond farm, but in this case sample numbers were restricted. Consequently the surveillance for new fish pathogens and monitoring for existing pathogens in the wild ecosystems and aquaculture facilities is necessary and must include the macro and micro flora and fauna surrounding such facilities as they are potentially affected from aquaculture waste streams. The sustainability of aquaculture in open water culture must be considered with great concern for many reasons, but disease by its nature could overwhelm a species and other aquatic life quickly disseminated in a dynamic water medium. Freshwater culture of barramundi has problems with off flavour and disease, particularly recirculating aquaculture systems due to undercapitalization and possibly at this stage with existing type farms not suited for the culture of barramundi with one farm having all fish sampled diagnosed with systemic bacteraemia and gill Epitheliocystis. Commonly fish sampled from freshwater culture had suffered pathological changes to the gill, particularly hyperplasia indicating the fish are continually affected by issues of water quality and disease. Pond culture appeared to control gill disease issues by affording lower stocking rates, high water exchanges from a river within metres, fallow and the flavour of the fish similar to wild catch or sea cage culture, when purged in brackish water. The decreased environmental and ecosystem risks, coupled with the pond farmer reporting good profits with a simple form of culture, also suitable for intensification is a success story for barramundi production for today and the future.

This study characterises various aspects of barramundi (Lates calcarifer) humoral immunity, including ontogeny, temperature modulation and kinetics following challenge with Streptococcus iniae. It was discovered that Staphylococcal protein A (SpA) was able to efficiently isolate antibody from serum, and that all barramundi Ig found in serum is tetrameric with a weight of approximately 800 kDa. This tetramer is composed of 8 heavy chains (72 kDa) and 8 light chains (28 kDa). Denaturing, non-reducing electrophoresis demonstrated differential disulfide polymerization (redox forms) of the tetrameric Ig which was consistent with those observed with other species. Polyclonal and monoclonal antibodies were produced against the protein A purified barramundi Ig, and various ELISA formats were developed. These serological tools were used to investigate aspects of barramundi humoral immunity. Examination of ontogeny of humoral immunity, revealed that barramundi possess minimal maternal antibody (<10 μg/ml wet weight) post-hatch, which is depleted rapidly (within 3 days). By day 8 systemic Ig is able to be detected, which continues to increase over the following months. However, it is not until seven week post-hatch that barramundi fingerlings are able to mount a prolonged immune response following vaccination with S. iniae. Environmental temperature was also found to significantly impact the ability of barramundi to respond to vaccination with S. iniae. Barramundi maintained at low temperatures (<230C) displayed a diminished, delayed and highly variable humoral immune response following vaccination, with many of the experimental animals failing to respond to primary vaccination. These responses could be mediated by either administering a booster vaccine or by elevating the environmental temperature. This study also demonstrated that there was a relationship with specific serum antibody and protection against S. iniae, with fish possessing high levels of specific Ig being protected from lethal challenge, while those with low titres being more susceptible to disease. Specific antibody in barramundi could be generated through natural exposure to the bacterium from the environment or through vaccination. Thus bath vaccination of fish (50,000) held at two facilities resulted in elevated systemic antibody levels and lower observed mortality, when compared to the unvaccinated control fish. Infections due to S. iniae were determined to be associated with elevated water temperatures. Laboratory trials and field data indicated that water temperatures between 24 and 280C resulted in the highest barramundi mortality. A weak association was also determined with low pH and mortality, with fish exposed to low pH’s (<6.0) being more susceptible to infection. No association was observed with mortality and salinity. Four monoclonal antibodies (Mab’s) were also generated against a 21 kDa protein from cell wall of S. iniae. The Mab’s displayed a high level of specificity for S. iniae, including those from Australia, Israel and America, and minimal cross-reactivity with other bacterial species tested. The Mab’s were used in an immunohistochemical study that confirmed the neurotropic nature of S. iniae infections, as well as demonstrating the presence of the bacterium in the intestine of infected fish.

