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Marine reserves contribute to the recovery of species exposed to overfishing

A study by the Institute of Marine Sciences (ICM-CSIC) shows that areas where fishing is prohibited are contributing to the recovery, in just a few years, of species such as hake, one of the most commercially interesting in the Mediterranean. According to the study, the effect of the reserve especially favours juvenile individuals, but it also contributes to an increase in their catches around the area where fishing is not allowed.

Juveniles are the ones that benefit the most from the effect of the reserves / ICM-CSIC.A group of researchers from the Institut de Ciències del Mar (ICM-CSIC) has found that marine reserves are contributing to the recovery of European hake (Merluccius merluccius) in the Mediterranean, where this is one of the most consumed and commercially valuable species. In fact, it is considered overfished in some parts of the westernmost part of this basin, where some closed areas have been established precisely for this reason.

According to the study, recently published in the journal Fisheries Research, around areas of the reserve where hake cannot be fished, the number of juvenile catches tends to increase, indicating that what is technically known as the "spillover" effect is taking place, i.e. there is an export of fish outside the reserve due to an increase in fish within the reserve. In this case, this is especially true for juvenile fish, although adult fish, although also increasing around the reserve, do so to a lesser extent.

"The results of the study are consistent with those of other studies that show that the spillover effect of a fishing reserve can increase the catches of commercial species around the reserve by up to 20%, thus promoting the sustainability of the species and the fishery," says the ICM-CSIC researcher Laura Recasens.

One of the research's fishing boats.Study carried out in Roses

To carry out the study, researchers combined data from vessel monitoring systems (VMS), which are carried by all fishing boats over 12 meters in length and collect daily information on the geographical location of the fishing effort, with data on daily hake catches from trawlers in the port of Roses. Thanks to this, they were able to assess the effect of fish stocks without having to sample within the protected area and thus without disturbing the habitat under restoration.

To do this, they compared catch and VMS data collected before the establishment of the reserve with data collected three years after the establishment of the reserve around it. This allowed the researchers to prove that marine reserves contribute to the recovery even of communities heavily exposed to the impact of fishing.

According to the researchers, this methodology can be repeated year after year to see the effect of the reserves on this and other species. It can also be used to identify changes in the demography of the species under study as a result of the fishing ban, which is useful to see if fisheries shift the focus from juveniles -as happens in many Mediterranean fisheries- to individuals closer to the adult stage.

Marine reserves are now known to play an important role as laboratories for further conservation measures and are key to raising public awareness of the need to protect our seas and oceans. However, few studies like this one in deep shelf and slope areas have proven that they are truly effective, either by increasing the resilience of communities to impacts from, for example, fishing activity or climate change, or by accelerating their recovery.

Knowing the spatial distribution, trophic ecology and how species of great commercial interest interact with the environment is key to ensuring the sustainability of stocks. The ICM-CSIC is particularly committed to this cause and contributes to it through the work done by researchers in the Department of Renewable Marine Resources.

In this sense, a group of researchers from this same department published another article at the end of 2020 that is relevant for fisheries management on a hake distribution model that combines environmental and biotic factors and takes into account seasonal changes for the prediction of the individuals’ distribution.

Reference Article

Sala-Coromina, J., García, J. A., Martín, P., Fernandez-Arcaya, U., & Recasens, L. European hake (Merluccius merluccius, Linnaeus 1758) spillover analysis using VMS and landings data in a no-take zone in the northern Catalan coast (NW Mediterranean)Fisheries Research237, 105870.

Elena Martínez | Communication and dissemination office ICM-CSIC