Zeuxapta Seriolae Research Articles

A decision support tool for parasite management in fish aquaculture

AbstractA decision support tool was developed to aid management of problematic parasites in marine fish aquaculture. The tool provides biologically relevant treatment intervals to interrupt the life cycle of ectoparasitic flatworms that occur in global kingfish and amberjack (Seriola spp.) aquaculture. Temperature‐dependent life cycle parameters for the ‘skin flukes’, Benedenia seriolae and Neobenedenia girellae, and the ‘gill fluke’, Zeuxapta seriolae, were derived from published data and modelled using non‐linear regressions. Increasing temperatures shortened the duration of most life cycle parameters of all parasites. Salinity had no effect on the timing of life cycle parameters but limited hatching success in hypo‐ and hypersaline conditions. The tool, named BeNeZe after the first two letters of each parasite genera, enables rapid determination of treatment intervals for two consecutive medicinal immersion or ‘bathing’ treatments—the first to kill adult flatworms attached to fish and the second to prevent maturity of new parasite recruits. As temperature increases, the interval between treatments and the ‘window’ within which the second treatment should be applied is reduced. The tool can be used for multi‐species infections. The inclusion of parasite taxonomy, biology and behaviour as part of an integrated management strategy is reviewed. Available through an open access app, BeNeZe is intended to be applied in conjunction with farm biosecurity, surveillance, management measures and recognition of independent management units. BeNeZe can be used to reduce infection burdens, improve fish welfare and production and reduce treatment number and frequency.

Effect of garlic extract and diallyl sulfide immersion baths in the life stages of Zeuxapta seriolae, a parasite of California yellowtail (Seriola dorsalis)

Effect of garlic extract and diallyl sulfide immersion baths in the life stages of Zeuxapta seriolae, a parasite of California yellowtail (Seriola dorsalis)

Evaluation of Praziquantel Efficacy against Zeuxapta seriolae Infections in Greater Amberjack, Seriola dumerili

The aim of this study was to evaluate the efficacy of dietary praziquantel (PZQ), a promising fish anthelminthic, against Zeuxapta seriolae, a lethal ectoparasite of greater amberjack (Seriola dumerili Risso) farmed in the Mediterranean and elsewhere. The trial was carried out in small cages (3 m3) in situ, harbouring fish (125 ± 14 g) naturally infected with Z. seriolae, at 25 ± 1 °C water temperature. Praziquantel-medicated diet (150 mg PZQ/kg fish) was delivered for three days against a control group. Measurement of both adults and oncomiracidia of Z. seriolae in sampled gill arches revealed significant differences between the tested groups (PZQ: 19.3 ± 9.8 vs. Control: 3.8 ± 6.3). Considering an estimated efficacy of 80.4% in the medicated fish, the present study indicates that oral PZQ treatments can confront Z. seriolae infections considerably in farmed greater amberjack and, perhaps, replace the commonly used hydrogen peroxidase baths.

Four polyopisthocotyleans (Platyhelminthes: Monogenea) from carangid fishes in the Mediterranean, off the Algerian coasts

Four polyopisthocotyleans were collected from the gill filaments of carangids from off the Algerian coast, southern Mediterranean. Specimens of Gastrocotyle trachuri van Beneden & Hesse, 1863 (Gastrocotylidae) and Cemocotyle cf. trachuri Dillon & Hargis, 1965 (Heteraxinidae) from the Mediterranean horse mackerel Trachurus mediterraneus (Steindachner), Zeuxapta seriolae (Meserve, 1938) (Heteraxinidae) from the greater amberjack Seriola dumerili (Risso) and Pyragraphorus hollisae Euzet & Ktari, 1970 (Pyragraphoridae) from the pompano Trachinotus ovatus (Linnaeus) are redescribed based on newly collected specimens. Their taxonomically important morphological features (male copulatory organ and clamp sclerites) are described and illustrated, and the morphometric variation between Mediterranean and oceanic specimens is highlighted. Careful examination of the specimens of Cemocotyle Sproston, 1946 from the Mediterranean revealed that they exhibited unusual features compared with Cemocotyle trachuri Dillon & Hargis, 1965 from the Pacific, mainly the absence of the terminal lappet, thus questioning previous records of this species in the Mediterranean. New geographical locality records are provided for Z. seriolae and P. hollisae. The presence of C. cf. trachuri and Z. seriolae in the Mediterranean is noteworthy as these monogeneans were initially described in the Pacific Ocean. This study extends the geographical range of Z. seriolae to the southern Mediterranean.

