  Conservation measures are implemented to support biodiversity in areas that
are degraded or under anthropogenic pressure. Over the past decade, numerous
projects aimed at rehabilitating a fish nursery function in ports, through the
installation of artificial structures, have emerged. While studies conducted on
these solutions seem promising on a very local scale (e.g., higher densities of
juvenile fish on artificial fish nurseries compared to bare port
infrastructures), no evaluation has been undertaken yet to establish their
contribution to the renewal of coastal fish populations or their performance
compared to other conservation measures such as fishing regulation. Here, we
used a coupled model of fish population dynamics and fisheries management,
ISIS-fish, to describe the coastal commercial fish population, the white
seabream (Diplodus sargus) in the highly artificialized Bay of Toulon. Using
ISIS-Fish, we simulated rehabilitation and fisheries management scenarios. We
provided the first quantitative assessment of the implementation of artificial
structures in ports covering 10% and 100% of the available port area and
compared, at population level and fishing fleets level, the quantitative
consequences of these rehabilitation measures with fishing control measures
leading to strict compliance with minimum catch sizes. The rehabilitation of
the nursery function in ports demonstrated a potential to enhance the renewal
of fish populations and catches. When the size of projects is small the
outcomes they provide remain relatively modest in contrast to the impact of
regulatory fishing measures. However, we have demonstrated that combining
fishing reduction measures and rehabilitation projects has a synergistic effect
on fish populations, resulting in increased populations and catches. This study
is the first quantitative assessment of fish nursery rehabilitation projects in
port areas, by evaluating their effectiveness in renewing coastal fish
populations and fisheries and comparing their outcomes with fishing control
measures. Small-scale port-area nursery rehabilitation projects can support
fish populations, but are less effective than controlling fisheries.
