| Thunnus alalunga, English name is Albacore, is temperate oceans upper-middle-fish, swimming fast, highly migratory, gregariousness,one kind of the small-size tuna. Albacore is widely distributed in the Pacific Ocean, Indian Ocean and the Atlantic Ocean is one of the main types of tuna fisheries. With the development of the north Pacific albacore fishery in recent years, the north Pacific albacore resources protection has become an important topic. Study on reproductive biology can evaluate and forecast the north Pacific albacore population resource and population development status in order to provide data support and scienticbasic.It provide reliable basic data and scientific support for fishery management measures,reasonable utilization and scientific management in the north Pacific albacore fishery resources.Based on the research data collected during conducting the North Pacific albacore tuna resources exploration supported by Ministry of Agriculture from October 2013 to February 2014 in the North Pacific Ocean (29° 08'N-41° 08'N,163° 50'W-144° 19'W), through survey data of longlines fishing and the biological samples we taken back,using Excel, Spss, Origin, Marin and paraffin method, to analyze biological characteristics of north Pacific albacore tuna in order to do research about the fishery biology and reproductive biology study. Research including its group composition, feeding, gonad development characteristics, gonad maturation level, individual characteristics of development, reproduction distribution characteristics, the minimal maturity age and 50% sexual maturity, the gonad maturation level, batch fecundity and sex ratio and so on. The main conclusions are as follows:(1)The range of fork length for femal is from 74cm to 111cm, the average fork length is 85.22cm, and the dominant fork length is 81cm to 90cm. The range fork length for male is from 63cm to 99cm, the average fork length is 84.73cm, and the dominant fork length is 81cm to 90cm.According to one-way ANOVA test, there is no significant differences in the fork length composing between male and female albacore(F=2.165, P>0.05).(2) The range of weight for femal is from 7kg to 25kg, the average weight is 11.15kg, and the dominant weight is 9kg to 12kg. The range weight for male is from 5kg to 12kgcm, the average weight is 11.01cm, and the dominant weight is 9kg to 12kg.According to one-way ANOVA test, there is no significant differences in the weight composing between male and female albacore(F=1.408, P>0.05).(3)The relationship between fork length(cm) and weight(kg) of the north Pacific albacore could be described as follows:whole:W= 0.0004FL2.3154 (r2=0.7014, n=787);female:W= 0.0005FL22365(r2=0.6783, n=364);male:W= 0.0003FL2.3776 (r2=0.7186, n=423).(4)Histologically,the development progress of albacore oocyte is divided into six phases.In phase ?,mitosis occurs frequently; In phase ?, mitosis stop, appear yolk nucleus, extracellular appear a layer of follicular cells; In phase ?, cells mature gradually,follicular cells has developed from a single layer to the second floor, a radiation membrane, lipoid vesicle and yolk granules appear; In phase ?, lipoid vesicle summed up several big lipoid vesicle, radiation membrane thickening. In phase V,the oocyte is about to be eduction, lipoid vesicle fuse into a big one,nuclear moves to the animal pole of the mature oocyte, after the oocyte spawned, follicular cell become a zona radiate. In phase VI,not all the mature oocytes spawned,those did't spawned will be re-absorbed.(5) Histologically, according to the distribution of dominant oocytes, ovary development process is divided into six periods. In the ? stage,ovary is too small to distinguish sex when observed by naked eyes;In the ? stage, ovary is red. We can not recognize the oocytes granules when observed by naked eyes; In the ? stage, ovary is bigger.Number of Oocyte in phase ? is obvious.We can recognize the oocytes granules obviously; In the IV stage, ovary become larger and darker obviously. Oocytes granules are easy to be separated. Number of Oocyte in phase IV is obvious.In the ? stage, ovary gauffer become larger and thicker tempestuously,if abdomen was squeezed slightly, oocytes fluid will outflow. In the ? stage, ovary is aubergine, smaller, the surface shrinkage is flabby, looks like an empty capsule.(6) The north Pacific albacore GSI (Gonad-somatic index) has certain correlation with fork length. With the improvement of gonad maturation level, ovary weight and GSI will change obviously.(7) The north Pacific is a type of tubular (also known as radiant),sperm become mature in the blade which is in radial structure, blade wall is composed of testis membrane connective tissue.One side of the testis with longitudinal crack, output tube is at the bottom of testis.Tubular structures lay regularly.(8)According to the observational method, testis development process is divided into six periods. In the ? stage, testis is hard to distinguish sex when observed by naked eyes; In the ? stage, blood vessel of testis is not obvious,it is easy to distinguish sex when observed by naked eyes; In the ? stage, testis look like weak red or bright yellow cylindrical; In the IV stage, testis is hoary, blood vessel is obvious. If abdomen was squeezed slightly, a little sperm fluid will outflow. In the V stage, testis is white and fully mature. If abdomen was squeezed slightly, plenty of viscous white sperm fluid will outflow. In the ? stage, Testis natural degradation or spawned.A small amount of sperm often remain.(9)During sampling time, there are two peak spawning period, the mid-december and the early of January. In the investigation waters, GSI of female albacore decreasing trend along with the increase of latitude, variation with longitude is not obvious.(10) Combining with the analysis of observational method and histological method.The the minimal maturity age of the north Pacific albacore are 81cm (males) and 86cm (females),50% sexual maturity fork length are 87.72cm (males) and 90.44cm (females). Logistic equation is used to calculate the north Pacific albacore mature rate relationship with fork length:Males: Curve fitting degree is 93.48%Females Curve fitting degree is 93.61%(11)The batch fecundity range of female north Pacific albacore is from 149126.2pcs to 429965.6pcs. The average fecundity is 285692.87pcs±77912.88. The relative fecundity range is from 12.43pcs*g-1-33.07pcs*g-1. The average relative fecundity is 21.22 pcs*g-1±5.06.(12)In this research, there are 364 male albacore and 423 female albacore.The overall sex ratio is 1:1.16. After sexual maturity, male proportion increased with fork length, while the female proportion reduced gradually. In general, there are more males than females. |
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