Dark marine habitats are often characterized by a food-limited condition. Marine caves are characterized by the absence of light and limited water flow, which lead to reduced fluxes of organic matter for cave-dwelling organisms. Marine caves are listed among the European habitats requiring the designation of special areas for conservation.

This study investigated whether the most abundant and common cave-dwelling fish Apogon imberbis has the potential to play the role of trophic vector in Mediterranean marine caves. This was done by assessing stomach contents to check for changes in repletion according to a nycthemeral cycle, by identifying prey items and their habitats and by assessing A. imberbis movements out of the caves at nigh to feed.

It was found out that A. imberbis stays within the caves during the day and moves out at night to feed on invertebrates associated with habitats other than caves.

The authors conclude that the obtained results support the hypothesis that A. imberbis could contribute to enriching marine caves with POM (Particulate Organic Matter), thus reducing the cave food depletion and evidencing the crucial trophic role of this species in connecting Mediterranean marine caves with external habitats. It is highlighted that the findings may provide a helpful basis for optimizing management and conservation measures.

https://www.nature.com/articles/s41598-018-27491-1

Bussotti et al. (2018) Fish mitigate trophic depletion in marine cave ecosystems. Scientific Reports 8:9193