Measuring the impacts of aquatic animal diseases: the role of economic analysis.

Aquaculture is an important industry both economically and socially. The majority of this industry is focused on the production of aquatic animals, which may be substantially adversely affected by disease. Economic analyses may be used to inform decision-makers on the aquatic animal disease control choices that are economically optimal. Examples of such analyses are presented in this paper, ranging from basic cost estimates of disease impact to complex, spatial- temporal, bio-economic models. Regardless of the complexity of the analysis, there is a consistent need to collect and analyse good quality data measuring both the production and health of aquatic animals. This would require a variety of individuals and groups, including farmers, scientists and the government, to collaboratively contribute to this end. Given the necessary data, more sophisticated models may be better used to inform decision-making from the farm to the national level. Finally, economic analyses should not be limited to simple aggregated cost and benefit results but rather should include the social and gender impacts of financial decisions, as well as the potential externalities both within and among the various impacted sectors in order to optimise investment at both the farm and national levels.

Le secteur de l'aquaculture joue un rôle important aux plans tant économique que social. La majorité des filières du secteur sont axées sur la production d'animaux aquatiques, espèces susceptibles à des maladies à l'impact souvent considérable. Les décideurs ont la possibilité de recourir à des analyses économiques afin de sélectionner les stratégies de lutte contre les maladies des animaux aquatiques optimales au plan économique. L'auteur présente quelques exemples de ce type d'analyses, qui vont de l'estimation basique des coûts liés à l'impact d'une maladie à des modèles analytiques complexes, spatiotemporels et bioéconomiques. Indépendamment de la complexité de l'analyse, il est à chaque fois indispensable de collecter et d'analyser des données de bonne qualité concernant la production et la santé des animaux aquatiques. La réussite d'une telle entreprise nécessite la contribution d'un large éventail d'acteurs individuels et collectifs travaillant en collaboration, dont les éleveurs, les chercheurs et les instances gouvernementales. Dès lors que l'on dispose des données nécessaires, des modèles plus sophistiqués pourront être utilisés afin d'étayer les prises de décision depuis les élevages jusqu'au niveau national. Enfin, les analyses économiques ne devraient pas se limiter à de simples résultats agrégés des coûts et des bénéfices mais devraient prendre en compte les impacts sociaux des décisions financières et leurs répercussions sexospécifiques, ainsi que les effets externes potentiels sur et parmi les divers secteurs affectés, dans le but d'optimiser les investissements réalisés aussi bien au niveau des élevages qu'à l'échelle nationale.

La acuicultura es una actividad industrial importante, a la vez económica y socialmente. El grueso del sector está dedicado a la producción de animales acuáticos, en los que pueden hacer estragos las enfermedades. Los análisis económicos pueden ser utilizados por las instancias decisorias para decidir con conocimiento de causa acerca de las líneas de actuación económicamente idóneas para combatir las enfermedades de dichos animales. El autor presenta ejemplos de este tipo de análisis, que van desde estimaciones básicas del costo de las consecuencias de una enfermedad hasta complejos modelos bioeconómicos que integran la dimensión espaciotemporal. Ahora bien, sea cual sea el nivel de complejidad del análisis, siempre es necesario reunir y analizar datos de buena calidad que midan tanto la producción como el estado de salud de los animales acuáticos. Para hacer posible tal objetivo sería menester que diversas personas y colectividades, entre ellas productores, científicos y administraciones públicas, trabajaran de consuno con este fin. Habida cuenta de los datos necesarios, es posible dar un mejor uso a modelos más sofisticados para fundamentar los procesos decisorios a todos los niveles, desde la explotación hasta el ámbito nacional. Los resultados de los análisis económicos, por último, lejos de ofrecer meras sumas de costos y beneficios, deberían también dar cuenta de los efectos sociales o ligados al género de las decisiones de índole económica, así como de eventuales influencias externas que se dejen sentir en los diversos sectores afectados, o que se ejerzan de uno a otro de esos sectores, con el fin de optimizar las inversiones tanto en cada explotación como a escala nacional.

Kudoa sp. (Myxozoa, Multivalvulida): first report in five commercial fish species from the Canary Islands-FAO 34 (Macaronesia-Spain).

