The Mediterranean endemic fan mussel Pinna nobilis is suffering an ongoing basin-scale mass mortality event (MME) since 2016. As most Mediterranean populations have collapsed, the species has been declared as Critically Endangered in the IUCN Red List of threatened species. In an effort to track the progress of the MME and provide updated information on the status of the species in the Greek seas, we compiled data collected through dedicated surveys and opportunistic assessments during 2019 and 2020. A total of 14589 fan mussel individuals, of which 81.1% dead, were recorded in 258 site surveys. Of the remaining 2762 live individuals, 256 were juveniles. Two marine areas which still sustain living populations were identified, namely Kalloni Gulf (Lesvos Island), and Laganas Bay (Zakynthos Island). The inner part of Kalloni Gulf appears to maintain the largest surviving population of the species in the eastern Mediterranean, with an abundance estimate of 684000 individuals (95% confidence interval: 322000-1453000). Solitary, potentially resistant, scattered individuals were recorded in several sites. Other previously abundant populations that had been assessed in the past, specifically those of Lake Vouliagmeni (Korinthiakos Gulf), Souda Bay (Crete) and Gera Gulf (Lesvos Island), and which collectively summed up to ~350,000 individuals, have now been wiped out. Our results document the collapse of most P. nobilis populations throughout the Greek seas. The MME has substantially progressed between early 2019 and mid-2020, as indicated by the increase of mortality at sites consecutively monitored multiple times. This work highlights the urgent need for continuous monitoring of surviving populations and calls for the immediate implementation of an effective protection and management strategy that will ensure the persistence of surviving individuals and the production of resistant offspring.
Zooplankton and hydrography of the upper 200 m was studied in coastal and pelagic waters off central Greece (eastern Mediterranean) during July 1998. The spatial distribution of the main environmental (temperature, salinity, fluorescence) and zooplankton (abundance, dry-weight, dominant groups) features of the area was delimited over an intense grid of 124 stations. The complex topography of the surveyed area comprised an interesting field for the study of pelagic–coastal interaction and its influence on the taxonomic composition of zooplankton.A typical summer thermal stratification was observed over the entire study area. Marked differences were found in surface-salinity between the eastern (Aegean Sea) and the western (Ionian Sea) part of the study area, which was attributed to the presence of less saline waters originating from the Black Sea. A deep fluorescence maximum was present in both coastal and pelagic stations. Zooplankton abundance and biomass showed an inshore–offshore gradient with coastal areas being significantly richer than pelagic areas. The taxonomic composition of zooplankton varied greatly both along the inshore–offshore gradient and among the different semi-enclosed Gulfs. Copepods were the dominant group in the pelagic waters comprising 67–78% in terms of mean relative abundance. In coastal areas, copepods were less important with cladocerans (especially the species Penilia avirostris) being the dominant group (44–51%). Appendicularians and chaetognaths comprised an important component of the zooplankton community over the entire surveyed area with mean relative abundance ranging from 2·5 to 14% and 0·6 to 5·8%, respectively.
Body size is the most easily measured universal characteristic and its relation with body weight has been extensively documented in fisheries research (Froese et al. 2011). The Length-weight (L-W) relation of a species depends on many factors (i.e. sex, size range, habitat, food availability, and fishing pressure), but may also vary seasonally (Froese 2006, Karachle and Stergiou 2008, Liousia et al. 2012. However, studies focusing on seasonal L-W relations are rather limited compared with those on annual estimates, because most of the estimates are based on samplings conducted during short-term periods in an annual basis.In Greek fisheries, L-W relations are mostly derived from sampling conducted in open sea (using trawls and purse seines; for reviews see: Stergiou and Moutopoulos 2001, Karachle and Stergiou 2008) than in coastal waters (smallscale fishery; Moutopoulos and Stergiou 2002), despite of the multi-gear nature of the fishery. Small-scale fishery is of great importance to the Greek fishery contributing 57.3% to the total Greek fisheries landings (Moutopoulos and Stergiou 2012). It involves approximately 30 000 fishers characterized by low income, elementary education and living in small and isolated islands (Tzanatos et al. 2005). Likewise, in the study area (Korinthiakos Gulf) the small-scale fishery component is highly contributing to providing approximately 74% of the total landings (Moutopoulos and Stergiou 2012).In the presently reported study, we calculated annual and seasonal estimates of L-W relations for the most abundant fish species caught by a professional small-scale ves-
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