The growth and reproductive endocrinology of adult triploid Pacific salmonids

This paper describes the effect of triploidy on growth and reproductive endocrinology in the months leading up to and including spawning in rainbow trout,Salmo gairdneri, and pink salmon,Oncorhynchus gorbuscha. Growth rates were the same for diploid and triploid rainbow trout, but triploid female pink salmon were smaller than maturing diploid females and diploid and triploid males of the same age. Triploid males of both species developed typical secondary sexual characteristics and had normal endocrine profiles, although their cycle appeared to be delayed by about one month. Triploid females remained silvery in appearance and showed no endocrine signs of maturation, even at the level of the pituitary. Thus, although triploids of both sexes are genetically sterile, only the females do not undergo physiological maturation.Reported in part at the Third International Symposium on Reproductive Physiology of Fish, St. John's, Newfoundland, August 2–7, 1987.     

Diurnal variation in thermal environment experienced by salmonids in the North Pacific as indicated by data storage tags

Eight temperature-recording data storage tags were recovered from three salmonids in Alaska (pink and coho salmon and steelhead trout) and five chum salmon in Japan after 21–117 days, containing the first long-term records of ambient temperature from Pacific salmonids migrating at sea. Temperature data imply diel patterns of descents to deeper, cooler water and ascents to the surface. Fish were found at higher average temperatures at night, with narrower temperature ranges and fewer descents than during the day. Fish tagged in the Gulf of Alaska were at higher temperatures on average (10–12°C) than chum salmon tagged in the Bering Sea (8–10°C). Chum salmon were also found at a wider range of temperatures (−1–22°C vs 5–15°C). This is probably related both to the different oceanographic regions through which the fish migrated, as well as species differences in thermal range and vertical movements. Proportions of time that individual fish spent at different temperatures seemed to vary among oceanographic regions. Steelhead trout may descend to moderate depths (50 m) and not be limited to the top few metres, as had been believed. Japanese chum salmon may seek deep, cold waters as they encounter warm surface temperatures on their homeward migrations. Temperature data from all fish showed an initial period (4–21 days) of day and night temperatures near those of sea surface temperatures, suggesting a period of recuperation from tagging trauma. A period of tagging recuperation suggests that vertical movement data from short-term ultrasonic telemetry studies may not represent normal behaviour of fish. The considerable diurnal and shorter-term variation in ambient temperatures suggests that offshore ocean distribution may be linked more to prey distribution and foraging than to sea surface temperatures.     

Farming of salmonids in Russia

Abstract. Salmonids of the genera Salmo and Oncorhynchus are the main aquaculture Interest of Russia. Culture of salmonids, as well as other species, is determined by two factors: vulnerability of coastal areas to storms and high temperatures in the south of Russia and long periods of icing and low temperatures in the north. Adaptation of salmonids to these conditions therefore is an important aspect of research in Russia.
The culture of salmonids in Russia can be divided into three categories:
(1) traditional hatchery rearing and release of fingerlings into natural populations;
(2) acclimatization of Pacific salmon through transoceanic transportation; and
(3) commercial production in sea cages.     

Bacterial kidney disease in salmonids

Bacterial kidney disease (BKD) is the most important bacterial infection in salmonid fish. Clinics, pathomorphology, distribution and possibility of therapy of BKD are discussed regarding results of literature as well as own experiences.     

Tagging experiments with salmonids

In order to find an efficient method for marking fish a tagging experiment has been carried out at the Fish Breeding Experimental Station, Sunndalsøra, Norway. Three different methods have been tried: jaw-tagging, cold-branding and tattooing with two different types of dye. During the winter 1972/1973 relatively large numbers of rainbow trout (12 602), sea trout (2 065) and salmon (13 141) were marked using the three marking methods mentioned. It was found that cold-branding with liquid nitrogen was the most rapid and inexpensive method for marking salmonids; after about one year between 87 and 92% of the fish can be identified.For cold-branding rainbow trout and sea trout an exposure time of 3 sec is too long.Tattooing with fluorescent pigments gave poor results in this experiment but could be a useful method for marking salmonids if a device could be constructed that tattoos bigger spots.Fast blue is not recommended for marking fast-growing salmonids.     