Anthelmintic herbal extracts as potential prophylactics or treatments for monogenean infections in cultured yellowtail kingfish (Seriola lalandi)

Monogenean parasites pose a considerable threat to the aquaculture of yellowtail kingfish, Seriola lalandi. Current chemotherapeutic treatments are expensive, labor intensive and can cause mortality if incorrectly administered. Many medicinal herbs possess anti-parasitic properties and therefore have potential as an alternative or supplement to current treatment methods. The anthelminthic effects of garlic, rosemary, and commercially manufactured herbal products were trialed both in vitro and in vivo against two species of monogeneans, Neobenedenia girellae and Zeuxapta seriolae, to assess their suitability for use in yellowtail kingfish aquaculture. The survival of adult N. girellae and Z. seriolae and larval N. girellae (i.e. oncomiracidia) were assessed in vitro, by exposure to seawater solutions containing the herbal products. All herbal-seawater solutions significantly reduced the survival of mature N. girellae and Z. seriolae and N. girellae oncomiracidia relative to the controls. Two in vivo trials were then conducted to examine the preventative and curative treatment effects of rosemary and garlic against Z. seriolae infections, by supplementing these products into their feed. The first trial fed supplemented diets for 30 days prior to exposure with Z. seriolae oncomiracidia. The second trial examined the potential curative effects of these extracts by feeding supplemented diets to yellowtail kingfish already infected with Z. seriolae for 10 and 20 days. The effect of these curative treatment diets on recruitment of juvenile Z. seriolae was also assessed. Supplementation of rosemary and garlic products into feed 30 days prior to experimental exposure significantly reduced Z. seriolae infection success, while supplementation of garlic powder, rosemary extract, and rosemary oil onto pellets significantly reduced Z. seriolae abundance on yellowtail kingfish after 20 days of feeding. Recruitment of juvenile Z. seriolae was also significantly reduced.

Mixed parasitism induced experimentally in yellowtail, Seriola dorsalis reared in RAS: intensity and spatial distribution on the skin and gills

Fish mariculture from the genus Seriola spp. can present high mortalities due to parasites. In Mexico, the mortality yellowtail Seriola dorsalis caused by parasites is low, and there are no reports of massive mortality events. However, as the aquaculture activity of yellowtail intensifies, parasites will be increasingly conspicuous. Therefore, the present study is an aim to know S. dorsalis ’s susceptibility to a monogenean infection mixed under RAS experimental conditions and their intensity and spatial distribution on the skin and gills. In this study, a parasitic mix induction was performed using two monogenean species such as Zeuxapta seriolae and Benedenia seriolae besides the Amyloodinium ocellatum , a dinoflagellate that was naturally presented. At the end of the experiment after 45 days, B. seriolae prevalence was 100% with a mean intensity of 122 parasites and showed a preference for the head and body of the fish. Zeuxapta seriolae prevalence was 100% with a mean intensity of 40 parasites preferentially found in the second branchial arch. In the case of A. ocellatum prevalence was of 100% with a mean intensity greater than 200 trophozoites per fish. The fish mortality reached 90% at the end of the experiment. During the infection, the fish weight decreased a 14% at the end of the experiment. Therefore, it will be necessary to carry out prophylactic and control strategies, to reduce the impact of these parasites under culture conditions.

Parasites of amberjacks from the archipelago of Madeira, Eastern Atlantic.

