The North Patagonian gulfs, Argentina, support an important population of small pelagic fish (SPF) that play a key role in the marine ecosystem. Here, we assessed the seasonal SPF distribution in Nuevo gulf and San Matías Gulf concerning several environmental variables and the nautical area scattering coefficient (NASC) of Munida gregaria using generalized additive models (GAMs). We collected biological data by a 38/200 kHz echosounder along zigzag transects in all four seasons. The echoes of fish were separated from other targets using a dB difference algorithm. Then, we calculated the mean NASC of pelagic fishes every 0.5 nm. Satellite-derived data were used to characterize the environment at study sites. GAMs were built in two stages for each gulf considering all season in a single model in one hand, and each season separately in the other one. In the first stage, we modeled the probability of presence as a function of predictors. In the second stage, we used the NASC of fish as the response for presence data only. In general terms, the probability of fish presence increases with bottom depth, and the fish density was higher in cold waters and zones with higher chlorophyll-a concentration. The relative importance of the variables was different according to the season. The formation and rupture of the thermocline and its subsequent spatial heterogeneity observed in spring and autumn could be important drivers of SPF distribution. Squat lobsters’ distributions related positively with SPF in San Matías Gulf summer and negatively in Nuevo Gulf summer.

中文翻译：

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两个巴塔哥尼亚湾高空间分辨率下远洋鱼类分布的物理和生物驱动因素

阿根廷的北巴塔哥尼亚湾支持着重要的小型远洋鱼类 (SPF) 种群，它们在海洋生态系统中发挥着关键作用。在这里，我们评估了新湾和圣马蒂亚斯湾的季节性 SPF 分布，涉及几个环境变量和Munida gregaria的航海区域散射系数 (NASC)使用广义加性模型 (GAM)。我们通过 38/200 kHz 回声测深仪沿所有四个季节的锯齿状断面收集了生物数据。使用 dB 差异算法将鱼的回声与其他目标分开。然后，我们每 0.5 nm 计算一次远洋鱼类的平均 NASC。卫星数据被用来描述研究地点的环境特征。一方面在单个模型中考虑所有季节，另一方面在每个季节分别考虑每个海湾的 GAM 分两个阶段构建。在第一阶段，我们将存在概率建模为预测变量的函数。在第二阶段，我们仅使用鱼的 NASC 作为对存在数据的响应。一般来说，鱼出现的概率随着底部深度的增加而增加，在冷水和叶绿素-a 浓度较高的区域，鱼类密度较高。变量的相对重要性因季节而异。在春季和秋季观察到的温跃层的形成和破裂及其随后的空间异质性可能是 SPF 分布的重要驱动因素。深蹲龙虾的分布与圣马蒂亚斯湾夏季的 SPF 呈正相关，而在新湾夏季则与 SPF 呈负相关。