Salmonid Eggs Research Articles

Adenosine triphosphate levels of chinook salmon (Oncorhynchus tshawytscha) eggs following in vitro maintenance and activation/fertilization.

To further examine the concept of egg quality and the physiology of stored salmonid eggs, we investigated the effects of different oxygen tensions on the adenosine triphosphate (ATP) levels of unfertilized, activated, and fertilized chinook salmon (Oncorhynchus tshawytscha) eggs. The ATP levels of unfertilized chinook salmon eggs were 2.61±0.14 nmol ATP per egg (17.6±0.9 μmol l−1 relative to cell water) and ranged from 1.98 to 3.63 nmol ATP per egg. The ATP content of unfertilized eggs maintained at 10 °C under 100% O2, 21% O2, and 100% N2 remained unaltered throughout a 120 h storage period. Storing eggs under identical conditions at 20 °C (in an effort to speed egg metabolism and ATP turnover) resulted in significant O2-independent decreases in ATP levels. However, ATP levels of unfertilized eggs exposed to 1 mmol l−1 potassium cyanide (a potent inhibitor of oxidative phosphorylation) at 10 °C were significantly decreased after 24 h and continued to decline throughout the 120 h maintenance period to about 30% of time=0 values. Maintenance with exogenous nutrients (5 mmol l−1 acetate plus 5 mmol l−1 pyruvate) over 120 h at 10 °C did not alter the ATP content of unfertilized eggs. Eggs activated by exposing them to 10 °C water for a few minutes showed a rapid decrease in ATP values, regardless of whether the eggs were fertilized or not. Following an initial ∼25% drop after fertilization, the ATP levels remained stable for the remainder (5 d) of the incubation period in eggs maintained in 10 °C water. Therefore, unfertilized chinook salmon egg ATP levels appear to be relatively stable and maintained by a low, cyanide-inhibitable metabolism. The stability of egg ATP levels may be one reason that salmonid eggs can be stored for several days while eggs from other fishes cannot.

Modelling the probability of salmonid egg pocket scour due to floods

Modelling the probability of salmonid egg pocket scour due to floods

Groundwater in headwaters: hydrological and ecological significance

Abstract The hydrological and ecological significance of groundwater has generally been under-estimated in headwater catchment studies within the Celtic regions. The paper presents data from headwater catchments in both upland and lowland settings in northern Scotland to address this gap in our understanding. Research in the 10 km 2 Allt a’ Mharcaidh catchment in the western Cairngorms has demonstrated that a range of groundwater sources in various drift deposits can account for c. 50% of annual runoff, even in a high altitude headwater stream. Despite the traditional assumption that upland catchments have limited aquifer storage, oxygen isotope studies of groundwater imply mean water residence times of up to five years which indicate a range of groundwater sources in montane environments. Moreover, hydrogeochemical reactions in the saturated zone appear to regulate stream water chemistry at moderate and low flows. In such montane environments, groundwater discharges at springs create unique wetland habitats which often form the source of headwater streams and affect riparian areas. In lowland catchments the hydrological significance of groundwater is equally important. In addition, recent studies in a salmon spawning stream in the Newmills Burn, Aberdeenshire has shown that aquifer-stream interactions in hyporheic zones are crucial in maintaining habitat conditions conducive to the survival of salmonid eggs, and the subsequent population of salmon streams. It is concluded that interdisciplinary studies incorporating hydrogeological investigations are fundamental to a proper understanding of the hydrology and functional ecology of catchment systems in the Celtic regions.

