Total biomass and areal biomass density are often necessary to establish ecological relationships and enable informed management decisions, in particular setting fisheries catch limits. Further refining these estimates to sub-population biomass based on length informs ecological models of predator-prey dynamics, ecosystem energy transfer and biogeochemical cycles; however, measures of uncertainty in these per-length biomass estimates are needed. We present a statistical method to calculate the per-length biomass of Antarctic krill (Euphausia superba) from conversion factors using acoustic and net sample data. Variability in krill length-frequency, and wetmass introduced by net sampling is also explored through non-parametric bootstrapping. We applied this method on a 1 mm length window to active acoustic and net sample data collected during an Antarctic krill biomass survey in CCAMLR Division 58.4.2 (62 – 67°S; 55 – 80°E, with a survey area of 775,732 km2) performed between February – March 2021. We found that 77% of the total estimated biomass was attributable to krill of length 14 – 49 mm. The largest biomass of krill in a single length bin was estimated as 340,000 t (95% CI: 148,000 - 408,000 t) and was found in the 49 mm length bin (i.e., 48.5 to 49.5 mm). This method will allow future surveys (with sufficient data) to estimate biomass of krill on a per-length basis along with associated uncertainty (confidence intervals) derived from net sampling and so may be used to provision size-based ecosystem models with krill biomass.

中文翻译：

---

南极磷虾（Euphausia superba）的单位长度生物量估计

总生物量和面积生物量密度通常是建立生态关系和做出明智的管理决策所必需的，特别是设定渔业捕捞限额。根据长度进一步细化这些对亚种群生物量的估计，为捕食者-猎物动力学、生态系统能量转移和生物地球化学循环的生态模型提供信息；然而，需要衡量这些单位长度生物量估计的不确定性。我们提出了一种统计方法来计算南极磷虾的单位长度生物量（超级磷虾) 来自使用声学和净样本数据的转换因子。还通过非参数自举探索了磷虾长度频率和净采样引入的湿质量的变化。我们在 1 毫米长的窗口上应用了这种方法，以在 CCAMLR 58.4.2 分部（62 – 67°S；55 – 80°E，调查面积为 775,732 公里）的南极磷虾生物量调查期间收集的主动声学和净样本数据2个) 在 2021 年 2 月至 3 月之间进行。我们发现总估计生物量的 77% 归因于长度为 14-49 毫米的磷虾。单个长度箱中磷虾的最大生物量估计为 340,000 吨（95% CI：148,000 - 408,000 吨），并且在 49 毫米长度箱（即 48.5 至 49.5 毫米）中被发现。这种方法将允许未来的调查（有足够的数据）在每个长度的基础上估计磷虾的生物量以及来自净采样的相关不确定性（置信区间），因此可用于提供具有磷虾生物量的基于大小的生态系统模型。