Age-Dependent Habitat Identification of Mediterranean Swordfish: Application on Commercial Fishery Data and Potential Use in Fisheries Management

<div><p>Based on fisheries data from the 1990s and 2000s in the eastern Mediterranean Sea, generalized additive models were applied to investigate the relative influence of environmental factors on swordfish catch rates. (1) Young-of-the-year swordfish and (2) the remaining “adult” swordfish were modeled separately. Results suggested that the two stock components differentiated significantly: adults were more abundant to the south-east (Levantine basin), at the open seas, showing a clear relationship to cooler water masses. In contrast, juveniles were more frequently observed to the north-west (Ionian Sea), close to the coast, in warmer waters. Seasonally, juvenile swordfish were more abundant during the start and end of the fishing period, and during years of elevated water temperature. Lunar disc illumination affected positively all year classes; maximum catches observed around full-moon. The proportion of large swordfish decreased significantly throughout the study period, indicating a change in size-structure of the population or availability to the fishing gear. There were strong indications that the Ionian and Levantine may actually constitute favorable spawning grounds. Based on the models suggested associations, an indirect identification of the swordfish potential habitats was obtained. It was further considered how size-dependent habitat delineation could form the basis for a more realistic management approach, through the introduction of spatio-temporal closures of fishing activities.</p></div

Results of the PERMANOVA Analyses.

<p>Permutational multivariate analyses of variance based on the Euclidean dissimilarity measure for presence-absence data. The tests were done using 9999 permutations under the reduced model.</p><p>Results of the PERMANOVA Analyses.</p

The set of candidate models.

<p>GSA = Geographical Sub-Areas</p><p>s() is a smooth function represented using penalized regression splines [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0119330#pone.0119330.ref025" target="_blank">25</a>].</p><p>Covariate “Fisherman” was estimated through penalized random effects (bs = “re”).</p><p>The set of candidate models.</p

Generalized additive mixed model (GAMM) derived effects of engine power (kW), fishing depth, Period, and Country on the catch rates reported by fishers.

<p>Gray shaded area and dashed lines of upper and lower brackets indicate 2 standard errors above and below the estimates shown in solid lines. The relative density of data points is shown by the ‘rug’ on the x-axis.</p

Median overall engine power (in kW) and fishing depth (in meters) of the vessels used by the fishermen interviewed over time.

<p>Upper and lower whiskers indicate 25–75% percentiles around the median.</p

Non-metric Multi Dimensional Scaling (nMDS) ordination comparing species abundance trends responses outputs across the different locations (Country).

<p>The position of each dot is defined by the assemblage of species recorded in each interview.</p

Map showing the ports where the interviews with the fishermen were carried out.

<p>SPAIN (GSA 6): 1: Port de la Selva; 2: Roses; 3: Palamos; 4: Blanes; 5: Arenys de Mar; 6: Mataro; 7: Barcelona; 8: Vilanova i la Geltrù; 9: Tarragona; 10: Cambrils; 11: L’Ametlla de Mar; 12: San Carles de la Rapita; ITALY (GSA 9 & 17): 13: Viareggio; 14: Livorno; 15: Elba Island; 16: Castiglione della Pescaia; 17: Porto Santo Stefano; 18: Porto Ercole; 19: Civitavecchia; 20: Fiumicino; 21: Ponza Island; 22: Civitanova Marche; GREECE (GSA 20 & 22) 23: Nea Michaniona; 24: Chalkis; 25: Peireas; 26: Patra. Country maps source: ©OpenStreetMap contributors. <a href="http://www.openstreetmap.org/copyright" target="_blank">http://www.openstreetmap.org/copyright</a></p

SEAwise Report on review guidelines

This deliverable report provides the framework, guidelines, and specific instructions for systematic reviews to be undertaken with SEAwise. The report also includes pre-registered review protocols for five key systematic reviews focussing on the social effects of and on fishing, ecological effects on fisheries yield, ecological effects of fisheries, spatial management impacts, and evaluation of management strategies. The results of these reviews are reported in subsequent x.1 deliverable reports and will provide a synthesis of foundational knowledge for each of SEAwise’s work packages two-through-six, respectively.  This report contains a brief overview of the motivation for undertaking a series of systematic reviews and the selected framework that is being employed for all reviews across the project. Furthermore, this report provides detailed instructions for carrying out each step of a systematic review which can be applied to both the key SEAwise reviews, but also any other review either within or outside of this project. This includes, descriptions of how important databases function, R-scripts for processing records from databases and approaches to data-management for large collaborative reviews.  Additionally, this report serves as the repository for the search protocols for five reviews. These protocols ensure transparent methods and reduced bias in the searching, screening and data extraction.  The success of the coordination across five large-scale systematic reviews is illustrated in the coherence of the approaches and detailed methods described in this report. This report describes results of the SEAwise project. More information about the project can be found at https://seawiseproject.org/</p