Genotyping of individual fish oocytes based on polymerase chain reaction amplification of mitochondrial DNA

A major reason for the routine use of the polymerase chain reaction (PCR) in genetic projects is that it requires small amounts of imperfectly puri®ed DNA for the detection of polymorphic markers. Recently, a number of protocols have been proposed that permit PCR ampli®cation from a variety of tissues. They have been summarized brie y by Estoup, Largiader, Perrot & Chourrout (1996). Here, we propose a procedure of fast mitochondrial (mt) DNA extraction from individual salmonid eggs that allows further PCR ampli®cation and genotype studies. Fish eggs (in particular salmonid eggs) are the samples that require mechanical treatment before DNA extraction in order to allow contact between cytoplasm and lysis solution. Eggs of white®sh (Fig. 1A) and rainbow trout were tapwater activated (5 min), and then their chorion was pierced with a glass cannula under a stereomicroscope to allow the escape of cytoplasmic uid (Fig. 1B). The uid was transferred into a 0.5-mL Eppendorf tube, lysed in 3 mL of lysis buffer [200 mM KOH, 50 mM dithiothreitol (DTT)] for 30 min at 60 °C, and neutralized by 4 mL of neutralizing buffer (900 mM Tris-HCl, pH 8.3, 300 mM KCl, 200 mM HCl; modi®ed from Li, Cui & Arnheim 1991; Fig. 1C). Before use, samples were vortexed brie y for 3 s. An aliquot of 1±3 mL (usually 2 mL) was taken as a template for a 12-mL total volume of PCR reaction. Forty cycles of PCR (beginning with preliminary denaturation at 95 °C for 1 min) were carried out in a GeneAmp PCR system 2400 with a primer pair L-H (L: 5¢-CCACTAGCTCCCCAAAGCTA-3¢; H: 5¢-ACTTTCTAGGGTCCATC-3¢), which spans the entire control region of both white®sh and rainbow trout mtDNA (Brzuzan 1998). The cycle consisted of 92 °C for 1 min, 50 °C for 1 min and 72 °C for 1.5 min. Positive ampli®cations were observed regularly and allowed further sequence analysis with restriction enzymes (Fig. 1D). The extraction procedure presented is simple, rapid and ef®cient for several ampli®cations of mitochondrial sequences. The ability to analyse DNA sequence variation in single cells (oocytes) provides a unique tool for solving many important biological problems. For example, it permits revelation of the presence of both mutant and wild-type mtDNA (heteroplasmy) in the same ®sh egg, which is equal to an individual `®sh'. Investigating mature oocytes from heteroplastic females can determine the relationship between the levels of drift occurring during oogenesis and mutation rates, thus giving an insight into the evolution of ®sh mtDNA (Nesbu, Arab & Jakobsen 1998). It is possible that the `single-cell' PCR is applicable to the analysis of the polymorphic DNA regions in an embryo derived from an egg at the earliest stages of development. Finally, because of the type of tissue used (an egg), it R

Sediment transport and siltation of brown trout (Salmo trutta L.) spawning gravels in chalk streams

Deposition rates of fine sediment into brown trout spawning gravels were measured at monthly intervals for a period of one year in a small channel of the River Test, Hampshire. Data were also collected on stream discharge, water depth, flow velocity and suspended sediment concentrations. Deposition rates followed a seasonal pattern and were maximal during periods of high discharge in the late winter/early spring when suspended sediment concentrations were high. The material deposited in the spawning gravels included silts and fine sands (<250 μm) that were transported in suspension and coarser fragments of low density tufa-like material that were transported as bed load. The ecological implications of fine sediment deposition for salmonid egg survival in chalk streams are considered. Copyright © 1999 John Wiley & Sons, Ltd.

Water temperatures within spawning beds in two chalk streams and implications for salmonid egg development

Water temperatures within brown trout (Salmo trutta L.) spawning gravels were measured in two Hampshire chalk streams from October 1995 to April 1996 inclusive. During the winter, mean intra-gravel water temperatures were higher than those in the stream, and increased with depth in the gravel bed. The amplitude of diel fluctuations in water temperature decreased with depth in the gravel bed, although diel fluctuations were still evident at a depth of 30 cm. Differences in intra-gravel temperature gradients between the two study sites were attributed to differences in the amplitude of stream water temperature fluctuations and there was no evidence that either of the study sites were located in zones of upwelling groundwater. Published equations are used to predict, from temperature, the timing of important stages in the development of brown trout embryos (eyeing, hatching and emergence) for eggs spawned in the autumn and winter and buried at different depths in the gravel bed. Copyright © 1999 John Wiley & Sons, Ltd.