Kudoid myxozoans have been reported causing serious chronic problems in marine fisheries, by reducing the market value of infected fish through pathological damage to the host musculature. We report here the overall prevalence of a Kudoa species in 84/277 (30.3%) fishes from 20 different species of high commercial value captured between October 2011 and December 2013 from the United Nations Food and Agriculture Organization (FAO) 34 commercial fishing area, near the coast of the Canary Islands (Spain). Macroscopic examination showed myxozoan-like cysts in skeletal muscle from 5 of the 20 fish species examined, with the following prevalences: Pagellus acarne (86.7%), Pagellus erythrinus (46.5%), Serranus cabrilla (27.8%), Spondyliosoma cantharus (19.4%), and Sarpa salpa (28.6%). Infection intensity was determined based on spore counts following muscle tissue digestion. Morphometric studies to characterize the species and DNA sequence analysis results suggest that these infections are attributable to a Kudoa species closely related to Kudoa trachuri. This paper reports the first study on a multivalvulidan species to be identified from the Canary Islands. Furthermore, this is the first report of Kudoa parasites in all of the hosts mentioned above, with the exception of P. acarne.

Occurrence of Anisakis pegreffii (Nematoda: Anisakidae) Larvae in Imported John Dory (Zeus faber) from Senegalese Coast Sold in Turkish Supermarkets.

BACKGROUND: West African goatfish Pseudupeneus prayensis, bluespotted seabream Pagrus caeruleostictus and John Dory Zeus faber are commercially marketed as fresh and frequently imported from Senegalese coast (FAO area 34.3.12) in Turkish supermarkets. PURPOSE: The aim of the current study was to collect data of occurrence and molecular identification of Anisakis species in imported P. prayensis, P. caeruleostictus and Z. faber caught in the Senegalese coast and to support epidemiological report for a risk evaluation of Anisakis species in Turkish supermarkets. METHODS: Forty imported fish from each species at a total of 120 samples were investigated for the presence of Anisakis larvae. Based on ITS region of RFLP analysis Anisakis larvae were identified and randomly selected five larvae were also sequenced for further confirmation for cox2 gene. RESULTS: No Anisakis larvae were isolated from P. prayensis, P. caeruleostictus whereas Anisakis larvae were only found in Z. faber. A total of 156 Anisakis larvae were collected from Z. faber. All larvae were molecularly identified as Anisakis pegreffii. The prevalence (%), intensity and abundance of Anisakis infection in Z. faber were detected to be 82.5%, 8.3 and 6.8, respectively. CONCLUSION: This is the first assessment of the occurrence of A. pegreffii in imported Z. faber from the Senegalese coast in Turkish supermarkets. Moreover, consuming imported P. prayensis and P. caeruleostictus present low to non-existent risk for anisakiasis in Turkish consumers. Furthermore, the presence of A. pegreffii larvae in imported Z. faber from the Senegal waters could have public health implications in Turkish consumers.

Economic appraisal of vaccination against Streptoccocus agalactiae in Nile tilapia farms in Brazil.

Infection with Streptococcus agalactiae causes mortality and major economic losses in Nile tilapia (Oreochromis niloticus) farming worldwide. In Brazil, serotype strains Ia, Ib and III have been isolated in streptococcosis outbreaks, but serotype Ib is the most prevalent. Vaccination is considered an effective method to prevent economically-important diseases in aquaculture and has been associated with decreased use of antibiotics and improvements in fish survival. We developed a flexible partial-budget model to undertake an economic appraisal of vaccination against Streptococcus agalactiae in Nile tilapia farmed in net cages in large reservoirs. The model considers the benefits and costs that are likely to be associated with vaccination at the farm-level, in one production cycle. We built three epidemiological scenarios of cumulative mortality attributable to S. agalactiae (5%, 10%, and 20%, per production cycle) in a non-vaccinated farm. For each scenario, we applied a stochastic model to simulate the net return of vaccination, given a combination of values of "vaccine efficacy", "gain in feed conversion ratio", "feed price", "fish market price ", and "cost of vaccine dose". In the 20% cumulative mortality scenario, the net return would break-even (benefits ≥ costs) in at least 97.9% of interactions. Should cumulative mortality be lower than 10%, the profitability of vaccination would be more dependent on better feed conversion ratio. The inputs "feed price" and "cost of vaccine" had minor effects on the output, in all pre-vaccination mortality scenarios. Although our simulations are based on conservative values and consider uncertainty about the modeled parameters, we conclude that vaccination against S. agalactiae is likely to be profitable in Nile tilapia farms, under similar production conditions.

Derivation of the economic value of R0 for macroparasitic diseases and application to sea lice in salmon.

