Demography of the largest and most endangered Brazilian parrotfish, Scarus trispinosus, reveals overfishing

Nc Roos,Bm Taylor,Go Longo,Ar Carvalho

doi:10.3354/esr01024

Abstract

Many parrotfishes (Labridae: Scarinae) have life history traits, including late maturation and long lifespans, that make them vulnerable to overfishing. The greenbeak parrotfish Scarus trispinosus is the largest Brazilian endemic parrotfish and has been harvested in reef-associated fisheries along the coast. After a sharp population decline, S. trispinosus is now considered by the IUCN to be an Endangered species. We provide an assessment of age-based and reproductive biology for this species and discuss applications for fisheries management. We sampled 95 individuals from inshore and offshore reefs from Rio Grande do Norte state, northeast Brazil, both obtained from artisanal fishing landings and fishery-independent collections. All sampled specimens were females with fork lengths (FL) ranging from 8.1 to 55.9 cm and ages ranging from 0.3 to 7 yr, with estimated median maturity (L50) of 39.2 cm FL and median age (A50) of 4.2 yr. Size class distributions indicate that the inshore reefs are mostly inhabited by juveniles under L50, whereas the offshore reefs are inhabited by mature individuals, suggesting an ontogenetic habitat shift from inshore to offshore reefs around the timing of maturation. The fishing pressure on this species is concentrated in inshore reefs, therefore mostly on immature individuals, which may be severely affecting the reproductive capacity of this species. This information is useful to guide size-based fisheries management, such as regulating minimum capture size and fishing gears that capture individuals smaller than L50. Managing fisheries of endangered species with late maturity and complex reproductive cycles such as S. trispinosus is imperative to aid recovery.

Highlights

Parrotfishes (Labridae: Scarinae) are important for subsistence and commercial reef fisheries worldwide
Differences in age distributions were observed between locations, with older individuals being more common in offshore reefs and younger individuals being more common in inshore reefs (Fig. 2B)
We provided an assessment of age-based and reproductive biology of Scarus trispinosus, an Endangered endemic species threatened by severe fishing pressure that resulted in a ~50% decline in the population over the past 30 yr (Padovani-Ferreira et al 2012)

Summary

Introduction

Parrotfishes (Labridae: Scarinae) are important for subsistence and commercial reef fisheries worldwide. Because parrotfishes perform important ecological roles in reef ecosystems, such as grazing and bioerosion (Bellwood & Choat 1990, Bonaldo et al 2014), the consequences of parrotfish harvesting have been widely investigated and discussed (e.g. Mumby 2006, Lokrantz et al 2010, Bellwood et al 2012, Bozec et al 2016). Life-history traits such as life span, growth, size and age at maturity, and rates of mortality and maturation directly affect population dynamics, and are critical to comparatively infer species vulnerability to overexploitation (Taylor et al 2014). Such information is often scarce, hampering the implementation of appropriate management policies to protect parrotfishes from overfishing

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Conclusion