Biological Characteristics Of Two Economic Species Of Southwest Atlantic Ocean

Based on the biological data of366Argentina hake (Merluccius hubbsi) and399rockcod (Patagonotothen ramsayi) collected on board “Lurongyu No.6177andNo.6178”operating in the southern Atlantic Ocean off Argentina during January2011to April2011, the present study analyzed the biological charateristics,includingmaturity stage of the gonad, feeding intensity, sex ratio, standard length distribution,body weight distribution, the relationship between standard length and percentage ofempty stomachs and the relationship between standard length and body weight bystatistic and power regression methods. The results show that:Argentina hake:The standard length ranges from24.4to72.5cm. The dominating standard lengthranges from30.1to35.0cm on January. The dominating standard length ranges from35.1to40.0cm during February to April. The body weight ranges from130to945g.The dominating body weight ranges from301to350g on January. The dominatingbody weight ranges from401to450g during February to April. The age compositionis from1to6.The relationship between standard length and body weight is W=0.021830L2.740002.There is more females than males, and the ratio of females to males is about4.63:1. The maturity stage of the gonad of both females and males is dominating ofstage Ⅵ.The feeding intensity is mainly in the class0,class1and class2. The lowestpercentage of class0,class1and class2is49%on January; The highest percentage ofthem is87%on April. The feeding intensity of males is mainly in the class0,class 1and class2;The lowest percentage of class0,class1and class2is68%on February;The highest percentage of them is100%on April. The feeding intensity of females ismainly in the class0,class1and class2;The lowest percentage of class0,class1andclass2is45%on January; The highest percentage of them is84%on April.When standard length falls into20.1-50cm, the percentage of empty stomachs isfluctuating with the standard length increasing,ranging from20%to40%. Whenstandard length is larger than50.1cm, percentage of empty stomachs is0. Percentageof empty stomachs of males is decreasing with the standard length increasing. Whenstandard length falls into20.1-50cm, percentage of empty stomachs of females isincreasing with the standard length increasing. When standard length is larger than50.1cm, percentage of empty stomachs of females is0.Rockrod:The standard length ranges from9.3to30.4cm. The dominating standard lengthranges from9.0to10.9cm on January. The dominating standard length ranges from19.0to20.9cm during February to April. The body weight ranges from9.5to533g.The dominating body weight ranges from0to49.9g on January. The dominatingbody weight ranges from100to149.9g during February to April. The agecomposition is from0to5.The relationship between standard length and body weight is W=0.004898L3.388855.There is more females than males, and the ratio of females to males is about1:0.48. The maturity stage of the gonad of both females and males is dominating ofstage Ⅱ,the percentage of stages Ⅰand Ⅲ is low during January to April.The feeding intensity is mainly in the class0,class1and class2. The lowestpercentage of class0, class1and class2is49%on January; The highest percentage ofthem is90%on March. The feeding intensity of males is mainly in the class0,class1and class2. The lowest percentage of class0,class1and class2for males is41.2%on January; The highest percentage of them is77%on February. The feeding intensity of females is mainly in the class0,class1and class2. The lowest percentage of class0,class1and class2for females is45%on January; The highest percentage of them is86.3%on March.When standard length falls into25-26.9cm, the percentage of empty stomachs isthe highest (30%). Except the group of standard length falling into25-26.9cm, thepercentage of empty stomachs is increasing and then decreasing with the standardlength increasing. When standard length falls into15-26.9cm, the percentage of emptystomachs of males is decreasing and then increasing with the standard lengthincreasing. Except the group of standard length falling into15-26.9cm, the percentageof empty stomachs of males is0. When standard length falls into25-26.9cm, thepercentage of empty stomachs of females is the highest (30%). When standard lengthis larger than27cm, percentage of empty stomachs of females is0.