BACKGROUND: Macroparasites, such as ticks, lice, and helminths, are a concern in livestock and aquaculture production, and can be controlled by genetic improvement of the host population. Genetic improvement should aim at reducing the rate at which parasites spread across the farmed population. This rate is determined by the basic reproduction ratio, i.e. [Formula: see text], which is the appropriate breeding goal trait. This study aims at providing a method to derive the economic value of [Formula: see text]. METHODS: Costs of a disease are the sum of production losses and expenditures on disease control. Genetic improvement of [Formula: see text] lowers the loss-expenditure frontier. Its economic effect depends on whether the management strategy is optimized or not. The economic value may be derived either from the reduction in losses with constant expenditures or from the reduction in expenditures with constant losses. RESULTS: When [Formula: see text] ≤ 1, the economic value of a further reduction is zero because there is no risk of a major epidemic. When [Formula: see text] > 1 and management is optimized, the economic value increases with decreasing values of [Formula: see text], because both the mean number of parasites per host and frequency of treatments decrease at an increasing rate when [Formula: see text] decreases. When [Formula: see text] > 1 and management is not optimized, the economic value depends on whether genetic improvement is used for reducing expenditures or losses. For sea lice in salmon, the economic value depends on a reduction in expenditures with constant losses, and is estimated to be 0.065€/unit [Formula: see text]/kg production. DISCUSSION: Response to selection for measures of disease prevalence cannot be predicted from quantitative genetic theory alone. Moreover, many studies fail to address the issue of whether genetic improvement results in reduced losses or expenditures. Using [Formula: see text] as the breeding goal trait, weighed by its appropriate economic value, avoids these issues. CONCLUSION: When management is optimized, the economic value increases with decreasing values of [Formula: see text] (until the threshold of [Formula: see text], where it drops to zero). When management is not optimized, the economic value depends on whether genetic improvement is used for reduced expenditures or production losses. For sea lice in salmon, the economic value is estimated to be 0.065 €/unit [Formula: see text]/kg production.

Social and economic aspects of aquatic animal health.

Aquaculture is an increasingly important source of animal protein for a growing global population. Disease is a major constraint to production, with resultant socio-economic impacts for individuals, communities and economies which rely on aquaculture. Aquatic animal health is also strongly influenced by human factors, ranging from international trade regulations to the behaviours of individuals working in aquaculture. This article summarises the human factors associated with aquaculture production using international examples for illustration.

L'aquaculture est une source de protéines animales de plus en plus importante compte tenu des besoins d'une population mondiale toujours plus nombreuse. Les maladies sont un obstacle majeur pour la production du secteur, avec des effets socio-économiques importants pour les individus, les communautés et les économies dépendant de l'aquaculture. La santé des animaux aquatiques subit également l'influence de facteurs anthropiques, depuis les réglementations applicables au commerce international jusqu'au comportement des personnels des fermes aquacoles. Cet article résume les facteurs anthropiques associés à l'aquaculture, à partir d'exemples observés dans divers endroits du monde.

La acuicultura constituye una fuente de proteínas animales de creciente importancia para una población mundial que aumenta sin cesar. Las enfermedades, que son el principal factor limitante que pesa sobre la producción, tienen también efectos socioeconómicos para las personas, comunidades y economías que dependen de la acuicultura. La sanidad de los animales acuáticos se ve igualmente muy influida por una panoplia de factores humanos, que van desde los reglamentos de comercio internacional hasta el proceder del personal de las instalaciones acuícolas. Sirviéndose de ejemplos tomados de diferentes países, los autores resumen los factores humanos que influyen en la producción acuícola.

Identification of Infectious Salmon Anaemia Virus from Imported Iced Atlantic Salmons.

Infectious Salmon anaemia virus (ISAV) has become a threat to the salmon industry worldwide and has caused considerable economic loss. In the present study, 9 suspect cases of ISAV infection were identified from iced Atlantic salmons imported from Norway in 2014 through Shenzhen port (Shenzhen, China) using methods recommended by the World Organization for Animal Health. However, the results of virus isolation were negative., Based on the sequence analysis of ISAV segment 6, the 9 ISAV isolates belonged to the HPRO type, had high homology (98.3%~100.0%) and closest relationship with Norway strains. We identified the 9 positive HPRO ISAVs from 491 iced Atlantic salmons (1. 8%). Therefore, we should strengthen the quarantine of iced Atlantic salmons from Norway in case of HPRO ISAV into China.

