Survey of yellowfin tuna in the west-central Indian Ocean was conducted on board of Chinese longliners during 2003,2004 and 2005,which is a part of Chinese Tuna Fishery Scientific Observer Program(CTFSOP) . The reprod...Survey of yellowfin tuna in the west-central Indian Ocean was conducted on board of Chinese longliners during 2003,2004 and 2005,which is a part of Chinese Tuna Fishery Scientific Observer Program(CTFSOP) . The reproductive biology has been investigated. A total of 1 023 samples are collected including 417 ovaries and 606 testes. Spawning activities of yellowfin tuna have been studied for both male and female from January to June. The data showed that the average monthly sex ratio is 0.59,and the minimum length at sexual maturity is 101 cm for female and 110 cm for male respectively. Length at 50% sexual maturity is esti-mated at 113.77 cm for female and 120.20 cm for male,whereas maturation rate is 0.066 cm-1 for female and 0.091 cm-1 for male. Sex ratio by length class indicates that the proportion of male is higher than female's along with size increasing;for instance,in the group of the body length longer than 145 cm,some females have their body length from 145 to 160 cm and males have their body length at 160 cm and even longer. Statistically,yellowfin tuna has a significant seasonal reproduction.展开更多
Detailed petrographic,geochemical(O-C-Sr isotopes)and fluid inclusion studies of the deeply buried Cambrian carbonates in the West-central Tarim Basin revealed three types of crystalline dolomites(fine-crystalline,non...Detailed petrographic,geochemical(O-C-Sr isotopes)and fluid inclusion studies of the deeply buried Cambrian carbonates in the West-central Tarim Basin revealed three types of crystalline dolomites(fine-crystalline,nonplanar-a(s),dolomite(RD1),fine-to medium-crystalline,planar-e(s)dolomite(RD2),and medium-to coarse-crystalline,nonplanar-a dolomite(RD3)),medium-to coarsecrystalline,nonplanar-a saddle dolomite cement(CD)and early and later-stage calcite cement.The occurrence of RD1 along low-amplitude stylolites points to link with pressure dissolution by which minor Mg ions were likely released for replacive dolomitization during early-to intermediate-burial seawater dolomitization.The increasing crystal sizes of RD2 and RD3 with irregular overgrowth rims suggests intense recrystallization and replacement upon the RD1 or remaining precursor limestones by dolomitizing fluids during late intermediate burial dolomitization.The overlap ofδ^(18)O,δ^(13)C and ^(87)Sr/^(86)Sr values of RD1-RD3 and CD dolomite with coeval seawater values,suggests that the principal dolomitizing fluids that precipitated these dolomites was connate(Cambrian)seawater preserved in the host limestones/dolomites.Their high ^(87)Sr/^(86)Sr ratios suggest influx of radiogenic strontium into the Cambrian seawater.Two regimes of fluid flow are recognized in the study area:firstly,influx of magnesium-rich higher-temperature basinal brines along deep-seated faults/fractures,resulting in cementation by CD dolomite.Secondly,the incursion of meteoric waters,mixing with ascending highertemperature basinal brines,and an increase in Ca^(2+)/Mg^(2+)ratio in the fluids probably results in the precipitation of calcite cement in vugs and fractures.展开更多
文摘Survey of yellowfin tuna in the west-central Indian Ocean was conducted on board of Chinese longliners during 2003,2004 and 2005,which is a part of Chinese Tuna Fishery Scientific Observer Program(CTFSOP) . The reproductive biology has been investigated. A total of 1 023 samples are collected including 417 ovaries and 606 testes. Spawning activities of yellowfin tuna have been studied for both male and female from January to June. The data showed that the average monthly sex ratio is 0.59,and the minimum length at sexual maturity is 101 cm for female and 110 cm for male respectively. Length at 50% sexual maturity is esti-mated at 113.77 cm for female and 120.20 cm for male,whereas maturation rate is 0.066 cm-1 for female and 0.091 cm-1 for male. Sex ratio by length class indicates that the proportion of male is higher than female's along with size increasing;for instance,in the group of the body length longer than 145 cm,some females have their body length from 145 to 160 cm and males have their body length at 160 cm and even longer. Statistically,yellowfin tuna has a significant seasonal reproduction.
基金funded by the National Natural Science Foundation Project of China (Nos. 41372126 and 41772103)National Science and Technology Major Project of China (No. 2016ZX05007-002)Natural Science Foundation Innovation Group Program of Hubei Province (No. 2015CFA024)
文摘Detailed petrographic,geochemical(O-C-Sr isotopes)and fluid inclusion studies of the deeply buried Cambrian carbonates in the West-central Tarim Basin revealed three types of crystalline dolomites(fine-crystalline,nonplanar-a(s),dolomite(RD1),fine-to medium-crystalline,planar-e(s)dolomite(RD2),and medium-to coarse-crystalline,nonplanar-a dolomite(RD3)),medium-to coarsecrystalline,nonplanar-a saddle dolomite cement(CD)and early and later-stage calcite cement.The occurrence of RD1 along low-amplitude stylolites points to link with pressure dissolution by which minor Mg ions were likely released for replacive dolomitization during early-to intermediate-burial seawater dolomitization.The increasing crystal sizes of RD2 and RD3 with irregular overgrowth rims suggests intense recrystallization and replacement upon the RD1 or remaining precursor limestones by dolomitizing fluids during late intermediate burial dolomitization.The overlap ofδ^(18)O,δ^(13)C and ^(87)Sr/^(86)Sr values of RD1-RD3 and CD dolomite with coeval seawater values,suggests that the principal dolomitizing fluids that precipitated these dolomites was connate(Cambrian)seawater preserved in the host limestones/dolomites.Their high ^(87)Sr/^(86)Sr ratios suggest influx of radiogenic strontium into the Cambrian seawater.Two regimes of fluid flow are recognized in the study area:firstly,influx of magnesium-rich higher-temperature basinal brines along deep-seated faults/fractures,resulting in cementation by CD dolomite.Secondly,the incursion of meteoric waters,mixing with ascending highertemperature basinal brines,and an increase in Ca^(2+)/Mg^(2+)ratio in the fluids probably results in the precipitation of calcite cement in vugs and fractures.