This study characterises various aspects of barramundi (Lates calcarifer) humoral immunity, including ontogeny, temperature modulation and kinetics following challenge with Streptococcus iniae. It was discovered that Staphylococcal protein A (SpA) was able to efficiently isolate antibody from serum, and that all barramundi Ig found in serum is tetrameric with a weight of approximately 800 kDa. This tetramer is composed of 8 heavy chains (72 kDa) and 8 light chains (28 kDa). Denaturing, non-reducing electrophoresis demonstrated differential disulfide polymerization (redox forms) of the tetrameric Ig which was consistent with those observed with other species. Polyclonal and monoclonal antibodies were produced against the protein A purified barramundi Ig, and various ELISA formats were developed. These serological tools were used to investigate aspects of barramundi humoral immunity. Examination of ontogeny of humoral immunity, revealed that barramundi possess minimal maternal antibody (<10 μg/ml wet weight) post-hatch, which is depleted rapidly (within 3 days). By day 8 systemic Ig is able to be detected, which continues to increase over the following months. However, it is not until seven week post-hatch that barramundi fingerlings are able to mount a prolonged immune response following vaccination with S. iniae. Environmental temperature was also found to significantly impact the ability of barramundi to respond to vaccination with S. iniae. Barramundi maintained at low temperatures (<230C) displayed a diminished, delayed and highly variable humoral immune response following vaccination, with many of the experimental animals failing to respond to primary vaccination. These responses could be mediated by either administering a booster vaccine or by elevating the environmental temperature. This study also demonstrated that there was a relationship with specific serum antibody and protection against S. iniae, with fish possessing high levels of specific Ig being protected from lethal challenge, while those with low titres being more susceptible to disease. Specific antibody in barramundi could be generated through natural exposure to the bacterium from the environment or through vaccination. Thus bath vaccination of fish (50,000) held at two facilities resulted in elevated systemic antibody levels and lower observed mortality, when compared to the unvaccinated control fish. Infections due to S. iniae were determined to be associated with elevated water temperatures. Laboratory trials and field data indicated that water temperatures between 24 and 280C resulted in the highest barramundi mortality. A weak association was also determined with low pH and mortality, with fish exposed to low pH’s (<6.0) being more susceptible to infection. No association was observed with mortality and salinity. Four monoclonal antibodies (Mab’s) were also generated against a 21 kDa protein from cell wall of S. iniae. The Mab’s displayed a high level of specificity for S. iniae, including those from Australia, Israel and America, and minimal cross-reactivity with other bacterial species tested. The Mab’s were used in an immunohistochemical study that confirmed the neurotropic nature of S. iniae infections, as well as demonstrating the presence of the bacterium in the intestine of infected fish.

Other than the study by Griffiths (2009) on gill diseases, there has been no comprehensive study and report on the major diseases of Asian seabass (or barramundi) Lates calcarifer Bloch. It is a food fish species of growing importance in Asia and Australia. This study investigates some of the major diseases encountered in the various stages of the culture of L. calcarifer, at the histopathological, ultrastructural and molecular levels. Culture practices can have significant impacts on fish health. Disease outbreaks are influenced by factors involving the host, environment and pathogen. Current knowledge on diseases of L. calcarifer, and these factors which may influence disease outbreaks are discussed in Chapter 1. This is the first report of an intestinal Eimeria infection in L. calcarifer. The Eimeria infection was associated with severe pathology and significant mortality in the absence of other pathogens. It was detected in diseased L. calcarifer in all five nurseries in Ca Mau, Vietnam. Although these were small scale nurseries which stocked an average of 3000 to 5000 fish at any one time, a mortality rate of up to 30% was reported and is the cause of significant economic losses for these nurseries. Moderate to heavy Eimeria infestation were observed in greater than 80% of diseased fish examined. This high rate of Eimeria infestation is suspected to be linked to the low daily water exchange rates practised in these nurseries. However, the examination of only diseased fish does not allow the determination of prevalence. A systemic iridovirus infection was concurrently observed in some of the fishes but was not consistently present when compared to the Eimeria infection. Molecular analysis showed that the Eimeria of L. calcarifer from Vietnam formed clades with the Eimeria detected in L. calcarifer cultured in Australia, but clustered separately from other known Eimeria species. Although Cryptosporidium was detected in these L. calcarifer tissues, it could not be demonstrated histologically or ultrastructurally, suggesting a low grade infestation or perhaps an environmental contaminant in fish tissues tested. In situ hybridization using labeled PCR products showed that labeled DNA probes generated from 18S PCR products could not be used to distinguish between closely related genera such as Cryptosporidium and Eimeria. Future investigation to determine the origin, transmission and risk factors associated with this Eimeria infestation in L. calcarifer are needed. ‘Scale drop syndrome’ is a novel disease first reported in L. calcarifer in Penang, Malaysia in 1992. Cases with similar gross and clinical presentations were observed in Singapore in 2002, 2006 and 2009. Affected fish have loose scales, which dropped off easily when handled. The disease was initially observed in 100-300g fish, and later in larger fish up to 5kg bodyweight. Cumulative mortalities of 40 to 50% were reported