Hybridization in salmonids: Results and perspectives

This report presents a critical review of interspecific hybridization in salmonids and discusses the potentiality of hybrids for water management and fish farming.     

西北地区试养银鲑初报

银鲑原是一种海水鱼类 ,在美国经人工驯化后能够在淡水中养殖。近几年国内银鲑养殖仅限于北京地区几个有渔业外事关系的单位 ,其他省区没有养殖。本所 2 0 0 0年 5月 2 7日从北京康鑫水产公司引进银鲑试养 ,取得了良好的效果。1　苗种引进及放养5月 2 7日从北京康鑫水产公司 ,采用泡沫箱尼龙袋充氧加冰的方法 ,空运规格 7～ 8厘米的银鲑鱼苗 10 0 0尾 ,每箱装 2 50尾 ,运输时间 16小时 ,运输成活率 10 0 %。鱼苗运抵渔场后 ,先暂养在网箱中 ,投喂煮熟的鸡蛋黄 ,第 2天放入流水池塘。池塘面积 38平方米 ,水深 4 0厘米 ,养殖水为泉水 ,水温 10…     

Induction of polyploidy in salmonids by cytochalasin B

The purpose of this study was to investigate the possibility of producing tetraploid fishes. Eggs of salmon (Salmo Salar) and rainbow trout (Salmo gairdneri) were treated with concentrations of cytochalasin B ranging from 1 μg/ml to 100 μg/ml for varying periods of time. All treated groups had higher death rates than untreated controls. If the treatment was started immediately after fertilization and before the eggs had swollen all eggs died. The highest frequency of mosaic embryos and polyploid cells was obtained when the treatment started 35–70 h° (hour-degrees) after fertilization and lasted until about the 4-cell stage of development. A dose of 10 μg/ml of cytochalasin B gave the most satisfactory results. This concentration was used for further work. Two batches of 6000 salmon eggs and several groups of rainbow trout eggs were treated and hatched. The hatchability was generally low while the control group had a normal hatchability. If some of the treated fish are eventually found to be tetraploids and fertile, they will be used to produce triploid offspring by crossing with normal diploid fish.     

Virulence of Flavobacterium branchiophilum in experimentally infected salmonids

Abstract. The ability of selected strains of Flavobacterium branchiophilum to attach to and colonize the gills of five species of teleosts (four salmonid and one cyprinid) and cause mortality was investigated. In virulence studies with F. branchiophilum strain LAB4a, cumulative mortality was dose-dependent in rainbow trout, Oncorhynchus mykiss (Walbaum), and ranged from 0 to 75%. However, regardless of dose, the relative amount of gill-associated F. branchiophilum antigen increased 1 h after challenge. The gill-associated F. branchiophilum antigen in fish which survived (moribund fish) increased by four to six times compared to that detected on the gills 1 h after challenge. The gill-associated antigen on moribund fish was not significantly different from that on the gills of dead fish. Flavobacterium branchiophilum strain LAB4a also attached to the gills of brook trout, Salvelinus fontinalis (Mitchell), rainbow trout, chinook salmon, Oncorhynchus tshawytscha (Walbaum), Arctic charr, Salvelinus alpinus (L.), and common shiners, Luxilus cornutus (Mitchell), following a 1-h bath exposure, and caused mortality in all species. The virulence of eight strains of F. branchiophilum for rainbow trout was examined. Both virulent and avirulent strains adhered to the gills following bath exposure (fimbriae were observed on all strains), but only virulent strains had the capacity to further colonize the gills and cause mortality.     

