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Estimates of availability and catchability for select rockfish species based on acoustic-optic surveys in the Gulf of Alaska
Fisheries Research ( IF 2.4 ) Pub Date : 2020-12-30 , DOI: 10.1016/j.fishres.2020.105848
Darin T. Jones , Christopher N. Rooper , Christopher D. Wilson , Paul D. Spencer , Dana H. Hanselman , Rachel E. Wilborn

Fishery-independent surveys, such as bottom trawl surveys, provide time-series abundance estimates, which inform many modern stock assessments. Area-swept biomass estimates from trawl surveys assume that fish densities do not differ between trawlable (T) and untrawlable (UT) areas. Bias and imprecision in the biomass estimates can occur when this assumption is not met. Thus, reliable estimates are needed for both the extent of T and UT habitat types in the surveyed area, and the relative densities of the fish species in the two habitat types to accurately assess groundfish populations. Acoustics and stereo-camera survey tools were used in the present study to determine the extent of T and UT habitat within 25-km2 bottom trawl survey grid cells historically designated as T/UT. Splitbeam acoustics were used to compare the abundance of rockfishes (Sebastes spp.) between the T/UT grid cell areas. Acoustic data were collected along uniformly spaced transects within 52 T and 43 UT grid cells throughout the Gulf of Alaska during summers 2013, 2015, and 2017. The acoustic backscatter attributed to rockfishes in UT grid cells was approximately three times that in T cells, and the percentages available to the bottom trawl survey were 40 % for harlequin rockfish, 43 % for northern rockfish, 51 % for dusky rockfish, and 98 % for Pacific ocean perch (POP). These findings allowed for estimation of the trawl catchability coefficient (q; a scaler between estimates of the area-swept survey abundance and actual abundance) of 0.46 for harlequin rockfish, 0.50 for northern rockfish, and 0.64 for dusky rockfish, and 1.15 for POP. These values could be used to inform the relationship between trawl survey estimated and actual abundances of rockfishes to improve the accuracy of stock assessments for these species.



中文翻译:

基于声光勘测在阿拉斯加湾对某些石鱼种类的可用性和可捕性进行估算

与渔业无关的调查,例如海底拖网调查,提供了时间序列的丰度估计,可为许多现代种群评估提供依据。拖网调查得出的区域清扫生物量估计值假设,可拖网(T)和不可拖网(UT)区域的鱼类密度没有差异。当不满足此假设时,可能会出现生物量估计中的偏差和不精确性。因此,需要对被调查地区的T和UT生境类型的范围以及这两种生境类型中鱼类物种的相对密度进行可靠的估计,以准确评估底层鱼类种群。在本研究中,使用了声学和立体摄像机调查工具来确定25 km 2之内的T和UT生境底部拖网调查网格单元,历史上称为T / UT。使用分束式声学比较T / UT网格单元区域之间的石鱼(Sebastes spp。)丰度。在2013年,2015年和2017年夏季,在整个阿拉斯加湾的52个T和43个UT网格单元中,沿着均匀分布的样线收集了声波数据。归因于UT网格单元中石鱼的声学反向散射约为T单元的三倍,而拖网调查所占百分比为:丑角石鱼40%,北部石鱼43%,昏暗石鱼51%和太平洋鲈鱼(POP)98%。允许用于拖网捕系数的估计(这些发现q; 丑角石鱼为0.46,北方石鱼为0.50,暗淡石鱼为0.64,POP为1.15,在区域扫描调查的丰度和实际丰度的估计之间进行缩放。这些值可用于告知拖网调查估计值与石鱼实际丰度之间的关系,以提高这些物种种群评估的准确性。

更新日期:2020-12-30
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