ReviewAn overview of fisheries discards in the Azores
Introduction
Sustainable fisheries management requires the accurate knowledge of present levels of fishing mortality (Pauly, 2009; Pitcher et al., 2002). Nevertheless, stock assessment and fisheries management have traditionally been based on the reported catch (i.e. reported landings), even though it has been demonstrated not to reflect total fishing mortality (Broadhurst et al., 2006; Pauly and Zeller, 2016; Zeller and Pauly, 2005). One of the main reasons for this discrepancy is that a significant portion of fishing mortality lie within discards (Alverson et al., 1994; Broadhurst et al., 2006; Kelleher, 2005; Zeller et al., 2017), i.e. the catch portion returned to the sea for whatever reason, either dead or alive (FAO, 1996). Discards are rarely reported in official statistics.
Discarding results from a complex set of decisions taken by fishers while sorting the catch (Eliasen et al., 2014; Rochet and Trenkel, 2005); however market incentives and regulatory constraints are often the preponderant drivers (Arnason, 1994; Catchpole et al., 2014; Feekings et al., 2012). The discard composition is usually more diverse than the landing composition, both in species and sizes (Viana et al., 2013). Thus, accounting for the total catch (discards plus landings) is more accurate than only accounting for landings when quantifying fishing pressure and characterizing its distribution across the ecosystem components (Fauconnet et al., 2015; Viana et al., 2013). Including discard estimates has also been shown to increase the accuracy and applicability of stock assessment models (Dickey-Collas et al., 2007; Punt et al., 2006). Quantifying discards is therefore a necessary step for more realistic and relevant management of fisheries, especially within an Ecosystem Based Management (EBM) context (Bellido et al., 2011; Hall et al., 2000; Viana et al., 2013).
An increased focus has been given to estimate discards in fisheries after the initial efforts in the 1980′s (e.g. Saila, 1983). This process resulted in a growing public awareness of bycatch and discarding practices, and of the resulting conservation issues (Hall et al., 2000). Since then, estimates of discards have become available for a wide diversity of regions and fisheries (Alverson et al., 1994; Kelleher, 2005; Zeller et al., 2017). These estimates show that, at the global scale, industrial large-scale fisheries (notably bottom trawlers) generated the majority of discards in the last sixty years, whereas small-scale fisheries accounted for an estimated mere 7% (combining all small-scale (hand lines, gillnets etc.) and fixed gears (weirs, traps, etc.) operating in domestic waters only; Zeller et al., 2017; http://www.seaaroundus.org). Yet, knowledge of discards from certain types of fisheries, namely those taking place in the deep-sea, remains scarce; in spite of the well-documented vulnerability of deep-sea ecosystems to anthropogenic activities (Haedrich et al., 2001; Koslow et al., 2000; Morato et al., 2006; Norse et al., 2012). The available information mainly focused on deep-sea trawling (Allain et al., 2003; Connolly and Kelly, 1996; Kelly et al., 1997, 1998). Even though hooks-and-lines fisheries are generally considered more sustainable than trawling (Alfaro-Shigueto et al., 2010; González et al., 2007; Pham et al., 2014), higher bycatch rates of vulnerable species, such as deep-water sharks, have been reported for some deep-sea longline fisheries (Clarke et al., 2005; Coelho and Erzini, 2008; Connolly and Kelly, 1996) and raise conservation concerns.
The Azores, a Portuguese oceanic archipelago along the Mid-Atlantic Ridge in the north Atlantic (Fig. 1), is a good example of this paradigm. As in most oceanic islands, fishing has always been a key driver of the Azorean economy. It is dominated by small-scale hooks-and-lines fisheries (Carvalho et al., 2011) aggregated in two main categories - pelagic and deep-sea - reflecting the considerable surrounding depths in Azorean waters (only less than 1% of the total 1 million Km2 Economic Exclusive Zone (EEZ) is shallower than 700 m). The main Azorean pelagic fisheries are the tuna pole-and-lining, the pelagic longlining primarily targeting swordfish, and the artisanal purse seining for small pelagics (Morato, 2012; Pham et al., 2013). Deep-sea fisheries concentrate on the island slopes and numerous seamounts (Morato et al., 2008) using hook-and-lines and, although multi-specific in nature, their main target is blackspot seabream, the species with the highest landed value in recent years (Morato, 2012). Deep-sea trawling has been banned in the region since 2005 (EC 1568/2005).
