Introduction
Since the construction of the Suez Canal in the late nineteenth century, the Mediterranean Sea has been exposed to the largest bioinvasion recorded in modern history (Galil, Reference Galil, Lutmar and Rubinovitz2023). The proximity to the Suez Canal has turned the eastern Mediterranean, and the Israeli coast in particular, into a hotspot and dispersal hub of non-indigenous species (NIS), with more than a hundred alien fish recorded to date, most of them of Red Sea and Indo-Pacific origin (Golani, Reference Golani2021). Among the non-indigenous fish reported from the Mediterranean, only few are members of cryptobenthic families (following the definition by Brandl et al., Reference Brandl, Goatley, Bellwood and Tornabene2018) and strictly reef-associated.
The Pseudochromidae (commonly known as dottybacks) is a family of small (usually less than 10 cm SL), reef-associated fishes, containing 154 species in 24 genera, that are widely distributed throughout tropical and subtropical regions of the Indo-Pacific (Froese and Pauly, Reference Froese and Pauly2024). Dottybacks are often brightly coloured, with many species (e.g. Pseudochromis fridmani, P. aldabraensis, P. elongatus, P. springeri) popular in the marine aquarium trade. Pseudochromines, which form the largest subfamily, are mainly associated with small caves and interstices in sponges and branched corals (Gill, Reference Gill2004). Recently, we observed and photographed a bluespotted dottyback, P. persicus Murray, 1887, off the Mediterranean coast of northern Israel. Pseudochromis persicus is native to the western Indian Ocean, known mainly from the Persian Gulf and the Arabian Sea (Gill and Mee, Reference Gill and Mee1993; Gill, Reference Gill2004; Alavi-Yeganeh et al., Reference Alavi-Yeganeh, Sheikhzadeh and Ghanbarifradi2024). This is one of the largest species in its genus, attaining approximately 15 cm TL (Gill, Reference Gill2004). In its native range, it has been observed in shallow reef areas ranging from 1 to 25 m deep, where it feeds on small crustaceans and benthic invertebrates (Gill, Reference Gill2004). In this article, P. persicus is reported from the eastern Mediterranean Sea for the first time, more than 4000 km from its natural distribution.
Materials and methods
On 14 October 2024, a single individual of P. persicus was detected during a recreational snorkelling activity in Bat Galim, Haifa, on the northern coast of Israel (32°50′02.6″N, 34°58′08.3″E) in the eastern Mediterranean Sea (Figure 1). The reef in Bat Galim is a large continuous limestone rocky platform and a part of the upper Rosh Carmel underwater ridge. The individual was observed at a depth of 2 m, where the reef is characterized by large flat areas interrupted by small ledges and crevices. The individual was observed on two more occasions, on 24 October and 26 October, at the same location where it was first detected. On 29 October the fish was not observed at the site. The individual was photographed in stills and video using an underwater camera Olympus Tough TG-7 and its total length was estimated in situ. Species identification was based on the images and followed Gill (Reference Gill2004). Identification was further validated through personal communication with Gill A. based on the photos taken.
Figure 1. Precise locality where Pseudochromis persicus was sighted.
Results
We report the first sighting of P. persicus in the Mediterranean Sea. A mature individual, estimated at 14 cm TL, was observed swimming in and out of a rock crevice, displaying apprehensive behaviour towards the observers. Video of the sighting can be accessed on YouTube (https://www.youtube.com/watch?v=CeLruWLMYaM&t=2s).
Systematics
Class Actinopterygii
Order Perciformes
Family Pseudochromidae Müller & Troschel, 1849
Genus Pseudochromis Rüppell, 1835
Pseudochromis persicus Murray, 1887
Common name: Bluespotted dottyback
Type locality: Persian Gulf
Description and diagnostics
Brief description of the Mediterranean specimen observed, based on photographs (Figure 2): Body elongated and slightly compressed laterally. Eyes protruding. The mouth oblique with thick lips and a slight gape, featuring one pair of enlarged caniniform teeth anteriorly on the upper jaw and one pair on the lower jaw. Lower lip incomplete (interrupted at the symphysis). The maxilla extending to a vertical at anterior edge of the eye. Caudal fin rounded. Live coloration of the head and body dark blue to brown, and the dorsal, pelvic, anal and caudal fins dark blue with bright blue margins and spots. The spots on the dorsal and anal fins organized in two rows at the base of the fin. Spots on the caudal fin scattered in at least 11 rows along caudal fin rays. The pectoral fins rusty yellow to orange. Cheeks with two bright blue oblique stripes stretching upwards from the margins of the upper lip. The upper stripe short and stretches to two-thirds the distance from the eye. The lower stripe longer, interrupted and reaching below the posterior margin of the orbit. Lower part of the cheeks and operculum with faint blue spots and streaks. Iris reddish brown and a bright yellowish suboval ring framing the pupil. A large black blotch about the size of eye diameter on the operculum behind upper edge of preopercle, edged anteriorly with a bright blue fine bar, nearly vertical. Pseudochromis persicus highly resembles P. omanensis in meristic, coloration, morphometric details, and in attaining a large size (both reach ~15 cm TL) (Gill, Reference Gill2004). However, the observed individual had bright blue to turquoise spots scattered over the sides of the body, including its anterior part, which are considered a distinguishing characteristic of P. persicus (see: Gill and Mee, Reference Gill and Mee1993; Gill, Reference Gill2004; Anthony Gill, pers. comm.).
