Performance of the long-snouted seahorse, Hippocampus guttulatus, under warming conditions

Temperature is a determinant cue for several behavioral, physiological, and metabolic processes in fish, which occur within a range set to optimize species fitness. Understanding how ocean warming will impact species, at individual and population levels, is, therefore, of utmost relevance for management and conservation purposes. This knowledge assumes particular relevance when it comes to species with unique life history traits that experience multiple threats, such as seahorses. This study aimed to assess the effects of warming on growth, feed intake, and behavioral patterns of the long-snouted seahorse, Hippocampus guttulatus. Fish were collected, before the breeding season, in the Sado estuary, Portugal, and subsequently exposed for an 8-week period to three different temperatures: 17 degrees C, 20 degrees C, and 24 degrees C. Three times a week, behavioral observations were performed. Feed intake was measured every day and individuals were weighed once a week. Results indicate differences in behavioral responses of seahorses exposed to increasingly warming conditions. Under extreme temperature conditions (24 degrees C), fish were more active, and fed more, but this increment of energy through feeding did not translate into increased growth in weight. Altogether, these results indicate that Sado's population of H. guttulatus may become under thermal stress when exposed, for a long term, to warming conditions that are expected to occur by the end of the century.

Automated summary

Temperature is a crucial factor affecting the behavior, physiology, and metabolism of fish, which in turn influence their fitness. Understanding the impact of ocean warming on individual and population levels of species is essential for conservation purposes. This study focused on assessing the effects of warming on the growth, feed intake, and behavioral patterns of long-snouted seahorses. The results showed that seahorses exhibited different behavioral responses under increasingly warming conditions, with increased activity and feeding, but no corresponding weight gain. These findings suggest that the Sado population of H. guttulatus may experience thermal stress under long-term exposure to predicted warming conditions by the end of the century.