Triploid Atlantic Salmon Research Articles

The kinetics of the hypoferraemic response and changes in levels of alternative complement activity in diploid and triploid Atlantic salmon, following injection of lipopolysaccharide

To study any possible effects of triploidy on the kinetics of the response of two non-specific disease factors, full sibling diploid and triploid Atlantic salmon were injected intraperitoneally with either lipopolysaccharide (1mg kg−1body weight) or saline. Individually marked fish were repetitively blood sampled for up to 19 days. Total serum protein concentrations remained constant throughout the experiment indicating that the sampling regime did not cause haemodilution. The alternative complement pathway activity (measured by the titre of haemolytic activity against rabbit erythrocytes) in the serum of saline injected fish remained constant but in LPS-injected fish it fell to barely detectable levels 2 days after injection, but recovered to pre-treatment levels by about day 5. Triploid fish took slightly longer to reach full recovery levels than diploids. All groups of fish showed a hypoferraemic response, suggesting that the sampling regime was at least partially responsible. However, the response was more rapid and pronounced in the LPS-injected fish. In the latter, serum iron concentrations decreased to very low levels by day 2 post-injection in the diploid fish and by day 3 in the triploid fish. Pre-treatment iron levels were re-established by about 15 days post-injection in all groups. The data show only slight differences between the diploid and triploid fish, but the longer time taken for the triploids to recover complement activity and the slower onset of the hypoferraemic response following injection of LPS, suggest that they may be at a disadvantage compared with their diploid siblings in their defence against bacterial infections.

Use of sterile triploid Atlantic salmon (Salmo salar L.) for aquaculture in New Brunswick, Canada

Induced triploidy is the only effective method currently available for mass production of reproductively sterile salmonids for aquaculture. Repeated studies at the Atlantic Salmon Federation's hatchery (St Andrews, New Brunswick, Canada) have shown only minor differences between triploids and diploids in survival to S1 smolt age (15 months), percentage of the population which became S1 smolts, and mean S1 smolt size. However, a similar study at a commercial hatchery was terminated because of exceptionally high mortality of triploids prior to the start of feeding. Marine growout trials in sea cages showed that triploids grew well in seawater, but had reduced survival rates (leading to a 5-15% reduction in yield at harvest) and high rates of jaw abnormalities. Similar results have been reported elsewhere. Although induced triploidy can be used effectively as a management tool to ensure lack of reproduction, there is at present little support of the aquaculture industry to switch to their large-scale use. In light of fundamental biological differences, it is perhaps naive to expect triploids to perform as well as diploids using standard culture methods. Triploids should be treated as a new “species” for aquaculture development, beginning with research to determine their optimum rearing requirements.

The hematology of diploid and triploid transgenic Atlantic salmon ( Salmo salar )

This study examined the erythrocyte height/length, hematocrit, total blood hemoglobin concentration and mean cellular hemoglobin content of diploid and triploid transgenic and non-transgenic Atlantic salmon, to clarify the interaction between metabolic rate and hematology in these fish. Triploid erythrocytes were significantly longer and proportionately thinner than diploid erythrocytes for both genotypes. These morphological differences gave triploid erythrocytes an elliptical appearance with the width being ∼53% of the length, whereas diploid erythrocytes tended to be more rounded with the width being ∼62% of the length. As well, diploid and triploid transgenic erythrocytes were significantly shorter and thinner (P<0.0001) than their non-transgenic counterparts. Although not significant, observations using a Channelized Coulter Counter showed that transgenic erythrocytes tended to be higher in count and smaller in volume than non-transgenic erythrocytes of the same ploidy. Transgenics likely produce erythrocytes with higher surface area to volume ratio in response to their elevated metabolic rates. No other major hematological differences were observed between transgenics and non-transgenics of the same ploidy.

Ocean migration and recaptures of tagged, triploid, mixed-sex and all-female Atlantic salmon (Salmo salar L.) released from rivers in Ireland.