Amberjacks, Seriola spp., are a group of carangid fishes of economic importance for fisheries and aquaculture worldwide. A survey of the parasites of greater amberjack S. dumerili and almaco jack or longfin yellowtail S. rivoliana from the Madeira archipelago (including the Madeira and Selvagens Islands) was carried out. This work is the first parasitological study of these 2 species in the Eastern Atlantic. A total of 14 parasite taxa were detected in the 47 fish analysed: Allencotyla mcintoshi, Stephanostomum petimba, Rhadinorhynchus sp. and Caligus aesopus (in both Seriola spp.); Dionchus agassizi, Zeuxapta seriolae, Tormopsolus orientalis, Didymocystis sp. and Anisakis sp. (in S. rivoliana); Tetrochetus coryphaenae, Stephanostomum sp., S. ditrematis, Oncophora melanocephala and Hysterothylacium seriolae (in Seriola dumerili). The monogenean Dionchus agassizi and the nematode O. melanocephala constitute new host records for the genus Seriola, and the species Allencotyla mcintoshi, Z. seriolae, Tormopsolus orientalis, H. seriolae, and C. aesopus are reported in the region of Madeira for the first time. Some of the parasites detected, in particular Z. seriolae and C. aesopus, could constitute a threat to amberjack aquaculture, and measures should be taken to prevent their introduction into sea cages.

Random and systematic sampling error when hooking fish to monitor skin fluke (Benedenia seriolae) and gill fluke (Zeuxapta seriolae) burden in Australian farmed yellowtail kingfish (Seriola lalandi)

The Australian farmed yellowtail kingfish (Seriola lalandi, YTK) industry monitor skin fluke (Benedenia seriolae) and gill fluke (Zeuxapta seriolae) burden by pooling the fluke count of 10 hooked YTK. The random and systematic error of this sampling strategy was evaluated to assess potential impact on treatment decisions.Fluke abundance (fluke count per fish) in a study cage (estimated 30,502 fish) was assessed five times using the current sampling protocol and its repeatability was estimated the repeatability coefficient (CR) and the coefficient of variation (CV). Individual body weight, fork length, fluke abundance, prevalence, intensity (fluke count per infested fish) and density (fluke count per Kg of fish) were compared between 100 hooked and 100 seined YTK (assumed representative of the entire population) to estimate potential selection bias.Depending on the fluke species and age category, CR (expected difference in parasite count between 2 sampling iterations) ranged from 0.78 to 114 flukes per fish. Capturing YTK by hooking increased the selection of fish of a weight and length in the lowest 5th percentile of the cage (RR = 5.75, 95% CI: 2.06–16.03, P-value = 0.0001). These lower end YTK had on average an extra 31 juveniles and 6 adults Z. seriolae per Kg of fish and an extra 3 juvenile and 0.4 adult B. seriolae per Kg of fish, compared to the rest of the cage population (P-value < 0.05).Hooking YTK on the edge of the study cage biases sampling towards the smallest and most heavily infested fish in the population, resulting in poor repeatability (more variability amongst sampled fish) and an overestimation of parasite burden in the population. In this particular commercial situation these finding supported that health management program, where the finding of an underestimation of parasite burden could provide a production impact on the study population. In instances where fish populations and parasite burdens are more homogenous, sampling error may be less severe. Sampling error when capturing fish from sea cage is difficult to predict. The amplitude and direction of this error should be investigated for a given cultured fish species across a range of parasite burden and fish profile scenarios.

Monogenean Parasite Cultures: Current Techniques and Recent Advances.

