Decadal population depletion, size class reduction, and range contraction of the giant yellow croaker in China: Implications for conservation and management

Abstract

Many species became threatened long before solid population monitoring studies were conducted, making their conservation very challenging. Here, we utilize local ecological knowledge, grey and peer-reviewed literature data to reveal the population dynamics and decline process of a Critically Endangered large marine fish (the giant yellow croaker) in the Pearl River Estuary (its last spawning refuge) and across southern China (its historical geographic range) over recent five decades. We gathered sporadic timeseries data about the (i) growth and abundance indicators, (ii) occurrences and distribution range, (iii) anthropogenic drivers for population declines. We then used timeseries models to reconstruct the process of population change and its potential drivers. We quantitatively compared the range of historical and current distributions for this species. Our results demonstrated that (i) its population showed a prominent decline in body size and geographic range across China, (ii) its abundance was generally stable and low in the Pearl River Estuary and habitat loss and environmental degradation may prevent its recovery despite of the significant decline in fishing pressure in recent decades. These findings highlight that population recovery actions including habitat restoration and protections are urgently needed for this species. We show that local ecological knowledge is valuable in reconstructing population dynamics of data-poor iconic fish and in better understanding both their geographic range and anthropogenic threats.