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Invasive aquatic macrophytes tend to reproduce and spread through vegetative means, often via fragmentary propagules. Dispersal among aquatic sites may occur overland via attachment to various vectors, or within river systems by directional water currents. However, for many species the relationship between fragment size and resumption of growth is unknown. Here, we assessed resumption of growth of apical and mid-stem fragments of invasive Crassula helmsii, Elodea canadensis and Lagarosiphon major. Proportionally, apical fragments tended to more readily resume growth than mid-stem sections, especially for E. canadensis and L. major (80–100%). However, viability did not scale linearly with increasing fragment size, which suggests that fragment size is not a singular determinant of propagule fitness. Nevertheless, longer fragments generally produced greater numbers of shoots and roots, but root production significantly differed among species and was determined through an interaction between plant section, species and fragment length. Overall, all species produced new shoots and roots from fragments as small as 10 mm. C. helmsii mid-stem fragments standardised by node counts did not display new growth (up to 10 nodes), while E. canadensis tended to show greater shoot and root production with increasing node counts. It is evident that a medium to high proportion of small fragmentary propagules of these invasive macrophytes can retain viability. These data have clear implications for understanding the dispersal of these invasive species and their management. Specifically, cutting and dredging may increase rather than decrease infestations, especially in downstream directions. Thus, in the absence of adequate fragment containment, current short-term control strategies may in fact be counterproductive.

The Joint EIFAAC/ICES/GFCM Working group on eels (WGEEL) met from September 6–9 and 12–20 September 2022 in Toombridge, Northern Ireland, to provide the scientific basis for the ICES advice on fishing opportunities and conservation aspects for the European eel and address requests from EIFAAC and GFCM. WGEEL assessed the state of the European eel and its fisheries, collated and analysed biometric data, reviewed and summarized available data on eel quality, further identified issues specific to the Mediterranean region, discussed the use of landings data for the assessment (following WKFEA) and reported on any updates to the scientific basis of the advice, new and emerging threats or opportunities. The recruitment of European eel declined markedly from 1980 to 2011. The glass eel recruitment compared to that in 1960–1979 in the “North Sea” index area was 0.5% in 2022 (provisional) and 0.6 % in 2021 (final). In the “Elsewhere Europe” index series it was 9.7 % in 2022 (provisional) and 5.5% in 2021 (final), based on available data series. For the yellow eel data series, recruitment for 2021 was 19% (final) of the 1960–1979 level; the 2022 data collection for yellow eel is ongoing. Time-series from 1980 to 2022 show that glass eel recruitment remains at a very low level. Analyses of data series on yellow or silver eel abundance (162 series analysed) and grouped biometric data were re-run this year and show the potential of the yellow and silver eels’ series to improve the stock assessment. A graphical analysis of the new biometric data integrated in the database, 1.2 million individual data and 4908 grouped data (combining length, weight and age data), was carried out to identify future analyses and information that might be missing. To identify the potential of Length-Based Models for stock assessment, a preliminary overview of the models, the input needed and of the assumptions was realised. A collation and integration of available