Abstract
Shark depredation is an issue of concern in some Western Australian recreational and commercial fisheries where it can have economic, social and ecological consequences. Knowledge of the shark species involved is fundamental to developing effective management strategies to mitigate the impacts of depredation. Identification of the species responsible is difficult as direct observation of depredation events is uncommon and evaluating bite marks on fish has a high degree of uncertainty. The use of trace DNA techniques has provided an alternative method for species identification. We demonstrate proof of concept for a targeted DNA barcoding approach to identify shark species using trace DNA found at bite marks on recovered remains of hooked fish. Following laboratory validation, forensic analysis of swabs collected from samples of bitten demersal fish, led to the definitive identification of shark species involved in 100% of the incidences of depredation (n = 16).
Highlights
Depredation in a fisheries context is the partial or complete removal of fish from fishing gear by non-target species
Sequences for the cytochrome oxidase subunit 1 (CO1) and cytochrome B (CytB) gene regions for the shark and teleost species commonly encountered in the West Coast and Gascoyne Coast bioregions of Western Australia were downloaded from GenBank/ Barcode of Life Database (BOLD) databases where available
Samples of shark species included in these reference archives were collected by experienced scientific staff during long-term fishery-dependent and -independent sampling programs where species identification protocols and staff training were based on identification keys reported by Last and Stevens [31]
Summary
Depredation in a fisheries context is the partial or complete removal of fish from fishing gear by non-target species. Depredation is an ecological and economic issue worldwide, occurring in commercial and recreational fisheries [9, 10]. In north-western Australia, anecdotal observations from recreational, charter and commercial fishers suggest that depredation by sharks may have increased in recent years leading to the assumption by some of a general increase in shark abundance. The case to allow increased commercial shark catches as a solution to reduce depredation has been made in Western Australia [11]. There is no direct evidence to support this assumption as these observations might reflect changes in distribution and behaviour of a variety of shark species
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