# First record of winter pregnant males of two pipefish species in a Mediterranean coastal lagoon

## TL;DR

For the first time, male pipefish were found to be pregnant in winter in a Mediterranean lagoon, possibly due to recent warming trends.

## Contribution

First recorded winter breeding event for two pipefish species in response to thermal anomalies.

## Key findings

- Pregnant males of Syngnathus abaster and Syngnathus typhle were observed in January 2025 in the Mar Menor lagoon.
- The size structure of S. abaster in winter 2025 differed from colder winters, suggesting phenological shifts.
- This indicates potential impacts of climate change on the reproductive dynamics of syngnathids.

## Abstract

Syngnathus abaster Risso, 1827 and Syngnathus typhle L., 1758 are key components of fish assemblages in European transitional waters, with well‐documented reproductive cycles typically occurring from spring to autumn. However, recent warming trends in the western Mediterranean has raised questions about potential shifts in their breeding phenology. In January 2025, three pregnant S. abaster males and one S. typhle male were detected in the Mar Menor Coastal lagoon (western Mediterranean), representing the first recorded winter breeding event for both species. The size structure of S. abaster in winter 2025 also contrasted with colder winters, further supporting this interpretation. These findings may reflect a response to recent thermal anomalies and highlight the phenological plasticity of these species. To our knowledge, this is the first indication of potential phenological shifts in syngnathids from transitional waters, with implications for understanding how climate change may influence their reproductive dynamics.