by farms, posing significant economic losses of larger more valuable fish. This investigation forms the first pathological description of ‘scale drop syndrome’ (SDS) in L. calcarifer. To aid recognition of new cases for study, a case definition was developed for ‘scale drop syndrome’ in L. calcarifer as a systemic vasculitis associated with tissue necrosis in all major organs including the skin, with apparent targeting of cells of epithelial origin. Attempts to isolate or detect the causative agent(s) by cell culture, PCR and immunohistochemistry have proven unsuccessful. Further studies to elucidate the definitive aetiology, isolate the causal agent(s) and reproduce the disease will help better understanding and control of SDS. Although systemic iridoviral disease has been previously reported in many freshwater and marine fish species, this study forms the first report of this disease in L. calcarifer. Systemic iridoviral disease was observed in 5 to 20g L. calcarifer usually 2 to 3 weeks post-transfer into sea cages at two farms. Inclusion bodies suggestive of a systemic iridovirus infection were observed in clinically healthy L. calcarifer from the land-based nursery of one of these two farm; the presence of an iridovirus infection was supported by positive PCR results using Red Sea bream iridovirus (RSIV) primer 1. The presence of inclusions was not accompanied by any tissue necrosis in these clinically healthy fish. This finding suggested that the systemic iridovirus infection occurred before stocking at sea, and did not originate from wild fish or older fish in adjacent sea cages as initially suspected by this farm. Immunohistochemistry on tissues of clinical cases of systemic iridovirus gave positive results using the Red Sea bream iridovirus monoclonal antibody (RSIV M10), although intensity varied between tissues, possibly related to varying exposure of different tissues to fixation chemicals. Inclusion bodies in clinically healthy fish from the same farm did not show positive reaction with RSIV M10. This may be due to a lack of antigenic expression by the viral infected cells at this early stage of infection. Viral nervous necrosis (VNN) is a serious disease of hatchery reared L. calcarifer fry in this study. Mortalities of 50 to 100% were reported in 3wo fry. VNN can be difficult to diagnose in older fry, where it can be associated with few vacuolations or an absence of viral inclusions ‘Pot belly disease’ (PBD) was previously reported in L. calcarifer fry less than 1g, in association with an intracellular coccobacillus infection and mortalities of 80 to 100%. In this study, PBD was observed in 120g L. calcarifer at two sea cage farms, in association with significant granulomatous enteritis. The extent of the granulomatous enteritis is likely to have an effect on affected fish. It was observed concurrently with systemic iridoviral disease at one farm and nocardiosis at another farm. Diagnosis by histopathology and the lack of other confirmatory tests for PBD may result in underdiagnosis of this disease. The epidemiology of PBD needs further study to establish origin and modes of transmission, to facilitate better disease control. Diseases associated with infections by ubiquitous bacteria such as Vibrio, Tenacibaculum were commonly observed in L. calcarifer post-handling. Tenacibaculosis and vibriosis often occurred concurrently with other diseases such as streptococcosis, systemic iridviral disease or PBD. Streptococcosis can affect fish up to 3kg bodyweight, resulting in significant mortalities greater than 40 to 50%. Like SDS, because streptococcosis can affect up to market size fish, they can cause considerable economic losses. Although vaccines against Streptococcosis are available, conflicting views are held on the efficacy of Streptococcus vaccines by various research groups. Overall, the South-east Asian L. calcarifer farms which practiced vaccination against Streptococcus iniae reported a reduction of mortality, especially in fish greater than 1 to 1.5kg bodyweight. Nocardiosis has been reported as an emerging disease in marine food fish species caused by acid fast filamentous branching bacterium. Although nocardiosis was observed histopathologically in L. calcarifer at two sea cage farms, the numbers of samples examined were small and no other tests were attempted due to lack of suitable samples. More intensive and extensive study is needed to determine the significance of nocardiosis in L. calcarifer. Chronic granulomatous enteritis was not uncommon in the cases submitted to the Fish Health Laboratory in Perth. Although the peritonitis was associated with heavy bacteria infection, it is unclear if these are secondary invaders. Schipps, Bosmans & Humphreys (2009) reported that Vibrio harveyi and Photobacterium damsela damsela vaccinations appeared to be not efficacious, suggesting that these bacteria were not the primary cause of the disease. It is well recognized that disease outbreaks in farmed fish are influenced by the interaction between host, the environment and pathogens. While serious diseases are often reported in association with specific aquatic pathogens, not much is known about the risk factors which trigger fish disease outbreaks. Disease outbreaks often occur after stressful events such as net transfers, recent handling or poor water quality. In fact, diseases are often caused by ubiquitous pathogens that are commonly present in the culture environment. Although further research is necessary to gather more information to improve diagnosis and management of specific diseases, general health management strategies can be applied at the various stages in the culture of L. calcarifer to minimize disease outbreaks. This is discussed for L. calcarifer in Chapter 6. Observations of types of disease agents may be influenced by site conditions or the types of tests or materials examined. For example, some parasites may be more prevalent in certain sites where intermediate hosts abound, or loosely attached ectoparasites may be lost unless wet mount microscopic examinations of fresh tissues were carried out. The study of emerging diseases such as scale drop syndrome (SDS) or pot belly disease (PBD) in L. calcarifer has been hampered by lack of confirmatory diagnostic tools and inadequate knowledge on critical epidemiological factors such as mode of transmission or potential reservoirs. While ideally identification and isolation of the causal agent will help fulfil Koch’s postulates, it may be possible to improve the understanding of disease via cohabitation or infectivity trials using tissue homogenates from diseased fish when pure isolates are not available. There is a need to conduct research to not only establish a definitive aetiology, but also to identify risk factors to facilitate successful disease control. The successful management of disease in aquaculture does not lie in any one strategy but an integrated management of all risks encountered during the culture cycle against disease occurrence or incursions.

