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

Abstract:

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.