Distributions of planktonic sea lice larvae Lepeophtheirus salmonis in the inter-tidal zone in Loch Torridon, Western Scotland in relation to salmon farm production cycles   总被引：2，自引：0，他引：2  

Margaret A McKibben  & David W Hay 《Aquaculture Research》2004,35(8):742-750

This study examines the relative density of sea lice, Lepeophtheirus salmonis (Krøyer), larvae in the inter‐tidal areas of Loch Torridon, a fjordic sea loch in Western Scotland and the site of several commercial salmon farms. Samples of planktonic sea lice were collected in each spring from 1999 to 2003 near the mouth of the River Shieldaig, where sea trout have been shown to congregate in the first few days after going to sea, and from 2001 to 2003 near the mouth of the River Balgy. No larval sea lice were found near the mouth of the River Shieldaig in spring 2000 or 2002, when gravid female sea lice were absent on local fish farms. The same finding was observed in 2002 at the mouth of the River Balgy. In springs of 1999, 2001 and 2003, peak densities of larval sea lice of 33, 94 and 143 m^?3, respectively, were observed at the mouth of the river Shieldaig. At the mouth of the River Balgy, peak densities of 74 and 78 lice m^?3 were observed in 2001 and 2003 respectively. At the time these samples were collected, the two local salmon farms were in the second year of their production cycle and gravid female sea lice were present. Samples of larval sea lice were also obtained year round, at approximately weekly intervals, from a 50‐m transect at the mouth of the River Shieldaig, from March 2001 to June 2003, and compared with frequencies of gravid female sea lice on the two local salmon farms. High levels were found in the winter. No planktonic sea lice were found in this transect when gravid females were not present on the local fish farms.  相似文献   

Observations on open-water densities of sea lice larvae in Loch Shieldaig, Western Scotland   总被引：4，自引：0，他引：4  

Michael J Penston  Margaret A McKibben  David W Hay  & Philip A Gillibrand 《Aquaculture Research》2004,35(8):793-805

Sea trout (Salmo trutta L.) stocks on the West Coast of Scotland and Ireland have decreased due to reduced survival during the marine phase of their life cycle. Lice‐infested sea trout returning to rivers could indicate that parasite burdens are contributing to the decline. Salmon farms represent a potential source of substantial quantities of sea lice, leading to a conjectured link between parasites on salmon fish farms and infestations on wild sea trout. To investigate the potential infective pressure on sea trout in Loch Shieldaig, offshore and sub‐littoral plankton samples were collected and analysed for sea lice nauplius and copepodid stages. During the plankton survey, numbers of sea lice on a fish farm in the loch reached a maximum in November 2001. Soon after, numbers of sea lice larvae peaked in open‐water samples and then in sub‐littoral samples. Nauplii were found adjacent to the farm and occurred less elsewhere. This study reports a concentration of sea lice larvae at the head of Loch Shieldaig and indicates a possible relationship between sea lice numbers on the fish farm and lice larvae densities in the open‐water of the loch and in the sub‐littoral zone.  相似文献   

Studies on the use of hydrogen peroxide as a method for the control of sea lice on Atlantic salmon     

D. W. Bruno  R. S. Raynard 《Aquaculture International》1994,2(1):10-18

Atlantic salmon (Salmo salar) post-smolts exposed to 1.23 hydrogen peroxide for 20 min at 13.5 C suffered an acute toxicity resulting in a 35% mortality within 2 h. Under similar conditions at 10 C no mortalities were observed with Atlantic salmon or goldsinny wrasse (Ctenolabrus rupestris). No histological changes were noted in tissues from exposed fish. Thirty-three per cent of adult and pre-adult sea lice (Lepeophtheirus salmonis) were immobilized or killed following exposure to 0.5 hydrogen peroxide at 10 C, rising to 98% at 2. Some lice were able to recover and regained normal swimming movements. Gas bubbles within the haemolymph caused affected lice to float on the water surface. A delay in the toxicity of hydrogen peroxide to copepodites occurred, with a 10% mortality following a 20 min exposure to 1.25 at 10 C rising to 100% mortality at 19 h post treatment.Dilute hydrogen peroxide was stable over the 20 min treatment period. Aeration and higher temperatures increased the long-term breakdown of a working concentration of hydrogen peroxide in seawater.  相似文献   

The development of pyrethrum-based treatments against the ectoparasitic salmon lice Lepeophtheirus salmonis in sea cage rearing of atlantic salmon Salmo salar L.     

Karin Boxaspen  & Jens Christian Holm 《Aquaculture Research》2001,32(9):701-707

Motile salmon lice Lepeophtheirus salmonis were successfully removed by an oil-based pyrethrum treatment mixture. The experiments described here are all based on skin exposure of the salmon Salmo salar L. The in-cage method, in which salmon would delouse themselves by jumping through a layer of treatment mixture, gave up to 86.9% delousing effect under low levels of solar radiation (October). However, at higher levels of radiation (May), the comparable effect decreased to 31.8%. Studies of exposure time vs. delousing effect showed no difference between 2-s and 10-s exposure and gave an overall delousing effect of 89.5%. Individual delousing procedures have thus been developed with a 4- to 6-s dip in the pyrethrum treatment mixture. A commercial method is described based on commercial Py-Sal 25 mixed with an anaesthetic bath before a vaccination or sorting operation. The overall delousing efficiency with this large-scale method was 85%. This is the method now used in commercial delousing with pyrethrum as the active component.  相似文献   