Water temperatures within spawning beds in two chalk streams and implications for salmonid egg development

Water temperatures within brown trout (Salmo trutta L.) spawning gravels were measured in two Hampshire chalk streams from October 1995 to April 1996 inclusive. During the winter, mean intra-gravel water temperatures were higher than those in the stream, and increased with depth in the gravel bed. The amplitude of diel fluctuations in water temperature decreased with depth in the gravel bed, although diel fluctuations were still evident at a depth of 30 cm. Differences in intra-gravel temperature gradients between the two study sites were attributed to differences in the amplitude of stream water temperature fluctuations and there was no evidence that either of the study sites were located in zones of upwelling groundwater. Published equations are used to predict, from temperature, the timing of important stages in the development of brown trout embryos (eyeing, hatching and emergence) for eggs spawned in the autumn and winter and buried at different depths in the gravel bed. Copyright © 1999 John Wiley & Sons, Ltd.

Some biochemical characteristics of fungi isolated from salmonid eggs

Fungal isolates from salmonid eggs displayed apparently unique patterns of biochemical characteristics at both the generic and specific levels. of the five genera examinedAchlya andPythium were able to assimilate 13–16 out of 19 carbohydrates.Aphanomyces was able to assimilate only glucose and starch, which was assimilated by all isolates. Members ofSaprolegnia displayed identical patterns of carbohydrate assimilation, except forS. hypogyna, which was also able to assimilate melibiose, in common withAchlya, Pythium, andLeptolegnia. Pythium was the only genus capable of assimilating salicin. OnlyAchlya andP. monospermum were able to assimilate rhamnose. In terms of amino acid assimilation isolates ofSaprolegnia ferax andS. diclina displayed an identical patterns, as did isolates ofS. parasitica andS. hypogyna. OnlyAphanomyces frigidophilus isolate was capable of assimilating cysteine. All genera exceptPythium assimilated glutamine, a fundamental amino acid. All isolates exhibited lipase and fatty acid esterase activities but no cellulase acitivity. The biochemical characteristics discovered in this study offer possibilities for identification and classification of these fungi, which are discussed herein.

Effects of overripening on spawning behaviour and reproductive success of Atlantic salmon females spawning in a controlled flow channel

The influence of overripening on salmonid egg quality has often been described in artificial breeding. However, no information exists on the impact of this factor on fish reproducing naturally, although it is likely to be critical, especially in disturbed environments. Pairs of Atlantic salmon in which the size of the male and the female was evenly matched were released in a spawning channel from 1 to 12 days after ovulation. Handling did not affect egg quality. Overripening had a negative effect on egg viability. Egg mortality, infertility and malformations increased with the number of days after ovulation. In females which had just matured, 16·7% of their recovered eggs were dead, 3·1% were unfertilized and 1·7% were malformed, as compared to 25·4, 9·7 and 5·4%, respectively, in females that had been mature for at least a week. Overripening played a role in both female spawning behaviour and capacity to spawn, as females which had been mature for over a week released their eggs more quickly while they retained more ova in their abdominal cavity than early spawning females. Thus, in studies of reproductive behaviour and in particular of sexual selection, it is critical to take into account the maturation status of females since the duration of spawning activity is used by various authors to determine female sexual motivation. Alternatively, overripening may decrease the female selectivity for mates.

Ineffectiveness of Iodophore Treatment in Disinfecting Salmonid Eggs Carrying Cytophaga psychrophila.

