An evaluation of the duration of efficacy of emamectin benzoate in the control of Caligus curtus Müller infestations in Atlantic cod, Gadus morhua L

The duration of efficacy of emamectin benzoate in the control of Caligus curtus infestations in Atlantic cod, Gadus morhua L., was studied following an administration of 50 μg kg^?1 for seven consecutive days. No lice were found on medicated fish when challenged 1 week (challenge 1) or 5 weeks (challenge 2) following termination of medication, whereas the mean abundance of lice among the unmedicated fish was 17.9 and 19.3 lice per fish in challenge 1 and 2, respectively. Muscle concentrations of 19.5 ± 8.2 ng g^?1 and 3.4 ± 0.9 ng g^?1, respectively, and skin concentrations of 23.1 ± 10.8 and 4.2 ± 1.0 ng g^?1, respectively, were found 27 and 55 days following the termination of medication. Tissue concentrations and the duration of efficacy indicate a dosing regime for emamectin in cod, similar to the regime used for Atlantic salmon, Salmo salar L.     

Investigation of the Protective Effect of β-carotene in the Prevention of Lipid and Protein Oxidation in Carp Meat during Different Storage Times

ABSTRACT

This study was aimed to investigate the effects of dietary β-carotene supplement for 42 days on lipid and protein oxidation biomarkers in carp meat at different times of storage. Seventy-five fish were divided into three groups: group 1 as control group was fed with basic diet; groups 2 and 3 received 50 and 100 mg kg^?1 diet β-carotene, respectively. Based on the present study results, muscle malondialdehyde concentrations were significantly lower following β-carotene consumption at 0, 24, 72, and 96 h after harvest in group 3 compared to the control group (p < 0/05). Muscle protein carbonyl contents showed a significant decrease following β-carotene supplementation at 0, 48, and 96 h after harvest in group 3 compared to the control group. Ferric reducing antioxidant power values were significantly increased following β-carotene supplementation at 72 and 96 h after harvest in group 3 compared to the control group. The results indicated that β-carotene supplementation with a dose of 100 mg kg^?1 diet is largely effective to improve the oxidative status of carp meat by reducing lipid and protein oxidation.     

Numerical simulation of circulation in the Laizhou Bay

IntroductionAs part of the Bei Dou Fisheries Research and Managements project(1997- 2 0 0 0 ) ,the Institute of MarineResearch participated in a collaborative study with the Yellow Seas Fisheries Institute on approaches to thedevelopment of theoretical models as tools for assessing the carrying capacity of bivalve production.The In-stitute of Marine Research has in recent years engaged in relatively extensive activity on numerical modellingof coastal oceans. To demonstrate some of the po…     

Changes in the distribution of Atlantic cod (Gadus morhua) in the southern Gulf of St Lawrence — effects of environmental change or change in environmental preferences?

Density-independent redistribution in response to changing temperature conditions and density-dependent redistribution in response to changing temperature preferences are two contrasting hypotheses to explain changes in the distribution of cod populations. I tested these hypotheses using survey data on the distribution of cod during the feeding season in the southern Gulf of St Lawrence. These tests used indices of cod distribution as the dependent variable and indices of cod abundance and bottom temperature as explanatory variables. Both hypotheses were often supported in univariate tests that ignored confounding between the two explanatory variables. Tests that accounted for this confounding indicated an effect of cod abundance on distribution for ages 4–8⁺ years, and 3⁺, but provided no support for an effect of environmental conditions on distribution except for age 3. Variation in the temperature distribution of cod was consistent with an effect of abundance on interannual variation in distribution and with no effect of environment except for age 3 cod. Age 3 cod were consistently under-represented in areas of very cold bottom water but older cod were not. As predicted by bioenergetic considerations, cod tended to occupy colder water at high levels of abundance, suggesting a mechanism for density-dependent shifts in distribution. Shifts in cod distribution during the feeding season in the southern Gulf appear to be more closely linked to density-dependent changes in environmental preferences than to density-independent responses to changing environmental conditions.     

Antiparasitic efficacy of dietary administration of trichlorfon (Masoten®) in the control of Neoechinorhynchus buttnerae (Neochinorhynchidae) in Colossoma macropomum (Serrasalmidae)

Aquaculture International - This study investigated the efficacy of trichlorfon against Neoechinorhynchus buttnerae, as well as its palatability, residue analysis, and the blood parameters of...     

