The presence of bristlemouth, Gonostoma denudatum (Rafinesque 1810), from the coast of Northern Cyprus (Northeastern Mediterranean)

Gonostoma denudatum belonging to Gonostomatidae family are small fishes living in deep-sea around Atlantic and Mediterranean. They are vital species for plastic accumulation because they can be available in all depths of the water column during the day. In this study, it was aimed to present the recent record of G. denudatum, which captured from North Cyprus in May 2018. The total length of the specimen, which obtained from a depth of between 420 and 640 m, is 12.8 cm. Its photograph was taken and the catalogue number (MEUFC-19-11-108) was given. Morphometric characteristics were measured and calculated. The specimen is stored in the Museum of the Systematic, Faculty of Fisheries, Mersin University. Please cite this paper as follows: Akbora, H.D., Ayas, D., Çiftçi, N. (2020). The presence of bristlemouth, Gonostoma denudatum (Rafinesque 1810), from the coast of Northern Cyprus (Northeastern Mediterranean). Marine Science and Technology Bulletin, 9(1): 42-45.


Introduction
Gonostoma denudatum is a species belonging to the Gonostomatidae family of order Stomiiformes. They are bathypelagic species and live at a depth of 100-700 m (Badcock, 1984). They are found in East and West Atlantic waters reported as 14 cm (Quéro, 1990). Recently, this species has reported from Mersin Bay as 13.7 cm, TL (Bayhan and Erguden, 2019).
All Gonostoma species have a pigment spot on the back of the eye. To distinguish those species, natural pigmentations in different parts of their bodies investigated. G. denudatum has a deep pigmentation from the caudal fin base to the dorsalcaudal peduncle and the lower caudal-fin base. (Ahlstrom et al., 1984). G. denudatum is mostly feeding on Euphausiids and copepods (Badcock, 1984). In a study on the presence of microplastics in fish species living in the mesopelagic area in the Northwest Atlantic region, G. denudatum was found to be the fish having the most microplastic in the body (Wieczorek et al., 2018). With this study, an individual of G. denudatum caught off the coast of Northern Cyprus is reported. Besides, some morphometric of the fish is given.

Material and Methods
One specimen belonging to G. denudatum was caught from North Cyprus offshore waters. Sampling was carried out by a commercial trawl on May 17, 2018. The sampling depth ranged between 420 and 640 m. Sampling gear was prepared according to MEDITS procedures (Bertrand, 2002). The coordinates of the sampling area were 36.07227 N and 34.53326 E (Figure 1).

Figure 1. Sampling location of Gonostoma denudatum
Its photograph was taken and catalog number (MEUFC-19-11-108) was given. Species identification fulfilled according to information provided in Ahlstrom et al. (1984). Morphometric measurements were performed according to Bilecenoğlu et al. (2014) and compared with previous studies in the Eastern Mediterranean (Table 1). The specimen was preserved in 4% formaldehyde and deposited in the Museum of the Systematic, Faculty of Fisheries, Mersin University.

Results
The total length of G. denudatum (Figure 2), an Atlantic deep water species caught off the coast of Cyprus, was measured as 12.8 cm. The maximum total length reported in the literature is 14 cm (Quéro, 1990). In this case, the individual caught in the waters of Cyprus was mature.

Discussion
The fish caught in this study is a recent report for the Eastern Mediterranean and the first record for Cyprus. It has also contributed to the list of marine fish in Cyprus. In Table 1, morphometric features of G. denudatum compared with previous studies. Total length of the specimen was measured as 12.8 cm. However, caudal fin of the specimen was damaged during the fishing operation ( Figure 2). In this way, the actual total length of the sample could probably longer than 12.8 cm.
When the standard length of the sample compared with other studies, it is seen that this specimen is the biggest individual caught from the Eastern Mediterranean Sea. The most of percentage values of the G. denudatum in all compared studies are similar except; eye diameter, interorbital distance, postorbital length, and snout length. It is thought that this difference caused by other studies is due to a mistake made during the calculation. When the given lengths are converted to a percentage, it gives different results. Meristic characteristics couldn't be measured and compared because the fin rays were damaged.
G. denudatum listed as "Least Concern" in the International Union for Conservation of Nature (IUCN) Red List, and the population trend is unknown (Harold, 2015). Together with the recent record of G. denudatum from Mersin Bay (Bayhan and Erguden, 2019), and the present study, it can be said that this fish started to make a population in the Eastern Mediterranean region. Also, this study is the first record for Cyprus.
On the other hand, G. denudatum is a fish that can found at different depths during the day, and it hunted by various fish species (Badcock, 1984). Some of these predator species have commercial value for human consumption. According to Wieczorek et al. (2018), G. denudatum was found to be the most micro-plastic accumulating species in its body. Together with this information, it can be said that G. denudatum plays a crucial role in transporting plastic pollution back to humans via the food chain. A further study on this species about its plastic accumulation and transferring them via food chain is planned.

Conclusion
G. denudatum lives in the deep sea, and it's rarely seen in the Mediterranean region because of regular fishing activities not aiming at those depths. Now there are two recent records for G. denudatum in the adjacent areas means that those fishes started to increase their population. New researches can be done for those fishes about their plastic accumulation properties. They can be unique and powerful indicators for plastic pollution studies in the future.

Conflict of Interest
The authors declare that there is no conflict of interest.