Incidence Of Sexual Maturation Research Articles

Efficacy of 24 h light to reduce maturation in Arctic charr (Salvelinus alpinus) is dependent on both the start date and duration

Two lab-based trials quantified the effect of a range of continuous light (LL) treatments overwinter on the somatic growth and incidence of sexual maturation in the fall age 2 of individually identified under-yearling Arctic charr (Labrador strain) at constant 10°C. Controls were maintained under simulated natural photoperiod (LDN; Latitude 45°N). In trial 1 (n=120/trt, mean 54g initial body weight), LL starting the 1st day of either October, November, December, January or February (all returned to LDN on April l) resulted in a step-wise reduction in maturity of 43, 55, 59, 67 73% compared with 77% in the control (sexes pooled). In trial 2 (n=90/trt, mean 24g initial body weight), LL starting either August 13 or October 1 and ending April 1 reduced maturity to <10%, compared to 33% (LL Dec1-Apr1) and 50% in the LDN controls. LL starting October 1 and ending either February 1, April 1 or June 1 were equally effective, resulting in <15% maturity. The importance of returning from LL to LDN in spring to reduce maturity was demonstrated by the LL constant (Oct–Oct) treatment which resulted in relatively high maturity, 31%. The reduction of maturity rate was independent of both somatic growth and condition factor during winter in all treatment groups. Among fish that matured, the timing of completion of sexual maturation was affected by both the LL start and end date.

Vaccination and elevated dietary phosphorus reduces the incidence of early sexual maturation in Atlantic salmon (Salmo salar L.)

This study investigated the effect of ip injection of an oil-adjuvant vaccine and dietary phosphorus (P) level on the incidence of sexual maturation and occurrence of skeletal deformities in Atlantic salmon. Triplicate groups (12×12m sea cages) of vaccinated (V) and unvaccinated (UV) Atlantic salmon underyearling smolts were fed diets with 0.6% (0.6P) or 0.9% available phosphorus (0.9P) from seawater transfer in mid-October and 3months onwards, and then a commercial diet for a further 11months. Both vaccination and 0.9% available phosphorus significantly increased the proportion of immature fish. V significantly reduced the incidence of mature females, while 0.9P significantly reduced the incidence of mature males. In addition, there were always relatively fewer mature V than UV males within each of the six sea-cages (three per diet). At the end of the period on different test diets, fish fed the 0.6P diet displayed significantly lower mechanical stiffness of the vertebral bodies than fish fed the 0.9P diet, but the mean values were both relatively high, which indicated that both groups enjoyed good mineral status. There was no effect of vaccination on stiffness, and there were no dietary or vaccination effects on the occurrence of externally detectable skeletal deformities (vertebral column, operculum, jaw).This is the first study to show that dietary phosphorus and vaccination can influence sexual maturation in fish. The results show that early seawater diets for underyearling Atlantic salmon smolts must be sufficient in phosphorus to prevent unwanted sexual maturation during on-growth in seawater.

Body weight, sexual maturity, and spinal deformity in strains and families of Atlantic cod (Gadus morhua) at two years of age at different locations along the Norwegian coast

Abstract Body weight, occurrence of spinal deformity, and sexual maturity were recorded in 51 full-sib families of the strains coastal and Arctic cod at two years of age. The family groups were located at three sites along the Norwegian coast including Hordaland, Møre and Romsdal (M&amp;R), and Nordland County to detect genetic variation in important production traits and to investigate interactions between genetic composition and production environment. Body weight varied among locations partly owing to different production conditions. There were also large differences among the locations with respect to spinal deformity. M&amp;R had the highest occurrence of spinal deformity (p &lt; 0.001). Comparison of sexual maturity among the locations was made difficult owing to the different ways the trait was recorded. Only small differences were found between coastal and Arctic cod in spinal deformity (p &lt; 0.05 in Hordaland) and sexual maturity (p = 0.06 in M&amp;R), while no differences were found for body weight. Heritability estimates for body weight (0.51), spinal deformity (0.27), and sexual maturity (0.21) indicate the potential for improvement of all three traits by selective breeding using a family-based selection programme. Final recordings at the end of the growing period will provide further information. Genetic correlations estimated between weight and occurrence of spinal deformity (rg = 0.50) suggest that caution be used when selecting for growth, and that a need exists for including spinal deformity in the selection index. No significant correlations were found between these two traits and the incidence of sexual maturity.