Socio-cultural context of fishers’ participation in coastal resources management in Anini-y,Antique in west central Philippines

The vicious cycle of poverty, overfishing and resource degradation in coastal communities in the Philippines calls for action that will address the problem of declining fish catch and degraded fish habitats. The literature has shown that an efficient and effective coastal management program can be instrumental in approaching this problem. In order to secure food and livelihood of fishers, the Southeast Asian Fisheries Development Center/Aquaculture Department collaborated with the local government of Anini-y, Antique to develop a sustainable utilization of natural marine resources through sea ranching of abalone within the Nogas Island marine protected area. Establishing a marine protected area is a means of conserving natural stocks while sea ranching is considered an effective strategy that can increase fishery resources. The two management schemes are considered as effective coastal resources management strategies. The success of a sea-ranching project is dependent not only on biophysical but also on socioeconomic factors as determinants of community participation and cooperation. A social assessment was conducted to determine the fishers’ socio-cultural characteristics, their perceptions of their coastal resources and knowledge on how to effectively manage these coastal resources. The fishers’ awareness on fishing regulations and the extent of their participation in community's coastal resources management activities were also determined. Data were collected from a household survey using a semi-structured questionnaire, focus group discussions and in-depth interviews with key informants. The fishers generally scored low in almost all aspects of their socioeconomic wellbeing. Most fishers perceived that their coastal resources were in a bad condition which they attributed to illegal and commercial fishing, increasing number of fishers and the poor enforcement of fishery regulations. However, the weighted mean scores of their knowledge on coastal resources management, awareness to fishery regulations and participation in community coastal resource management activities were average. This implied that fishers when trained and developed can become potential partners for effective coastal resources management programs.     

Variation in content of Ω3 fatty acids in farmed Atlantic salmon,with special emphasis on effects of non-dietary factors

The main aim of the present study was to examine the impact of some biological and environmental factors on the lipid and fatty acid compositions of farmed Atlantic salmon (Salmo salar), with special emphasis on 3 fatty acids. Two year groups of salmon at nine fish farms distributed along the Norwegian coast were fed the same diet and were sampled every second month. The data are believed to give a representative characterization of lipid and fatty acid content of salmon farmed in Norway.Multiple regression analysis revealed that variation in lipid content and body weight explained 80% of the variation found in 3 fatty acids in farmed salmon, and 22:6 3 showed greater variation than other 3 fatty acids. Further analysis of lipid-corrected values revealed only minor effects of latitude on the per cent content of highly unsaturated 3 fatty acids, and hardly any effect of seawater temperature, with the exception of 22:6 3, which decreased slightly with increasing temperature.The per cent 22:6 3 in the fillet became gradually reduced with increasing fish age and body weight, whereas the content of 20:5 3 and other 3 fatty acids remained relatively constant. The per cent content of 22:6 3 of young salmon was higher than in the feed, but approached the feed value gradually as body weight increased. The lipid content of the salmon increased with fish age, and the absolute quantitative contents of both 22:6 3 and 20:5 3 increased meanwhile, even though the per cent content of 22:6 3 decreased quite pronouncedly.The per cent 22:6 3 and other 3 fatty acids was higher in wild than in farmed salmon, but the absolute quantitative content was higher throughout in farmed salmon, which had higher lipid contents. The 3/6 ratio, which is important in human health evaluation, was lower in farmed than in wild salmon. The large flexibility of 3 fatty acids and lipid content of farmed salmon leave us with the option of producing a wide variety of salmon qualities requested by the market. Both per cent and absolute quantitative 3 contents, as well as the 3/6 ratio, may readily be manipulated.     

Development of Cre–loxP technology in zebrafish to study the regulation of fish reproduction

One cannot seek permission to market transgenic fish mainly because there is no field test or any basic research on technological developments for evaluating their biosafety. Infertility is a necessary adjunct to exploiting transgenic fish unless completely secure land-locked facilities are available. In this study, we report the generation of a Cre transgenic zebrafish line using a cytomegalovirus promoter. We also produced fish carrying the Bax1 and Bax2 plasmids; these genes were separated by two loxP sites under a zona pellucida C promoter or were driven by an anti-Müllerian hormone promoter. We inserted a red fluorescent protein gene between the two loxP sites. After obtaining transgenic lines with the two transgenic fish crossed with each other (Cre transgenic zebrafish x loxP transgenic zebrafish), the floxed DNA was found to be specifically eliminated from the female or male zebrafish, and apoptosis gene expressions caused ovarian and testicular growth cessation and degeneration. Overexpression of the Bax1 and Bax2 genes caused various expression levels of apoptosis-related genes. Accordingly, this transgenic zebrafish model system provides a method to produce infertile fish and may be useful for application to genetically modified fish.     