Eggs of coho salmon (Oncorhynchus kisutch), rainbow trout (O. mykiss), and masu salmon (O. masou) were artificially inseminated and subsequently immersed in a modified Ordal and Anacker's broth culture of Cytophaga psychrophila (107-108CFU/ml) for 30min. The bacterium was recovered from the eggs at the eyed stage with viable cell counts ranging from 105 to 107CFU/g. The fertilized eggs were disinfected with 50ppm povidoneiodine for 15min immediately after experimental infection. However, C. psychrophila was detected by a broth culture method from 60-80 percent of the surface-disinfected eggs. At the eyed stage, the eggs were disinfected again with povidone-iodine at concentrations of 50-1, 000ppm for 15-120min. C. psychrophila was isolated from all of them at densities of 104-107CFU/g. The uninfected control eggs were all negative for the bacterium. It is concluded that the povidone-iodine treatment is ineffective to eliminate C. psychrophila from salmonid eggs.

Stress induced elevation of plasma cortisol in adult female coho salmon (Oncorhynchus kisutch), is reflected in egg cortisol content, but does not appear to affect early development

Circulating levels of cortisol, the major corticosteroid among teleosts, increase in response to environmental Stressors. Cortisol has also been reported to be present in the freshly ovulated eggs of a number of teleost species. Since environmental Stressors have been implicated in the decrease of egg quality in salmonids, this study was conducted to investigate possible connections between egg cortisol content and subsequent viability. A physical Stressor applied to a single group of adult female coho salmon (Oncorhynchus kisutch), during the final two weeks of oogenesis appeared to result in significantly elevated plasma cortisol levels (227.5 ± 61.5 ng/ml) above those observed in a single group of control animals (141.0 ± 42.7 ng/ml), although other factors cannot be ruled out. Mean egg cortisol content (25.3 ± 0.77 ng/g) was significantly higher in the disturbed than in the undisturbed females (9.90 ± 0.94 ng/g), suggesting that cortisol content in eggs of salmonids is reflective of plasma levels during late oogenesis. Gonadosomatic index was unaffected by the treatment, although there was some evidence to suggest that elevated cortisol levels may have hastened ovulation in the experimental group. Paired groups of eggs from single females having either unmanipulated (37.0 ± 5.4 ng/g) or artificially elevated (232.7 ± 13.9 ng/g) levels of cortisol showed no significant differences in terms of time to, or synchrony of hatch, yolk sac to body weight ratio at hatch, growth from hatch to 52 days post fertilization (dpf), or percent mortality. Cortisol was seen to clear rapidly from eggs in both experimental and control groups soon after fertilization, and there was no significant difference observed between groups by 8 dpf, suggesting that maternal cortisol clears from developing embryonic salmon by the late eyed stage and may not be a factor in later development.

Aquatic Fungi Developing on Eggs of Salmonids

Aquatic fungi isolated from salmonid eggs incubated at six fishery stations in Japan belonged to the genera Saprolegnia, Achlya, Aphanomyces, Leptolegnia, and Pythium. The species diversity of the fungi varied according to the site studied.

Riverine salmonid egg burial depths: review of published data and implications for scour studies

Published data on salmon, trout, and charr egg burial depths are highly variable and inconsistent. Primary sources of variation include elevation datum and portion of the egg pocket referenced to; differences in spawning behavior and the number, thickness, and location of egg pockets; relationships between egg depth, fish species, and corresponding size of female and spawning substrate and velocity characteristics; sampling method; presence of excavation barriers; redd superimposition; and scour and fill by hydraulic and other mechanical processes. Such sources of variability in the reported data have important implications for studies of scouring processes in salmonid spawning areas that require accurate identification of egg burial depths for predicting and preventing potential scour impacts. Cumulative measurement error and unexplained variation may amount to 5-20 cm or more in published values. The most relevant data for scour impact assessments are depths from the original stream bed elevation down to the top of the main egg pocket. Frequency distribution data are needed for determining probabilities and cumulative levels of scour impacts and for managing genetic diversity as well as population size. Preliminary depth threshold criteria are proposed for use now, pending further research.

