Population study of the fan shell <i>Pinna nobilis</i> L. in Malo and Veliko Jezero of the Mljet National Park (Adriatic Sea)

Abstract

SUMMARY: Although previous studies have noted the presence of the bivalve Pinna nobilis Linnaeus, 1758 in Mljet National Park, there is a lack of basic knowledge of this endangered species. The present study was initiated as part of a long-term investigation of P. nobilis density and growth with the aim of gaining a better understanding of this species' population dynamics, as well as evaluating the efficiency of protection measures of P. nobilis in Mljet National Park. Density, population structure, growth of tagged individuals and epibionts on P. nobilis were studied using SCUBA diving in 1998 and 2000 along four transects in Mljet inlets, Adriatic Sea. The density of P. nobilis ranged from 0.20 ind/m 2 on transect MLJ-9 in Malo Jezero in 1998 to 0.02 ind/m 2 on transect MLJ-5 in Veliko Jezero in 2000. Individuals measured in 1998 were significantly smaller than those measured in 2000. Growth curves were constructed from data collected by tagging and re-measuring 47 individuals. A decrease in density along some of the transects and the disappearance of 24 tagged individuals in 2000 is suggestive of poaching. The results of the present study indicate recovery of the P. nobilis population in Mljet lakes, but also provide evidence for the illegal removal of this protected species.

Genetic structure of the endangered species Pinna nobilis (Mollusca: Bivalvia) inferred from mtDNA sequences

“…m −2 (GalinouMitsoudi et al 2006), comparing to the highest density (0.020-0.200 ind. m −2 ) of a studied Mediterranean "recovered" population in the East Adriatic Sea (Šiletić & Peharda 2003).…”

“…Although there are several publications referring to population studies of P. nobilis (Richardson et al 1999;Šiletić & Peharda 2003;Katsanevakis 2005;GalinouMitsoudi et al 2006;Garcia-March et al 2007), only a single study deals with a partial COI mtDNA sequence in the Pteriomorphia subclass in which P. nobilis belongs (Matsumoto 2003), but it does not include P. nobilis. There is neither nuclear nor mtDNA sequence, as well as no genetic analysis of the species published.…”

Habitat use by a large population of <em>Pinna nobilis</em> in shallow waters

“…At present, despite decades of combined legal species and habitat protection, common abundances of P. nobilis are less than 1 individual per 100 m -2 (Guallart and Templado 2012), although aggregations of more than 20 individuals per 100 m -2 have been observed in some areas where the species is still abundant (e.g. Siletic and Peharda 2003, Rabaoui et al 2008, Addis et al 2009). …”

“…Possibly for this reason, most studies indicating high P. nobilis densities have only been carried out in areas smaller than 10000 m -2 and the total population reported is usually much lower than 1000 individuals (e.g. Galinou-Mitsoudi et al 2006, Garcia-March and Kersting 2006, García-March et al 2007a, Siletic and Peharda 2003, Addis et al 2009, Zakhama-Sraieb et al 2011). More exceptionally, some studies have explored areas larger than 100000 m -2 and reported populations of thousands of individuals, in addition to very high local densities in discrete areas (Katsanevakis 2006, Katsanevakis andThessalou-Legaki 2009).…”

Densidad, estructura de tallas, orientación de las conchas y colonización de epibiontes de la nacra <i>Pinna nobilis</i> l. 1758 (Mollusca: Bivalvia) en una zona estuarina de Cerdeña (Mediterráneo Occidental).

“…Adults were also well represented; in fact large live and dead individuals (>80 cm Ht) were found, although with lower frequency values than small individuals. these large specimens are more than 20 years old (García-March et al,2007a;siletic and Peharda, 2003), and are of particular importance in the spawning and recruitment processes because they represent the source of new individuals.…”