Introduction & Objectives

In 2010, NOAA Fisheries’ Hawaiian Monk Seal Research Program (HMSRP) and U.S. Navy Pacific Fleet Environmental initiated a collaborative research effort to investigate potential impacts of naval activities in the Hawaii Range Complex (HRC).  To accomplish this goal, positional data was collected by 13 global position system (GPS) telemetry tags deployed over a 2 year period (2010-2011) on 11 individual Hawaiian monk seals.  For each tag deployment, the seal tracks were analyzed with respect to their location relative to tactical platforms operating in HRC during that time period.  If it was determined that the ship and the seal were within 36 km of each other, the data were queried to determine if there was any concurrent hull mounted mid-frequency sonar activity.  Independently, the tag data were analyzed by HMSRP to identify specific dates where seal behaviors differed dramatically from “normal” for each individual.  These “outlier” dates were compared to those time periods when a monk seal was in the vicinity of a hull mounted sonar ship while it was transmitting, to determine if there was any correlation between the seal’s abnormal behavior and concurrent mid-frequency active sonar activity.

Technical Approach

Positional data obtained from the Monk seal tag data (latitude, longitude and time) while it was on the surface was input into a geo-spatial data base to determine 1) if there were any tactical platform within specified range bins (described below) and 2) if there was any sonar activity during those times the animal was in the range bin.  Time periods (if any) for overlap were compared to the outlier data provided by HMSRP.  The range bins used were derived from the Hawaii Range Complex Final EIS/OEIS (DoN, 2008) table 4.1.2.4.9.7-1.  This table provides an estimate of received level from a tactical sonar operating in the Hawaii Range Complex. For each of the 13 monk seal tracks analyzed, it was determined the amount of time the monk seal was within the range bin. For those time periods the animal was in that range bin, time periods (if any) were determined for concurrent hull mounted sonar activity.   For those times when there was a sonar transmitting, the outlier data was queried to see if there were any time periods when there was any correlation between times of sonar transmissions and an identified change in behavior as defined in 6 categories: dive, haulout, surface and trip duration, trip distance and island movements.  

Progress & Results

Data summary – 2010 There were 7 monk seals tagged for a total of 805 days (19,320 hours) in 2010.  During this time period, 5 of the 7 tagged seals were within 36 km of a hull mounted sonar ship during some portion of their tagging period. There was a total of 1080 hours 45 minutes when a seal was in 15-36 km of a hull mounted sonar ship (not necessarily transmitting).  When the seal was in this range bin, there were a total of 13 hours 38 minutes hrs of concurrent mid-frequency active sonar activity. There was 192 hours 25 minutes when a seal was in the 5-15 km range bin of a sonar capable ship, with 30 minutes of concurrent sonar activity.  There was 24 hours 5 minutes when a seal was in the 2-5 km range bin of a sonar capable ship, with no concurrent sonar activity.  There was only 1 instance of a monk seal (RI11 2010) at a range of less than 2 km from tactical ship, however there was no concurrent active transmissions during that time period.  These data have been combined in table 2 with the 2-5 km range bin, indicating that there was no concurrent sonar transmission in 2010 for a seal within 5 km of a tactical platform.

Data summary - 2011 There were 6 monk seals tagged for a total of 788 days (18,912 hours) in 2011.  During this time period, 3 of the 6 tagged seals were within 36 km of a hull mounted sonar ship during some portion of their tagging period. There was a total of 155 hours 40 minutes hours when a seal was within 15-36 km of an sonar capable ship, with 15 minutes of concurrent sonar activity.  There was 20 hours 55 minutes when a seal was in the 5-15 km range bin of a sonar capable ship, with no concurrent sonar activity.  There was no time a seal was 5 km or less of a sonar capable ship.