Aspects of the reproductive biology of the marine ornamental Vagabond Butterflyfish Chaetodon vagabundus Linnaeus, 1758 (Pisces, Chaetodontidae) from Iligan Bay, Southern Philippines

The reproductive biology of ornamental fish species from coral reefs is poorly studied despite increasing demand in the aquarium trade industry. Aspects of the reproductive biology of the Vagabond butterflyfish, Chaetodon vagabundus Linnaeus, 1758, from Iligan Bay, Southern Philippines were investigated from August 2021 to August 2022. Monthly samples of 30 to 45 individuals per class size with a range of 9 to 14.1 cm (TL) were collected to examine the sex ratio, maturity stages and spawning period, gonadosomatic index (GSI), length at first maturity (L50) and the batch fecundity (BF) of the species. The sex ratio showed female dominance (1:1.42) among size classes and across months. The spawning period indicates a peak during the inter-monsoon or warm months (April and May) and extends beginning of the Southwest monsoon period (June and July). These were supported by the relatively higher gonadosomatic index (GSI) recorded during these months. Histological examination showed that the ovaries during this period had the presence of numerous tertiary vitellogenic and hydrated oocytes and post-ovulatory follicles. At the same time for testes, there are occurrences of dense spermatozoa in the lumen of tubules in testes. This served as confirmatory evidence in support of the spawning period. The length at first sexual maturity of males (10.58 cm TL) was slightly shorter than females (10.91 cm TL). Fecundity increased with the fish’s total length and weight showing a non-linear relationship that was best described by a power function. This study highlighted the valuable data produced that are required for the management of the population stock of this species.