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The human-mediated introduction of marine non-indigenous species is a centuries- if not millennia-old phenomenon, but was only recently acknowledged as a potent driver of change in the sea. We provide a synopsis of key historical milestones for marine bioinvasions, including timelines of (a) discovery and understanding of the invasion process, focusing on transfer mechanisms and outcomes, (b) methodologies used for detection and monitoring, (c) approaches to ecological impacts research, and (d) management and policy responses. Early (until the mid-1900s) marine bioinvasions were given little attention, and in a number of cases actively and routinely facilitated. Beginning in the second half of the 20th century, several conspicuous non-indigenous species outbreaks with strong environmental, economic, and public health impacts raised widespread concerns and initiated shifts in public and scientific perceptions. These high-profile invasions led to policy documents and strategies to reduce the introduction and spread of non-indigenous species, although with significant time lags and limited success and focused on only a subset of transfer mechanisms. Integrated, multi-vector management within an ecosystem-based marine management context is urgently needed to address the complex interactions of natural and human pressures that drive invasions in marine ecosystems.

SUMMARY: Ecological properties and distribution and abundance of medusae were studied over an 18-month period in the Mljet Island seawater lakes, south-east Croatia. Strong stratification during the summer differentiates these lakes from the oligotrophic South Adriatic ecosystem. The lakes are designated as a moderately eutrophicated ecosystem. Very small numbers of hydromedusae were noted, representing only the Anthomedusae and Leptomedusae. A new species of the genus Tima was found in considerable numbers of individuals. High abundance of the scyphomedusa Aurelia sp. was observed throughout the year. This species differs in terms of genetic divergence from Aurelia aurita found elsewhere in the Mediterranean and could be attributed to the boreal origin.

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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.

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Integrating mussel and ¢n¢sh aquaculture has been recognized as a way to increase pro¢ts and decrease environmental impacts of ¢n¢sh aquaculture, but not enough is known about the e¡ects of ¢n¢sh aquaculture on mussel growth. Here we present a pilot study aimed at determining how distance from ¢n-¢sh aquaculture a¡ects mussel growth. To this end, we measured growth and condition index of mussel (Mytilus galloprovincialis) at three di¡erent distances (0, 60 and 700 m) from ¢n¢sh aquaculture in the eastern Adriatic Sea. There was a statistically signi-¢cant di¡erence in growth of tagged mussels with respect to site. Average measured lengths of mussels at sites 1, 2 and 3 after the 10 months of the experiment were 57.60, 62.73 and 58.66 mm. Mussels grew fastest from March to May, and slowest from July to September, regardless of their position. Condition index showed spatial and temporal variations with higher values during fall and winter ( $ 23), and lower values during spring and summer ( $ 20). Our results show that production cycle in areas traditionally considered suboptimal for aquaculture can be equivalent to the cycle in areas traditionally considered optimal for mussel aquaculture if mussel aquaculture is integrated with ¢n¢sh aquaculture.