Fiftyfour thousand diploid and triploid Atlantic salmon were tagged with coded-wire micro-tags and released to the sea as smolts from two freshwater sites in Ireland in 1996 and 1997. Over 36,000 were mixed-sex groups in which the triploids (MS3N) were treated batches and the diploids (MS2N) were untreated batches of a single group of fertilized eggs at each site and year class. Over 17,000 were all-females, the triploids (AF3N) being treated batches and the diploids (AF2N) untreated batches of a single group of fertilized eggs at each site and year class. Adult tagged fish were subsequently recovered in the coastal fishery and in freshwater traps and angling fisheries in the rivers of release during 1997, 1998 and 1999. Recoveries from migration ranged from 0.08 to 9.79%. Diploid recoveries were within the normal ranges for salmon ranched from these sites, being between 0.64 and 1.82% at one site and between 3.85 and 9.79% at the other. Triploid recoveries, which occurred in the coastal fishery and in freshwater, ranged from 0.08 to 0.40% at the first site and from 0.98 to 2.05% at the other. Overall, triploid recoveries were between 12 and 24% of their diploid siblings within each release group. There were two peaks of recapture in the coastal fishery, the first in mid-June and the second in mid to late July. All-female diploids appeared to enter the fishery in advance of mixed-sex diploids. Triploids were the latest to arrive. There was no evidence of increased straying in triploids relative to diploids and the mean lengths, weights and condition factors were not significantly different between the ploidy groups. Triploidisation therefore reduced the home water harvest of treated salmon to less than 25% but did not completely eliminate triploid recaptures. The way in which triploidisation may influence the return of salmon from the oceanic feeding grounds is discussed.

Digestive protease activities and free amino acids in white muscle as indicators for feed conversion efficiency and growth rate in Atlantic salmon ( Salmo salar L.)

The aim of the present experiment was to screen several biochemical indices in fish and their interrelations in order to select variables for future studies of growth rate and feed conversion. Several parameters [trypsin activity, chymotrypsin activity, free amino acids (FAA) in plasma and white muscle, and RNA and RNA/protein ratio in the white muscle] were measured together with specific growth rate (SGR), feed intake and feed conversion efficiency (FCE) in four groups of diploid or triploid Atlantic salmon (Salmo salar L.) reared under different light regimes. SGR was measured on individually tagged fish, whereas feed intake and feed conversion was estimated on tank basis. A principal component analysis (PCA) explained 80.6% of the variance in the data, using all measured parameters, regardless of ploidy and light regime. Muscle free hydroxyproline showed the highest correlation, alone explaining 55% of SGR variability. The SGR also significantly correlated with trypsin activity (r=0.34), the activity ratio of trypsin to chymotrypsin (T/C) (r=0.39), plasma essential FAA (EAA) (r=0.39), plasma total FAA (TFAA) (r=0.37), the ratio of essential to non-essential FAA (EAA/NEAA) in the white muscle (r=−0.45), muscle RNA (r=−0.45) and RNA/protein ratio (r=−0.41). Tank FCE correlated positively (r=0.97) with SGR, T/C ratio and muscle free hydroxyproline, and negatively (r=−0.90) with muscle EAA/NEAA. The groups reared under continuous light (LL) regime showed significantly higher SGR than simulated natural photoperiod (SNP) groups, and with an apparently higher FCE. A higher growth rate was associated with either a higher consumption rate and/or a higher feed utilization. A negative correlation between muscle RNA concentration and SGR may indicate that increased growth rate under LL regime was not caused by an increased protein deposition rate.

Family differences in relative growth of diploid and triploid Atlantic salmon ( Salmo salar L.)

Comparisons of growth for diploid and triploid full sibs from 20 families of Atlantic salmon ( Salmo salar L.), ranging from 4 to 24 progeny/family, involved 628 individuals. Length and weight data, after approximately 75 weeks in seawater, indicated higher within and between family variances in triploids than in diploids. Regression analyses revealed that improvement of triploid populations might require measurements on triploid sibs of the diploid to be involved in reproduction.

An evaluation of the use of triploid Atlantic salmon ( Salmo salar L.) in minimising the impact of escaped farmed salmon on wild populations

The impact of escaped farmed salmon on wild populations may have potentially negative genetic and ecological effects. There is widespread evidence that farmed salmon interact with wild salmon. The use of sterile fish in culture has been proposed as a means of eliminating genetic interaction and minimising the ecological effect of farmed salmon. In this study, the migration behaviour of groups of triploid salmon were investigated through the controlled release of microtagged triploid and diploid stocks on the western coast of Ireland. Mixed-sex and all-female stocks of ranched grilse origin were triploidised using hydrostatic pressure. Smolts were ranched from the hatchery of origin and two groups of post-smolts were released from cages in a marine site. The return of adult salmon from these experimental release groups to coastal and freshwater capture sites was monitored as part of the Irish national coded wire tag recovery programme. The return of triploid salmon from each of the release groups, both to the coast and to fresh water, was significantly reduced compared to diploid salmon. The highest percentage return to fresh water (2.25%) was in the ranched mixed-sex diploid group. In contrast, no salmon from the cage release groups returned to the hatchery location on the Burrishoole river system and recoveries in other freshwater systems were low (<0.01%). The return of a small number of hormonally deficient, sterile triploid female fish suggests that migration to fresh water is not inextricably linked with reproduction. The substantially reduced return of hormonally competent triploid males to the coast and to fresh water, indicates that other factors may have an effect on their marine survival. The reduced return of triploid salmon to the coast and to fresh water, together with their inability to produce viable offspring, demonstrates the potential for triploidy as a means of eliminating genetic interactions between cultured and wild populations, and of reducing the ecological impact of escaped farmed fish.