Barramundi (Lates calcarifer) is a centropomid teleost with a wide distribution across the Indo Pacific. In Australia, barramundi are native to the tropical zone from Exmouth Gulf in Western Australia, across the northern part of the continent, to the Mary River in Queensland. Barramundi are protandrous hermaphrodites, and are euryhaline, with a catadromous life history. Barramundi are a valuable Australian resource, with important commercial and recreational fisheries and aquaculture production to the value of $11 million dollars per year. Recent declines in the availability of the fish in some rivers has led to an interest in the possibility of restocking rivers with barramundi from other areas. Determining the genetic structure of barramundi populations in Australia is important for understanding biogeographic history, and appropriate management practices for both aquaculture and recreational and commercial fishing. Previous studies have concentrated on the east coast of Australia, and have largely ignored the western populations. In this study, I obtained DNA data from barramundi populations across the Australian range of the species, as well as populations from Papua New Guinea and Indonesia. The aims of this study were to use the genetic data to determine: 1. if populations in Western Australia show genetic differences between geographic regions 2. if these populations show an ancestral split from populations in the east of Australia and 3. the ancestral origins of Australian barramundi. Previous studies of DNA data from barramundi have discovered an east/west split occurring at the Torres Strait that was assumed to be caused by the closing of the strait during lowered sea levels. However, these studies suffered from a bias in sampling area, concentrating either on the eastern half of the range of barramundi, or on the western tip of the range. Data from these studies were combined and reanalyzed. Two major clades were discovered, with considerable biogeographic structuring, but their geographic locations did not coincide with the reported vicariance event at the Torres Strait. Instead,historical divisions among freshwater drainage systems appeared to have driven the evolutionary history of barramundi in Australia. In order to investigate these historical divisions further, a 290 bp section of the mitochondrial DNA control region was sequenced in 284 barramundi from seven populations across the Australian geographic range of the species and from one population in Papua New Guinea and one population in Indonesia. Analyses of molecular variance within and among populations showed significant geographic structuring, based on biogeographical provinces and drainage divisions. Nested clade analyses indicated that these geographical associations were the result of restricted gene flow, range expansion, and past fragmentation events. I hypothesise that the Ord River area in the west of the continent was the ancestral source population for the rest of the species' range across Australia, with Indonesia being the most likely origin of this source. Populations of barramundi from the Pilbara region are genetically distinct and geographically isolated, with strong evidence of an ancestral divide along geographical barriers to dispersal. There is a strong association between Papua New Guinea and Australia, although further investigations using the cytochrome b region of mitochondrial DNA indicated a more ancestral divide between the two than is currently evident, which could reflect an ancient geographical divide between the two, or could be evidence of a secondary migration route to Australia. For a more detailed study of evolutionary processes acting on populations of barramundi in Western Australia, allelic diversity was examined at five microsatellite loci. All loci were polymorphic and genotypic frequencies conformed to Hardy-Weinberg expectations, with no significant linkage between loci evident in any population. Measures of within population diversity were significantly related to latitude, suggesting southerly migration from a northern source population. The Ord River was the most genetically diverse population, and the most likely ancestral migration source to the area, with diversity decreasing down the west coast. Although there were significant differences among populations, the nuclear microsatellite data do not indicate the same degree of genetic structuring as is evident in the mitochondrial data. This may be a consequence of rapid evolutionary change at microsatellite loci, with past separations or population differences masked by recombination and back mutation of the microsatellite alleles. However, the nature of nuclear and mitochondrial inheritance may also indicate life history differences between the sexes, where significant genetic contribution to gene flow by males and limited female gene flow may lead to preservation of maternally inherited population substructure. The principal findings from this study are: * There is no genetic evidence for an east/west division of barramundi populations in Australia, as suggested by previous research. * Despite barramundi's catadromous life history, and ability to disperse through marine waters, the present genetic structure indicates a division principally among river drainages. From a population genetic viewpoint, the species can be regarded as freshwater, rather than marine. * The most likely origin of barramundi in Australia is the Ord River region, with Indonesia as the route of migration. * Differences in the population structure demonstrated by nuclear and mitochondrial data indicate possible life history differences between the sexes. * Barramundi populations in different biogeographical provinces may have been substantially isolated over a long period of time, and may therefore represent independently evolving populations. This has important implications for fishery management and translocation issues for restocking rivers.