Global expansion in fish production and trade of aquatic ornamental species requires advances in aquatic animal health management. Aquatic parasite cultures permit diverse research opportunities to understand parasite-host dynamics and are essential to validate the efficacy of treatments that could reduce infections in captive populations. Monogeneans are important pathogenic parasites of captured captive fishes and exhibit a single-host life cycle, which makes them amenable to in vivo culture. Continuous cultures of oviparous monogenean parasites provide a valuable resource of eggs, oncomiracidia (larvae) and adult parasites for use in varied ecological and applied scientific research. For example, the parasite-host dynamics of Entobdella soleae (van Beneden and Hesse, 1864) and its fish host, Solea solea (Linnaeus, 1758), is one of the most well-documented of all monogeneans following meticulous, dedicated study. Polystoma spp. cultures provide an intriguing model for examining evolution in monogeneans because they exhibit two alternative phenotypes depending on the age of infection of amphibians. Furthermore, assessments of the ecological, pathological and immunological effects of fish parasites in aquaculture have been achieved through cultures of Gyrodactylus von Nordmann, 1832 spp., Benedenia seriolae (Yamaguti, 1934), Neobenedenia Yamaguti, 1963 spp. and Zeuxapta seriolae (Meserve, 1938). This review critically examines methods to establish and maintain in vivo monogenean monocultures on finfish, elasmobranchs and amphibians. Four separate approaches to establish cultures are scrutinised including the collection of live infected hosts, cohabiting recipient hosts with infected stock, cohabiting hosts with parasite eggs or oncomiracidia (larvae) and direct transfer of live adult parasites onto new fish hosts. Specific parasite species' biology and behaviour permits predictive collection of parasite life stages to effectively maintain a continuous culture, while environmental parameters can be altered to manipulate parasite generation time. Parasite virulence and biosecurity are vital components of a well-managed culture to ensure appropriate animal welfare and uncontaminated surrounding environments. Contemporary approaches and techniques are reviewed to ensure optimised monogenean cultures, which ultimately can be used to further our understanding of aquatic parasitology and identify mechanisms to limit infestations in public aquaria, ornamental trade and intensive aquaculture.

Potential role of ectoparasites (Zeuxapta seriolae and Caligus lalandei) in the transmission of pathogenic bacteria in yellowtail kingfish Seriola lalandi, inferred from cultivable microbiota and molecular analyses.

Potential role of ectoparasites (Zeuxapta seriolae and Caligus lalandei) in the transmission of pathogenic bacteria in yellowtail kingfish Seriola lalandi, inferred from cultivable microbiota and molecular analyses.

Praziquantel delivery via moist pellets to treat monogenean parasites of yellowtail kingfish Seriola lalandi: efficacy and feed acceptance.

Praziquantel (PZQ) is registered for oral use against Benedenia seriolae infecting Seriola spp. in Japan, but its bitter taste causes poor palatability. Incorporating PZQ in a moist pellet may help mask the flavor to improve intake. Altering delivery, however, may influence efficacy. We assessed the minimum effective concentrations of PZQ in moist pellets delivered by intubation for the monogeneans Zeuxapta seriolae and B. seriolae infecting yellowtail kingfish Seriola lalandi in flow-through tanks. The optimised dose was then evaluated in a sea-cage of S. lalandi to assess feed acceptance and efficacy. During intubation trials, efficacy was assessed as a percent reduction compared to control groups; in the field trial, efficacy was assessed by a percent reduction after treatment. PZQ delivered by intubation at 70 mg kg-1 body weight (BW) for 3 d was 99.7 and 81.7% effective against Z. seriolae and B. seriolae, respectively. Increasing the dose to 120 mg kg-1 BW for 3 d had a similar efficacy against Z. seriolae (98.4%) and increased efficacy against B. seriolae to 89.2%, but partial emesis of the medicated feed was sometimes noted. S. lalandi in a sea-cage at 17°C readily consumed PZQ administered daily in moist pellets at 70 mg kg-1 BW for 3 d (inclusion rate: 5.15 g kg-1), which significantly reduced Z. seriolae and B. seriolae abundance with 99.4 and 81.6% efficacy, respectively. Juvenile B. seriolae were common on the eyes of fish post-treatment which indicates a strategically timed repeat treatment is necessary.

The direction of sampling bias when hooking fish from a sea cage: case study of fluke monitoring in Australian farmed Yellowtail Kingfish (Seriola lalandi)

