Persistent illegal sturgeon fishing in the Caspian Sea

Illegal, unreported, and unregulated (IUU) fishing driven by artisanal small-scale fisheries is a critical threat to global biodiversity and is exemplified by the commercial extinction of Caspian sturgeons (Acipenser and Huso). A key knowledge gap persists regarding the scale and behavioral dynamics of these operations. We tested the hypothesis that persistent high-volume sturgeon poaching is sustained not by fleet growth but by an intensification of fishing effort per boat, a behavioral adaptation to state containment policies. We administered structured questionnaires to 53 members of 24 sturgeon fishing brigades (SFBs) in Dagestan, Russia, from 2020 to 2021 and verified the data collected with written catch records. To overcome data limitations, we developed a seasonal (September to June) analytical model. This included indirect standardization to control for seasonality and factor analysis to deconstruct catch trends. Survival analyses (Kaplan-Meier) were used to validate changes in the timing and intensity of fishing activity. From 2018 to 2021, the 24 SFBs harvested an estimated 82,193 kg of sturgeon across 319 trips. Active SFBs decreased from 21 to 17. However, fishing effort intensified dramatically, with fishing months per brigade increasing by nearly 50%, from 4.33 to 6.42. This resulted in a 49% increase in catch per brigade. Concurrently, catch volume per fishing month declined, indicating reduced efficiency. Our findings suggest that state containment policies have not curbed poaching and may have instead spurred effort intensification. Based on our expertise and contextual analyses, we hypothesize that the state's hatchery program functions not only as an ecological intervention but also as a political compensatory mechanism, creating a conservation paradox where supplementation of sturgeon numbers inadvertently subsidizes the illegal fishery, which drives lethal bycatch of the endangered Caspian seal (Pusa caspica). The autonomy of Dagestani communities, rooted in socioeconomic exclusion, renders standard conservation solutions infeasible, locking the system into a feedback loop of overexploitation.