The Spanish blackspot seabream (Pagellus bogaraveo) fishery in the Strait of Gibraltar: spatial distribution and fishing effort derived from a small-scale GPRS/GSM based fisheries vessel monitoring system

Abstract

-This paper aims to investigate the potential interest of using a Vessel Monitoring System (VMS) based on GPRS/GSM (Global System for Mobile Communications) technology to obtain a better estimation of fishing activity and distribution of a small-scale artisanal fleet, for which the European satellite-based system is not available. Since the early 1980s, the artisanal fishery targeting blackspot seabream (Pagellus bogaraveo), commonly known as "voraz", has been developing along the Strait of Gibraltar area. Up to now the fishing effort was estimated using the number of sales, a proxy for the number of fishing days. This measure does not, however, capture the "missing effort", i.e., fishing days resulting in no catch or not enough catch to be sold at public auction. The European satellite-based VMS provides information about the dynamics of different fishing fleets, but is not installed on small vessels (<15 m), such as those used by the artisanal "voracera" fleet targeting blackspot seabream in the Strait of Gibraltar. The Andalucía Regional Government installed its own vessel monitoring system on several artisanal fleets using GPRS/GSM cellular network technology that sends data on vessel positions and speed every three minutes. Data collected from 2009 to 2011 using this system were filtered and analysed to estimate fishing effort, catch rates and the spatial distribution of the blackspot seabream fishery. The estimates obtained seem to provide a good representation of fishery reality. As expected, the missing effort increases as the resource levels decrease. Additionally, expert knowledge of the fishery allowed application of an algorithm for splitting these daily trips into estimated fishing hauls. Afterwards the spatial distribution of catches and Catch per Unit Effort (CPUE) could be obtained linking VMS locations with landings information. This study provides a considerably finer spatial scale view of the fishery than data available in the past.

Using mobile device’s sensors to identify fishing activity

“…The variable GpsV m reflected, in each haul phase, velocity values similar to those found in other studies for trawl fishing [15,17,25], with medians of 8.4 knots shipping, 4.5 knots setting, 3 knots towing and 2.1 knots hauling. Furthermore, the expected variability of the speed is reflected in its interquartile ranges of 5.7 knots shipping, 1.2 knots setting, 0.16 knots towing and 1.4 knots hauling.…”

Is it possible to differentiate between environmental and fishery effects on abundance‐biomass variation? A case study of blackspot seabream (Pagellus bogaraveo) in the Strait of Gibraltar

“…The present study was carried out with blackspot seabream ( Paguellus bogaraveo ) caught in the Strait of Gibraltar. The catch area was the operational area of the voracera fleet (approximately a sector between 6°25′W to 5°15′W and 35°45′N to 36°15′N), which is in the extreme southeast of ICES Subarea IXa (Burgos et al ., ) (Fig. ).…”

Improving the interpretability of the effects of environmental factors on abundance of fish stocks

“…This study was based on catches of Blackspot seabream to the south of the Iberian Peninsula from the Strait of Gibraltar to Cape St. Vincent, ICES Division IXa in the area bound by the coordinates: 5°85′ W to 5°31′ W and 35°77′ N to 36°18′ N ( Burgos et al, 2013). The historical time series of monthly landings of Blackspot seabream correspond to landings from the Spanish ports of Tarifa, Algeciras, Conil, and Ceuta and the Moroccan port of Tangier between 1983 and 2016.…”