Morten Rye

Survival in early life of Atlantic salmon and rainbow trout: estimates of heritabilities and genetic correlations

Abstract Survival data obtained for offspring of 187 sires and 1404 dams of Atlantic salmon (eight year classes of data) and 213 sires and 1062 dams of rainbow trout (nine year classes) were analysed. Over year classes, average survival rates in the observation periods (during incubation and the early fresh water phase) ranged from 48% to 98%, being lowest in the period before the eyed-egg stage and during first feeding. In both species, heritabilities for survival derived from the sire components of variance were low (0.04–0.09). Heritabilities derived from the dam components of variance ranged from medium to high (0.31–0.87), indicating non-additive genetic and/or common environmental effects. Genetic correlations between survival in two succeeding periods were all, except one, positive and medium in magnitude (0.18–0.46). Genetic correlations between survival in non-succeeding periods were in general low and non-significant. Significant positive correlation between long-term survival and growth rate was found in Atlantic salmon (0.37). The corresponding correlation in rainbow trout was also positive (0.23), but not significantly different from zero.

Prediction of carcass composition in Atlantic salmon by computerized tomography

Abstract The prediction of carcass composition of Atlantic salmon (Salmo salar) using computerized tomography (CT) data was examined. 174 fish were included in the study, and prediction equations derived by multiple linear regression (MLR) and principal component regression (PCR) were evaluated. Validation of alternative equations was done according to the relative standard error of prediction (SEP/SD), relative mean prediction error (BIAS/SD) and the correlation between chemically determined and predicted values. The potential of the CT technique for accurate and fairly unbiased predictions of percentage fat and dry matter in salmon carcasses was clearly demonstrated. SEP/SD of about 0.40, BIAS/SD less than 0.10 percentage units and a correlation between observed and predicted values of 0.92 for both compositional components were obtained for the best prediction equations. A significant prediction of protein content was not obtained. The accuracy of predicting fat and dry matter content was improved by 38% by using CT data instead of the simple carcass measurements gutted body weight and condition factor. The impact of the results on a breeding program for quality-related traits in farmed Atlantic salmon is discussed.

Family association between immune parameters and resistance to Aeromonas hydrophila infection in the Indian major carp, Labeo rohita.

Seven innate immune parameters were investigated in 64 full-sib families (the offspring of 64 sires and 45 dams) from two year-classes of farmed rohu carp (Labeo rohita). Survival rates were also available from Aeromonas hydrophila infection (aeromoniasis) recorded in controlled challenge tests on a different sample of individuals from the same families. Due to strong confounding between the animal additive genetic effect and the family effects (common environmental+non-additive genetic), reliable additive (co)variance components and hence heritabilities and genetic correlations could not be obtained for the investigated parameters. Therefore, estimates of the association of challenge test survival with the studied immune parameters were obtained as product moment correlations between family least square means. These correlations revealed statistically significant (p<0.05) negative correlations of survival with bacterial agglutination titre (-0.48), serum haemolysin titre (-0.29) and haemagglutination titre (-0.34); and significant positive correlation with ceruloplasmin level (0.51). The correlations of survival to aeromoniasis with myeloperoxidase activity, superoxide production and lysozyme activity were found to be not significantly different from zero (p>0.05). Assuming that the negatively correlated candidate traits are not favourable as indirect selection criteria, the results suggest that ceruloplasmin level could potentially be a marker for resistance to aeromoniasis in rohu. The use of this immune parameter as an indirect selection criterion for increased resistance to aeromoniasis in rohu will, however, require that the parameter shows significant additive genetic variation and a significant genetic correlation with survival. Further studies are therefore needed to obtain a reliable heritability estimate for ceruloplasmin and its genetic correlation with survival from aeromoniasis.

Growth and survival in two complete diallele crosses with five stocks of Rohu carp (Labeo rohita)

Abstract The experiment of two 3×3 complete diallele crosses was carried out with four wild river stocks (Ganga, Yamuna, Brahmaputra and Sutlej) and one farmed stock (Local) of Rohu carp ( Labeo rohita ). The Local stock was included in both diallele crosses. In total, 864 fish were individually tagged at 6 months of age and reared for 14 months in three monoculture and two polyculture earthen ponds in Orissa, India. For harvest weight, total heterosis for each of the six stock crosses was low or negative and average heterosis was also low and in most cases not significantly different from zero. For survival, total and average heterosis was negligible and not significantly different from zero. It is concluded that genetic improvement through crossbreeding of Indian stocks of Rohu carp has little practical significance.

Effects of temperature on yolk sac larvae of Atlantic halibut (Hippoglossus hippoglossus L.)