Hyporheic temperature patterns within riffles

This paper outlines the results of a pilot study using data at 12 min intervals from 20 miniature temperature dataloggers to establish vertical and longitudinal temperature patterns within a river bed. Data are presented from two adjacent riffles immediately below the Blithfield Reservoir on the River Blithe, Staffordshire, UK, for a five day period in July 1994. Hyporheic temperatures were warmer than those of groundwater, colder than those of surface water and decreased with depth into the river bed. At the heads of the riffles shallow sites (20 cm depth) mirrored surface temperature patterns but were on average 1.53°C cooler while deeper sites (40 cm depth) were 2.60°C cooler on average. Hyporheic temperatures lagged behind the surface water pattern and lag times increased with depth. Sites at the riffle tails generally displayed temperature patterns similar to those of the groundwater system: on average, temperatures were 4.32°C cooler than surface water temperatures and showed no significant variation. Hyporheic temperature patterns at the heads of the riffles suggested downwelling surface water, while the tails appeared to be influenced by upwelling groundwater. Both riffles displayed similar hyporheic temperature patterns but riffle 1 was on average 1.22°C warmer per site than riffle 2. Temperature differences between the riffles are attributed to bed form and substratum composition. These factors may have significant ecological implications including rates of organic matter decomposition, invertebrate life cycles and salmonid egg hatching times.

Specific protective activity demonstrated in eggs of broodstock salmon injected with rabbit antibodies raised against a fish pathogen

DAO Diseases of Aquatic Organisms Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials DAO 31:95-101 (1997) - doi:10.3354/dao031095 Specific protective activity demonstrated in eggs of broodstock salmon injected with rabbit antibodies raised against a fish pathogen Laura L. Brown1,2,*, Trevor P. T. Evelyn2, George K. Iwama1 1Department of Animal Science, Canadian Bacterial Diseases Network, University of British Columbia, #248 - 2357 Main Mall, Vancouver, British Columbia, Canada V6T 1Z4 2Biological Sciences Branch, Department of Fisheries and Oceans, Pacific Biological Station, 3190 Hammond Bay Road, Nanaimo, British Columbia, Canada V9R 5K6 *Present address: National Research Council of Canada, Institute for Marine Biosciences, 1411 Oxford Street, Halifax, Nova Scotia, Canada B3H 3Z1. E-mail: laura.brown@nrc.ca Many infectious disease agents affect salmonids early in life, long before the immune system of the fish is able to mount an efficient, protective response. This study was undertaken to determine if protective antibodies could be transferred to salmonid eggs and embryos by injecting the antibodies into female broodstock salmon prior to spawning. Resistance to Vibrio anguillarum (Va) was used as the model for this system because it is known that resistance to vibriosis is antibody-mediated. Antibodies raised against Va in rabbits were injected into female coho salmon Oncorhynchus kisutch before spawning and were detectable in the eggs by immunoassays. Fry from the injected broodstock were also challenged with Va following absorption of their yolk sac, but were not protected against Va. Contents of eggs from all broodstock (including saline-injected controls) were injected into naive coho fry, which were then challenged with live Va. Egg material from broodstock injected with rabbit anti-Va antibodies conferred protection against Va; in contrast, egg material from broodstock injected with saline did not. The results suggest that vertical transfer of mammalian antibodies can occur in salmonids; however, any conferred protection is not maintained for long after the yolk sac is absorbed. The findings described demonstrate a potentially useful new approach for passively immunizing large numbers of yolk sac larval salmonids against certain pathogens. Immunoglobulin · Salmonid eggs · Vertical transmission · Mammalian antibodies · Maternal transfer Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in DAO Vol. 31, No. 2. Publication date: November 20, 1997 Print ISSN:0177-5103; Online ISSN:1616-1580 Copyright © 1997 Inter-Research.

Evidence that the causal agent of bacterial cold-water disease Flavobacterium psychrophilum is transmitted within salmonid eggs

Evidence that the causal agent of bacterial cold-water disease Flavobacterium psychrophilum is transmitted within salmonid eggs

Riverine salmonid egg burial depths: review of published data and implications for scour studies

Riverine salmonid egg burial depths: review of published data and implications for scour studies

Disease problems of salmonid fish in Japan caused by international trade.