An efficient system for fisheries data collection has been implemented in the Azores since the 70 s, which allows accurate reporting of the landings for all fisheries. However, a previous catch reconstruction showed that the catch taken in the EEZ was 22% greater than the volume reported in local landing statistics (Pham et al., 2013). This unreporting was mainly due to i) catch landed outside Azorean harbours, mostly by national and foreign pelagic longliners, ii) catch from recreational fisheries and iii) unreported catch from the deep-sea demersal fishery. A portion of the catch, that remains unreported, is commonly utilized for other purposes, such as bait or the crew’s own consumption. This part of the catch that is neither landed nor discarded, hereafter referred to as “other uses”, can also represent a significant part of the catch and should be distinguished from discards to accurately determine how much fish is returned to the sea and assess the real impacts of discarding on the ecosystem.
Despite the focus of Pham et al. (2013) on estimating the total Illegal, Unreported Unregulated (IUU) catch, discards remained unaccounted for in most fisheries, or not distinguished within the unreported catch from “other uses”. Novel fisheries observer data has since become available, providing an opportunity for an exhaustive and detailed estimationof discarding for all Azorean fisheries and species caught. That is the aim of this study. Such assessment is timely given the increased focus on discards reinforced by the upcoming implementation of the European Landing Obligation (LO) Regulation (CE 1380/2013), which requires European fishers to land all catch of quota species (European Commission, 2013). The LO is foreseen to come into force in 2019 for Azorean deep-sea fisheries.
Section snippets
Main fisheries in the Azores
Apart from industrial whaling, bottom fishing using handlines was by far the first commercial fishery in the Archipelago. The pole-and-line tuna fishery using live bait was commercially implemented in the 1950s and developed strongly thereafter in support of the growing canning industry (Martin and Melo, 1983). The introduction of bottom longlining in the 1980s entailed significant changes in the Azores fishing industry (Menezes, 1996).
Today, the bottom fishery using both longlines and
Results
Since 1950 to present, an average 784 t (95% CI, 588–1008 t) were discarded per year by Azorean fisheries, i.e. 5.0% of their total catch. Discarding has mostly increased since the 1950s until the turn of the century, from 240 t/year in the 1950s-60 s to 450 t/year in the 70 s–80 s and peaked to 2080 t/year in the 90 s. This peak coincided with a peak in abundance and resulting catch of silver scabbardfish by the local bottom longline fishery which mostly discards this species, added to a peak
Discussion
In this study we estimate that a total 1.02 million tonnes of marine fisheries catch has been taken from the Azores EEZ during the period 1950–2014. Yet, only 5.0% of this catch was discarded, i.e. 784 t discarded per year on average. Such low discards, when compared with the generality of European and even most global fisheries, results from a combination of the particular technical-cultural and socio-economic characteristics of the Azorean fisheries, namely i) the use of highly selective
Funding
This work was supported by the European Union’s Horizon 2020 research and innovation programme [Grant Agreement DiscardLess No 633680]; the Fundação para a Ciência e Tecnologia (FCT) [strategic project UID/MAR/04292/2013 granted to MARE; researcher contract IF/01640/2015 granted to PA; and researcher contract IF/01194/2013/CP1199/CT0002 granted to TM]. The COSTA project was funded by the U.S. Fish and Wildlife Service Marine Turtle Conservation Fund [Agreement nº F15AP00577], and the MADE
Acknowledgements
To the Azores Fisheries Observer Programme (POPA), to all fishery observers, boat owners, captains and crews of fishing vessels who participated in the Azorean fisheries observer programmes and fully contributed to data availability. We would like to thank Rebecca Boys for English language editing, and three anonymous reviewers for constructive comments that helped improve the quality of the manuscript.
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