Advances in satellite remote sensing of environmental perturbations have become important in understanding variations of ocean productivity and small pelagic fish catches. This marine resource is vital for coastal populations dependent on artisanal fishing for their income and food security, such as in coastal East Africa. In this region, the eastern Pemba Channel (Tanzania) represents a hotspot area, for a variety of marine species including small pelagics and coral reef associated species. This study examines the links between mackerel fish catch, one of the important small pelagic fish for direct consumption in the region, and changes in environmental oceanographic parameters over the period 2012–2018. The fisheries catch data is a rare local dataset, consisting of daily mackerel landings (from 2012 onwards) and supplemented by qualitative information on the mackerel fishery obtained through interviews with local stakeholders. The physical factors influencing phytoplankton biomass, and in turn, mackerel fisheries yield is investigated, using remotely-sensed chlorophyll-a (Chl-a) and Sea Surface Temperature (SST), together with Mixed Layer Depth (MLD) data from the high-resolution ocean model NEMO. We show that seasonal variations in mackerel landings are positively (negatively) correlated with Chl-a (SST) with a 1-month time lag (i.e., biophysical factors change first, mackerel stocks follow one month later). On the eastern side of the Pemba Channel, cooler SST and higher Chl-a are observed during the Southeast monsoon accompanied by increased mackerel landings, suggestive of enhanced productivity. Interannually, these relationships remain valid both for monthly and annual means, which confirms the close link between the variations of mackerel and biophysical conditions. Analysis of the Chl-a and MLD anomalies, relative to the mean, reveals that the phytoplankton blooms observed on the eastern side of the Pemba Channel, during the Southeast monsoon, are likely due to the deepening of the mixed layer, which tends to entrain cold and nutrient rich waters from greater depths to the surface. We conclude that upper ocean mixing contributes to the observed enhanced productivity along with other environmental factors. Additionally, we show how our results can be applied in the management of the mackerel resource in the Pemba Channel.

卫星遥感环境扰动的进展对于了解海洋生产力和小中上层鱼类捕获量的变化已变得很重要。这种海洋资源对于依靠手工捕鱼谋求收入和粮食安全的沿海人口至关重要，例如在东非沿海地区。在该地区，奔巴河东岸（坦桑尼亚）是一个热点地区，这里有各种海洋物种，包括小型浮游生物和与珊瑚礁有关的物种。这项研究研究了鲭鱼捕捞，2012-2018年期间该区域直接消费的重要小中上层鱼类之一与环境海洋学参数之间的联系。渔业捕捞数据是稀有的本地数据集，包括每日鲭鱼上岸量（自2012年起），并辅以通过与当地利益相关者的访谈获得的关于鲭鱼渔业的定性信息。使用遥感的叶绿素a（a）来研究影响浮游植物生物量的物理因素，进而研究鲭鱼的渔业产量。Chl-a）和海面温度（SST），以及来自高分辨率海洋模型NEMO的混合层深度（MLD）数据。我们显示，鲭鱼着陆的季节性变化与Chl-a（SST）正相关（负），具有1个月的时间滞后（即，生物物理因素首先发生变化，鲭鱼种群在一个月后发生变化）。在奔巴海峡的东侧，在东南季风期间观察到较冷的海温和较高的Chl-a，同时鲭鱼着陆量增加，表明生产力提高。每年一次，这些关系对于月度和年度均保持有效，这证实了鲭鱼的变化与生物物理条件之间的密切联系。该分析叶绿素aMLD异常（相对于平均值）揭示，东南季风期间在奔巴海峡东侧观测到的浮游植物水华，可能是由于混合层的加深，这往往会夹带来自冷水和营养丰富的水。更大的深度。我们得出的结论是，上层海洋混合与其他环境因素一起有助于观测到生产率的提高。此外，我们展示了如何将我们的结果应用到奔巴海峡鲭鱼资源的管理中。