The antifouling activity of some juvenoids on three species of acorn barnacle, Balanus

Analogues of insect juvenile hormones (juvenoids) have been tested for settling inhibition of cyprids from three species of barnacle, Balanus balanoides (L.), Balanus improvisus Darwin and Balanus amphitrite Darwin. Some 3-alkoxypyridine derivatives exhibited strong activity at mg litre(-1) concentrations; 3,7-dimethyloctyl 2-methyl-5-pyridyl ether (8) gave an EC(50) of 0.006 mg litre(-1) when tested on B. balanoides. When compound 8 and similar juvenoids were incorporated into paints, test panels kept in seawater for 8 months were free of barnacles.     

Nutrient digestibilities and gut function in Atlantic salmon (Salmo salar) fed diets with cellulose or non-starch polysaccharides from soy

Duplicate groups of Atlantic salmon (Salmo salar), kept in saltwater, were fed fish meal based cold-pelleted diets where graded levels of native or extruded non-starch polysaccharides (NSP) from soybeans replaced cellulose, at a total NSP level of 100 g kg^− 1 for 28 days. The study also included a diet where defatted soybean meal (SBM) constituted the NSP at a level of 100 g kg^− 1 and a reference diet without NSP supplementation.The SBM diet resulted in a significant reduction in faecal dry matter content, apparent digestibilities of starch and organic material, and growth, and an increased faecal output of several elements (K, Na, Zn), compared to all the other diets. Morphological changes were only seen in the intestine of the fish fed the SBM, i.e. the diets holding purified soy-NSP did not induce enteritis. When compared to the diet without NSP, cellulose addition increased faecal dry matter, while inclusion of native soy-NSP reduced it. Dry matter in faeces and apparent digestibility of crude protein decreased in a linear manner, while the digestibility of starch and faecal output of K and Na increased linearly when native soy-NSP replaced graded levels of cellulose from 0 to 100 g kg^− 1 feed. When diets with 75 or 100 g kg^− 1 of native NSP and extruded soy-NSP were compared, fish fed native soy-NSP had reduced faecal dry matter, higher digestibility of starch, and increased faecal output of Cu, Fe, and K. Dry matter in faeces and faecal output of Cu was lower for the highest inclusion level, while digestibility of starch and faecal output of Mn and K were higher.In conclusion, soy-NSP was inert compared to the fish meal reference, with respect to nutrient digestibilities and intestinal pathologies, but affected faecal mineral excretion in Atlantic salmon.     

Cataract preventative role of mammalian blood meal, histidine, iron and zinc in diets for Atlantic salmon (Salmo salar L.) of different strains

In the period from winter 1996 to autumn 1999, three feeding trials were conducted to study the possible role of mammalian blood meal in preventing lens opacities in Atlantic salmon. In addition to blood meal supplemented feed, experimental diets were formulated, aiming to mimic the total concentrations of selected elements present in blood meal (BM) enriched diets; the amino acid histidine (His) and the mineral iron (Fe). In addition, these diets were supplemented with Zn. The trials included different rearing conditions, sizes and strains of Atlantic salmon; one small scale feeding experiment with pre‐smolt of Strain A in fresh water (Trial 1) and two semi large trials with sub‐yearling (S0s) and yearling (S1s) smolts of Strains A and B in seawater (Trials 2 and 3). The trials included duplicate or triplicate feeding groups and lasted 6–12 months. Standard commercial diets not supplemented with BM were used as controls. High prevalence of cataract developed over time in all three studies, with end point ranges as follows; Trial 1: 40–52 %; Trial 2: 51–83 %; Trial 3: 63–100%. The cataracts normally first appeared in the anterior and/or posterior cortical region and later affected the perinuclear region. In all the experiments, there was a significant cataract preventative effect of both the BM supplemented and experimental diets compared to the respective control diets. To some extent, cataract incidence was reduced, but primarily cataractogenesis was less severe in these groups. A concurrent positive effect on growth of both added BM and experimental diets was observed in the two seawater trials, probably related to maintaining vision and feed uptake ability. In one of the trials, there were significant differences in cataract susceptibility between the two strains, measured both as frequency and severity of cataractous changes. Our data suggest that elevated concentrations of dietary His and/or Fe mitigate cataract formation.     

Prevalence of Borrelia burgdorferi sensu lato and Anaplasma phagocytophilum in questing Ixodes ricinus ticks in relation to the density of wild cervids

Background

Borrelia burgdorferi sensu lato and Anaplasma phagocytophilum have been considered as pathogens in animals and humans. The role of wild cervids in the epidemiology is not clear. We analyzed questing Ixodes ricinus ticks collected in spring for these pathogens from sites with high (Fjelløyvær and Strøm) and low density (Tjore, Hinnebu and Jomfruland) of wild cervids to study the spread of the pathogens in questing ticks.

Methods

For detection of Anaplasma phagocytophilum a 77-bp fragment in the msp2 gene was used. Detection of Borrelia burgdorferi sensu lato was performed using the FL6 and FL7 primers according to sequences of conserved regions of the fla gene. The OspA gene located on the linear 49-kb plasmid was used as target in multiplex PCR for genotyping. Genospecies-specific primers were used in the PCR for Borrelia burgdorferi sensu stricto, B. afzelii and B. garinii.

