We evaluated the feeding ecology of largehead hairtail (Trichiurus lepturus) and hairtail (T. margarites). We collected specimens from fishing ports in the Beibu Gulf (Gulf of Tonkin) from October 2008 to September 20...We evaluated the feeding ecology of largehead hairtail (Trichiurus lepturus) and hairtail (T. margarites). We collected specimens from fishing ports in the Beibu Gulf (Gulf of Tonkin) from October 2008 to September 2009 and analyzed their gut contents. We collected 857 T. lepturus and 666 T. margarites samples. The number of stomachs examined in this study was sufficient to describe the monthly and ontogenetic diet shifts for the two species, as indicated by the trophic diversity curves. T. lepturus was a general omnivore, feeding primarily on Bregmaceros rarisquamosu, Decapterus maruadsi, and Acetes chinensis. Conversely, T. margarites preyed primarily on D. maruadsi, B. rarisquamosus, B. nectabanus, and A. chinensis. Both species exhibited distinct ontogenetic diet shifts. Although the two hairtail specie fed on similar sources in the same habitat, the diet overlap was relatively low. Our results suggest that hairtail play an important role in controlling small pelagic and benthic fish populations in the gulf. This trophic correlation shall be used for developing a marine ecosystem model for the Beibu Gulf.展开更多
Surplus-production models are widely used in fish stock assessment and fisheries management due to their simplicity and lower data demands than age-structured models such as Virtual Population Analysis. The CEDA (catc...Surplus-production models are widely used in fish stock assessment and fisheries management due to their simplicity and lower data demands than age-structured models such as Virtual Population Analysis. The CEDA (catch-effort data analysis) and ASPIC (a surplus-production model incorporating covariates) computer packages are data-fitting or parameter estimation tools that have been developed to analyze catch-and-effort data using non-equilibrium surplus production models. We applied CEDA and ASPIC to the hairtail (Trichiurus japonicus) fishery in the East China Sea. Both packages produced robust results and yielded similar estimates. In CEDA, the Schaefer surplus production model with log-normal error assumption produced results close to those of ASPIC. CEDA is sensitive to the choice of initial proportion, while ASPIC is not. However, CEDA produced higher R 2 values than ASPIC.展开更多
Largehead hairtail(Trichiurus japonicus)is a commercially important fish species in China Seas,characterized by wide distribution,seasonal migration,spawning all year round.Under long-term high fishing pressure,the bi...Largehead hairtail(Trichiurus japonicus)is a commercially important fish species in China Seas,characterized by wide distribution,seasonal migration,spawning all year round.Under long-term high fishing pressure,the biological traits of largehead hair-tail have changed,such as miniaturization,smaller size-at-age and earlier age-at-maturation.To explore its current biological charac-ters,we analyzed age,growth and maturation of largehead hairtail in the East China Sea by analyzing the otolith microstructure and gonads.The results showed that largehead hairtail is mainly composed of 1 year and 2 years old individuals.The estimated von Ber-talanffy growth function(VBGF)showed significant differences between sexes,and asymptotic pre-anal length of male is longer than that of female.Two spawning seasons were observed in spring and autumn by monthly gonadosomatic index(GSI).Compared to historic survey data,the average pre-anal length at age decreased and size-at-maturation became smaller in the East China Sea.This study updates life history parameters of largehead hairtail,and provides a reference for the present status of largehead hairtail,which can contribute to largehead haritail stock assessment and sustainable utilization in the China Seas.展开更多
A total of 472 isozyme samples and about 1 000 myogen, esterase and morphyological samples of nine spawning stocks were collected from coastal waters of Hainan, Guangdong, Fujian, Zhejiang, Jiangsu and Sbandong Provin...A total of 472 isozyme samples and about 1 000 myogen, esterase and morphyological samples of nine spawning stocks were collected from coastal waters of Hainan, Guangdong, Fujian, Zhejiang, Jiangsu and Sbandong Provinces of China during 1976￣1992. Eleven isozymes were analysed by starch-gel and polyacrylamide-gel electrophoresis. Biochemical genetic structures of 11 isozymes were analysed and 24 loci were recorded. According to the allele frequencies of individual isozymes of each sampling stock, the mean proportion of polymorphic (P) and average heterozygosity (H) were calculated; then the genetic similarity (I) and genetic distance (D) were obtained. The results of cluster for O and D of all the samplied stocks show that the hairtail fish from Chemise coastal waters should be classified into three different sped6s (D: 0. 223￣0. 382) and eight populations (D: 0. 007￣0. 048).展开更多
