Blue marlin are often caught as bycatch in tuna longline fisheries. The fishery bycatch and destruction of ocean sunfish are unregulated worldwide. Shrimp fisheries produce unusually high levels of bycatch. Fishing has declined due to habitat degradation, overfishing, trawling, bycatch and climate change. Dolphins are a common bycatch in fisheries. Blobfish are often caught as bycatch in bottom trawling nets. The US government has approved BRDs that reduce finfish bycatch by 30%. They are directly targeted in some fisheries and considered as bycatch in others. The term "bycatch" is used also in contexts other than fisheries. One example of bycatch is dolphins caught in tuna nets. They are known to aggregate near fishing vessels, preying on bycatch discards. Also, dolphins are sometimes killed inadvertently as a bycatch of tuna fishing. Use of the pingers has been shown to significantly reduce marine mammal bycatch. The impact of shark culling is minor compared to bycatch from Commercial fishing. The fishing market, historically has always had a porpoise bycatch.