Safe Leads for safe heads: safer line weights for pelagic longline fisheries

Abstract

In many pelagic longline fisheries around the world there is reluctance to adopt a line weighting regime that will sink fishing gear rapidly to reduce seabird bycatch. In many cases this is due to safety concerns caused by traditional leaded swivels causing serious injuries, and even fatalities, when they fly-back at the crew in the event of line breakage (e.g. from shark bite offs) during line hauling. This paper presents the results of at-sea and on-shore trials to test the safety and operational effectiveness of an alternative line weight (the Safe Lead) which is designed to slide down, or off the line, in the event of a bite-off, significantly reducing danger to the crew from line weights. At-sea trials in South Africa revealed that Safe Leads can reduce the incidence of dangerous fly-backs to very low levels. In at-sea trails, only 4.2% of Safe Lead fly-backs reached the vessel (the remainder fell in the sea) whereas 73.3% of fly-backs by leaded swivels hit the vessel and one hit a crewmen in the head. Simulated bite-off events on shore revealed the degree of slippage (influences whether leads slide but remain on the branch line, or slide off the end of the line) varied as a function of distance from Safe Lead to hook (1–4m range) and tension on the line (20–120kg range). All Safe Lead replicates placed within 2m of the hook slid off the line under all four tension treatments. Under the higher tension categories of 80kg and 120kg, 80% of Safe Leads positioned 3m from the hook position slid off the line after a simulated bite-off (cut-away). High speed photography of fly-backs showed a significant (P<0.05) reduction in the velocity on impact of Safe Leads compared to leaded swivels and an associated >80% reduction in kinetic energy on impact. Our results suggest that Safe Leads are a cost-effective and operationally simple alternative to traditional leaded swivels with significant benefits to crew safety.