The size selectivity and catch pattern of Trichiurus lepturus in 40 mm diamond and square mesh codends were investigated in this study.A 34 m high opening trawl was used,which is a common design used by fishermen oper...The size selectivity and catch pattern of Trichiurus lepturus in 40 mm diamond and square mesh codends were investigated in this study.A 34 m high opening trawl was used,which is a common design used by fishermen operating along the northwest coast of India,and the cover codend method was employed to determine codend selectivity.Along with the changes in the length at 50%retention rate for Trichiurus lepturus with the usage of the square and diamond mesh codends,indicators to understand the exploitation pattern of this species in the fishery were assessed based on the total number of individuals and on total weight of the catch.The mean selection length increased and discard fraction is reduced when 40 mm square mesh codends are used in place of diamond meshes,however,it is observed that individuals at commercial length are also lost.The results demonstrate that mandatory use of legal mesh sizes alone will be insufficient to aid in the sustainable harvest of this species,given its estimated length at first sexual maturity of 61.2 cm.This is the first study to compare the size selection of this species in 40 mm diamond and square mesh codends along Northwest coast of India.Results of the study will help as a baseline for gear-based regulations in the region.展开更多
Knowledge of reproductive biology and life-history traits of populations exploited by fisheries is important for their sustainable management.We investigated the life-history traits of Trichiurus lepturus(largehead ha...Knowledge of reproductive biology and life-history traits of populations exploited by fisheries is important for their sustainable management.We investigated the life-history traits of Trichiurus lepturus(largehead hairtail)in south-eastern Australia;a region of low exploitation for this otherwise heavily exploited circumglobal species,to investigate whether there were differences in the reproductive biology and life-history traits in the south-east Australian population compared with those in other regions.We also used histological sections to examine male and female gonads at a microscopic level.Trichiurus lepturus in south-eastern Australia had a greater maximum length(193 cm total length(TL)),matured at a larger length(108 cm TL at 50%mature)and had a spawning period(March to September,Austral winter)that was inconsistent with other regions.The overall sex ratio of 1:0.4 females:males was consistent with a female dominant sex ratio observed in other regions,particularly in larger length classes.However,females in the current study dominated samples from both estuarine and coastal habitats,as well as during the spawning and non-spawning periods,which is not consistent with the patterns found in other regions.Differences in south-eastern Australia may relate to limited fishing pressure,genetic variation,or differences in environmental factors that influence reproductive development,including temperature,trophic resources and habitat.展开更多
基金Supported by the National Natural Science Foundation of China (No.30771653)the Bureau of Fisheries,Ministry of Agriculture,Department of Education of Guangdong Province (No.LYM09089)Guangdong Ocean University (No.2009-11)
文摘We evaluated the feeding ecology of largehead hairtail (Trichiurus lepturus) and hairtail (T. margarites). We collected specimens from fishing ports in the Beibu Gulf (Gulf of Tonkin) from October 2008 to September 2009 and analyzed their gut contents. We collected 857 T. lepturus and 666 T. margarites samples. The number of stomachs examined in this study was sufficient to describe the monthly and ontogenetic diet shifts for the two species, as indicated by the trophic diversity curves. T. lepturus was a general omnivore, feeding primarily on Bregmaceros rarisquamosu, Decapterus maruadsi, and Acetes chinensis. Conversely, T. margarites preyed primarily on D. maruadsi, B. rarisquamosus, B. nectabanus, and A. chinensis. Both species exhibited distinct ontogenetic diet shifts. Although the two hairtail specie fed on similar sources in the same habitat, the diet overlap was relatively low. Our results suggest that hairtail play an important role in controlling small pelagic and benthic fish populations in the gulf. This trophic correlation shall be used for developing a marine ecosystem model for the Beibu Gulf.
基金Supported by the Special Research Fund of Ocean University of China(No. 201022001)
文摘Surplus-production models are widely used in fish stock assessment and fisheries management due to their simplicity and lower data demands than age-structured models such as Virtual Population Analysis. The CEDA (catch-effort data analysis) and ASPIC (a surplus-production model incorporating covariates) computer packages are data-fitting or parameter estimation tools that have been developed to analyze catch-and-effort data using non-equilibrium surplus production models. We applied CEDA and ASPIC to the hairtail (Trichiurus japonicus) fishery in the East China Sea. Both packages produced robust results and yielded similar estimates. In CEDA, the Schaefer surplus production model with log-normal error assumption produced results close to those of ASPIC. CEDA is sensitive to the choice of initial proportion, while ASPIC is not. However, CEDA produced higher R 2 values than ASPIC.