Pathogenicity of Vibrio harveyi to salmonids

Out of 19 Vibrio harveyi isolates obtained from a diversity of hosts and geographical locations, 14 were pathogenic to rainbow trout, Oncorhynchus mykiss (Walbaum), and Atlantic salmon, Salmo salar L., with mortalities of up to 100% following intraperitoneal injections of 106 cells fish?1. The extracellular products (ECPs) of only five pathogenic isolates were harmful to fish. Both pathogenic and non‐pathogenic cultures produced ECPs containing caseinase, gelatinase, phospholipase, lipase and haemolysins. Vibrio harveyi VIB 645, which was the most pathogenic isolate, produced ECPs with a maximal effect on salmonids from preparations obtained by using cellophane overlays on tryptone soya agar supplemented with 1% (w/v) sodium chloride with incubation at 28 °C for 24 h. This preparation contained the highest titre of haemolytic activity to Atlantic salmon (1:256) and rainbow trout (1:32) erythrocytes.     

Predation by seals on salmonids in two Scottish estuaries

Detailed observations of the behaviour of harbour seals, Phoca vitulina L., at sites within the estuaries of the Rivers Dee and Don, in north-eastern Scotland, were made over two full years between 1993 and 1996. Small numbers of grey seals, Halichoerus grypus Fab., were also present. The presence of seals within the estuaries was strongly related to season, with maximum numbers observed in winter and early spring; seals were virtually absent in June and July. The River Don was used largely as a haul-out site, while the River Dee was used predominantly as a foraging site, although it was not possible to determine whether the same seals were using the two estuaries. More seals were hauled-out on the River Don during twilight and dark than in daylight. The seals were observed to eat mostly salmonids, Salmo salar L. and S. trutta L., unidentified roundfish and flounder, Pleuronectes flesus L. The otoliths identified in scats collected at the mouth of the River Don belonged to marine species indicating that the seals were also feeding outside the estuaries. A minimum estimate is given of the numbers of large salmonids eaten in each river during the course of the year. Although no information was available on the numbers of salmonids using the rivers or the reproductive status of the fish eaten by the seals, as a cause of mortality, seal predation on large salmonids in estuaries is apparently an order of magnitude less important than mortality caused by angling within the river.     

A riverscape perspective of Pacific salmonids and aquatic habitats prior to large‐scale dam removal in the Elwha River,Washington, USA

Abstract Dam removal has been increasingly proposed as a river restoration technique. In 2011, two large hydroelectric dams will be removed from Washington State’s Elwha River. Ten anadromous fish populations are expected to recolonise historical habitats after dam removal. A key to understanding watershed recolonisation is the collection of spatially continuous information on fish and aquatic habitats. A riverscape approach with an emphasis on biological data has rarely been applied in mid‐sized, wilderness rivers, particularly in consecutive years prior to dam removal. Concurrent snorkel and habitat surveys were conducted from the headwaters to the mouth (rkm 65–0) of the Elwha River in 2007 and 2008. This riverscape approach characterised the spatial extent, assemblage structure and patterns of relative density of Pacific salmonids. The presence of dams influenced the longitudinal patterns of fish assemblages, and species richness was the highest downstream of the dams, where anadromous salmonids still have access. The percent composition of salmonids was similar in both years for rainbow trout, Oncorhynchus mykiss (Walbaum), coastal cutthroat trout, Oncorhynchus clarkii clarkii (Richardson) (89%; 88%), Chinook salmon, Oncorhynchus tshawytscha (Walbaum) (8%; 9%), and bull trout, Salvelinus confluentus (Suckley) (3% in both years). Spatial patterns of abundance for rainbow and cutthroat trout (r = 0.76) and bull trout (r = 0.70) were also consistent between years. Multivariate and univariate methods detected differences in habitat structure along the river profile caused by natural and anthropogenic factors. The riverscape view highlighted species‐specific biological hotspots and revealed that 60–69% of federally threatened bull trout occurred near or below the dams. Spatially continuous surveys will be vital in evaluating the effectiveness of upcoming dam removal projects at restoring anadromous salmonids.     

Cold-branding and fin-clipping for marking of salmonids

Identification of individual fish is important under many research circumstances and is essential in breeding and selection work. Results are presented from the marking system used at the Norwegian Research Station for Salmonids. Trained personnel and good light conditions are necessary to obtain a high percentage of correct identifications. The best result obtained was 99% identification 22–28 months after marking. It is estimated that 1.4% of the fish read were incorrectly identified. The frequency of misidentified fish was higher when different cold-branded symbols were included in the system, increasing to a mean of 8% for salmon and 15% for rainbow trout.Cold-branding using five different symbols at two of six different positions on the fish gives 600 permutations when used in conjuction with clipping of the adipose and right or left pelvic fins. A satisfactory degree of correct identification is possible for use in a programme of selection in salmonids.     

