浙江北部沿岸春夏季长蛸时空分布及其与海洋环境的关系

Relationship between spatial-temporal distribution of long-arm octopus Octopus minor and oceanographic environmental factors along north coast of Zhejiang province during spring and summer

根据2014—2016年春夏季浙江北部沿岸拖网调查数据,选取时空因子(年、月、经纬度)和环境因子(底层温度SBT、底层盐度SBS、深度Depth和溶解氧DO),分析长蛸(Octopus minor)资源的时空分布情况,并利用提升回归树(boosted regression tree, BRT)模型研究各因子对长蛸资源丰度(以渔获量g/h表示)的影响程度。结果表明:2014年的平均渔获量明显高于2015和2016年,同一年中4月份的渔获量均高于其他月份;主要渔获量分布在122.75°E～123.25°E,30°N～30.5°N之间;2015年的渔场重心较其他年份略向北移动,4月至6月间渔场重心向东北方向移动,但变化不明显;选择以学习率(learning rate,lr)为0.001和复杂度(tree complexity,tc)为4的模型来建立时空环境因子与渔获量的关系,发现溶解氧对渔获量的影响最大,占所有影响因子的45.5%;其次为年和盐度,随后依次为深度(10.7%)、底层温度(7.3%)、纬度(4.7%)、月(4.7%)以及经度(2.3%)。相比较时空因子而言,环境因子对长蛸的渔获量影响更大。溶解氧是直接影响长蛸活动的重要因素,后续研究应该对此因子提高关注。

According to the trawl survey data along north coast of Zhejiang Province during spring and summer of 2014 to 2016, the spatial-temporal factors(year, month, latitude and longitude) and environmental factors(sea bottom temperature, SBT;sea bottom salinity, SBS;depth;dissolved oxygen, DO) were selected to analyze the spatial-temporal distribution of Octopus minor, as well as its relative importance using boosted regression tree(BRT). The results showed that the average catch in 2014 is higher than that of 2015 and 2016, and the catch in April is also higher than other months in the same year;the main catch distributed ranged from 122.75°E to 123.25°E,30°N to 30.5°N;the gravity of fishing ground in 2015 moved a little northward compared with the other two years, the gravity of fishing ground also moved a little northward during April to June;the learning rate(lr) 0.001 and tree complexity(tc) 4 were selected to establish the model between environmental factors and catch, and dissolved oxygen(DO) was the most important factor, accounting for 45.5%, then year and salinity, accounting for higher than 10%, then successively, depth(10.7%), SBT(7.3%), latitude(4.7%), month(4.7%) and longitude(2.3%). Environmental factor is more important than spatial-temporal factor to the catch of Octopus minor. Future studies should pay more attention to the dissolved oxygen as it is a critical factor that directly influences the marine organism.