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)

Abstract

Background. We present length–weight relations (LWR) and describe the reproductive biology of five species of coral reef fishes from Papua New Guinea (PNG).  Each of these species are targeted by artisanal- and small-scale commercial fisheries throughout the country. As such the purpose of this study was to provide baseline reproductive information that can be used for future evaluation and management of the fishery. Materials and methods. We used recently developed methods for rapid, low-cost, on-site, histology-based reproductive analysis that requires minimal research infrastructure.  These methods use standard techniques (e.g., plastic embedding) that have been modified such that work can be conducted in remote field settings without electrical service. We studied the following fish species: the teardrop threadfin bream, Nemipterus isacanthus (Bleeker, 1873); the dash-and-dot goatfish, Parupeneus barberinus (Lacepède, 1801); the blue sea chub, Kyphosus cinerascens (Forsskål, 1775); the striated surgeonfish, Ctenochaetus striatus (Quoy et Gaimard, 1825); and the orange-lined triggerfish, Balistapus undulatus (Park, 1797). Results. In all species, length was an approximately cubic function of weight.  Female B. undulatus mature at a smaller size than males; in the other four species males mature at a smaller size.  Nemipterus isacanthus, K. cinerascens, C. striatus, and B. undulatus are gonochores.  Females are rare or absent in the largest size classes of N. isacanthus, P. barberinus, C. striatus, and B. undulatus.  For P. barberinus and B. undulatus, size classes well below maximum observed size are responsible for the majority of egg production. Conclusion. Our results differed markedly from those of macroscopic and data-deficient approaches and may help to avoid unnecessary management actions.  Further, an emergent pattern challenges a current paradigm in reef-fish conservation and management; contrary to a general assumption for many reef-fish species, the largest size classes of at least three species did not have the highest per-capita fecundity.  Because females were rare or absent in the largest size classes, smaller fish are responsible for the majority of egg production.  Thus, for coastal communities dependent upon reef fishes for sustenance, our results suggest it may be easier to balance food needs and conservation by fishing across a broad size range.  Further, because of diminished concern about targeting the larger size classes commonly assumed to be responsible for the majority of egg production, doing so will simultaneously promote adequate reproductive output.

Keywords

• size-at-maturity
• sexual pattern
• sex ratios
• batc