Figure 2. Pseudochromis persicus in the Mediterranean Sea. Photos by S. Ohayon.
Discussion
The live coloration and size of the pseudochromid observed in Bat-Galim reef, Israel, agrees with the description remarks of P. persicus by Gill (Reference Gill2004), and distinguishes it from other congeneric species. The combination of a dark body, brown to rusty pectoral fins, pelvic, dorsal, anal and caudal fins with bright blue spots and margins, suboval line around the pupils and territorial behaviour, distinguishes it from any other cryptobenthic fish. While nine Pseudochromis species are known from the Red Sea (Golani and Fricke, Reference Golani and Fricke2018), P. persicus, known only from the Persian Gulf and Arabian Sea, is the first non-indigenous pseudochromid documented in the Mediterranean Sea. Its remote native range, combined with limited swimming abilities, raises the assumption that P. persicus arrived in the Mediterranean Sea through the Suez Canal in ships' ballast water. The proximity of Bat Galim reef to Haifa port strengthens this possible pathway. Only two more species, Istiblennius meleagris and Tridentriger trigonocephalus, have thus far likely reached the region by shipping (Goren et al., Reference Goren, Gayer and Lazarus2009; Rothman et al., Reference Rothman, Gayer and Stern2020; Golani, Reference Golani2021). Nonetheless, it is also possible that P. persicus is present but rare in the Red Sea, and interestingly, high probability of occurrence in the Red Sea was modelled by AquaMaps (2019). The Steinhardt's shrimp-goby (Cryptocecntrus steinhardti Goren and Stern, Reference Goren and Stern2021), for example, another benthic fish with cryptic behaviour, was discovered in the Mediterranean coast of Israel before it was first sighted in the Gulf of Aqaba, where it is native and presumably rare (sighting available in iNaturalist: https://israel.inaturalist.org/observations/106481693). An alternative introduction pathway may be through the marine aquarium trade, where the brightly coloured members of the family Pseudocromidae are popular. Nonetheless, to our best knowledge, P. persicus is not a common species in the trade.
The Israeli coast serves as an important entry station and breeding ground for NIS (Galil et al., Reference Galil, Mienis, Hoffman and Goren2021). Additionally, the discovery rate of new non-indigenous fishes in Israeli waters has been rising since the early 2000s, likely due to successive enlargements of the Suez Canal and research effort (Galil et al., Reference Galil, Mienis, Hoffman and Goren2021). A recent spatio-temporal analysis suggests that most NIS fishes arriving at the Mediterranean require approximately four years to spread from the first record towards the second region of detection, and 22 years in total to reach the central Mediterranean Sea from the Suez Canal (Vagenas et al., Reference Vagenas, Karachle, Oikonomou, Stoumboudi and Zenetos2024). The study also highlights that over half of the introduced fishes have been established in the Mediterranean in less than 10 years. Once an NIS is established, management or other controlling measures are limited or impossible; hence, prevention measures are considered the only effective strategy. Early detection of species with limited dispersal capabilities, in enclosed or semi-enclosed areas (e.g. aquaculture infrastructures, marinas and lagoons) may facilitate eradication attempts. With regards to cryptobenthic reef fish, early detection and monitoring programs may be facilitated by engaging citizen scientists, equipped with waterproof cameras.
Data
The authors confirm that the data supporting the findings of this study are available within the article.
Acknowledgements
We wish to thank Dr Anthony Gill for his useful advice. We also wish to thank the reviewers and the handling editor for promptly completing the review process.
Author contributions
S. Ohayon and W. Neser detected and documented the fish and wrote the manuscript. S. B.-S. Rothman identified the specimen and equally participated in writing the manuscript.
Financial support
This research did not receive funding from any agency, commercial or not-for-profit sectors.
Competing interest
None.
Ethical standards
This article did not require any research permit.
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