Sensitivity of larval and juvenile fish with different swim bladder morphology to barotrauma with a special focus on Cypriniformes

TL;DR

This study examines how different fish species, especially cypriniforms, are affected by barotrauma during rapid pressure changes in hydropower turbines.

Contribution

The study identifies species-specific injury patterns and swim bladder morphology as key factors in barotrauma sensitivity.

Findings

Physostomous cypriniforms showed the highest sensitivity to barotrauma with frequent swim bladder ruptures.

Depth acclimation increased vulnerability in European grayling.

Partial load conditions in Kaplan turbines reduced barotrauma-related mortality.

Abstract

Barotrauma, caused by rapid pressure changes, poses a major risk to fish migrating downstream through hydropower turbines. This study investigated the sensitivity of larval and juvenile fish with different swim bladder morphology to barotrauma using a custom-built chamber. Four different representative species, namely the two cypriniform species common nase (Chondrostoma nasus) and roach (Rutilus rutilus), both physostomous species with a two-chambered swim bladder, European grayling (Thymallus thymallus) as physostomous species with a single-chambered swim bladder and European perch (Perca fluviatilis) as physoclistous species with a single chambered swim bladder were investigated. Fish were acclimated to 0- or 15-meters depth (101 and 251 kPa, respectively) and exposed to rapid decompression to different nadirs (15, 30, 40, 60 kPa) to simulate turbine passage as a basis to construct dose-response curves predicting lethal injury probabilities. Species- and stage-specific injury patterns emerged, with physostomous cypriniforms showing the highest sensitivity and suffering frequent swim bladder ruptures. Depth acclimation, particularly in E. grayling, increased vulnerability. Moreover, lower barotrauma-related mortality was observed under partial load conditions in Kaplan turbines compared to full load. These insights are of high relevance for predicting barotrauma-related injury risks across species, particularly for species-rich groups like Cypriniformes and Characiformes that share similar swim bladder traits, to support sustainable hydropower development.

The online version contains supplementary material available at 10.1038/s41598-025-32670-y.

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