We collected Vimba vimba throughout the spawning season(mid April to mid June,2007) in Gorgan Bay(south-western Iran) and investigated its age,growth,and reproductive traits.The maximum age was 5+ years.Both sexes gre...We collected Vimba vimba throughout the spawning season(mid April to mid June,2007) in Gorgan Bay(south-western Iran) and investigated its age,growth,and reproductive traits.The maximum age was 5+ years.Both sexes grew allometrically(positive for males:b=3.140 9 and negative for females:b=2.791 4).The von Bertalanffy growth functions were described by the formulae Lt=32.565(1-e-0.184(t+0.530)) for males and Lt=35.950(1-e-0.179(t+0.529)) for females.The overall sex ratio was balanced,but males were predominant in the smaller size classes and females in the larger size classes.Based on the gonadosomatic index(GSI) values,spawning appears to occur between late April and late May in the bay.The highest mean GSI was 6.44 for males in early May and 20.36 for females in late April.Absolute fecundity varies from the minimum of 5 436 eggs for age 3+ fish to the maximum of 36 141 eggs for age 5+ fish.Fecundity was also positively correlated with fish size(length and weight).Egg diameter ranged from 1.05 to 1.70 mm in the mean of 1.42 mm.There was no correlation between female size and ova diameter.展开更多
The reproductive biology of bream A bramis brama(L.) was studied from 546 fish collected from the lower reaches of the Irtysh River in Xinjiang, north-west China, from March to November 2013. The overall sex ratio(M/F...The reproductive biology of bream A bramis brama(L.) was studied from 546 fish collected from the lower reaches of the Irtysh River in Xinjiang, north-west China, from March to November 2013. The overall sex ratio(M/F) was 1.06:1, and was not significantly diff erent from the theoretical 1:1 ratio( P >0.5). However, there was a dominance of males during the pre-spawning season(1.33 in March and 1.56 in April, P <0.5), while females were dominant during the peak spawning season(0.88 in June, P <0.5). The monthly variation in gonadosomatic index(GSI) and proportion of gonads at each macroscopic maturity stage, indicated that A. brama spawned once a year with peak spawning occurring from late May to June. The unimodal distribution of oocyte diameter each month indicated that A. brama is a single spawner, with a high degree of spawning synchronicity. The standard lengths(SL 50) and ages( A 50) at first maturity for males and females, were 178 and 204 mm, and 5.6 and 6.8 years, respectively. The mean absolute fecundity(AF) was 77 311 eggs per fish, and mean relative fecundity(RF) was 162 eggs per gram of body weight(BW). The AF of A. brama increased linearly with increasing of gonad weight(GW), eviscerated weight(EW) and standard length(SL), but was not significantly correlated with age. As, A. brama in the lower reaches of the Irtysh River reaches reproductive maturity relatively late in their life span, is mature for a short period and spawns in aggregations, this fish is vulnerable to overexploitation.展开更多
文摘We collected Vimba vimba throughout the spawning season(mid April to mid June,2007) in Gorgan Bay(south-western Iran) and investigated its age,growth,and reproductive traits.The maximum age was 5+ years.Both sexes grew allometrically(positive for males:b=3.140 9 and negative for females:b=2.791 4).The von Bertalanffy growth functions were described by the formulae Lt=32.565(1-e-0.184(t+0.530)) for males and Lt=35.950(1-e-0.179(t+0.529)) for females.The overall sex ratio was balanced,but males were predominant in the smaller size classes and females in the larger size classes.Based on the gonadosomatic index(GSI) values,spawning appears to occur between late April and late May in the bay.The highest mean GSI was 6.44 for males in early May and 20.36 for females in late April.Absolute fecundity varies from the minimum of 5 436 eggs for age 3+ fish to the maximum of 36 141 eggs for age 5+ fish.Fecundity was also positively correlated with fish size(length and weight).Egg diameter ranged from 1.05 to 1.70 mm in the mean of 1.42 mm.There was no correlation between female size and ova diameter.
基金Supported by the Special Funds for the Foundation Work of Science and Technology(No.2012FY112700)
文摘The reproductive biology of bream A bramis brama(L.) was studied from 546 fish collected from the lower reaches of the Irtysh River in Xinjiang, north-west China, from March to November 2013. The overall sex ratio(M/F) was 1.06:1, and was not significantly diff erent from the theoretical 1:1 ratio( P >0.5). However, there was a dominance of males during the pre-spawning season(1.33 in March and 1.56 in April, P <0.5), while females were dominant during the peak spawning season(0.88 in June, P <0.5). The monthly variation in gonadosomatic index(GSI) and proportion of gonads at each macroscopic maturity stage, indicated that A. brama spawned once a year with peak spawning occurring from late May to June. The unimodal distribution of oocyte diameter each month indicated that A. brama is a single spawner, with a high degree of spawning synchronicity. The standard lengths(SL 50) and ages( A 50) at first maturity for males and females, were 178 and 204 mm, and 5.6 and 6.8 years, respectively. The mean absolute fecundity(AF) was 77 311 eggs per fish, and mean relative fecundity(RF) was 162 eggs per gram of body weight(BW). The AF of A. brama increased linearly with increasing of gonad weight(GW), eviscerated weight(EW) and standard length(SL), but was not significantly correlated with age. As, A. brama in the lower reaches of the Irtysh River reaches reproductive maturity relatively late in their life span, is mature for a short period and spawns in aggregations, this fish is vulnerable to overexploitation.
