Study On The Fishery Biology Of Three Sebastes In Jiaozhou Bay Qingdao

Sebastes nigricans, S. hubbsi and S. schlegelii belong to Scorpaeniformes Scorpaenoidei Scorpaenidae Sebastes, are distributed in the Yellow Sea of China and in some Japanese waters. The three species are perched in the rocky reefs of shallow cold waters with a high economic value. In this study,107 S. nigricans,209 S. hubbsi and 45 S.schlegelii specimens were collected in the cage net in the Jiaozhou Bay Qingdao from April 2013 to July 2014. To protect the biodiversity of the three kinds of fish, realize the sustainable development and utilization of the three Sebastes fishery resources, fishery biology include morphology and reproduction, age and growth research, and, classification and identification were did in this paper, and the main results were as follows:1. In this chapter,93 S. nigricans and 152 S. hubbsi which were collected from Jiaozhou Bay Qingdao in 2014 were be done with basic biological research. A large number of meristic characters, morphometric characters riched the morphological data of the two rockfishes, this research obtained the fin formula of the two fishes in Jiaozhou Bay rockfish:the fin formula of S. nigricans was D. ⅩⅢ-ⅩⅣ-12-13, P. 16～17, Ⅴ. Ⅰ～Ⅱ-3～5, A. Ⅲ-6～7, C.17～19; the fin formula of S. hubbsi was D. Ⅻ～ⅩⅣ-11-14, P.15～17, Ⅴ.Ⅰ-5, A. Ⅲ-5～8, C.17～20. The sex ratio of S. nigricans was 4.23:1, and sex ratio of was S. hubbsi was 2.12:1, the Chi-square test results of both were significantly deviate from 1:1(P<0.05). No matter at which growth stages the female individuals were higher than the male individuals of the two fishes. Fish liver was the place to store, absorb and transport nutrients, and in this research the GSI and HSI trend of the two rockfishes were both just the opposite, indicating that their liver was the place which provide material basis and energy for sexual maturity. Individual relative fecundity represented the reproductive strategy, the relative fecundity with body lengh of S. nigricans and S. hubbsi were both less than other economic fish, showed the differences between ovoviviparous fish and oviparous fish, ovoviviparous fish could maintain their population continuity with fewer fecundity. It was feasible to identify S. nigricans and S. hubbsi based on morphological data, and it could get a high identification accuracy. And the number of dorsal fin spines could be used as the important classification criteria to identify the two rockfish.The minimum body length of sexual maturity of S. nigricans was 104mm, and through the logistic equation, the 50%females sexually mature body length of S. nigricans was 123.2mm. The minimum body length of sexual maturity of S. hubbsi was 64mm, and through the logistic equation, the 50%females sexually mature body length of S. hubbsi was 77.3mm; And these body length of sexual maturity could provide a theoretical basis for making appropriate fishing specifications.Secondly, we did the age and growth studies based on otolith microstructure of 107 S. nigricans and 209 S. hubbsi which collected in Jiaozhou Bay Qingdao from 2013 to 2014. The body length of S. nigricans ranged from 86mm to 200mm, and their weight ranged from 19.8g to 260.3g; The body length of S. hubbsi ranged from 51mm to 131mm, and their weight ranged from 4.5g to 63.5g. Body length and weight of S. nigricans and S. hubbsi all showed a power function relationship, among them S. nigricans gained the relationship W=2 ×10-5 BI3.101 (R2=0.939), S. hubbsi gained the relationship W＝8×10-5BL2.797 (R2=0.861). Age was determinated based on otolith annulation structure, the results revealed that the age of S. nigricans range from 1+～6+years old, thereinto 2+～3+years old was the dominant age group (81.3%). The age of S. hubbsi range from 0+～7+years old, thereinto 2+～4+years old was the dominant age group (77.5%). The growth of S. nigricans and S. hubbsi both corresponded to Von Bertalanffy growth equation, the Von Bertalanffy growth equations of S. nigricans were L1= 191.7 × [1-e-0.277(1+1414)] and W,=249.5× [-1.e-0.277(t+1.414)]3.101; and the Von Bertalanffy growth equations of S. hubbsi were L,=131.4×[1-e-0.269(t+2.697)] and Wt=63.6×[1-e-0.169(1+2.6971]2.797. The process of growth of 5. nigricans and S. hubbsi appeared that growed rapidly firstly and then gradually became more stable, their growth history could be divided into three stages:S. nigricans ①rapid growth when 1+～2+years old, ②mature and stable when 2+-4+ years old, ③old period when after 4+　years old; S. hubbsi ①rapid growth when 1+～3+years old,②mature and stable when 3+～6+ years old, ③old period when after 6+ years old. The otolith of S. nigricans and S. hubbsi would grow with the growth of the rockfishes. And otolith weight could be used as a means to estimate their age quickly. Comprehensive the turnoff age and the 50%sexually mature body length, we should use body length (130mm) and weight (75g) as the listing standards of 5. nigricans, and body length (80mm) and weight (20g) as the listing standards of S. hubbsi, to protect the fishery resources of S. nigricans and S. hubbsi in the waters of Jiaozhou Bay Qingdao.Thirdly, the sagittae morphological characteristics of three species S. hubbsi, S.nigricans and S.schlegelii which collected in Jiaozhou Bay Qingdao from 2013 to 2014, were analyzed to test the hypothesis that the three Sebastes species could be identified by their sagittae morphology and to find out which method was more appropriate. Eight otolith shape indices and 37 elliptical Fourier coefficients (eFcs) were analyzed, and results showed that the difference in the sagittae morphology between S. hubbsi and S. schlegelii were the largest, and those between S. hubbsi and S. nigricans were the least. In the discriminant analyses of the three species, discriminating rates of more than 95% were obtained and they were clearly sorted in scatter plots when using the otolith shape indices, the eFcs, as well as a combination of the two. When applied to the three species of which otolith was 4 to 7 mm and those were more than two years old, the species identification based on the otolith morphology was proved to be feasible:when only using the eFcs, a 100%of discriminating rate was obtained but this method couldn’t quickly locate the shape which was tiny in fact but significant difference among the sagittae of the three Sebastes in statistics. Combing otolith shape indices and the eFcs could not only obtain a high classification rate of about 99%, but also identify the differences in the rectangularity, form-factor and surface density among the three Sebastes sagittae. The results showed that combing shape indices analysis and elliptical Fourier analysis was the effective method for species discrimination of genus Sebastes and it can find out the differences of the sagittae of the three Sebastes.