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)
Introduction
The establishment of marine protected areas (MPA) is a management tool that has been implemented to enhance biodiversity and habitat conservation (Gell and Roberts, 2003). Moreover, MPAs have also been predicted to have a benefit on the adjacent fisheries through two main factors: the emigration of adults and juvenile individuals to zones where fishing is allowed (spillover effect, Rowley, 1994) and the exportation of pelagic eggs and larvae from the spawning stocks inside MPA (Gell and Roberts, 2003). In addition to the effects on the target species, the protection of an area from fishing can also reduce collateral effects of fishing, such as by catch, impact on benthic areas and therefore be a useful tool specially for multispecies fisheries (Hilborn et al., 2004). However, the establishment of a MPA does not guarantee by itself the accomplishment of these objectives: MPAs have to be carefully designed, monitored and evaluated (Hilborn, 2018; Hilborn et al., 2004; Sale et al., 2005). Edgar et al. (2014), after analyzing 87 MPAs worldwide, defined five key factors that determine the effectiveness of an MPA: the degree of fishing permitted, level of enforcement, MPA age, MPA size and presence of continuous habitat allowing fish movement across MPA boundaries.
While there is scientific evidence showing that the establishment of MPAs enhances habitat conservation and the biodiversity and biomass within its boundaries (Hilborn, 2018; Edgar et al., 2014), evidence regarding the effect of MPAs on fisheries yields remains scarce (Hilborn, 2018; Roberts et al., 2001; Sale et al., 2005). In the western Mediterranean, Harmelin-Vivien et al. (2008) demonstrated using underwater visual censuses in six MPA the existence of a negative fish biomass gradient from the MPAs to adjacent fished areas, which is consistent with the hypothesis of adult fish biomass spillover. The local concentration of fishing effort around MPAs borders, benefits for commercial fishing and tourism and implications for fisheries management have been mentioned in a number of studies (Goñi et al., 2008; Martín et al., 2012; Merino et al., 2009; Stelzenmüller et al., 2008).
The methodology for the analysis of MPA spillover is usually based on the observation of fish biomass gradients across MPA boundaries at a given time (Di Lorenzo et al., 2016; Francini-Filho and Moura, 2008). This is based on the idea that the increased fish size and population density inside a no-take area will cause fish emigration beyond the area boundaries, where fishing pressure will reduce the fish biomass (Stamoulis and Friedlander, 2013). Spillover analysis is usually based on discrete sampling methods such as underwater visual transects, tagging methods and experimental fish catches across MPA borders (Di Lorenzo et al., 2016). Other methodologies, such as catch and capture, have also been used with other commercial gears such as trammel nets (e.g., Johnson et al., 1999). Most studies are based on sampling carried out after protection, while comparisons of before and after the protection (before-after control impact (BACI) approach) remain scarce due to the lack of data before the protection measures (Di Lorenzo et al., 2016; Francini-Filho and Moura, 2008). However, the BACI approach, has been applied in the Mediterranean (Claudet et al., 2006; Fiorentino et al., 2008).
Vessel Monitoring System (VMS) data analysis can be used to study MPAs spillover effect by geo-referencing fishing catches or landings. Some studies have previously been carried out in this direction (Murawski et al., 2005). This methodology represents a marked difference with respect to the studies analyzing MPA spillover based on field sampling methods for two main reasons: before-after protection analysis can be done despite the lack of field sampling before the protection, and the large amount of spatiotemporally analyzed data. In the NW Mediterranean, VMS data have been used to characterize trawl fleet behaviour (e.g., Martín et al., 2014), but these data had not previously been applied to the evaluation of no-take zone performance.
Roses is an important fishing port on the Catalan coast both in terms of landings and income from the sale at the auction. Hake represented, in 2016, the primary species in the demersal landings (15.6 %; 15.6 tonnes) and the second in economic importance (14.2 %; 884 M €). It is mainly caught with otter trawl vessels (95 % of hake landings), although longlines and gillnets also target this species. Over the past 25 years, the hake landings along the Catalan Coast and in Roses harbour have decreased (Fig. 1). The population displays natural fluctuations regulated by the interaction between intrinsic biological factors and the environmental conditions, which can be observed to have occurred at the same time as hake landings markedly decreased over time (Fig. 1). In this context, the fishers Association of Roses initiated a protection plan for hake to reverse this trend. In 2013 (February to October) the fishers unilaterally decided to establish a no-take marine reserve in front of Roses port. The chosen area corresponded to a nursery ground for hake juveniles (Colloca et al., 2015; Druon et al., 2015; Tugores et al., 2019). Indeed, the areas of concentration of recently settled juveniles of hake, composed of age-0 individuals, are quite stable over time (Abella et al., 2005; Druon et al., 2015). Since February 2014, this area has remained permanently closed to any fishing activity, i.e., bottom trawling and small-scale fishing, including longlines and gillnets, under the surveillance of the same Roses Fishermen Association. The protected area, located in the continental shelf at 130−150 m depth, covers an extension of 51 km2. This zone used to be a fishing ground for bottom trawl, longline and gillnet, the fishing gears targeting hake.
