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Noble Pen Shell – how we are trying to save it

Pinna nobilis is the largest shellfish in the Adriatic and Mediterranean Seas. This legally protected species (OG 144/2013) is endemic to the Mediterranean. It has an important ecological role because it filters seawater, which contributes to the increase of seawater transparency, and provides life supstrate for algae, sponges and other invertebrates. The highest measured height of this shell was 120 cm, and it lives in the coastal belt between 0.5 and 60 meters of depth.

The mass mortality event of this shellfish was first observed within the Spanish part of the Mediterranean Sea in autumn 2016, while in the Adriatic Sea, the first report of death was recorded in 2019. Due to the mass extinction of this species across the Mediterranean, the IUCN officially changed the status of the pen shell in 2019 from a sensitive species (VU) to a critically endangered (CR). Therefore, The Environmental Protection and Energy Efficiency Fund has launched the project Preservation of Pinna nobilis in the Adriatic Sea.

Figure 1. Noble pen shell – Pinna nobilis

As part of the service of production, installation and removal of collectors for catching larvae of noble pen shell (Pinna nobilis) as well as identification and extraction of juvenile pen shells from collectors in the Mljet National Park, the Association Sunce conducted two field research. In the period from 14 – 15.6.2021. 6 collectors have been installed at two locations, Hrid Štit and Veliko jezero, while on 11.11.2021. we conducted collector were pulled out and larval identification have been made.

Larval collectors, in previous research, have proven to be a good tool to protect larvae from predators. Collector nets are consisted of intricate nylon filament, such as onion or potato bags. They are placed inside polyethylene nets attached to the main rope. The entire system is attached to a small concrete berth and tied to a signal buoy with a rope that holds  the entire collector vertically in a column of water.

Figure 2. Installation of collectors

During the  removal of collectors, we carefully put them in plastic containers with sea water and transported them to the mainland.

Figure 3. Removed collectors

Extraction and identification were carried out carefully because the shells are fragile and 0.5-9 cm in size, and during the examination we paid a lot of attention not to miss any juvenile noble pen shell.

Figure 4. Juvenile invertebrates removed from collectors

During the examination, we found various juvenile invertebrates in the collectors, but unfortunately none of them were noble pen shell P. nobilis. We found juvenile individuals of shellfish, sea snails, crabs, shrimps, starfish, serpent stars, sea cucmbers and mantles.

Although the checkup of collectors installed as part of this study did not find larvae or juvenile of P. nobilis, due to positive findings in other parts of the Adriatic, primarily in Brijuni National Park, the installation of collectors in Mljet NP, as well as searching for adult individuals, should not be abandoned in the coming years.