Fluctuations in Asymmetry of Common Carp (Cyprinus carpio) at the Kabat Fish Hatchery Center in Banyuwangi, Indonesia

The common carp (Cyprinus carpio), among the top five cultivated fish commodities, is a crucial animal protein source in many developing countries. Numerous breeding programs have been implemented to enhance the productivity and quality of common carp fingerlings, resulting in a variety of body colors and morphologies. Quality fingerlings ensure the sustainability of carp aquaculture. The Kabat Fish Hatchery Center (located in Banyuwangi Regency, East Java Province, Indonesia) is a Technical Implementation Unit of the Department of Food and Marine Affairs of Banyuwangi Regency Government, providing common carp fingerlings to farmers in the Kabat District and surrounding areas. However, a decline in the quality of common carp fingerlings has occurred at this hatchery, characterized by increased abnormalities leading to low survival rates and growth rates. Many fish hatcheries face similar issues of declining fingerling quality, including high levels of abnormalities and low viability and survival rates caused by inbreeding. This study aims to obtain quantitative information on the level of asymmetry in common carp fingerlings at the Fish Hatchery Center (FHC) Kabat as a reference for breeding programs.

A total of 200 common carp fingerlings with a total length of 5-7 cm were obtained from FHC Kabat. The fluctuating asymmetry magnitude (FAm) and fluctuating asymmetry number (FAn) were observed, both of which fluctuated. To calculate them, bilateral meristic characteristics measured included pectoral fin rays, pelvic fin rays, and lateral line scale counts. It was found that there was fluctuating asymmetry occurrence in FHC Kabat, with the highest FAm and FAn obtained on the lateral line scale. This implies inbreeding leading to decreased hatchery productivity, necessitating the introduction of broodstock from other areas.

The highest FAm and FAn on the lateral line scale also occurred in previous research on Nile tilapia (Oreochromis niloticus) and hybrid grouper (Epinephelus fuscoguttatus & Epinephelus lanceolatus). Within species, fluctuating asymmetry refers to the non-directional variation from the ideal bilateral symmetry structure. Asymmetric characteristics of paired right and left sides have been associated during ontogeny with genotype and environmental variation and are viewed as noise in development. Lower energy priority for growth compared to other paired organs leads to significant fluctuation in the meristic bilateral asymmetry feature of paired organs. This study indicates fluctuating asymmetry values (FAm and FAn) occurring on the lateral line scales. This is presumed to be because the number of lateral line scales is higher than the number of pelvic and pectoral fin rays, leading to higher energy expenditure in the development of lateral line scales.

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