The mitre squid(U roteuthis chinensis) and the swordtip squid( U. edulis) are Indo-Pacific cephalopod species that are abundant in the western Pacific Ocean. They are currently exploited in the East and South China Se...The mitre squid(U roteuthis chinensis) and the swordtip squid( U. edulis) are Indo-Pacific cephalopod species that are abundant in the western Pacific Ocean. They are currently exploited in the East and South China Seas and make up a significant portion of the Chinese neritic squid catch. Beaks, the feeding organs of squid, are important for individual size and biomass estimation because of their high resistance to degradation in predator stomachs and consistent dimensions. In this study, 104 U. chinensis and 143 U. edulis individuals were sampled from northern South China Sea with mantle length from 70 to 260 mm and 96 to 284 mm, respectively. The results indicated that morphological beak values were greater for U. edulis, compared to U. chinensis, for upper hood length(UHL), upper crest length(UCL), upper lateral wall length(ULWL), lower crest length(LCL), and lower lateral wall length(LLWL). According to principal component analysis, UHL/ML, UCL/ML, ULWL/ML, LCL/ML, LLWL/ML and LWL/ML could represent the characteristics of beaks for U. chinensis, while UHL/ML, UCL/ML, ULWL/ML, LHL/ML, LCL/ML and LLWL/ML could represent it for U. edulis. According to Akaike's information criterion(AIC) values, a power function was the most suitable model for U. chinensis, while a linear function was the most suitable model for U. edulis. The beak variable-mantle length ratio(beak variable/mantle length) declined with the increasing of mantle length and declined sharply at the early stage of growth in both beaks and species. The ratio changed quickly after achieving the mantle length of 140 mm for U. chinensis, while the ratio changed quickly after 170 mm for U. edulis. Beaks in both species experienced sharper changes through maturity stage I to II than other maturity stages. This study gives us basic beak morphology information for U. chinensis and U. edulis in the East and South China Seas. Geometric morphological methods combined with dietary analysis should be used in the future.展开更多
Swordtip squid(Uroteuthis edulis)is one of the important economical fishing target species in the East China Sea.Uroteuthis edulis is characterized by rapid growth,extensive migration,and long spawning period and sens...Swordtip squid(Uroteuthis edulis)is one of the important economical fishing target species in the East China Sea.Uroteuthis edulis is characterized by rapid growth,extensive migration,and long spawning period and sensitive to surrounding environment.In order to assess its stock status,it is necessary to explore its spawning season,growth patterns of different populations and their relationship with the environment in advance.In this paper,based on the samples of U.edulis collected in the East China Sea from September 2017 to March 2018,we explored the relationships between daily growth of statolith microstructure and environmental variables by gradient forest method and generalized additive model.The spawning season of U.edulis was found to be nearly one year,and two dominant season groups were found:the spring group with the peak period of April and the summer group with the peak period of August.Water temperature in the depth of 25 m(Temp_25),sea surface temperature(SST)and zonal velocity were the key environmental variables for the daily growth of April-spawning group.The most suitable environmental conditions for the growth of April-spawning group were water temperature(24-27℃)and velocity(0.1-0.3 m/s).SST,Temp_25 and mixed layer depth were the key environment variables for the daily growth of August-spawning group.The most suitable environmental conditions for the growth of Augustspawning group were water temperature(21-28℃)and water depth(0-50 m).Key environmental variables of different groups suggested that early growth was significantly affected by seasonal changes of water temperature,current velocity and prey abundance.This study explored the relationships between early growth and environmental variables and provided the scientific guidance for the management and conservation of U.edulis.展开更多
To determine the age and growth of Uroteuthis chinensis and U.edulis,growth increments of the lateral dome of the statolith were used in the present study.Specimens of the two species caught in the South China Sea(SCS...To determine the age and growth of Uroteuthis chinensis and U.edulis,growth increments of the lateral dome of the statolith were used in the present study.Specimens of the two species caught in the South China Sea(SCS)and East China Sea(ECS)were used to compare the age and growth differences between sexes.In the present study,we found the two species have similar lifespans of less than 200 days.We also found that there were significant differences in the relationships between mantle length and body weight for two species and for both sexes in the same species.The back-calculated hatching date for the two species was similar,i.e.October to January for specimens caught in spring,and March to June for specimens caught in summer(U.edulis)or autumn(U.chinensis).Exponential and logistic growth curves were fitted to build the age and mantle length relationship.Both growth curves showed that U.chinensis has a larger mantle length than U.edulis at the same age.The results of the growth rates also showed that U.chinensis grows faster than U.edulis.However,there are discrepancies between previous studies and the present study on the lifespan of the two species.Also,the sample size of the present study is small especially for U.edulis.Hence,future studies should be conducted to validate the daily periodicity of growth increment in the regions of statolith(except for the lateral dome which has been validated)and the sample size should be increased for age and growth studies.展开更多
