The so-called WOCE drifters have good water-following characteristics and the slip of the drogue has been calibrated in different conditions. Over the years many people tried various approaches to solving these problems, but it was mainly due to the impetus of two large experiments, Tropical Ocean and Global atmosphere (TOGA) and World Ocean Circulation Experiment (WOCE), and with the persistent efforts of Peter Niiler and colleagues that a good surface drifter was finally developed, standardized, and deployed in large numbers. Early drogues tended to fall off fairly quickly and, since drogue sensors were not used or did not work well, no one knew how long drogues remained attached. Many problems needed to be overcome: fishbite, chafe, shockloading, biofouling, corrosion, etc. The development of satellite tracking in the 1970s quickly revealed the weakness of available drifters – most performed poorly and most did not survive long at sea. Richardson, in Encyclopedia of Ocean Sciences, 2001 WOCE Drifter The distribution of fishing vessel activity, particularly the general avoidance of the central English Channel section, suggests that the underlying ecology of the Channel is not as uniform as the broadscale habitat map would indicate and particularly, that the central section is likely to be ecologically distinct from the eastern and western sections. There is a clear distinction between the central section of the Channel (low fishing vessel activity) and the eastern and western sections, where there are concentrations of fishing vessel activity.
While this is not a completely reliable indication of fishing activity, particularly as it mostly represents larger fishing vessels, it is useful for showing where these fishing vessels spend the most time. Individual traces are plotted with low opacity, emphasising areas where tracks are concentrated. Fig. 12.3 shows a map of AIS traces for vessels identified as fishing vessels between 20 (for the first week of each month). This provides an effective satellite tracking dataset of fishing vessels as foraging predators. Most fishing vessels (all vessels over 15 m since 2014) now routinely transmit position data via AIS (Automatic Identification System).
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