Event Abstract Back to Event The direction of sampling bias when hooking fish from a sea cage: case study of fluke monitoring in Australian farmed Yellowtail Kingfish (Seriola lalandi) Charles Caraguel1*, James Fensham1, Matt Landos2, Erin Bubner3 and Trent D'Antignana3 1 The University of Adelaide, School of Animal and Veterinary Sciences, Australia 2 Future Fisheries Veterinary Services, Australia 3 Flinder University / CleanSeas , Australia Purpose: The Australian Yellowtail Kingfish (Seriola lalandi, YTK) farming industry routinely monitors the burden of skin fluke (Benedenia seriolae, SF) and gill fluke (Zeuxapta seriolae, GF) in fish cages to make treatment decisions. Up to 10 YTK are conveniently captured using hook and line from the side of the cage and flukes are collected and counted. It is generally believed that hooking caged fish tends to select the fast swimming, dominant, and healthier fish. This is expected to result in an under-estimation of parasite prevalence and burden which could mislead or delay intervention. However, the presence and direction of a sampling bias when hooking YTK has not been investigated before. Methods: Individual weight, fork length and fluke counts were compared between 100 hooked and 100 seined YTK, assumed to be a fair representation of the study cage population. Results: Hooking increased by almost 6 times the probability of sampling YTK of a weight and length in the lowest 5th percentile of the cage (RR=5.75, p<0.001). These low end fish had on average an extra 32 juvenile and 6 adult GF per kg of fish and an extra 3 juvenile and 0.4 adult SF per kg of fish, compared to the rest of the population (p<0.05). Conclusions: Hooking biased sampling towards the smallest and most heavily infested fish resulting in an over-estimation of parasite burden in the study cage. Relevance: In Australia, a short rod is used to hook YTK which mainly access the smaller fish swimming on the edge of the cage. Hooking methods accessing fish from the centre of the cage may select a different category of fish. In the instance where the cage population is very homogenous, sampling bias may be less severe. More cage scenarios with different parasite burdens and fish profiles should be investigated to better predict the presence and direction of the bias. Keywords: Sampling, Bias (Epidemiology), Ectoparasitic Infestations, Aquaculture, yellowtail kingfish Conference: AquaEpi I - 2016, Oslo, Norway, 20 Sep - 22 Sep, 2016. Presentation Type: Oral Topic: Aquatic Animal Epidemiology Citation: Caraguel C, Fensham J, Landos M, Bubner E and D'Antignana T (2016). The direction of sampling bias when hooking fish from a sea cage: case study of fluke monitoring in Australian farmed Yellowtail Kingfish (Seriola lalandi). Front. Vet. Sci. Conference Abstract: AquaEpi I - 2016. doi: 10.3389/conf.FVETS.2016.02.00041 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 30 Apr 2016; Published Online: 14 Sep 2016. * Correspondence: Dr. Charles Caraguel, The University of Adelaide, School of Animal and Veterinary Sciences, Roseworthy, South Australia, 5371, Australia, charles.caraguel@adelaide.edu.au Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Charles Caraguel James Fensham Matt Landos Erin Bubner Trent D'Antignana Google Charles Caraguel James Fensham Matt Landos Erin Bubner Trent D'Antignana Google Scholar Charles Caraguel James Fensham Matt Landos Erin Bubner Trent D'Antignana PubMed Charles Caraguel James Fensham Matt Landos Erin Bubner Trent D'Antignana Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Patterns of genetic variation and life history traits of Zeuxapta seriolae infesting Seriola lalandi across the coastal and oceanic areas in the southeastern Pacific Ocean: potential implications for aquaculture.

