How did the Cyprus freshwater blenny disappear?

The Cyprus freshwater blenny (Salariopsis [Salaria] cf. fluviatilis) is the only known native freshwater-dwelling fish species ever documented from Cyprus. The species S. fluviatilis is relatively widespread across the Mediterranean thanks to its ancestral species being of marine origin, and following the end of the Messinian salinity crisis approximately 5 million years ago, they went on to occupy freshwater habitats and subsequently evolved into what we refer to today as freshwater blennies. 

The Cyprus freshwater blenny was first discovered in 1909 by Roland L.N. Michell, the then commissioner of Limassol, who sent three specimens, known only from 2-3 torrents within his district, at the time identified as Blennius varus, to George A. Boulenger, at the Department of Zoology in the Natural History Museum, London. Observations of the fish were never again documented and today those specimens are still the only evidence that the fish species ever existed in Cyprus at all. 

The 1940s brought a wave of development imparting lasting environmental damage that would impact the blenny, and the freshwater ecosystems of Cyprus forever. Following on from the construction of the island’s first dam at Kouklia on the Diarizos River in 1900, the dam construction movement took off, particularly so in Limassol, starting with Akrounta dam on the Amathos River in 1947. The Amathos River was subject to further damming at Yermasoyia in 1968, and Arakapas in 1975, but other major perennial rivers in Limassol were also being dammed. The Kouris River, the largest river in Cyprus, and without doubt one of the 2-3 torrents that hosted the Cyprus freshwater blenny, was also dammed in 1956 on its Kantou and Kryos tributaries, followed by the Trimiklini dam in 1958, Agros dam on the Limnatis tributary, and the monstrous Kouris River dam in 1988, the largest dam on the island to this day. 

 

This alteration, fragmentation, and restriction of the main perennial rivers of Limassol was likely hugely detrimental to the Cyprus freshwater blenny which is adapted to clean, clear, fast-flowing rivers over cobble/pebble substrate, on which it lives and breeds, and which is unable to survive any significant loss in water quality or habitat loss. Owing to its marine ancestry, the larvae also undergo a 1-month planktonic phase requiring specific slow-moving shallow waters alongside their riverine habitats which act as refuges. 

The late 1940s also saw the start of the fight against Malaria, and in 1946, chief health inspector Mehmet Aziz initiated a three-year-long intensive chemical pesticide (DDT) campaign across the entire island. The approach was extreme and no stone was left unturned, Aziz’s team pioneered a technique of pouring petroleum onto water surfaces to prevent mosquito larvae from hatching and sprayed every living waterbody with insecticide repeatedly but as a result, every standing water body from rivers, lakes, marshes, ponds, pools, puddles, and paw prints was contaminated until no sign of mosquito life remained; it was an ecological disaster wrapped up in a societal success story. 

The combined outcome of the DDT campaign alone was likely sufficient to finish off what was left of any blenny populations in Cyprus by the 1950s, but amphibian and freshwater crab numbers also plummeted drastically at that time, and with that, so did the numbers of endemic water snakes (Natrix natrix cypriaca), and probably Natrix tessellata as well (now considered extinct). The impact was felt by biodiversity all over the island, with some species remaining in low densities till this day, and the chances that other native freshwater fish species or invertebrates have been eliminated before even being discovered is certainly possible. 

The drastic rise in coastal development for tourism, urbanization resulting in habitat loss and posing ever-increasing demands on water resources, as well as the boom in agricultural fertilizer and pesticide use, are the proverbial nail-in-the-coffin for any chance of a surviving population of the Cyprus freshwater blenny. Many of the lower river stretches they once would have inhabited are simply dry or not fed enough recharge water, are frequently in poor condition, or are simply no longer suitable to host the species. Only a very select few places within the natural range of the species could be suitable for a reintroduction project, and the “Rewilding the Cyprus Freshwater Blenny” project aims to achieve.