The epidemiological and economic effects from systematic depopulation of Norwegian marine salmon farms infected with pancreas disease virus.

Pancreas disease (PD) is a viral disease associated with significant economic losses in Scottish, Irish, and Norwegian marine salmon aquaculture. In this paper, we investigate how disease-triggered harvest strategies (systematic depopulation of infected marine salmon farms) towards PD can affect disease dynamics and salmon producer profits in an endemic area in the southwestern part of Norway. Four different types of disease-triggered harvest strategies were evaluated over a four-year period (2011-2014), each scenario with different disease-screening procedures, timing for initiating the harvest interventions on infected cohorts, and levels of farmer compliance to the strategy. Our approach applies a spatio-temporal stochastic model for simulating the spread of PD in the separate scenarios. Results from these simulations were then used in cost-benefit analyses to estimate the net benefits of different harvest strategies over time. We find that the most aggressive strategy, in which infected farms are harvested without delay, was most efficient in terms of reducing infection pressure in the area and providing economic benefits for the studied group of salmon producers. On the other hand, lower farm compliance leads to higher infection pressure and less economic benefits. Model results further highlight trade-offs in strategies between those that primarily benefit individual producers and those that have collective benefits, suggesting a need for institutional mechanisms that address these potential tensions.

The economic benefits of disease triggered early harvest: A case study of pancreas disease in farmed Atlantic salmon from Norway.

Pancreas disease (PD) is an important viral disease in Norwegian, Scottish and Irish aquaculture causing biological losses in terms of reduced growth, mortality, increased feed conversion ratio, and carcass downgrading. We developed a bio-economic model to investigate the economic benefits of a disease triggered early harvesting strategy to control PD losses. In this strategy, the salmon farm adopts a PCR (Polymerase Chain Reaction) diagnostic screening program to monitor the virus levels in stocks. Virus levels are used to forecast a clinical outbreak of pancreas disease, which then initiates a prescheduled harvest of the stock to avoid disease losses. The model is based on data inputs from national statistics, literature, company data, and an expert panel, and use stochastic simulations to account for the variation and/or uncertainty associated with disease effects and selected production expenditures. With the model, we compared the impacts of a salmon farm undergoing prescheduled harvest versus the salmon farm going through a PD outbreak. We also estimated the direct costs of a PD outbreak as the sum of biological losses, treatment costs, prevention costs, and other additional costs, less the costs of insurance pay-outs. Simulation results suggests that the economic benefit from a prescheduled harvest is positive once the average salmon weight at the farm has reached 3.2kg or more for an average Norwegian salmon farm stocked with 1,000,000smolts and using average salmon sales prices for 2013. The direct costs from a PD outbreak occurring nine months (average salmon weight 1.91kg) after sea transfer and using 2013 sales prices was on average estimated at NOK 55.4 million (5%, 50% and 90% percentile: 38.0, 55.8 and 72.4) (NOK=€0.128 in 2013). Sensitivity analyses revealed that the losses from a PD outbreak are sensitive to feed- and salmon sales prices, and that high 2013 sales prices contributed to substantial losses associated with a PD outbreak.

Infectious diseases affect marine fisheries and aquaculture economics.

Seafood is a growing part of the economy, but its economic value is diminished by marine diseases. Infectious diseases are common in the ocean, and here we tabulate 67 examples that can reduce commercial species' growth and survivorship or decrease seafood quality. These impacts seem most problematic in the stressful and crowded conditions of aquaculture, which increasingly dominates seafood production as wild fishery production plateaus. For instance, marine diseases of farmed oysters, shrimp, abalone, and various fishes, particularly Atlantic salmon, cost billions of dollars each year. In comparison, it is often difficult to accurately estimate disease impacts on wild populations, especially those of pelagic and subtidal species. Farmed species often receive infectious diseases from wild species and can, in turn, export infectious agents to wild species. However, the impact of disease export on wild fisheries is controversial because there are few quantitative data demonstrating that wild species near farms suffer more from infectious diseases than those in other areas. The movement of exotic infectious agents to new areas continues to be the greatest concern.

Evidence of threat to European economy and biodiversity following the introduction of an alien pathogen on the fungal-animal boundary.

