Biomass decline is a vital threat for small-scale fisheries, but lack of data affects our ability to understand both biomass development and fishers’ adaptation. This study contributes to the literature on cost-effective, survey-data-based methods in data-poor and development-oriented settings. Based on original survey data from Nigeria, we find that 58% of respondents perceive a decline in fish abundance, in particular top-predator biomass. However, we also find signs of strategic behavior by respondents. Subsequently, we use multinomial logit and probit models to analyze the consequences of biomass decline for livelihoods. Our empirical findings support our theoretical prediction that biomass decline may crowd out some fishers while net favoring others, based on heterogeneous competitiveness. Furthermore, crowding-out status overlaps with high financial vulnerability. This emphasizes that biomass decline not only affects the cost of fishing, but may also adversely affect the fisheries pro-poor functions.

中文翻译：

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尼日利亚的生物质发展和渔民的脆弱性：来自调查数据集的证据

生物量减少对小规模渔业来说是一个重大威胁，但缺乏数据会影响我们了解生物量发展和渔民适应的能力。这项研究有助于在数据贫乏和面向发展的环境中建立具有成本效益、基于调查数据的方法的文献。根据尼日利亚的原始调查数据，我们发现 58% 的受访者认为鱼类丰度下降，尤其是顶级捕食者生物量。然而，我们也发现了受访者的战略行为迹象。随后，我们使用多项 logit 和 probit 模型来分析生物量下降对生计的影响。我们的实证研究结果支持我们的理论预测，即基于异质竞争力，生物量下降可能会排挤一些渔民，而净有利于其他渔民。此外，排挤状态与高财务脆弱性重叠。这强调了生物量下降不仅影响捕捞成本，还可能对渔业的扶贫功能产生不利影响。