Thursday, August 29, 2013

Samothraki Inland Water Fishes




Mid August 2013

On Samothraki we researched waters. Invertebrates, water quality, riparian vegetation, wetlands, birds, marine life, conservation issues of all sorts, and fish.

One of our team's passions is studying fish in inland waters - any waters inland of the shoreline. Fishes are interesting because they require really special conditions and resources for survival in any inland waters; and conditions on small islands are usually difficult. On Mediterranean islands, stable inland water conditions are scarce. This includes coastal lagoons, stream mouths, and any isolated water behind the beach-fronts (all wetland types of course) and streams of course. On islands, stream freshwater fishes have a hard time surviving - they cannot live without freshwater, so even a single dessication event can render them extinct from an island. On the other hand, marine fishes that swim into inland waters and move upstream need barrier-free movement opportunities and these conditions are rare or often influenced by human water exploitation and various barriers (road-crossings, dams, weirs).

What we found in Samothraki

Working on seven of the most representative of the basins we electrofished and used seine fry nets to collect fishes. Of these only Agistro, Fonias, and the Agios Andreas Lagoon had fishes! (see map below). Although we sampled using the above equipment 10 sites (8 using electrofishing) only six sites had fish. I present initial findings here- some spp. are still not confirmed as to their exact identification.

We found the following taxa of fishes in Samothraki's inland waters:

-Three species of Mugillids (Grey-mullets): these marine fish breed in the sea but enter fresh and brackish waters to feed - they love to feed on algae and detritus so they probably contribute to the cleansing of eutrophic lower stream reaches.

-Two or three species of Blennies: in this case we caught wholly marine Blennies - species that enter fresh and brackish waters but probably reproduce in the sea only.

-Two species of Gobies: One unidentified species and one common marine sand goby have been collected.

-One species of Atherina (sand-smelt): Collected only at Fonias river mouth in large numbers; they commonly enter rivermouths and lagoons when there is an opening to the sea.

-One species of Eel (Anguilla anguilla): Collected only in two rivers, in fact the two which have a good connection to the sea and are mostly perennially flowing towards the sea (Fonias and Angistro). The eel is a globally endanged species, so this find lends special value to the inland waters of the island.

So the inland waters ichthyofauna of Samothraki have a total of at least 9 fish species. This is good, but still we have  mysteries and unanswered questions. I was searching for a 'Dwarf Goby' called Knipowitschia caucasica, collected by Bulgarian researchers and published in the '60s; it was found nowhere.

Also, we found no true primary freshwater fishes. And this is remarkable since so much freshwater produced on the island flows to the sea - and at Fonias river for example we could have had a population of say River Blennies and even true primary freshwater fish. Our team searched hard - at one instant I had a hallucination that I saw a River Blenny at Fonias- it was probably a tadpole.



Samothraki Island and the river basin areas where we actively searched for fish using specialized fishing equipment; we visually inspected many other waters and small wetlands also.
The Fonias where we caught a 70 cm Eel - at mid-stream about 3 kms from the sea.
Walking along the Upper Fonias (Karya) at about 750 m. asl. Very slippery! 
The local super-widespread Ranid frog. This species is especially abundant where no eels exist!  Tsivdogiannis river.
The Upper Gria Vathra river at 700 m. elevation. Deep granite pools, slippery!!
Electrofishing the lower Yiali River in SE Samothraki. No fish here.
Its not just fish we find in river corridors: Dr. Yannis Karaouzas holds a beautiful Dahl's Whip Snake (Platyceps najadum) we caught in the upper part of the Fonias. Generally snakes were scarce; I saw only two Grass Snakes and this species after 13 field days on the island.
Fonias River mouth - only it and Agistros where flowing with an open mouth to the sea.
Atherina boyeri schoals caught inside the river-mouth of Fonias. Should have kept them for dinner...

I suspect these tiny Grey-Mullet fry are Mugi cephalus - caught at Fonias River Mouth.
Another Grey-Mullet, should be Liza Ramada. Many in the Fonias for about a 1000 m. upstream from the river mouth. But a large individual like this is only downstream due to anthropogenic barriers to movement.
Another Grey-Mullet; this time the Boxlip Mullet Oedalechilus labeo identified by the golden stripes and the charactersitics of the mouth-parts (broad and tall lip) Agistro.
Boxlip Mullet Oedalechilus labeo closer look at head. 
Boxlip Mullet Oedalechilus labeo in the Fonias stream, c. 150 m from the rivermouth in freshwater; this is the first time we catch this marine fish in freshwater! 
Team leader, Dr. N.Skoulikids inspects Katsambas river mouth - low water this year.
An anonymous wetland between Fonias and Ag.Paraskevi chapel. Brackish conditions, no fishes apparent but Mauremys rivulata (Terrapins) found! (One of only three sites we saw them on the island).
 Dr Zbigniew Kaczkowski expertly handling an Eel at Agistro river mouth pool.

Really BIG Eel at Agistro pool. Here we found four eels in a stretch of 80 m along the stream!

We saw three eels of this size on the island (here at Agistros - mid-stream section). Rare sight indeed!

Underwater snap-shot of the really BIG Eel at Agistros Stream.
Underwater snap-shot of a really small Eel (18 cm) hiding in sand in the lower Fonias river.
Agios Andreas Lagoon near Kamariotissa - great place for birding and fishing...
 Dr Zbigniew Kaczkowski with fry-net at Agios Andreas Lagoon near Kamariotissa.
'Mystery' Goby caught at both Agios Andreas Lagoon (here) and at Agistros river mouth. All were small - but abundant in Agios Andreas Lagoon. 
'Mystery' Goby (unidentified yet). It has a "salt-and-pepper" markings pattern and biggish head similar to a Gobio cobitis but we need to re-look at it carefully. The other fish is a Rusty Blenny (Parablennius sanguinolentus), both  at Agistros River Mouth. This particular Blenny species feeds on algae and is quite frequently seen at small-stream river mouths. 
Sand Goby, Pomatoschistus cf. marmoratus was common in Ag. Andreas lagoon.
Green Goby, Zosterissesor ophiocephalus was common in Ag. Andreas lagoon.
Peacock Blenny, Salaria pavo was common in Ag. Andreas lagoon.
Road-barrier to fish movements at Agistro. However some young eels do pass upstream. 

River crab (Potamon sp.) at Fonias river (Underwater shot after he bit me on the finger really hard). 
Terrapin (Mauremys rivulata) - like fish, this species also requires water! Rare on Samothraki (this one at the Anonymous wetland, mentioned above).

Ms. Anastasia Lambou taking notes at the nearly totally-dried-out Vdelolimni Lagoon. 

Researchers Mrs. Vlami and Ms. Lambou at the Vdelolimni Lagoon.

Dr. Skoulikidis carrying the electrofisher and nets through the dry alluvial fan below Yiali canyon.
The expedition team; local friend Mr. Yorgos Delos (at L.) took us by boat to the isolated river-mouth beach of Yiali.  



(Note: for further information please read: http://zogaris.blogspot.gr/2013/08/samothraki-island-natural-history.html)



















2 comments:

  1. congratulation for your results! ...enjoy Samothraki's nature! and about Overgrazing???

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  2. My warmest regards to our former Director! An honour to hear from you. I mention the issues of overgrazing in a recent blog post...

    http://zogaris.blogspot.gr/2013/08/samothraki-island-natural-history.html

    ReplyDelete