Photoperiod in seawater influence seasonal growth and chemical composition in autumn sea-transferred Atlantic salmon ( Salmo salar L.) given two vaccines

Despite gains in commercial salmonid aquaculture production by using underyearling smolts (0+), poor performance in seawater has been noted. This study assesses how artificial photoperiods in seawater may improve the performance. Seawater-transferred 0+ Atlantic salmon were exposed to natural light (NL) or continuous light (LL) from October to midsummer, or to LL from October to January followed by natural light (LL–NL), or NL from October to January and then LL to midsummer. All fish experienced natural light after midsummer. The photoperiods changed the seasonal growth pattern and harvest weights became significantly different (LL: 3445 ± 46 g; NL–LL: 3207 ± 45 g; LL–NL: 3092 ± 56 g; NL: 2854 ± 42 g). Growth of NL fish decreased from autumn through winter and increased in spring. LL fish grew better than NL fish until spring and was 21% heavier at slaughter. Switching from LL to NL in January reduced growth rate from March onwards to a level slightly lower than the seasonal growth pattern of the NL fish. The onset of light in January (NL–LL) resulted in a temporary decrease in growth for 7 weeks followed by a major weight increase with growth rate being significantly higher than LL fish from late April until October. NL–LL fish never managed to catch up with the LL fish, but were significantly larger than the NL fish. Changes in condition factor with light treatment demonstrated clearly the photoperiodic influence on the seasonal growth pattern. Two vaccines were used in all photoperiods. The fish given the vaccine that gave least adherences (lesion score 1.8 vs. 2.3) became 20% heavier than those given the other vaccine, and no interaction between photoperiod and vaccine was observed. Muscle lipid and astaxanthin contents in June were highest in LL fish (lipid: 9.1%; astaxanthin: 4.4 mg kg − 1 ) and lowest in NL fish (lipid: 4.1%; astaxanthin: 2.6 mg kg − 1 ). These differences largely disappeared by November, although fish exposed to light following seawater transfer (LL and LL–NL) had a tendency to contain higher levels of astaxanthin than those on natural light (NL and NL–LL). Both lipid and astaxanthin contents in fillet correlated positively with fish weight. The incidence of sexual maturation was 4% in LL and LL–NL, 1.5% in NL and 0% in NL–LL. In the seawater-phase of underyearling autumn-transferred smolts, we recommend using the NL–LL photoperiod regime. This light treatment gave a slightly smaller fish than LL at harvest, but there were no losses due to sexual maturation.

Suppression of maturation in 2-year-old Chinook salmon ( Oncorhynchus tshawytscha) reared under continuous photoperiod

We investigated the effect of 24-h photoperiod (LD24:0) on the incidence of sexual maturation in freshwater-reared, 2-year-old Chinook salmon by supplying artificial lighting throughout the second year of life, from 1 May (austral autumn) to 10 April the following year. Our study populations comprised one group of monosex females, on which most New Zealand salmon aquaculture is based, and one group of mixed-sex fish. Maturation was completely suppressed in both groups of females under LD24:0, but averaged 25% and 3.6% in monosex and mixed sex female controls, respectively. Maturation was also strongly suppressed in males, being at most 7% (including some individuals which may have previously matured as yearlings) under LD24:0 compared to 90% in the controls. At age 2, mature females were longer and heavier than immature females, but after adjusting for differences between mature and immature fish neither mean fork length, total weight, nor somatic weight differed between the LD24:0 and control groups. Fish subjected to LD24:0 tended to have higher condition factors than the controls, particularly from spring to early summer. Our results contrast with an earlier study in which LD24:0 initiated on 30 August (austral late winter) had no effect on the incidence of maturation in 2-year-old Chinook females, suggesting that the onset of maturation is linked to seasonal photoperiod signals during autumn and winter.

