Assessing Fishing and Marine Biodiversity Changes Using Fishers' Perceptions: The Spanish Mediterranean and Gulf of Cadiz Case Study

Abstract

BackgroundThe expansion of fishing activities has intensively transformed marine ecosystems worldwide. However, available time series do not frequently cover historical periods.MethodologyFishers' perceptions were used to complement data and characterise changes in fishing activity and exploited ecosystems in the Spanish Mediterranean Sea and Gulf of Cadiz. Fishers' interviews were conducted in 27 fishing harbours of the area, and included 64 fishers from ages between 20 to >70 years old to capture the experiences and memories of various generations. Results are discussed in comparison with available independent information using stock assessments and international convention lists.Principal FindingsAccording to fishers, fishing activity substantially evolved in the area with time, expanding towards deeper grounds and towards areas more distant from the coast. The maximum amount of catch ever caught and the weight of the largest species ever captured inversely declined with time. Fishers (70%) cited specific fishing grounds where depletion occurred. They documented ecological changes of marine biodiversity during the last half of the century: 94% reported the decline of commercially important fish and invertebrates and 61% listed species that could have been extirpated, with frequent mentions to cartilaginous fish. Declines and extirpations were in line with available quantitative evaluations from stock assessments and international conventions, and were likely linked to fishing impacts. Conversely, half of interviewed fishers claimed that several species had proliferated, such as cephalopods, jellyfish, and small-sized fish. These changes were likely related to trophic cascades due to fishing and due to climate change effects. The species composition of depletions, local extinctions and proliferations showed differences by region suggesting that regional dynamics are important when analysing biodiversity changes.Conclusions/SignificanceUsing fishers' perceptions, fishing and ecological changes in the study area were documented. The recovery of local ecological knowledge provides valuable information complementing quantitative monitoring and evaluation surveys.

The relative roles of the environment, human activities and spatial factors in the spatial distribution of marine biodiversity in the Western Mediterranean Sea

“…However, the pure effect of spatial variables on biodiversity metrics of most marine groups was small in deviance partitioning analyses, suggesting that a large fraction of their influence was related to the spatial structure of environmental and human variables considered. Although not conclusive, the remaining portion of their influence might reflect the role played by environmental or human variables not considered in the present study or past events (Legendre and Legendre, 1998), such as uneven historic human pressures, for example fishing activity in the coastal areas of the Mediterranean Sea (Azzurro et al, 2011;Coll et al, 2014).…”

Trophic level-based indicators to track fishing impacts across marine ecosystems

“…spiny dogfish in the Western Scotian Shelf; Araújo & Bundy 2012), or the expansion of fisheries to deeper areas. The latter may be the case in the Mediterranean ecosystems (Coll et al 2014).…”

“…divergence of TL-related descriptors at high trophic levels; Van der Lingen & Miller 2011) although they also may be well correlated (e.g. Coll et al 2014). These discrepancies or similarities in TL estimations warrant further examination and refinement of both isotope studies (e.g.…”

Infection of the lesser spotted dogfish with Proleptus obtusus Dujardin, 1845 (Nematoda: Spirurida) reflects ontogenetic feeding behaviour and seasonal differences in prey availability

“…The species is very popular for human consumption in the Mediterranean Sea (Capapé et al 2008), and it is a common fisheries by-catch in the eastern North Atlantic being the main shark species captured in northern Spain and northern France (Cavanagh 2005). Although populations have generally either remained stable or even increased over the last few decades (Jukic-Peladic et al 2001; UNEP-MAP-RAC/SPA 2013; Coll et al 2014;McHugh et al 2011), declines in lesser spotted dogfish landings have been reported for the Aegean Sea (Damalas and Vasilopolou, 2011), the Adriatic Sea (Barrausse et al, 2014) and the Tyrrhenian Sea (Ferretti et al 2005).…”