Japanese threadfin bream Nemipterus japonicus（Bloch, 1791） is among the most abundant and commercially important species in Pakistan. From the coast of Pakistan, four demersal trawl surveys in October–November 2009...Japanese threadfin bream Nemipterus japonicus（Bloch, 1791） is among the most abundant and commercially important species in Pakistan. From the coast of Pakistan, four demersal trawl surveys in October–November 2009 and May–June, August, October and November in 2010 were carried out. The purpose of this study is to estimate the population dynamics and status of the stock of the N. japonicus from Pakistani waters based on the research trawl surveys from the research area. The data consist of n=784 length-weight pairs and n=7 530 length frequency with the maximum length and weight of 29 cm and 358 g respectively. The length frequency data were analyzed using ELEFAN method in FiSAT computer package. The parameters of length and weight relationship were b=2.778, a=0.032 and R2=0.973. The estimated von Bertalanffy growth function parameters were L∞=30.45 cm, K=0.270 year-1. Based on length-converted catch curve analysis the total mortality（Z） during this study was estimated at 0.960 year-1. The natural mortality coefficient（M） was 0.74 year-1 using Pauly＇s equation（the annual average sea surface temperature was 27°C）, therefore, the fishing mortality coefficients（F） were 0.22 year-1. The yield per recruit analysis indicated that when tc was 2, Fmax was estimated at 1.2 and F0.1 at 1.1. When tc was 1, Fmax was estimated at 0.95 and F0.1 at 0.8. Because current age at first capture is about 1 year and Fcurrent was 0.22, Fcurrent is smaller than F0.1 and Fmax, which indicated that the fishery is about in a safe condition. When using Gulland（1971） biological reference point, Fopt was equals to M（0.74）. The current fishing mortality rate of 0.22 was smaller than the target biological reference point.展开更多
Understanding the reproductive biology particularly sexual maturity,reproductive cycle and fecundity of fish is useful for fisheries management.Unfortunately,there is no information about reproductive biology of Nemip...Understanding the reproductive biology particularly sexual maturity,reproductive cycle and fecundity of fish is useful for fisheries management.Unfortunately,there is no information about reproductive biology of Nemipterus furcosus.This study addresses this deficit for N.furcosus.We conducted a 12-month study to understand the reproductive biology particularly the sex ratio,sexual maturity,fecundity and reproductive cycle of N.furcosus at the east coast of peninsular Malaysia.Results indicated that ratios of male and female were statistically similar up to 19.0 cm TL(total length).Male outnumbered female above 19.0 cm TL(P<0.05).The fecundity ranged between 54,970 and 236,938 with a mean fecundity of 102,477±43,580(standard deviation).Male and female fish reached first sexual maturation at almost same size,15.8 and 15.6 cm,respectively.This information is needed to determine the lowest acceptable harvest length of this fish under the management aim to enter all female fish for reproduction minimum one time in their life.We estimated the reproductive period of N.furcosus applying oocytes diameter,histological examination of ovaries and monthly mean GSI.All of these methods gave a consistent result about spawning season,which appeared to be from March to July with peaks in March and June.Based on this result,N.furcosus spawners can be protected during March to July for entering the reproductive stock.Apart from artificial breeding,the results of this study might facilitate future efforts at fine-tuning fishing effort for a proper management of N.furcosus.展开更多
基金The special research fund of Ocean University of China under contract No.201022001
文摘Japanese threadfin bream Nemipterus japonicus（Bloch, 1791） is among the most abundant and commercially important species in Pakistan. From the coast of Pakistan, four demersal trawl surveys in October–November 2009 and May–June, August, October and November in 2010 were carried out. The purpose of this study is to estimate the population dynamics and status of the stock of the N. japonicus from Pakistani waters based on the research trawl surveys from the research area. The data consist of n=784 length-weight pairs and n=7 530 length frequency with the maximum length and weight of 29 cm and 358 g respectively. The length frequency data were analyzed using ELEFAN method in FiSAT computer package. The parameters of length and weight relationship were b=2.778, a=0.032 and R2=0.973. The estimated von Bertalanffy growth function parameters were L∞=30.45 cm, K=0.270 year-1. Based on length-converted catch curve analysis the total mortality（Z） during this study was estimated at 0.960 year-1. The natural mortality coefficient（M） was 0.74 year-1 using Pauly＇s equation（the annual average sea surface temperature was 27°C）, therefore, the fishing mortality coefficients（F） were 0.22 year-1. The yield per recruit analysis indicated that when tc was 2, Fmax was estimated at 1.2 and F0.1 at 1.1. When tc was 1, Fmax was estimated at 0.95 and F0.1 at 0.8. Because current age at first capture is about 1 year and Fcurrent was 0.22, Fcurrent is smaller than F0.1 and Fmax, which indicated that the fishery is about in a safe condition. When using Gulland（1971） biological reference point, Fopt was equals to M（0.74）. The current fishing mortality rate of 0.22 was smaller than the target biological reference point.
基金the International Islamic University Malaysiathe Ministry of Higher Education,Malaysia for the financial assis-tance through P-RIGS18-032-0032 and FRGS19-096-0705 projects,respectively.
文摘Understanding the reproductive biology particularly sexual maturity,reproductive cycle and fecundity of fish is useful for fisheries management.Unfortunately,there is no information about reproductive biology of Nemipterus furcosus.This study addresses this deficit for N.furcosus.We conducted a 12-month study to understand the reproductive biology particularly the sex ratio,sexual maturity,fecundity and reproductive cycle of N.furcosus at the east coast of peninsular Malaysia.Results indicated that ratios of male and female were statistically similar up to 19.0 cm TL(total length).Male outnumbered female above 19.0 cm TL(P<0.05).The fecundity ranged between 54,970 and 236,938 with a mean fecundity of 102,477±43,580(standard deviation).Male and female fish reached first sexual maturation at almost same size,15.8 and 15.6 cm,respectively.This information is needed to determine the lowest acceptable harvest length of this fish under the management aim to enter all female fish for reproduction minimum one time in their life.We estimated the reproductive period of N.furcosus applying oocytes diameter,histological examination of ovaries and monthly mean GSI.All of these methods gave a consistent result about spawning season,which appeared to be from March to July with peaks in March and June.Based on this result,N.furcosus spawners can be protected during March to July for entering the reproductive stock.Apart from artificial breeding,the results of this study might facilitate future efforts at fine-tuning fishing effort for a proper management of N.furcosus.