The author details the connection between disease outbreaks in salmonid fish and imports of salmonid eggs into Japan since the 1950s. The following diseases and species are involved: -infectious pancreatic necrosis in rainbow trout (Oncorhynchus mykiss) -infectious haematopoietic necrosis in sockeye ( of 'kokanee') salmon (O. nerka) and masu salmon (O. masu) -cold water disease, erythrocyte inclusion body syndrome, and bacterial kidney disease (caused by Renibacterium salmoninarum) in coho salmon (O. kisutch), ayu (Plecoglossus altivelis), rainbow trout and masu salmon. The author also discusses the strategies aimed at controlling the risk of disease spread through international trade in salmonid fish and fish products in Japan. Essential in these strategies are the following actions: -exchange of information on controlling disease problems -studies to establish standard methods to identify or detect fish pathogens -fish health certification.

Characteristics of current international trade of live salmonid eggs.

World trade in live salmonid embryos (eyed eggs) has grown in response to increased global salmon production, particularly in South America, and parallels international trade in farmed salmonid products. Rainbow trout (Oncorhynchus mykiss), Atlantic salmon (Salmo salar) and coho salmon (O. kisutch) are the most commercially important species. In 1992, the Food and Agriculture Organization of the United Nations estimated world production of rainbow trout at 300,000 tonnes, while the production of Atlantic salmon was estimated at 250,000 tonnes and coho salmon at 50,000 tonnes. One can estimate that roughly 3 billion, 150 million and 30 million eggs, respectively, were required to produce this yield. Broodstock are cultivated world-wide, using a wide variety of water sources, including the marine environment, riverine water containing anadromous fish, and ground water free of migrating fish. As many as 70% of all coho eggs are derived from feral fish. Approximately 50% of all commercial salmonid eyed eggs are produced in Europe, and approximately 15% are produced in the state of Washington, United States of America. Conditions which are ideal for commercial salmonid grow-out are not necessarily ideal for the cultivation of salmonid broodstock; this is one reason why international egg trade is necessary. The trend of current salmonid health regulations is towards facilitating egg commerce on a regional level, in an attempt to control disease transmission. Regulations controlling egg importation often include pathogens which are not vertically transmitted. This serves only to increase egg prices, in compensation for the cost of laboratory tests. Genetic improvements have been the cornerstone of increasing commercial production of all agricultural commodities. Fish health regulations are sometimes instituted in an effort to protect the local industry, but in fact they act more often to restrict the flow of genetic material and may actually serve to reduce industry productivity and profitability.

The effect of early exposure of Coho salmon ( Oncorhynchus kisutch) eggs to the p57 protein of Renibacterium salmoninarumon the development of immunity to the pathogen

Bacterial kidney disease (BKD) in salmonids is caused by Renibacterium salmoninarum(Rs) which is transmitted vertically through salmonid eggs. This study investigated the effect of vertical transmission of one protein of Rs, p57, on the development of the immune system of coho salmon ( Oncorhynchus kisutch) and on the susceptibility of the fish to subsequent challenge with Rs. It was shown that exposure of coho salmon at the egg stage to the p57 protein of Rs induces at least partial immunosuppression. Coho salmon eggs were injected with varying amounts of p57. The eggs were fertilized, the progeny were vaccinated against Rs, and then challenged with live, virulent Rs. Fish that had been injected as eggs with 100 ng of p57 demonstrated a significantly higher cumulative percent mortality (50 %) than those from the saline-injected eggs (controls) (14 %). The same fish also produced significantly lower levels of antibodies against p57, although not against whole Rs cells, than those derived from saline-injected eggs. It appeared, therefore, that there was some specificity to the immune suppression. A decreased proportion of phagocytic cells isolated from fish exposed as eggs to 100 ng p57, showed respiratory burst activity (0 ·4 %) compared with the proportion of cells isolated from the saline-injected (control) group (16 ·5 %). These data suggest that early (egg stage) exposure of coho salmon to p57 results in long-term immunosuppression and a decreased ability in the animal to resist subsequent challenges with Rs.