Ship's compliance with a traffic separation scheme and speed limit in the Gulf of Panama and implications for the risk to humpback whales

Abstract

To reduce the whale-vessel strike risk in the Gulf of Panama, the International Maritime Organization (IMO) adopted a Traffic Separation Scheme (TSS) with corresponding inshore traffic zones and seasonal (Aug–Nov) speed limits of ≤10 kn (Speed Over Ground, SOG) commencing December 2014. Here, we assessed compliance rates to these new regulations. Vessel traffic data in the area were obtained between 2014 (pre-TSS implementation) and 2016 using Automated Identification System (AIS) transponders. Most vessels (86.1 and 89.8% in 2015 and 2016, respectively) promptly adhered to the TSS. Significant differences were also detected in speed compliance rates among years, but overall speed compliance was low, i.e., only 19.0% of ships in 2015 and 9.7% in 2016 traveled at ≤10 kn. Compliance rates with the TSS and speed limits varied significantly by vessel type. These divergent compliance responses were likely due to inadequate communication to mariners and notes on printed and digital charts. Speed compliance could be enhanced, e.g. via education programs to raise awareness of endangered whales, along with collaborative initiatives between the maritime industry and port authorities, and law enforcement. In addition, continued monitoring of compliance with IMO regulations, as well as ship-related cetacean injuries/mortality by local environmental authorities should aid assessing the efficacy of these conservation measures and mitigating the whale-vessel strike risk in the Gulf of Panama. Above all though, authorities need to evaluate a mandatory speed regulation by the IMO or unilaterally, based on the newly modified and extended baseline for nation's internal waters.