基于点模式模型的南极半岛北部南极磷虾渔场的时空变动

南极磷虾作为南极生态系统中的关键物种,磷虾渔场时空演变规律对于磷虾海洋生态功能影响及其资源管理十分重要。本研究利用我国磷虾渔业生产数据,按照月份组合,针对南极半岛北部磷虾渔业,采用点模式方法,利用3个空间因子:经度、纬度和离岸距离,获得各月磷虾资源分布最佳点模式模型和模型的方差分析结果,并以最佳点模式模型推知可能潜在的渔场分布。结果显示,(1)12月磷虾渔场离岸距离最大(为45 km),随后,渔场逐渐向南设得兰群岛岸线逼近,至3月时渔场离岸最近,3月之后,磷虾渔场逐渐远离海岸线,4月和5月渔场离岸距离大约在13 km左右。(2)点模式模型的方差分析结果发现,12月,1月,3月和4月最优点模式模型对模型的方差解释率分别为59%、60%、57%和68%,空间因子能够较好拟合磷虾渔场分布,而2月和5月,空间点模型对总体方差的解释率分别为38%和32%。(3)夏季12—1月,磷虾渔场分布在乔治王岛北部;2月,在利文斯顿岛周围形成第2个渔场,以及布兰斯菲尔德海峡中部形成第3个渔场;3—5月渔场基本分布在布兰斯菲尔德海峡沿南极半岛岸线平行方向分布。研究表明,南极半岛北部磷虾渔场的离岸距离远近与该海域海冰边界消融和生长的规律相吻合;基于空间因子点模式模型在大部分月份均能较好地拟合磷虾渔场的时空演变规律,再配合单位捕捞努力量渔获量(CPUE)数据,可以作为探测磷虾群热区的潜在手段。

Spatial-temporal variation on Euphausia superba fishing ground in the northern Antarctic Peninsula based on point pattern model

As a key species in the Antarctic ecosystem, the spatial and temporal dynamics of Antarctic krill''s fishing ground is becoming important issues for the role effects of krill''s oceanic ecosystem function and resource management.Using multi-year Chinese krill fishery scientific data by month group,combining three spatial factors-longitude, latitude and offshore distance, the optimal point pattern model of monthly krill distribution and the variance analysis results were obtained for the krill fishery in the northern Antarctic Peninsula based on the spatial point pattern method, and the possible potential fishing grounds were predicted based on the proposed optimal point pattern model. The results were: (1) In December, the greatest distance of fishing grounds to shore (45 km) can be found. Subsequently, the fishing grounds were gradually approaching coastline of the South Shetland Islands. By March the fishing grounds were at the least distance to the Antarctic Peninsula shoreline. After March, fishing ground gradually retreated from the coastal area, in April and May distance of fishing grounds to shore maintained about 13 km. (2) The variance analysis of the optimal point pattern model indicated the explained rates of variance to the model in December, January, March and April were 59%, 60%, 57% and 68%, respectively. Spatial factors can fit the distribution of krill fishing ground very well in these months. But in February and May, the explained rate of the variance to spatial point pattern model reduced to 38% and 32%, respectively. (3) Fishing grounds were located in the northern King George Island during austral summer (December to January).In February, a secondary fishing ground was formed around the Livingston Island, and the third fishing ground occurred in the middle of the Bransfield Strait.During March-May fishing ground distributed along in the Bransfield Strait paralleled to the Antarctic Peninsula. In conclusion, the offshore distance of the fishing ground coincided with the extension and retreating of the sea ice boundary in the northern Antarctic Peninsula. The point pattern model of krill fishery based on spatial factors can well fit the temporal and spatial evolution of krill fishing ground in most months. Combined with the catch per fishing unit (CPUE), the point pattern model can be used as a potential technique to explore the hotspot of krill aggregation.