Morphological distinctions between males and females of a species are referred to by sexual dimorphism. It may result from various selection pressures affecting either sex or both and may occur in any dioecious species, including Green Swordtail fish, which are sexually reproductive. This study examined the different rheotaxis responses of Xiphophorus hellerii based on different sexes and morphological features. We analyzed ten adult males, ten gravid females, and ten non-gravid females of Xiphophorus helleri collected down the river and transferred into the column. We counted the number of the individual that performed positive rheotaxis (+), negative rheotaxis (-), and indifference response (0). The result showed different rheotaxis responses shown by male, non-gravid female, and gravid female X. hellerii. The highest percentage of positive rheotaxis response (movement against the current) was shown by non-gravid female X. hellerii, reaching up to 89%. Morphological differences between male, non-gravid female, and gravid female X. hellerii appear to affect the orientation and ability of X. hellerii in giving response against current and certainly has an impact on their survival in nature.

The northern region of Sekotong Bay is well known for its secluded, and it potentially provides a unique habitat for the coral reef ecosystem. There are only two islets located in that outermost area, namely Gili Rengit and Gili Layar. This study aims to describe the reef fish community structure in both islands. The study was conducted in the northern and southern parts of each islet using UVC (Underwater Visual Census) method along a 50×5 m belt transect. A total of 64 species of reef fish from 18 families were identified. The majority of fish found were resident obligate and dwellers. Moderate diversity index, as well as the low presence of indicator and targeted fish species, indicates the susceptible stability of reef fish community in the outer islet of Sekotong Bay.

Abstract. Ghafari MIA, Fitrianti V. 2021. Pioneer assessment on megabenthic community suggests the recent ecological condition of coral reef in Senggigi Beach, Western Lombok Island, Indonesia. Indo Pac J Ocean Life 5: 14-21. Megabenthic communities are among the excellent bioindicator used nowadays. This study was the first to conduct in Senggigi Beach and provide preliminary useful information regarding the condition of coral reef ecosystem on-site, through assessing the megabenthic community from 2019-2020 to 202-2021. Benthos Belt Transect (BBT) method was used to collect data from 6 different observation sites. There are 3 groups of targeted megabenthic fauna assessed: the bioindicator group (sea urchin and blue starfish), the corallivorous group (drupella snail and crown-of-thorns starfish), and the commercially valued group (edible sea cucumber, giant clam, spiny lobster, and commercial top shells). Sea urchin was found to dominate all stations, indicating a decreasing live coral cover after bleaching. Presence of corallivorous megabenthos was very rare, as it is not a potential threat to corals. There is a trend of increasing density of edible sea cucumber and giant clam by 30% and 50% respectively, with a mass giant clam recruit in 2021. We suspect less or no impact of anthropogenic activity to megabenthic community dynamic in Senggigi Beach to date, but their community dynamic is purely influenced by the decline condition of coral reef ecosystem due to recent 2016 mass bleaching.