Recent years have seen a global and rapid resurgence of fungal diseases with direct impact on biodiversity and local extinctions of amphibian, coral, or bat populations. Despite similar evidence of population extinction in European fish populations and the associated risk of food aquaculture due to the emerging rosette agent Sphaerothecum destruens, an emerging infectious eukaryotic intracellular pathogen on the fungal-animal boundary, our understanding of current threats remained limited. Long-term monitoring of population decline for the 8-year post-introduction of the fungal pathogen was coupled with seasonal molecular analyses of the 18S rDNA and histological work of native fish species organs. A phylogenetic relationship between the existing EU and US strains using the ribosomal internal transcribed spacer sequences was also carried out. Here, we provide evidence that this emerging parasite has now been introduced via Pseudorasbora parva to sea bass farms, an industry that represents over 400 M€€ annually in a Mediterranean region that is already economically vulnerable. We also provide for the first time evidence linking S. destruens to disease and severe declines in International Union for Conservation of Nature threatened European endemic freshwater fishes (i.e. 80% to 90 % mortalities). Our findings are thus of major economic and conservation importance.

Estimating costs of sea lice control strategy in Norway.

This paper explores the costs of sea lice control strategies associated with salmon aquaculture at a farm level in Norway. Diseases can cause reduction in growth, low feed efficiency and market prices, increasing mortality rates, and expenditures on prevention and treatment measures. Aquaculture farms suffer the most direct and immediate economic losses from diseases. The goal of a control strategy is to minimize the total disease costs, including biological losses, and treatment costs while to maximize overall profit. Prevention and control strategies are required to eliminate or minimize the disease, while cost-effective disease control strategies at the fish farm level are designed to reduce the losses, and to enhance productivity and profitability. Thus, the goal can be achieved by integrating models of fish growth, sea lice dynamics and economic factors. A production function is first constructed to incorporate the effects of sea lice on production at a farm level, followed by a detailed cost analysis of several prevention and treatment strategies associated with sea lice in Norway. The results reveal that treatments are costly and treatment costs are very sensitive to treatment types used and timing of the treatment conducted. Applying treatment at an early growth stage is more economical than at a later stage.

Stochastic modelling of direct costs of pancreas disease (PD) in Norwegian farmed Atlantic salmon (Salmo salar L.).

An economic model for estimating the direct costs of disease in industrial aquaculture was developed to include the following areas: biological losses, extraordinary costs, costs of treatment, costs of prevention and insurance pay-out. Direct costs of a pancreas disease (PD) outbreak in Norwegian farmed Atlantic salmon were estimated in the model, using probability distributions for the biological losses and expenditures associated with the disease. The biological effects of PD on mortality, growth, feed conversion and carcass quality and their correlations, together with costs of prevention were established using elicited data from an expert panel, and combined with basal losses in a control model. Extraordinary costs and costs associated with treatment were collected through a questionnaire sent to staff managing disease outbreaks. Norwegian national statistics for 2007 were used for prices and production costs in the model. Direct costs associated with a PD-outbreak in a site stocked with 500,000 smolts (vs. a similar site without the disease) were estimated to NOK (Norwegian kroner) 14.4 million (5% and 95% percentile: 10.5 and 17.8) (NOK=euro0.12 or $0.17 for 2007). Production was reduced to 70% (5% and 95% percentile: 57% and 81%) saleable biomass, and at an increased production cost of NOK 6.0 per kg (5% and 95% percentile: 3.5 and 8.7).

An economic evaluation of the control of three notifiable fish diseases in the United Kingdom.

We summarised the challenges faced in an ex ante cost-benefit appraisal of United Kingdom government spending on disease surveillance for three notifiable fish diseases: infectious salmon anaemia (ISA), viral haemorrhagic septicaemia (VHS) and infectious haemorrhagic necrosis (IHN). We used a social cost-benefit analysis and adopted a national perspective. We compared costs of current public and private surveillance effort with the benefits stated in terms of the avoided private and social costs of potential disease outbreaks. Spending on ISA and VHS were predicted to be efficient; the benefit-cost ratios were always >or=3.2 for ISA and >or=5.8 for VHS for all nine scenarios examined for each infection. However, the benefit-cost ratio for IHN was predicted never to exceed 1.6, and was <1.0 in five of the nine scenarios-so spending on IHN would be harder to justify.

Two multivalvulid myxozoans causing postmortem myoliquefaction: Kudoa megacapsula n. sp. from red barracuda (Sphyraena pinguis) and Kudoa thyrsites from splendid alfonso (Beryx splendens).

