Organizers: Luiz A. Rocha1, Hudson Pinhero1, Randall K. Kosaki2 & Joshua M. Copus3

Affiliations: 1/ California Academy of Sciences, 2/ NOAA Papahānaumokuākea Marine National Monument, 3/University of Hawaii.

Email: lrocha@calacademy.org; htpinheiro@gmail.com; randall.kosaki@noaa.gov; joshua.copus@gmail.com

Lead contact: Luiz A. Rocha

Description: Within this session, we expect to provide a platform for researchers that are studying the biodiversity, taxonomy, ecology, biogeography, and evolution of fishes in mesophotic coral ecosystems (MCEs). Although coral-reef habitats extend to approximately 150 m (500 ft) depth, the vast majority of biological research has focused on the upper 30 m (100 ft). The remaining four-fifths of coral-reef habitat, known as MCEs or the “Twilight Zone”, remain almost unknown. Over the past three decades, improvements in mixed-gas rebreather diving technology, as well as increased access to remotely operated vehicles (ROVs) and manned submersibles, has led to a steady increase in the exploration and documentation of MCEs within the tropical Indo-Pacific and elsewhere. Consequently, publications about “mesophotic fishes” grew substantially in the last years, from four in 2010 to 45 today (1/3 of the total publications about mesophotic fishes were published in 2016). Research conducted so far has revealed many undescribed species and unique biogeographic, ecological, and evolutionary patterns. The primary purpose of this session is to summarize current knowledge about MCE fishes throughout the tropical Indo-Pacific, focusing on the uniqueness and broad-scale patterns observed in this poorly known habitat. As many MCEs have been identified as refugia for shallow water fishes, this session will also provide conservation information applicable to shallow reefs. As an outcome, we expect to generate more effective and complementary research by coordinating ongoing and future strategies among the several groups actively working in this emerging field.

Expected Audience: We expect this session to be of interest not only to researchers focused on deeper coral-reef environments, but also to all who study fishes on coral reefs. In particular, it will be of interest to a wide variety of scientists exploring disciplines such as biodiversity, taxonomy, ecology, biogeography, evolution (including population genetics), physiology, and conservation of fishes. Moreover, the great diversity of scientists who have generalized or characterized coral-reef fishes based on data from the shallowest 20% of coral-reef environments will likely be interested in understanding what is known about the remaining 80% of that habitat. Interest in documenting MCEs in general has increased dramatically in recent years (particularly since 2010), and many current and future graduate students have gravitated toward research projects in this area of study. In addition to scientists involved with primary research, MCEs are widely seen as playing an important role in issues such as whether deeper habitats can serve as a reservoir or refuge for heavily exploited or threatened shallow-reef environments (and vice-versa), so this session will be of interest to those involved with reef fish management and conservation. Thus, we expect a diverse collection of talks and posters by researchers from many regions of the world. Based on the success of a similar session in the recent International Coral Reef Symposium in Hawaii, we expect a high attendance and interest during the IPFC. It should also attract potential conference sponsors from the ROV, submersible, photography, filming, and technical diving industries.