基金Supported by the National Natural Science Foundation of China(Nos.41306127,41276156)supported by SHOU International Center for Marine Studies and Shanghai 1000 Talent Program
文摘The mitre squid(U roteuthis chinensis) and the swordtip squid( U. edulis) are Indo-Pacific cephalopod species that are abundant in the western Pacific Ocean. They are currently exploited in the East and South China Seas and make up a significant portion of the Chinese neritic squid catch. Beaks, the feeding organs of squid, are important for individual size and biomass estimation because of their high resistance to degradation in predator stomachs and consistent dimensions. In this study, 104 U. chinensis and 143 U. edulis individuals were sampled from northern South China Sea with mantle length from 70 to 260 mm and 96 to 284 mm, respectively. The results indicated that morphological beak values were greater for U. edulis, compared to U. chinensis, for upper hood length(UHL), upper crest length(UCL), upper lateral wall length(ULWL), lower crest length(LCL), and lower lateral wall length(LLWL). According to principal component analysis, UHL/ML, UCL/ML, ULWL/ML, LCL/ML, LLWL/ML and LWL/ML could represent the characteristics of beaks for U. chinensis, while UHL/ML, UCL/ML, ULWL/ML, LHL/ML, LCL/ML and LLWL/ML could represent it for U. edulis. According to Akaike's information criterion(AIC) values, a power function was the most suitable model for U. chinensis, while a linear function was the most suitable model for U. edulis. The beak variable-mantle length ratio(beak variable/mantle length) declined with the increasing of mantle length and declined sharply at the early stage of growth in both beaks and species. The ratio changed quickly after achieving the mantle length of 140 mm for U. chinensis, while the ratio changed quickly after 170 mm for U. edulis. Beaks in both species experienced sharper changes through maturity stage I to II than other maturity stages. This study gives us basic beak morphology information for U. chinensis and U. edulis in the East and South China Seas. Geometric morphological methods combined with dietary analysis should be used in the future.
基金The National Key R&D Program of China under contract No.2019YFD0901404the National Natural Science Foundation of China under contract No.41876141+1 种基金the Shanghai Science and Technology Innovation Program under contract No.19DZ1207502the Fund of Key Laboratory of Open-Sea Fishery Development,Ministry of Agriculture and Rural Affairs under contract No.LOF 2018-02。
文摘Swordtip squid(Uroteuthis edulis)is one of the important economical fishing target species in the East China Sea.Uroteuthis edulis is characterized by rapid growth,extensive migration,and long spawning period and sensitive to surrounding environment.In order to assess its stock status,it is necessary to explore its spawning season,growth patterns of different populations and their relationship with the environment in advance.In this paper,based on the samples of U.edulis collected in the East China Sea from September 2017 to March 2018,we explored the relationships between daily growth of statolith microstructure and environmental variables by gradient forest method and generalized additive model.The spawning season of U.edulis was found to be nearly one year,and two dominant season groups were found:the spring group with the peak period of April and the summer group with the peak period of August.Water temperature in the depth of 25 m(Temp_25),sea surface temperature(SST)and zonal velocity were the key environmental variables for the daily growth of April-spawning group.The most suitable environmental conditions for the growth of April-spawning group were water temperature(24-27℃)and velocity(0.1-0.3 m/s).SST,Temp_25 and mixed layer depth were the key environment variables for the daily growth of August-spawning group.The most suitable environmental conditions for the growth of Augustspawning group were water temperature(21-28℃)and water depth(0-50 m).Key environmental variables of different groups suggested that early growth was significantly affected by seasonal changes of water temperature,current velocity and prey abundance.This study explored the relationships between early growth and environmental variables and provided the scientific guidance for the management and conservation of U.edulis.
基金This work was funded by the National Science Foundation of China(NSFC41306127 and NSFC41276156).
文摘To determine the age and growth of Uroteuthis chinensis and U.edulis,growth increments of the lateral dome of the statolith were used in the present study.Specimens of the two species caught in the South China Sea(SCS)and East China Sea(ECS)were used to compare the age and growth differences between sexes.In the present study,we found the two species have similar lifespans of less than 200 days.We also found that there were significant differences in the relationships between mantle length and body weight for two species and for both sexes in the same species.The back-calculated hatching date for the two species was similar,i.e.October to January for specimens caught in spring,and March to June for specimens caught in summer(U.edulis)or autumn(U.chinensis).Exponential and logistic growth curves were fitted to build the age and mantle length relationship.Both growth curves showed that U.chinensis has a larger mantle length than U.edulis at the same age.The results of the growth rates also showed that U.chinensis grows faster than U.edulis.However,there are discrepancies between previous studies and the present study on the lifespan of the two species.Also,the sample size of the present study is small especially for U.edulis.Hence,future studies should be conducted to validate the daily periodicity of growth increment in the regions of statolith(except for the lateral dome which has been validated)and the sample size should be increased for age and growth studies.
