Marine mammals used as bait for improvised fish aggregating devices in marine waters of Ecuador, eastern tropical Pacific

C Castro,Jj Alava,D Cárdenas,K Van Waerebeek

doi:10.3354/esr01015

Abstract

Fish aggregating devices (FADs) are floating objects typically used to attract and capture pelagic fish in industrial tuna fisheries. This study documents 9 cases, involving 31 marine mammals, of incidentally captured, killed or otherwise retrieved cetaceans and pinnipeds which were used, or presumably used, as bait for improvised fish aggregation devices (IFAD) by artisanal fishers in coastal Ecuador. At least 3 species of small cetaceans were affected, including pantropical spotted dolphinStenella attenuata, short-finned pilot whaleGlobicephala macrorhynchus, pygmy killer whaleFeresa attenuataand an unidentified small delphinid, as well as South American sea lionsOtaria byroniawhich were reportedly killed on purpose for this fishing practice. A sperm whalePhyseter macrocephalusand a humpback whaleMegaptera novaeangliaewere presumably found floating at sea and opportunistically exploited as FADs. The South American sea lion represented 80.6% of marine mammals used as bait associated with FADs (25 sea lions out of 31 marine mammals), while the remaining 5 (possibly 6) cetacean species represented 19.4%. This is the first report of baited FADs in Ecuador, the extent of which is still unknown. This fishing technique has not been documented in other nations along the west coast of South America, although baiting of gillnets with marine mammal parts is common in Peru. Without fisheries management and regulation, this illegal fishing practice could rapidly expand and lead to further direct kills and conservation problems for targeted marine mammal populations in the eastern tropical Pacific. A bottom-up fisheries policy in concert with community-based conservation to ban the use of marine mammals as FAD bait is recommended.

Highlights

Fish aggregating devices (FADs) have traditionally been defined as structures floating at the surface of the ocean placed by fishers to increase fishing opportunities and attract and capture both pelagic juvenile and adult fishes, such as tropical tuna including skipjack Katsuwonus pelamis, yellowfin Thunnus albacares and bigeye Thunnus obe-Publisher: Inter-Research · www.int-res.comEndang Species Res 41: 289–302, 2020Fonteneau et al 2013, Gershman et al 2015, Murua et al 2016)
We found that smaller, improvised FADs (IFADs) fabricated and used by artisanal fishers (Fig. 2) were often baited with marine mammal remains
31 individuals of 6 different marine mammal species were determined as used for bait associated with a FAD

Summary

Introduction

Fish aggregating devices (FADs) have traditionally been defined as structures floating at the surface of the ocean placed by fishers to increase fishing opportunities and attract and capture both pelagic juvenile and adult fishes, such as tropical tuna including skipjack Katsuwonus pelamis, yellowfin Thunnus albacares and bigeye Thunnus obe-Publisher: Inter-Research · www.int-res.comEndang Species Res 41: 289–302, 2020Fonteneau et al 2013, Gershman et al 2015, Murua et al 2016). Other oceanic megafauna and epipelagic marine species such as sharks, sea turtles, and marine mammals aggregate around FADs (Brehmer et al 2012, Dagorn et al 2013). The potential deleterious impacts of FADs due to high levels of bycatch and threats to the marine biodiversity of tropical pelagic ecosystems have been reviewed, highlighting the need for additional fisheries management actions and an improved management plan (Dagorn et al 2013, Gershman et al 2015). Pelagic sharks, sea turtles, and other vulnerable marine species are entangled and killed in these FADs (Filmalter et al 2013, Hall & Roman 2013, Murua et al 2016). Massive mortality of silky sharks Carcharhinus falciformis was reported on an annual basis in the Indian Ocean, where approximately 480000 to 960000 silky sharks are killed each year when caught in FADs (Filmalter et al 2013)

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