Barramundi (Lates calcarifer) is a centropomid teleost with a wide distribution across the Indo Pacific. In Australia, barramundi are native to the tropical zone from Exmouth Gulf in Western Australia, across the northern part of the continent, to the Mary River in Queensland. Barramundi are protandrous hermaphrodites, and are euryhaline, with a catadromous life history. Barramundi are a valuable Australian resource, with important commercial and recreational fisheries and aquaculture production to the value of $11 million dollars per year. Recent declines in the availability of the fish in some rivers has led to an interest in the possibility of restocking rivers with barramundi from other areas. Determining the genetic structure of barramundi populations in Australia is important for understanding biogeographic history, and appropriate management practices for both aquaculture and recreational and commercial fishing. Previous studies have concentrated on the east coast of Australia, and have largely ignored the western populations. In this study, I obtained DNA data from barramundi populations across the Australian range of the species, as well as populations from Papua New Guinea and Indonesia. The aims of this study were to use the genetic data to determine: 1. if populations in Western Australia show genetic differences between geographic regions 2. if these populations show an ancestral split from populations in the east of Australia and 3. the ancestral origins of Australian barramundi. Previous studies of DNA data from barramundi have discovered an east/west split occurring at the Torres Strait that was assumed to be caused by the closing of the strait during lowered sea levels. However, these studies suffered from a bias in sampling area, concentrating either on the eastern half of the range of barramundi, or on the western tip of the range. Data from these studies were combined and reanalyzed. Two major clades were discovered, with considerable biogeographic structuring, but their geographic locations did not coincide with the reported vicariance event at the Torres Strait. Instead,historical divisions among freshwater drainage systems appeared to have driven the evolutionary history of barramundi in Australia. In order to investigate these historical divisions further, a 290 bp section of the mitochondrial DNA control region was sequenced in 284 barramundi from seven populations across the Australian geographic range of the species and from one population in Papua New Guinea and one population in Indonesia. Analyses of molecular variance within and among populations showed significant geographic structuring, based on biogeographical provinces and drainage divisions. Nested clade analyses indicated that these geographical associations were the result of restricted gene flow, range expansion, and past fragmentation events. I hypothesise that the Ord River area in the west of the continent was the ancestral source population for the rest of the species' range across Australia, with Indonesia being the most likely origin of this source. Populations of barramundi from the Pilbara region are genetically distinct and geographically isolated, with strong evidence of an ancestral divide along geographical barriers to dispersal. There is a strong association between Papua New Guinea and Australia, although further investigations using the cytochrome b region of mitochondrial DNA indicated a more ancestral divide between the two than is currently evident, which could reflect an ancient geographical divide between the two, or could be evidence of a secondary migration route to Australia. For a more detailed study of evolutionary processes acting on populations of barramundi in Western Australia, allelic diversity was examined at five microsatellite loci. All loci were polymorphic and genotypic frequencies conformed to Hardy-Weinberg expectations, with no significant linkage between loci evident in any population. Measures of within population diversity were significantly related to latitude, suggesting southerly migration from a northern source population. The Ord River was the most genetically diverse population, and the most likely ancestral migration source to the area, with diversity decreasing down the west coast. Although there were significant differences among populations, the nuclear microsatellite data do not indicate the same degree of genetic structuring as is evident in the mitochondrial data. This may be a consequence of rapid evolutionary change at microsatellite loci, with past separations or population differences masked by recombination and back mutation of the microsatellite alleles. However, the nature of nuclear and mitochondrial inheritance may also indicate life history differences between the sexes, where significant genetic contribution to gene flow by males and limited female gene flow may lead to preservation of maternally inherited population substructure. The principal findings from this study are: * There is no genetic evidence for an east/west division of barramundi populations in Australia, as suggested by previous research. * Despite barramundi's catadromous life history, and ability to disperse through marine waters, the present genetic structure indicates a division principally among river drainages. From a population genetic viewpoint, the species can be regarded as freshwater, rather than marine. * The most likely origin of barramundi in Australia is the Ord River region, with Indonesia as the route of migration. * Differences in the population structure demonstrated by nuclear and mitochondrial data indicate possible life history differences between the sexes. * Barramundi populations in different biogeographical provinces may have been substantially isolated over a long period of time, and may therefore represent independently evolving populations. This has important implications for fishery management and translocation issues for restocking rivers.

