1. How maintain marine fish population in a context of high anthropic pressure: role of shallow coastal zones
Pr. Philippe LENFANT1,2; Dr. Jérémy PASTOR1,2; Dr. Adrien CHEMINEE1,2.
1 University of Perpignan Via Domitia, CEntre de Formation et de Recherche sur les Environnements Méditerranéens, UMR 5110 CNRS/UPVD, 58 Avenue Paul Alduy, F Perpignan, France
2 CREM, Centre de Recherche sur les Ecosystèmes Marins, Technological plateform, F PORT-BARCARES, France
My main topic concern the fish population dynamic. We study since 20 years recruitent process of the white seabream. In paralell we work on reserve effect and the role of MPA in the maintain of marine biodiversity.
In the context of no take zone can not be create in Mediterranean sea regarding the high level of anthropic activities, we have focused recently on ecological restoration to complete the conservation action link to MPA.
I propose you to present you the specific context of coastal shallow water and I will make a focus on fish recruitment process which could be integrate in ecological restoration action

2. High biodiversity  Species / Habitat
Shallow coastal zone
River
Estuary
Lagoon
Sandy
coast
Posidonia
meadow
The interest of coastal shallow water is synthetise by this slide where we can see the concentration of human activities, especillay some activities linked to the transport infrastructure. But in this coastal zone, it is also the place of a high diversity of habitat and species with just some example like estuary, rocky coast or posidonie meadow, a species protected by the french law.
Rocky
coast
High biodiversity  Species / Habitat

3. Halieutic stocks: pelagic fishes, seabass…
Shallow coastal zone
Associated with habitat, we found a high diversity of species which can be exploited by professional and recreational fishermen.
Halieutic stocks: pelagic fishes, seabass…

4. Ecological functions and services
Shallow coastal zone
Regulating
Climate, Water purification…
Provisioning
Food, Fresh water…
Regarding the association of habitat, species, ecological functions, intesrest for human, we consider that coastal shallow water has a main role in ecosystem services : as we have shown before it concerns the provisioning of food or water, the regulation of climate and induce a cultural interest for human
Cultural
Recreation, Ecotourism…
Ecological functions and services

5. Pollution, overfishing, artificial coastline
Shallow coastal zone
But the high concentration of human activities generate pressures for marine biodiversity. Three pressures have a main role in lost biodiversity : polution, overfishing, and artificialisation. I will focus on this last pressure to better understand consequences of lost habitat on fish population. For that it is important to better know the life cycle.
Pollution, overfishing, artificial coastline

6. High natural mortality
Fish life cycle
Mortality larval
stage: >95%
10 to
100 days
Mortality
settlement:
~90%
The benthic phase when individuals are juvenile and adult is a long phase, sometimes more than 50 y. Comparatively with the pelagic larval stage with a maximum of 100 days. Even this phase is short, this phase is critical for the species. During this period, more than 95% of individuals die by predation, starvation. This natural mortality is induce by the lack of parentage protection
2 to
>50 years
High natural mortality
 no parental
protection

7. Coastal habitat losses  endangered fish life cycle
We have evaluated that for 1 Million eggs produced, only one individuals will be able to survive. As I mention before, the pelagic stage is critical but the settlement zone in the shallow water stay also critical. Individuals become juvenile and have to change their habitat preference with more complexity to be protected against predators.
In cas of habitats losses, news settlers can be eliminated rapidly. It means that recruitment process is cancelled
Coastal habitat losses  endangered fish life cycle

8. Essential Fish Habitat: Nursery
Following species, habitat recruitment can be different at the same season. But if several species recruit in the same place, they differ by the season to limit competition for food and space
Multi-species nursery...
to limit competition
Beck et al., 2001

9. Essential Fish Habitat: Nursery
Method : Underwater Visual Census
Before starting restoration action, it was important to have more information about intensity of recruitment in abunance. After a survey of 20 y,
 2 high cohorts in 20 y: no maximization of marine ecosystem
 Carrying capacity > 5000 individuals  reference for ecological restoration program
(Lenfant et al., in prep.)

10. Ecological restoration solutions
PhD Marc Bouchoucha
- Richness / abundance / growth in artificial habitat (Biohut)
- Pollution impact
PhD Manon Mercader
- Ecological gain in full equiped harbor (BACI)
- Mortality test in aquarium
Harbor / Marina: places to restore nursery function

11. Ecological restoration solutions
Grouper juvenile – Total length 6 cm
Mercader et al., 2016
Bouchoucha et al., 2016
Lenfant et al., submitted
Mercader et al., in prep.
Thank you