BackgroundThe monogenean, Zeuxapta seriolae, is a host-specific parasite that has an extensive geographical distribution on its host, Seriola lalandi, and is considered highly pathogenic in farmed fish. In recent years, developing cultures of S. lalandi in different coastal localities in Southeastern Pacific Ocean (SEP) have been affected by moderate and heavy infections of this parasite, attributed to contagion from wild to farmed fish. Here, we evaluated the pattern of genetic variations and biological traits of Z. seriolae in a spatial and temporal scale across its geographical distribution in SEP to determine its genetic status and biological traits, which could affect its transmission dynamics from wild to farmed fish.MethodsWild fish and their parasites were sampled from fisheries in the northern Chilean coast (NCC: 24°S-30°S) and Eastern islands (JFA: ca 33°S; 80°W) between 2012 and 2014. Fragments of 816 bp of the cytochrome c oxidase subunit I (COI) gene was sequenced for 112 individuals from NCC and 63 from JFA and compared using AMOVA. Prevalence and intensity of Z. seriolae were calculated for each area. The parasite body size, fecundity and size at sexual maturity were estimated for 177 parasites from NCC and 128 from JFA, and significant differences were evaluated using GLM.ResultsGeographical genetic structuring was detected for Z. seriolae across SEP, with a population in NCC and the other in JFA, both with the same high haplotype diversity. Neutrality tests and mismatch analyses indicated that both Z. seriolae populations are stable. Parasite biological traits such as fecundity, body size, and size at sexual maturity, and population parameters varied significantly between geographical areas.ConclusionTwo genetic groups of Z. seriolae were detected in wild fish across SEP. Because of the seasonal migration of wild host and temporal contact with farming, quantifying the genetic diversity and level of gene flow or isolation between parasite populations is useful for fish health management in farming. The smallest size of sexual maturity in parasites from NCC is predictive of shorter life cycles, and their high genetic diversity suggests high evolutionary potential and high transmission of this parasite to farmed hosts.

Captive spawning and larval rearing of California yellowtail (Seriola lalandi)

A captive population of California yellowtail (Seriola lalandi) was used to document spawning patterns, including measures of egg production, population fecundity and egg and larval quality from 2007 to 2010. Spawned eggs were also used to document larval development and to develop rearing techniques for aquaculture in the region. Broodstock growth and condition factor were best when feeding rations were maintained at 10–15% body weight week−1 during the warm summer months. A winter ration based on satiation feeding was typically 4% body weight week−1. During the 4-year study period, the only broodstock health issue was an infestation by the parasitic gill fluke Zeuxapta seriolae, which was readily treated. Spawning occurred naturally in the 140 m3 tank when the ambient water temperature reached 16°C and ended when the temperature exceeded 22°C. Egg production reached a maximum in 2010 when 43 spawn events were recorded from a pool of nine females yielding 36.8 million eggs in total. The average female size at this time was 20 kg, which equated to a total annual population fecundity of approximately 226 000 eggs kg−1 female year−1. Larval rearing trials yielded survival rates as high as 5.8% from egg to 50 days post-hatch (dph). Successful larval culture methods included the addition of algae paste for green water culture, rotifers (20 rotifers mL−1) at 2 dph and Artemia (5 Artemia mL−1) at 6 dph. Larvae were transferred from the incubation tank at 10 dph to a shallower tank with 33% greater surface area to accommodate the larvae's strong orientation to surface waters. This research represents the first documentation of successful spawning and larval rearing for S. lalandi in the eastern Pacific.

Post-larval development of the microcotylid monogenean Sparicotyle chrysophrii (Van Beneden and Hesse, 1863): Comparison with species of Microcotylidae and Heteraxinidae

The chronology of post-larval development in S. chrysophrii, a polyopisthocotylean monogenean parasite of the gilthead seabream ( Sparus aurata L.), was experimentally studied. It is compared with other species within the Microcotylidae and the Heteraxinidae, including an analysis of the changes in attachment and the growth rate. Gilthead seabreams infected by larvae of S. chrysophrii were killed periodically in order to collect the different developmental stages. Parasite total body length, haptor length, largest clamp width, and total number of clamps were recorded. Specimens of S. chrysophrii in culture conditions at 20 °C became gravid after 26–30 days, with 37 pairs of clamps. The S. chrysophrii growth curve appears to be sigmoid with 3 growth periods (slow–fast–slow). The haptor of S. chrysophrii grows linearly with total body length, but the main contribution to total body length growth is that of the non-haptoral body. The relationship between number of clamps and total body length during development can be fitted to an exponential curve for all the reviewed species, i.e.: Microcotyle spinicirrus, Microcotyle donavini, Microcotyle gotoi, Microcotyle sebastis, Microcotyle hiatulae, Polylabroides multispinosus, Bivagina tai, Heteraxinoides xanthophilis, Heteraxine heterocerca, and Zeuxapta seriolae. The sequence of events was common for all of the species compared: terminal lappet is lost when about 15% of clamps were developed; primordia of testes at approximately 30% of clamps developed, and maturity (as first egg appearance) at about 65% of clamps developed.

