Unravelling Seascape Patterns of Cryptic Life Stages: Non-Reef Habitat Use in Juvenile Parrotfishes

Rene A. Abesamis,Katie T. Sievers,Abner A. Bucol,Garry R. Russ

doi:10.3390/d12100376

Rene A. Abesamis, Katie T. Sievers + Show 2 more

Open Access

https://doi.org/10.3390/d12100376

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Abstract

Juvenile fish often use alternative habitats distinct from their adult phases. Parrotfishes are an integral group of coral reef fish assemblages, are targeted in fisheries, are sensitive to reef disturbances, and have been documented as multiple-habitat users. Considering the abundance of research conducted on parrotfishes, very little is known about their juvenile ecology at the species level due to their cryptic and variable coloration patterns. We collected juvenile parrotfishes in non-reef habitats (macroalgal beds, seagrass beds, and lagoons) in the Philippines and used DNA analysis to determine species composition. The results were then compared with data on adult parrotfish abundance from underwater visual census (UVC) surveys in coral reef and non-reef habitats. Collections identified 15 species of juvenile parrotfishes in non-reef habitats, and of these, 10 were also recorded in UVCs as adults. Informed by adult surveys, 42% of the 19 parrotfish species observed as adults were classified as multi-habitat users based on their presence in coral reef and non-reef habitats. When accounting for the occurrence of species as juveniles in non-reef habitats, 93% of the species collected as juveniles would be considered multi-habitat users. Species identified as juveniles in non-reef habitats comprised 50% of the average adult parrotfish density on coral reefs and 58–94% in non-reef habitats. The species richness of juveniles in non-reef habitats was greater than that of adults occupying the same habitats, and the most common adult species observed in UVCs was not collected as juveniles in non-reef habitats. Finally, UVC suggested that 97% of juvenile parrotfish <10-cm total length was present in non-reef habitats compared to coral reefs. These results provide further evidence for ontogenetic movement across habitat boundaries for parrotfish species in a diverse and highly connected tropical seascape. This is one of the few studies to quantify links between nursery and adult habitat in parrotfishes, highlighting the importance of including non-reef habitats in ecological studies of an iconic group of coral reef fish.

Highlights

Juvenile fish often use alternative habitats distinct from their adult phases
We identified 15 parrotfish species or species sets based on collection of juveniles (Table 3), 14 by DNA results and one by observation (S. dimidiatus)
This study demonstrated considerable use of non-reef habitats by juvenile parrotfishes, with ontogenetic shifts representing prevalent and important life-history transitions for many species

Summary

Introduction

Juvenile fish often use alternative habitats distinct from their adult phases This strategy is assumed to increase juvenile survival, which contributes to adult populations. These alternative habitats are defined as nursery habitats [1,2,3,4]. Non-reef habitats can have reduced predation levels compared to coral reefs but often at the cost of reduced growth rates [9,10]. This fitness trade-off is a key element driving nursery habitat use, where juveniles use habitats adjacent to coral reefs before moving to coral reefs as adults [11], otherwise known as ontogenetic habitat

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