Identification of métiers of the Spanish set-longline fleet operating in non-Spanish European waters

The Spanish set-longline fleet operating in ICES Subareas VI, VII and Divisions VIIIabd is composed of two fleet segments distinguished according to tonnage: vessels larger and shorter than 100 grt. Spanish regulations allow Spanish-registered longliners fishing in European waters to prosecute three different types of fisheries, namely targeting hake, targeting non-TAC species and targeting deepwater species. Due to the fact that the type of license is not registered in logbooks, together with the recent changes in the regulation of fishing on some non-TAC and deepwater species, conducting multivariate analyses of landing profiles at species level becomes the most appropriate way to identify fisheries and métiers. A 3-step approach was used, consisting of clustering of landings profiles (2004–2006), interviews with skippers by group, and an exploration of the spatial–temporal patterns in both sources of information. The results obtained allowed us to identify eight fisheries. Of these, four fisheries were common to both fleet segment giving eight métiers: directed at hake, forkbeards, lings, and conger. Of the remaining four métiers, the mixed métier developed by vessels shorter than 100 grt occurred throughout the period studied, while the remaining three métiers showed discontinuous patterns and were directed at bluemouth, Atlantic pomfret, and deepwater sharks, respectively. The two first métiers appeared in 2006, while the last one was found to occur during 2004–2005 but disappeared in 2006. The obtained results allow us to match the Spanish fishing license system with the métiers classification used by the Common DCF (data collection framework) taking into account the current categorization of species in regulations.     

Liquid-chromatographic hybrid triple–quadrupole linear-ion-trap MS/MS analysis of fatty-acid esters of dinophysistoxin-1 in bivalves and toxic dinoflagellates in Japan

Fatty-acid esters of dinophysistoxin-1 (DTX1) in scallops Patinopecten yessoensis, mussels Mytilus coruscus, and toxic dinoflagellate Dinophysis species, collected from Japanese seawater, were analyzed by liquid-chromatography mass spectrometry (LC–MS). Precursor ion monitoring, multiple reaction monitoring for 18 fatty-acid esters of DTX1, and full-scan MS/MS spectra obtained with a hybrid triple–quadrupole linear-ion-trap mass spectrometer showed that 14:0, 16:0, and 16:1 esters were the most abundant 7-O-acyl-DTX1 analogues in bivalves. Fatty-acids esters formed by conjugations at hydroxyl positions other than the 7-position of DTX1 were not detected in the bivalves. DTX1 and okadaic acid-16:0 fatty-acid esters have been reported as the most abundant ester in bivalves in several previous studies; however, we found that 7-O-16:1-DTX1 was the most abundant ester in some mussels in which 16:1 was more dominant than 16:0 in the free fatty-acid profile. Comparison between 7-O-acyl-DTX1 and free fatty-acid profiles in the same bivalve samples suggests that polyunsaturated fatty acids are selectively excluded in enzymatic acylation of DTX1. No 7-O-acyl-DTX1 was detected in any single-cell isolates of D. fortii, D. acuminata, D. mitra, D. norvegica, D. tripos, D. infundibulus, and D. rotundata.     

Trends in import and export of fishery products in the Czech Republic during 2010–2015

There has been a worldwide increase in consumption of fish from open waters and aquaculture during the last decades. In 2013, the Czech Republic was the sixth largest producer of fish within the EU, with annual production of 20,135 tonnes. However, during the period 2010–2015 import of fishery products to the Czech Republic increased from 39,098 to 43,399 tonnes. The monetary value of import increased by 81 % from 90.2 million EUR in 2010 to 169.9 million EUR in 2015. In 2010, the major imported fishery product was frozen fillets of sutchi catfish (Pangasianodon hypophthalmus) from Vietnam (8872 tonnes). In 2015, the most imported fishery product was whole chilled salmon (Salmo salar) from Norway (6897 tonnes). During 2010–2015, the export of fishery products increased from 18,167 to 22,134 tonnes, which is an increase by 21.8 %. The value of export has increased by 80 % from 54.5 million EUR in 2010 to 98.1 million EUR in 2015. The major exported fish was live common carp (Cyprinus carpio) at volume of 7545–9075 tonnes. This study looks at changes in market, volume and value of fish imported and exported during the last 6 years.     

