According to the information received, the mortality of about 200 kg of reticulated leatherjacket was observed in an area of 55 km from the coast of the Messen region to the Direstan Bay in the southern part of Qeshm Island. The distribution of fish carcasses was not uniform; in general, all carcasses belonged to Stephanolepis diaspros which were spotted along the beach. Following receiving this news, an expert group was formed at the Persian Gulf and Oman Sea Ecological Research Institute. The expert group analyzed the received images and videos and telephone interviews, and after receiving the frozen samples of the fish, they performed bioassays and autopsies. At the autopsy, the contents of the fish viscera could not be identified due to the small size of the carcasses, the heat of the air, and the autolysis of the intestinal contents. Evaluation of the received images and bioassay of fish samples showed that these fish were small in size and had the average length of 3.11 ± 3.1 cm and the average weight of 5.25 ± 5.9 g. The samples received were accurately and scientifically identified in the laboratory of the Persian Gulf and Oman Sea Ecological Research Institute. The species of dead fish was identified as Stephanolepis diaspros. This species belongs to the family Monacanthidae and the order Tetraodontiformes. Given that this fish is not in the catch basket of traditional, ornamental and even commercial fisheries, and no activities have been reported to exploit this type of fish in the southern part of the Qeshm Island, the capture fisheries hypothesis to explain reticulated leatherjacket mortality can probably not be considered strong. This species does not have a strong herding behavior and lives mainly in rocky beds. Therefore, the accumulation of homogeneous carcasses (fish usually found in fisheries by - catch were not observed next to these carcasses) and the scattering of carcasses in the 55 km long coastal area also refutes the hypothesis of capture fisheries. In the days leading up to the reticulated leatherjacket death, there were no reports of contamination or red tides. In addition, contaminants and red tides generally do not have a selective effect. Therefore, the probability of the effect of red tide on fish mortality is low. Although the visceral contents of this carcass were not traceable, feeding was generally a selective behavior for these fish and the nutritional factor may have contributed to the death of these fish. Also, when the phenomenon of mortality coincides with the maximum tide and considering the lunar eclipse phenomenon and the peak of tidal changes, factors such as dissolved oxygen in water may decrease to an unbearable level for this species and cause mass fish deaths.