Abstract Larvae of Atlantic halibut were incubated at five different temperatures (4, 6, 8, 10 and 12 °C) from hatching onwards (Experiment 1), and at 4 °C for a period of 0, 10, 20, 30 or 40 days before the temperature was increased to 6 °C or 8 °C (Experiment 2). Both experiments were terminated at time of first feeding, 230 day-degrees (d °) after hatching. In Experiment 1, larval survival was significantly lower at 12 °C, and the yield of normally developed larvae dropped significantly when larvae were incubated at 6 °C or higher. When larvae were incubated for different periods at 4 °C (Experiment 2), the number of days at 4 °C had a significant effect on larval survival and the frequencies of functional larvae, jaw deformations and yolk sac oedema, while the temperatures in the second period (6 °C or 8 °C) had no significant effect on the same traits. Frequency of normally developed larvae increased with increasing number of days at 4 °C while the survival rate tended to decrease with increasing number of days at 4 °C. Myotomal height, larval dry weight, yolk sac volume and feeding incidence were less influenced by the incubation temperature in both experiments. The results demonstrated that the development of abnormalities like gaping jaws and yolk sac oedema in halibut yolk sac larvae can be associated with high temperatures and presence of different temperature tolerances at different developmental stages.

Selection for improved resistance to Aeromonas hydrophila in Indian major carp Labeo rohita: survival and innate immune responses in first generation of resistant and susceptible lines.

Selection for disease resistance in fish may be performed directly on basis of survival data obtained in controlled challenge trials, or indirectly using information from immunological or molecular markers linked to differential survival. In the present study, several key innate immune parameters were measured in aeromoniasis resistant and susceptible lines of rohu Labeo rohita to assess their suitability as immune markers for use in indirect selection for increased resistance. Experimental infection with Aeromonas hydrophila (9.55 × 10(6) cfu g(-1) fish) through the intraperitoneal route produced higher survival in the resistant line (73.33%) as compared to the susceptible line (16.67%). Blood and liver tissue samples from both lines were collected to study some of the innate immune parameters and immune-related gene expression. The respiratory burst activity of blood phagocytes, serum myeloperoxidase activity and ceruloplasmin level were significantly (p < 0.05) higher in the resistant line compared to the susceptible line. Lower level of blood glucose and serum natural haemolysin titre were marked in the resistant line as compared to the susceptible line. No significant difference was measured in total serum protein concentration, antiprotease activity and bacterial agglutinin level between two lines, while the expression of transferrin, complement factor C3 and TLR 22-like transcripts were significantly (P < 0.05) higher in liver samples of the susceptible line. However, no such difference was found in β(2)-microglobulin and lysozyme gene expression between lines. The study demonstrated the possibility of using some of the investigated innate immune parameters as indirect marker traits for selection for improved resistance to aeromoniasis in rohu.

Growth and survival of six stocks of rohu (Labeo rohita, Hamilton) in mono and polyculture production systems

One farmed stock (Local) and five riverine stocks of Rohu (Labeo rohita, Hamilton) from 2-year classes (1993 and 1994) were evaluated for growth and survival under monoculture and polyculture systems at the Central Institute of Freshwater Aquaculture (CIFA), India. In the 1993 year-class, 29 full-sib groups of Local and 28 full-sib groups of river Ganga were tested while in the 1994 year-class the stocks tested were of Local and of rivers Brahmaputra, Ganga, Gomati, Sutlej and Yamuna with 6, 8, 7, 7, 18 and 11 full-sib groups, respectively. For each year-class, individually tagged fingerlings were stocked into three 0.1 ha monoculture ponds (9 fish/full-sib group/pond) and two 0.4 ha polyculture ponds (13 fish/full-sib group/pond). In polyculture, Rohu were stocked together with Catla (Catla catla, Hamilton) and Mrigal (Cirrhinus mrigala, Hamilton) in the ratio of 1.2:1:1, respectively. The stock effect on body weight at harvest was not significant in the 1993 year-class but highly significant in the 1994 year-class. The stock effect on survival from tagging to harvest was not significant in any of the year-classes. The interaction between production system and stock on growth and survival was significant but low, particularly compared to the significant and important full-sib effect. Thus, the growth performance of the stocks was relatively consistent in monoculture and polyculture. The significant full-sib effects for growth and survival suggest that these traits can be improved through selective breeding. The implications of the results for the development of a selective breeding program for Rohu in India are discussed.

Genetic variation in mineral absorption of large Atlantic salmon (Salmo salar) reared in seawater

Abstract Apparent absorption coefficients (AACs) of mineral elements (K, Na, Cu, Ca, Mg, Zn, Fe, Mn, P) were studied in 82 full-sib family groups of individually tagged Atlantic salmon (41 sires, 2 dams per sire, 7–27 fish per family), with an average weight of 4.6 kg. The fish were kept in one net-pen in seawater and fed a diet with Y2O3 as the inert marker. Faeces were obtained by stripping and pooled for each family. The mean AACs (%) of elements and ash were: K, 97.5; Na, 23.8; Cu, 55.9; Ca, −11.7; Mg, −260; Zn, 37.9; Fe, 23.8; Mn, 7.6; P, 40.4 and ash, 16.6. Differences between paternal half-sib families were significant (P