Offshore Farming of the Mediterranean Amberjack (Seriola dumerili) in the Northeastern Mediterranean

The growth rate, survival, and feeding parameters of Mediterranean amberjack (Seriola dumerili Risso, 1810) cultivated in offshore cages in the Gulf of İskenderun (Hatay, Turkey) were investigated from July 2006 to March 2008. Two offshore cages (339 m3) were placed at a depth of 10 m in a sheltered area 500 m off the coast. Juveniles (101.97±14.54 g), caught with seine nets 400-1200 m from the coast, were stocked in the cages at 250 per cage. Fish in one cage, Group A, were fed commercial pellets for all 20 months whilst fish in the second cage, Group B, were fed pellets for the first 16 months and frozen sardines for the following four. The mean live weight, survival, feed conversion ratio, daily feed consumption, and water quality parameters were recorded monthly. Group B reached a significantly (p&lt;0.05) greater weight (2785.00±64.91 g) than Group A (2441.14±38.13 g). Food conversion ratios ranged 1.16-2.46 for group A and 1.10-2.28 for group B, low when compared with other studies on amberjacks in the Mediterranean. Average mortality was 25%, due to a Zeuxapta seriolae (Monogenea: Heteraxinidae) infection in December 2006 (20%) and fish handling for measurement in June 2007 (~5%). The farmed amberjacks had significantly higher protein and lipid contents than their wild counterparts at the end of the 20-month feeding period. Amberjacks found frozen sardines more appealing than pellets, especially during the winter. In conclusion, it is advised to feed Mediterranean amberjack frozen sardines or other trash fish during the winter grow-out period. Their rapid growth rate, as well as their adaptability to farming, make offshore net cages a promising system for the aquaculture of this species.

Pathological obstacles of newly-introduced fish species in Mediterranean mariculture: a review

Species diversification has been extensively employed in Mediterranean mariculture industry as a tool to relief the crisis resulting from market saturation and overproduction of the two main representatives, sea bass (Dicentrarchus labrax) and gilthead sea bream (Sparus aurata). Numerous new promising candidates belonging to several fish families such as Sparidae, Polyprionidae, Serranidae, Sciaenidae, Soleidae, Carangidae and Scombridae have been introduced to provide alternative culture choices in Mediterranean. The farming potential of these species in production scale has received some or little success partly due to the fact that their entrance has not been accompanied without the presence of considerable pathological problems. Bacterial outbreaks causing serious problems have been mainly induced by Photobacterium damsella subsp. piscicida, Vibrio alginolyticus, V. harveyi, Tenacibaculum maritimum and Flavobacterium sp. Detrimental parasitic pathogens included the myxosporean Enteromyxum leei, the ciliates Cryptocaryon irritans and Uronema spp., the flagellate Amyloodinium occelatum, the monogenean Zeuxapta seriolae and the digeneans Paradeontacylix-like spp. Viral encephalopathy and retinopathy infections and the chlamydia-like bacteria causing Epitheliocystis disease are also of significance importance. Numerous other agents of lesser pathogenic significance as well as other occasionally recorded pathogens are also mentioned in this review. Additional research effort has to be devoted to the pathogenesis of important pathogens and the interactions with their hosts to assist the viability of new fish species farming in Mediterranean region.

Efficacy of orally administered praziquantel against Zeuxapta seriolae and Benedenia seriolae (Monogenea) in yellowtail kingfish Seriola lalandi

