First Report on Reproductive Features of Shadow Driftfish Cubiceps whiteleggii (Perciformes: Nomeidae): An Effort toward Sustainable Management

Fish of the Nomeidae family are a significant part of marine food webs and are an emerging fisheries resource. The formulation of sustainable management and conservation strategies is constrained by the lack of comprehensive research on the population biology of any of these species. We, therefore, studied reproductive aspects of Cubiceps whiteleggii as a representative of Nomeidae. We used a biological index (gonadosomatic index), as well as macroscopic (visual observations of the surface and transverse ovary sections) and microscopic analyses, in search of proxies for estimating the ovarian maturity status. Samples were collected from April 2014 to December 2017 in Kagoshima Bay, Japan. Asynchronous ovary development in C. whiteleggii indicated multiple spawning during a single reproductive season. Ovarian maturity stages were divided into six groups based on the appearance of the most advanced oocytes, post-ovulatory follicles, and atretic oocytes: immature, maturing, mature, spawned, spent, and resting. Females with ovaries at mature or spawned stages were defined as sexually mature individuals. The size at 50% sexual maturity was estimated to be 126 mm standard length. The spawning season was estimated to last from July to November. Both biological and macroscopic indices were found unsuitable to be used as independent indices in estimating reproductive aspects requiring scientists and managers to search for better alternatives. The conceptualization of appropriate management protocols for the fishery should be aided by these findings, which are the sole knowledge available on the reproductive features of this species. This will ensure its sustainable harvest and make it easier to conduct future research on fish reproduction.