Long-to-short photoperiod in winter halves the incidence of sexual maturity among Arctic charr

To better understand how photoperiod and body size interact to affect age at maturity, PIT-tagged 2-year-old Salvelinus alpinus (ca. 300 g, n=330) were reared in fresh water from February 3 under four treatments, either 18-h light/6-h dark (LD18:6) for 42 days then LD8:16 (long–short); LD18:6 for 42 days then simulated natural (long–ambient); constant LD18:6 (constant–long); or simulated seasonal photoperiod cycle (control). Temperature was 10 °C. In November, the incidence of maturity in the long–short treatment was reduced to 44% among males and 20% among females, compared to 83% and 50% in the control (p 1 kg and immature) by over four-fold. The long–ambient treatment also reduced maturation (p<0.05), but to a lesser degree, 66% and 32% in the respective sexes. The constant–long treatment had no effect on males and increased maturation among females. The arrest of sexual maturation was associated with a marked alteration in seasonal pattern of growth suggesting it was due to a suppression of somatic growth. By contrast, initial body size and condition factor were poor indicators of incipient maturing fish.

Deferred costs of compensatory growth after autumnal food shortage in juvenile salmon.

Growing animals are often able to offset the effects of periods of reduced food availability by subsequently undergoing a phase of elevated compensatory or 'catch-up' growth. This indicates that growth rates are not normally maximized even when food is not limiting, suggesting that fast growth may be costly. Here, we show experimental evidence of a long-term deferred cost of compensatory growth after a period of food shortage. Juvenile salmon subjected to a short-lived low-food regime in autumn subsequently entered a hyperphagic phase, leading to complete restoration of lipid reserves and partial recovery of lost skeletal growth relative to controls. However, several months later they entered a prolonged phase of poorer performance (despite food now being freely available), so that by the following spring they were substantially smaller than controls and had lower lipid reserves for their body size. The incidence of sexual maturation in males the following breeding season was also reduced. Salmon thus appear to trade off the benefits of short-term restoration of fat stores prior to winter against long-term performance.

Growth, osmoregulation and sexual maturation of underyearling Atlantic salmon smolt Salmo salar L. exposed to different intensities of continuous light in sea cages

Atlantic salmon smolts are usually transferred to sea water during early spring, but photoperiod treatment can be used to produce underyearling (0+) smolts for transfer to sea water in late autumn, 7–8 months earlier than usual. This study investigated the effect of exposure to additional continuous light (LL) of different intensities on 0+ smolts after transfer to sea water. 0+ smolts transferred to sea cages in mid-October were exposed to natural light (NL) or LL of one of three intensities (low, medium or high) until January, whereupon they experienced NL until harvest in December. Fish in all groups displayed a normal ability to hypoosmoregulate, assessed by monitoring plasma chloride concentrations after transfer to sea water. No consistent differences in length, weight or condition were found between LL groups. The LL groups had greater growth in length than the NL group during the time of LL exposure, followed by an increase in weight when exposed to NL. This resulted in fish of larger size than the NL group. By August, the fish in the NL group had caught up with the LL groups in respect of length, weight and condition factors. This suggests that the LL treatment led to increased winter growth and phase-shifted a seasonal pattern of growth. The incidence of sexual maturation was low (< 1%), with no differences between groups.

Effects of growth and fatness on sexual development of chinook salmon (Oncorhynchus tshawytscha) parr

The independent effects of size and fatness, 1 year prior to maturity, on male sexual development of chinook salmon (Oncorhynchus tshawytscha) were tested. Beginning in March 1995, ration size and dietary lipid were independently manipulated to produce four groups of spring chinook salmon differing in size and fatness. Size, growth rate, adiposity, liver triacylglycerol and glycogen contents, and plasma insulin and insulin-like growth factor I (IGF-I) levels were monitored to follow the metabolic states of fish in the different treatment groups and to observe whether plasma levels of these growth mediators predict sexual development. Differences in size and fatness were well established by the first autumn (September 1995), 1 year prior to sexual maturity, and common ration size groups were pooled for further rearing. Subsequently in winter-spring (February-March), 6 months prior to sexual maturity, there were no within-tank differences in size or fatness. Nevertheless, the effects of size and fatness, from 1 year earlier, on incidence of sexual maturity were significant. Overall, size appeared to have the primary effect, but for smaller fish, an effect of fat content was indicated. Plasma insulin levels, and in limited cases, IGF-I levels, were correlated with growth rate and size, but were not accurate indicators of sexual development.

