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Reproductive biology of yellowbelly flounder Rhombosolea leporina (Günther, 1862) and Rhombosolea spp.

Yellowbelly flounder Rhombosolea leporina is a culturally, recreationally, and commercially important flounder species in New Zealand. R. leporina contain high-quality flesh and sexually dimorphic growth, where females grow more rapid and reach an overall larger size than males. These biological characteristics make R. leporina an enticing opportunity for aquaculture. Aquaculture is becoming an increasingly important capability in global food security and an alternative to wild capture fisheries. Understanding and controlling the reproductive biology of an aquaculture species candidate is required to ensure successful production. The understanding of the reproductive biology also facilitates the effective management of wild stocks. Currently, there is a limited amount of literature on the reproductive cycle of R. leporina and no previous literature available on the sexual differentiation in Rhombosolea spp. This study provides a histological investigation into the reproductive cycle of adult female R. leporina, from November 2015 – October 2017, and sexual differentiation in Rhombosolea spp. juveniles. It was found that R. leporina spawns over a protracted seven-month season, from June to December. Based on the histological observations it was apparent that R. leporina have multiple group synchronous ovarian development with the potential of batch spawning. The investigation into sexual differentiation in the Rhombosolea spp. juveniles revealed gonadal cavities in all individuals, making ovarian cavities an inadequate criterion of sex. Therefore, it was found that the juveniles display sexual differentiation at 47 mm TL and 57 mm TL, for females with meiotic oocytes and males with spermatocytes respectively. Furthermore, spermatozoa were present in testes of a 71 mm TL male. These results provide insights into the precise timing of reproductive development and the size at sexual differentiation. The results presented here may facilitate further investigations into the endocrine regulation or manipulation of the reproductive biology of R. leporina. The implication of the investigation into Rhombosolea spp. juveniles illustrate the necessity of more robust investigations into the timing of sexual differentiation and initial gonadal development alongside insights into gene expression. Nonetheless, these findings provide essential background knowledge on the reproductive biology of R. leporina and Rhombosolea spp. juveniles for the potential of aquaculture and management of wild stocks.
Type of thesis
Koverman, R. (2018). Reproductive biology of yellowbelly flounder Rhombosolea leporina (Günther, 1862) and Rhombosolea spp. (Thesis, Master of Science (MSc)). The University of Waikato, Hamilton, New Zealand. Retrieved from https://hdl.handle.net/10289/13316
The University of Waikato
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