基于繁殖群体与补充群体结构特征的金乌贼资源增殖策略优化

利用青岛近岸海域连续监测数据,分析金乌贼繁殖群体及补充群体结构特征,比较不同洄游时期繁殖亲体的绝对生殖力与卵子规格,以及补充群体的扩散迁移过程,为金乌贼繁殖亲体筛选、增殖模式优化及放流海域合理规划等提供参考。结果显示,5—7月陆续洄游至青岛近岸的金乌贼繁殖亲体的胴长、体质量及其怀卵量随采样时间推移均呈逐渐下降趋势,前期繁殖亲体成熟卵细胞的卵径和卵重显著高于中期和后期亲体。金乌贼产黏性卵,通常将受精卵黏附于海藻或其他附着物上,其幼体生长迅速。受繁殖亲体结群期长及分批产卵等繁殖习性影响,补充群体的胴长、体质量离散水平亦随秋季采样时间推移不断升高。补充群体规格的离散可促进空间生态位分化,增加营养生态位宽幅,该生殖策略有利于减小种内摄食压力。基于金乌贼繁殖生态学特征,建议集中采集前期洄游亲体开展人工苗种繁育,以提升繁育效率,保证大规格苗种供应;依据其分批产卵习性,大规模增殖放流可分批进行,以减小种内饵料竞争,提高放流群体成活率;5—7月在近岸水深15～20 m的缓流区投放人工产卵附着基,也是一种有效的资源原位修复手段。今后应进一步探究金乌贼受精卵放流技术,优化其资源修复模式,降低增殖成本,提高资源增殖效率。

Strategy optimization of stock enhancement of golden cuttlefish, (Sepia esculenta) based on structural characteristics of reproductive and recruitment populations

Golden cuttlefish, Sepia esculenta, was one of the largest economic cephalopods in Chinese northern seas, with an annual yield of more than 1 000 tons until the 1970 s. Since then, with the continuous expansion of fishing activities and dwindling of spawning field, this species has greatly reduced its local abundance compared with the previous condition due to its biological sensitivity to the environment (one-year life cycle and low fecundity). For this situation, many measures have been adopted to boost the population to meet the needs of human consumption, such as the release of artificially hatched juveniles and restoration of spawning habitats. The primary objective of this study is to optimize the existing conservation strategies and methods of cuttlefish by exploring the structural characteristics of the cuttlefish population in Qingdao coastal waters. The brood amount and size of egg cells of adult cuttlefish in 2017 were calculated. The distribution of body length and spatiotemporal migration process of juveniles were analyzed by using continuous monitoring methods. Results showed a decreasing trend in the specification of golden cuttlefish that arrived at different stages during the grouping period (May-July). The brood amount and size of egg cells of breeding cuttlefish in the early-stage were significantly higher than those of middle-and later-stages. The fertilized eggs of cuttlefish are characterized by sinking and stickiness, thus attaching to the attachment, such as algae or reefs. For juvenile cuttlefish, they grow rapidly, and the dispersion level of body specifications increases with sampling time due to the long grouping period and spawning in batches habits of breeding cuttlefish. This behavior might be a reproductive strategy for avoiding intraspecific feeding competition and promoting the differentiation of spatial niche. Therefore, according to the actual brood amount and the quality of eggs in the collection periods of breeding cuttlefish, it is suggested that the utilization rate of the early-stage population should be increased to improve breeding efficiency and guarantee the supply of large-size juveniles. The placement of spawning substrates in the spawning ground (slow-flowing area, 15-20 m) of adult cuttlefish from May to July is an important measure of resource restoration. Based on the reproductive habits of breeding cuttlefish, background survey in food abundance of release''s water for juvenile cuttlefish is indispensable. To reduce the intraspecific predation pressure and improve the survival rate of released population during large-scale juveniles'' release, juveniles'' release in different periods should be taken into consideration. In order to further optimize the mode of resource restoration and reduce the cost of the proliferation of cuttlefish, we also suggest exploring the technology of releasing fertilized eggs.