coral reef fishes

The successful dispersal of coral reef fish populations relies on the high swimming abilities of pelagic larvae and - once settled to a reef habitat - the ability to endure hypoxia at night. This study used swimming respirometry and transcriptomics to examine the physiological mechanisms underlying the transition of cinnamon anemonefish larvae from pelagic to benthic life stages. The results suggest that changes in gene expression of oxygen-binding proteins may play a crucial role in successful larval recruitment, which has implications for understanding the connectivity of coral reef fish populations.

Anthropogenic noise has negative impacts on animal reproductive success, and protecting habitats from noise pollution may help improve it. The study used a season-long field manipulation on the Great Barrier Reef to demonstrate that limiting motorboat activity on reefs leads to increased fish offspring survival. A complementary laboratory experiment and the field study suggest that the improved reproductive success is due to improvements in parental care and offspring length, highlighting the potential benefits of noise mitigation for enhancing ecosystem resilience.

Measuring swimming performance of small fishes contributes to a better understanding of how environmental factors affect individual organisms and potentially populations dynamics (e.g., through variable dispersal and connectivity). Here, we automated multi-lane swimming chambers to reduce operator interference and optimize swimming performance measurements of early life stages of fishes. Testing different experimental protocols, we found species-specific sensitivities in offspring from two tropical fishes.

In this study we found that micropredation by a single parasite (gnathiid isopod) significantly decreased escape performance and swimming behaviour of coral reef fish juveniles. However, stress hormone (cortisol) levels doubled. These findings suggest that micropredation may affect the overall fitness of juvenile fish hosts, which may result in large scale changes in the number of fish succesfully recruiting to adult populations on coral reefs.

In this study, we showed that critical thermal maxima differ across species and life stages in tropical fishes. Furthermore, body mass and experimental heating rate had a strong influence on the measured thermal tolerance. This suggests that these factors need to be accounted for when estimating and comparing heat tolerance across early ontogeny in tropical fishes.

Management and conservation advice can benefit from physiological findings, as these support a mechanistic understanding of changes that are observed on organism- or even population-levels. We highlight examples for coral reef fishes, and advocate better collaboration and knowledge exchange between physiologists and decision-makers.