Postmortem myoliquefaction associated with multivalvulid myxozoans was found in fillets of red barracuda (Sphyraena pinguis) and splendid alfonso (Beryx splendens), which were imported to Japan from China and South Africa, respectively. Morphological examinations of the myxozoans from the somatic muscle of red barracuda revealed that spores (30.3-44.7 microm in maximum thickness) had 4 distinct winglike valves, in which 1 extremely large (12.7 x 5.8 microm), 2 small, and 1 vestigial polar capsule were present. The small subunit ribosomal DNA sequence analysis showed that the myxozoan cluster within a clade was composed of Kudoa thyrsites, Kudoa minithyrsites, and Kudoa lateolabracis, all having stellate spores with 1 polar capsule larger than the other 3. On the basis of these characteristics, we describe this parasite as Kudoa megacapsula n. sp. Morphological and molecular analyses of the myxozoan from splendid alfonso identified it as K. thyrsites, which has been described from many marine fishes. To our knowledge, this is the first record of K. thyrsites in splendid alfonso.

Cardiomyopathy syndrome in farmed Atlantic salmon Salmo salar: occurrence and direct financial losses for Norwegian aquaculture.

Cardiomyopathy syndrome (CMS) was first diagnosed in the mid-1980s in farmed Atlantic salmon in Norway, and later also in Scotland and the Faeroe Islands. In Norway the number of diagnosed cases increased from 25 to 103 in the period from 1998 to 2001 according to the National Veterinary Institute (NVI) records. Very little is known about the causes of the disease and there is no documentation of its impact on the farmed salmon industry. This field survey was performed to collect information on occurrence, risk factors and the economic importance of CMS in sea farmed Atlantic salmon Salmo salar in Norway. Data were collected in January 2001 from a total of 174 groups of farmed salmon which had been previously transferred to sea during 1999 and 2000. Approximately 11.5% of all groups of salmon in our study experienced cases of CMS. Affected fish were presumably in generally good condition prior to time of death. In fish which had completed the seawater production cycle, CMS occurred more than 1 yr (median 395 d, >2 kg body weight) after seawater transfer. In fish transferred into the sea during autumn 2000 which had not completed the seawater cycle during the study period, CMS was diagnosed at a weight as low as 700 g. Although sudden death is characteristic, CMS may be regarded as a chronic disease, with moderately elevated mortality rates at site level. Affected groups showed significantly increased mortality, causing a direct annual financial loss for the industry of Euros 4.5 to 8.8 million on fish farms. Preventive prescheduled slaughtering of salmon, which is performed on many affected farms, may be too costly when done too early.

Increased efficacy of immersion vaccination in fish with hyperosmotic pretreatment.

Immersion vaccination is common practice in aquaculture, because of its convenience for mass vaccination with sufficient protection. However, the mechanisms of antigen uptake and presentation, resulting in a protective immune response and the role of the innate immune system therein are largely unknown. The impact of immersion vaccination on fish physiology and on the ensuing innate and specific immune response was characterized with fluorescently labeled particulate and soluble model antigens. Vaccination of common carp by direct immersion (DI) or hyperosmotic immersion (HI; direct immersion, preceded by a brief immersion in a hypertonic solution) greatly enhanced the uptake of soluble, but not particulate antigen through temporary disruption of the integrity of the epithelia of gills and skin. Damage induced is mild and does not impose additional stress over the handling associated with immersion vaccination. Especially HI briefly but strongly activates the innate immune system. We conclude that HI more effectively increased the uptake of vaccine and enhanced the efficacy by which vaccine components are processed and presented by the innate immune system, dually enhancing the mucosal immune response. Understanding the mechanisms involved in uptake and processing of vaccine in the early phase of the immune response will greatly benefit the design of immersion vaccination.

Diseases of tunas, Thunnus spp.

Much is known about those aspects of tuna health which can be studied in wild populations, e.g. helminth parasites. However, because aquaculture of these species is in its infancy, knowledge of microbial, nutritional and environmental diseases is limited. This review is an attempt to bring together the available information on those diseases of Thunnus spp. which cause significant morbidity, mortality or economic loss. In doing so it has become clear that much more research needs to be undertaken on the physiology of the species (southern, northern and Pacific bluefin tuna) currently used in aquaculture in order for the pathogenesis of some conditions to be properly understood. Attempts at hatchery culture of Pacific bluefin tuna has indicated that Thunnus spp. will be problematic to hatch and propagate.