Introduced northern pike predation on salmonids in southcentral Alaska

Northern pike (Esox lucius) are opportunistic predators that can switch to alternative prey species after preferred prey have declined. This trophic adaptability allows invasive pike to have negative effects on aquatic food webs. In Southcentral Alaska, invasive pike are a substantial concern because they have spread to important spawning and rearing habitat for salmonids and are hypothesised to be responsible for recent salmonid declines. We described the relative importance of salmonids and other prey species to pike diets in the Deshka River and Alexander Creek in Southcentral Alaska. Salmonids were once abundant in both rivers, but they are now rare in Alexander Creek. In the Deshka River, we found that juvenile Chinook salmon (Oncorhynchus tshawytscha) and coho salmon (O. kisutch) dominated pike diets and that small pike consumed more of these salmonids than large pike. In Alexander Creek, pike diets reflected the distribution of spawning salmonids, which decrease with distance upstream. Although salmonids dominated pike diets in the lowest reach of the stream, Arctic lamprey (Lampetra camtschatica) and slimy sculpin (Cottus cognatus) dominated pike diets in the middle and upper reaches. In both rivers, pike density did not influence diet and pike consumed smaller prey items than predicted by their gape‐width. Our data suggest that (1) juvenile salmonids are a dominant prey item for pike, (2) small pike are the primary consumers of juvenile salmonids and (3) pike consume other native fish species when juvenile salmonids are less abundant. Implications of this trophic adaptability are that invasive pike can continue to increase while driving multiple species to low abundance.     

Stress hormones and the cellular stress response in salmonids

The relationship between stress protein (SP) levels and the hormonal stress response in salmonids was examined through the measurement of gill SP70 and SP30 levels together with plasma cortisol, glucose and ion concentrations, in response to handling stress (45 s holding in a net), intraperitoneal cortisol implants, and heat shock (+10 °C). Handling and cortisol implants resulted in increased plasma cortisol and glucose levels. Heat shock following handling reduced plasma [Na⁺] below that observed in response to the handling stress alone, and heat shock following cortisol implant significantly lowered both plasma [Cl^–] and [Na⁺] below that of fish receiving the cortisol implant alone. Increased SP70 levels occurred 1 h following the 2 h +10 °C heat shock. Handling the fish prior to the application of heat shock suppressed the increase of SP70 levels in the gills. However, increased plasma cortisol concentrations alone did not attenuate gill tissue SP70 increase caused by heat shock. Physiological (10^–7 M) and pharmacological (10^–5 M) concentrations of adrenaline caused increased levels of SP70 in hepatocytes. Addition of the -blocker propanolol blocked this response to adrenaline. The results indicate that handling procedures do not result in an increase of hsp30 or hsp70 and may suppress hsp synthesis under certain circumstances.     

Intestinal microflora of salmonids: a review

Microflora isolated from fish intestines have been described for a limited number of salmonid fish species. The size of the microbial population of salmonids appears to vary within different regions of the gastrointestinal tract. The genera present in the gastrointestinal tract seem to be those which can survive and multiply in the intestinal tract. The predominant bacteria isolated from the salmonid gut are aerobes or facultative anaerobes. Few investigations have evaluated obligate anaerobes in the digestive tract of salmonids, and these studies have suggested that the population levels of obligate anaerobes are lower than those of facultative anaerobes. The bacterial genera isolated from fish intestines vary with salinity, antibiotics, chromic oxide, diet and dietary components such as linoleic acid, and display day-to-day fluctuations. Acinelobacter spp., Enterobacter spp. and Pseu-domonas spp. are regarded as autochthonous in Oncorhynchus species, while Aeromonas spp., Flavobacterium spp., Pseudomonas spp. and Lactobacillus spp. are suggested as autochthonous in Arctic charr, Salvelinus alpinus(L.).