Barramundi (Lates calcarifer) is a centropomid teleost with a wide distribution across the Indo Pacific. In Australia, barramundi are native to the tropical zone from Exmouth Gulf in Western Australia, across the northern part of the continent, to the Mary River in Queensland. Barramundi are protandrous hermaphrodites, and are euryhaline, with a catadromous life history. Barramundi are a valuable Australian resource, with important commercial and recreational fisheries and aquaculture production to the value of $11 million dollars per year. Recent declines in the availability of the fish in some rivers has led to an interest in the possibility of restocking rivers with barramundi from other areas. Determining the genetic structure of barramundi populations in Australia is important for understanding biogeographic history, and appropriate management practices for both aquaculture and recreational and commercial fishing. Previous studies have concentrated on the east coast of Australia, and have largely ignored the western populations. In this study, I obtained DNA data from barramundi populations across the Australian range of the species, as well as populations from Papua New Guinea and Indonesia. The aims of this study were to use the genetic data to determine: 1. if populations in Western Australia show genetic differences between geographic regions 2. if these populations show an ancestral split from populations in the east of Australia and 3. the ancestral origins of Australian barramundi. Previous studies of DNA data from barramundi have discovered an east/west split occurring at the Torres Strait that was assumed to be caused by the closing of the strait during lowered sea levels. However, these studies suffered from a bias in sampling area, concentrating either on the eastern half of the range of barramundi, or on the western tip of the range. Data from these studies were combined and reanalyzed. Two major clades were discovered, with considerable biogeographic structuring, but their geographic locations did not coincide with the reported vicariance event at the Torres Strait. Instead, historical divisions among freshwater drainage systems appeared to have driven the evolutionary history of barramundi in Australia. In order to investigate these historical divisions further, a 290 bp section of the mitochondrial DNA control region was sequenced in 284 barramundi from seven populations across the Australian geographic range of the species and from one population in Papua New Guinea and one population in Indonesia. Analyses of molecular variance within and among populations showed significant geographic structuring, based on biogeographical provinces and drainage divisions. Nested clade analyses indicated that these geographical associations were the result of restricted gene flow, range expansion, and past fragmentation events. I hypothesise that the Ord River area in the west of the continent was the ancestral source population for the rest of the species’ range across Australia, with Indonesia being the most likely origin of this source. Populations of barramundi from the Pilbara region are genetically distinct and geographically isolated, with strong evidence of an ancestral divide along geographical barriers to dispersal. There is a strong association between Papua New Guinea and Australia, although further investigations using the cytochrome b region of mitochondrial DNA indicated a more ancestral divide between the two than is currently evident, which could reflect an ancient geographical divide between the two, or could be evidence of a secondary migration route to Australia. For a more detailed study of evolutionary processes acting on populations of barramundi in Western Australia, allelic diversity was examined at five microsatellite loci. All loci were polymorphic and genotypic frequencies conformed to Hardy-Weinberg expectations, with no significant linkage between loci evident in any population. Measures of within population diversity were significantly related to latitude, suggesting southerly migration from a northern source population. The Ord River was the most genetically diverse population, and the most likely ancestral migration source to the area, with diversity decreasing down the west coast. Although there were significant differences among populations, the nuclear microsatellite data do not indicate the same degree of genetic structuring as is evident in the mitochondrial data. This may be a consequence of rapid evolutionary change at microsatellite loci, with past separations or population differences masked by recombination and back mutation of the microsatellite alleles. However, the nature of nuclear and mitochondrial inheritance may also indicate life history differences between the sexes, where significant genetic contribution to gene flow by males and limited female gene flow may lead to preservation of maternally inherited population substructure. The principal findings from this study are: • There is no genetic evidence for an east/west division of barramundi populations in Australia, as suggested by previous research. • Despite barramundi’s catadromous life history, and ability to disperse through marine waters, the present genetic structure indicates a division principally among river drainages. From a population genetic viewpoint, the species can be regarded as freshwater, rather than marine. • The most likely origin of barramundi in Australia is the Ord River region, with Indonesia as the route of migration. • Differences in the population structure demonstrated by nuclear and mitochondrial data indicate possible life history differences between the sexes. • Barramundi populations in different biogeographical provinces may have been substantially isolated over a long period of time, and may therefore represent independently evolving populations. This has important implications for fishery management and translocation issues for restocking rivers.

