POSIDONIA OCEANICA MONITORING and FISH SURVEYS

Unfortunately, during 2007 our survey work was curtailed due to Gaynor’s illness. However, a group of Belgian divers took up the challenge to investigate the area that we have called  “Blenny City”.

“BLENNY CITY” SURVEY - September 2007

This survey was carried out by Belgian Marine Biologists, Marijn Rabaut, Joke Lenoir and Katja Guilini following study of Gaynor’s photographic records of each species, discussion of habitat and the influence of sea conditions, and practice/observational dives.

The following data was collected from within the littoral community of a stretch of shallow (1-3 meters) rocky coast given the name of “Blenny City” because of the number and variety of blennies observed there. It lies at Lat: N42 07 Long: E003 10, east of Illa Mateau, near the town of L’Escala, Costa Brava.

The data was obtained by two or three divers swimming in parallel at varying depths whilst recording the number of each species of blenny observed during dives lasting 45 minutes. The numbers from each diver were collated for each species on each date.

TYPE OF BLENNY DATE 16/9/07 17/9/07 20/9/07 22/9/07 NUMBER OF BLENNIES Parablennius pilicornis (Variable blenny) 10 2 2 8 Lipophrys canevae (Reticulated blenny) 8 10 2 9 Parablennius zvonimiri (Staghorn blenny) 32 8 7 15 Parablennius gattorugine (Tompot blenny) 0 0 2 4 Aidablennius sphynx (Sphinx blenny) 6 13 5 26 Parablennius incognitus (Surprise blenny) 30 18 3 14 Lipophrys pholis (Shanny) 8 11 2 5 Parablennius rouxi (Striped blenny) 5 2 1 4 Parablennius marmoreus (Seaweed blenny) 13 2 1 3 Tripterygion tripteronotus (Red triple-fin) 58 50 19 47 Tripterygion delaisi (Yellow triple-fin) 28 20 9 13 Tripterygion melanurus minor (Small triple-fin) 9 7 4 8 SEA CONDITIONS CALM CALM SURGE CALM

The identity of the “Seaweed blenny” remains under investigation, and will only be positively resolved by genetic typing. Local observations and photographs taken over the past three years suggest a strong similarity with one of the photographs on FISHBASE labeled as Parablennius marmoreus (Seaweed blenny). However, this may be inaccurate as other photographs shown on that FISHBASE page depict Parablennius pilicornis (Variable blenny) although are also labeled as Parablennius marmoreus.

The Sphinx blennies favour a specific algae-covered rock where they graze despite much traffic from divers and snorkelers during the summer months. In contrast the Reticulated blennies are very shy and quick to hide in their holes during surge conditions or the presence of divers.

The Triplefins are particularly plentiful in this area, but difficult to differentiate in September when they are not wearing their bright mating colours. They are also seen in deeper areas.

The Striped blennies, Variables, Staghorns, Seaweed blennies and Tompots are also observed at depths ranging to 20 meters, whilst the Shannies and Sphinxes are only seen in the shallow area studied here.

Earlier surveys can be viewed on the next pages

The 2005 and 2006 Posidonia oceanica surveys revealed that the meadow in Cala Montgo is doing well. In fact, it is so healthy and the water quality so good that the seagrass flowered in October 2006. The flowers may not look very spectacular, but when the buds are open they are a pretty yellow colour. The most amazing thing was how abundant they were throughout the meadow. Contrary to what I have read, the flowers were very plentiful with several within a square meter.

As well as being available on this site the data is freely given to Marbef, for inclusion in their species database, and CRAM a local Catalan organisation concerned with protecting Posidonia oceanica and rescuing marine mammals and turtles. Photographs are also freely donated to Marbef and Fishbase.

Thanks to all who volunteered in 2006 and 2007. Keep in touch and we hope to see you all again very soon.