Global patterns of shark and ray bycatch

Publication specs

Title: Global patterns in the bycatch of sharks and rays

Authors: Shelby Oliver, Matias Braccini, Stephen J. Newman, Euan S. Harvey  

Journal: Marine Policy

Year: 2015

The left-behind, the unwanted, the unmanaged – whatever you want to call it, bycatch is prevalent in commercial fisheries. Sharks and rays are at risk of becoming bycatch in all commercial fisheries. So what exactly is bycatch? Bycatch is the discarded (dead or alive) catch and/or unmanaged catch from fisheries. While fishing for particular species, fishers often catch unwanted species using longlines, trawls, gillnets, and purse-seines. It is common for these so-called undesired species to be illegally kept and later sold, particularly in the case of some sharks and rays, whose fins sometimes end up in the lucrative fin trade.

This study reviewed relevant data from global commercial fisheries. Most of the data came from the North Atlantic Ocean, which is not where the majority of fishing occurs. This suggests that most fisheries are not effectively reporting bycatch data. Shark bycatch mainly occurred in the South Atlantic pelagic longline fishery. No patterns were found in ray bycatch, likely due to a lack of data reporting. For both sharks and rays, the largest total annual bycatch took place in pelagic longline and deep sea/coastal trawl fisheries. One shark species dominated longline bycatch – the blue shark, pictured above – which may make up more of the catch than the actual target species. Rays are not exempt from unregulated fishing, and as a group are considered more threatened than sharks. Perhaps even more alarming is that the majority of ray bycatch comes from commercial trawl fisheries where they are often thrown back into the ocean, left for dead. 

Below is an overview of the prevailing species caught as bycatch by region:

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Sharks

  • Blue sharks – North & South Atlantic, Western Pacific
  • Silky & thresher sharks – Indian Ocean & Eastern Pacific

Rays

  • Pelagic rays – South Atlantic, Western Pacific & Indian Ocean

Sharks

  • Sharpnose sharks – North Atlantic
  • Dogfish – South Atlantic, Eastern & Western Pacific
  • Carpet sharks – Indian Ocean

Rays

  • Skates – North & South Atlantic


Sharks

  • Blacktip shark – North Atlantic
  • Sevengill sharks & shortnose spurdogs – Indian Ocean
  • Catsharks – Eastern Pacific

Rays

  • Cownose rays – North Atlantic
  • Bat rays – Indian Ocean & Eastern Pacific


Sharks

  • Coastal sharks (e.g. blacktip, bull, and dusky sharks) – North Atlantic & Eastern Pacific
  • Silky sharks – South Atlantic & Indian Ocean

Rays

  • Manta & devil rays – South Atlantic, Eastern Pacific & Indian Ocean


These results suggest that global shark and ray bycatch monitoring – data collection and availability – should become high priority for management. Sharks and rays are important fishery and tourism resources, especially in developing nations, so it is vital to find out if these levels of bycatch are sustainable for each species. Should the current levels of shark and ray bycatch in commercial fisheries not be sustainable, regulations would have to be modified or developed and enforced to safeguard their future.

Global FinPrint

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