2006年江苏盐城水稻褐飞虱的发生及防治   总被引：1，自引：0，他引：1  

陈元洲  仇学平  曹方元  茅永琴  宋巧凤 《金陵科技学院学报》2007,23(2):65-67

2006年江苏省盐城褐飞虱大暴发,是近10年来最重的1年,表现出:迁入期早,峰次多,迁入量大,田间虫量高,三、四代连续大发生,危害时间长等特点,对水稻产量造成了严重影响。在防治方面,按照统防统治的原则,采取“压前控后”与“狠治主害代”的防治策略,取得了很好的防治效果。  相似文献   

Susceptibility,behaviour, and retention of the parasitic salmon louse (Lepeophtheirus salmonis) differ with Atlantic salmon population origin          下载免费PDF全文

S Bui  S Dalvin  T Dempster  O F Skulstad  R B Edvardsen  A Wargelius  F Oppedal 《Journal of fish diseases》2018,41(3):431-442

Atlantic salmon populations across the world have diverse ecological and evolutionary histories, from wild anadromous or landlocked, to domestication and genetic modification. The natural host behaviours confer protection from infestation by ectoparasitic salmon lice Lepeophtheirus salmonis, yet whether genetic origin results in different behaviours and thus susceptibility to infestation is unknown. In common garden experiments, we tested antiparasite behaviours, susceptibility and retention of salmon lice in wild anadromous, wild landlocked, domesticated and genetically modified domesticated strains. Within domesticated strains, we tested two infestation histories (previously infested and naïve) and a new phenotype (albino colouring). Farmed stocks initially acquired 24%–44% higher levels of parasite density than the wild and landlocked strains. Burst swimming and displacement behaviours were higher in the domesticated groups, and jumping was more prevalent in the domesticated strains. At 34 days post‐infestation, domesticated strains and the wild anadromous strain did not differ significantly from each other; however, landlocked salmon had increased infestation levels considerably. Domesticated strains lost ~20% (±9.9%–16.5%; 95% CI) of their initial parasite load, while parasite load increased by 5.5% (±30.1%) for wild salmon and 20.1% (±28.5%) in landlocked salmon. This study provides early evidence for diverged host–parasite interactions associated with domestication in this system.  相似文献   

An improved in vitro rearing system for the human head louse allows the determination of resistance to formulated pediculicides     

Kyong Sup Yoon  Jian-Rong Gao  Miwako Takano-Lee  J. Marshall Clark 《Pesticide biochemistry and physiology》2006,86(3):195-202

An improved in vitro rearing system, based on a silicone-reinforced Parafilm^® M membrane, human hair tufts and reconstituted human blood, enabled the large-scale rearing of pediculicide-susceptible (EC-HL) and resistant (SF-HL and BR-HL) strains of human head lice. Developmental time differed for early instars but differences became synchronized as lice matured. Mean survivorship amongst the three strains reared in vitro were not significantly different when compared to EC-HL and SF-HL reared in vivo. The efficacies of three pediculicidal products were assessed under semi-clinical conditions using a modified version of the in vitro rearing system. Treatments of 1% permethrin in acetone, Nix^®, Rid^® or Pronto^® Plus to hair tufts following manufacturer’s instructions were highly efficacious (100% mortality) on EC-HL but differentially efficacious (62.2-84.4% mortality) on SF-HL examined eight days post-treatment. SF-HL that survived the first treatment received an identical second treatment eight days following the first treatment. Survivors (13.3-30.0%) developed to adults (10th-11th day following first treatment) and females successfully laid fertile eggs that developed to first instars. These results confirm resistance to permethrin- and pyrethrin-based pediculicide formulations in SF-HL when assessed under semi-clinical conditions and validates resistance previously determined using filter-paper contact bioassays and unformulated insecticides.  相似文献   

Morphology of the leather defect light flecks and spots.     

O Nafstad  H Wisl?ff  H Gr?nst?l 《Acta veterinaria Scandinavica》2001,42(1):107-112

The skin histology and the scanning electron microscope morphology of the hide defect light flecks and spots after tanning were studied in 11 steers infested with biting lice (Damalinia bovis). Nine steers from herds free of lice were used as controls. Skin biopsies from 6 of the animals in the lice infested group showed mild to moderate hyperkeratosis and moderate perivascular to diffuse dermatitis with infiltration of mainly mononuclear cells and some eosinophilic granulocytes. The steers were slaughtered at an age of 18 to 23 months. Light flecks and spots occurred on all examined hides from the infested group after tanning. No examined hides from the control group demonstrated similar damage. Both light microscopic examination of sections of tanned hide with light flecks and spots and scanning electron microscopy of the same defects showed superficial grain loss and craters with a irregular fibre base encircled by smooth and intact grain. The association between louse infestation at an early age and damage of hides following slaughter 6 to 15 months later, suggested that louse infestations lead to a prolonged or lifelong weakening in the dermis. This weakening may cause superficial grain loss during the tanning process.  相似文献   

Tissue distribution of 14C-diflubenzuron in Atlantic salmon (Salmo salar)     

Tor Einar Horsberg  Tonje Hy 《Acta veterinaria Scandinavica》1991,32(4):527-533

Diflubenzuron is a potent inhibitor of chitin synthesis, with potential use against salmon lice infestations. The absorption, distribution and elimination of the substance in Atlantic salmon was examined after a single, oral dose of 75 mg/kg bodyweight. The kinetic properties were studied by whole-body autoradiography, liquid scintillation counting and thin layer chromatography, using a 14C-labelled isotope of the substance. The drug was poorly absorbed from the intestine, but reached a concentration of more than 4 micrograms/g in the mucus layer of the skin 2 days after administration. If maintained for several days, this concentration is probably sufficient to control all moulting stages of sea lice in Atlantic salmon. The main route of excretion was via the bile.  相似文献   

Essential oils in the management of the donkey louse,Bovicola ocellatus          下载免费PDF全文

L. Ellse  B. Sands  F. A. Burden  R. Wall 《Equine veterinary journal》2016,48(3):285-289

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