Spatio-temporal patterns of larval fish settlement in the northwestern Mediterranean Sea

Abstract

Most coastal fish species spend their early life stages in the pelagic environment, before settling in coastal habitats. The variability in the arrival of larvae to coastal habitats provides information on the species’ biology and recruitment potential. To explore the dynamics of larval fish supply to coastal habitats in the NW Mediterranean Sea, 13 sites were monitored using light-traps, from July 2012 to December 2015. Most variation in catches per unit effort (CPUE) among topographic basins and species were statistically significant for high (quantile 75%) and very high (quantile 90%) catches only. At the yearly scale, CPUE displayed strong seasonality, and 3 main species assemblages were detected in late spring-early summer, summer and late autumn-early winter. At the monthly scale, CPUE were higher around the new moon for all quantiles and temporally autocorrelated at a lag of ~28 d. Larval supply also varied spatially with site-specific associations and with riverine influence. Altogether, these results confirm that the previously described patterns of larval supply observed in tropical and subtropical environments (e.g. the high variability at all spatial and temporal scales and the strong influence of the moon) also apply to Mediterranean fish assemblages. Our quantile-based approach demonstrated that the larval supply in the NW Mediterranean Sea is a solid candidate for monitoring the state of the marine ecosystems, highlighting the need to continue such time series.

Ichthyoplankton assemblages and physical characteristics of two submarine canyons in the south central Tyrrhenian Sea

“…To date, we have no understanding of the spawning origins of fish that recruit in the southern‐central Tyrrheanian shelf. Further investigations using Lagrangian particle tracking inclusive of larval behavior can determine settlement areas and whether these canyons can act as potential source of recruits for fish populations of both protected and/or fished areas of the north shelf (e.g., Faillettaz et al, 2020; Falcini et al, 2020). Local artisanal fishermen utilize Cuma and Dohrn canyons as their primary fishing grounds and their anecdotal evidence highlight the importance of these areas for capturing mature females of demersal and pelagic species.…”

All shallow coastal habitats matter as nurseries for Mediterranean juvenile fish

“…Similarly, the same habitat can perform as a ‘good’ nursery at a given site but not in another location 64 . Thus, the success of fish nurseries does not depend only on the local characteristics of habitats but also on large scale environmental phenomena that determine the initial intensity and trajectory of the flux of fish larvae 80 , 110 .…”

“…1 ). A random sampling design was adopted to encompass the natural characteristics and spatial variability of shallow coastal habitats during the warm (June–July 2014) and cold (April 2015) period (Table 1 ), as fish settlement shows wide seasonal variation 26 , 31 , 80 . During our study, mean seasonal sea surface temperature ranged from approximately 14 °C (cold period) to 22 °C (warm period).…”

Typology of fish nurseries in shallow Mediterranean coastal zones: all habitats matter

“…1). A random sampling design was adopted to encompass the natural characteristics and spatial variability of shallow coastal habitats during the warm (June-July 2014) and cold (April 2015) seasons (Table 1), as fish settlement shows wide seasonal variation 26,42,71 . A total of 2 101 UVC samples were undertaken.…”

“…Similarly, the same habitat can perform as a 'good' nursery at a given site but not in another location 104 . Thus, the success of fish nurseries does not depend only on the local characteristics of habitats but also on large scale environmental phenomena that determine the initial intensity and trajectory of the flux of fish larvae 71,105 .…”