Synthesis and regulation of 17α-hydroxy-20β-dihydroprogesterone in immature males of Oncorhynchus mykiss

Three experimental approaches were chosen to study the question if the progestin 17-hydroxy-20-dihydroprogesterone (1720OHP) is synthesised in testes of young Oncorhynchus mykiss, in which the absence of spermatozoa was verified histologically: first, in order to detect 20-hydroxysteroid dehydrogenase activity (20HSD), testes homogenates were incubated with ³H-labeled 17OHP.Metabolites were analysed by TLC, HPLC, and repeated crystallization to constant isotope ratios. One of the metabolites was identified as 1720OHP-³H, indicating that already immature testes contain 20HSD activity and are able to produce 20-reduced steroids. Second, 1720OHP was quantified by radioimmunoassay in incubates of testes fragments. The sensitivity of the gonads to gonadotropin II (GtH II) became evident when comparing incubations in the absence and presence of GtH II. Third, plasma levels of 1720OHP were significantly higher in animals injected with partially purified salmon gonadotropin, compared to controls. Thus, for the first time, it could be shown that 20HSD is present in testicular cells other than spermatozoa. Furthermore, 1720OHP is indeed secreted at a very early stage of testicular development; 1720OHP secretion is also responsive to GtH II. Future studies will have to show if the functions of this progestin include the stimulation of spermatogenesis.     

What are the drivers of the occurrence of illegal fishing and conservation barriers of sturgeons in the Caspian Sea?

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Regulation of oocyte maturation in the rainbow trout,Salmo gairdneri: role of cyclic AMP in the mechanism of action of the maturation inducing steroid (MIS), 17α-hydroxy, 20β-dihydroprogesterone

In fish, oocyte maturation (resumption of meiosis after completion of vitellogenesis and before ovulation) is triggered by maturation inducing steroids (MIS) which generally appear to be secreted in the ovary in response to stimulation by a pituitary maturational gonadotropin. Converging data from different laboratories show that 17-hydroxy, 20-dihydroprogesterone (17, 20-OH-P) is the principal MIS in salmonoids; but clear identification remains to be done in other taxonomic groups.The experiments reported here in the rainbow troutSalmo gairdneri examine the possible involvement of oocyte cAMP on the mechanism of MIS action. The action of 17, 20-OH-P, on germinal vesicle breakdown (GVBD) in oocytes incubatedin vitro within the follicle, was inhibited by various substances expected to elevate the intraoocyte concentrations of cAMP: cAMP ( 1 mM) or dibutyril cAMP ( 2 mM), phosphodiesterase inhibitors such as theophylline ( 0.2 mM) or 3-isobutyl-1 methylxanthine (IBMX 0.1 mM), adenylate cyclase activators such as cholera toxin (> 100 nM) or forskolin ( 0.03 mM). In fact, the combined action of IBMX (1 mM) and forskolin (0.01 or 0.05 mM)in vitro was to promote accumulation of intraoocyte cAMP within 1 to 5 hours. Oocyte cAMP concentrations exhibited a large variability between different females, depending on the stage of oocyte development; a significant positive correlation between oocyte cAMP concentration and the follicular weight, and a significant negative correlation between oocyte cAMP concentration and the median efficient dose of 17, 20-OH-P for induction of GVBD, were observed. Finally, when intrafollicular oocytes were incubatedin vitro, the addition of a maturation-inducing concentration of 17, 20-OH-P (3×10^–6M) induced a significant decrease of oocyte cAMP within the first 10 hours of incubation. These results show that cAMP appears to play a central role in the regulation of oocyte sensitivity to 17, 20-OH-P and in the intraoocyte mechanisms leading to GVBD in trout.These data are discussed together with the few indications available in fish concerning the mechanism of MIS action which can be compared to some extent with the amphibian model.     

What can be expected of a T90 extension piece to improve selectivity in bottom trawl multispecific fisheries in the Bay of Biscay?

In the Bay of Biscay, the selective properties of otter trawls have mainly been studied with regard to single species. However, for bottom trawl multispecific fisheries targeting fish, it remains challenging to find a selective device capable of limiting catches of small individuals of several species without commercial losses. The present study focuses on an innovative technical solution to reduce catches of undersized individuals in a multispecies bottom trawl fishery in the Bay of Biscay. We tested a cylinder made of 100-mm diamond meshes turned at 90°, namely T90 inserted in the extension piece. We present the selectivity results obtained for six commercial species. This device allows the escape of small Solea solea, Trachurus trachurus and Spondyliosoma cantharus individuals. No commercial losses of Sepia officinalis were recorded. Patterns for Dicentrarchus labrax and Mullus surmuletus require further investigation due to limited fish size ranges in the dataset.     