Blood oxygen transport, rheology and haematological responses to confinement stress in diploid and triploid Atlantic salmon, Salmo salar

Diploid and triploid all-female Atlantic salmon ( Salmo salar) smolts were challenged with 2.5 h of confinement stress in aerated seawater. Subsequent stress responses were quantified by plasma cortisol, glucose, and lactate, and by the haematological parameters haematocrit (Hct), red blood cell count (RBCC), mean cell volume (MCV), blood haemoglobin concentration (Hb), mean cell haemoglobin (MCH), mean cell haemoglobin concentration (MCHC), total protein and erythrocyte adenosine triphosphate (ATP). The magnitude of stress responses was similar between diploid and triploid smolts. Triploid smolts displayed a higher MCH, but lower Hb than diploid smolts. The blood oxygen affinity of diploid and triploid fish was similar at 15°C over the pH range 6.76–7.99 and the isohaemoglobin components were identical. The enlarged triploid erythrocytes showed reduced shear-dependence on blood viscosity at constant Hct and are therefore unlikely to contribute to greater peripheral vascular resistance. The results show that despite having fewer, larger erythrocytes, triploids have very similar oxygen carrying capacity and haematological response to stress as diploids. This suggests that the higher farm mortality reported for triploids in response to stress is not generated by their failure to show respiratory homeostasis in the face of stress.

Physiological stress responses to confinement in diploid and triploid Atlantic salmon

Confinement of juvenile Atlantic salmon Salmo salar from four different populations (all–female diploids, all–female triploids, mixed sex diploids and mixed sex triploids) either before (FW parr) or after (SW smolts) transfer to sea elevated plasma cortisol and plasma lactate from control levels irrespective of ploidy status. Both before and after confinement, plasma cortisol levels in SW smolts (6–174 ng ml–1) were higher than those in FW parr (4–58 ng ml–1), which possibly reflected the physiological challenge of acclimation to SW. Mixed sex populations of SW smolts had higher cortisol levels than all–female populations. The duration of confinement (1, 3 or 6 h) affected the magnitude of the plasma cortisol and lactate responses in SW smolts. Plasma cortisol levels in diploid and triploid SW smolts subjected to 2 h of confinement decreased to pre–stress levels within 6 h post–confinement. Plasma lactate levels were not significantly different from pre–stress levels 48 h after confinement. As no difference exists in primary and secondary stress responses of Atlantic salmon of differing ploidy status, it is unlikely that differences in mortality rates between diploid and triploid populations under commercial conditions can be attributed to differences in their physiological responses to periods of stress lasting up to 6 h.

Physiological stress responses to confinement in diploid and triploid Atlantic salmon

Confinement of juvenile Atlantic salmon Salmo salar from four different populations (all–female diploids, all–female triploids, mixed sex diploids and mixed sex triploids) either before (FW parr) or after (SW smolts) transfer to sea elevated plasma cortisol and plasma lactate from control levels irrespective of ploidy status. Both before and after confinement, plasma cortisol levels in SW smolts (6–174 ng ml–1) were higher than those in FW parr (4–58 ng ml–1), which possibly reflected the physiological challenge of acclimation to SW. Mixed sex populations of SW smolts had higher cortisol levels than all–female populations. The duration of confinement (1, 3 or 6 h) affected the magnitude of the plasma cortisol and lactate responses in SW smolts. Plasma cortisol levels in diploid and triploid SW smolts subjected to 2 h of confinement decreased to pre–stress levels within 6 h post–confinement. Plasma lactate levels were not significantly different from pre–stress levels 48 h after confinement. As no difference exists in primary and secondary stress responses of Atlantic salmon of differing ploidy status, it is unlikely that differences in mortality rates between diploid and triploid populations under commercial conditions can be attributed to differences in their physiological responses to periods of stress lasting up to 6 h.

Muscle growth and development in normal-sex-ratio and all-female diploid and triploid Atlantic salmon.