We investigated the efficacy of praziquantel (PZQ) administered orally to yellowtail kingfish (Seriola lalandi in sea-cage aquaculture in South Australia) against the monogeneans Zeuxapta seriolae and Benedenia seriolae infesting gills and skin, respectively. PZQ was administered to fish by surface-coating feed pellets (Trial 1) or by direct intubation of the stomach (Trial 2). In both trials 4 daily doses were administered: 50 and 75 mg kg(-1) body weight (BW) d(-1) for 6 d, and 100 and 150 mg kg(-1) BW d(-1) for 3 d. Mean parasite intensity was compared between medicated fish and unmedicated control fish. In Trial 1, fish fed lower daily doses of PZQ for 6 d (50 and 75 mg kg(-1) BW d(-1)) had fewer Z. seriolae and B. seriolae than fish fed higher daily doses for 3 d (100 and 150 mg kg(-1) BW d(-1)). Fish rejected feed pellets surface-coated with PZQ, suggesting PZQ affected palatability of feed, and may explain differences in efficacy between treatments. In Trial 2, where PZQ was administered by intubation, there were fewer Z. seriolae and B. seriolae in medicated fish than control fish. Intubated PZQ was also effective against newly recruited Z. seriolae and B. seriolae. PZQ could be developed as a useful treatment for Z. seriolae and B. seriolae parasitising S. lalandi in sea-cage aquaculture if suspected palatability problems are resolved.

Effects of the gill monogenean Zeuxapta seriolae (Meserve, 1938) and treatment with hydrogen peroxide on pathophysiology of kingfish, Seriola lalandi Valenciennes, 1833

Infections by the gill fluke Zeuxapta seriolae are a serious concern for sea cage aquaculture of kingfish, Seriola lalandi. The present study aimed to determine the pathophysiological effects of a progressive infection with Z. seriolae and the effects of treatment with hydrogen peroxide. For the progression of infection study, infected fish were taken from a sea cage farm, treated to remove parasites and then infected by cohabitation with heavily infected fish. Samples were taken at 2-week intervals for 8 weeks. Infection intensity peaked at 4 weeks post-infection (mean intensity 565.9) and the number of mature worms (2 mm fixed length or larger) peaked at 6 weeks post-infection. Attachment of Z. seriolae appeared to cause little localized pathology; however, the occurrence of hyperplastic lamellae increased as the infection progressed. Haemoglobin concentrations were negatively correlated with Z. seriolae intensity and were lower than controls at 4 weeks (35.8% decrease) and 6 weeks (57.4% decrease) post-infection. Blood lactate concentration and plasma osmolality increased throughout the course of infection. For the effect of treatment experiment, groups of infected and non-infected fish were sampled either before or after treatment with hydrogen peroxide. Treated fish from both infected and uninfected groups had increased plasma lactate, osmolality and pH compared with pre-treatment groups. Treatment with hydrogen peroxide appeared to have acute effects on fish health but the magnitude (e.g. lactate, osmolality) and extent of the effects (e.g. haemoglobin) was much less than that caused by chronic infection with Z. seriolae.

An egg-laying rhythm in Zeuxapta seriolae (Monogenea: Heteraxinidae), a gill parasite of yellowtail kingfish ( Seriola lalandi)

Egg-laying in Zeuxapta seriolae from the gills of yellowtail kingfish ( Seriola lalandi) in South Australia was investigated in situ under a controlled lighting schedule. Eggs were collected every 3 h from mature Z. seriolae infecting 4 S. lalandi kept individually for 7 consecutive days exposed to alternating 12 h periods of illumination and darkness (light on 06:00 h; light off 18:00 h) at 18±0.5 °C and 40 ppt salinity. A well-defined egg-laying rhythm was demonstrated for Z. seriolae. A total of 650,153 eggs was collected during all periods of illumination and darkness. Of these eggs, 71.6% (57.4–81.8%) were collected during the first 3 h period following ‘dusk’ at 18:00 h. At the conclusion of the experiment, 179 mature Z. seriolae specimens were recovered with a mean clamp number of 47 (37–53) along the major clamp row and 36 (26–44) along the minor clamp row. Of the 179 specimens examined, 177 were found with eggs in utero: mean 321, range 8–1015. Specimens of Z. seriolae produced on average 21.6 (20.8–23.8) eggs/worm/h over the 7 day experiment. It is suggested that Z. seriolae accumulates eggs in utero over a 24 h period. Eggs extracted from the uteri of worms were joined together by filamentous strands and formed a single continuous ‘egg string’. The well-defined egg-laying rhythm in Z. seriolae may be related to a specific host behaviour associated with ‘dusk’ or darkness.