TurtleWatch Research Aims to Reduce Bycatch of Loggerhead Turtles in Hawaii Longline Fishery

TurtleWatch is an online map of oceanic temperature distribution in the fishing grounds of the Hawaii-based shallow set pelagic longline fishery. Posted daily on the PIFSC website, TurtleWatch enables fishermen to avoid ocean areas where their fishing gear is most likely to interact with protected loggerhead sea turtles.

An example image of the current operational TurtleWatch product. The red-blue color scale depicts 
                 gradation in average sea surface temperature for the most current 3-day period. The grey arrows 
                 represent the direction and velocity of ocean surface currents for the latest 7-day period. The brown 
                 band across the middle represents the "TurtleWatch Zone", or the surface temperature range 
                 (63.5°-65.5°F) where fishers are advised to avoid deploying shallow-set gear.
An example image of the current operational TurtleWatch product. The red-blue color scale depicts gradation in average sea surface temperature for the most current 3-day period. The grey arrows represent the direction and velocity of ocean surface currents for the latest 7-day period. The brown band across the middle represents the "TurtleWatch Zone", or the surface temperature range (63.5°-65.5°F) where fishers are advised to avoid deploying shallow-set gear.

Developers of TurtleWatch in the PIFSC Ecosystems & Oceanography Division (EOD) have recently worked to update the tool. Evan Howell, Jeffrey Polovina and Donald Kobayashi have completed preliminary research to identify the ocean region where shallow-set gear interactions with loggerhead turtles and leatherback turtle occurred from January to April 2011. The research team is working to improve TurtleWatch by incorporating the most recent fishery information.

EOD launched the experimental TurtleWatch product in December 2006 after turtle interactions exceeded established federal limits, prompting the NOAA Fisheries Service to close the shallow-set longline fishery in March of that year. The initial TurtleWatch release included a recommendation to fishers using shallow-set gear targeting swordfish that they fish in waters with sea surface temperatures warmer than 65.5°F (~18.5°C). In December 2007, the recommendation was refined to a temperature range 63.5°F-65.5°F (~17.5°-18.5°C) . This temperature band corresponded to the region where roughly 50% of observed turtle interactions had occurred during the first quarter of the year, the time period when most interactions with loggerheads are recorded.

Sea surface temperature values and dates of loggerhead sea turtle (CC, blue) and leatherback (DC, green) 
                 sea turtle interactions during 2011, through April 15. The red band represents the 
                 "TurtleWatch Zone", or the surface temperature range (63.5°-65.5°F) where fishers are 
                 advised to avoid deploying shallow-set gear. Grey dots show sea surface temperatures and dates for 
                 observed shallow-set operations. The inset histogram shows the distribution of shallow-set fishing 
                 effort binned by intervals of sea surface temperature based on available data for the first quarter of 
                 2011.
Sea surface temperature values and dates of loggerhead sea turtle (CC, blue) and leatherback (DC, green) sea turtle interactions during 2011, through April 15. The red band represents the "TurtleWatch Zone", or the surface temperature range (63.5°-65.5°F) where fishers are advised to avoid deploying shallow-set gear. Grey dots show sea surface temperatures and dates for observed shallow-set operations. The inset histogram shows the distribution of shallow-set fishing effort binned by intervals of sea surface temperature based on available data for the first quarter of 2011.

Scientific observers accompany every shallow-set fishing trip by Hawaii longline vessels, recording sea turtle interactions, fish catch, and other information. Based on the date gear was hauled, observers recorded 15 interactions with loggerheads in 2006, 15 in 2007, 0 in 2008, 3 in 2009, and 7 in 2010. As of April 15, 2011, there have been 12 interactions with loggerheads in shallow set gear so far this year (based on preliminary data). As shown in the second graphic, 9 of these have occurred in the "TurtleWatch Zone" fishermen are advised to avoid. During the same period in 2011, there have been 5 confirmed and 1 unconfirmed interactions with leatherback sea turtles in the shallow set longline gear; 3 of the 6 leatherback interactions were in the TurtleWatch Zone.

Preliminary analysis of 2011 longline fishing records indicates that roughly 53% of the shallow-set fishing effort as of April 15 was in the 17.5-18.5°C range where 75% of the loggerhead interactions occurred.

Research is underway to compare environmental conditions between years of higher and lower loggerhead interactions to see whether differences in interaction levels are related to variations in the environment. In addition, the PIFSC team is collaborating with leatherback turtle experts at the Southwest Fisheries Science Center to see whether a tool similar to TurtleWatch can be created to help longline fishers avoid interactions with that species.