Distribution of non-native Pacific oyster Magallana gigas (Thunberg, 1793) along the eastern Adriatic coast

Non-native Pacific oyster Magallana gigas (Thunberg, 1793) was introduced to the Mediterranean Sea for aquaculture purposes in the 1960s. Although this species was not introduced for aquaculture to the Croatian part of the Adriatic Sea, in the 1970s, it was reported in the Lim Bay, in the North-eastern Adriatic. Until recently, there has been no research on the species in the Croatian part of the Adriatic. The aim of this research was to summarize existing and novel data on the distribution of M. gigas in coastal areas of the Eastern Adriatic and to provide a baseline for the future monitoring and assessment programmes of the species. Distribution of M. gigas was determined by three different methods: (i) a visual census of the presence of M. gigas specimens in the medio-littoral zone ; (ii) DNA identification of M. gigas larvae in the water column ; and (iii) the presence of M. gigas in the subtidal zone at depth between 25 and 40 m. Magallana gigas has a well- established population in the medio-littoral zone of natural and anthropogenic habitats along the coast of the North-eastern Adriatic Sea (west coast of Istria peninsula), but it is not present in the deeper layers . In the Central-eastern and South-eastern Adriatic Sea, the species was either absent or sporadically recorded with no evidence of fully established populations. Considering the great invasion success of M. gigas worldwide and effects that this species could have on the invaded ecosystem (e.g. competition for food and space with native species), detailed future monitoring is needed for the Eastern Adriatic Sea

Workshop to scope and preselect indicators for criterion D3C3 under MSFD decision (EU) 2017/848 (WKD3C3SCOPE)

The workshop to scope and preselect indicators for Descriptor 3 criterion 3 under MSFD Commission Decision (EU) 2017/848 (WKD3C3SCOPE) provided a platform for experts from the EU member states and relevant regional bodies to meet and support development and progress the assessment methodology, based on a request by the EC (DGENV). WKD3C3SCOPE is the first of a series of three workshops (WKD3C3THRESHOLDS and WKSIMULD3) to provide guidance in relation to operational indicators for MSFD D3C3. The workshop was organized as a series of presentations with intermittent group discussions. On the first day of the workshop the participants discussed what defines a ‘healthy population structure’ for species with different life history traits (ToR a). During the following days, the group discussed and identified relevant D3C3 indicators (ToR b) and developed criteria to select among the identified D3C3 indicators to allow further testing and setting of thresholds at WKD3C3THRESHOLDS (ToR c). The participants found that overall, healthy fish stocks are characterized by high productivity, wide age and size structuring in the population, and the ability to quickly recover from disturbances. The groups noted that environmental factors, along with stock biomass and fishing pressure, influence the productivity and health of a stock, with environment playing a particularly large role in the recruitment of short-lived stocks. It was suggested that the age structure of a stock might be more relevant for evaluating the health of long-lived stocks. However, it was acknowledged that not all stocks have sufficient data to evaluate all proposed indicators, and a single indicator is unlikely to suffice for all stocks. Data availability, species- specific factors and regional or sub-regional variation are thus also important considerations. In relation to ToR b, the participants presented their work on potential indicators including: recruitment time-series, proportion of fish larger than the mean size of first sexual maturation, F rec/Fbar, length distribution L 90, relative proportion of old fish above A 90, indicators of spawner quality, and SSB/R. A discussion on pros/cons, benefits to the population of high or low indicator values, benefits supported by empirical evidence, applicability to data-poor stocks and benefits supported by simulation/theoretical considerations followed the presentations. Finally, in relation to ToR c, the difficulty emerged in ranking the indicators alone without considering the data used to estimate them and a new set of evaluation criteria for use in WKD3C3THRESHOLDS were defined. Based on the outputs of the meeting a list of indicators to be further evaluated has been drafted, which also emphasizes the stocks for which studies have empirically demonstrated effects on productivity. In addition to the listed indicators, indicators of genetic diversity and proportion of fish with parasite infestation were mentioned but to the knowledge of the participants, widespread data for these are currently not publicly available.info:eu-repo/semantics/publishedVersio

Glycymeris bimaculata (Poli, 1795) - A new sclerochronological archive

Glycymeris bimaculata is one of the largest (up to ~115mm) bivalves in the Mediterranean Sea, yet there is a paucity of information about the biology, ecology and growth of the species. Maximum longevity, growth and periodicity of internal shell growth line formation were assessed in individuals collected from Pag Bay in the Adriatic Sea. We validated annual periodicity of line formation using stable isotope analysis of shell calcium carbonate to construct standardized growth indices (SGIs) in live collected specimens obtained in 2008 and 2012 and develop a statistically robust master chronology from the growth increment series to explore shell growth responses to environmental indices. The estimated age of 55 shells (shell length 49.1 to 109.5 mm) ranged from 6 to 57 years and shell growth is described by the von Bertalanffy growth equation: Lt = 90.85 – (e-0.10 (t+3.13)). The dark growth lines visible in acetate peel replicates of polished and etched shell cross-sections were deposited annually at the beginning of spring. Growth increment data for the period between 1991 and 2007, derived from 9 individuals (age between 17 and 34 years), were used in the construction. The SGIs had pronounced inter-annual variability with the period between 1997 and 1999 characterized by slower growth, the period between 2000 and 2005 by moderate growth, whilst the widest growth increments were deposited in 2006 and 2007. Differences in growth between these periods were related to differences in surface seawater temperatures and salinity