Changes in the Distribution of Atlantic Bluefin Tuna (Thunnus thynnus) in the Gulf of Maine 1979-2005
Figure 4
Spatial relationship between Atlantic herring and Atlantic bluefin tuna in the Gulf of Maine.
Atlantic herring kernel density estimations were constructed based on the metric tons of herring captured in each tow or set (trawler or purse seiner, respectively). Density estimations were normalized yielding utilization distributions that displayed probability of occurrence during four two week time periods, A) June 1-15 1997, B) August 16-30 2003, C) July 16-31 2004, and August 1-15 2005. Atlantic bluefin tuna (white circles with solid black borders) were located closer to high probability regions of Atlantic herring than a randomly distributed population. While the majority of bluefin tuna schools were located within areas of high herring probability, some schools of bluefin tuna did not display any association with herring.