Comparisons of body sizes at sexual maturity and at sex change in the parrotfishes of Hawaii: input needed for management regulations and stock assessments

Abstract

First estimates of sex allocation patterns and body size-at-sexual maturity and at protogynous sex change are presented for the five major (including one endemic) species of parrotfishes of Hawaii. Median body size at initial maturation as a female (LM50) and at protogynous sex change from adult female to adult male (LΔ50) varied greatly among the five species. Estimates of LM50 were about 14, 17, 24, 34 and 35 cm fork length (LF) in palenose Scarus psittacus, Pacific bullethead Chlorurus spilurus, stareye Calotomus carolinus, spectacled Chlorurus perspicillatus and redlip parrotfish Scarus rubroviolaceus. Values of LΔ50 were c. 23, 27, 37, 46 and 47 cm LF in the respective species. Length at female maturation was proportional to maximum body size (Lmax) of the respective species, ranging from 50 to 72% and averaging 62% of Lmax across species. LΔ50 was also proportional to Lmax, ranging from 82 to 97% and averaging 92%. Males of both pairs of Scarus and Chlorurus spp. reported here are diandric. Only one of the five major species (C. carolinus) is functionally monandric, with either all or nearly all males secondarily derived from adult females. The broadly differing absolute body sizes at sexual maturation and at sex change among the five species have important implications for improving regulatory size limits for parrotfishes in the State of Hawaii, where parrotfish species have historically been managed based on a single minimum size limit of 30·5 cm LF. This study provides a model demonstration of why catch data for parrotfishes, and other size-structured reef-fish populations, should be recorded either by species or by functional size-groups of species that allow setting more meaningful minimum size limits.

Growth and maturation of the redlip parrotfish Scarus rubroviolaceus

“…Hence, actual life span of the species in American Samoa may be greater than represented. The species reached 50% female maturity at 75% of its estimated asymptotic L F , which is similar to ratios from Hawaii (68%; Howard, 2008;DeMartini & Howard, 2016) and Guam (72%; for the same species.…”

“…rubroviolaceus is of prime importance to commercial fishers. It represents the highest landed scarine species by mass in Hawaii, the Commonwealth of the Northern Mariana Islands and American Samoa and is the third highest in Guam (Houk et al ., ; DeMartini & Howard, ; NOAA Commercial Fisheries Bio‐Sampling Program, unpubl. data).…”

“…An increase in mean I G values during winter months (peak, July to August) suggests that reproductive activity may increase during this period, but it is clear that no stark peaks in reproduction occur temporally for this species. DeMartini & Howard () demonstrated a pronounced peak in I G values for the same species during late winter in Hawaii, where temporally distinct patterns of reproduction would be more likely with increased seasonality at greater latitude (Conover, ). Most scarines have prolonged spawning seasons with reproductive events co‐ordinated with outgoing tidal currents, but little else is known regarding reproductive cycles of S .…”

Hazards of managing disparate species as a pooled complex: A general problem illustrated by two contrasting examples from Hawaii

“…Commercial catches of parrotfish, bottomfish and all other taxa are recorded by the State of Hawaii, DLNR, DAR. Seven (mostly five: DeMartini & Howard, ; Howard, Schumacher, & Parrish, ) species of parrotfish are recorded as a single, species‐pooled taxon (‘uhu’, the general Hawaiian word for parrotfish), even though many of the component species (and even some colour phases within species) are visually distinguishable and are in fact known by distinct Hawaiian names (Randall, ; Titcomb, ). Deep‐7 bottomfish, on the other hand, are recorded by species in the commercial catch records of Hawaii, as is the ‘uku’ grey snapper ( Aprion virescens , Lutjanidae), the major component of the non‐Deep‐7 Bottomfish Management Unit Species (BMUS).…”

Rapid reproductive analysis and length–weight relations for five species of coral-reef fishes (Actinopterygii) from Papua New Guinea: Nemipterus isacanthus, Parupeneus barberinus, Kyphosus cinerascens, Ctenochaetus striatus (Perciformes), and Balistapus undulatus (Tetraodontiformes)

“…Advances in knowledge of the reproductive biology of Indo-Pacific reef fishes are ongoing (DeMartini et al 2014, Taylor et al 2014, Ohta and Ebisawa 2015, DeMartini and Howard 2016, Rhodes et al 2016, Schemmel et al 2016. However, none of these studies use histological methods that can be readily employed in developing countries (with limited research infrastructure) and easily learned by local marine resource-management staff (who often may be inadequately trained).…”