西白令海狭鳕夏季卵巢发育特征

性腺发育是鱼类繁殖生物学的重要研究内容之一。狭鳕是全球渔业单一品种产量最高的鱼种，但目前有关西白令海狭鳕性腺发育，尤其是卵巢发育的研究较为不足。为此，根据2017年6—9月和2018年8—9月在西白令海（60°28′N ~61°57′N，179°11′E~177°57′W）随机采集的狭鳕卵巢样本，利用组织学分析，描述了狭鳕卵母细胞和卵巢的发育阶段。结果显示，夏季西白令海狭鳕卵巢内同时存在不同时相的卵母细胞，卵母细胞可分为9个发育时相，卵巢分为5个发育阶段；卵巢发育期与叉长、纯体质量、卵巢质量和性腺指数均无统计学上的相关性，且雌性个体的性腺指数无法较好地预测西白令海狭鳕的性成熟度。夏季，所取样的狭鳕大部分不产卵，成熟个体产卵活动不频繁，Ⅱ期和V期发育阶段的狭鳕均较少。本研究可为西白令海狭鳕的资源状况评估及渔业可持续发展提供科学数据。

Ovary development of walleye pollock (Gadus chalcogrammus) in the western Bering Sea summer

The development of gonad is one of important parts for studying fish reproduction biology. Walleye Pollock (Gadus chalcogrammus) is the single fish species with the highest commercial catch worldwide. However, the information about the gonadal development, particularly the ovary development of this species in the western Bering Sea is limited. Based on ovarian samples randomly collected from June to September 2017 and August to September 2018 in the western Bering Sea (60°28''N - 61°57''N, 179°11''E - 177°57''W), histological analysis was used to describe the development stages of the oocytes and ovaries of Walleye Pollock. The results showed that oocytes in different phases occurred in the ovary of Walleye Pollock in the western Bering Sea. The oocytes of Walleye Pollock were divided into 9 developmental phases, and the ovary was divided into 5 developmental stages. There were no statistically significant correlations between ovarian development and fork length, net weight, ovarian weight and Gonadosomatic Index (IGS), respectively. The IGS can''t be considered as a good index for predicting the maturity of Walleye Pollock in the western Bering Sea. Most of sampled Walleye Pollock did not spawn during summer, the mature individuals did not ovulate frequently, and few individuals in the second and last stages of development were found in the samples. The present study provided biological information for the stock assessment and sustainable exploitation of Walleye Pollock resource in the western Bering Sea.