The research investigated the effectiveness of proteins from tuna hydrolysate (TH) and poultry by product meal (PBM), as fishmeal (FM) protein replacements. The results demonstrated that replacement of 10% FM with TH improved growth, immunity, intestinal health and disease resistance in juvenile barramundi. The addition of 10% TH in bioprocessed PBM not only improved the physiology of the fish but also increased the fish growth when 100% fishmeal protein was replaced by PBM protein.

The effects of pre-freezing treatments such as time-temperature abuse, use of ice, freeze–thaw cycles, use of polyphosphate and post freezing treatments such as glazing and packaging were assessed on the microbiological and physiochemical properties of barramundi (Lates calcarifer) fillets. The results indicated that the use of sodium tripolyphosphate, constant temperature and use of ice in the form of slurry can improve the shelf life of barramundi fillets.

The Barramundi (Lates calcarifer Bloch) is a large, percoid fish, highly valued as a commercial and recreational species. In Queensland, it is distributed in estuaries, coastal habitats and freshwater areas accessible to the sea north from about the Noosa River. This study reports on a three year investigation of the movements, reproduction and growth of barramundi at 15 sites along the east Queensland coast. Of the 524 adult and sub-adult barramundi tagged in coastal areas and estuaries of eastern Queensland between 1981 and 1984, 136 (26%) were recaptured. Most recaptures (75%) occurred within a year of the fish being tagged and 32% were recaptured within three months of release. Movements of tagged fish were usually less than five kilometres, with 25 km regarded as rare. While most fish were recaptured at or near the location where they were released (usually an estuary), in the Burdekin delta area there were movements along coastal foreshores and into adjacent streams. Unlike other parts of Australia and Papua New Guinea, barramundi in eastern Queensland are generally not catadromous. The large proportion of short and ephemeral rivers and an increasing number of barriers across the larger river systems have restricted the freshwater habitat available for barramundi. In eastern Queensland, peak spawning occurs from November to February although some spawnings do occur as early as September and as late as April. Gametogenesis commences in August/September and is apparently initiated by a seasonal increase in water temperature and photoperiod. Only weak evidence was found supporting multiple spawning and only one modal size class of developing eggs was generally present in ovaries. Fecundity was high and was found to be exponentially related to length. Barramundi mature as males and later, between about 900 and 1000 mm total length, change sex to females. Length-weight relationships, for both sexes, in all areas were strongly linear. In most areas there were significant differences between male and female length-weight regressions. For each area, estimates of the von Bertalanffy growth parameters K, L00 and t 0 ranged from 0.23 to 0.25, 1189 mm to 1274 mm and -0.44 to -0.49 years respectively. Growth rates were initially faster than those established for barramundi in the Northern Territory, Gulf of Carpentaria and Papua New Guinea, and this as considered to be a possible response to heavy exploitation or environmental conditions.