Genetic parameters of growth and sexual maturity in Arctic char ( Salvelinus alpinus)

A factorial mating system was used to study the contribution of additive genetic, non-additive genetic and maternal effects on the variation in weight, length, condition factor, specific growth rate and the incidence of sexual maturation in the Arctic char reared at two locations. Genetic correlations between characters and between locations were also studied. Additive genetic effects on length and weight estimated from the sire component of variance ranged from 0.25 to 0.62 and for sexual maturity from 0.19 to 0.45. Maternal effects and non-additive genetic effects were low on all characters compared with additive genetic effects. Genetic correlations between weight, length and condition factor were positive and high. Low positive genetic correlations between sexual maturation incidence and growth characters were found at one location and high but negative correlations at the other location. Specific growth rates of fish during October–May in different years were positively correlated. Growth rate during May–October was found to correlate poorly to the preceding October–May growth rates.

Growth and early sexual maturation in Baltic salmon (Salmo salar) parr

The relationship between sexual maturation and growth in Baltic salmon (Salmo salar) parr was studied in hatchery stock originating from the Umeälven (Ume River) in northern Sweden. The probability that a male parr would mature sexually at age 1 + was positively related to its size at the start of the experiment at age 0+. The specific growth rate and condition factor of maturing and nonmaturing males were similar until the onset of gonadal growth, when the growth rate of maturing males decreased. Sibling groups of immature parr were fed different rations during the 3 weeks prior to the start of gonadal development. The incidence of sexual maturation in the groups given different rations was linearly related to the growth rate during the period of different feeding rates. This study suggests that both the size at age 1, resulting from the growth rate during the first summer, and the opportunity for growth during the period preceding the onset of gonadal growth affect the incidence of maturation in male parr of age 1 +.

Growth, Parr–Smolt Transformation, and Changes in Growth Hormone of Atlantic Salmon (Salmo salar) Reared under Different Photoperiods

Potential 1+ smolts of Atlantic salmon (Salmo salar) were reared under three light regimes: simulated natural photoperiod (LDN), continuous light (LD24:0), or a combination of continuous, low-intensity background light and a superimposed simulated natural photoperiod (dual photoperiod, LDD). Growth rate in freshwater was enhanced by LD24:0 and LDD, and changes associated with smoking (increased salinity tolerance, reduced condition coefficient) were advanced under LD24:0. Plasma growth hormone levels were initially high on LD24:0 and LDD whereas on LDN, plasma growth hormone levels increased gradually from February through April. Overall GH levels were negatively correlated with condition coefficient during the final stages of smoking. After 16 mo in seawater, there were no significant size differences among the groups. The incidence of sexual maturation as postsmolts was higher in the LD24:0 and LDD groups whereas the incidence of grilsing was higher in LDN. Results demonstrate the significant influence of photoperiod on growth and smoking in Atlantic salmon. An abrupt increase to continuous light in winter may be sufficient to advance important aspects of the parr–smolt transformation. Dual photoperiod may be a way to combine the increased growth rate observed under continuous light and the normal parr–smolt transformation associated with natural photoperiod.

Photoperiod and its effect on incidence of sexual maturity in pink salmon (Oncorhynchus gorbuscha)

Pink salmon (Oncorhynchus gorbuscha) were reared for 15 months after fry emergence under three photoperiod regimes. About 50% of males matured in a photoperiod that had two periods of declining day length within the 15-month study period. No males matured in photoperiods having only one period of declining day length, and no females matured in any photoperiod. The rate of change of day length is likely of greater importance than the amplitude of change in inducing sexual maturation in males.

The female reproductive cycle of the octopus,Eledone cirrhosa

Changes in the relative size of the ovary, oviducal glands and eggs are described forEledone cirrhosacaptured from the North Sea off Aberdeen over a 3 year period(N= 488). The analysis is based only on freshly caught animals, excluding those held in aquarium conditions (&gt; 5 days). Ovary enlargement and egg size estimates are used as indices of sexual maturity. Between 0–15% and 18–95% of total body weight is contributed by the ovary. Maximum egg length in the ovary ranges up to 7 mm. On these criteria, sexual maturation typically occurs at body sizes between 400–1000 g although some animals of 1000–1200 g are found showing no evidence of ovary enlargement. The majority of the monthly sample is always immature but maturation can apparently occur at almost any time of the year. Increase in mean ovary index and mean values for egg size are strongly seasonal and indicate a peak incidence of sexual maturity over 2–3 months in the July-September period. Spawning is presumed to follow within 1 month. Estimates of the fecundity of the females, based on the egg sample from the ovary, range from 2·2 × 103 to 55 × 10 3 eggs with a mean of 11 × 10 3 and a mode of 7·5 × 10 3 eggs.