Scientific collaboration started with the first study focusing on the effects of fishing closure carried out from March 2015 to March 2016 (Balcells et al., 2016; Recasens et al., 2016). Higher abundance, biomass and biodiversity of the benthic community was observed inside the protected area compared to an analogous (similar depth and seabed) area where the fishing activity continued normally (1.3) (Balcells et al., 2016). Interestingly, taking into account the short time period since the implementation of the protected zone, the effect was detected in both economically valuable species and benthic species that are not commercially exploited (Balcells et al., 2016; Recasens et al., 2016). In the case of hake, the abundance and biomass of recruits (10−20 cm TL) was doubled inside the protected zone (Recasens et al., 2016).
In the present study, we investigated the consequences for the Roses hake fishery of the establishment of the no-take area using VMS and landings data, that is, we analyzed whether the effect of the aforementioned observed increases in biomass, abundance and biodiversity within the no-take area boundaries effected the surrounding area (spillover effect), enhancing the hake fishery yield. As the methodology used represents a novelty in this kind of studies, analyzing its potential is in itself an objective of this work. Therefore, we have two main objectives: (1) explore the potential of VMS/GIS tools to analyze spillover effect and characterize hake populations in space and time and (2) analyze the effect of the establishment of a no-take zone on the Roses hake fishery.
Section snippets
Experimental design
Our experimental design was based on the definition of areas adjacent to the no-take zone (P, 130−150 m depth) similarly to other studies analysing spillover (Di Lorenzo et al., 2016). First, we included the areas that previous studies were based on (Balcells et al., 2016). Second, other zones (1.1, 1.2, 2.1, 2.2) were designed as close as possible to the protected one but also attempting to cover different bathymetric ranges of the hake distribution: the coastal shelf (1.1 and 1.2, 100−130 m
Roses hake fishery
For the 11 years period (2006–2016), hake landings in Roses port varied between 130 and 336 tons per year (Table 1). If we take into account longer time series (Fig. 1), it can be observed that the landings started to fluctuate in this range in approximately 1997. Previously, hake landings reached higher values of approximately 500 and 750 tons per year (Fig. 1). The hake landings trend along the entire Catalan coast (Roses excluded, Fig. 1) also showed a decrease that started later,
Hake spatial distribution
The spatial distribution of hake as presented in this study was consistent with the results of previous studies carried out in the same area (Demestre and Sánchez, 1998; Recasens et al., 1998). These studies showed that the hake bathymetric distribution ranged between 50 and 700 m depth approximately, with low biomass deeper than 400 m. Differences in the bathymetric distribution among size classes were also observed. Juveniles concentrated at depths shallower than 200 m, whereas adults had a
Conclusions
The analysis of VMS data combined with landings data provide a new methodology to study hake distribution and behaviour, assess no-take zone effectiveness in the sustainability of a hake fishery and analyse changes in fleet behaviour around a protected area. We provide some evidences of spillover effect on hake juveniles. Fishing vessel positioning data should be combined with field sampling inside MPAs to study the species recruitment behavior and time series data should be long enough to
CRediT authorship contribution statement
Joan Sala-Coromina: Conceptualization, Methodology, Data curation, Formal analysis, Visualization, Writing - original draft, Writing - review & editing. Jose Antonio García: Conceptualization, Methodology, Data curation, Formal analysis, Visualization, Writing - review & editing. Paloma Martín: Conceptualization, Methodology, Writing - review & editing. Ulla Fernandez-Arcaya: Writing - review & editing. Laura Recasens: Conceptualization, Methodology, Writing - review & editing.
Declaration of Competing Interest
The authors report no declarations of interest.
Acknowledgements
We acknowledge the Roses Fishers Association for the collaboration on the implementation of the management plan of the non-fishing area, as well as the Regional Government of Catalonia and the Spanish Fisheries Ministry for the access to landings and VMS data respectively. We acknowledge the constructive comments and suggestions of the reviewers that were very helpful for the improvement of the manuscript. We thank Joan Mir-Arguimbau for his guidance on data analysis. This study was supported
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2022, Fisheries ResearchCitation Excerpt :These data and capabilities are available in some Mediterranean areas, and some works have shown promising results on how to manage the European hake that could be adapted to a lack of strong stock structure (Colloca et al., 2015; Tserpes et al., 2008). Khoukh and Maynou (2018) and Sala-Coromina et al. (2021) showed with a realistic model and data of fishermen catch how the closure of a hake nursery area could improve the biology and economy of the fishery, within a Management Evaluation Strategy (MES) framework. As indicated above, some stock assessments and Management Plans comprise several GSAs.