Effects of traditional Chinese medicines on immunity and culturable gut microflora to Oncorhynchus masou.

The present study was conducted to evaluate the effect of dietary traditional Chinese medicines on the growth, immunity, and composition of culturable gut microflora in Oncorhynchus masou. Diets were formulated to contain no medicine (control), antitoxic decoction (A), general antiphlogistic decoction (B), or Herbae Artemisiae Capillariae decoction (C). Fish were manually fed twice daily till apparent satiation for 30 days. Compared with that in the control group, supplementation with the three kinds of Chinese herbal medicine enhanced fish growth significantly (P < 0.05). The activities of liver superoxide dismutase and glutathione peroxidase in the treatment groups were significantly higher compared with those in the control group (P < 0.05). The quantity of intestinal microflora was higher in the treatment groups compared with that in the control group. Moreover, there were some effects of dietary Chinese herbal medicine on the composition of intestinal microflora. Microflora of Pseudomonas sp., Psychrobacter sp., Microbacterium sp., Macrococcus sp., Burkholderia sp., and Arthrobacter sp. were found in the treatment groups, whereas there were none in the control group. There was a significant increase in their amounts in the treatment groups (P < 0.05). The three kinds of traditional Chinese medicines can improve the growth and immunity of Oncorhynchus masou and affect the quantity and composition of intestinal microflora.

Reproductive success, early life stage development, and survival of westslope cutthroat trout (Oncorhynchus clarki lewisi) exposed to elevated selenium in an area of active coal mining.

The effects of accumulated Se on the reproductive success and larval development of cutthroat trout (Oncorhynchus clarki lewis,) collected from a site of active coal mining in British Columbia were assessed. Eggs from 12 fish from an exposed site (Clode Pond) and 16 from a reference site (O'Rourke Lake) were field-collected and reared in the laboratory. Egg Se concentrations ranged from 12.3 to 16.7 and 11.8 to 140.0 microg/g dry weight (dw) from fish collected at the reference and exposed sites, respectively. Other studies, including those with this species, have not shown Se to affect egg viability; however, in the present study, eggs with Se concentrations > 86.3 microg/g dw were not successfully fertilized or were nonviable at fertilization, while eggs with concentrations > 46.8 and < 75.4 microg/g dw were fertilized (96% reached the eyed stage) but did not produce viable fry. A significant positive relationship between egg Se concentration and alevin mortality was observed. Deformities were analyzed in surviving fry which developed from eggs with Se concentrations between 11.8 and 20.6 microg/g dw. No relationship between Se concentration in eggs and deformities or edema was found in this range, suggesting that the no-effect threshold for deformity is > 20.6 microg/g dw. The present data, in conjunction with the data from several other studies in temperate fish, suggest that current Se thresholds are conservative for cold-water fish.

Disturbance of plasma melatonin profile by high dose melatonin administration inhibits testicular maturation of precocious male masu salmon.

We have previously shown that the testicular development of underyearling male masu salmon Oncorhynchus masou reared under a long photoperiod was accelerated by oral melatonin treatment (0.5 mg melatonin/kg body weight/day), suggesting that melatonin mediates photoperiodic signaling. In this study, we further examined the effects of a disturbance in the plasma melatonin profile on gonadal development in underyearling male masu salmon by administering a higher dose of melatonin. Fish randomly selected in June were divided into two groups. They were reared under a light:dark (LD) cycle of 16:8 (lights on 04:00-20:00 hr) and fed with pellets sprayed with melatonin or vehicle twice a day at 08:30 and at 15:30 hr (7.5 mg melatonin/kg body weight/day) until October. Fish were sampled on Day 0, 25, 60, 90 and 120. The plasma melatonin levels were high in the dark phase and low in the light phase in the control group, while they were constantly high with no significant change in the melatonin-treated group. Melatonin treatment had inhibitory effects on the gonadosomatic index and plasma testosterone levels. Pituitary salmon gonadotropin-releasing hormone content and luteinizing hormone content were significantly lower in the melatonin-treated group on Day 60 and 90, respectively. These results indicate that the plasma melatonin profile is important for mediating photoperiodic signals that regulate brain-pituitary-gonadal axis in underyearling precocious male masu salmon.