Marinas and ports could offer suitable habitats for post-larval fish owing to their calm and food-rich waters. However, port infrastructures with their steep smooth sides and hard surfaces do not provide protection for the juvenile fish from predation meaning that most, if not all, the juvenile fish do not reach a size to survive in nearshore fisheries. Ecocean have addressed the problem of how to turn marinas and ports into safe havens for fish, and so enhance local fisheries, by creating artificial substrates, called ‘Biohut ’, which can be attached to docks, pontoons and seawalls to provide suitable habitats for the fish. Here, we describe the outcomes of tests of the ‘Biohut’ system in a Mediterranean marina and in the commercial Port of Marseille.
What is ‘Biohut’?
Biohut® consists of a patented double-caged framework that provides food and shelter to young fish, thus improving their survival rates in environments which have been modified radically by man and where natural substrates favoured by juvenile fish are no longer available.
Two research projects have validated the efficacy of the ‘Biohut ’ concept, one in a marina the Mediterranean Sea (NAPPEX project) and the other in the busy commercial port of Marseille (GIREL project).
Figure 1. A Biohut® just after it had been installed under a pontoon. Over time, the substrate inside (in this case empty oyster shells) will become covered in a rich community of attached flora and fauna, providing food for the young fish, while the external grids prevent larger predators from entering the habitat, thus creating a safe place for the young fish to grow.
NAPPEX project – the use of ‘Biohut’ in marinas
NAPPEX was created to answer a call from the French Ministry of Ecology for ecological engineering solutions to achieve “Good Environmental Status” targets set by the European Marine Strategy Framework Directive (MSFD). In March 2013, 192 Biohut® structures were installed along docks and under pontoons in six Mediterranean marinas. Scientists from the University of Perpignan monitored each location for two years, quantifying the number of juvenile fish, and of mobile and attached fauna. The NAPPEX survey provided scientific validation of the ability of Biohut' to restore the fish nursery function in marinas (Bouchoucha et al., 2016). A total of 56 different species of fish were observed using the ‘Biohut’ at juvenile stage. The surveys also showed that the abundance and diversity of fish larvae varied depending on the location of the marina and the positions of the ‘Biohut’ within the marina. Finally, the NAPPEX project highlighted the lack of knowledge about marina environments. Three theses are now in progress on the relevance of integrating ecological engineering into the design of port infrastructures.
GIREL project – the use of ‘Biohut’ in commercial ports
The GIREL project was conducted in one of the largest commercial ports in the Mediterranean Sea, the Grand Port Maritime of Marseille. 120 Biohut® were installed in 3 different areas of the port and monitored along with two control areas (docks and rocky breakwaters without Biohut® reef structures). The results were extremely positive (Mercader et al., 2017). The observations reported higher abundances of juvenile fish in the artificial nurseries compared to the control areas (on average x4 and up to x30 in the best areas). In terms of diversity, 26 different fish species were observed using the Biohut® . Subsequently the French Water Agency recognised the Biohut® system as an operational tool for enhancing fish nurseries and ecological restoration in coastal areas.
This project also raised additional questions relating to whether there is any chemical contamination of the fish within the artificial nurseries. Results presented recently by Bouchoucha et al. (2018) clearly show that fish (Sparidae) are not more polluted inside than outside these artificial nurseries.
The installation of this innovative solution is easily replicable on any built shoreline infrastructure. Convinced by the efficiency of the process, 17 port authorities in the Mediterranean coast have deployed the Biohut® artificial reefs already. The word NAPPEX has become closely identified with ports which are committed to sustain biodiversity within their waters by implementing artificial habitats for the protection of fish larvae and many other marine species.
The Biohut® concept is being deployed increasingly in other regions, such as the tropical waters of the French Caribbean, brackish environments of the east coast of the USA, lagoons of the southern Mediterranean (Morocco) and the colder waters of Northern Europe (Netherlands and Denmark). In all these places, the benefits Biohut® system on marine biodiversity have been seen.
Further information about Biohut® projects around the world as well as pictures and videos are available at www.nappex.fr. General information about the company Ecocean is available at www.ecocean.fr
For further information contact: Gilles Lecaillon - firstname.lastname@example.org
Bouchoucha et al., 2016. Potential use of marinas as nursery grounds by rocky fishes: insights from four Diplodus species in the Mediterranean. Marine Ecology Progress Series 547, 193–209.
Mercader et al., 2016. Observation of juvenile dusky groupers (Epinephelus marginatus) in artificial habitats of North-Western Mediterranean harbors. Marine Biodiversity. DOI 10.1007/s12526-016-0498-x
Mercader et al., 2017. Small artificial habitats to enhance the nursery function for juvenile fish in a large commercial port of the Mediterranean. Ecological Engineering 105, 78-86.
Bouchoucha et al., 2018. Growth, condition and metal concentration in juveniles of two Diplodus species in ports. Marine Pollution Bulletin 126, 31-42.