Potential of nutrient reutilisation in combined intensive–extensive pond systems

The experiments on the intensive–extensive system were carried out between 2008 and 2010 in three ponds (area 310 m², depth 1 m) serving as extensive units, where cages were placed as an intensive units (volume 10 m³) one in each pond. In the intensive units, African catfish (Clarias gariepinus) was cultured and fed with pellet whilst common carp (Cyprinus carpio) was stocked in each extensive unit and raised without any artificial feeding. Three different setups of extensive ponds were tested: the additional artificial plastic substrate for periphyton development equalled to 0, 100 and 200 % of the pond surface area (PP0 %, PP100 % and PP200 %) at feed loading level of 1.2, 1.9 and 2.8 gN m^?2 day^?1 in 2008, 2009 and 2010, respectively. The additional net fish yields in the extensive unit were 2.8–6.5 t ha^?1 in PP0 %, 5.1–8.1 t ha^?1 in PP100 % and 2.1–4.3 t ha^?1 in PP200 %. The nitrogen recovery in the additional fish yields of extensive ponds, expressed as the percentage of feed load, was 5.6–6.1, 6.8–10 and 2.1–6.1 % in the treatments PP0 %, PP100 % and PP200 %, respectively. The combined fish production resulted in higher protein utilisation by 22–26 %; even this ratio can be increased by 33–45 % with periphyton application.     

Food-deprivation-induced suppression of pituitary–testicular-axis in the tilapia Oreochromis mossambicus

In the present study, the tilapia Oreochromis mossambicus were exposed to food deprivation for a period of 6 or 12 days and changes in the luteinizing hormone (LH) immunoreactivity in the proximal pars distalis (PPD) of the pituitary gland and the testicular activity were examined. Intensely immunoreactive LH content was noticed in the PPD of the pituitary gland in the initial controls, controls on days 6 and 12, and fasting fish on day 6, whereas the LH immunoreactivity was moderate or weak in fasting fish on day 12. In addition, although the mean gonadosomatic and hepatosomatic indices among different experimental groups did not show any statistically significant difference, the mean numbers of spermatogonia, spermatocytes, and spermatids were significantly lower in food-deprived fish on days 6 or 12 compared to those of controls. The inhibition of the spermatogenesis was accompanied by the presence of abundant spermatozoa in the lumen of seminiferous tubules of the testis in food-deprived fish, whereas the occurrence of spermatozoa was relatively infrequent in initial controls and controls. Furthermore, refeeding to food-deprived fish on day 6 onwards resulted in occurrence of few intensely stained LH secreting cells and significantly higher numbers of spermatocytes and spermatids concomitant with sparse spermatozoa in majority of tubules compared to those of food-deprived fish. These results suggest that prolonged exposure to food-deprivation causes suppression of the LH secretory activity in the pituitary gland and disruption in the spermatogenesis in O. mossambicus.

     

Is the decline of freshwater mussel populations in a regulated coastal river in south‐eastern Australia linked with human modification of habitat?

• 1. The Hawkesbury‐Nepean River provides potable water for 5 million people living in the Sydney basin, and water for agricultural and horticultural production that meets most of Sydney's daily needs for fresh food. Anecdotal evidence indicated that numbers of freshwater mussels have seriously declined in much of the river over recent decades.
• 2. A field survey revealed the presence of populations of three species of mussels, Hyridella depressa, Hyridella australis and Velesunio ambiguus in the river. Higher density mussel populations were most common in catchment areas with little human modification to the channel bed or adjacent vegetation communities.
• 3. Levels of disturbance of riparian vegetation and, to a lesser degree, land use, were identified as being strongly associated with the absence of mussels from some reaches.
• 4. Catchment geomorphology was also shown to be relevant to the abundance, population structure and suite of mussel species present in different geomorphic reaches of the river. Absence of mussels was noted from areas where they had been recorded in previous studies. These results demonstrate that mussel species are under threat in the catchment.
• 5. As filter feeders with the ability to remove excess nutrients and bioaccumulate toxic substances, freshwater mussels play an important role in natural remediation processes in freshwater systems.
• 6. The decline in mussel populations in the Hawkesbury‐Nepean River highlights concerns for the overall health of the river system, and supports the need to identify the subsidiary impacts of physical habitat modification in developing both riverine and riparian management strategies.

Copyright © 2006 John Wiley & Sons, Ltd.