Global marine fisheries discards: A synthesis of reconstructed data

Abstract

As part of the global marine fisheries catch reconstruction project conducted by the Sea Around Us over the last decade, estimates were derived for discards in all major fisheries in the world. The reconstruction process derives conservative but non-zero time-series estimates for every fisheries component known to exist, and relies on a wide variety of data and information sources and on conservative assumptions to ensure comprehensive and complete time-series coverage. Globally, estimated discards increased from under 5 million t/year (t = 1,000 kg) in the early 1950s to a peak of 18.8 million t in 1989, and gradually declined thereafter to levels of the late 1950s of less than 10 million t/year. Thus, estimated discards represented between 10% and 20% of total reconstructed catches (reported landings + unreported landings + unreported discards) per year up to the year 2000, after which estimated discards accounted for slightly less than 10% of total annual catches. Most discards were generated by industrial (i.e. large-scale) fisheries. Discarding occurred predominantly in northern Atlantic waters in the earlier decades (1950s-1980s), after which discarding off the West Coast of Africa dominated. More recently, fleets operating in Northwest Pacific and Western Central Pacific waters generated the most discards. In most areas, discards consist essentially of marketable taxa, suggesting a combination of poor fishing practices and poor management procedures is largely responsible for the waste discarding represents. This is important in an era of increasing food security and human nutritional health concerns, especially in developing countries. K E Y W O R D Scatch estimation, catch reconstruction, ecosystem effects of fishing, fisheries impacts, overfishing, unreported catch

Conservation Concerns of Small-Scale Fisheries: By-Catch Impacts of a Shrimp and Finfish Fishery in a Sri Lankan Lagoon

“…The fishery analyzed here reported by-catch and discard levels of high concern, but it is difficult to place these findings in the context of similar fisheries as quantitative estimates from artisanal fisheries globally are virtually non-existent (Davies et al, 2009) and generally based on reconstructions (Pauly and Zeller, 2016;Zeller et al, 2017).…”

“…The same applies to the impacts of the words fishing gear, where the majority of what we know comes from studies of large-scale fisheries, where overexploitation, bycatch, and habitat destruction are commonly encountered and well-documented (Dayton et al, 1995;Hutchings, 2000;Dulvy et al, 2003;Kappel, 2005;Lotze et al, 2006;Polidoro et al, 2012;Zeller et al, 2017). Globally, at least 7.3 million tones (t) of fish (usually dead or dying) are thought to be discarded from marine fisheries annually (Kelleher, 2005;Zeller and Pauly, 2005).…”

“…Similarly, by-catch forms on average 40.4% of catch (Davies et al, 2009). Discard estimates come mostly from observations of major or large-scale industrial fisheries (Zeller et al, 2017). In comparison, limited attention has been paid to small-scale fisheries (SSF) (Fennessy and Everett, 2015;Temple et al, 2017) which are assumed to have low discard rates, for example around 3.7% total catch (Kelleher, 2005).…”

“…While there is increasing recognition of the need for improved management of these fisheries, there remains limited context-specific understanding of their socialecological complexity, particularly concerning discards and bycatch. Discards are categorized as fish and other marine life that are thrown overboard, whereas by-catch are fish and other marine organisms that are caught but not targeted (Zeller et al, 2017). However, by-catch may or may not be discarded (Zeller et al, 2017) making defining the terms difficult.…”

“…Discards are categorized as fish and other marine life that are thrown overboard, whereas by-catch are fish and other marine organisms that are caught but not targeted (Zeller et al, 2017). However, by-catch may or may not be discarded (Zeller et al, 2017) making defining the terms difficult. Given that there is increasing recognition that SSF are "too big to ignore" (Chuenpagdee, 2011;Jentoft and Chuenpagdee, 2015;Pauly and Zeller, 2016;Too-Big-to-Ignore, 2017) there exists an urgent need to characterize SSF catch in terms of non-target catch and discards.…”