Muscle development and growth were investigated in diploid populations of normal-sex-ratio and all-female Atlantic salmon (Salmo salar L.) and their triploid counterparts produced by high-pressure treatment. Somites were formed at the rate of 6 h-1 in both diploids and triploids at 6 degrees C. The rostral-to-caudal development of myotubes, myofibrils and acetylcholinesterase staining at the myosepta was slightly more advanced in triploid than in diploid fish, although the differences were smaller than among individual families. The c-met receptor tyrosine kinase was used as a molecular marker for the satellite cells involved in postembryonic muscle growth. Satellite cell nuclei comprised 17.5 % of total myonuclei in smolts and they were 24 % more abundant in diploid than in triploid fish. Cells expressing the myogenic regulatory factor myf-6, a marker of satellite cells committed to differentiation, represented 14.8 % of total myonuclei in diploids and 12.5 % in triploids. At ambient temperatures, the number of white muscle fibres in normal-sex-ratio fish increased more than 30-fold between the alevin and smolt stages, and approximately 3.5-fold further during the first year of seawater growth. The rate of muscle fibre recruitment in seawater stages was significantly greater in diploid than in triploid fish, reaching 1162 fibres day-1 and 608 fibres day-1, respectively, in all-female groups 800 days post-hatching. For 42 cm fork-length fish, there were approximately one-third more muscle fibres per myotome in diploid than in triploid groups, 649 878 and 413 619, respectively, for all-female fish. The probability density function of muscle fibre diameters in each fish was estimated using non-parametric smoothing techniques, and the mean densities for diploids (fD) and triploids (fT) were calculated. The peak fibre diameter was approximately 20 (micro)m in all age classes, irrespective of ploidy. Distinct bimodal distributions of muscle fibre diameter were evident in all groups 775 days and 839 days post-hatching, reflecting seasonal cycles of fibre recruitment. fD and fT were compared using a non-parametric bootstrap technique and the reference band representing the null-hypothesis indicated that there was no difference with ploidy. Reference bands for normal-sex-ratio fish at 315 days and 470 days indicated that diploids had a higher percentage of smaller-diameter fibres and that triploid distributions had a thicker right-hand tail. Similar differences in fD and fT of muscle fibre diameters were found for all-female fish, although the statistical evidence was less strong. Reference bands indicated differences in the middle range of the distributions of muscle fibre diameter in fish 620-775 days post-hatch, with triploids having a thicker right-hand tail. Thus, a lower density of satellite cells was associated with reduced rates of fibre recruitment but a compensatory increase in muscle fibre hypertrophy in triploid compared with diploid fish.

Comparisons of cultured triploid and diploid Atlantic salmon (Salmo salar L.)

The use of sterile, triploid salmon for aquaculture would be an effective method of preventing genetic interactions between cultured and wild salmon. The studies presented in this paper compare the performance of six year classes of triploid and diploid salmon in freshwater and seawater stages of commercial production. Freshwater growth was comparable between triploids and diploids. Freshwater survival was also similar between triploids and diploids except that survival was lower in the triploids for the developmental interval between fertilization and first feeding. In sea water, triploids performed better than diploids in terms of growth. However, survival was lower in triploids and they showed a higher incidence of jaw deformities. In summary, the overall yields of triploids was lower than diploids under culture conditions.

The feeding response of diploid and triploid Atlantic salmon and brook trout

Pair and group experiments were conducted to determine whether differences exist in feeding success between juvenile diploid and triploid salmonids in a competitive situation. In the pair experiments, 22 pairs (one diploid and one triploid) of size-matched Quebec-strain brook trout Salvelinus fontinalis (7·2–46·3 g) were fed an unlimited number of pellets three times a day for 5 days. Dominance was assigned to the fish which ate the most pellets within each pair. In the group experiments, groups of three diploid and three triploid size-matched fish were fed a restricted ration three times a day for 5 days. Hierarchical rank within the group was assigned based on the number of pellets consumed by each fish. The group experiment was repeated 10 times with Atlantic salmon Salmo salar (5·1–62·7 g), Quebec-strain brook trout (11·8-110·8 g), and large UNB-strain brook trout (18·2–33·0 g), and 12 times with smaller UNB-strain brook trout (0·6–2·0 g). A statistically significant difference in rank between ploidies was found only for the smaller UNB-strain brook trout in the group experiments, with diploids dominant over triploids. This suggests that there may be a difference in competitive feeding success between diploid and triploid brook trout early in development, but that this difference diminishes as the fish grow.