Results

Infection rates with Borrelia spp. were significantly lower at Fjelløyvær and Strøm compared to Tjore and Hinnebu; Fjelløyvær vs. Tjore (χ² = 20.27, p < 0.0001); Fjelløyvær vs. Hinnebu (χ² = 24.04, p < 0.0001); Strøm vs. Tjore (χ² = 11.47, p = 0.0007) and Strøm vs. Hinnebu (χ² = 16.63, p < 0.0001). The Borrelia genospecies were dominated by. B. afzelii (82%) followed by B. garinii (9.7%) and B. burgdorferi sensu stricto (6.9%). B. burgdorferi s.s. was only found on the island of Jomfruland. The infection rate of Anaplasma phagocytophilum showed the following figures; Fjelløyvær vs Hinnebu (χ² = 16.27, p = 0.0001); Strøm vs. Tjore (χ² = 13.16, p = 0.0003); Strøm vs. Hinnebu (χ² = 34.71, p < 0.0001); Fjelløyvær vs. Tjore (χ² = 3.19, p = 0.0742) and Fjelløyvær vs. Støm (χ² = 5.06, p = 0.0245). Wild cervids may serve as a reservoir for A. phagocytophilum. Jomfruland, with no wild cervids but high levels of migrating birds and rodents, harboured both B. burgdorferi s.l. and A. phagocytophilum in questing I. ricinus ticks. Birds and rodents may play an important role in maintaining the pathogens on Jomfruland.

Conclusion

The high abundance of roe deer and red deer on the Norwegian islands of Fjelløyvær and Strøm may reduce the infection rate of Borrelia burgdorferi sensu lato in host seeking Ixodes ricinus, in contrast to mainland sites at Hinnebu and Tjore with moderate abundance of wild cervids. The infection rate of Anaplasma phagocytophilum showed the opposite result with a high prevalence in questing ticks in localities with a high density of wild cervids compared to localities with lower density.     

Water flow and diurnal variation in metabolite production rates of Atlantic salmon (Salmo salar L.) post‐smolt

Diurnal variation of carbon dioxide (CO₂) and total ammonia production in Atlantic salmon post‐smolt were studied at different water flow rates. The experiment comprised four groups each with two replicates representing specific flow levels of 0.5, 0.4, 0.3 and 0.2 L kg^?1 min^?1. During the first diurnal cycle, the seawater samples were collected eight times during 21 hr. In the second diurnal cycle, six samplings were performed during a prolonged sampling period of 35 hr. The highest CO₂ concentrations were observed in the lowest water flow group (0.2 L kg^?1 min^?1) between 4 and 10 p.m. for the first sampling period and at about 2 p.m. for the second sampling period. The overall real CO₂ production rates were in the range 1.7–5.5 mg kg^?1 min^?1 including diurnal variation in all groups for both sampling periods. In general, a second‐order polynomial model describes the relationship between specific water flow and real mean CO₂ production rate (p < 0.001). Maximum concentrations of total ammonia nitrogen (TAN) occurred around 7 and 8 p.m. in all groups and was highest for the 0.2 L kg^?1 min^?1 group for both sampling periods. Note that maximum concentration of TAN and CO₂ both occurred in the afternoon. The TAN production rates were in the range 0.06–0.44 mg kg^?1 min^?1 including both sampling cycles.     

Salmonid alphavirus (SAV) and pancreas disease (PD) in Atlantic salmon,Salmo salar L., in freshwater and seawater sites in Norway from 2006 to 2008

A cohort study was initiated in the spring of 2006 to investigate epidemiological aspects and pathogenesis of salmonid alphavirus (SAV) subtype 3 infections and pancreas disease (PD). The aims were to assess involvement of the freshwater production phase, the extent and frequency of subclinical infections and to follow PD‐affected populations throughout the entire seawater production cycle, as well as investigate possible risk factors for PD outbreaks. Fish groups from 46 different Atlantic salmon freshwater sites in six counties were sampled once prior to seawater transfer and followed onto their seawater sites. A total of 51 Atlantic salmon seawater sites were included, and fish groups were sampled three times during the seawater production phase. SAV subtype 3 was not identified by real‐time RT‐PCR from samples collected in the freshwater phase, nor were any SAV‐neutralizing antibodies or histopathological changes consistent with PD. In the seawater phase, SAV was detected in samples from 23 of 36 (63.9%) studied sites located within the endemic region. No SAV subtype 3 was detected in samples from seawater sites located outside the endemic region. The cumulative incidence of PD during the production cycle amongst sites with SAV detected was 87% (20 of 23 sites). Average fish weight at time of PD diagnosis ranged from 461 to 5978 g, because of a wide variation in the timing of disease occurrence throughout the production cycle. Mortality levels following a PD diagnosis varied greatly between populations. The mean percentage mortality was 6.9% (±7.06) (range 0.7–26.9), while the mean duration of increased mortality following PD diagnosis was 2.8 months (±1.11) (range 1–6).     

Pancreas disease (PD) in sea‐reared Atlantic salmon,Salmo salar L., in Norway; a prospective,longitudinal study of disease development and agreement between diagnostic test results

A prospective longitudinal study was performed on three cages at each of three Norwegian Atlantic salmon seawater sites that experienced outbreaks of pancreas disease (PD). Once salmonid alphavirus (SAV) ribonucleic acid (RNA) was detected by real‐time RT‐PCR (Rt RT‐PCR) at a site, it became detected in all studied cages and was persistently found until the end of the study period up to 19 months after first detection. SAV‐specific antibodies were detected at all sites until the end of the study period and were also found at a high prevalence in broodfish at the time of stripping. No evidence of increased viral activity was detected in these broodfish. One site tested negative over several months prior to the first detection of SAV by Rt RT‐PCR and SAV‐specific antibody, which occurred 1 month prior to clinical manifestations of PD. Moribund fish or thin fish/runts that were sampled after the first PD diagnosis had almost twice the risk of testing positive by one or more diagnostic tests compared to that of randomly selected apparently healthy individuals. This paper describes the first detailed investigation of the disease development of PD at site and cage level in Norway, as well as an assessment of the performance and agreement of the commonly used diagnostic tests.