基金supported by the National Key R&D Program of China(No.2018YFD0900902)the Na-tional Natural Science Foundation of China(No.41861134037).
文摘Largehead hairtail(Trichiurus japonicus)is a commercially important fish species in China Seas,characterized by wide distribution,seasonal migration,spawning all year round.Under long-term high fishing pressure,the biological traits of largehead hair-tail have changed,such as miniaturization,smaller size-at-age and earlier age-at-maturation.To explore its current biological charac-ters,we analyzed age,growth and maturation of largehead hairtail in the East China Sea by analyzing the otolith microstructure and gonads.The results showed that largehead hairtail is mainly composed of 1 year and 2 years old individuals.The estimated von Ber-talanffy growth function(VBGF)showed significant differences between sexes,and asymptotic pre-anal length of male is longer than that of female.Two spawning seasons were observed in spring and autumn by monthly gonadosomatic index(GSI).Compared to historic survey data,the average pre-anal length at age decreased and size-at-maturation became smaller in the East China Sea.This study updates life history parameters of largehead hairtail,and provides a reference for the present status of largehead hairtail,which can contribute to largehead haritail stock assessment and sustainable utilization in the China Seas.
文摘A total of 472 isozyme samples and about 1 000 myogen, esterase and morphyological samples of nine spawning stocks were collected from coastal waters of Hainan, Guangdong, Fujian, Zhejiang, Jiangsu and Sbandong Provinces of China during 1976￣1992. Eleven isozymes were analysed by starch-gel and polyacrylamide-gel electrophoresis. Biochemical genetic structures of 11 isozymes were analysed and 24 loci were recorded. According to the allele frequencies of individual isozymes of each sampling stock, the mean proportion of polymorphic (P) and average heterozygosity (H) were calculated; then the genetic similarity (I) and genetic distance (D) were obtained. The results of cluster for O and D of all the samplied stocks show that the hairtail fish from Chemise coastal waters should be classified into three different sped6s (D: 0. 223￣0. 382) and eight populations (D: 0. 007￣0. 048).
文摘The size selectivity and catch pattern of Trichiurus lepturus in 40 mm diamond and square mesh codends were investigated in this study.A 34 m high opening trawl was used,which is a common design used by fishermen operating along the northwest coast of India,and the cover codend method was employed to determine codend selectivity.Along with the changes in the length at 50%retention rate for Trichiurus lepturus with the usage of the square and diamond mesh codends,indicators to understand the exploitation pattern of this species in the fishery were assessed based on the total number of individuals and on total weight of the catch.The mean selection length increased and discard fraction is reduced when 40 mm square mesh codends are used in place of diamond meshes,however,it is observed that individuals at commercial length are also lost.The results demonstrate that mandatory use of legal mesh sizes alone will be insufficient to aid in the sustainable harvest of this species,given its estimated length at first sexual maturity of 61.2 cm.This is the first study to compare the size selection of this species in 40 mm diamond and square mesh codends along Northwest coast of India.Results of the study will help as a baseline for gear-based regulations in the region.
文摘Knowledge of reproductive biology and life-history traits of populations exploited by fisheries is important for their sustainable management.We investigated the life-history traits of Trichiurus lepturus(largehead hairtail)in south-eastern Australia;a region of low exploitation for this otherwise heavily exploited circumglobal species,to investigate whether there were differences in the reproductive biology and life-history traits in the south-east Australian population compared with those in other regions.We also used histological sections to examine male and female gonads at a microscopic level.Trichiurus lepturus in south-eastern Australia had a greater maximum length(193 cm total length(TL)),matured at a larger length(108 cm TL at 50%mature)and had a spawning period(March to September,Austral winter)that was inconsistent with other regions.The overall sex ratio of 1:0.4 females:males was consistent with a female dominant sex ratio observed in other regions,particularly in larger length classes.However,females in the current study dominated samples from both estuarine and coastal habitats,as well as during the spawning and non-spawning periods,which is not consistent with the patterns found in other regions.Differences in south-eastern Australia may relate to limited fishing pressure,genetic variation,or differences in environmental factors that influence reproductive development,including temperature,trophic resources and habitat.