The feeding response of diploid and triploid Atlantic salmon and brook trout

Pair and group experiments were conducted to determine whether differences exist in feeding success between juvenile diploid and triploid salmonids in a competitive situation. In the pair experiments, 22 pairs (one diploid and one triploid) of size-matched Quebec-strain brook trout Salvelinus fontinalis (7·2–46·3 g) were fed an unlimited number of pellets three times a day for 5 days. Dominance was assigned to the fish which ate the most pellets within each pair. In the group experiments, groups of three diploid and three triploid size-matched fish were fed a restricted ration three times a day for 5 days. Hierarchical rank within the group was assigned based on the number of pellets consumed by each fish. The group experiment was repeated 10 times with Atlantic salmon Salmo salar (5·1–62·7 g), Quebec-strain brook trout (11·8-110·8 g), and large UNB-strain brook trout (18·2–33·0 g), and 12 times with smaller UNB-strain brook trout (0·6–2·0 g). A statistically significant difference in rank between ploidies was found only for the smaller UNB-strain brook trout in the group experiments, with diploids dominant over triploids. This suggests that there may be a difference in competitive feeding success between diploid and triploid brook trout early in development, but that this difference diminishes as the fish grow.

Q4 4:30 The comparison of some non-specific immune parameters in diploid and triploid atlantic salmon

Q4 4:30 The comparison of some non-specific immune parameters in diploid and triploid atlantic salmon

Saltwater performance of triploid Atlantic salmon Salmo salar L. brown trout Salmo trutta L. hybrids

Saltwater performance of triploid Atlantic salmon Salmo salar L. brown trout Salmo trutta L. hybrids

Saltwater performance of triploid Atlantic salmon Salmo salar L. x brown trout Salmo trutta L. hybrids

Survival and growth in a saltwater net-pen of sexually immature triploid Atlantic salmon Salmo salar L. brown trout Salmo trutta L. hybrids was comparable to that of immature diploid Atlantic salmon. Following 17 months of freshwater rearing, the experimental fish were individually tagged and transferred to a saltwater net-pen where they were raised communally for 376 days. Initial and final average weights were 158 and 760 g per fish for the diploid Atlantic salmon and 209 and 1010 g per fish for the triploid hybrids; weights for the hybrids were significantly larger in both cases (α= 0.05). Survival from transfer to harvest was 43% for the Atlantic salmon and 48% for the hybrids. Average specific growth rate of fish which survived to harvest was 0.42% day-1 for Atlantic salmon and 0.41% day-1 for hybrids; these values were not significantly different. No significant differences were observed in average condition factor and dress-out percentage between crosses. Average gonadal weights and gonadosomatic indices were not significantly different for male diploid Atlantic salmon, female triploid hybrids and male triploid hybrids, but were significantly greater for female Atlantic salmon.

The performance of all‐female diploid and triploid Atlantic salmon smolts on transfer together to sea water

On transfer to sea water for 45 days, the return of appetite was later and growth rates tended to be lower for triploid Atlantic salmon, Salmo salar, reared together with diploid Atlantic salmon. All mortalities comprised of triploid salmon (29%) and were attributable to failed smolt syndrome. No correlation was found between the growth of diploid or triploid fish in fresh water and their subsequent growth on transfer to sea water.

The performance of all-female diploid and triploid Atlantic salmon smolts on transfer together to sea water

The performance of all-female diploid and triploid Atlantic salmon smolts on transfer together to sea water

Saltwater performance of all-female triploid Atlantic salmon

Survival and growth in a saltwater net-pen was compared between sexually immature all-female diploid and triploid Atlantic salmon ( Salmo salar). All-female fish were produced using sperm from sex-reversed gynogenetic males and triploidy was induced by heat shock. At 17 months post-initiation of feeding, fish larger than 60 g were individually tagged and transferred to a saltwater net-pen where they were reared communally for 376 days. Survival from transfer to harvest was 65% for diploids and 40% for triploids, the difference between ploidy groups having occurred primarily during the 3.5 month period following transfer. Initial average weights of diploids and triploids at stocking were 112 and 103 g per fish, respectively; these values were not significantly different (α = 0.05). Average final weights were 766 and 679 g per fish for diploids and triploids, respectively; these values were significantly different between ploidy groups ( P < 0.01). However, specific growth rates calculated for individual fish identified at harvest and averaged within ploidy groups did not differ significantly (0.52% per day and 0.49% per day, respectively). Average condition factor of fish at stocking was significantly lower for diploids than for triploids (0.98 and 1.02, respectively; P < 0.001), and was significantly greater for diploids at harvest (0.90 and 0.83, respectively; P < 0.001). In summary, triploid all-female Atlantic salmon appeared to require a larger size to complete smoltification, and to grow comparably to or slightly slower than diploids.