<i>Abstract</i> .—Central Queensland in Australia already has a highly variable rainfall and streamflow pattern. River flows of the largest local river, the Fitzroy, are seasonal and ephemeral and, between 1976 and 2008, varied in magnitude from around 349,677 to 22,903,390 ML per annum. Predictions of local climate change effects suggest that rainfall and streamflows will become more variable with less frequent but larger flood events and extended, more severe drought periods. SUNTAG is a program that has recorded details of tagged and recaptured fish in Queensland since 1986. CAPREEF is a community-based program that has collected catch-and-effort data from recreational fishers across Central Queensland since 2005. The SUNTAG and CAPREEF programs act as a long-term central repository to collect recreational fish tagging and catch information. The goal of this paper was to examine two models predicting changes associated with rainfall and streamflow, the first examining changes in barramundi <i>Lates calcarifer </i> recruitment in a wetland system and the second predicting changes in recreational catch rate of sand whiting <i>Sillago ciliata </i> and red throat emperor <i>Lethrinus miniatus</i> . Catch rates of young barramundi recruiting to a wetland in the Fitzroy River delta between 1985 and 2008 varied between 0 and 37 fish/d. The median catch rates of fishing clubs also varied widely, being highest in years following wet season flooding.

<em>Abstract</em>.—Mangrove habitats are among the most threatened coastal habitats. Loss and degradation of mangroves have broad impacts because mangroves are important in prevention of coastal erosion, are excellent at carbon sequestration, and are critical habitats for many marine and estuarine fishes, including coral reef species. However, these species often lack the economic importance or charismatic characteristics to leverage conservation of mangrove habitats. Recent and ongoing research is demonstrating the importance of mangrove habitats to economically important recreational fish species that, in conjunction with reports on the economic impact of these fisheries, provides leverage for mangrove conservation. Two recreational fish species—Common Snook <em>Centropomus undecimalis </em>and Tarpon <em>Megalops atlanticus</em>—depend on mangrove habitats for one or more of their life stages. Two other species— Bonefish <em>Albula vulpes </em>and Barramundi <em>Lates calcarifer</em>—are concurrent with mangroves. Each species supports fisheries with annual economic impacts of hundreds of millions of dollars and a large constituency of users. The combination of biological and economic research on these and other recreational fish species can be used as tools for mangrove conservation, adding a much needed boost to coastal conservation efforts and providing protection to many ecologically important but less charismatic species.

<em>Abstract</em>.—Mangrove habitats are among the most threatened coastal habitats. Loss and degradation of mangroves have broad impacts because mangroves are important in prevention of coastal erosion, are excellent at carbon sequestration, and are critical habitats for many marine and estuarine fishes, including coral reef species. However, these species often lack the economic importance or charismatic characteristics to leverage conservation of mangrove habitats. Recent and ongoing research is demonstrating the importance of mangrove habitats to economically important recreational fish species that, in conjunction with reports on the economic impact of these fisheries, provides leverage for mangrove conservation. Two recreational fish species—Common Snook <em>Centropomus undecimalis </em>and Tarpon <em>Megalops atlanticus</em>—depend on mangrove habitats for one or more of their life stages. Two other species— Bonefish <em>Albula vulpes </em>and Barramundi <em>Lates calcarifer</em>—are concurrent with mangroves. Each species supports fisheries with annual economic impacts of hundreds of millions of dollars and a large constituency of users. The combination of biological and economic research on these and other recreational fish species can be used as tools for mangrove conservation, adding a much needed boost to coastal conservation efforts and providing protection to many ecologically important but less charismatic species.

<em>Abstract</em>.-The general acceptance that individual fisheries should be managed in the context of the ecosystem of which the target species are a part has led to the paradigm of ecosystem- based fisheries management (EBFM). Such management may be particularly suitable for diadromous fishes, which spend time in rivers, estuaries, and the sea, because their sustainability would benefit from a holistic approach. The extent to which this is possible and has been successful depends on a wide variety of biological, socioeconomic, and political factors. Fishing in all its forms is only one of a broad array of human activities in rivers, estuaries, and the coastal zone; hence, diadromous fisheries management requires not only integration across ecosystems, but also its inclusion in overall planning processes. Tropical diadromous fisheries in developing countries suffer from overfishing, lack of adequate human resources to manage the fisheries, insufficient scientific data for sound management and decision making, lack of monitoring capabilities, poor enforcement of laws, inefficient administration, and increasing conflicts between different types of users. Even in developed countries, many of these issues also have not been addressed. The extent to which an EBFM approach has been successful for tropical diadromous species is discussed using the various barramundi <em>Lates calcarifer</em>, mullet (Mugilidae), and tropical shad (<em>Tenualosa</em>) fisheries of Asia and Australia, taking into account issues of food security and the role of community-based management.