# Removal of dead fish eggs by Asellus aquaticus as a potential biological control in aquaculture

## TL;DR

This study shows that Asellus aquaticus can selectively eat dead fish eggs without harming live ones, suggesting they could help keep aquaculture hatcheries clean.

## Contribution

The study demonstrates the selective foraging behavior of A. aquaticus on dead fish eggs, opening new possibilities for biological control in aquaculture.

## Key findings

- A. aquaticus consumed dead zebrafish eggs but left viable eggs and larvae untouched.
- The number and exposure time of A. aquaticus affected the proportion of dead eggs consumed.
- A. aquaticus may help reduce pathogen growth by removing dead eggs as a substrate.

## Abstract

The objective of the present experimental study was to gain a better understanding of the foraging activity of Asellus aquaticus during fish egg incubation. A. aquaticus were introduced into experimental setups of dead eggs, viable eggs and hatched larvae of zebrafish (Danio rerio), a commonly used model organism. The amount of A. aquaticus and the duration of their exposure to the eggs significantly affected the proportion of consumed dead eggs in each experimental cycle. A. aquaticus belongs to the group of aquatic detritivores, and no predatory behavior was observed during the experiments. These crustaceans could distinguish between the dead eggs and those containing living embryos. Furthermore, zebrafish larvae remained unharmed by A. aquaticus, even in the absence of alternative food source. These findings underscore the potential sanitary role of these crustaceans in natural waters and offer new perspectives on their possible use as biological control organisms in aquaculture hatcheries. Additionally, our results suggest a potential application of A. aquaticus in combating pathogens by reducing the growth substrates for bacteria and fungi.